A mixed aqueous electrolyte containing a long-chain fatty acid zinc salt and applications thereof

Abstract

The application belongs to the technical field of electrochemical energy storage, and provides a mixed aqueous electrolyte containing long-chain fatty acid zinc salt and application thereof, which comprises a solvent and a zinc salt, the solvent is a mixture of deionized water and a non-aqueous organic solvent, the zinc salt comprises long-chain fatty acid zinc salt and other zinc salts, the concentration of the long-chain fatty acid zinc salt is 0.5-2 mol / L, the concentration of the other zinc salts is 0-5 mol / L, and the structural formula of the long-chain fatty acid zinc salt is as follows: Zn(R-COO)2; wherein R represents a hydrophobic long carbon chain organic group, and the total number of carbon atoms ranges from 6 to 30 (C). 2+ The long-chain fatty acid zinc is introduced in the application, which not only supplements Zn 2+ concentration as a zinc salt, but also serves as an interface modifier due to its unique molecular structure (long hydrophobic carbon chain and hydrophilic carboxyl group).

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage technology, and particularly relates to a mixed aqueous electrolyte containing long-chain fatty acid zinc salt and its application. Background Technology

[0002] With the escalating energy crisis, the development of efficient, safe, and low-cost electrochemical energy storage technologies has become an urgent priority. Aqueous batteries using water as a solvent are a hot topic in next-generation large-scale energy storage technologies due to their inherent safety, high ionic conductivity, environmentally friendly manufacturing, and low cost. In particular, aqueous zinc-ion batteries and aqueous zinc-based flow batteries are promising for commercialization because metallic zinc has a high theoretical specific capacity (820 mAh / g) and a low redox potential (-0.76 V vs. SHE).

[0003] However, conventional aqueous electrolytes (such as zinc sulfate and zinc trifluoromethanesulfonate aqueous solutions) face serious challenges: the thermodynamic stability window of water molecules is narrow, and the solvation shell of zinc ions contains a large amount of water ([Zn(H2O)6)). 2+ These active water molecules readily undergo hydrogen evolution at the negative electrode interface, leading to increased internal battery pressure, elevated pH, and accumulation of insulating byproducts. Simultaneously, a severe "sharp effect" exists during zinc deposition; due to uneven electric field distribution, zinc ions tend to deposit at protrusions, forming dendrites that eventually pierce the separator, causing a short circuit. Furthermore, traditional inorganic zinc salts or short-chain organic zinc salts are extremely polar and cannot effectively construct a hydrophobic interface layer, making it difficult to fundamentally prevent water molecules from contacting the negative electrode.

[0004] Existing technologies often address these issues by adding trace amounts of organic additives. However, these additives are not only consumed, but they also do not contribute to capacity or provide effective conductivity for zinc ions. Summary of the Invention

[0005] The purpose of this invention is to provide a mixed aqueous electrolyte containing long-chain fatty acid zinc salts, in order to solve the problems mentioned in the background art.

[0006] This invention is implemented as follows: a mixed aqueous electrolyte containing long-chain fatty acid zinc salts, comprising a solvent and zinc salts, wherein the solvent is a mixture of deionized water and a non-aqueous organic solvent, and the zinc salts include long-chain fatty acid zinc salts and other zinc salts, wherein the concentration of the long-chain fatty acid zinc salts is 0.5-2 mol / L, and the concentration of the other zinc salts is 0-5 mol / L. The structural formula of the long-chain fatty acid zinc salts is shown below: Zn(R-COO)2; Wherein, R represents a hydrophobic long-chain organic group, and the total number of carbon atoms ranges from 6 to 30.

[0007] Another objective of this invention is to provide an application of a mixed aqueous electrolyte containing long-chain fatty acid zinc salt in the preparation of electrochemical energy storage devices.

[0008] This invention introduces long-chain fatty acid zinc into an aqueous electrolyte. Long-chain fatty acid zinc salts are typical amphiphilic molecules; under electrochemical conditions, their anions (R-COO)... - Utilizing the polar carboxyl group "head" as an anchoring point, these molecules tightly assemble on the zinc-loving metal anode surface through chemical bonding (coordination) or electrostatic adsorption. Meanwhile, their hydrophobic long carbon chain "tails" extend vertically or obliquely towards the electrolyte side, facing away from the electrode surface. This self-assembly forms a dense, ordered hydrophobic barrier, effectively "squeezing out" a large number of free and solvated water molecules from the inner layer of the electric double layer. This cuts off the supply of active water for the hydrogen evolution reaction, thus thermodynamically and kinetically inhibiting water decomposition and electrode corrosion. The van der Waals forces between the long-chain molecules form a flexible mesh structure, which allows desolvated Zn... 2+ It passes smoothly through the electrolyte, but effectively blocks large solvent molecule clusters, anionic clusters, or macromolecular byproducts from contacting the electrode surface. More importantly, this ordered molecular array homogenizes the local electric field distribution on the electrode surface, eliminating the electric field concentration effect caused by the roughness of the electrode surface. The adsorption layer induces zinc ions to deposit in parallel and dense layers along specific crystal planes, thereby fundamentally suppressing vertically growing zinc dendrites and the resulting risk of membrane puncture. This invention also emphasizes the synergistic effect of long-chain fatty acid zinc and organic solvents (such as alcohols, ethers, amides, etc.). Long-chain fatty acid zinc has extremely low solubility in pure water and cannot reach an effective concentration. The introduction of organic co-solvents utilizes the principle of "like dissolves like" to break the hydrophobic association between long-chain molecules, allowing them to be uniformly dispersed in the electrolyte in ionic form, ensuring the effective ionic conductivity of zinc ions. Furthermore, the concentration of long-chain fatty acid zinc in the electrolyte was controlled in this embodiment of the invention to achieve optimal electrochemical performance: When the concentration of long-chain fatty acid zinc is too low (below 0.1 mol / L), it is insufficient to construct a continuous and dense hydrophobic protective layer on the zinc anode surface, leaving a large number of exposed active sites at the interface. This results in the inability to effectively suppress hydrogen evolution reaction and dendrite growth. Simultaneously, if it is used as the main salt, an excessively low ion concentration leads to insufficient ionic conductivity, failing to meet the device power requirements. When the concentration of long-chain fatty acid zinc is too high (above 5 mol / L or close to saturation solubility), the steric hindrance effect of the long carbon chain and intermolecular interactions cause a significant increase in electrolyte viscosity, reducing the migration rate of zinc ions. In addition, an excessively thick interfacial adsorption layer introduces a large interfacial impedance, leading to an increase in deposition / stripping overpotential, reduced voltage efficiency, and even the risk of solute precipitation clogging the membrane at low temperatures. Therefore, the preferred concentration range of long-chain fatty acid zinc in this embodiment of the invention is 0.5-2 mol / L. Within this range, the electrolyte exhibits a balance of high ionic conductivity, excellent interfacial wettability, and robust interfacial protection. Attached Figure Description

[0009] Figure 1 The electrochemical performance comparison results of the half-cells prepared with the electrolytes of Example 1 and Comparative Examples 1-2 of this invention; Figure 2 The results show the comparison of the electrochemical performance of full cells prepared with the electrolytes of Examples 1 and 4 and Comparative Examples 1-2 of this invention. Detailed Implementation

[0010] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0011] This invention provides an electrolyte comprising a zinc salt, wherein the zinc salt includes a long-chain fatty acid zinc salt; This long-chain fatty acid zinc salt has the following general structure: Zn(R-COO)2; Wherein, R represents a hydrophobic long-chain organic group, and the total number of carbon atoms (C) ranges from 6 to 30. Based on the differences in the microstructure of the R group, this long-chain fatty acid zinc can be subdivided into the following three categories, each with the following unique general structural formula: The first category consists of linear long-chain fatty acid zinc salts. These zinc salts are characterized by their linearly arranged hydrophobic tail chains, lack of side chain branches, and ease of forming a tightly packed self-assembled monolayer on the electrode surface. They have the following general structure: Zn[CH3-(CH2) n -COO]2; Where n is an integer representing the number of repeating units of methylene (-CH2-), and the value range is 4≤n≤28; This general formula covers zinc saturated straight-chain fatty acids; if the chain contains double bonds (unsaturated), the carbon-hydrogen ratio in the general formula is adjusted accordingly to C. n H 2n-1 Or lower; The linear long-chain fatty acid zinc is selected from at least one of the following specific compounds: zinc caprylate, zinc decanoate, zinc laurate, zinc myristate, zinc palmitate, zinc stearate, zinc arachidate, zinc behenate, zinc creosote, zinc oleate, zinc linoleate, zinc linolenate, and zinc erucate. The second category: branched long-chain fatty acid zinc salts. These zinc salts are characterized by the presence of alkyl side chains (branches) on their carbon chain backbone. The steric hindrance effect of the branches disrupts the crystallinity of the molecule, significantly improving its solubility in organic solvents and enabling the formation of a flexible amorphous protective film at the interface. They have the following general structure: Zn[C(R1)(R2)(R3) -COO]2; Wherein, R1, R2, and R3 are hydrogen or different alkyl groups (such as methyl, ethyl, butyl, etc.), and the sum of the number of carbon atoms of R1, R2, and R3 is C≥4; The branched long-chain fatty acid zinc is selected from at least one of the following specific compounds: zinc 2-ethylhexanoate, zinc isostearate, and zinc neodecanoate; The third category: functionalized long-chain fatty acid zinc salts. These zinc salts are characterized by the introduction of specific polar functional groups on their hydrophobic carbon chains. These functional groups provide additional anchoring sites, which can enhance the adsorption and binding force between the zinc salt and the electrode surface, or participate in specific interfacial polymerization reactions. They have the following general structure: Zn[R4-X-COO]2; Wherein, R4 represents a long-chain alkylene or alkenylene skeleton (C5~C6). 29 X represents a polar functional group other than the carboxyl group, selected from at least one of hydroxyl (-OH), epoxy, amino (-NH2), double bond (-CH=CH-), and ketone carbonyl (-C=O); The functionalized long-chain fatty acid zinc is selected from at least one of the following specific compounds: zinc 12-hydroxystearate, zinc ricinoleate, and zinc undecenoate.

[0012] Meanwhile, the zinc salt configuration used in the embodiments of the present invention is further subdivided into the following two types: Single primary salt: at least one of the first, second, and third type long-chain fatty acid zincs is used as the sole source of electrolyte salt; Mixed zinc salts: At least one of the first, second, and third types of long-chain fatty acid zinc salts, combined with other zinc salts, wherein the other zinc salts are selected from at least one of the following specific compounds: zinc sulfate (ZnSO4), zinc chloride (ZnCl2), zinc bromide (ZnBr2), zinc iodide (ZnI2), zinc trifluoromethanesulfonate (Zn(OTf)2), zinc acetate (Zn(CH3COO)2), zinc nitrate (Zn(NO3)2), zinc perchlorate (Zn(ClO4)2), zinc tetrafluoroborate (Zn(BF4)2), and zinc bis(trifluoromethanesulfonyl)imide (Zn(TFSI)2); more preferably, the other zinc salts are at least one of zinc trifluoromethanesulfonate (Zn(OTf)2), zinc acetate (Zn(CH3COO)2), or zinc bis(trifluoromethanesulfonyl)imide (Zn(TFSI)2); In this embodiment of the invention, based on the total volume of the electrolyte, the concentration of long-chain fatty acid zinc is 0.1-5 mol / L, and the concentration of other zinc salts is 0-5 mol / L; in this embodiment of the invention, the concentration of zinc salts in the solvent is 0.5 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, 5 mol / L, 5.5 mol / L, 6 mol / L, 6.5 mol / L, 7 mol / L, 7.5 mol / L, 8 mol / L, 8.5 mol / L, 9 mol / L, 9.5 mol / L, 10 mol / L, or any range of these values.

[0013] Since zinc long-chain fatty acids are mostly insoluble or only slightly soluble in pure water, the solvent in this electrolyte is a mixture of deionized water and a non-aqueous organic solvent. The non-aqueous organic solvent is selected from polar organic solvents that can effectively dissolve zinc long-chain fatty acids, including but not limited to alcohols, ethers, esters, amides, sulfones, or nitriles. It can be at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, ethylene glycol dimethyl ether, tetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diphenyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, dimethyl carbonate, methyl acetate, methyl propionate, ethyl acetate, ethyl propionate, propyl acetate, propyl propionate, ethylene carbonate, propylene carbonate, butenyl carbonate, γ-butyrolactone, butyl carbonate, formamide, sulfolane, methyl ethyl sulfone, dimethyl sulfoxide, and acetonitrile. Based on the total volume of the electrolyte, the volume of non-aqueous organic solvents accounts for 0-95 vol of the total electrolyte volume.

[0014] This invention also provides an electrochemical energy storage device, which may be an aqueous zinc-ion battery, an aqueous zinc metal battery, an aqueous zinc-based flow battery, or a zinc-air battery, etc. In this invention, the electrochemical energy storage device includes a positive electrode, a negative electrode, a separator and / or a solid electrolyte and an electrolyte solution. This electrochemical energy storage device can be applied in energy storage power stations, uninterruptible power supplies, large household batteries, portable outdoor energy storage power supplies, flexible wearable electronic devices, implantable medical electronic devices, rail transit braking energy recovery devices, substation DC operating power supplies, laptops, input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, headsets, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, and other fields. The electrolyte used in this electrochemical energy storage device is any of the electrolytes mentioned above, and may also include other electrolytes that do not depart from the scope of the present invention; In this embodiment of the invention, the negative electrode sheet includes a negative current collector and a negative electrode material layer. The negative electrode material layer is disposed on the surface of the negative current collector and includes a negative electrode active material. The specific type of negative electrode active material is not specifically limited and can be selected according to requirements. In this embodiment of the invention, the negative electrode active material is at least one of silicon-based materials, carbon-based materials, tin-based materials, phosphorus-based materials, metals, and alloy-based materials. The silicon-based material is at least one of silicon, silicon alloys, silicon oxides, and silicon-carbon compounds. The carbon-based material is at least one of graphite, soft carbon, hard carbon, carbon nanotubes, and graphene. The tin-based material is at least one of tin, tin oxides, and tin alloys. The phosphorus-based material is phosphorus and / or phosphorus complexes. The metal is at least one of zinc, aluminum, magnesium, lithium, sodium, and potassium. The alloy includes metals / quasi-metals that can be alloyed, for example, those that can be alloyed. The metal / quasi-metal is Si, Sn, Al, Ge, Pb, Bi, Sb, Si-Y alloy (where Y is an alkali metal, alkaline earth metal, element of group 13-16, transition metal, rare earth element or combination thereof, except Si), or Sn-Y alloy (where Y is an alkali metal, alkaline earth metal, element of group 13-16, transition metal, rare earth element or combination thereof, except Sn), and Y can be Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po or combination thereof; In this embodiment of the invention, the negative electrode material layer further includes a binder, which has a mass percentage of 0.3-5% based on the total mass of the negative electrode material layer, and is used to improve the bonding between the negative electrode active material particles and the bonding between the negative electrode active material and the current collector; non-limiting examples of binders include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc. In embodiments of the present invention, the negative electrode material layer may further include a conductive agent, wherein the mass percentage of the conductive agent is 0.3-3% based on the total mass of the negative electrode material layer; the conductive agent may include any conductive material as long as it does not cause a chemical change, and non-limiting examples of conductive materials include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powder, metal fiber, etc., such as copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof; In this embodiment of the invention, the negative electrode current collector may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with conductive metal, and combinations thereof; In embodiments of the present invention, the positive electrode sheet includes a current collector and a positive electrode active material layer located on the current collector. The positive electrode active material includes, but is not limited to: manganese dioxide (MnO2), manganese trioxide (Mn2O3), manganese trioxide (Mn3O4), spinel lithium manganese oxide (LiMn2O4), lithium-rich manganese-based solid solution (xLi2MnO3·(1-x)LiMO2), zinc manganate (ZnMn2O4), and sodium manganate (Na2O4). 0.44 MnO2), magnesium manganese oxide (MgMn2O4), vanadium pentoxide (V2O5), vanadium dioxide (VO2), lithium vanadate (LiV3O8), sodium vanadate (NaV3O8), zinc vanadate hydrate (ZnO2), etc. 0.25 V₂O₅·nH₂O), ammonium vanadate (NH₄V₄O) 10 ), calcium vanadate (CaV6O) 16 ·3H2O), hydrated vanadium pentoxide (V2O5·nH2O), ferric ferricyanide (Prussian blue) (Fe4[Fe(CN)6]3), copper hexacyanoferrate (K2Cu[Fe(CN)6]), zinc hexacyanoferrate (K2Zn3[Fe(CN)6]2), sodium vanadium phosphate (Na3V2(PO4)3), polyaniline (PANI), polypyrrole (PPy), polythiophene derivative (PEDOT), p-benzoquinone (C6H4O2), pyrene-4,5,9,10-tetraone (C 16 The active materials for the positive electrode are: H6O4, iodine (I2), lead dioxide (PbO2), nickel hydroxyl oxide (NiOOH), silver oxide (Ag2O), molybdenum disulfide (MoS2), and molybdenum diselenide (MoSe2); more preferably, the active material for the positive electrode is vanadium pentoxide (V2O5). In this embodiment of the invention, the positive electrode active material layer further includes an adhesive, and optionally includes a conductive material. The adhesive is used to improve the bonding between the positive electrode active material particles and also to improve the bonding between the positive electrode active material and the current collector. In this embodiment of the invention, the adhesive may be polyvinyl alcohol, polyacrylic acid, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyacrylamide, polymethyl methacrylate, sodium alginate, chitosan, gelatin, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon, etc. In embodiments of the present invention, the conductive materials include, but are not limited to: carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof; the carbon-based materials are selected from natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof; the metal-based materials are selected from metal powder, metal fiber, copper, nickel, aluminum, or silver; the conductive polymer is a polyphenylene derivative; In this embodiment of the invention, the material and shape of the diaphragm are not particularly limited, and can be any technology disclosed in the prior art. For example, the diaphragm may include a substrate layer and a surface treatment layer. The substrate layer may be a glass fiber filter membrane, bacterial cellulose membrane, nonwoven fabric, membrane, or composite membrane with a porous structure. The material of the substrate layer is at least one of glass fiber, cellulose, polyethylene, polypropylene, and polyethylene terephthalate. Specifically, a glass fiber filter membrane, bacterial cellulose membrane, polypropylene nonwoven fabric, polyethylene nonwoven fabric, or polypropylene-polyethylene-polypropylene porous composite membrane may be selected. At least one surface of the substrate layer is provided with a surface treatment layer, which may be a polymer layer or an inorganic layer, or a layer formed by mixing polymers and inorganic substances. The inorganic layer includes inorganic particles and a binder, and the inorganic particles are alumina, silicon oxide, magnesium oxide, oxygen, etc. The material contains at least one of titanium dioxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate; and the binder is at least one of polyvinyl alcohol, polyacrylic acid, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyacrylamide, polymethyl methacrylate, sodium alginate, chitosan, gelatin, polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl alkoxy, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene. In this embodiment of the invention, the diaphragm is a glass fiber diaphragm, wherein the diaphragm thickness is in the range of 0.7 to 2.7 mm, and the air permeability is 3.7-19 s·100 mL·in. 2 Within the range; In some embodiments of the present invention, the electrochemical energy storage device may include an outer packaging, which may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc., or a soft package, such as a pouch-type soft package. The material of the soft package may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.

[0015] This invention also provides an apparatus including the above-mentioned electrochemical energy storage device. The apparatus includes, but is not limited to, energy storage systems, energy storage systems, electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, etc. In order to meet the high power and high energy density requirements of the secondary battery for the apparatus, a battery pack or battery module can be used.

[0016] Unless otherwise specified, all reagents, materials and instruments used in the following examples and comparative examples are commercially available.

[0017] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0018] Example 1: A mixed aqueous electrolyte containing long-chain fatty acid zinc salts, the preparation method of which includes the following steps: Dissolve 35.2g of zinc octoate in 60ml of methanol, add 40ml of deionized water, and stir to obtain the electrolyte.

[0019] Example 2: A mixed aqueous electrolyte containing long-chain fatty acid zinc salts, the preparation method of which includes the following steps: Dissolve 35.1g of zinc 2-ethylhexanoate in 60ml of methanol, add 40ml of deionized water, and stir to obtain the electrolyte.

[0020] Example 3: A mixed aqueous electrolyte containing long-chain fatty acid zinc salts, the preparation method of which includes the following steps: Dissolve 36.4g of zinc ricinoleate in 60ml of methanol, add 40ml of deionized water, and stir to obtain the electrolyte.

[0021] Example 4: A mixed aqueous electrolyte containing long-chain fatty acid zinc salts, the preparation method of which includes the following steps: Dissolve 17.6 g of zinc octoate and 17.5 g of zinc 2-ethylhexanoate in 60 ml of methanol, add 40 ml of deionized water, and stir to obtain the electrolyte.

[0022] Example 5: A mixed aqueous electrolyte containing long-chain fatty acid zinc salts, the preparation method of which includes the following steps: Dissolve 35.2g of zinc stearate in 60ml of methanol, add 40ml of deionized water, add 16.1g of zinc sulfate, and stir to obtain the electrolyte.

[0023] Comparative Example 1: An aqueous electrolyte, the preparation method of which includes the following steps: Dissolve 32.3g ZnSO4 in 100 ml of water and stir to obtain the electrolyte.

[0024] Comparative Example 2: An aqueous electrolyte, the preparation method of which includes the following steps: Dissolve 32.3g ZnSO4 in 40 ml of water, add 60 ml of methanol, and stir to obtain the electrolyte.

[0025] Comparative Example 3: An aqueous electrolyte, the preparation method of which includes the following steps: Dissolve 3.52g of zinc octoate in 60ml of methanol, add 40ml of deionized water, and stir to obtain the electrolyte.

[0026] Comparative Example 4: An aqueous electrolyte, the preparation method of which includes the following steps: Dissolve 70.4g of zinc octoate in 60ml of methanol, add 40ml of deionized water, and stir to obtain the electrolyte.

[0027] Zn / Cu and Zn / V₂O₅ batteries were prepared using the electrolytes from Examples 1-5 and Comparative Examples 1-4, and then coulombic efficiency and cycle stability tests were performed. The coulombic efficiency test was conducted using Zn / Cu batteries. The batteries were assembled in the following order: negative electrode shell, spring plate, gasket, zinc plate, separator, copper plate, and positive electrode shell. 50 to 90 microliters of electrolyte were added to each battery to wet the separator, and finally, the batteries were sealed. The batteries were first tested at a voltage range of 0-1V with a flow rate of 0.1 mA / cm². 2 The current density was pre-charged and discharged 5 times at 1 mA / cm². 2 The zinc was stripped at a current density until the voltage exceeded 1V. The battery was then subjected to a current density of 1 mA / cm² within the 0-1V voltage range. 2 Deposition was performed at a current density of 1 mA / cm for one hour, followed by deposition at 1 mA / cm. 2 The zinc was stripped using a current density until the voltage exceeded 1V, and the coulombic efficiency was calculated. Coulombic efficiency = discharge capacity / charge capacity.

[0028] Full cell capacity retention test: Zn / V2O5 batteries were used for testing. The batteries were assembled in the following order: negative electrode shell, spring contact, gasket, zinc plate, separator, positive electrode plate, and positive electrode shell. 50 to 90 microliters of electrolyte were added to each battery to wet the separator, and finally, the batteries were sealed. The batteries were first pre-charged and discharged at a current density of 0.1C within the 0.3-1.5V voltage range, followed by charge-discharge cycles at a current density of 1C within the 0.3-1.5V voltage range. The results are as follows Figure 1 , Figure 2 As shown in Tables 1 and 2: Table 1 Table 2 As can be seen, compared with Comparative Example 1, Examples 1-3 showed significant performance improvements in half-cell cycle life, initial coulombic efficiency, and full-cell capacity retention. The half-cell cycle life and full-cell capacity retention of Comparative Example 1 were significantly lower than those of Examples 1-3, indicating that in traditional aqueous electrolytes lacking long-chain fatty acid zinc protection, active water molecules led to severe hydrogen evolution reaction and zinc anode corrosion. In contrast, Examples 1-3 showed significant improvements in half-cell cycle life, full-cell capacity retention, and cycle life. This is mainly due to the long-chain fatty acid zinc salt anion (R-COO-). - The polar carboxyl group "head" is anchored to the negative electrode surface, while the hydrophobic long carbon chain "tail" self-assembles to form a dense and ordered hydrophobic barrier, which "squeezes out" free water molecules from the inner layer of the double layer, thereby significantly suppressing side reactions. Comparing Example 1 and Comparative Example 2, the synergistic effect mechanism of long-chain fatty acid zinc and non-aqueous organic solvents is demonstrated. Although Comparative Example 2 introduced methanol to reduce water activity, making its performance better than that of Comparative Example 1 with pure water system, it was still far inferior to Example 1. This shows that it is not enough to rely solely on non-aqueous organic solvents to reduce water activity. It is necessary to combine it with the specific adsorption and desolvation promoting effect of long-chain fatty acid zinc. The adsorption layer formed by long-chain fatty acid zinc molecules at the interface not only physically blocks solvent molecule clusters, but also homogenizes the local electric field distribution on the electrode surface, eliminates the "sharp effect", and thus induces zinc ions to undergo dense layered deposition. Comparing Example 1 with Comparative Examples 3 and 4 reveals the key impact of concentration control on electrochemical performance. In Comparative Example 3, the concentration of long-chain fatty acid zinc was too low (0.1 mol / L), resulting in a half-cell life of only 16 cycles and a significant decrease in full-cell capacity retention. This was because the concentration was insufficient to construct a continuous and dense hydrophobic protective layer on the negative electrode surface, leaving a large number of exposed active sites at the interface. Furthermore, the low ion concentration resulted in insufficient ionic conductivity, failing to support the normal ionic conductivity requirements of the battery. Conversely, in Comparative Example 4, the concentration was too high (2 mol / L). Although it was superior to Comparative Example 3, its performance was significantly lower than that of Example 1. This was mainly attributed to the high concentration leading to the steric hindrance effect of the long carbon chain and enhanced intermolecular interactions, which significantly increased the electrolyte viscosity and reduced the migration rate of zinc ions. At the same time, the excessively thick interfacial adsorption layer introduced a huge interfacial impedance, resulting in an increase in deposition / stripping overpotential and deteriorating interfacial kinetics. Example 4 employed a combination strategy of zinc octanoate and zinc 2-ethylhexanoate to achieve optimal overall performance. This indicates that the linear fatty acid zinc (zinc octanoate) and branched fatty acid zinc (zinc 2-ethylhexanoate) structures form a complementary effect in interfacial adsorption. The branched structure may increase the flexibility of the interfacial film or further optimize the void filling, making the SEI film constructed by the composite additives exhibit superior ability in suppressing dendrite growth and adapting to changes in electrode volume. Furthermore, Example 5 demonstrates the advantages of using a mixture of long-chain fatty acid zinc and inorganic zinc salts. Compared with Comparative Example 2, the introduction of zinc octoate in Example 5 significantly improved both the half-cell life and the full-cell retention rate. This indicates that long-chain fatty acid zinc, as a functional co-salt, successfully compensates for the weak interfacial protection capability of inorganic zinc salts. While ensuring high ionic conductivity, it modifies the interface using its hydrophobic long carbon chains, achieving a synergistic protection effect.

[0029] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. The application of a mixed aqueous electrolyte containing long-chain fatty acid zinc salt in the preparation of electrochemical energy storage devices, characterized in that, The electrochemical energy storage device is an aqueous zinc-ion battery or an aqueous zinc metal battery. The mixed aqueous electrolyte containing long-chain fatty acid zinc salts includes a solvent and zinc salts. The solvent is a mixture of deionized water and a non-aqueous organic solvent. The zinc salts include long-chain fatty acid zinc salts and other zinc salts. The concentration of the long-chain fatty acid zinc salts is 0.5-1 mol / L, and the concentration of the other zinc salts is 0-5 mol / L. The long-chain fatty acid zinc salt is selected from at least one of the following compounds: zinc octanoate, zinc decanoate, zinc laurate, zinc myristate, zinc palmitate, zinc stearate, zinc arachidate, zinc behenate, zinc creosote, zinc oleate, zinc linoleate, zinc linolenate, zinc erucate, zinc 2-ethylhexanoate, zinc isostearate, zinc neodecanoate, zinc 12-hydroxystearate, zinc ricinoleate, and zinc undecenoate. The volume of the non-aqueous organic solvent accounts for 60-95 vol% of the total electrolyte volume.

2. The application according to claim 1, characterized in that, The other zinc salts are selected from at least one of the following compounds: zinc sulfate, zinc chloride, zinc bromide, zinc iodide, zinc trifluoromethanesulfonate, zinc acetate, zinc nitrate, zinc perchlorate, zinc tetrafluoroborate, and zinc bis(trifluoromethanesulfonyl)imide.

3. The application according to claim 1, characterized in that, The non-aqueous organic solvent is at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, ethylene glycol dimethyl ether, tetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, methyl ethyl carbonate, methyl acetate, methyl propionate, ethyl acetate, ethyl propionate, propyl acetate, propyl propionate, ethylene carbonate, propylene carbonate, butenyl carbonate, γ-butyrolactone, butylene carbonate, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate, dimethyl methylphosphonate, acetonitrile, sulfolane, methyl ethyl sulfone, dimethylformamide, dimethylacetamide, dimethyl dimethoxysilane, and methyltriethoxysilane.

4. The application according to claim 1, characterized in that, The electrochemical energy storage device includes a positive electrode, a negative electrode, and a separator.

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