Patent Application
20160204441
This invention proposes thin (˜1 cm) home wall energy storage devices based on zinc-air and nickel-zinc batteries with replaceable and rechargeable zinc modules.
Energy storage devices are key components of future economy. Zinc batteries, which are low cost, high energy and safe to operate, are prospective storage devices for reserve power, electric grid, and transportation.
Batteries for homes recently received special attention: at the end of April 2015 Tesla Motors offered 10 KWh, 2 KW batteries of 130 cm×86 cm×18 cm size. These batteries have been advertised as wall mounted. The batteries had moderate power capabilities about 2 KW. Lithium batteries with higher performance (for example 1 KWh battery with 1 KW power) are essentially more expensive with prices in the range $600/KWh-$900/KWh.
Batteries with nickel oxide-hydroxide cathodes (also referred as nickel cathodes) are attractive because of long cycle life of the nickel electrode. Linden's Handbook of Batteries specifies lifetime of nickel-cadmium batteries as 8-25 years. The cadmium electrode has been phasing out from mass production because of safety concerns. Nickel-metal hydride batteries that have replaced nickel-cadmium storage devices are more expensive that nickel-cadmium batteries.
The commercialization of large-sized nickel-zinc rechargeable batteries is appealing because of relatively high discharge voltage 1.65V, low cost, safety, and high power capabilities. Nickel-zinc batteries have 30% higher energy density in comparison with nickel-metal hydride devices. A nickel-zinc battery with the cost about $300/KWh and power capabilities of a lithium battery, ten years lifetime, and 5,000-7,500 charge-discharge cycles can be considered as effective substitute for large-sized lithium batteries.
Zinc-air batteries are the cheapest (based on cost per energy density) batteries at market, and allows very high specific energies up to 280 Wh/kg. Rechargeable zinc-air batteries have two basic designs: a) batteries with bifunctional air-electrodes, and b) batteries with dual air electrodes. In case of dual air electrodes one electrode is used for air reduction while another one for oxygen evolution. In case of rechargeable batteries with dual air electrodes the growth of metal dendrites is localized between metal and oxygen evolution electrodes. As the result no dendrites appear at the interface between zinc and oxygen reduction electrodes what eliminates short circuits during discharge. The use of dual air electrodes allows better selection and optimization of current collectors as well as catalysts to insure better cycle life of the storage devices.
An example of a battery with dual air electrode is described by Tzidon et al in WO Pat. No. 2012/156872 A1. This battery has six electrodes: two zinc, two air (reduction), and two oxygen evolution electrodes. A metal-air battery assembled from elemental cells is arranged face-to-face, and requires leaving air gaps about 1 mm-2 mm to allow air access to the whole surface of the air electrode. Taking into account that the thickness of an elemental cell is about (or less) than 10 mm, the presence of air gaps increases battery volume by 10%-20%. Rechargeable batteries with zinc anodes have cycle life about 500-900 cycles.
The objectives of this invention are as follows:
This invention uses rechargeable and replaceable zinc cartridges as components of nickel-zinc batteries. The cycle life of the batteries can be increased by replacing zinc cartridges at about 10% of the battery cost. As the result the total lifetime of the anode can be extended to be compatible with that of the nickel-oxide hydroxide cathode. It is suggested a flat design of the modules interconnected with channels as basic elements of wall mounted batteries. The home wall battery design includes rotational joints to assure zinc cartridge replacement without disassembling the batteries.
The design of the zinc cartridges is improved by using current collectors covered with Zn—Cu—Bi alloy. Zinc composition is formulated using additives of polyphenylenediamines and zirconium hollow fibers. A flat module with battery/supercapacitor characteristics has been demonstrated.
Low cost rechargeable zinc cartridges are intended to be used as the components of the nickel-zinc battery. After degradation an old zinc cartridge is replaced by a new one at about 10% of the battery cost to serve the next period. As the result the capital cost of the battery is increased by 10% for the second period, but not by 100% when the battery is replaced completely.
The specific of the design is a flat low cost plastic cell, and a module assembled by gluing, ultrasonic welding, heat treatment, or plastic welding.
A replaceable zinc cartridge is formed of zinc electrode 3 that includes a current collector and zinc electrode composition, and sealed with separator envelop 4. The thickness of the cartridge is selected in such a way that it fits free space (pocket) of the cell, and can be moved out of the cell without any physical or functional damage to the electrode. Typical thickness of the zinc cartridge is in the interval from 0.1 mm to 1 cm. The cartridges with lower/larger thickness will also work, but might be unpractical. The idea of a replaceable electrode is applicable to any other rechargeable electrode that can be used with nickel-metal and metal-air batteries. For example a replaceable and rechargeable anode can be formed from iron, cobalt, cadmium, nickel hydride, or the alloys of metals. On the other hand the idea can be applied to other batteries like silver-zinc battery if a high cycle life silver electrode is available.
The replacement of the zinc cartridge can be performed when the battery (and the nickel electrode) is discharged. In this case a new zinc electrode, which replaces old one, should be also in the discharged state. This can be achieved by formulation of the zinc electrode on the basis of doped zinc oxide and additives. A zinc electrode formed from zinc powder can be chemically or electrochemically discharged before moving into discharged nickel-zinc battery. The zinc cartridge can also be replaced when the nickel electrode is in the charged state; in this case a charged zinc electrode is used to complement the state of charge of the nickel electrode.
Zinc cartridge includes a zinc electrode wrapped in the separator, or in the anion-exchange membrane. The separator/membrane envelope is hermetically sealed, so that ions can exchange with electrolyte solely through the separator or membrane or a combination thereof. Separator is made from a porous material stable in alkaline solutions. Examples of separator materials include polyethylene, polypropylene, and cellophane. Such a porous material can include a thin layer of an anion exchange material.
The zinc electrode can be formed from zinc powder, or zinc oxide doped with lead, bismuth, indium, aluminum or other metals that inhibit hydrogen evolution during charging. Zinc or zinc oxide paste can also include carboxymethylcellulose, polyvinyl alcohol, polyacrylic acid, polyamines, and similar additives. The zinc electrode can further include materials that improve its performance, for example zirconia fibers in the amount 0.5%-7%.
The current collector of the zinc electrode can be produced from copper, copper alloys, nickel, nickel alloys, lead, lead alloys, steel, stainless steel, bismuth, bismuth alloys, tin, tin alloys, zinc and zinc alloys, silver and silver alloys, carbon, graphite, expanded graphite, graphene, composites of graphite materials. The current collector can be covered by an additional layer to increase conductivity, to protect from corrosion, to improve mechanical, chemical or physical properties as required by the system. The material of an additional layer can include zinc, tin, lead indium, bismuth, antimony, nickel, silver or their alloys. The ratio of the components of the alloys can be selected from interval from 0.1% to 99.9%. In certain special cases the content of an additive can be lower than 0.1%. The third component can be added if required. Said metal layer can be deposited by electroplating, electroless plating, hot metallization, painting, and liquid metal pulverization.
The current collector can be processed by rolling, casting, expanding, printing, stamping. For example zinc, (or its alloy with lead, 1 mass %,) can be casted at temperature 550° C. to form a grid. Another approach is to roll zinc sheet to thickness about 0.5 mm, then slit the sheet into strips of 1 mm width, then cast zinc again locally to unite the strips in one current collector. Such a current collector is lighter than a current collector formed completely by casting by about 30%-50%.
The current collector of this invention is covered by a layer of zinc-copper-bismuth alloy, which improves long term stability of the current collector. The advantage of the mentioned alloy over other alloys its low toxicity and flexibility. The composition includes 15%-35% of bismuth, 0.5%-5% of copper and the rest is zinc. The alloy is deposited by electrochemical or chemical plating or casting. For example a current collector made of brass can be covered with zinc-copper-bismuth alloy by deepening the basic current collector into alloy at 490° C.
Nickel electrode of the battery can be produced starting from nickel hydroxide of the battery grade that includes, for example, cobalt and zinc additives in amount from 1 to 10 percent. Nickel hydroxide is mixed with nickel powder, for example T255 of Novamet corporation, which is added in the amount 1%-20% by weight; about 0.5%-5% of ptfe dispersion is included as a binder, a 0.5%-4% of hydroxymethylcellulose is added to improve wetability. The mixture is turned into paste by adding water or electrolyte, and rubbed into nickel foam electrode.
When the anode is made of zinc oxide composition, both electrodes (nickel hydroxide and zinc oxide) are mounted into battery, and reduced by continuous or pulse current with the amount of passed electricity exceeding theoretical by about 10%-50%. If the zinc electrode is made of zinc powder composition, the nickel electrode is charged in a separate electrochemical cell to be compatible with the charged zinc electrode.
The current collector of the nickel-oxide hydroxide electrode is produced from nickel, titanium, stainless steel, cobalt, lead, and alloys of mentioned metals. The current collector can be formed from mesh, foam, corrugated metal sheet, or expanded metal. A current collector for a wall mounted nickel electrode is produced as a composite electrode, which is foil on one side and foam on the other.
This invention proposes current collectors for nickel-zinc and zinc-air batteries with one side as continued sheet, while on the other as foam, expanded metal, mesh or other high surface area material. The composite current collectors can be formed from one metal, for example nickel, or two different materials, for example nickel and stainless steel. The foam portion can be made from carbon foam. The current collector can be produced by welding (including ultrasonic and laser welding), gluing, soldering, pressing, rolling, electrochemical plating, electrochemical etching (on the high surface area side), chemical etching, or pulverization with subsequent thermal treatment.
Electrolyte for nickel-zinc and zinc-air batteries is formulated on the basis KOH, NaOH, LiOH or mixture thereof. Typical electrolyte mass concentrations in water, or mixture of water with organic solvent is in the interval 10%-40%.
The increase of the battery life by replacement of the zinc cartridge can be accomplished in a zinc-air battery where the zinc electrode is low cost, and has short cycle life, while the air reduction and oxygen evolution electrodes have long lifetime. Two air electrodes, one for air reduction, and another for oxygen evolution, eliminate the use of a bifunctional rechargeable air electrode, and increase lifetime of both air electrodes. Unlike nickel-zinc battery, a three electrode zinc-air storage device does not require any adjustment of the red-ox state of the zinc electrode because two air electrodes include only a layer of a catalyst. For this reason the zinc cartridge in the zinc-air battery works like a fuel of a fuel cell. A zinc-air battery with replaceable and rechargeable zinc cartridges can be considered as a hybrid of a rechargeable battery and a fuel cell.
The design of the three electrode zinc-air cell can be similar to nickel-zinc cell illustrated in
The oxygen evolution electrode includes at least a gas evolution catalyst layer, and a hydrophobic layer exposed to air. The hydrophobic layer is formed from hydrophobic carbons, nitride materials, (for example boron nitride,) ptfe or polysilicon rubbers. The current collector is made of nickel, nickel alloys, stainless steel, lead, manganese dioxide or their alloys or compositions. The catalyst for oxygen evolution can be selected from iridium oxide, ruthenium oxide, or composition of these materials, mixture or chemical compositions based on nickel cobalt oxides, manganese dioxide or other oxygen evolution catalysts know in the field.
Oxygen reduction electrode includes at least catalyst layer, and hydrophobic layer exposed to air. The composition of the hydrophobic layer is similar to the composition of the hydrophobic layer of the oxygen evolution electrode, while oxygen reduction electrode can include catalysts for oxygen reduction such as manganese dioxide, nickel cobalt oxides, nitrogen doped carbon, iron, cobalt or their complexes deposited on carbon, graphene, and expanded graphite.
The difference between nickel-zinc and zinc-air battery is in the charge-discharge voltage. The zinc-air battery is discharged at about 1.0V-1.25V depending on current, while nickel-zinc battery is discharged at 1.65V. The nickel-zinc battery can be charged at 1.7V-1.8V while the zinc-air battery at 1.95V-2.3V. As the result the recharging efficiency of the nickel-zinc battery is higher about 0.8-0.85 when the same characteristic of a zinc-air battery is about 0.5-0.65 depending on the effectiveness of oxygen reduction and oxygen evolution catalysts. The efficiency of recharge of the zinc-air battery can be increased when the zinc oxide electrode is reduced in a separate cell with a counter electrode (electroactive substrate) different from water.
There is a line of organic or inorganic substrates, which oxidation can be performed at essentially lower potentials than water oxidation, and the regeneration efficiency can be effectively increased. An example of such a substrate is chlorine that can be oxidized at potentials lower than the potential of water oxidation to oxygen.
Many components of the zinc, air and oxygen evolution electrodes are substances, which are used as electrode components of supercapacitors. Examples of such a materials include carbon black, N-doped carbon materials, graphene, lead, tin, copper, iron, nickel, bismuth, silver powders; conducting polymers: polyaniline, polythiophene, polypyrrole and their derivatives; manganese oxides, nickel oxides, cobalt oxides, lead oxide, ruthenium oxide, iridium oxide, silver oxide, and compositions/alloys of these materials.
On one hand mentioned substances can accumulate extra charge at the border with electrolyte electrostatically. On the other hand these materials can function as catalysts or conducting additives of the metal-air batteries. For example, oxygen evolution electrodes often include ruthenium and iridium dioxides catalysts, which are also materials for supercapacitors.
A zinc-air battery, which includes high surface area carbon materials, has embedded supercapacitance that can influence the shape of the charge-discharge curves. An example of a charge-discharge characteristic of a zinc-air battery with extra capacitance is provided in
To meet temporal power requirements of an application, the zinc-air battery often requires a supercapacitor connected in parallel to the battery. The addition of a supercapacitor can increase weight/volume ratio, and the price of the storage device. The internal supercapacitance can raise temporal power capabilities without any increase in the weight, volume and price of the device. It is important to note that supercapacitor properties are inherent to the electrodes of a zinc-air battery, and appear to a certain degree as intrinsic property of a metal-air battery irrespective of intention to use them.
The cells can be united in the modules as is shown in
Two types of nickel-zinc batteries can be assembled: sealed batteries similar to conventional nickel batteries, and batteries that have no conventional sealing. Latter can lose humidity slowly because of evaporation. The internal channels of the module, and flexible tubes make electrolyte common for all cells. The compensation (preferably automated) of the evaporated electrolyte is processed using one opening for the whole battery.
According to this invention “smart ABS” can be applied as module case material. ABS can be processed by most conventional low cost 3d printers. Smart ABS is a variety of ABS with melting temperature about 10° C. higher than ABS.
Nickel-zinc or zinc-air modules can be assembled in batteries using rotational joints as presented in
It is obvious that in case of three electrode zinc-air batteries a switch is required to transfer the battery made of several elemental cells from charge to discharge mode. The solution offered in this invention is based on the circuit shown in
A battery made of four cells is used as an example. Me, OR and OE of
To charge the battery, voltage from a power supply is applied to the battery, and to the relays circuit control by turning the switch 15 “on”. An optional resistance 16 can be used to decrease voltage in correspondence with the relay specifications.
This example demonstrates a flat nickel-zinc battery designed with a wall mounted nickel-oxide hydroxide electrode, and a replaceable zinc cartridge. Zinc electrode current collector (4 cm*6 cm) has been produced by deposition of the Zn—Bi—Cu alloy with mass content 80% Zn, 20% Bi and 5% Cu on brass mesh 40 at 550° C. Electroactive zinc composition was prepared by mixing 8.1 g of zinc dust, 5 mkm size, 0.2 g of lead oxide, 0.2 g of m-aminodiphenylamine, 0.2 g zirconia hollow fibers, 0.2 g of ptfe dispersion, 0.1 g of carboxymethylcellulose with water. The mixture is deposited on brass current collector and wrapped into cellophane separator. The separator is sealed using double scotch.
Nickel electrode of the same size is prepared by welding nickel foam (pore diameters 0.3 mm-0.7 mm) to the nickel sheet 0.2 mm thickness; mixing 8.1 g of nickel oxide-hydroxide that includes 2% of ZnO and 5% of CoO with 1.5 g nickel powder, 0.2 g ptfe dispersion, 0.1 g carboxymethylcellulose; adding water and mixing, rubbing the composition into the foam part of the current collector. The nickel hydroxide electrode was electrochemically oxidized at 100 mA/cm2 current in 30% KOH against nickel sheet counter electrode to produce nickel oxide-hydroxide electrode.
The base is formed by milling a pocket in 0.25″ thick polypropylene sheet. The nickel electrode and polypropylene sheet of 1/16 in thickness were glued to the base. The zinc cartridge was placed into the case between the nickel electrode and the plastic wall. The cell was filled with 30% KOH 5% LiOH solution. The cell was closed with the rubber plug, sealed by polysilicone liquid rubber, and dried at room temperature. The battery has been discharged at 31 load and 1.65V for three hours, and charged at 1.75V-1.8V for the same time. The zinc cartridge could be replaced by deleting the cartridge together with the rubber plug, removing the old zinc electrode, installing a new one, moving the cartridge with rubber plug into the cell, and sealing the cell with polysilicone rubber.
This example demonstrates assembling a module of three cell zinc-air battery, which is presented in
The air electrode catalyst was prepared by mixing 12 g of acid treated carbon black with 0.1 g-mol of m-phenylenediamine in 100 mL of 0.5M HCl solution. 0.05 g-mol ammonium persulfate and 0.05 g-mol FeCl3 were added to solution at 10° C. and mixed for 24 h. Produced precursor was dried, and heat treated at 800° C. for 1 h. Then the sample was leached in 0.5M H2SO4 at 80° C. for 5 h, washed and heat treated at 800° C. for 1 h again.
Three current collectors (4 cm*6 cm) were assembled by welding nickel mesh 40 to nickel foam. The air electrode catalyst was rubbed into nickel foam part of the electrode. The electrode was covered with a hydrophilic layer made from composition of ptfe dispersion in water and carbon black. This dispersion was mixed, and applied in form of 1 mm layer to the nickel current collector with the catalyst. The air electrode had been heat treated at 320° C. for 3 min. Three current collectors for the air evolution electrodes were assembled from stainless steel mesh 100. The catalyst layer of RuO2 was deposited by anodic oxidation of stainless steel 304 electrode in 1M HCl solution, and 0.01M solution of (NH4)2RuCl6 at 0.9V vs Ag/AgCl reference electrode for 30 min. Then hydrophobic layers were deposited on the top of the catalyst layers similar to that of the air electrodes. Then three air reduction electrodes, and three oxygen evolution electrodes have been glued to the base using hot melt glue to form three cells. Three zinc electrodes were placed in the pockets, and sealed with liquid polysilicone rubber similar to the nickel-zinc battery of Example 1. Then a circuit, similar to presented in
This application claims benefit to U.S. provisional application No. 62/044,666 filed Sep. 2, 2014, and to US provisional application No 6207926 filed Nov. 13, 2014, and to U.S. provisional application No. 62/167,581 filed May 28, 2015 all of the subject matter has been incorporated by reference. This work was supported by National Research Council—Industrial Research Assistance Program, Project No 829964, 2014.
| Number | Date | Country | |
|---|---|---|---|
| 62044666 | Sep 2014 | US | |
| 62167581 | May 2015 | US |
