Hybrid polyhalide electrolyte for static battery and method for manufacturing static battery cell

Abstract

A mixed polyhalide initial electrolyte for a static zinc halide battery is provided. There is also provided a method for manufacturing a static battery cell, the method comprising the steps of: providing an initial electrolyte comprising one or more chloride ion sources and one or more bromide ion sources, where the one or more chloride ion sources and the one or more bromide ion sources are provided in a predetermined ratio, the predetermined ratio is selected to produce a target amount of mixed polyhalide upon initial charging of the electrolyte; and forming an electrochemical cell comprising an anode, a cathode, and an initial electrolyte.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 422,229, filed on November 3, 2022, which is hereby incorporated by reference in its entirety. Technical Field

[0003] Described herein are hybrid polyhalide electrolytes for stationary batteries and methods for manufacturing stationary battery cells containing such electrolytes. Specifically, described herein are hybrid polyhalide electrolytes for stationary zinc - halide batteries and methods for manufacturing stationary zinc - halide battery cells containing such electrolytes. Background Art

[0004] Zinc - halide batteries have been developed as devices for storing electrical energy. Conventional zinc - halide batteries (e.g., zinc - bromide batteries) employ bipolar electrodes that are disposed in a stationary, i.e., non - flowing, aqueous solution of zinc bromide. The charge and discharge processes in zinc - halide batteries typically occur through redox couples such as Zn 2+ / Zn(s) and X - / X 2 reactions in the zinc - halide electrolyte. When the battery is charged by an electric current, the following chemical reactions occur:

[0005] Zn 2+ +2e - →Zn

[0006] 2X - →X 2 +2e - ,

[0007] where X is a halogen (e.g., Cl, Br, or I). Conversely, when the battery discharges, the following chemical reactions occur:

[0008] Zn→Zn 2+ +2e -

[0009] X 2 +2e - →2X - .

[0010] These zinc halide energy storage batteries are formed in a bipolar electrochemical cell stack, where each electrode includes two poles such that an anodic reaction occurs on one side of the electrode while a cathodic reaction occurs on the opposite side of the same electrode. In this case, the bipolar electrodes are typically configured as plates, and the cell stack is assembled to form a prismatic geometry. During charging and discharging of the bipolar battery, the electrode plates serve as conductors for adjacent cells, i.e., each electrode plate serves as the anode of one cell and the cathode of an adjacent cell. In this prismatic cell geometry, the entire surface area of the electrode plates separating adjacent electrochemical cells transfers current from one cell to another.

[0011] Thus, when a conventional bipolar zinc halide battery is charged, zinc metal is electrodeposited on the anodic side of the bipolar electrode plate while molecular halogen species are formed on the cathodic side of the electrode plate. And, when the battery is discharged, the deposited zinc metal is oxidized to free electrons that conduct through the electrode plate and reduce the molecular halogen species to produce halogen anions.

[0012] Historically, due to the density gradients observed in the electrolyte, static zinc bromide batteries achieved limited energy and power densities. During battery charging, as the dense polybromide phase forms and subsequently sinks to the bottom of the cell, it becomes difficult to utilize the entire electrode surface area when charging to higher capacities and thus higher energy densities. Therefore, static zinc halide batteries face the inherent challenge of simultaneously increasing the energy and power densities of static zinc halide batteries without using a flowing electrolyte. Since flow batteries use a flowing electrolyte, no such density gradient is observed in the electrolyte of such flow batteries. Thus, the above challenges of static zinc halide batteries are not relevant to zinc halide flow batteries.

[0013] Chinese Patent CN102479968B discloses a redox flow battery using zinc chloride and zinc bromide solutions as electrolytes. The anode and cathode are made of an inert conductive material, and the zinc chloride and zinc bromide solutions are stored in an anode electrolyte storage tank and a cathode electrolyte storage tank, respectively. During battery operation, the electrolyte solution circulates between the battery module and the electrolyte storage tank with the help of a circulation pump.

[0014] BrCl was demonstrated in a Ti-Br-Cl flow battery (TBCFB) 2 - / Br -As a positive redox pair. See, for example, Xu, Y. et al., "A High Energy Density Bromine-Based Flow Battery with Two-Electron Transfer", ACS Energy Lett., 7, 1034-1039 (2022). See also Zou, Y. et al., "Reversible I - / I 2 / I + Four-electron Zn-I conversion 2 Aqueous Battery (A Four-electron Zn-I 2 Aqueous Battery Enabled by Reversible I - / I 2 / I + Conversion)", Nature Commc'ns, 12, 170 (2021).

[0015] Biswas, S. et al., "Minimal Architecture Zinc-bromine Battery for Low Cost Electrochemical Energy Storage", Energy Env't Sci., 10, 114-120 (2017), discuss the problems caused by the tendency of polybrominated species to separate and stratify in aqueous systems. However, they address this challenge by proposing a horizontal cell architecture that places the bromine cathode at the bottom of the cell, the zinc anode at the top, and abandons the use of complexing agents. This approach allegedly keeps the polybrominated species where they are needed, but introduces new challenges to commercially scalable cell architectures involving gassing, galvanizing, and efficient packaging of the cell. Summary of the invention

[0016] The present disclosure describes a mixed polyhalide initial electrolyte for a static zinc halide battery. The present disclosure also describes a method for making a static zinc halide battery cell including the electrolyte.

[0017] In one aspect, the present disclosure describes a method for manufacturing a static battery cell, comprising the steps of: providing an initial electrolyte comprising one or more chloride ion sources and one or more bromide ion sources, wherein the one or more chloride ion sources and the one or more bromide ion sources are provided in a predetermined ratio selected to produce a target amount of mixed polyhalide upon charging of the initial electrolyte; and forming an electrochemical cell unit comprising an anode, a cathode, and the initial electrolyte.

[0018] In some embodiments, the static battery cell is a static zinc halide electrochemical cell unit.

[0019] In some embodiments, the static zinc halide electrochemical cell unit is in a static zinc halide battery.

[0020] The initial electrolyte comprises one or more chloride ion sources. Non-limiting examples of the one or more chloride ion sources include, for example, ZnCl 2 , KCl, NH 4 Cl, LiCl, CuCl 2 , CaCl 2 , FeCl 3 , SbCl 3 , CrCl 3 , NaCl, BiCl 3 , quaternary ammonium salts having chloride anions, or combinations thereof.

[0021] The initial electrolyte comprises one or more bromide ion sources. Non-limiting examples of the one or more bromide ion sources include, for example, ZnBr 2 , KBr, NH 4 Br, LiBr, CuBr 2 , CaBr 2 , NaBr, AgBr, AlBr 3 , quaternary ammonium salts having bromide anions, or combinations thereof.

[0022] In some embodiments, the predetermined ratio of the one or more chloride ion sources and the one or more bromide ion sources is a molar ratio of total chloride ions to total bromide ions of from about 1:1 to about 13:1.

[0023] In some embodiments, the predetermined ratio of the one or more chloride ion sources and the one or more bromide ion sources is a molar ratio of total chloride ions to total bromide ions of from about 1:1 to about 2:1.

[0024] In some embodiments, the predetermined ratio of the one or more chloride ion sources and the one or more bromide ion sources is a molar ratio of total chloride ions to total bromide ions of from about 1.25:1 to about 1.5:1.

[0025] Another aspect of the present disclosure describes an initial electrolyte for a static secondary zinc halide electrochemical cell unit, comprising: about 5 wt.% to about 30 wt.% of ZnBr 2 ; about 5 wt.% to about 60 wt.% of ZnCl 2 ; about 10 wt.% to about 60 wt.% of H 2 O; and about 0.05 wt.% to about 20 wt.% of one or more quaternary ammonium agents. In another aspect, after the initial electrolyte is at least significantly charged, a mixed polyhalide is formed.

[0026] In some embodiments, the mixed polyhalide produced during charging, significant charging, or charging beyond significant charging may have the general formula [X (2n+1) Y (2m) - , where X and Y are different from each other and are independently Cl or Br, n is an integer between 0 and 5, and m is an integer between 1 and 5.

[0027] In some embodiments, when the initial electrolyte (having a predetermined ratio of different halides) within the electrochemical cell unit is charged until it reaches an open circuit potential greater than 1.82 V and a volumetric charge capacity greater than 54 mAh / mL, a mixed polyhalide is formed.

[0028] In some embodiments, one or more quaternary ammonium agents are independently selected from quaternary ammonium agents having the formula N + (R 1 )(R 2 )(R 3 )(R 4 )X - , where R 1 is hydrogen or an alkyl group, and R 2 , R 3 , and R 4 are each independently an alkyl group the same as or different from R 1 , and X - is chlorine or bromine.

[0029] In some embodiments, the initial electrolyte further comprises about 0.5 wt.% to about 15 wt.% of KBr and about 0.5 wt.% to about 15 wt.% of KCl.

[0030] In some embodiments, the initial electrolyte further comprises about 0.5 wt.% to about 15 wt.% of KCl. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] These and other features, aspects, and advantages of the present disclosure will be better understood when the following detailed description is read with reference to the accompanying drawings.

[0032] Figure 1 ​Shows an exploded view of an electrochemical cell unit according to an embodiment of the present disclosure.

[0033] Figure 2 Is a side view of a battery according to an embodiment of the present disclosure.

[0034] Figure 3 Is Figure 2 An exploded view of the battery of.

[0035] Figure 4 Is for Figure 2 An exploded view of the terminal assembly in the battery of.

[0036] Figure 5 Is for Figure 2 A front view of the battery frame member of the battery of.

[0037] Figure 6 Shows the effect of reducing the molar ratio of zinc chloride to zinc bromide in the electrolyte on the formation of polybromide at the bottom of the vial.

[0038] Figure 7 Shows the variation of the representative voltage with the test time of the mixed polyhalide initial electrolyte and the zinc bromide initial electrolyte (control) according to an embodiment of the present disclosure. The zinc bromide starting electrolyte forms polybromide during charging, while the mixed polyhalide in the present disclosure is not formed.

[0039] Figure 8 Shows the effect of the total Cl / Br molar ratio in the mixed polyhalide initial electrolyte according to an embodiment of the present disclosure on the discharge energy (Wh).

[0040] Figure 9 Shows the representative average coulombic efficiency (%) of the mixed polyhalide initial electrolyte according to an embodiment of the present disclosure and the zinc bromide initial electrolyte that forms polybromide during charging but does not form the mixed polyhalide in the present disclosure during ten charge and discharge cycles.

[0041] Figure 10 Shows the variation of the representative average coulombic efficiency of the mixed polyhalide initial electrolyte according to an embodiment of the present disclosure and the zinc bromide initial electrolyte that forms polybromide during charging but does not form the mixed polyhalide in the present disclosure with the cycle length.

[0042] Figure 11 Shows the variation of the representative cell discharge voltage (V) of the mixed polyhalide initial electrolyte according to an embodiment of the present disclosure and the zinc bromide initial electrolyte that forms polybromide during charging but does not form the mixed polyhalide in the present disclosure with the cell discharge energy density (Wh / L). Detailed Description

[0043] Embodiments of the present disclosure are described in detail with reference to the accompanying drawings, in which like reference numerals identify like or identical elements. It should be understood that the disclosed embodiments are merely examples of the present disclosure, which may be embodied in various forms. Well-known functions or constructions are not described in detail to avoid obscuring the present disclosure with unnecessary details. Accordingly, the specific structural and functional details disclosed herein should not be construed as limiting, but merely as a basis for the claims and as a representative basis for teaching one of ordinary skill in the art to make and use the present disclosure in virtually any appropriate detailed structure in various ways.

[0044] I. Definitions

[0045] As used herein, the terms “electrochemical cell” or “cell” are used interchangeably to refer to a device capable of generating electrical energy from a chemical reaction or facilitating a chemical reaction by introducing electrical energy. The electrochemical cell can be part of a bipolar stack or a monopolar (or single-pole) electrochemical cell. The electrochemical cell can be connected in series or parallel to any number of other electrochemical cells or can be a stand-alone device.

[0046] As used herein, the term “battery” includes an electrical storage device comprising at least one electrochemical cell. For example, a battery can be composed of about 5 to 50 electrochemical cells connected in series. A “secondary battery” is rechargeable, while a “primary battery” is non-rechargeable. For the secondary battery of the present disclosure, the battery anode is designated as the positive electrode during discharge and as the negative electrode during charging. Conversely, the battery cathode is designated as the negative electrode during discharge and as the positive electrode during charging.

[0047] As used herein, the term “electrode” refers to an electrical conductor used to contact a non-metallic part of an electrical circuit (e.g., a semiconductor, an electrolyte, or a vacuum). An electrode can also refer to an anode or a cathode.

[0048] As used herein, the term “anode” refers to the negative electrode from which electrons flow during the discharge phase of a battery. The anode is also the electrode that undergoes chemical oxidation during the discharge phase. However, in a secondary cell or a rechargeable cell, the anode is the electrode that undergoes chemical reduction during the charging phase of the cell. The anode is formed of a conductive material or a semi-conductive material, such as, for example, a metal (e.g., titanium or titanium coated with TiC), a metal oxide, a metal alloy, a metal composite, a semiconductor, a conductive plastic, etc.

[0049] As used herein, the term "cathode" refers to the positive electrode into which electrons flow during the discharge phase of a battery. The cathode is also the electrode that undergoes chemical reduction during the discharge phase. However, in a secondary battery cell or a rechargeable battery cell, the cathode is the electrode that undergoes chemical oxidation during the charging phase of the battery cell. The cathode is formed of a conductive material or a semiconductive material, such as, for example, a metal, a metal oxide, a metal alloy, a metal composite, a semiconductor, a conductive plastic, etc.

[0050] As used herein, the term "monopolar electrode" or "unipolar electrode" refers to an electrode that serves as the anode or the cathode of a battery cell and does not participate in the electrochemical reaction of an additional battery cell.

[0051] As used herein, the term "bipolar electrode" refers to an electrode that serves as the anode of one battery cell and the cathode of another battery cell. For example, in a battery, the bipolar electrode serves as the anode in one battery cell and as the cathode in an adjacent battery cell. In some instances, the bipolar electrode includes two surfaces, a cathode surface and an anode surface, wherein the two surfaces are connected by a conductive material. For example, a bipolar electrode plate can have opposite surfaces, wherein one surface is the anode surface and the other surface is the cathode surface, and the conductive material is the thickness of the plate between the opposite surfaces.

[0052] As used herein, "electrolyte" refers to a substance that behaves as a conductive medium. For example, the electrolyte facilitates the movement of electrons and cations in a battery cell. The electrolyte includes a mixture of materials, such as an aqueous solution of a metal halide salt (e.g., ZnBr 2 、ZnCl 2 etc.).

[0053] As used herein, the term "halogen" refers to any one of the elements fluorine, chlorine, bromine, iodine, and astatine that occupy Group VIIA (17) of the periodic table. Halogens are reactive nonmetal elements that form strong acidic compounds with hydrogen and can form simple salts therefrom.

[0054] As used herein, the term "halide" refers to a binary compound of a halogen with another element or group that has a lower electronegativity (or higher electropositivity) than the halogen to form a fluoride, chloride, bromide, iodide, or astatide compound.

[0055] As used herein, the term "polyhalide" refers to a molecular ion that contains three or more identical types of halogen atoms and has a total charge of -1. Non-limiting examples of polyhalides include, for example, Br 3 - 、Br 5 - 、Cl 3 -or Cl 5 - 。

[0056] As used herein, the term "polyhalide" refers to a molecular ion containing three or more bromine atoms and having a total charge of -1. When charging a battery in a halide electrolyte consisting mainly of bromide ions dissolved in a solution, the bromide is electrochemically converted to bromine (Br 2 ), which then combines with free bromide in the solution to form polyhalides. Polyhalides typically form a non-aqueous phase in the electrolyte when formed. Non-limiting examples of polyhalides include, for example, Br 3 - and Br 5 - (having molecular weights of 239.7 and 399.5 g / mol, respectively).

[0057] As used herein, "mixed polyhalide" refers to a molecular ion containing three or more different types of halogen atoms (such as bromine and chlorine atoms) and having a total charge of -1. When charging a battery in an uncharged electrolyte consisting of a selected ratio of bromide and chloride ions dissolved in a solution, the bromide is electrochemically converted to bromine (Br 2 ), and then at a higher charging voltage, the bromine combines with chloride ions in the solution to be further oxidized to form mixed polyhalides. In one aspect, mixed polyhalides are formed when using an uncharged electrolyte having a predetermined ratio of different halide ions. Non-limiting examples of the predetermined ratio of different halide ions in the uncharged electrolyte include, for example, a molar ratio of total chloride to total bromide of 1:1 to 13:1. Preferably, the molar ratio of total chloride to total bromide in the uncharged electrolyte is in the range of about 1.5:1 to about 2.5:1. Non-limiting examples of mixed polyhalides include, for example, BrCl 2 - (having a molecular weight of 150.8 g / mol) or ClBr 2 - (having a molecular weight of 195.3 g / mol).

[0058] As used herein, the term "anion" refers to any chemical entity having one or more permanent negative charges. Examples of anions include, but are not limited to, fluoride, chloride, bromide, iodide, arsenate, phosphate, arsenite, hydrogen phosphate, dihydrogen phosphate, sulfate, nitrate, hydrogen sulfate, nitrite, thiosulfate, sulfite, perchlorate, iodate, chlorate, bromate, chlorite, hypochlorite, hypobromite, carbonate, chromate, hydrogen carbonate (bicarbonate), dichromate, acetate, formate, cyanide, amide, cyanate, peroxide, thiocyanate, oxalate, hydroxide, and permanganate.

[0059] As used herein, "titanium material" can include, but is not limited to, titanium (in any oxidation state), TiC, alloys of TiC such as TiC x M (where x is 0, 1, 2, 3, or 4 and M is a metal), titanium carbide hydride, non-stoichiometric titanium-carbon compounds, and combinations thereof.

[0060] As used herein, "titanium carbide" can be used interchangeably with "titanium carbide material" and includes, but is not limited to, TiC, alloys of TiC such as TiC x M (where x is 0, 1, 2, 3, or 4 and M is a metal), titanium carbide hydride, non-stoichiometric titanium-carbon compounds, and combinations thereof.

[0061] As used herein, the term "zinc metal" refers to elemental zinc, also known as Zn(0) or Zn 0 .

[0062] For the purposes of this disclosure, the terms "dimethyl ether poly(ethylene glycol)", "DME-PEG" can be used interchangeably to refer to a polymer having the structure , where n is an integer. DME-PEG 1000 refers to a DME-PEG polymer having a number average molecular weight (M n ) of approximately 1000 amu, and DME-PEG 2000 refers to a DME-PEG polymer having a number average molecular weight (M n ) of approximately 2000 amu.

[0063] As used herein, the term "dimethyl ether" refers to an organic compound having the formula CH 3 OCH 3 .

[0064] As used herein, the term "aggregate concentration" refers to the sum concentration (e.g., wt.%) of each component of a class of components or a class of reagents (e.g., quaternary ammonium agents). In one example, the aggregate concentration of one or more quaternary ammonium agents in an electrolyte is the sum of the concentrations (e.g., weight percentages) of each component quaternary ammonium agent present in the electrolyte. Thus, if an electrolyte has three quaternary ammonium agents, the aggregate concentration of the three quaternary ammonium agents is the sum of the concentrations of each of the three quaternary ammonium agents present in the electrolyte. And, if the electrolyte has only one quaternary ammonium agent, the aggregate concentration of the quaternary ammonium agent is simply the concentration of the single quaternary ammonium agent present in the electrolyte.

[0065] As used herein, the term "alcohol" refers to any organic compound whose molecule contains one or more hydroxyl groups attached to a carbon atom. Examples of alcohols include methanol, ethanol, 1-propanol (i.e., n-propanol), 2-propanol (i.e., isopropanol), 1-butanol (i.e., n-butanol), sec-butanol, isobutanol, tert-butanol, 1-pentanol, or any combination thereof.

[0066] As used herein, the term "hydroxyl" refers to the -OH group.

[0067] As used herein, the term "glycol" refers to any class of organic compounds belonging to the alcohol family. In a glycol molecule, two hydroxyl (-OH) groups are attached to different carbon atoms. Examples of glycols include C 1-10 glycols, which include ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, hexanediol, or any combination thereof. Other examples of glycols include substituted ethylene glycols and substituted propylene glycols.

[0068] As used herein, the term "weight percentage" and its abbreviations "wt.%" or "wt%" are used interchangeably to refer to 100 times the product of the quotient of the mass of one or more components divided by the total mass of the mixture or product containing the components:

[0069] wt% = 100% × (mass of component(s) / total mass)

[0070] When referring to the concentration of a component or ingredient of an electrolyte, as described herein, wt.% or wt% is based on the total weight of the electrolyte.

[0071] As used herein, the term "quaternary ammonium agent" refers to any compound, salt, or material that contains a quaternary nitrogen atom. Non-limiting examples of quaternary ammonium agents include, for example, tetraalkylammonium halides (e.g., tetramethylammonium bromide, tetramethylammonium chloride, tetraethylammonium bromide, tetraethylammonium chloride, alkyl-substituted pyridinium halides, alkyl-substituted morpholinium halides, combinations thereof, etc.), heterocyclic ammonium halides (e.g., alkyl-substituted pyrrolidinium halides (e.g., N-methyl-N-ethylpyrrolidinium halide or N-ethyl-N-methylpyrrolidinium halide), alkyl-substituted pyridinium halides, alkyl-substituted morpholinium halides, viologens having at least one quaternary nitrogen atom, combinations thereof, etc.), or any combination thereof. The tetraalkylammonium halides can be symmetrically or asymmetrically substituted with respect to the substituents of the quaternary nitrogen atom.

[0072] As used herein, the term "viologen" refers to any bipyridinium derivative of 4,4'-bipyridine.

[0073] As used herein and in the zinc-bromide battery literature, a "complexing agent" generally refers to a quaternary ammonium organic compound having a positive charge. The complexing agent is used to melt, bind, or complex polybromo or polyhalide species formed in the battery, thereby producing a species in which the positively charged quaternary ammonium and the negatively charged polybromo compound or polyhalide are a compound with a lower vapor pressure and higher thermodynamic stability.

[0074] As used herein, the term "ammonium bromide complexing agent" refers to any compound, salt, or material that contains a quaternary nitrogen atom, where the quaternary nitrogen atom is not part of an imidazolium, pyridinium, pyrrolidinium, morpholinium, or phosphonium moiety. Examples of ammonium bromide complexing agents include: tetraethylammonium bromide, trimethylpropylammonium bromide, dodecyltrimethylammonium bromide, cetyltriethylammonium bromide, and hexyltrimethylammonium bromide.

[0075] As used herein, the term "imidazolium bromide complexing agent" refers to any compound, salt, or material that contains a quaternary nitrogen atom, where the quaternary nitrogen atom is part of an imidazolium moiety. Examples of imidazolium bromide complexing agents include: 1-ethyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium bromide, 1-ethyl-2,3-dimethylimidazolium bromide, 1-decyl-3-methylimidazolium bromide, 1-butyl-2,3-dimethylimidazolium bromide, 1-methyl-3-octylimidazolium bromide, and 1-methyl-3-hexylimidazolium bromide.

[0076] As used herein, the term "pyridinium bromide complexing agent" refers to any compound, salt, or material that contains a quaternary nitrogen atom, where the quaternary nitrogen atom is part of a pyridinium moiety. Examples of pyridinium bromide complexing agents include: 1-ethyl-2-methylpyridinium bromide, 1-ethyl-3-methylpyridinium bromide, 1-ethyl-4-methylpyridinium bromide, 1-butyl-3-methylpyridinium bromide, 1-butyl 3-methylpyridinium bromide, 1-butyl-4-methylpyridinium bromide, and 1-hexylpyridinium bromide.

[0077] As used herein, the term "pyrrolidinium bromide complexing agent" refers to any compound, salt, or material that contains a quaternary nitrogen atom, where the quaternary nitrogen atom is part of a pyrrolidinium moiety. An example of a pyrrolidinium bromide complexing agent is 1-butyl-1-methylpyrrolidinium bromide.

[0078] As used herein, the term "morpholinium bromide complexing agent" refers to any compound, salt, or material that contains a quaternary nitrogen atom, where the quaternary nitrogen atom is part of a morpholinium moiety. An example of a morpholinium bromide complexing agent is N-ethyl-N-methylmorpholinium bromide.

[0079] As used herein, the term "phosphonium bromide complexing agent" refers to any compound, salt, or material that contains a quaternary phosphonium atom. An example of a phosphonium bromide complexing agent is tetraethylphosphonium bromide.

[0080] As used herein, the term " crown ether" refers to a cyclic compound composed of a ring containing at least three ether groups. Examples of crown ethers include 12-crown-4, 15-crown-5, 18-crown-6, dibenzo-18-crown-6, and diaza-18-crown-6.

[0081] As used herein, an "alkyl" group refers to a saturated aliphatic hydrocarbon group containing 1-20 (e.g., 1-16, 1-12, 1-8, 1-6, or 1-4) carbon atoms. The alkyl group can be straight-chain or branched-chain. Examples of alkyl groups include, but are not limited to, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, 2-ethylhexyl, octyl, nonyl, decyl, dodecyl, and cetyl.

[0082] As used herein, an "aryl" group, when used alone or as part of a larger moiety in "aralkyl", "aryloxyalkyl", or "arylalkoxy", refers to a monocyclic (e.g., phenyl); bicyclic (e.g., indenyl, naphthyl, tetrahydronaphthyl, tetrahydroindenyl); tricyclic (e.g., fluorenyl, tetrahydrofluorenyl, anthryl, or tetrahydroanthryl); or benzo-fused group having 3 rings. For example, benzo-fused groups include those fused to two or more C 4-8A phenyl group with a partially fused carbocyclic ring. The aryl group may optionally be substituted with one or more substituents, including aliphatic (e.g., alkyl, alkenyl, or alkynyl); cycloalkyl; (cycloalkyl)alkyl; heterocycloalkyl; (heterocycloalkyl)alkyl; aryl; heteroaryl; alkoxy; cycloalkoxy; heterocycloalkoxy; aryloxy; heteroaryloxy; aralkyloxy; heteroaralkyloxy; arylcarbonyl; heteroarylcarbonyl; amino; aminoalkyl; nitro; carboxyl; carbonyl (e.g., alkoxycarbonyl, alkylcarbonyl, aminocarbonyl, (alkylamino)alkylaminocarbonyl, arylaminocarbonyl, heteroarylaminocarbonyl; or sulfonylcarbonyl); aralkylcarbonyloxy; sulfonyl (e.g., alkylsulfonyl or aminosulfonyl); sulfinyl (e.g., alkylsulfinyl); thioalkyl (e.g., alkylthioalkyl); cyano; halo; hydroxy; acyl; mercapto; sulfonyloxy; urea; thiourea; aminosulfonyl; sulfonamide; oxo; or carbamoyl. Optionally, the aryl group may be unsubstituted.

[0083] Examples of substituted aryl groups include haloaryl, alkoxycarbonylaryl, alkylaminoalkylaminocarbonylaryl, p,m-dihaloaryl, p-aminop-alkoxycarbonylaryl, m-aminom-cyanoaryl, aminoaryl, alkylcarbonylaminoaryl, cyanoalkylaryl, alkoxyaryl, aminosulfonylaryl, alkylsulfonylaryl, aminoaryl, p-halo-m-aminoaryl, cyanoaryl, hydroxyalkylaryl, alkoxyalkylaryl, hydroxyaryl, carboxyalkylaryl, dialkylaminoalkylaryl, m-heterocycloaliphatic-o-alkylaryl, heteroarylaminocarbonylaryl, nitroalkylaryl, alkylsulfonylaminoalkylaryl, heterocycloaliphaticcarbonylaryl, alkylsulfonylalkylaryl, cyanoalkylaryl, heterocycloaliphaticcarbonylaryl, alkylcarbonylaminoaryl, hydroxyalkylaryl, alkylcarbonylaryl, aminocarbonylaryl, alkylsulfonylaminoaryl, dialkylaminoaryl, alkylaryl, and trihaloalkylaryl.

[0084] As used herein, "aralkyl" means an alkyl group substituted with an aryl group (e.g., C 1-4 alkyl). Both "alkyl" and "aryl" are defined herein. An example of aralkyl is benzyl. "Heteroaralkyl" means an alkyl group substituted with a heteroaryl group.

[0085] As used herein, "cycloalkyl" refers to a saturated carbocyclic mono-, bi-, or tri-, or poly-(fused or bridged) ring of 3 to 10 (e.g., 5 to 10) carbon atoms. Without limitation, examples of monocyclic cycloalkyls include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, etc. Without limitation, examples of bicyclic cycloalkyls include octahydro-indenyl, decahydro-naphthyl, bicyclo[3.2.1]octyl, bicyclo[2.2.2]octyl, bicyclo[3.3.1]nonyl, bicyclo[4.3.2]decyl, bicyclo[2.2.2]octyl, bicyclo[2.2.1]heptyl, bicyclo[3.1.1]heptyl, etc. Without limitation, polycyclic groups include adamantyl, cubyl, norbornyl, etc. The cycloalkyl ring may optionally be substituted at any chemically feasible ring position.

[0086] As used herein, a "heterocycloalkyl" group refers to a 3- to 10-membered mono- or bicyclic (fused or bridged) (e.g., 5- to 10-membered monocyclic or bicyclic) saturated ring structure in which one or more of the ring atoms are heteroatoms (e.g., N, O, S, or combinations thereof). Examples of heterocycloalkyls include optionally substituted piperidinyl, piperazinyl, tetrahydropyranyl, tetrahydrofuranyl, 1,4-dioxolanyl, 1,4-dithianyl, 1,3-dioxolanyl, oxazolidinyl, isoxazolidinyl, morpholinyl, thiomorpholinyl, octahydrobenzofuranyl, octahydrochromenyl, octahydrothiochromenyl, octahydroindolyl, octahydropyridinyl, decahydroquinolinyl, octahydrobenzo[b]thienyl, 2-oxa-bicyclo[2.2.2]octyl, 1-aza-bicyclo[2.2.2]octyl, 3-aza-bicyclo[3.2.1]octyl, 2,6-dioxa-tricyclo[3.3.1.0 3,7 nonyl, tropane. Monocyclic heterocycloalkyls may be fused to a phenyl moiety such as tetrahydroisoquinoline. The heterocycloalkyl ring structure may optionally be substituted at any chemically feasible position on one or more of the rings.

[0087] As used herein, "heteroaryl" refers to a monocyclic, bicyclic, or tricyclic structure having 4 to 15 ring atoms, wherein one or more of the ring atoms are heteroatoms (e.g., N, O, S, or combinations thereof), and wherein one or more of the rings in the bicyclic or tricyclic ring structure are aromatic. Heteroaryl includes benzo-fused ring systems having 2 to 3 rings. For example, benzo-fused groups include those fused to one or two C 4-8A benzo group fused with a heterocyclic moiety (e.g., indolizyl, indolyl, isoindolyl, 3H - indolyl, dihydroindolyl, benzo[b]furanyl, benzo[b]benzothienyl, quinolinyl or isoquinolinyl). Examples of heteroaryl are azetidinyl, pyridinyl, 1H - indazolyl, furanyl, pyrrolyl, thienyl, thiazolyl, oxazolyl, imidazolyl, tetrazolyl, benzofuranyl, isoquinolinyl, benzothiazolyl, xanthene, thioxanthene, phenothiazine, dihydroindole, benzo[1,3]dioxolene, benzo[b]furanyl, benzo[b]benzothienyl, indazolyl, benzimidazolyl, benzothiazolyl, purinyl, cinnolinyl, quinolinyl, quinazolinyl, cinnolinyl, phthalazyl, quinazolinyl, quinoxalinyl, isoquinolinyl, 4H - quinazolinyl, benzo - 1,2,5 - thiadiazolyl or 1,8 - naphthyridinyl. Heteroaryl also includes bipyridine compounds.

[0088] When an element or layer is referred to as "on", "bonded to", "connected to", "attached to", or "coupled to" another element or layer, it can be directly on, bonded, connected, attached, or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as "directly on", "directly bonded to", "directly connected to", "directly attached to", or "directly coupled to" another element or layer, there may be no intervening elements or layers. Other words used to describe the relationship between elements should be interpreted in a similar manner (e.g., "between" versus "directly between", "adjacent" versus "directly adjacent", etc.). As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0089] Terms such as upper, lower, above, below, right, left, etc. may be used to describe the position of various elements relative to other elements. These terms represent the position of the elements in an exemplary configuration. However, it will be apparent to those skilled in the art that, without departing from the present disclosure, the battery frame member can be rotated in space, and thus, these terms should not be used to limit the scope of the present disclosure.

[0090] As used herein, "a plurality of" refers to two or more of the described elements. In some embodiments, a plurality refers to three or more, four or more, or five or more of the described elements.

[0091] As used herein, "chemically compatible" refers to a material that does not interfere with the chemical properties of an electrochemical cell unit in a manner that significantly negatively impacts the performance of the electrochemical cell unit. Chemically compatible materials are chemically compatible with electrolytes (e.g., zinc halide electrolyte, alkaline electrolyte) and anode and cathode materials.

[0092] As used herein, "chemically inert" refers to a material that does not undergo any significant chemical reaction with the electrolyte, anode, or cathode of an electrochemical cell unit.

[0093] As used herein, "during charging", "in the charging process", or "charging" refers to the charging process of an electrochemical cell unit, which occurs when an external current is applied to the electrochemical cell unit (the cathode is the positive terminal and the anode is the negative terminal). The electrochemical cell unit, the electrolyte within the electrochemical cell unit, or the battery can all be said to be "charging".

[0094] "Initial electrolyte" or "uncharged electrolyte" as used herein refers to the electrolyte before charging.

[0095] As used herein, "charged electrolyte" or "charged-up electrolyte" refers to the electrolyte contained within an electrochemical cell unit that has been charged by any amount such that it is no longer in the "initial electrolyte" state.

[0096] As used herein, "charged electrochemical cell unit" or "charged-up electrochemical cell unit" refers to an electrochemical cell unit that has been charged by any amount such that the electrolyte within the electrochemical cell unit is no longer in the "initial electrolyte" state.

[0097] As used herein, in the context of an electrochemical cell unit or the electrolyte contained within an electrochemical cell unit, "significantly charged" or "has received significant charging" means that the electrochemical cell unit or the electrolyte contained within the electrochemical cell unit has been charged to reach an open-circuit potential of at least 1.82 V and a volumetric charge capacity of at least 54 mAh / mL.

[0098] As used herein, the term "mixed polyhalide electrolyte" refers to an aqueous electrolyte containing a mixture of bromide and chloride ions in solution, which forms mixed polyhalides in one aspect when it has received significant charging. As used herein, "mixed polyhalide electrolyte" is an umbrella term encompassing the initial electrolyte and the charged electrolyte in any charging state. However, for clarity, mixed polyhalides are only present in large amounts in the charged electrolyte when it has received significant charging.

[0099] As used herein, "electrolyte density gradient" refers to regions within the electrolyte that have different densities due to different distributions of molecular species with different molecular weights in the charged electrolyte. In one aspect, the electrolyte density gradient is the result of charged electrolytes containing three or more halogen atoms (of the same type or different types) and molecular ions with different molecular weights.

[0100] As used herein, the "Coulombic efficiency" of a secondary battery refers to the ratio of the discharge capacity to the charge capacity within the same charge / discharge cycle.

[0101] As used herein, the "current density distribution" of a battery refers to the variation of the local current density on the surface of an electrode.

[0102] II. Electrochemical Cell Unit and Battery

[0103] In one aspect, the present invention provides an initial electrolyte for a static secondary zinc halide electrochemical cell unit and battery. In another aspect, the present invention provides a static secondary zinc halide battery including the initial electrolyte.

[0104] A. Electrolyte

[0105] The present disclosure provides an initial electrolyte that can be used in non-flow (i.e., static) secondary zinc halide electrochemical cell units and batteries. In these electrochemical cell units and batteries, the zinc halide (e.g., a combination of zinc bromide and zinc chloride) present in the initial electrolyte acts as an electrochemically active material. These electrochemical cell units and batteries are described below.

[0106] The initial electrolyte of the present disclosure is a zinc halide electrolyte that contacts at least one electrode of the electrochemical cell unit. The initial electrolyte is mechanically isolated in each cell unit of the static secondary zinc halide battery. In some embodiments, the electrode is a bipolar electrode, and the initial electrolyte is disposed between the inner surface of the terminal plate, the cathode assembly, the front surface of the bipolar electrode, and the inner surface of the frame (if present).

[0107] For example, in one embodiment of a static zinc bromide secondary battery, positively charged zinc ions and negatively charged halide ions need to be provided at the anode and cathode, respectively.

[0108] In a conventional zinc bromide initial electrolyte with a low chloride concentration, when the electrochemical cell unit or battery is charged, bromide anions near or at the cathode electrode (e.g., the carbon material of the cathode assembly) exposed to the electrolyte are oxidized to bromine. Conversely, during discharge, bromine is reduced to bromide anions.

[0109] Bromine combines with bromide to form polybromide anions near or at the cathode electrode, which can be represented as follows:

[0110]

[0111] In a conventional zinc bromide initial electrolyte with a low chloride concentration, as shown in Equation (1) above, polybromides (e.g., Br 3 - and Br 5 -(with molecular weights of 239.7 and 399.5 g / mol respectively), whose density is much higher than the density of the aqueous electrolyte of about 1.6 g / mL, resulting in a highly uneven electrolyte density gradient, and further leading to a low utilization rate of the electrode surface area in the electrochemical cell unit that has received significant charging. For example, when the polybromide is Br 3 - when, the density of the electrolyte is between about 2.0 g / mL and about 2.2 g / mL. Therefore, historically, one of the greatest challenges faced by static zinc halide batteries is the electrolyte density gradient along the height of the electrochemical cell unit, resulting in uneven electrode utilization and limited energy and power density.

[0112] One way to reduce the electrolyte density gradient along the height of the cell unit is to prepare the initial electrolyte with a mixed chloride / bromide polyhalide having a density lower than that of previously known polybromides. In the initial mixed halide electrolyte containing a high concentration of zinc chloride, the mixed polyhalide (e.g., BrCl 2 - (with a molecular weight of 150.7 g / mol)) can form a mixed polyhalide with a density significantly lower than that of traditional polybromides (e.g., Br 3 - and Br 5 - (with molecular weights of 239.7 and 399.5 g / mol respectively)). Therefore, the density of the formed mixed polyhalide is significantly lower than that of traditional polybromides, thereby reducing the electrolyte density gradient along the height of the cell unit.

[0113] As the molar ratio of zinc chloride to zinc bromide increases, the cathodic reaction can change from the above equation (1) to the following equation (2):

[0114]

[0115] Since equation (2) becomes the main cathodic reaction in the static zinc halide battery (instead of equation (1)), another benefit of solving many historical problems of the static zinc halide battery is that the molecular weight of the final product of equation (2) is significantly lower than that of the final product of equation (1). This results in a mixed polyhalide in the initial electrolyte, and for equation (2), the polyhalide has a lower density and will not sink to the bottom of the cell unit, thereby achieving full utilization of the electrode height. In addition, the voltage of equation (2) is higher than that of equation (1), which makes the battery have higher energy.

[0116] The present disclosure relates to an initial electrolyte that can be particularly used in static zinc halide batteries, where the initial electrolyte is a mixed chloride / bromide electrolyte capable of achieving higher voltages, higher energy and power densities, and lower density mixed polyhalides. This is achieved by formulating a mixed chloride / bromide electrolyte with the correct concentrations and ratios of zinc chloride, zinc bromide, potassium chloride, and potassium bromide, as well as appropriate complexing agents and zinc plating additives. The lower density of the mixed polyhalides of these initial electrolytes is crucial for solving the problem of electrolyte density gradient (stratification) in the height of the electrolyte in traditional static zinc bromide batteries, in which the polybromides formed during charging of the electrolyte are much denser than the initial aqueous electrolyte, resulting in the accumulation of polybromides at the bottom of the battery cell and uneven utilization of the electrode height during discharge.

[0117] Figure 6 Shows the effect of reducing the molar ratio of zinc chloride to zinc bromide in the electrolyte on the formation of polybromides at the bottom of the vial. The shading shown represents the coloring and opacity in the aqueous phase of a given sample, which is caused by the distribution of halide complexes suspended or dissolved in that sample. As Figure 6 shown, reducing the molar ratio of zinc chloride to zinc bromide in the initial electrolyte results in the formation of the above-mentioned dense polybromides at the bottom of the vial. Thus, the initial electrolyte with a higher zinc chloride content forms mixed polyhalides that are buoyant in the electrolyte and do not deposit or accumulate at the bottom of the vial. The implication of this result is that when using an initial electrolyte with a chloride ratio equal to or greater than the bromide ratio, the full height of the static zinc halide battery can be fully utilized, which is a significant improvement over historical static zinc bromide batteries. In some embodiments, the total chloride to total bromide molar ratio in the uncharged or initial electrolyte is between about 1:1 and about 13:1. Preferably, the total chloride to total bromide molar ratio in the uncharged or initial electrolyte is from about 1:1 to about 2:1. Preferably, the total chloride to total bromide molar ratio in the uncharged or initial electrolyte is from about 1.25:1 to about 1.5:1.

[0118] One aspect of the present disclosure provides an uncharged or initial electrolyte for a static secondary zinc halide electrochemical battery cell, comprising: about 5 wt.% to about 30 wt.% of ZnBr 2 ; about 5 wt.% to about 60 wt.% of ZnCl 2 ; about 10 wt.% to about 60 wt.% of H 2 O; and about 0.05 wt.% to about 20 wt.% of one or more quaternary ammonium agents. During the charging of the battery, low molecular weight halide ions (such as bromide and chloride) in the uncharged electrolyte are electrochemically converted into high molecular weight polyhalides (such as Br 3 - 、Br 5- etc.) and high molecular weight mixed polyhalides (such as BrCl 2 - , ClBr 2 - etc. or combinations thereof). The quantity and type of polyhalides and mixed polyhalides formed during charging depend on many uncharged electrolyte variables, including halide concentration, pH value, ratio of chloride to bromide, battery charge capacity, and battery voltage. Once the higher molecular weight polyhalides and mixed polyhalides are electrochemically formed, they typically chemically complex with the quaternary ammonium agent. The complex of the quaternary ammonium agent and the polyhalide or mixed polyhalide can be stored until the battery discharges.

[0119] In some embodiments, when the uncharged electrolyte (having a predetermined ratio of different halides) within the electrochemical cell unit is charged until an open circuit potential of at least 1.82 V and a volumetric charge capacity of at least 54 mAh / mL are reached, a mixed polyhalide is formed. In some embodiments, when the uncharged electrolyte (having a predetermined ratio of different halides) within the electrochemical cell unit is charged until it reaches an open circuit potential greater than 1.82 V and a volumetric charge capacity greater than 54 mAh / mL, a mixed polyhalide is formed. Non-limiting examples of open circuit potentials greater than 1.82 V are 1.83 V - 2.10 V. Non-limiting examples of volumetric charge capacities greater than 54 mAh / mL are 55 mAh / mL - 104 mAh / mL.

[0120] In some embodiments, the mixed polyhalide can be generated by further charging the battery unit after the battery unit has received significant charge. Such mixed polyhalide has the general formula [X (2n+1) Y (2m) - , where X and Y are different from each other and independently are Cl or Br, n is an integer between 0 and 5, and m is an integer between 1 and 5. Non-limiting examples of mixed polyhalides generated during charging include, for example, BrCl 2 - (molecular weight 150.8 g / mol), ClBr 2 - (molecular weight 195.3 g / mol) or combinations thereof.

[0121] In some embodiments, the total molar ratio of chloride ions to bromide ions in the uncharged electrolyte is from about 1:1 to about 13:1. In some embodiments, the total molar ratio of chloride ions to bromide ions in the uncharged electrolyte is from about 1:1 to about 2:1. In yet another embodiment, the total molar ratio of chloride ions to bromide ions in the uncharged electrolyte is from about 1.25:1 to about 1.5:1.

[0122] ​In some embodiments, the charged electrolyte has no density gradient along the electrode length during charging and is independent of the charge capacity. In some embodiments, the charged electrolyte forms a lower density gradient during charging compared to an electrolyte having a total chloride to total bromide molar ratio of less than about 1:1.

[0123] In some embodiments, the density of the initial electrolyte is from about 1.2 to about 2.10 g / cm 3 . In some embodiments, when the electrochemical cell unit containing the initial electrolyte has undergone at least one significant charge, the density of the electrolyte at the end of charging is from about 1.4 to about 2.20 g / cm 3 .

[0124] In some embodiments, the ratio of the density of the initial electrolyte to the density of the charged electrolyte is from about 1.3 to about 1. In one aspect, such a ratio can be obtained when the electrochemical cell unit containing the initial electrolyte has undergone at least one significant charge. In another embodiment, the ratio of the density of the initial electrolyte to the density of the charged electrolyte is from about 1.15 to about 1. In one aspect, such a ratio can be obtained when the electrochemical cell unit containing the initial electrolyte has undergone at least one significant charge.

[0125] In some embodiments, the initial electrolyte of the present disclosure produces a higher Coulombic efficiency in a static secondary zinc iodide electrochemical cell compared to a static secondary zinc bromide electrochemical cell having an initial electrolyte with a total chloride to total bromide molar ratio of less than about 1:1 before charging.

[0126] In some embodiments, the initial electrolyte further includes other components suitable within the scope of the present disclosure. For example, the additional components in the initial electrolytes described in PCT Publication No. WO 2016 / 057477, filed Oct. 6, 2015, PCT Publication No. WO2017 / 172878, filed Mar. 29, 2017, U.S. Patent No. 10276872, filed Mar. 29, 2016, and U.S. Patent Application Publication No. 2011 / 0253553A1, filed Mar. 21, 2011, can be used within the scope of the present disclosure, all of which are incorporated herein by reference.

[0127] In some embodiments, the initial electrolyte further contains from about 0.5 wt.% to about 15 wt.% KBr and from about 0.5 wt.% to about 15 wt.% KCl.

[0128] In some embodiments, the initial electrolyte further comprises from about 0.5 wt.% to about 15 wt.% of KCl. In some embodiments, the initial electrolyte does not include KBr. In some embodiments, the initial electrolyte comprises about 0 wt.% of KBr.

[0129] The initial electrolyte includes one or more chloride ion sources. Non-limiting examples of one or more chloride ion sources include, for example, ZnCl 2 , KCl, NH 4 Cl, LiCl, CuCl 2 , CaCl 2 , FeCl 3 , SbCl 3 , CrCl 3 , NaCl, BiCl 3 , quaternary ammonium salts having chloride anions.

[0130] The initial electrolyte includes one or more bromide ion sources. Non-limiting examples of one or more bromide ion sources include, for example, ZnBr 2 , KBr, NH 4 Br, LiBr, CuBr 2 , CaBr 2 , NaBr, AgBr, AlBr 3 , quaternary ammonium salts having bromide anions.

[0131] In some embodiments, the initial electrolyte includes ZnBr 2 , ZnCl 2 , KCl and KBr. In some embodiments, the total molar ratio of chloride ions to bromide ions in the initial electrolyte is from about 1:1 to about 13:1. In another embodiment, the total molar ratio of chloride ions to bromide ions in the initial electrolyte is about 1:1 to 2:1. In still another embodiment, the total molar ratio of chloride ions to bromide ions in the initial electrolyte is from about 1.25:1 to about 1.5:1.

[0132] In some embodiments, the initial electrolyte includes from about 0.05 wt.% to about 20 wt.% of one or more quaternary ammonium agents. Each quaternary ammonium agent is independently selected from quaternary ammonium agents having the formula N + (R 1 )(R 2 )(R 3 )(R 4 )X - , wherein R 1 is hydrogen or an alkyl group, and R 2 , R 3 and R 4 are each independently an alkyl group the same as or different from R 1 , and X- is chlorine or bromine.

[0133] In some embodiments, one or more quaternary ammonium agents include a first quaternary ammonium agent. In some embodiments, the first quaternary ammonium agent is selected from tetra-C 1-6 alkylammonium chloride or tetra-C 1-6 alkylammonium bromide. In some embodiments, the first quaternary ammonium agent is tetramethylammonium chloride, tetraethylammonium chloride, tetrapropylammonium chloride, tetrabutylammonium chloride, tetramethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, or tetrabutylammonium bromide.

[0134] In some embodiments, one or more quaternary ammonium agents further include a second quaternary ammonium agent. In some embodiments, the second quaternary ammonium agent has the formula N + (R 1 )(R 2 )(R 3 )(R 4 )X - , where R 1 is hydrogen or an alkyl group, and R 2 , R 3 , and R 4 are each independently an alkyl group the same as or different from R 1 , and X - is chlorine or bromine.

[0135] In some embodiments, the second quaternary ammonium agent is the chloride or bromide of trimethylethylammonium, trimethylpropylammonium, tripropylbutylammonium, triethylmethylammonium, triethylpropylammonium, triethylbutylammonium, tripropylmethylammonium, tripropylethylammonium, or tripropylbutylamine.

[0136] In some embodiments, the initial electrolyte further contains from about 0.1 wt.% to about 3 wt.% of a diol, where the diol is ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, hexanediol, or any combination thereof. In one embodiment, the diol is neopentyl glycol.

[0137] In some embodiments, the initial electrolyte further contains from about 0.1 wt.% to about 3 wt.% of a diglyme, where the diglyme is monoglyme, diglyme, triglyme, tetraglyme, pentaglyme, hexaglyme, or any combination thereof. In one embodiment, the diglyme is tetraglyme. In some embodiments, the diglyme is dipropylene glycol dimethyl ether (DMM).

[0138] In some embodiments, the initial electrolyte further comprises less than 0.1 wt.% of one or more additives selected from Sn, In, Ga, Al, Tl, Bi, Pb, Sb, Ag, Mn, Fe, Cr, Sc, Cu, Al, Ru, Sr, or any combination thereof. In some embodiments, the initial electrolyte further comprises up to 1 wt.% of one or more additives selected from Sn, In, Ga, Al, Tl, Bi, Pb, Sb, Ag, Mn, Fe, Cr, Sc, Cu, Al, Ru, Sr, or any combination thereof.

[0139] In some embodiments, the initial electrolyte comprises: about 5 wt.% to about 40 wt.% of ZnBr 2 ; about 5 wt.% to about 60 wt.% of ZnCl 2 ; about 10 wt.% to about 60 wt.% of H 2 O; about 1 wt.% to about 10 wt.% of KBr; about 1 wt.% to about 20 wt.% of KCl; and about 0.05 wt.% to about 20 wt.% of one or more quaternary ammonium agents.

[0140] In some embodiments, the initial electrolyte comprises: about 5 wt.% to about 40 wt.% of ZnBr 2 ; about 5 wt.% to about 60 wt.% of ZnCl 2 ; about 10 wt.% to about 60 wt.% of H 2 O; about 1 wt.% to about 20 wt.% of KCl; and about 0.05 wt.% to about 20 wt.% of one or more quaternary ammonium agents.

[0141] In some embodiments, the initial electrolyte further comprises about 0.1 wt.% to about 3 wt.% of DME-PEG. In some embodiments, the initial electrolyte comprises DME-PEG having a number average molecular weight of about 1000 amu, DME-PEG having a number average molecular weight of about 2000 amu, or a combination thereof.

[0142] In some embodiments, the initial electrolyte further comprises about 0.1 wt.% to about 3 wt.% of PEG. In some embodiments, the initial electrolyte comprises PEG having a number average molecular weight of about 1000 amu, PEG having a number average molecular weight of about 3500 amu, or a combination thereof.

[0143] In some embodiments, the initial electrolyte does not contain DME-PEG.

[0144] In some embodiments, the initial electrolyte does not contain PEG.

[0145] Table 1 - Part 1 and Table 1 - Part 2 provide non - limiting examples of initial electrolytes that will produce the hybrid polyhalides of the present disclosure when an electrochemical cell unit containing the initial electrolyte has undergone at least significant charging.

[0146] Table 1 - Part 1

[0147] Component (wt.%) 1 2 3 4 5 6 7 8 9 Zinc bromide 19.5 11.5 4 7.6 14 16.7 22 17.5 14.5 Zinc chloride 24 28 33 30 26 24 19.5 19 17 Potassium bromide 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 Potassium chloride 9.4 9.4 9.4 9.4 9.4 9.4 9.4 9.4 9.4 Water 30 34 36.5 35.88 33.48 32.78 31.98 37.78 41.98 Triethylmethylammonium chloride 7 7 7 7 7 7 7 7 7 DME-PEG 2K 0.62 0.62 0.62 0.62 0.62 0.62 0.62 0.62 0.62 DME-PEG 1K 0.22 0.22 0.22 0.22 0.22 0.22 0.22 0.22 0.22 Neopentyl glycol 0.87 0.87 0.87 0.87 0.87 0.87 0.87 0.87 0.87 Tetraethylene glycol dimethyl ether 0.91 0.91 0.91 0.91 0.91 0.91 0.91 0.91 0.91

[0148] Table 1 - Part 2

[0149] Component (wt.%) 10 11 12 Zinc bromide 23.80 23.80 23.80 Zinc chloride 19.70 19.70 19.70 Potassium bromide --- --- --- Potassium chloride 14.10 14.10 14.10 Water 32.78 32.78 32.78 Triethylmethylammonium chloride 7.00 7.00 7.00 DME-PEG 2K 0.62 --- 0.62 DME-PEG 1K 0.22 --- 0.22 PEG 3350 --- 0.62 --- PEG 1000 --- 0.22 --- Neopentyl glycol 0.87 0.87 0.87 Tetraethylene glycol dimethyl ether 0.91 0.91 --- Dipropylene glycol dimethyl ether --- --- 0.91

[0150] It has also been found that an initial electrolyte having a hybrid polyhalide according to an embodiment of the present disclosure advantageously improves the coulombic efficiency of a static secondary zinc - halide electrochemical cell. In some embodiments, the coulombic efficiency of a static secondary zinc - halide electrochemical cell having a hybrid polyhalide initial electrolyte according to an embodiment of the present disclosure is increased by about 3% to about 8% compared to a comparable static secondary zinc - bromide cell having an initial zinc - bromide electrolyte that forms polybromides upon charging in the electrolyte rather than the hybrid polyhalides as described in the present disclosure. The following examples demonstrate this.

[0151] An initial electrolyte having a hybrid polyhalide according to an embodiment of the present disclosure can advantageously improve the current density distribution over the height of the electrodes of a static secondary zinc - halide electrochemical cell.

[0152] The inventors of the present disclosure have also unexpectedly found that an initial electrolyte produced at a pH of about 3 can achieve these results. Prior to the present invention, it was thought that the BrCl 2 - reaction only occurs in extremely low - pH electrolytes with a pH of about 1 or lower, or in extremely concentrated electrolytes containing a small amount of free water.

[0153] The chloride and bromide concentrations in the initial electrolyte can be determined as follows: The cell unit can be charged using the protocol described in Example 3 below. Then the cell unit can be removed from the electrical connection and then opened to remove an aliquot of the electrolyte from the cell unit. An aliquot (e.g., 10 mL) can be obtained from the top of the cell unit and an aliquot (e.g., 10 mL) can be obtained from the bottom of the cell unit. The bromide and chloride concentrations of each aliquot can be analyzed and determined to chemically demonstrate the distribution of bromide and chloride at the top and bottom in the various electrolytes.

[0154] The open - circuit potential of the cell unit can be determined as follows: The cell unit can be charged using the protocol described in Example 3 below. The open - circuit potential of the cell unit can be measured after charging. This open - circuit potential may vary depending on the final composition of the hybrid polyhalide after charging.

[0155] The ultraviolet-visible spectrum of the electrolyte after charging can be determined as follows: The battery cell can be charged using the protocol described in Example 3 below. The battery cell can be removed from the electrical connection and then opened to remove aliquots of the electrolyte from the battery cell. Aliquots (e.g., 10 mL) can be obtained from the top of the battery cell, aliquots (e.g., 10 mL) can be obtained from the bottom of the battery cell, and each aliquot can be subjected to ultraviolet-visible spectroscopy. The type of mixed polyhalide formed may have a different ultraviolet-visible spectrum because the color of the mixed polyhalide varies depending on the bromide and chloride in the mixed polyhalide, as Figure 6 shown.

[0156] The electrolyte density gradient can be determined as follows: The battery cell can be charged using the protocol described in Example 3 below. Then the battery cell can be removed from the electrical connection and then opened to remove aliquots of the electrolyte from the battery cell. Aliquots (e.g., 10 mL) can be obtained from the top of the battery cell, aliquots (e.g., 10 mL) can be obtained from the bottom of the battery cell, and each aliquot can be subjected to electrolyte density measurement.

[0157] B. Electrochemical Cell

[0158] On the other hand, the present invention provides a secondary zinc halide battery comprising the above-described initial electrolyte. The secondary zinc halide battery is a static (non-flowing) secondary zinc halide battery. Static battery structures are well known to those skilled in the art. In the following aspects, the battery is described as a static bipolar electrochemical cell. Those skilled in the art know alternative battery structures, such as monopolar (or single-pole) batteries. Therefore, alternative static battery structures are not discussed in detail herein.

[0159] B. Static Bipolar Electrochemical Cell

[0160] Reference Figure 2 and Figure 3 , embodiments of the static (non-flowing) bipolar zinc halide secondary electrochemical cell 500 of the present disclosure include at least one bipolar electrochemical cell unit and two terminal electrochemical cell units. In some embodiments, the bipolar electrochemical cell includes from about 10 to 50 bipolar electrochemical cell units in series and two terminal electrochemical cell units. For example, in one embodiment, the bipolar electrochemical cell includes 26 bipolar electrochemical cell units in series and two terminal electrochemical cell units. In another embodiment, the bipolar electrochemical cell includes 38 bipolar electrochemical cell units in series and two terminal electrochemical cell units.

[0161] B.i. Static Bipolar Electrochemical Cell

[0162] The at least one bipolar electrochemical cell unit includes a bipolar electrode 502, a cell frame member 514, and a zinc halide electrolyte. The terminal electrochemical cell unit includes a bipolar electrode 502, a cell frame member 514, a terminal assembly 504, a terminal end plate 505, and a zinc halide electrolyte.

[0163] Figure 1 A disassembled view of the electrochemical cell unit 100 of the present disclosure is shown, which includes a bipolar electrode 102, a cell frame member 114, a terminal assembly 104, and the aforementioned initial zinc halide electrolyte.

[0164] 1. Bipolar electrode

[0165] Reference Figure 3 and Figure 4 , the bipolar electrode 502 of the present disclosure includes a bipolar electrode plate 702, which has an anode surface on one side of the bipolar electrode plate and a cathode surface on the other side of the bipolar electrode plate opposite to the anode surface. On the cathode surface of the bipolar electrode plate 702, a carbon material 624 is adhered to the surface of the bipolar electrode plate 702 using an adhesive layer 711 such that the carbon material 624 is at least electrically connected to the surface of the bipolar electrode plate 702. The structure of the bipolar electrode 502 is described by reference to the disassembled view of the terminal assembly 504 in Figure 4 because the structure of the bipolar electrode 502 is the same as the structure of the bipolar electrode in the terminal assembly 504.

[0166] The bipolar electrode 502 of the present disclosure is configured to electroplate zinc metal on the anode electrode surface and generate halide or mixed halide species reversibly chelated in the carbon material during charging of the electrochemical cell unit. Conversely, these electrodes are configured to oxidize the electroplated zinc metal during discharging of the electrochemical cell unit to generate Zn 2+ cations and reduce the halide or mixed halide species to their corresponding anions.

[0167] a. Bipolar electrode plate

[0168] The bipolar electrode plate 702 includes a conductive coating or film that is relatively inert to the zinc halide electrolyte used in the electrochemical cell. In some embodiments, the coating or film covers a portion of the surface of the bipolar electrode plate 702. In some embodiments, the bipolar electrode plate 702 includes titanium, titanium oxide, TiC, TiN, or graphite. Optionally, the bipolar electrode plate 702 is a plastic material that has been made conductive by incorporating a conductive filler into the plastic. In some embodiments, the bipolar electrode plate 702 includes a titanium material (e.g., titanium or titanium oxide). In other embodiments, the bipolar electrode plate 702 includes a titanium material coated with a titanium carbide material. In these embodiments, at least a portion of the surface of the bipolar electrode plate 702 is coated with the titanium carbide material. In some embodiments, the bipolar electrode plate 702 includes a conductive carbon material (e.g., a graphite plate). In some cases, the bipolar electrode plate 702 includes a graphite plate coated with a titanium carbide material. In these embodiments, at least a portion of the surface of the bipolar electrode plate 702 is coated with the titanium carbide material. In some embodiments, the bipolar electrode plate 702 includes a conductive plastic. Any suitable conductive plastic can be used within the scope of the present invention. Conductive plastics are well known to those skilled in the art and are not described in detail herein. Such conductive plastic materials can include a base resin polymer having carbon black, graphite, fumed silica, or a combination thereof. For example, the conductive plastic described in U.S. Patent No. 4,169,816, filed Mar. 6, 1978, can be used within the scope of the present disclosure, which is incorporated herein by reference.

[0169] In some embodiments, the bipolar electrode plate can be substantially rectangular, with one dimension being significantly larger than the other dimension to convey a rectangular appearance. In Figure 3 the X-Y-Z coordinate space shown, the width dimension of the terminal assembly 504 is in the X direction and is the larger dimension relative to Y. The height dimension of the terminal assembly 504 is in the Y direction and is the shorter dimension compared to the X dimension, such that the illustrated terminal assembly 504 and the disassembled battery have a rectangular appearance. The Z direction represents the depth (i.e., thickness) of the illustrated battery components. As Figure 3 and Figure 4 shown, the orientation of the bipolar electrode plate and the orientation of the carbon material are complementary to the orientation of the terminal assembly 504, such that the width and height of the bipolar electrode plate and the width and height of the carbon material respectively share approximately the same orientation as Figure 7 the width and height of the illustrated terminal assembly 504.

[0170] The bipolar electrode plate can be formed by stamping or other suitable processes. Optionally, a portion of the surface of the bipolar electrode plate 702 can undergo surface treatment (e.g., coating, etc.) to enhance the electrochemical properties of the cell or battery. The inner surface of the bipolar electrode plate can include an electrochemically active region that is associated with or defined by the formation of a zinc metal layer during charging of the cell or battery. In some embodiments, the inner surface of the electrode plate can be sandblasted or otherwise treated within the electrochemically active region. In other embodiments, the outer surface can also be sandblasted within the electrochemically active region associated with the area surrounded by the cathode assembly.

[0171] For example, in some embodiments, at least a portion of the inner surface, at least a portion of the outer surface, or at least a portion of both surfaces is treated (e.g., sandblasted) to obtain a rough surface. In some cases, at least a portion of the inner surface of the bipolar electrode plate is treated (e.g., sandblasted) to obtain a rough surface. In some cases, the inner surface region treated to obtain a rough surface is substantially defined by the perimeter of the cathode assembly fixed to the outer surface of the electrode plate.

[0172] b. Cathode assembly

[0173] The electrochemical cell of the present disclosure includes a cathode assembly located on the cathode surface of the bipolar electrode plate 702. In some embodiments, the cathode assembly includes at least one carbon material 624 and an adhesive layer 711 that electrically connects the carbon material 624 to the bipolar electrode plate 702. The carbon material is positioned on a coating material on the surface (e.g., cathode surface) of the bipolar electrode plate 702. In other embodiments, the cathode assembly includes a cathode cage that electrically connects the carbon material 624 to the cathode surface of the bipolar electrode plate 702. The cathode cage described in U.S. Provisional Application No. 63 / 168,699, filed Mar. 31, 2021, can be used within the scope of the present disclosure, and this application is incorporated herein by reference.

[0174] i. Carbon material

[0175] The carbon material 624 is in electrical communication with the surface of the bipolar electrode plate 702 and is adhered to the bipolar electrode plate 702 using the adhesive layer 711. The carbon material suitable for the electrochemical cell of the present disclosure can include any carbon material that can reversibly absorb aqueous bromine species (e.g., aqueous bromine or aqueous bromide) and is substantially chemically inert in the presence of an electrolyte. In some embodiments, the carbon material includes carbon black or other furnace carbon. Suitable carbon black materials include, but are not limited to, Cabot Other matte black mixtures of XC72R, Akzo Nobel Ketjenblack EC600JD, and conductive furnace black. In some embodiments, the carbon material may also include other components, including but not limited to PTFE binder and deionized water. For example, the carbon material has a water content of less than 50 wt.% (e.g., from about 0.01 wt.% to about 30 wt.%) based on the weight of the carbon material. In some embodiments, the carbon material includes PTFE (e.g., from about 0.5 wt.% to about 5 wt.% based on the weight of the carbon material).

[0176] In some embodiments, the carbon material may be in the form of one or more thin rectangular blocks. In some embodiments, the carbon material may include a single solid block. In other embodiments, the carbon material may include one to five, one to three, or one to two solid blocks of carbon black.

[0177] In some embodiments, the carbon material may be composed of woven carbon fibers or non-woven carbon felt material.

[0178] In some embodiments, the carbon material may be substantially rectangular, where one dimension is significantly larger than the other to convey a rectangular appearance. In Figure 3 and Figure 4 the X-Y-Z coordinate space shown, the width dimension of the carbon material 624 is in the X direction (shown as "W" in Figure 4 ), and it is the larger dimension relative to Y, which gives the article a rectangular appearance. The height dimension of the carbon material 624 is in the Y direction (shown as "H" in Figure 4 and Figure 10 ), and it is the shorter dimension relative to the width dimension. The orientation of the bipolar electrochemical cell 500 and the orientation of the carbon material 624 are complementary such that the width and height of the bipolar electrochemical cell 500 respectively share approximately the same orientation as the width and height of the carbon material 624. A battery having such a carbon material embodiment as described in U.S. Application No. 17 / 410,552, filed on August 24, 2021, can be used within the scope of the present disclosure, which is incorporated herein by reference.

[0179] 2. Terminal Assembly

[0180] Referring to Figure 4, the terminal assembly 504 of the present disclosure includes: a terminal connector 708; a conductive flat plate 704 having a conductive perimeter 706; an electrically insulating tape member 710; and a terminal bipolar electrode plate 702. The conductive flat plate 704, the terminal bipolar electrode plate 702, and the electrically insulating tape member 710 each have inner and outer surfaces that are at least substantially parallel to each other, wherein the outer surface of the conductive flat plate 704 is joined to the terminal connector 708, the inner surface of the conductive flat plate 704 is joined to the outer surface of the terminal bipolar electrode plate 702, wherein the electrically insulating tape member 710 is disposed between the inner surface of the conductive flat plate 704 and the outer surface of the bipolar electrode plate 702 such that the electrically insulating tape member 710 does not cover the entire inner surface area of the conductive flat plate 704, and wherein the conductive perimeter 706 enables bidirectional uniform current to flow through the conductive flat plate 704 between the terminal connector 708 and the terminal bipolar electrode plate 702.

[0181] Since the insulating tape member 710 does not cover the entire surface of the conductive flat plate 704, it allows the conductive perimeter 706 to be in electrical communication with the terminal bipolar electrode plate 702. In some embodiments, the size of the insulating tape member 710 is smaller than the size of the conductive flat plate 704. The terminal connector 708 of the bipolar electrochemical cell is connected for electrical communication with the conductive flat plate 304. In some embodiments, the outer surface of the conductive flat plate 704 is joined to the terminal connector 708. In some embodiments, the terminal connector 708 includes any conductive material. In one embodiment, the terminal connection includes brass (e.g., the terminal connector is a tab assembly that is in electrical communication or contact with the terminal perimeter).

[0182] The terminal bipolar electrode plate 702 of the terminal assembly 504 has inner and outer surfaces that are at least substantially parallel to the inner and outer surfaces of the conductive flat plate 704 and the electrically insulating tape member 710. The terminal bipolar electrode plate 702 can include, but is not limited to, a titanium material coated with a titanium carbide material, through-holes, a rough inner surface, etc. The conductive perimeter 706 of the flat plate 704 having the electrically insulating tape member 710 is joined to the terminal bipolar electrode plate 702 such that the conductive perimeter 706 is centered generally about the electrochemically active region of the terminal bipolar electrode plate 702. In some embodiments, the electrochemically active region corresponds to the region that extends between the inner and outer surfaces of the terminal bipolar electrode plate 702 that is chemically or electrically in communication with an adjacent bipolar electrode plate during charging and discharging cycles of an electrochemical cell. In these embodiments, the electrochemically active region of the terminal bipolar electrode plate 702 associated with the negative terminal of the battery corresponds to the region surrounded by or defined by the cathode assembly disposed on the inner surface of the terminal bipolar electrode plate 702 (e.g., the terminal cathode electrode plate). The electrochemically active region of the terminal bipolar electrode plate 702 associated with the positive terminal of the battery can correspond to the region on its inner surface that is opposite the cathode assembly disposed on the front surface of an adjacent bipolar electrode plate and that forms a zinc metal layer (the terminal anode assembly) during battery charging. In some embodiments, at least a portion (e.g., at least the chemically active region) of the surface of the terminal bipolar electrode plate 702 of the terminal anode assembly is a rough surface.

[0183] Figure 4 A exploded view of a terminal assembly for a Figure 2 battery is provided, which shows the cathode carbon material 624, the adhesive layer 711, the terminal bipolar electrode plate 702, the electrically insulating tape member 710, the conductive flat plate 704, the conductive perimeter 306, and the terminal connector 708.

[0184] In some embodiments, the conductive perimeter 706 formed by welding is centered within the electrochemically active region of the terminal bipolar electrode plate 702. In some embodiments, the conductive perimeter 706 is substantially rectangular, substantially circular, or substantially elliptical. In some embodiments, the conductive perimeter 706 is substantially rectangular.

[0185] In some embodiments, the conductive flat plate 704 having the electrically insulating tape member 710 is centered within the electrochemically active region of the terminal bipolar electrode plate 702.

[0186] In some embodiments, the surface of the electrically insulating tape member is joined to the surface of the conductive flat plate by welding or an adhesive. In some embodiments, the adhesive is conductive.

[0187] The conductive flat plate described herein is larger than prior art current collectors and, thus, provides more contact points and better current density distribution. This reduces manufacturing costs.

[0188] In some embodiments, the terminal assembly is a terminal cathode assembly, wherein the terminal cathode assembly includes a terminal bipolar electrode plate 702 having an electrochemically active region, a conductive flat plate 704 having an electrically insulating tape member 710 disposed on a surface of the terminal bipolar electrode plate 702 and substantially centered within the electrochemically active region, and a cathode assembly such as any of the cathode assemblies described herein disposed on an inner surface of the terminal bipolar electrode plate 702.

[0189] In some embodiments, the terminal assembly is a terminal anode assembly, wherein the terminal anode assembly includes a terminal bipolar electrode plate 702 having an electrochemically active region, a conductive flat plate 704 having an electrically insulating tape member 710 centered within the electrochemically active region, and wherein the terminal anode assembly lacks a cathode assembly.

[0190] In some embodiments, a conductive perimeter 706 of the conductive flat plate 704 having the electrically insulating tape member 710 is joined to a surface of the terminal bipolar electrode plate 702 by welding or an adhesive. In some cases, the adhesive is conductive. Non-limiting examples of suitable conductive adhesives include graphite-filled adhesives (e.g., graphite-filled epoxy, graphite-filled silicone, graphite-filled elastomer, or any combination thereof), nickel-filled adhesives (such as nickel-filled epoxy), silver-filled adhesives (e.g., silver-filled epoxy), copper-filled adhesives (e.g., copper-filled epoxy), any combination thereof, and the like.

[0191] In some embodiments, the conductive flat plate 704 having the electrically insulating tape member 710 is composed of at least one of a copper alloy, a copper / titanium cladding, aluminum, titanium, and a conductive ceramic.

[0192] In some embodiments, at least one of the conductive flat plate 704 having the electrically insulating tape member 710 or the terminal bipolar electrode plate 702 includes titanium. In some embodiments, at least one of the conductive flat plate 704 having the electrically insulating tape member 710 or the terminal bipolar electrode plate 702 includes a titanium material coated with a titanium carbide material.

[0193] In some embodiments, an inner surface of at least one of the conductive flat plates 704 having the electrically insulating tape member 710 includes copper.

[0194] In some embodiments, an outer surface of at least one of the conductive flat plates 704 having the electrically insulating tape member 710 includes at least one of copper, titanium, and a conductive ceramic.

[0195] In some embodiments, the conductive flat plate 704 having the electrically insulating tape member 710 includes a first metal, and the terminal bipolar electrode plate 702 includes a second metal.

[0196] In some embodiments, the electrical insulation tape member 710 can be composed of any adhesive material that is essentially electrically insulating. Non-limiting examples of the electrical insulation tape member 710 include, for example, Kapton TM , Mylar TM , polyimide, polyethylene, nylon, polytetrafluoroethylene, neoprene, or any other electrically insulating polymer.

[0197] 3. Battery frame member

[0198] In some embodiments, the battery of the present disclosure includes a battery frame member 514 that is interposed between two adjacent bipolar electrodes or between the bipolar electrode 502 and the terminal assembly 504 (e.g., a terminal anode assembly or a terminal cathode assembly).

[0199] The width and height of the battery frame member 514 are complementarily positioned with respect to the width "W" and height "H" of the carbon material 624, respectively. The width of the battery frame member 514 is the dimension along (parallel to) the bottom of the battery frame member, where the gas channel 801 is located at the top of the battery frame member (as Figure 5 shown). In Figure 3 the X-Y-Z coordinate space shown, the width dimension of the battery frame member 514 is in the X direction, while the height dimension of the battery frame member 514 is in the Y direction. The depth of the battery frame member 514 is in the Z direction and is the value of the dimension perpendicular to the height and width of the battery frame member 514 (shown as "D" in Figure 3 ). In some embodiments, the frame member 514 is substantially rectangular, with one dimension significantly larger than the other to convey a rectangular appearance.

[0200] In one embodiment, as Figure 5 shown, the battery frame member 514 has an outer peripheral edge and an inner peripheral edge that defines an open inner region. In some embodiments, the battery frame member 514 is configured such that the open inner region is generally centered around the center of the electrochemically active region of the terminal bipolar electrode plate 702 received by the battery frame member 514 and / or the center of the cathode assembly disposed on the terminal bipolar electrode plate 702. In some embodiments, the outer periphery of the battery frame member 514 defines the outer surface of the battery.

[0201] In some embodiments, the battery frame member 514 includes a first side that faces and holds the first (terminal) bipolar electrode plate 702, and a second side that is disposed on the opposite side of the battery frame member 514 relative to the first side and faces and holds a second bipolar electrode plate. The second electrode plate is adjacent to and parallel to the first electrode plate in the battery. The first electrode plate, the second electrode plate, and the terminal electrode plate(s) may be configured to have substantially the same size and shape. In some embodiments, the battery frame member 514 contacts the anode bipolar electrode plate on one side and contacts the cathode bipolar electrode plate of an adjacent bipolar cell on the other side.

[0202] In some embodiments, the battery frame member 514 includes a sealing member 516 that extends around the inner peripheral edge of the entire frame ( Figure 5 ). In some embodiments, the battery frame member 514 includes a first sealing member 516 disposed along a first inner peripheral edge. In some embodiments, the first sealing member is an O-ring. In some embodiments, the first sealing member 516 is a gasket. In some embodiments, each inner peripheral edge is configured to receive the sealing member 516 disposed therein, and when the electrochemical cell is assembled, the sealing member 516 forms a substantially leak-free seal when the seal is compressed between the corresponding bipolar electrode plate or terminal electrode plate and the battery frame member 514 to provide a sealing interface between the bipolar electrode plate or end plate and the battery frame member 514. The sealing members cooperate to retain the electrolyte between the opposing bipolar electrode plates and the battery frame member 514, or between the bipolar electrode plates, the terminal electrode plates, and the frame member 514. In some embodiments, the sealing member 516 is overmolded onto the frame member 514. In some embodiments, the sealing member 516 is applied to the frame member 514 using a form in place liquid curing process. In some embodiments, the sealing member 516 extends above the depth of the frame member 514 and is compressed during assembly.

[0203] In some embodiments, the battery frame member 514 includes a groove in a bottom portion of the battery frame member 514 to prevent abnormal voltage during cycling. In some embodiments, the groove includes a groove shelf 406 and a void space 407 below the groove shelf 406. In some embodiments, the cathode carbon material 624 rests on the groove shelf 406. It has been found that the presence of the groove shelf and the void below the groove shelf prevents abnormal voltage during cycling. In some embodiments, there is no void 407 below the groove shelf 406 and the groove shelf 406 extends to the bottom of the battery frame member 514. In some embodiments, the groove shelf 406 on which the cathode carbon material 624 rests can be between 0.5 and 5 cm high, including the void space 407 below the groove shelf 406, and can be between 3 and 10 mm wide along the entire bottom of the width of the battery frame member 514.

[0204] In some embodiments, the battery frame member includes a first frame member and a second frame member. In some embodiments, the first frame member and the second frame member are horizontally stacked and vertically oriented, wherein a first outer edge of the first frame member is substantially coplanar with a second outer edge of the second frame member.

[0205] In some embodiments of the battery, each battery frame member 514 is plastically welded to an adjacent frame member 514 using a weld 805 around the perimeter of the battery frame member 514.

[0206] In some embodiments, the battery frame member 514 includes a gas channel 801 on top of the battery frame member directly above the vent hole 802. The vent hole 802 allows gas to escape into the gas channel 801. In some embodiments, the gas channel 801 associated with each battery frame member 514 is covered so that no lid needs to be placed on the gas channel 801 after the battery frame members are assembled together. As described herein, the gas channel 801 is a battery headspace for gas from the electrochemical cell units in the battery frame member 514. In some embodiments, the frame member 514 is filled with electrolyte through a fill hole in the gas channel (as shown, a plug 809 is inserted therein), and the gas channel 801 is also in communication with the vent hole 802. Once the battery is filled with electrolyte, the plug 809 is inserted into the fill hole to seal the gas channel 801 from the environment. In those embodiments where the fill hole and the vent hole 802 are not the same, the vent hole remains open to the gas channel during battery operation. In other embodiments, electrolyte is added to the battery through the vent hole.

[0207] In some embodiments, a liquid diversion system is present in the top of the cell frame member 514 directly below the vent hole 802, which allows gas to escape into the gas channel 801. Although the gas channel 801 provides gas communication throughout the cell 500, the liquid diversion system prevents liquid from entering the gas channel 801 through a series of components. In some embodiments, the liquid diversion system includes a main diverter 803 having two partial blocking walls 804 and a plurality of auxiliary blocking walls 808 to ensure that liquid is always directed back into the open interior region within the cell frame member 514. In some embodiments, the main diverter 803 consists of a horizontal plastic protrusion having end pieces facing downward at an angle within the range of 30 degrees to 60 degrees. In some embodiments, the auxiliary blocking walls ensure that a minimal amount of fluid will reach the main diverter. In some embodiments, the auxiliary blocking walls 808 are designed herein to alternate top-down and bottom-up relative to the frame member 514 in order to disrupt any internal electrolyte waves caused by severe shaking or tilting. One advantage of the liquid diversion system is to improve the quality of the cell by keeping the electrolyte contained within the frame member during transportation.

[0208] Each cell frame member 514 can be formed of flame-retardant polypropylene fiber, high-density polyethylene, polyphenylene oxide, or polyphenylene ether. Each cell frame member 514 can receive two adjacent bipolar electrode plates or a bipolar electrode plate and a terminal electrode plate. Each cell frame member 514 can also accommodate an aqueous electrolyte solution (e.g., a zinc halide electrolyte or a zinc bromide electrolyte) received via the vent hole 802.

[0209] 4. Compression Plate

[0210] In some embodiments, an electrochemical cell unit or cell includes a pair of compression plates located at the ends of the electrochemical cell unit or cell. Suitable compression plates can be, for example, the compression plates described in PCT Publication No. WO2019 / 108513, filed on November 27, 2018, which is incorporated herein by reference and can be used within the scope of the present disclosure.

[0211] III. Examples

[0212] Example 1: Preparation of Hybrid Polyhalide Electrolytes and Control Electrolytes

[0213] An initial electrolyte aqueous solution of a mixed halide was prepared containing zinc bromide in a concentration range of 0.2 M - 3.0 M, zinc chloride in a concentration range of 1.0 M - 4.0 M, a potassium halide salt in a concentration range of 1.0 - 3.5 M, and a tetraalkylammonium salt in a concentration range of 0.5 - 1.0 M. An initial electrolyte aqueous solution having the same composition as above but without zinc chloride was also prepared and used as a control electrolyte solution.

[0214] Example 2: Comparison of Voltages Generated Using a Mixed Polyhalide Electrolyte and a Control Electrolyte

[0215] A test battery cell was assembled using a titanium metal current collector with a titanium carbide coating formed into a plate. The anode plate and the cathode plate were placed in a slotted high-density polyethylene battery cell that held the plates in a parallel configuration, 14 mm apart. Before battery cell assembly, a carbon felt was attached to the cathode titanium current collector using 0.8 ml of a conductive acetone-based glue. The assembled battery cell was filled with 20 ml of the initial electrolyte described in Example 1. The test battery cell was cycled using an Arbin Instruments battery cycler. The battery cell was charged to a capacity of 0.9 Ah at a constant current of 150 mA. The charging voltage limit was 2.3 V. The battery cell was discharged at a constant current of 140 mA until the voltage reached 1.1 V, after which the battery cell was further discharged at a constant current of 50 mA until the voltage reached 1.1 V. Figure 7 Shows the representative voltage as a function of test time for a mixed polyhalide initial electrolyte and a zinc bromide initial electrolyte according to an embodiment of the present disclosure. The zinc bromide initial electrolyte forms polybromide upon charging, unlike the mixed polyhalide formed in the present disclosure. Figure 7 The curve in [reference] shows a battery cell with a mixed polyhalide initial electrolyte having an open-circuit potential of 2 V (compared to 1.75 V for a conventional zinc-bromine battery), a discharge start voltage of 1.86 V (compared to 1.63 V for a conventional zinc-bromine battery), and a discharge energy that is approximately 10 - 20% higher than that of a conventional zinc-bromine battery (depending on the chloride-to-bromide ratio). Figure 7 The results are consistent with the increased voltage of Equation (2) above. Notably, the discharge time of the mixed polyhalide electrolyte is also much longer. This higher Coulombic efficiency indicates that the proposed electrolyte density gradient reduction mechanism is effective in the mixed polyhalide initial electrolyte.

[0216] Compared to a battery energy storage system with a control polybromide chemistry Figure 7The variation of the monotonically increasing charging voltage shown provides additional advantages in the design and operation of battery energy storage systems (BESS). State-of-charge monitoring is a key operating requirement for BESS, and traditionally voltage measurements have been used to track the state of charge during operation. For the voltage profile of the reference polybromide chemistry, this can be done during discharge, but not during charging, because there is no significant relationship between the state of charge and the charging voltage due to the flatness of the voltage profile. This makes state-of-charge monitoring and overcharge protection very complex when using such batteries. In contrast, the monotonically increasing voltage of the polyhalide chemistry means that simpler voltage tracking methods can be used during both charging and discharging.

[0217] Another advantage of the monotonically increasing voltage of the polyhalide chemistry compared to batteries with reference polybromide chemistry is that it allows the batteries to operate in a parallel configuration. In this configuration, the current on each battery will be adjusted to ensure that each battery has the same total voltage. To operate this configuration safely, it is important that the voltage-state-of-charge relationship of the batteries provides a self-balancing effect, whereby a battery with a higher state of charge will have a higher voltage and thus consume less current. In the absence of this effect, parallel operation of the batteries can lead to significant state-of-charge imbalances, as any current differences will cause long-term accumulation of state-of-charge imbalances. The charging voltage profile of the reference polybromide chemistry does not provide this self-balancing effect, while the voltage profile of the polyhalide chemistry does. This results in a significant increase in operational flexibility and battery energy storage design possibilities.

[0218] Example 3: Operating conditions of the test

[0219] Test battery cells were assembled using titanium metal current collectors coated with titanium carbide formed as plates. The anode and cathode plates were placed in a parallel configuration, separated by a 12 mm thick high-density polyethylene frame containing an embedded sealing ring that allowed the cell to be sealed by compressing the assembly between two opposing steel pressure plates. Before cell assembly, carbon felt was attached to the cathode titanium current collector using 13 ml of a conductive acetone-based glue. The assembled cell was filled with 210 ml of the initial electrolyte described in Example 1. The test battery cells were cycled using an Arbin Instruments battery cycler. Discharge energy, coulombic efficiency, and self-discharge tests were conducted under the following conditions:

[0220] Maximum charging voltage: 2.2 V - 2.4 V

[0221] Minimum discharge voltage: 1.1 V

[0222] Charging power range: 16 mW / cm 2 - 41 mW / cm 2(12 mW / mL - 31 mW / mL)

[0223] Discharge power range: 16 mW / cm 2 -41 mW / cm 2 (12 mW / mL - 31 mW / mL)

[0224] Charge capacity range: 68 mAh / cm 2 -137 mAh / cm 2 (54 mAh / mL - 104 mAh / mL)

[0225] The denominator of the geometric area is normalized to the geometric surface area of the cathode electrode, and the denominator is normalized to the volume (mL) of the electrolyte available in the battery cell.

[0226] Example 4: Effect of Cl / Br ratio on discharge energy

[0227] Construct and test the battery cell as described in Example 3. Figure 8 Shows the effect of the total Cl / Br molar ratio in the mixed polyhalide initial electrolyte according to the embodiments of the present disclosure on the discharge energy (Wh) when the battery cell with a cathode geometric surface area of 165 cm 2 is charged to a capacity of 97 mAh / cm 2 When the ratio of chloride to bromide is approximately 2:1, the discharge energy reaches a maximum. This indicates that there is an optimal ratio at which the mixed polyhalide species dominate during charging, below which dense polybromide species may dominate; above which there is not enough bromide on the electrode to form mixed polyhalides. There may be a competitive effect for the halide ratio, and different beneficial ratios may be obtained.

[0228] Example 5: Comparison of the coulombic efficiency of a battery cell using a mixed polyhalide electrolyte with a battery cell using only polybromide

[0229] Figure 9 Shows the representative average coulombic efficiency (%) of the mixed polyhalide initial electrolyte according to the embodiments of the present disclosure and the zinc bromide initial electrolyte that forms polybromide during charging without forming the mixed polyhalide in the present disclosure during ten charge and discharge cycles. The electrolyte that forms the mixed polyhalide always has a higher coulombic efficiency than the electrolyte with only polybromide.

[0230] Example 6: Comparison of the variation of the coulombic efficiency of a battery cell using a mixed polyhalide electrolyte with a battery cell using only polybromide with the cycle length

[0231] Construct and test the battery cell as described in Example 3. To study the variation of Coulombic efficiency with cycle length, the cycle length was varied by changing the charging power. Figure 10 Shows the variation of the representative average Coulombic efficiency with cycle length for a mixed polyhalide initial electrolyte according to an embodiment of the present disclosure and a polybromide-only initial electrolyte that forms polybromides upon charging but does not form the mixed polyhalides of the present disclosure. For the initial electrolyte that forms polybromides, the Coulombic efficiency decreases with cycle length, while for the electrolyte that forms mixed polyhalides, its Coulombic efficiency remains fairly consistent. This indicates that the self-discharge rate of the mixed polyhalide species is lower compared to polybromides.

[0232] Example 7: Comparison of the discharge voltage of a battery cell with a mixed polyhalide electrolyte and a battery cell using only polybromide

[0233] Construct and test the battery cell as described in Example 3. Figure 11 Shows the variation of the representative battery cell discharge voltage (V) with the battery cell discharge energy density (Wh / L) for a mixed polyhalide initial electrolyte according to an embodiment of the present disclosure and a zinc bromide initial electrolyte that forms polybromides upon charging but does not form the mixed polyhalides in the present disclosure. The mixed polyhalide initial electrolyte has a higher discharge voltage and a longer discharge time compared to the zinc bromide-only initial electrolyte.

[0234] Other embodiments

[0235] It should be clear that the above only relates to the preferred embodiments of the electrolytes and batteries disclosed herein, and many changes and modifications can be made herein without departing from the spirit and scope of any invention defined by the claims and their equivalents.

[0236] Based on the above and with reference to the various figures, those skilled in the art will understand that certain modifications can also be made to the present disclosure without departing from the scope of the present disclosure. Although several embodiments of the present disclosure are shown in the figures, it is not intended that the present disclosure be limited thereto, as it is intended that the scope of the present disclosure be as broad as permitted by the technology, and this specification should be understood accordingly. Therefore, the above description should not be construed as restrictive, but only as an example of a particular embodiment. Other modifications within the scope and spirit of the appended claims will occur to those skilled in the art.

Claims

1. A method for manufacturing a static battery cell, comprising the steps of: providing an initial electrolyte comprising one or more chloride ion sources and one or more bromide ion sources, wherein the one or more chloride ion sources and the one or more bromide ion sources are provided in a predetermined ratio, the predetermined ratio being selected to produce a target amount of mixed polyhalide when the initial electrolyte is at least significantly charged; and forming an electrochemical cell unit comprising an anode, a cathode, and the initial electrolyte.

2. The method according to claim 1, wherein the static battery cell is a static zinc halide electrochemical battery cell.

3. The method according to claim 2, wherein the static zinc halide electrochemical battery cell is located in a static zinc halide battery.

4. The method according to any one of the preceding claims, wherein the initial electrolyte comprises from about 5 wt.% to about 30 wt.% ZnBr 2 ; from about 5 wt.% to about 60 wt.% ZnCl 2 ; from about 10 wt.% to about 60 wt.% H 2 O; and from about 0.05 wt.% to about 20 wt.% of one or more quaternary ammonium agents.

5. The method according to any one of the preceding claims, wherein the mixed polyhalide produced when the initial electrolyte is at least significantly charged has the general formula [X (2n+1) Y (2m) - , where X and Y are different from each other and independently are Cl or Br, n is an integer between 0 and 5, and m is an integer between 1 and 5.​ 6. The method according to any one of the preceding claims, wherein the mixed polyhalide is BrCl 2 - , ClBr 2 - or a combination thereof.

7. The method according to any one of the preceding claims, wherein the one or more chloride ion sources are ZnCl 2 , KCl, NH 4 Cl, LiCl, CuCl 2 , CaCl 2 , FeCl 3 , SbCl 3 , CrCl 3 , NaCl, BiCl 3 , a quaternary ammonium salt having a chloride anion, or a combination thereof.

8. The method according to any one of the preceding claims, wherein the one or more bromide ion sources are ZnBr 2 , KBr, NH 4 Br, LiBr, CuBr 2 , CaBr 2 , NaBr, AgBr, AlBr 3 , a quaternary ammonium salt having a bromide anion, or a combination thereof.

9. The method according to any one of the preceding claims, wherein the predetermined ratio of the one or more chloride ion sources and the one or more bromide ion sources is a molar ratio of total chloride ions to total bromide ions of from about 1:1 to about 13:

1.

10. The method according to any one of the preceding claims, wherein the predetermined ratio of the one or more chloride ion sources and the one or more bromide ion sources is a molar ratio of total chloride ions to total bromide ions of from about 1:1 to about 2:

1.

11. The method according to any one of the preceding claims, wherein the initial electrolyte further comprises from about 0.5 wt.% to about 15 wt.% of KBr and from about 0.5 wt.% to about 15 wt.% of KCl.

12. The method according to any one of the preceding claims, wherein the initial electrolyte further comprises from about 0.5 wt.% to about 15 wt.% of KCl.

13. The method according to any one of the preceding claims, wherein the initial electrolyte comprises about 0 wt.% of KBr.

14. The method according to any one of claims 4 - 13, wherein the one or more quaternary ammonium agents are independently selected from quaternary ammonium agents having the formula N + (R 1 )(R 2 )(R 3 )(R 4 )X - , wherein R 1 is hydrogen or an alkyl group, R 2 , R 3 and R 4 are each independently an alkyl group the same as or different from R 1 , and X - is chlorine or bromine.

15. The method according to any one of claims 4 - 14, wherein the one or more quaternary ammonium agents are independently selected from tetramethylammonium chloride, tetraethylammonium chloride, tetrapropylammonium chloride, tetrabutylammonium chloride, tetramethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, or tetrabutylammonium bromide.

16. The method according to any one of the preceding claims, wherein the initial electrolyte further comprises from about 0.1 wt.% to about 3 wt.% of diglyme, wherein the diglyme is monoglyme, diglyme, triglyme, tetraglyme, pentaglyme, hexaglyme, or any combination thereof.

17. The method according to any one of the preceding claims, wherein the initial electrolyte further comprises up to 1 wt.% of one or more additives selected from Sn, In, Ga, Al, Tl, Bi, Pb, Sb, Ag, Mn, Fe, Cr, Sc, Cu, Al, Ru, Sr, or any combination thereof.

18. The method according to any one of the preceding claims, wherein the initial electrolyte further comprises DME - PEG having a number average molecular weight of about 1000 amu, DME - PEG having a number average molecular weight of about 2000 amu, or a combination thereof.

19. The method according to any one of the preceding claims, wherein the initial electrolyte further comprises PEG having a number average molecular weight of about 1000 amu, PEG having a number average molecular weight of about 3500 amu, or a combination thereof.

20. The method according to any one of the preceding claims, wherein significant charging of the electrochemical cell unit is when the electrochemical cell unit has been charged until it reaches an open circuit potential of at least 1.82 V and a volumetric charge capacity of at least 54 mAh / mL.

Images