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 or NiMH battery in that nickel oxyhydroxide is used as a cathode, but iron is used instead of the toxic metal complexes in NiCd and most NiMH batteries as the anode. During discharge, both metals turn into their hydroxide forms: Ni(OH)2 and Fe(OH)2. (see the wikipedia article under electrochemistry). It should be possible to build it in a discharged state, combining the appropriate hydroxides of Nickel and Iron. 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. (We will definitely need someone who knows some chemistry and is willing to put in some time at at least several stages in this development process.)

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 306,000C, which is approximately 3.17 moles of electrons. Sheet steel will form a base material for the electrodes, so iron is not a limiting factor. Nickel's electrochemistry in an NiFe battery indicates a 1:1 molar ratio, so 3.17 moles of nickel will be required. 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 Oxide is toxic. The Appropriate Technology Collaborative is investigating toxicity [1].
• The lye electrolyte is caustic and corrosive, but perhaps could be used in small amounts.
• Suspending the lye in glycerin also mitigates effects.
• Glycerin is a by-product of creating bio-diesel, thus using a waste of a different process.

Sources

FusionBeads [2] 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, although sheet could be used for electrode material. Those guys must be making generous profit to say the least.

There are several ways to make the nickel electrode which require different raw materials. See electrode sections for details. In short there are established ways which use metallic nickel, oxyhydroxide, nickel oxide (NiO2 I think), nickel nitrate and potentially other salts, and maybe the hydroxide. Which material will be needed can be chosen on price, availability and the ease of the associated manufacturing technique.

A look on alibaba indicates that the nickel compounds may be substantially cheaper than the metal.

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 4. 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.

Sticking points and contributions imminently needed

We need to obtain the documents with the titles below. They are almost all available through sciencedirect.com, just search the titles. Linking to them directly is not possible because of the way they do the URLs. If you can obtain these in some way, please do so without delay. I suggest temporarily changing your browser's default download folder to a new folder to fill up or something for efficiency.

Then these can be legally shared by e.g. zippyshare.com with other developers who ask for a copy under the fair use doctrine.

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.

-To produce a battery that is economical, relatively easy to make, and which works to satisfaction (~0.2C, equal to or greater than 60% round trip efficiency) with efficient use of prototyping time, we need this information. I volunteer to read them all and come up with a plan for the next prototype(s) but do not have access. I can go back and get the full citations if they are for some reason needed. -Gregor

Most important:

Assessment of performance characteristics of the nickel---iron cell

SECONDARY BATTERIES - NICKEL SYSTEMS Nickel–Iron

SECONDARY BATTERIES - NICKEL SYSTEMS Electrodes: Nickel

SECONDARY BATTERIES - NICKEL SYSTEMS

SECONDARY BATTERIES - NICKEL SYSTEMS Electrodes: Iron

The nickel/iron battery

A nickel-iron battery with roll-compacted iron electrodes

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

6V, 60Ah nickel-iron battery. [3] Bulletin of Electrochemistry. Vol. 6, no. 2, pp. 263-265. 1990 <--- not available through sciencedirect.com

Less important but still highly desirable: The role of FeS and (NH4)2CO3 additives on the pressed type Fe electrode

Passivation of iron in alkaline carbonate solutions

Electrochemical characteristics of iron carbide as an active material in alkaline batteries

­Temperature limitations of primary and secondary alkaline battery electrodes

97/03847 Performance characterization of sintered iron electrodes in nickel/iron alkaline batteries

Nickel-based rechargeable batteries

Performance characterization of sintered iron electrodes in nickel/iron alkaline batteries

On the key importance of homogeneity in the electrochemical performance of industrial positive

active materials in nickel batteries

Electrochemical behaviour of Teflon-bonded iron oxide electrodes in alkaline solutions

Rechargeable alkaline iron electrodes

Performance characterization of sintered iron electrodes in nickel/iron alkaline batteries

Role of activation on the performance of the iron negative electrode in nickel/iron cells

Rechargeable alkaline iron electrodes

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

Research, development and demonstration of a nickel—iron battery for electric vehicle propulsion there are several papers with this term

The role of FeS and (NH4)2CO3 additives on the pressed type Fe electrode

There are some less important ones on the research page.

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.

Note that in electrochemistry the cathode is the electrode to which cations are attracted. In other words the positive electrode, when when talking about the exterior of the battery could be called the anode. This is due to historical reasons.

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 polymer binder loaded with graphite or other carbon particles which is then pyrolized can be made, with the pyrolized polymer being the conductive grid. Polymer binders (not pyrolized) filled with conductive particles are often used in modern batteries. The mix is made, then pressed with great force onto a nickle 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 block, and heated to melt or diffusion bond the flakes/fibers together, producing a conductive matrix surrounded by active (powdered) 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 and is relatively easy; conductive powder or fibers or flakes (graphite, nickel or nickel cobalt alloy) are mixed with the active material and pressed into "pockets" formed from perforated metal sheets.

For the iron electrode high surface area solid iron electrode may be used plain or with small amounts of something to provide sulfide ions like magnesium sulfide, iron sulfide or ever elemental sulfur, to cause activation of the electrode (removal of the iron monxide layer as the sulfur is more electronegative than the iron). For high purity powder like carbonyl iron the sulfide needs to be added. Otherwise it is often 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 meters per gram, which may correspond to roughly 10 micron average particle size.

Loose powder is not ever used, because the conductivity between particles is too low. In the the case of the nickel electrode, they must be at least pressed together (pocket type) or surrounded with a fine conductive matrix (e.g. 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) 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). This is because the nickel oxyhydroxide is not very conductive (see other reactions section). Nickel hydroxide is even less conductive (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.

In at least one of the Edison batteries he chose to use mercury to increase the conductivity between iron particles but that may have been a battery intended for Starting and lighting (SLI) in cars, which requires a very low internal resistance as discharge rates can exceed 20C during starting. We need no more than 1C or at most 2C (lithium ion are 2C or so usually) for general use and short term load leveling, and 0.1 may do (just) for solar power system energy storage. If we did need high currents sintered electrodes would be more sensible. Commercial batteries like the Changhong batteries intended for solar use are rated for 0.2 C but they make batteries capable of 10C for starting locomotives too. The C ratings are only guidelines however and can be exceeded greatly at cost of efficiency and energy that can be used - 6 C produces a capacity of 65% rated capacity for the battery in the sealed battery testing doc.

It needs to be determined exactly how the changing shape of the electrode goes. 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.

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 itsself. 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 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.

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

-and 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.

- 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 mes h 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. Sulfate is also needed to keep the iron electrode active so when it is used up the battery dies.

-accumulation of sulfur on the surface of the iron electrode esp. at lower temperatures and high discharge rates.

-deposition of iron in the nickel compound crystal structure <--needs more research

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

-carbonate and the other one in the battery hadnbook undesirable ions <-- need to add those other ones.

probably all kinds of minor undesirable contaminants, edison mentiones manganese , high purity iron like carbonyl iron is often used same for nickel electrode. Howevetr this may be expensive

lithium hydroxide apparently improves the thermodynamic reversibility of reactions and slows down the iron poisoning of the nickel elecrode maybe this indicates longer life and higher charge/discharge efficiency , we need a chemisty who can identify other ways of improving esp the charg/discharge efficiency by identifying other acceptable additives that might work.

-evolution of gasses at the nickel electrodes during charging, this could play into the ow efficiency but may only be commesurate with other prerequisite reactions at the iron electrode and unpreventable in themselves. Another contributor to low charge/discharge efficiency maybe.

- Evolution of gasses at electrode during periods when a charged battery sit there for future use (charge-stand), again in conjunction with prerequisite activity at the iron electrode. Another cause of self discharge.

-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 could corrode the nickel possibly leading to failure.

Need to add references but should have the sci docs first or will take forever and be low quality refs anyway.

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.

- 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.

Other 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 down 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 fraction of the battery that is actually active material, and the fraction of material that is available for actual use all vary quite substantially with the design of the electrodes, and the amount of electrolyte added etc.

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.

factors affecting cost

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 and nontoxic 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 wool current collector.

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 many nickel oxides and the name is often used to refer to several.

There are also several different reactions that are important to contribute output energy in the battery, not just the one on the wikipedia page. (need to add details)

Related pages

http://openfarmtech.org/wiki/Batteries http://openfarmtech.org/wiki/Nickel-Iron_Battery/Research