Rechargeable alkaline battery with enhanced cycling stability and coulombic efficiency

Abstract

A rechargeable alkaline battery with enhanced cycling stability and coulombic efficiency is provided. The cell includes a cathode prepared using a cathode material, connected to the first end, an anode prepared using an anode material, connected to the second end, a hydroxide electrolyte having a higher concentration, and at least one porous separator positioned between the anode and the cathode. The hydroxide electrolyte inhibits hydrogen evolution reactions in the overall reaction from about 20% to less than 5%. The rechargeable alkaline battery is charged and discharged at the rate of 15 mA / cm < 2 >, and the capacity retention ratio of the rechargeable alkaline battery is up to 80% or above after 290 times of circulation during 40% of depth of discharge (DOD) circulation.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 509,286 filed on June 21, 2023, and the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0002] The present invention relates to the field of electrochemical technology, and in particular to a super-concentrated hydroxide electrolyte with a wide electrochemical stability window and application thereof. Background Art

[0003] In recent years, rechargeable zinc batteries have attracted widespread attention due to their high safety, high energy density, environmental friendliness, and low cost of zinc metal. The working principle of zinc batteries depends on the different acid-base properties of the electrolytes they use. Alkaline zinc batteries stand out due to their significant advantages over neutral batteries. In alkaline electrolytes, the discharge process of the zinc anode involves a short-range conversion between zinc and zinc oxide, which helps to mitigate shape changes and dendrite formation to a certain extent. Therefore, alkaline zinc batteries can usually achieve a charge capacity greater than 10 mAh / cm 2 High area capacity.

[0004] Furthermore, zinc electrodes can bring immediate practical benefits as a viable alternative to metal hydrides in NiMH batteries, leveraging established cathode and cell architectures. However, large-scale commercial applications of rechargeable alkaline zinc batteries have not yet been fully realized due to several key issues at the electrode interface, especially the hydrogen evolution reaction (HER) and zinc anode passivation during cycling.

[0005] Theoretically, these interfacial phenomena are closely related to the concentration of alkaline hydroxides in the electrolyte. During discharge, the solubility of zinc oxide in the electrolyte determines the storage mode of zinc oxide ions, which is positively correlated with the concentration. When its solubility is exceeded, the passivation layer formed by the release of zinc oxide limits the operation of zinc batteries at high depth of discharge (DoD). At the same time, since the equilibrium potential of zinc / zinc ions in traditional alkaline electrolytes is lower than that of reversible hydrogen electrodes, the hydrogen evolution reaction tends to occur preferentially thermodynamically, resulting in electrolyte volume loss and reduced Coulombic efficiency (CE).

[0006] In view of these challenges, a feasible solution is needed to simultaneously improve the solubility of zinc oxide and enhance the electrochemical stability of the electrolyte itself. The present invention addresses this need. Summary of the invention

[0007] Previous studies have not utilized high concentrations of metal hydroxides and oxides to achieve low water activity over a wide electrochemical range. In addition, reported cells have not shown high efficiency and long-term stability at deep discharge. The present invention aims to expand the narrow electrochemical window of alkaline electrolytes for application in high-voltage, high-energy-density rechargeable batteries.

[0008] In a first aspect, the present invention provides a rechargeable alkaline battery with enhanced cycle stability and coulombic efficiency. The battery includes a cathode made of a cathode material and connected to a first end, an anode made of an anode material and connected to a second end, a high concentration hydroxide electrolyte, and at least one porous separator between the anode and the cathode. The hydroxide electrolyte includes a solute and a solvent and has a concentration of at least 10M. It suppresses the hydrogen evolution reaction in the overall reaction from about 20% to less than 5%.

[0009] In one embodiment, the anode material includes zinc, zinc alloys, zinc hydroxide, zinc oxide, or other zinc compounds with low alkaline solubility.

[0010] In one embodiment, the cathode material comprises nickel oxide hydrate.

[0011] In one embodiment, the battery includes at least one porous separator, including nonwoven cellulose membranes, polymer films, ion selective membranes, and glass fiber separators.

[0012] In one embodiment, rechargeable alkaline cells include nickel zinc cells, silver zinc cells, and zinc air cells.

[0013] In one embodiment, the solute is one or more alkali metal hydroxides selected from lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, aluminum hydroxide or a combination thereof. The solvent includes deionized water, ethanol and dimethyl sulfoxide. The concentration of the one or more alkali metal hydroxides is 1-20 mol / L.

[0014] In another embodiment, the solute further comprises a metal oxide containing zinc oxide, aluminum oxide, boron oxide, tin oxide or a combination thereof. The concentration of the metal oxide is 0.001-5 mol / L.

[0015] The present invention utilizes high concentrations of metal hydroxides and / or oxides to limit the activity of water, thereby expanding a larger electrochemical window, while maintaining high ionic conductivity through structural diffusion of hydroxide ions. When the hydroxide concentration reaches 15M, the actual electrochemical window of the electrolyte can be extended to at least 2.1V, and the ionic conductivity at room temperature is at least 0.2S / cm.

[0016] When applied to rechargeable alkaline batteries (e.g., alkaline zinc batteries), the electrolyte can significantly suppress the amount of hydrogen gas generation, thereby keeping the battery stable during long-term deep cycling.

[0017] At 15 mA / cm 2 When the rechargeable alkaline battery is charged and discharged at a rate of 40% DOD, the capacity retention rate is as high as over 80% after 290 cycles.

[0018] At 30mA / cm 2 When charged and discharged at a rate of 60% DOD cycle, the rechargeable alkaline battery has a capacity retention rate of more than 95% after 90 cycles and maintains at least 95% Coulombic efficiency, and continues to operate for more than 135 times while maintaining 60% of the specific capacity.

[0019] Preferably, at 30 mA / cm 2 When charged and discharged at a rate of 60% DOD cycle, the rechargeable alkaline battery has a capacity retention rate of more than 96.77% after 90 cycles and maintains a coulombic efficiency of at least 96.77%, and continues to operate for more than 135 times while maintaining a specific capacity of 60%. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Embodiments of the present invention are described in more detail below with reference to the accompanying drawings, in which:

[0021] Figure 1 Depicted is a structural configuration of a Zn||NiOOH coin cell according to an embodiment of the present invention.

[0022] Figure 2 The electrochemical stability window and ionic conductivity of 6M, 9M, 12M, and 15M KOH electrolytes are depicted.

[0023] Figure 3 Linear sweep voltammetry plot of the hydrogen evolution reaction in 15 M KOH electrolyte saturated with Al2O3.

[0024] Figure 4 The polarization curve of the Zn||NiOOH coin cell constructed with the super-concentrated hydroxide electrolyte according to the embodiment of the present invention is depicted.

[0025] Figure 5 The cycling performance of Zn||NiOOH coin cells constructed with super-concentrated hydroxide electrolyte according to an embodiment of the present invention at 40% depth of discharge is depicted.

[0026] Figure 6 The cycling performance of Zn||NiOOH coin cells constructed with super-concentrated hydroxide electrolyte according to an embodiment of the present invention at 60% depth of discharge is depicted. DETAILED DESCRIPTION

[0027] The present invention provides a rechargeable alkaline battery with enhanced cycle stability and coulombic efficiency. The battery includes a cathode made of a cathode material and connected to a first end, an anode made of an anode material and connected to a second end, a hydroxide electrolyte with a relatively high concentration, and at least one porous separator between the anode and the cathode. The hydroxide electrolyte includes a solute and a solvent and has a concentration of at least 10M. It suppresses the hydrogen evolution reaction in the overall reaction from about 20% to less than 5%.

[0028] In one embodiment, the rechargeable alkaline battery may include a nickel zinc battery, a silver zinc battery, and a zinc air battery.

[0029] The typical electrochemical properties of water in hydroxide electrolytes are systematically investigated in Ni-Zn batteries. Figure 1 , the assembly process of the Zn||NiOOH coin cell involves several components arranged in a specific order to ensure its proper function. First, the construction of the button cell begins with the preparation of the cathode, which includes the cathode material and is connected to the first end. Specifically, a NiOOH (nickel oxide hydrate) layer is coated on the first end. Subsequently, the separator is carefully placed on the NiOOH layer to prevent direct contact with the anode and promote ion transport. Subsequently, the anode is deposited on the separator. The anode material includes a layer of zinc (Zn), and the anode is connected to the second end. To ensure proper sealing and insulation, gaskets are then inserted around the perimeter of the assembly. Finally, the second end is usually made of a conductive material similar to the first end and fixed in place to complete the circuit.

[0030] In one embodiment, the cathode material can be nickel oxide hydrate. The cathode material can also be iron or iron analogs, such as nickel iron oxide, manganese iron oxide, chromium iron alloy, molybdenum iron alloy, titanium iron alloy, vanadium iron alloy, copper iron alloy, cobalt iron alloy, etc.

[0031] The anode material can be zinc, zinc alloy, zinc hydroxide, zinc oxide or other zinc compounds with low alkaline solubility. In another embodiment, the anode material can also be aluminum or aluminum analogs, boron or boron analogs, both of which have obvious advantages in certain electrochemical applications. For example, aluminum analogs can be aluminum oxide, aluminum hydroxide. Boron analogs can be boron trioxide, boric acid.

[0032] At least one porous membrane acts as a barrier to maintain the integrity of the internal structure of the battery. The porous membrane can be a non-woven cellulose membrane, a polymer film, an ion selective membrane or a glass fiber membrane. The polymer film used for the battery separator needs to have good ion transport properties, chemical stability, thermal stability and mechanical strength. For example, the polymer film can be a polypropylene (PP) film, a polyester (PET) film, a polytetrafluoroethylene (PTFE) film, a polyethylene (PE) film, etc.

[0033] Preferably, the porous membrane can be selected from 3501 diaphragm.

[0034] The electrolytes disclosed in the present invention, specifically but not limited to water-based hydroxide electrolytes, can solve the limited electrochemical window problem inherent in water-based electrolytes. These electrolytes are designed to enhance the cycle stability and coulombic efficiency of rechargeable alkaline batteries (such as nickel-zinc batteries, silver-zinc batteries and zinc-air batteries) while maintaining ionic conductivity.

[0035] Hydroxide electrolytes generally refer to electrolyte solutions or solids containing hydroxide (OH-) ions. In one embodiment, the hydroxide electrolyte is formed by mixing an aqueous solution of a solute and a solvent. The solute may include one or more highly concentrated alkali metal hydroxide salts, to which may be added metal oxides or metal hydroxides, such as lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, aluminum hydroxide, zinc oxide, aluminum oxide, boron oxide, tin oxide, or a combination thereof. The solvent may include deionized water, ethanol, and dimethyl sulfoxide.

[0036] In one embodiment, the concentration of the hydroxide electrolyte is in the range of 6-10M.

[0037] Preferably, the concentration of the hydroxide electrolyte is at least 10 M. For example, the concentration may be 11M, 12M, 13M, 14M or 15M.

[0038] In one embodiment, the hydroxide electrolyte can be an alkaline solution, such as sodium hydroxide (NaOH) or potassium hydroxide (KOH), or an organic solution containing a hydroxide ligand, such as trimethylamine hydroxide (TMHAOH). In addition, the hydroxide electrolyte can also be a solid material, such as aluminum hydroxide (Al(OH)3) or sodium hydroxide particles (NaOH). These hydroxides play an important role in ion conduction and catalytic reactions in electrochemical processes.

[0039] In one embodiment, the concentration of the one or more alkali metal hydroxides is 1-20 mol / L.

[0040] Preferably, the concentration of the one or more alkali metal hydroxides is 9-20 mol / L.

[0041] More preferably, the concentration of the one or more alkali metal hydroxides is 15-20 mol / L.

[0042] In one embodiment, the concentration of the metal oxide is 0.001-5 mol / L.

[0043] More preferably, the concentration of the metal oxide is 0.1-5 mol / L.

[0044] The electrolyte can effectively suppress the hydrogen evolution reaction through a unique electrolyte structure and low water activity. The electrolyte structure includes pairs of metal cations and hydroxide anions that exclude some water molecules that are usually located in the cation solvation shell and are prone to hydrogen evolution reactions. Low water activity reduces the driving force and reaction kinetics for hydrogen production. Due to the unique hydroxide structure diffusion, the electrolyte maintains high ionic conductivity. These improvements have been observed in rechargeable alkaline batteries, including nickel-zinc batteries, silver-zinc batteries, and zinc-air batteries, achieving excellent cycling stability and coulombic efficiency at a large depth of discharge.

[0045] In the following description, specific details are provided in order to provide a thorough understanding of the present invention, but are for purposes of explanation only and not limitation.

[0046] Examples

[0047] Example 1

[0048] Preparation of water-soluble KOH electrolyte

[0049] A typical electrolyte is prepared by weighing different masses (molar concentrations) of commercial high-purity potassium hydroxide chemicals in ultrapure water, known as 15M KOH electrolyte. When testing, a three-electrode cell was assembled in which a gold foil was used as the working electrode, a platinum foil was used as the counter electrode, and Hg / HgO was used as the reference electrode.

[0050] The KOH electrolyte exhibits a broadened electrochemical stability window exceeding 2.5 V, with its cathode and anode limits far exceeding the theoretical decomposition voltage of water (1.23 V). In addition, it maintains a relatively high ionic conductivity of 0.2774 S / cm ( Figure 2 ).

[0051] Example 2

[0052] Preparation of NaOH-KOH mixed water-soluble electrolyte

[0053] A typical NaOH-KOH mixed aqueous electrolyte is prepared by weighing different masses (molar concentrations) of commercial high-purity potassium hydroxide and sodium hydroxide chemicals in ultrapure water. When assembling a three-electrode cell for testing, the total concentration of mixed solutes in the electrolyte is 20 mol / L. Among them, tin foil, platinum sheet and Hg / HgO are used as working electrode, counter electrode and reference electrode, respectively.

[0054] The electrolyte exhibits the ability to effectively suppress the hydrogen evolution reaction at room temperature, with an onset potential as low as -1.6 V and relatively high ionic conductivity.

[0055] Example 3

[0056] Preparation of saturated Al2O3 alkaline aqueous electrolyte

[0057] A typical alkaline aqueous electrolyte with saturated Al2O3 was prepared by weighing different masses (molar concentrations) of commercial high-purity chemical potassium hydroxide in ultrapure water. Subsequently, Al2O3 powder was dissolved in pure KOH solution at a higher temperature to form saturated Al2O3, which was then cooled to room temperature and filtered. In the assembly of a three-electrode cell, tin foil, platinum foil and Hg / HgO were used as the working electrode, counter electrode and reference electrode for testing, respectively.

[0058] The electrolyte exhibits the ability to effectively inhibit the hydrogen evolution reaction, with an onset potential as low as -1.6 V ( Figure 3 ).

[0059] Example 4

[0060] Alkaline nickel-zinc battery with super concentrated electrolyte

[0061] Figure 1 A coin cell design using an aqueous hydroxide electrolyte based on a NiOOH||Zn configuration is shown. The design uses a bicontinuous nanoporous (NP) Zn anode, a NiOOH / Ni(OH)2 cathode, and at least one porous separator, including a nonwoven cellulose membrane (16 mm diameter, 100 μm thick, 75% porosity) and a Celgard 3501 separator (16 mm diameter, 25 μm thickness, 55% porosity). The NiOOH / Ni(OH)2 cathode (1 cm 2) were used directly from fully charged commercial NiMH AAA cells (2600 mAh, GP Cells). For anodes cycled at 40% DOD, a solution consisting of 15 M KOH and saturated ZnO was used as the electrolyte for the cathode and separator. Prior to assembly, the anode was infiltrated with a 6 M KOH / 1 M LiOH solution in which 10 wt % Ca(OH)2 was suspended. For anodes cycled at 60% DOD, the aqueous electrolyte was 15 M KOH / saturated ZnO with 10 wt % Ca(OH)2 added.

[0062] Figure 4 and Figure 5 The prepared nickel-zinc battery showed a high current density of 15 mA / cm Zn 2 The stable performance when cycling at 40% DOD under charge and discharge has excellent cycle stability, and the capacity retention rate is still greater than 80% after 290 cycles.

[0063] In order to obtain higher energy density, a DOD greater than 40% may be urgently needed. After further increasing the DOD to 60%, the NiOOH||Zn battery retained its capacity for 90 cycles with 100% Coulombic efficiency and continued to operate for more than 135 cycles with a specific capacity retention of 60% ( Figure 6 ).

[0064] definition

[0065] Throughout this specification, unless otherwise specified herein, the word "comprise" or variations such as "comprises" or "comprising" should be understood to imply the inclusion of the stated integer or group of integers, but not the exclusion of any other integer or group of integers. It should also be noted that in this disclosure and particularly in the claims and / or paragraphs, terms such as "comprises / comprised / comprising" may have the meanings ascribed to them in U.S. patent law; for example, they allow for non-explicit recitation of elements but exclude elements that exist in the prior art or that affect the basic or novel characteristics of the invention.

[0066] Throughout the present specification and claims, unless otherwise indicated herein, the word "include" or variations such as "includes" or "including", will be understood to imply the inclusion of a stated integer or groups of integers but not the exclusion of any other integer or groups of integers.

[0067] As used herein, the terms "substantially," "essentially," "approximately," and "about" are used to describe and explain a small change. When used in conjunction with an event or circumstance, the terms may refer to the situation where the event or circumstance occurs exactly, as well as the situation where the event or circumstance occurs approximately. For example, when used in conjunction with a numerical value, these terms may include a range of variation less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%.

[0068] References in this specification to "one embodiment", "an exemplary embodiment", etc. indicate that the described embodiment may include certain features, structures, or characteristics, but each embodiment may not necessarily include the certain features, structures, or characteristics. Moreover, such phrases do not necessarily refer to the same embodiment. In addition, when a certain feature, structure, or characteristic is described in conjunction with an embodiment, it should be understood that it is within the knowledge of a technician in the field to affect such features, structures, or characteristics in conjunction with other embodiments, whether or not explicitly described.

[0069] In the preparation methods described herein, the steps may be performed in any order without departing from the principles of the invention unless a time sequence or an operational order is explicitly described. In a claim, it should be stated that one step is performed first and then several other steps are performed, which means that the first step is performed before any other steps, but the other steps may be performed in any appropriate order unless the sequence is further listed in the other steps. For example, a claim element listing "step A, step B, step C, step D, and step E" should be understood as step A being performed first and step E being performed last, and steps B, C, and D may be performed in any order between steps A and E, and the order is still within the literal scope of the claim process. A given step or subset of steps may also be repeated.

[0070] The term "higher depth of discharge (DoD)" refers to how far a battery can be fully discharged during a discharge cycle, i.e. the percentage of stored electrical energy released. In other words, it indicates the proportion of the battery's total energy storage capacity that is discharged during use. If a battery can achieve a higher depth of discharge, it means it can provide longer operating time or release more electrical energy, which is critical for applications that require long-term use or high power output.

[0071] A "coin cell" is a specific type of battery that is usually round and small, and shaped like a coin, hence the name. Coin cells are often used in small electronic devices such as watches, calculators, small sensors, or as a power source in laboratory settings. While coin cells can be disposable, they are usually rechargeable, such as silver oxide cells or lithium-ion cells.

[0072] The "NiOOH layer" refers to nickel oxide hydrate, which is a layer of material used as an anode in a battery. This layer is usually formed on the anode (or positive electrode) of a battery and participates in electrochemical reactions, such as in a nickel-metal hydride (NiMH) battery or a nickel-zinc (NiZn) battery. The NiOOH layer exhibits excellent chemical stability and conductivity, allowing the positive electrode of the battery to efficiently perform electrochemical reactions and provide the required energy.

[0073] Other definitions of selected terms used herein can be found in the detailed description of the entire invention and application. Unless otherwise defined, all other technical terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the invention belongs.

Claims

1. A rechargeable alkaline battery with enhanced cycle stability and coulombic efficiency, characterized in that, The rechargeable alkaline battery comprises: a cathode made of a cathode material and connected to the first terminal; an anode made of an anode material and connected to the second end; A hydroxide electrolyte comprising a solute and a solvent, wherein the hydroxide electrolyte has a concentration of At least 10 M, the hydroxide electrolyte suppresses the hydrogen evolution reaction in the overall reaction, reducing it from about 20% to less than 5%; and at least one porous separator located between the anode and the cathode, 15mA / cm 2 When the rechargeable alkaline battery is charged and discharged at a rate of 40% and the discharge depth is cycled at 40%, the capacity retention rate of the rechargeable alkaline battery is as high as more than 80% after 290 cycles.

2. The rechargeable alkaline battery of claim 1, wherein the rechargeable alkaline battery further comprises a spacer.

3. The rechargeable alkaline battery of claim 1, wherein the anode material comprises zinc, zinc alloy, zinc hydroxide, zinc oxide or other zinc compounds with low alkali solubility.

4. The rechargeable alkaline battery of claim 1, wherein the cathode material comprises nickel oxide hydrate.

5. The rechargeable alkaline battery of claim 1, wherein the at least one porous separator comprises a nonwoven cellulose membrane, a polymer film, an ion selective membrane, and a glass fiber separator.

6. The rechargeable alkaline battery according to claim 1, wherein the rechargeable alkaline battery comprises a nickel-zinc battery, a silver-zinc battery, and a zinc-air battery.

7. The rechargeable alkaline battery of claim 1, wherein the solute is an alkali metal hydroxide selected from one or more of lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, aluminum hydroxide, or combinations thereof.

8. The rechargeable alkaline battery according to claim 7, wherein the concentration of the alkali metal hydroxide is in the range of 1-20 mol / L.

9. The rechargeable alkaline battery of claim 7, wherein the solute further comprises zinc oxide, aluminum oxide, boron oxide, tin oxide, or a combination thereof.

10. The rechargeable alkaline battery according to claim 9, wherein the concentration of the metal oxide is 0.001-5 mol / L.

11. The rechargeable alkaline battery of claim 1, wherein the solvent comprises deionized water, ethanol, and dimethyl sulfoxide.

12. The rechargeable alkaline battery of claim 1, wherein the rechargeable alkaline battery exhibits an ionic conductivity of at least 0.2 S / cm at room temperature.

13. The rechargeable alkaline battery of claim 1, wherein the practical electrochemical window of the hydroxide electrolyte extends to at least 2.1V.

14. The rechargeable alkaline battery of claim 1, wherein the 2 When charged and discharged at a rate of 200 rpm and a depth of discharge of 60%, the rechargeable alkaline battery maintains a capacity retention rate greater than 95% after 90 cycles, maintains a coulombic efficiency of at least 95%, and continues to operate for more than 135 times while maintaining a specific capacity of at least 60%.

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