Nickel-Iron Battery

This page is currently under construction and might undergo drastic changes within a short span of time.

http://en.wikipedia.org/wiki/Nickel_iron_battery

Basic Concepts Behind Construction

The electrochemistry of a Nickel iron battery is similar to a NiCd in that nickel oxyhydroxide is used as a cathode, but iron is used instead of the toxic metal complexes in NiCd. It should be possible to build it in a discharged or charged state, whichever is most convenient. Alternatively, the battery could be constructed out of metallic nickel and iron, and the nickel could be converted to NiOOH or Ni(OH)2 in situ through oxidization with ozone or peroxide and UV or some other means, and similarly the iron electrode converted. We will just go with whatever is cheap/convenient.

The reactions are not quite the way the are battery handbook, 3rd edition (more details available in that reference):

Fe + 2NiOOH + 2H₂ O <—> 2Ni(OH)₂ + Fe(OH)₂ (first plateau)

3Fe(OH)₂ + 2NiOOH <---> 2Ni(OH)₂ + Fe₃O₄ + 2H₂O (second plateau)

The overall reaction:

3Fe + 8NiOOH + 4H₂O <---> 8Ni(OH)₂ Fe₃O₄

Discharging is left to right, charging is right to left.

"Plateau" refers to a region on the voltage vs state of charge of the iron electrode.

In practical batteries the second plateau is not normally used for various reasons even though avoiding it entails adding a lot of extra iron.

First test

A sample concrete cell was tested, but no practical benefit is achieved using concrete as an electrolyte, as to be effective, the entire cell must be submerged, and the electrical conductivity of cement is far too high when submerged. A new design is in the works for a cell which would use raw glycerine (glycerol) as a byproduct of biodiesel production, thus improving the ecologies of both systems. The rationale is that the lye (KOH or NaOH) which 'contaminates' the glycerine should prove to be an effective electrolyte, and the glycerine itself should support a more stable cell. (Glycerine will evaporate much more slowly than water, and due to higher viscosity, should even further improve vibration-resistance of the cell. Ideally, this design could even be adapted to portable units.

Preliminary Figures for a 12V, 1kWh pile

NiFe cells produce a working potential of 1.2V, and charge at 1.4V. A 12V battery would then consist of 10 cells, and charge at 14V which is typical for most "12V" batteries.

To achieve 1kWh capacity, we will need 1000W/12V = ~85Ah. This means that each cell will need to provide 85Ah capacity. This corresponds to 1 coloumbs per second*3600 seconds per hour*85Ah*1/10^5 coloumbs per mole, which is approximately 3.17 moles of electrons. Iron is cheap and so is not a limiting factor. Nickel's electrochemistry in an NiFe battery indicates we get an electron per nickel atom, so 3.17 moles of nickel will be required with a hypothetical 100% utilization of active material. This is about 185g of Ni at a molar mass of 58.69g/mole. For a 'safety' margin, we will round up to 200g. At 200g Ni per cell, a total of 2kg of nickel will be needed for a 1kWh unit. The actual capacity of this cell based on the rounded values above would be 1095.8Wh.

Environmental Aspects

All batteries (at least the ones in common use) are toxic to a greater or lesser extent. The NiFe Battery isn't an exception, but it is far less toxic than Cadmium-based batteries.

• Iron is non-toxic and commonly available.
• Nickel is slightly toxic.
• The electrolyte is caustic, but a so-called starved electrolyte cell can be used in a sealed battery without degradation in performance if potential spills are a perceived problem. In this design only the minimum amount of electrolyte is used, and it is absorbed in a porous mat so there is no liquid that can escape. This is what an Absorbed Glass Mat (AGM) lead acid battery is, and it can be used here too. The cost of the mat is not insignificant though. For photovoltaic there may be no need, flooded cells could be fine.
• Increasing the viscosity of the electrolyte with glycerin also could be used, similar in theory to a gel-cell battery. There is a cost of increased internal resistance for a higher viscosity electrolyte. It may also pose a problem with the amount of gas produced, which needs to escape from the region of the electrodes. The glycerin might reduce cycle life as it could degrade on one of the electrodes in the strong red/ox environment or contain contaminants.
• Glycerin is a by-product of creating bio-diesel, thus using a waste of a different process. It may have other uses elsewhere in producing the active materials etc. too.

Sources and pricing

FusionBeads [1] 3"x3" 24 gauge nickel sheet is $3.25.
Metric: 76.2x76.2mm and 0.5mm thick. The density of nickel is 8.902 g/cm3. 2903.22 mm3 which is 2.90 cm3. Thus, each sheet weights 25.84g. 2000g (2kg required as above) is 77.38 sheets. $251.50 is the cost of 2kg of nickel. Actually, it can be gotten cheaper in these quantities, but this is an outside number.

We need to look into purchasing in bulk as it is far cheaper than this sheet. Those guys must be making generous profit to say the least.

Wikipedia indicates that the price of metallic nickel these days is about 13 USD a kilogram, but it has been in the fifties during certain price spikes, I could not find a historical record, or even the current commodity price anywhere.

There are several ways to make the nickel electrode and active material which require different raw materials. See electrode sections for details. To both produce the nickel oxyhydroxide or hydroxide either inside the electrode matrix or as a powder of good particle size and porosity, which is then mixed into a paste and pasted into (with a matrix electrode) or onto (with a metal plate electrode, needs other additives to the paste) the electrode, there are several established economical ways that involve different raw materials, all of which will have different prices and availabilities:

-Use a metallic nickel which is then oxidized electrochemically in a suitable chemical bath - Use the oxyhydroxide or hydroxide powder, which can be purchased directly in purities adequate for battery use - Nickel oxide (NiO2 I think), which is then roasted in air to oxidize it to the oxyhydroxide - Nickel nitrate, sulfate, and potentially other salts can be melted, the electrode dipped in, and then the electrode dipped in hot sodium hydroxide solution to convert the nickel through a binary reaction to nickel hydroxide. This has to be repeated several times to load the electrode. - To produce nickel hydroxide powder from some other salts, the nickel salt is sprayed into a basin of sodium hydroxide.

As long as we have nickel compound of adequate purity it's just a matter of figuring out an economical production method, or using an existing one. Which material will be needed can be chosen on price, availability and the ease and economy of the associated manufacturing technique.

Nickel could be recovered from the waste stream too, but this might not end up saving any money.

Iron as an element or in the form of steel is cheap, but a look on alibaba.com indicates that it may cost substantially more in pure iron powder. We might want to make our own in the production phase, especially if a design which only uses a fraction of the iron as active material is chosen. The first problem is purification, in which the carbonyl process or other industrial processes might be useful in scaled down form, but this is where the contributions of a chemist would be particularly welcome as there is probably something which is more practical. Then it needs to be powdered either mechanically or through chemical or electrochemical processes, or some combination thereof.

Purification may not be badly needed. It would improve performance but how much so needs to be worked out so an informed decision can be made.

The Edison process for producing the iron powder was much like what references indicate is the current process used for producing the powder for pocket plate batteries [the battery handbook, 3rd edition]:

- dissolve "pure iron" (how pure, what impurities are problematic can be nailed down to a fair degree from the documents listed in the sticking points section). - The FeSO4 is then re-crystallized (are we talking fractional crystallization here to purify it?), dried, and roasted (815 to 915 deg. C) (in what atmosphere? Air probably) to Fe2O3.

- The material is washed free of any remaining [iron] sulfate, dried, and partially reduced in hydrogen.

-The resulting material (Fe3O4 and Fe) is partially oxidized, dried, ground, and blended. Small amounts of additives, are blended in to increase battery life, depassivate the iron electrode, reduce gas production, and improving conductivity. (See other reaction and additives sections for details on potential additives.)

There are other ways established ways:

Heating iron oxalate in a vacuum produces a mix of iron and iron oxide powder High purity iron powder like carbonyl powder

Price of Nickel and Iron

http://www.indexmundi.com/commodities/?commodity=nickel price is very roughly $23 per kg. Pretty good really. http://www.steelonthenet.com/commodity_prices.html price $0.60 per kg for scrap steel, presumably pure iron would be in that range.

From the electrochemistry figures above for a 1 kWh unit, that would be $48 or so on metals. So 20 Wh per $ ($0.05 per Wh). Even the cheapest lead acid batteries are 7 Wh per $. In reality they are more like 5. So the good news it that materials cost should not sink the ship anyway, although I'm sure all the other costs for the perforated pocket, assembly etc. will add up plenty fast.

Toxicity

Nickel itself that is the concern rather than any particular compound. Water soluble compounds are unsurprisingly much more of a concern than metal that is bound in solid objects like nickel plating or some types of stainless steel, since it is more bioavailable and can be spread and spilled more easily. At low levels of exposure talking in terms of nickel content is done. But of course the exact solubility and other factors has a substantial effect on the exact toxicity at higher levels of different water soluble compounds too, note the ld50 is 10x lower for nickel chloride as for nickel oxyhydroxide according to the documents below, so the expedient of speaking in terms of nickel content doesn't always work that well.

Note that nickel hydroxide, oxide and oxyhydroxide are all considered "insoluble" although obviously the chemistry here depends on them being at least a bit soluble. But that increases the safety margin a bit. It may be substantially higher under these alkali conditions though.

Still all metals are toxic to some degree including iron and we need some numbers to make an informed decision. Preferably a solid evaluation of dose response relationship, and if the batteries are to be widely adopted now is the time to factor in chronic exposure too. It needs to be considered not in a vacuum but relative to other options available.

higher quality : http://jas.fass.org/cgi/content/abstract/28/5/620 http://www.annclinlabsci.org/cgi/content/abstract/11/2/119 http://www.hpa.org.uk/web/HPAwebFile/HPAweb_C/1236757324101 l http://www.epa.gov/iris/subst/0271.htm https://fscimage.fishersci.com/msds/53189.htm http://www.nickelinstitute.org/index.cfm/ci_id/13029/la_id/safe_use_guide_5.cfm.htm

unknown due to lack of access: http://www.ncbi.nlm.nih.gov/pubmed/19888907 http://www.annclinlabsci.org/cgi/content/abstract/7/5/377 Low quality: http://www.crios.be/Nickel/toxicology.htm material safety datasheets with information regarding nickel oxyhydroxide, clearly it is sometimes used as a material in NiMH, in fact most of the hits are datasheets for such batteries rather than the material itself: http://www.rdbatteries.net/Data/Panasonic_NiMH_Info.pdf http://www.chiefsupply.com/resources/msds/Moto-NiCd.pdf http://www.batteriesplus.com/msds/Duracell_Nickel_Oxyhydroxide_%20Batteries_NorthAmericaMSDS.pdf (as if companies would give accurate information on their own products) http://www.it.pg.com/productsafety/msds/fabric_and_homecare/duracell/Duracell_Nickel_Oxyhydroxide_Batteries_(North_America_MSDS).pdf

Note that the permissible exposure limits (PEL) for the material is about a fifth that of graphite, which we know is not too toxic though it might accumulate in the lungs I guess. Still there are a lot of variables there as most particles inhaled are not retained, depends on size etc etc.

Obviously the LD50 is quite low at 1000 mg/kg range. But that means little in terms of what happens at lower levels. For Chloride it seems to be in the 100 mg/kg range.

http://www.osha.gov/SLTC/healthguidelines/nickelsolublecompounds/recognition.html They fail to say dosages in critical places, this information is actually low quality.

nickel chloride: http://www.sciencelab.com/xMSDS-Nickel_chloride-9926213

oxide:http://www.inchem.org/documents/ukpids/ukpids/ukpid70.htm

From Dietary information perspective: http://iom.edu/Activities/Nutrition/SummaryDRIs/~/media/Files/Activity%20Files/Nutrition/DRIs/ULs%20for%20Vitamins%20and%20Elements.pdf

"A Tolerable Upper Intake Level (UL) is the highest level of daily nutrient intake that is likely to pose no risk of adverse health effects to almost all individuals in the general population. Unless otherwise specified, the UL represents total intake from food, water, and supplements."

1 milligram per day for nickel, 40 for iron. Well that's to totally zero adverse effect level and there's probably plenty of room for more there. Nickel is probably available as a dietary supplement, I wonder what happens when people take too much.

http://www.eoearth.org/article/Public_Health_Statement_for_Nickel case report little more than half way down of people drinking 250 mg/liter (250 ppm) nickel welding, relevant to pocket production: http://www.crios.be/Welding/toxicology.htm Maybe it woudl be better to make the pockets without welding. Folding perforated sheets cleverly, sewing with nickel wire etc. plenty of other options that should be fine .

As usual it is difficult to obtain quality information on a health issue and it is very time consuming to wade through the crap and get some answers. Case reports, vague qualitative statements, contradictions, and paywalls, are the norm. Ideally a table of dose-response relationships for a range of different people over a wide range of doses would be obtained but whatever.

In summary it looks like it is certainly less problematic than lead or mercury, gloves, ladling or scooping rather than pouring dry materials, and working outside would more than suffice for me personally. Spills of solutions and especially powders should be prevented.

Suggested contributions

We could use the documents below.

Then these can be legally shared by e.g. zippyshare.com with other developers who ask for a copy under the fair use doctrine. See the library section for what we already have.

We basically want all papers that mention nickel iron specifically and most of the others that relate to battery electrodes made from nickel oxyhydroxide(very frequently referred to as only "hydroxide" in the context of NiMH especially), and metallic iron and/or iron oxides. The electrode ones may not mention "nickel iron" per se because e.g. a good iron electrode can also be used in several other battery chemistries.

Most important:

6V, 60Ah nickel-iron battery. (http://md1.csa.com/partners/viewrecord.php?requester=gs&collection=TRD&recid=2274533EA) Periasamy, P | Ramesh Babu, B | Jegannathan, S | Muralidharan, S | Chakkravarthy, C | Vasu, K I Bulletin of Electrochemistry. Vol. 6, no. 2, pp. 263-265. 1990

Nickel--Iron Battery Development in CECRI. (Abstract Only) ,Periasamy, P | Babu, B R | Jegannathan, S Trans. SAEST. Vol. 24, no. 3, pp. 6.19. July-Sept. 1989

Alkaline Ni--Fe battery development is undertaken in CECRI under the sponsorship of the Defence Ministry (India). Dry powder sintering technique using the concerned metal powder is followed to fabricate porous Fe negatives and Ni positives. With carbonyl-nickel powder as the starting material, porous Ni positive plates (17.4 x 13.8 x 0.2 cm) were prepared by sintering in hydrogen atmosphere to get the Ni matrix of porosity 8-85%, followed by impregnation of nickel hydroxide into the pores of the Ni matrix. Porous Fe electrode was fabricated from electrolytic Fe powder by sintering in H atmosphere and activation of the sintered porous Fe plate (17.4 x 13.8 x 0.15 cm). A 6 V, 60 A/h Ni/Fe battery consisting of five individual cells in series is assembled with five positives and six negatives in each cell. The electrolyte is 30% KOH solution containing 50 g/l of LiOH. The separator is woven nylon fabric. The 6 V, 60 A/h Ni/Fe battery is charged at the 2 h (C/2) rate and discharged at different rates ranging from 1 h (C) to 5 h (C/5) rate to realise the A/h capacity in each case. In addition to carrying out life cycle test on the battery, self-discharge and effect of temperature on the output have been carried out. Special features of the Ni/Fe battery developed in CECRI are: high charging efficiency (80%), approx 50% capacity output at 0 deg C, high rate of charge and discharge and deep discharge up to 90-95%, without affecting the battery.--AA

Less important but still highly desirable:

Westinghouse nickel-iron battery performance, 1981 Yeki Creator/Author Rosey, R. Publication Date 1981 Jan 01 OSTI Identifier OSTI ID: 6394222; Legacy ID: DE83008901 Report Number(s) CONF-811010-9 DOE Contract Number W-31-109-ENG-38 Other Number(s) Other: ON: DE83008901 Resource Type Conference/Event Specific Type Technical Report Resource Relation 6. electric vehicle council symposium, Baltimore, MD, USA, 21 Oct 1981; Other Information: Portions are illegible in microfiche products Research Org Westinghouse Electric Corp., Pittsburgh, PA (USA). Advanced Energy Systems Div. Subject 33 ADVANCED PROPULSION SYSTEMS; 25 ENERGY STORAGE; ELECTRIC-POWERED VEHICLES; IRON-NICKEL BATTERIES; LIFE-CYCLE COST; PERFORMANCE; CAPACITY; DESIGN; ELECTRODES; ENERGY DENSITY; COST; ELECTRIC BATTERIES; ELECTROCHEMICAL CELLS; METAL-METAL OXIDE BATTERIES; VEHICLES Description/Abstract An advanced nickel-iron battery system is currently being developed by Westinghouse for energy storage applications which include on and off road electric vehicles, emergency standby power systems and deep water submersibles. The thrust of a present development program, sponsored by the Department of Energy under the Electric/Hybrid Vehicle Act, is to demonstrate battery system performance characteristics in an electric vehicle to achieve a 100 mile range on the SAE J227a D cycle. The 1981 nickel-iron battery performance objectives established by Westinghouse required to meet this range are: 54 wh/kg gravimetric energy density; 120 wh/l volumetric energy density; and 150 w/kg peak power density. Additional requirements are > 60% charge efficiency, selling price of $80/kWh, and 1000 cycles life to provide a system with acceptable operating life cycle cost. Demonstrated results for electrodes, cells, and batteries will be presented. These include charge/discharge voltage profiles, thermal effects on performance, power characteristics, cyclic stability, and vehicular mission profiles. The design and operating features of the battery system will also be reviewed.

There are some even less important ones on the research page.

See the Library section for a list of documents that we already have (these lists of what we need and what we have share no documents in common at this point on june 30 2011.)

Future Prototypes

It looks as though using a high surface area electrode made from nickel or another conductive material which is acceptable from a chemistry standpoint, then causing the oxyhydroxide to deposit on it electrochemically could be done. But there are a great many ways to make the electrodes, and some may be more suitable. A great number of patents are available with what look like better options. See the research page for links.

All of them include some "plaque" or conductive matrix with fairly high surface area which extends throughout the active material. Nickel sponge, sintered nickel powder, and nickel fabric cloth like material, have been used.

A typical fibrous mesh for a battery that performs well at 0.2 C might use fibers 15 microns in width, usually not circular but their cross section might be 15 x 30 microns, which fill 20-10% of the volume of the electrode, which entails a void width of 60 microns ( (1000*(1-f)/((f*1000)/w) where f is the fill fraction, and w is the average width of the average fiber). Fibers as small as 2 microns have been used and they provide superior performance that might be good for a starting battery.

Other documents indicate that around 10-100 micron fibers with voids 100 to 200 microns apart in which the conductive material consumes 10 to 30 percent of the volume of the electrode is reasonable, so that's about the right range, the documents are talking about different contexts and from different eras so it's no surprise there is that variation.

A polymer binder loaded with graphite or other carbon particles which is then carbonized (not the same as pyrolized, entails changes in crystal structure and interconnection of the carbon mass which increases strength and conductivity) can be made, with the carbonized polymer being the conductive grid. Polymer binders (not carbonized) filled with conductive particles and hydrophobic plastic (e.g. teflon) spacer particles are often used in modern batteries. The mix is made, then pressed with great force onto a nickle or nickel plated grid or cloth. The polymer mix material can also be applied to a thin textured sheet of metal.

Fine flakes ("flitts") or fibers of nickel metal can be mixed with active material, pressed into a plate, and heated to melt or diffusion bond the flakes/fibers together, producing a conductive matrix surrounded and filled by a porous mass of oxyhydroxide.

Nickel wool or other low density fibrous masses of conductive material which are chemically acceptable might do as well. It is stated in patents that nickel plated steel wool works well. In this case the active material has to be applied in a paste or though more complex means like electrodeposition, in which the active material is precipitated by electrolysis in the electrode volume.

The so called pocket electrode is still used in modern batteries; conductive powder or fibers or flakes (graphite, nickel or nickel cobalt alloy flitts) a couple millimeters in size are mixed with the active material and pressed into "pockets" formed from perforated metal sheets. The pressing is needed to get good electrical contact between the particles and conductive material.

For the iron electrode high surface area solid iron electrode may be used with small amounts of something to activate it, such as sulfide ions like magnesium sulfide, iron sulfide or even elemental sulfur, to cause activation of the electrode (removal of the iron monoxide layer as the sulfur is more electronegative than the iron and for some reason suppresses hydrogen gas production). Other additives in the iron electrode might be possible and desirable but sulfur is the main one (see additives section) and accomplishes several things at once. For high purity powder like carbonyl iron the sulfide needs to be added. Otherwise it can be present in high enough amounts for some batteries as an impurity (see other reactions section). The appropriate surface area of both electrodes which will give a reasonably low internal resistance needs to be calculated or tested. References indicate it should be on the order of 10 sq meters per gram, which is about 26 micron average particle diameter (density of NiOOH is 4 so 40 square meters or 400,000 sq cm per cc, so pi*r^2*4/(4*pi*r^3/3)=1/(r/3)=400,000 so r=1/133,333 cm or 13.3 microns, so diameter is 26.6 microns. This same reference source, the battery handbook 3rd edition, says that 200 mesh (0.075 or 75 micron diameter) particles are used for pocket plate technology so there is some disconnect there.

Loose powder is not ever used, because the conductivity of the mass is too low. In the the case of the nickel electrode, they must be at least pressed together with the flits (pocket type) or surrounded with a fine conductive matrix and have quite small size area and then during the initial charge/discharge cycles they tend to bond together so the bulk conductivity of the mass increases to an acceptable level (pasted). Nickel hydroxide is even less conductive than the oxyhydroxide (how much?). This may help to explain why the electrodes are rarely loaded with the hydroxide initially, as the lower conductivity combined with the poor level of inter-particle contact before the particles are bonded together would make the initial charge/discharge cycles take that much longer but that's not a major problem for us.

In at least one of the Edison batteries he chose to use mercury to increase the conductivity between iron particles but that is not used in modern batteries and there are better ways to get the improved performance. It does not seem to have been done with the batteries that were eventually mass produced by the edison battery company either. Commercial batteries like the Changhong batteries intended for solar use are rated for 0.2 C but they make batteries capable of starting locomotives too. The C ratings are only guidelines however and can be exceeded greatly at cost of efficiency and effective battery capacity - 6 C produces a capacity of 65% rated capacity for the battery in the sealed battery testing doc. See related pages section for more about high rate batteries.

Over time the electrode shape could change in undesirable ways, reducing surface area and increasing the battery's internal resistance to an excessive value. It appears that this occurs to a relatively small degree in nickel iron batteries, and in fact this is mainly what gives them their much longer life compared with other batteries. Mostly it is limited by the very low solubility of the reactants and reaction products, they cannot travel far in the electrolyte before being redeposited (precipitating out of solution). In fact the nickel electrode reactions are thought to occur almost all in the solid state.

This is one of the reasons deep discharging of lead acid is a problem. Although there are many different types of lead acid battery there is usually alloy of antimony and lead used to form the electrode scaffold for one or both electrodes, which reacts more slowly than the lead that is supposed to cover it. But if discharged too deeply the scaffold will react too, and it cannot be reformed in the shape it was, rendering the battery damaged. Similarly during recharge some battery types form dendrites from one electrode to another - thin shafts of metal. As the finger of metal protrudes towards the opposing electrode the resistance between the tip of the finger and the opposing electrode gets lower, resulting in a higher current at the tip of the dendrite, causing metal to be preferentially deposited at the tip of it, lengthening it until it touches the opposite electrode, shorting the battery. Clearly over many charge/discharge cycles the cumulative effects that result from the relative effect size of these processes can cause substantial changes in electrode shape if they are not understood and accounted for, which is hard to do.

In the nickel iron battery the fact that this occurs very little allows the iron electrode metal scaffold (plaque, current collector) to be made of the reactant itself while still getting long life (sintered electrode). The surface can get converted to the reaction product and back again many times without changing the shape of the internal iron structure. Usually, if you did this with e.g. a zinc anode the zinc would get out of shape pretty fast due to dendrite growth etc. and become useless. A sintered block with 3 to 4 times the amount of iron than stoichiometric is typical, so 1/3 to 1/4 of the iron is used in each full charge/discharge.

In patents it appears to be universally assumed that for both nife electrodes, if they have a high surface area at manufacture they continue to have a high surface area thereafter so this may not be a problem.

Other important reactions in the cell

If you want a good battery rather than a poor one, the side reactions and other reactions in the cell are the most critical factor, with the only second being electrode geometry/design. They are a fundamental part of battery design. These exclude the reactions that contribute to the output electrical energy to the cell.

These are what sap energy away, leading to poor efficiency and high self discharge, and partly what limits battery life. Some of them are used to counteract the undesirable ones.

There are others that need to be learned from the documents listed in the sticking points section.

- tellurium dioxide is a recommended additive but never seems to be used in commercial batteries, improves efficiency by reducing hydrogen evolution.

- mucic acid is another additive that can be used to reduce the hydrogen evolution when integrated into the iron electrode, by a factor of 10 during storage (reducing self discharge greatly). Not clear if it helps improve efficiency as the patent does not mention that, but hydrogen evolution is the main reason the energy efficiency is so low so maybe worth further investigation.

-self discharge due to oxidization by dissolved o2 (pretty small in magnitude)

-The iron being anaerobically attacked by water, about 1000 times larger in magnitude than the oxidation due to dissolved o2. This is the main reason the battery has such a high self discharge rate. Basically the conversion of iron plus water to iron hydroxide plus hydrogen gas.

- self discharge at the nickel electrode, need to check the mechanisms/reactions again probably relatively low since it is in nimh and nicad despite the same reactants present.

-corrosion of the metallic mesh by electrolyte, this may be one of the lifetime-limiting reactions that increases with temperature.

-oxidization of sulfide to sulfate and it's ensuing accumulation on the surface of the iron electrode, increasing internal resistance. Sulfide is also often used to keep the iron electrode active so when it is used up the battery dies.

-sulfides like iron sulfide, or in some cases elemental sulfur (S8), or compounds of selenium or tellurium is used to "depassivate" the electrode. According to patents and reference sources this consists of reducing non-conductive, non-active oxides like FeO on the surface of the electrode back to active forms. They also indicate that without these additives charge efficiency drops greatly and hydrogen evolution goes way up, unless high purity iron like carbonyl iron is used and even then they don't work for long unless sulfur is added. No information has yet been found as of june 3rd 2011 on the performance of selenium and tellurium as mentioned above, if it might be superior to sulfur. Probably not.

-Accumulation of sulfur on the surface of the iron electrode esp. at lower temperatures and high discharge rates. If the sulfur or sulfides (or maybe other additives) are incorporated into the structure of the iron mass they are released faster when higher discharge rates occur and this can end up being too fast for them to diffuse away, resulting in them accumulating as a solid on the surface of the electrode, and since they are insulating and block access to the electrolyte this is a problem. At lower temps the solubility is lower so they are more prone to precipitate out of solution. This is not a permanent effect, the compounds redissolve if given some time. The exact temperatures and discharge rates depend on the quantities of additive involved and the surface are of the electrode etc. but references indicate this a problem more in the 0 deg C range than room temperature and at relatively high discharge rates, like two or three times the rated discharge rate (how high? In milliamps per sq meter is probably a reasonable measure).

-deposition of iron in the nickel compound crystal structure <--needs more research could be important life limiting reaction.

-oxidization of the surface of metallic flitts to low conductivity nickel oxide. Edison had a problem with nonconductive layer on the flitts forming and didn't know what it was, maybe explained in later patents.

-carbonate and the other one in the battery handbook undesirable ions, note that carbon dioxide from the air will react from the electrolyte to form carbonate salts <-- need to add those other ones. Some docs on the desired list may help inform here.

-probably all kinds of minor undesirable contaminants, Edison mentions manganese, and high purity material like carbonyl iron is often used to avoid them, and similarly for nickel electrode. However this may be expensive or harder to produce.

-lithium hydroxide apparently improves the thermodynamic reversibility of reactions (improves overall energy efficiency) and slows down the iron poisoning of the nickel electrode maybe this indicates longer life and higher charge/discharge efficiency, we need a chemist who can identify other ways of improving esp the charge/discharge efficiency by identifying other acceptable additives that might work. Also maybe analyze modern batteries if they have high performance.

-evolution of gasses at the nickel electrodes during charging and also charge-stand, this could play into the low efficiency but may only be commensurate with other prerequisite reactions at the iron electrode and unpreventable in themselves.

-The air interface one that causes oxidization of the nickel metal and/or active material(?) of the electrode when there is an interface with the electrolyte and air, nickel electrode needs to be submerged. Another cause of self discharge if not designed right, plus can corrode the electrode or the nickel plating of it right through possibly leading to failure.

- a couple of abstracts of inaccessible documents seem to clearly indicate that accumulation of potassium/sodium carbonate and similar compounds (presumably produced by atmospheric co2 and impurities in makeup electrolyte) deposit on the electrodes and this is one of the first problems that limits cell lifetime for unsealed, conventional nife batteries. They may be rejuvenated if this is the case.

Need to add references. See additives section too.

Additives

- cobalt hydroxide is used to improve conductivity of the nickel electrode either by adding it to the nickel oxyhydroxide at manufacture or into the powder after, by e.g. coating the particle electrolytically to give them a higher effective conductivity without interfering with their reactivity too much (it does reduce it a little though so again there will be an optimum amount). It can also help to increase the fraction of active material that is utilized. 1 to 5% of the active material mass may be used for this. We probably want to avoid bothering with this.

- metallic cobalt to the metallic mesh, function needs to be checked, probably to improve contact resistance and reduce oxidization of the mesh and maybe reduce corrosion rate by electrolyte.

-sulfur, tellurium or selenium compounds are used to activate the electrode, see other reactions section

-carbon black is sometimes added to pocket plate electrodes to improve bulk conductivity of the active material mass

-graphite particles can also be similarly added for pocket plate electrodes

Non-chemical factors affecting performance

At low temperatures with some iron electrode designs sulfur can accumulate on the iron electrode and increase internal resistance (designs which incorporate elemental sulfur, patents indicate this can be rectified by using a sulfide salt of low solubility like iron sulfide FeS).

The conductivity of the electrolyte goes up as the temp goes up. This is desirable but other undesirable reactions increase in rate at higher temps so there is a compromise there. Also this is one of the main mechanisms that can lead to thermal runaway during constant voltage charging as it can form a positive feedback loop. The solution is to just not use constant voltage charging, which is easy.

The factors like the energy to weight ratio and power to weight will of course tend to be affected by any non-reactant materials used to e.g. reduce cost etc, but fortunately those are of little importance in the context of OSE. Basically we want to produce something that can replace lead acid which is cheaper, easier to work with and make and maintain, more durable with abuse and longer lasting, and not as bad for the environment. Ideally both for starting lighting ignition (SLI) batteries and also storage. Batteries described in documents can handle 6C and more without seriously hard to manufacture materials and additives so SLI is definitely an option. None of these require high energy density or power to weight ratio although they are always nice.

The fraction of active material that actually is utilized if low will reduce power and energy to weight and volume ratio. Can be affected by particle size, additives and also any particles of active material that are not in reasonable electrical contact with the current collector for whatever reason will remain unused.

The level of the electrolyte can if not maintained in a non-sealed battery, drop below the level of the plates, and the uncovered portion of the plate may remain unused, decreasing capacity until the electrolyte is replenished.

There is always some distance that the current needs to travel to get from the reaction area to the current collector, and to do this is has to pass along the active material. Therefore the conductivity of the active material is an issue which significantly affects internal ohmic resistance (the term internal resistance is often used to refer in a catch all way to the current draw vs. voltage output relationship even though this is due to many factors besides ohmic resistance).

factors affecting cost

1. Active material utilization fraction.

Not all of the active material actually gets used in the electrode. Obviously we want it to be high in the nickel electrode in particular because the cost of the material is high.

In the Edison cell the fraction of mass utilized can be calculated from the weights and composition of the electrodes Edison gives in the patents and this should be done. It can be increased with the addition of conductive carbon (like graphite) particles to the active material. Documents indicate that the homogeneity of the particle sizes is important in pocket cells to increase mass utilization, which should be no surprise as it would entail a smaller number of particles in between the gaps of large particles that are not compressed in any way against their neighbors, leading to high contact resistance and therefore low electrical coupling to the current collector.

For pasted electrodes it can be very high for both the iron and the nickel electrodes, patents indicate that it could be 80% without cobalt additive and almost 100% with it for the nickel. Smaller particle sizes and finer denser mesh helps too. Similar figures apply to the iron but since iron is cheap that will probably not be a deciding factor in the iron electrode design.

For sintered iron electrodes it is typically 1/3 or 1/4 of the total mass. The rest forms the conductive matrix of the current collector.

If the active material or a precursor that is later converted the the active material (like nickel oxide, probably NiO) is added before sintering the current collector that would need to be checked, but it would likely be high.

With electrodeposition and molten salt it should be very high.

For the nickel electrode the amount of conductive metallic material used (if metal is used, carbon works too) is typically 30% to 10 by volume of the electrode, so this will have a significant impact on cost if it is solid nickel. This may be a good reason to use a nickel plated steel of some sort or some other material as a current collector.

From patent number 00880978 Edison indicates that about 8 grams of the material the composition of which is described in number 839,371 is used per tube. The composition could be checked and the other patents searched (see research page for and archive of searchable pdfs of edison's patents) to find what the ampere hour capacity of each tube was, which I remember seeing but now forget, and then the efficiency of material utilization can be calculated. It is probably fairly low but can be improved by mixing in conductive particles of carbon and using a more uniform particle size. Mostly likely a pocket plate battery would be relatively expensive when made at a small scale, for these and other reasons.

The homogeneity of the materials is important apparently according to one of the journal articles and may be cheaper than additives.

2.Charge/discharge (round trip) efficiency (distinct from charge only efficiency).

This has a major impact on the cost of a solar power system that the batteries are included in. See [Impact of battery efficiency on cost]. To a rough approximation it can be represented as an addition to the $/Wh cost of the battery, and could add an additional $0.2 per Wh or more, which given that $0.2 per Wh is about the cost of lead acid AGM batteries (the normal type used in solar installations) that is a real problem.

However lead acid batteries are not that much better, actually, in real-world conditions. Nevertheless, the efficiency is one of the major considerations that should be optimized for. References indicate this can range from 50 to 65% depending on battery design, so it is not a given. Methods of enhancement so far identified include the addition of activators to the iron electrode like sulfur, selenium or tellurium compounds (which is best? Sulfur is the only one references seem to describe being used so experimentation or in depth knowledge of chemistry may be required here).

Forum posts and other information indicates that the efficiency actually rises over time to 80% or so after a few years of use, but this needs to be verified with other sources. Ideally the mechanisms could be identified and used to get this performance right off the bat.

This seems like one of the things an individual highly knowledgeable about chemistry could be particularly helpful with.

As the cost of the collector goes down over time this will become less important.

3. Cycle life. Although they get much longer cycle life than lead acid batteries, and it is to some degree inherent to the chemistry, it is not a given, and references indicate it can vary from 1500 to 3500 cycles, depending on the design of the battery, and up to 4000 with "good care" (issues which cause cycle life loss due to lack of good maintenance should be identified but this refers to non-sealed batteries so some of them might not apply to a sealed battery).

Cycle life unsurprisingly has a major impact on long term cost, so it should be maximized. It would be hard to test due to the time requirements, so this is a case where the higher quality references and perhaps in-depth knowledge of chemistry will be particularly needed.

Financial calculations should be done to determine how valuable very long lives are, although this is also important as part of OSE specs.

4. Calendar life.

Marketing material[www.nickel-iron-batteries.com] indicates that there are significant mechanisms that causes capacity loss independent of charge/discharge cycling. Some ideas on what it/they might be are included in the other reactions section.

In Edison cells one of the problems was the make-up electrolyte had impurities in it, and dust from the air would get into the battery and cover the electrode material particles. A sealed battery would of course avoid this, so there is another reason to do a sealed battery.

Problems with an unsealed cell

Ingress of stuff: Dust, carbon dioxide in the air which reacts with the electrolyte to form carbonate salts using up the electrolyte and possible being a problem chemically (need access to better references to know) Contaminants from the replacement electrolytes added, but from the solutes and that less than perfectly pure water is used. To some extent these will be expelled along with the electrolyte. May include some particulate matter.

Need to calculate how much of a problem these things would be without any sort of precautions, e.g. just a hole in the case.

Egress of stuff: Electrolyte solute, a mist is produced when bubbles break the surface of the water and this can result in loss of electrolyte solute as the water droplets that escape contain it.

Electrolyte solvent, due to the escape of mist and the conversion of the water to gas.

fortunately the active materials stay put, since they are hardly soluble in the electrolyte.

Prevention methods assuming lack of gas recombination ability: Gas permeable plastic film (polyethylene might do) allows only gasses to pass, keeping solute in and particulates out. Can be chosen to reduce the permeability of co2 relative to the other gasses.

Pressure regulated valve helps with ingress by only opening when the pressure inside the battery is higher than the atmosphere, thus preventing dust etc getting in by brownian motion as would occur with a simple hole in the battery case. Could also maybe be just a one way valve. In VRLA batteries they do not activate until a substantial pressure has built up because the hope is that most of the gasses will recombine in the electrode separator or if there is a catalytic recombiner, and the valve is more of a safety device. If there is no hope of recombination at all there may be little point in pressure regulated valve instead of just a one way valve. Maybe could be a liquid valve but then over the years the liquid might escape as mist etc. even if a nonvolatile liquid is used.

Design the vent hole to have a path that makes dust getting in harder, and as small as possible.

A porous material like the material used in doulton ceramic water filters, or plastic microporous material film (or a mini sterilizing filter as used in home brewing on the aerator air lines which use them) or fibrous mat could help filter dust and mist out of the air to prevent ingress and egress of those things.

An anti-mist filter like used on air pumps to remove oil mist could help prevent escape of mist.

Use high purity materials when replenishing electrolyte to reduce the addition of contaminants, could cost extra and/or be harder to obtain though.

Sealing the battery

The evolution of hydrogen and oxygen gas is a problem to a greater or lesser extent in all batteries with an aqueous electrolyte. This includes lead acid, NiMH and nicad, but the problem is particularly bad in nickel iron due to the quantity of gas produced being higher and for some reason the chemistry apparently not being amenable to the cheaper approaches used in the other types, possibly including that hydrogen is evolved even when the battery is not being overcharged.

This problem can be dealt with in a number of ways to the extent the battery can be considered "sealed" in that there should be no need to add electrolyte over the course of the batteries intended lifetime, which includes:

-Reducing it to an acceptable level so low that the supply of electrolyte is not the limiting factor in battery life. Especially helps if the battery life is not that long. Depends on clever chemistry, making the iron electrode (where hydrogen is evolved on overcharge) extra large to prevent formation of hydrogen gas until well after the battery is fully charged (because the nickel electrode is fully charged well before the iron one is, preventing the battery from storing any more energy after that point).

-Recombining the gasses There are a wide range of approaches used to do this in batteries of various sizes and types, see the research page for links and patents and notes. In sealed lead acid batteries they can get the gases to recombine in the porous electrode separator by getting the oxygen evolved to the other electrode, where it promptly recombines with the hydrogen for some reason.

The other common method is catalytic combiner caps, also called "hydro caps" which catalyze the conversion of hydrogen to oxygen. The big problem with this is that they usually use platinum group metals which are extremely rare and expensive, albeit in small amounts. Research needs to be done to determine if the relevant metals might be recoverable in the very small amounts needed locally. Patents indicate it might be possible to use the cheaper more common metals like osmium.

Research also needs to be done to determine if different more readily available catalysts like Raney nickel or something might be made to work.

The design of such caps is also not entirely trivial, as the catalyst surface must be kept free of liquid water and any mist from the electrolyte. A lot of heat can also be produced, especially during overcharge conditions.

It might be possible to ignite the mixture in a controlled and safe way with a spark gap or heated nichrome element, thereby eliminating the catalyst metals.

Whatever method is chosen there is also the choice of shared gas space and non-shared. In shared gas space the cells share the same atmosphere and so the water that is produced by recombination needs to be distributed equitably back to the cells again, or water or electrolyte solutes will accumulate in one cell or another. And thermal gradient will also result in redistribution of the water by evaporation and condensation. Non-shared gas space is the simplest in this regard, with each cell having it's own atmosphere, but then you need a separate combiner mechanism for each cell (although of fractional capacity), which may be more complex to manufacture.

Combiner caps made for lead acid batteries might work for us for now, and are readily available. But there may or may not be some minor snags with e.g. access to the catalyst being blocked by the solutes in the electrolyte accumulating, whereas in lead acid the electrolyte solute is also a volatile liquid itself rather than a solid in NiFe. Purchasing ones made for NiFe specifically has the problem that they would likely not be readily available and the supply might dry up in the future if the manufacturer stops making them or puts the price up.

However the battery could be designed, with some compromises, to work in either sealed or non-sealed mode.

Also, sometimes the gasses are not produced in stoichiometric proportions, usually there is an excess of hydrogen because the oxygen reacts with other components in the cell or electrolyte instead of going to O2 gas. Obviously this can't continue forever or it would cause major problems with the battery chemistry and limit battery life. It usually only happens for a while until equilibrium is (nearly) achieved, with the ratio of evolved gasses getting closer and closer to stoichiometric for recombination to water as time goes on, either during the charge cycle or with time after the battery is built. Thus there still needs to be provisions to allow some gas escape, even aside from the safety issues.

If it occurs cyclically (not clear yet form information available) then if venting the excess occurs every cycle, it would cause some loss of electrolyte. Unless it is quite low this is bad. Instead the container will probably have to be made to stand these transient pressures and contain the gas until the other of the pair is also evolved and recombination can proceed.

Electrode production options

There are many different ways to make the physical electrodes given active material. The Edison process involved tubes packed with powdered active material, nickel or graphite flakes, molasses and some additives such as cobalt hydroxide (see other reactions and additives section) under about 4000 PSI and with about 8 grams of the mixture per tube, each of which was about a quarter of an inch in diameter and formed of nickel plated perforated sheet metal and reinforced with rings of metal in some areas. See his patents for details. These are then connected together to form the nickel electrode. He made the iron is in either a similar way or by compressing iron active material into a brick with copper crystals, mercury and other additives.

A very similar process is was still used as lately as the nineties by some manufactures, who may still be using it. For some reason they use smaller tubes only a few millimeters wide.

The changhong batteries are pocket-plate type. Verification is needed on exactly what pocket plate indicates. It can include tubular but there seems to be a distinct method as well in use which involves essentially denting the surface into pockets, much like a tv dinner tray. This could be easier and cheaper.

Other current collectors that are described as being or having been used commercially are: Nickel fiber mesh and paper

Sintered nickel powder

A foil or mesh on nickel or nickel plated steel which is covered in powder then sintered to bond the particles to it, increasing surface area

Foil (for teflon bonded) can be bend or scored or etched to increase surface area

Nickel foam- nickel powder is mixed with e.g. polyurethane foam particles the surface of which they coat, packed together and heated at greater than 700 degrees, removing the polyurethane and leaving the nickel.

Nickel plated steel wool

Others described in patents but which don't seem to be used:

Carbonized polymer material, heat some polymers to 900 degrees and they carbonize into a relatively durable and conductive material which is chemically compatible more or less with both the nickel and iron electrodes. Carbon particles of activated carbon are mixed in too.

There may be others as well

Other ideas:

conductive plastics?

Getting the material onto the substrate:

Active material includes additives etc.

Used commercially: Mix the active material with teflon or another hydrophobic plastic particles, graphite particles, and some elastomer and a thickener. Exact compositions described in patents. Apply to mesh or foil and press hard, like 700 kg per cm2.

Mix it into a paste and apply to a mesh or foam by running the foam or cloth through rollers along with the paste. Apparently it stays put in the foam without any additives like thickeners or binders though I would have though it would slowly fall out. de-emulsifiers, thickeners and other additives are sometimes used to make the details of production easier.

A common method called vacuum impregnation is to dip the mesh or foam in melted nickel nitrate and then into hot sodium hydroxide solution, converting the nitrate to hydroxide. Presumably it is done under a vacuum else the air in the foam would prevent entry of the liquids.

Electrochemical impregnation, there are several ways to do it and a chemist could probably come up with more, but basically the right nickel compound precipitates out of solution in fine particles on the surface of the nickel matrix. The source of the nickel can be either the metallic nickel matrix (beefed up with extra nickel of course) or the surrounding solution.

Described in patents but not apparently used: In some cases the active material can be mixed with e.g. nickel fibers or fibers of the polymer to be carbonized, then the whole thing heated, bonding the fibers, flakes, whatever, together into a continuous mesh. The heating does not damage the active material if it is formulated right and done in the right atmosphere (not hard though).

list of tasks that need to be completed

If you can do any of the things below please do, and put a link to the location where the completed work is, or promote that item to a new section on this page. When the Pivotal tracker comes online these can be moved there.

-Decide between pocket plate and nickel plated steel wool: Can we get away without the diffusion bonding? Diffusion bonding takes hours at very high temperature, leading to high capital and energy costs. Other methods could maybe be used: ultrasonic welding, resistive welding, the fibers may be connected during the electroplate process satisfactorily. Also, the diffusion bonding's purpose is to reduce the bulk resistance of the steel wool but maybe we don't absolutely need to do so.

-look into electroless plating instead of electroplating. It looks as though it would require a lot of chemical and produce a lot of waste which would be somewhat toxic, compared with electroplating. For the iron electrode the pocket plate should be relatively easy because it doesn't have to be under such pressure, and it is more conductive. The battery handbook 3rd edition says they are made with stamped pockets from a steel sheet (much like a TV dinner tray). -Identify active material usage fraction for various electrode designs -come up with some reasonably good and workable battery designs that mesh with OSE specs - calculate materials and estimate manufacturing cost for them and pick what looks like would be the cheapest - hash out what would be the production process so have a reasonable idea of the complexity of what it will be before finalizing decision to use this design. If seems to be getting ungainly, go back and do likewise for a different design and maybe it will be more makeable. - produce bill of materials for prototype -identify suppliers -build and test it well -repeat thrice integrating knowledge gained in previous prototypes while hashing out the details of the eventual production line. -design production line -track down suppliers and produce bill of materials -prototype pieces of it -build the line and get it working.

Notes on interpreting patents and other documentation

Chemists have a terrible habit of interchanging the names of compounds as if they were synonyms based on family relations, and glossing over details. Nickel Oxyhydroxide if often referred to as nickel hydroxide in this context. Incidentally so is actual nickel hydroxide, which can get confusing for someone with limited knowledge of the art.

A nickel-iron battery likewise may use not just iron as the negative electrode but can also make use of the higher iron oxides like Fe3O4 (ferric oxide) called iron oxide as a reactant (need to check details on this). Similarly FeO (ferrous oxide or iron monoxide) is a problem in the batteries but is likewise called iron oxide. Similarly there are a couple nickel oxides and the name is often used to refer to several.

Note that often the individual electrodes are sometimes talked about (like with the iron plateau thing) in the absence of the other, which can happen because sometimes you can think of the battery to some degree as 2 half cells and many reactions proceed almost independently of what is going on at the other electrode.

Also it is a convenient way to talk about what happens if the electrode is completely charged/discharged or whatever which might not happen in a real battery. But they can never be fully separate, reactions at one usually end up influencing the other at least a bit, and sometimes important ones are basically prerequisite for certain reactions at the other. But it is interesting partly because they can get "out of sync" to some degree sometimes and be in different states of charge.

Basically you have to step away with the simplistic view of batteries that we are usually presented with and think of it in terms of the complex electrochemical system that is is.

See wikipedia "cathode" for an explanation of which is the cathode in an electrochemical cell.

Note on efficiency measures

The charge/discharge (also called round trip and overall) efficiency is the performance parameter that we care about, of course. Hypothetically it should be equal to the charge efficiency multiplied by the discharge efficiency. In this case the efficiency is energy efficiency.

The charge efficiency is often quoted in absence of the discharge or overall efficiency, which is very annoying as it makes it harder to compare different battery designs that are mentioned in the literature. In marketing materials it is probably used in the hope the customer will erroneously assume it is equivalent to overall efficiency, since it is always higher than overall.

The discharge efficiency is rarely referred to in isolation for some reason, probably because it usually more or less commensurate with charge efficiency and can be computed easily from the overall and charge efficiency. Commensurate does not mean equal though.

Not energy efficiency:

Faradaic and coloumbic efficiency: see wikipedia article. Unfortunately it is apparent in patents and other documents it is apparently that this is in fact often, either due to ignorance or more likely sloppiness, used to mean charge efficiency or overall efficiency so watch out for this.

Polarization of the electrodes, see wikipedia.

Overpotential, see wikipedia.

library

A lot of information has been gathered and this needs to stay available to other devs. For documents accessible on the net links should be provided, and the page should be spidered a few links deep to produce a backup copy the docs.

Some docs can be shared but aren't available online and I will upload the few I have and list them here.

Some docs cannot be legally put on the wiki but can be shared to at least 3 layers of passing the docs for free person to person, under fair use. A list of these ones I have now is below. Contact me at gregorfolouk@hotmail.com and I will send you a copy of any or all of them.

cyclic voltammetry studies of porous iron electrodes in alkaline solutions used for alkaline batteries

electrochemical behaviour of iron oxide electrodes in alkali solutions

performance characterisation of sintered iron electrodes in nickel/iron alkaline batteries

comparative studies of porous iron electrodes

electrochemical behaviour of teflon-bonded iron oxide electrodes in alkali solutions

rechargeable alkaline iron electrodes

SECONDARY BATTERIES – Electrodes: Iron

On the key importance of homogeneity in the electrochemical performance of industrial positive active materials in nickel batteries

SECONDARY BATTERIES – NICKEL SYSTEMS

The electrochemical generation of ferrate at pressed iron powder electrodes: effect of various operating parameters

SECONDARY BATTERIES – Nickel–Iron

DEVELOPMENTAL STUDIES ON POROUS IRON ELECTRODES FOR THE NICKEL-IRON CELL

The electrochemical generation of ferrate at pressed iron powder electrode: comparison with a foil electrode

The nickel/Iron battery

A nickel-iron battery with roll-compacted iron electrodes

Nickel-based rechargeable batteries Original Research Article Journal of Power Sources, Volume 100, Issues 1-2, 30 November 2001, Pages 125-148 A. K. Shukla, S. Venugopalan, B. Hariprakash

Passivation of iron in alkaline carbonate solutions Original Research Article Journal of Power Sources, Volume 35, Issue 2, July 1991, Pages 131-142 M. Jayalakshmi, V.S. Muralidharan

Iron/carbon-black composite nanoparticles as an iron electrode material in a paste type rechargeable alkaline battery

Electrochemical behaviour of Teflon-bonded iron oxide electrodes in alkaline solutions P. Periasamy, B. Ramesh Babu, S. Venkatakrishna Iyer

Electrochemical characteristics of iron carbide as an active material in alkaline batteries Kiyoshi Ujimine, Atsushi Tsutsumi

ASSESSMENT OF PERFORMANCE CHARACTERISTICS OF THE NICKEL-IRON CELL

Role of activation on the performance of the iron negative electrode in nickel/iron cells M. Jayalakshmi, B. Nathira Begum, V. R. Chidambaram, R. Sabapathi and V. S. Muralidharan* Central Electrochemical Research Institute, Karaikudi 623006 (India)

The role of FeS and �NH / CO additives on the pressed type Fe 4 2 3 electrode C.A. Caldas, M.C. Lopes, I.A. Carlos ) Group of Electrochemistry and Polymers, DQ-UFSCar, P.O. Box 676, CEP 13565-905,

TEMPERATURE LIMITATIONS OF PRIMARY AND SECONDARY ALKALINE BATTERY ELECTRODES SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025 (U.S.A.)

RESEARCH, DEVELOPMENT, AND DEMONSTRATION OF A NICKEL/ IRON BATTERY FOR ELECTRIC VEHICLE PROPULSION Eagle-Picher Industries Inc., C and Porter Streets, P.O. Box 47, Joplin, MO 64801 (U.S.A.)

Rechargeable alkaline iron electrodes K. Vijayamohanan, T. S. Balasubramanian and A. K. Shukla Solid-state and Structural Chemistry Unit, Indian Institute of Science, Bangalore - 560 012 @&a)

RESEARCH, DEVELOPMENT, AND DEMONSTRATION OF A NICKEL/ IRON BATTERY FOR ELECTRIC VEHICLE PROPULSION Westinghouse Advanced Energy Systems Division, P.O. Box 10864, Pittsburgh, PA 15236 (U.S.A.)

• There are a few more which are probably available for free somewhere but which are still under copyright and therefore cannot be shared on the wiki, usually manuals on existing batteries etc.:

"the edison alkaline storage battery" doc from the edison battery company with some historical info about the batteries and their production

Operations manual(TN cell).pdf for changhong batteries(probably available on the changhong site)

"table 6 plus apendices" a piece of a manual for batteries that are in manufacture today, according to the person that sent me this doc they were made in Ukraine. (changhong=china)

Electrolyte Mixing Procedures V5611.doc This doc is for modern batteries still in production don't remember if it was ukraine or changhong ones

Changing Electrolyte pages 1 and 2.pdf this doc is for modern batteries, don't remember if it was the ukraine ones or the changhong ones

Commercial batteries

A list of existing manufaturers: -zappworks. According to email exchanges with these people these are apparently actually rebuild original edison batteries from the edison battery co.

-Changhong

-there is one in Ukraine according to one retailer who used to sell their batteries a couple years ago.

Journal articles indicate there are a number of manufacturers around the world producing them for industrial purposes etc.

See nickel iron battery .com for more

Retailers: -iron edison company

-zappworks sells their own

Current project status

Basically, having gone through all those patents and documents and so much more (check the edit history) my recommendation as to how to proceed is:

1. Obtain a a changhong battery. 2. Performance test it with a battery analyzer fr maybe 20 cycles to collect a bunch of data regarding charge discharge efficiency at various states of charge etc. This should be available from the manufacturer, but I have found that it is not in fact. Probably for marketing reasons. They figure you will just cross your fingers and buy it anyway.

We need this info anyway so we know what we are competing against in the market.

3. Dismantle the electrodes to look at their construction. In all my travels I have not been able to determine how pocket plate electrodes are made exactly this [2] is about it. Although there are many different ways and the basic idea is just to pack the material in at 2000 to 4000 psi (it becomes a solid mass probably a bit like soapstone) and then hold it at a pressure of about 40 psi. The main purpose of the pressures is to decrease the contact resistance between the constituent parts.

4. If the performance is higher than expected they may have developed new additives, especially if the efficiency is better than 60%. Check the battery for patent numbers. Contact the company to see if the battery or any part of it is patented. Look up the patents.

Under US patent system, they cannot conceal this information in the slightest - it must be fully made known - or the patent is not enforceable. That is why stuff usually has "protected by patent x" on it.

5. If there are not patent problems, analyze the active material by microscopic and chemical analysis to determine what the additives are so we can copy them. Fear not, this is not unethical as this is SOP in manufacturing.

6. Design battery Open battery prototype I while keeping the production line in mind. To keep costs low there will probably need to be a bit of custom equipment for electroplating etc which can be made with the replab but not really be part of it.

7. Build, test.

I think it is most probably by a ways that pocket plate is the best, for a variety of reasons, mostly simplicity of manufacture, not tubular and not sintered and not mesh and not teflon bonded and not nickel plated steel wool. Changhong even uses pocket plates for their starting lighting ignition batteries so it should be good.

Related pages

• Batteries
• Nickel-Iron_Battery/Research
• Nickel-Iron_Battery collaboration and correspondence
• Battery chemistry comparison
• Nickel-Iron SLI battery
• Nickel-Iron Off grid battery
• Edison Battery
• Impact of battery characteristics on off grid system cost