Alloy reference electrode, preparation method thereof and three-electrode soft package battery

Abstract

The application belongs to the field of batteries, and specifically discloses an alloy reference electrode, a preparation method thereof and a three-electrode soft package battery. The alloy reference electrode comprises a metal material and an alloy layer on the surface of the metal material. The alloy layer contains alloy particles. The alloy particles comprise aluminum-lithium alloy particles, aluminum-sodium alloy particles, aluminum-potassium alloy particles, sodium-tin alloy particles, lithium-tin alloy particles, potassium-tin alloy particles, sodium-bismuth alloy particles, potassium-bismuth alloy particles or lithium-bismuth alloy particles, sodium-antimony alloy particles, potassium-antimony alloy particles or lithium-antimony alloy particles. The alloy reference electrode has a stable potential and will not dissolve in the electrolyte or react with the electrolyte at high temperatures. When the alloy reference electrode is applied to the three-electrode soft package battery, the potential changes of each electrode in the charging and discharging process of the whole battery can be observed, and the monitoring of a single electrode in the charging and discharging cycle process can be realized without damage.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and specifically relates to an alloy reference electrode, its preparation method, and a three-electrode soft-pack battery. Background Technology

[0002] Lithium-ion batteries (or sodium-ion batteries) have become a very important energy storage technology due to their high energy density, long cycle life, and low self-discharge. To better study the potential changes of the positive and negative electrodes during charging and discharging in battery design and research, it is necessary to distinguish the effects of the positive and negative electrodes on cell performance. Therefore, a third electrode, the reference electrode, is introduced into pouch cells. The potential and impedance of the positive and negative electrodes relative to the reference electrode are measured during charging and discharging, providing data support for individual electrode studies. Real-time monitoring of the electrochemical behavior of the positive and negative electrodes relative to the reference electrode provides a basis for cell design.

[0003] Among the widely used reference electrodes, copper wire reference electrodes have the advantages of simple and inexpensive preparation. However, in practical applications, the metallic lithium (sodium) plated on the copper wire is extremely reactive and dissolves into the battery system in a short time at high temperatures, affecting the interpretation of battery data during testing. Furthermore, the copper wire needs to be re-plated with lithium, making it unsuitable for monitoring the positive and negative electrode voltages of long-cycle batteries. Reference electrodes made directly from metallic lithium, while simple to prepare, react with the electrolyte in lithium-ion batteries, gradually consuming the lithium source during charge-discharge cycles, thus hindering long-term monitoring of lithium-ion battery cycle performance. Silver, gold, and platinum wires are expensive, and the exposed metal wires can interfere with electrical signals. Although lithium iron phosphate has a relatively stable lithium insertion / extraction voltage platform and can be used as a reference electrode, offering advantages for monitoring the positive and negative electrode voltages of long-cycle batteries, its high cost and complex activation process necessitate optimization of the reference electrode to address at least one of the technical problems existing in the current technology. Summary of the Invention

[0004] In order to overcome at least one of the technical problems existing in the prior art, one of the objectives of the present invention is to provide an alloy reference electrode.

[0005] The second objective of this invention is to provide a method for preparing an alloy reference electrode.

[0006] The third objective of this invention is to provide a three-electrode soft-pack battery.

[0007] The fourth objective of this invention is to provide a method for preparing a three-electrode soft-pack battery.

[0008] The fifth objective of this invention is to provide an electrical device.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A first aspect of the present invention provides an alloy reference electrode, the alloy reference electrode comprising a metallic material and an alloy layer located on the surface of the metallic material; The alloy layer contains alloy particles; The alloy particles are an alloy formed from one element selected from lithium, sodium, and potassium, and at least one element selected from aluminum, tin, bismuth, and antimony.

[0010] In some embodiments of the present invention, the thickness of the alloy layer is 40-60 μm.

[0011] In some embodiments of the present invention, the alloy layer is formed by the accumulation of alloy particles.

[0012] This invention improves the potential stability of an alloy reference electrode by forming an alloy layer on the surface of a metal material. The resulting alloy reference electrode can stably monitor the potential changes of the positive and negative electrodes of a three-electrode pouch cell during charge-discharge cycles, thereby improving the safety and reliability of the three-electrode pouch cell.

[0013] In some embodiments of the present invention, the metal material includes foamed metal or metal sheet.

[0014] In some embodiments of the present invention, the foam metal includes at least one of foamed aluminum, foamed tin, foamed bismuth, and foamed antimony.

[0015] In some embodiments of the present invention, the metal sheet includes at least one of aluminum, tin, bismuth, and antimony.

[0016] In some embodiments of the present invention, the metal material is a porous foam metal, and the alloy particles are loaded on the surface and / or within the pores of the foam metal.

[0017] In this invention, the alloy reference electrode is used as a reference electrode when measuring the potential of the positive or negative electrode in a three-electrode pouch cell. A cell is constructed by combining the electrode to be measured (e.g., the positive or negative electrode) with an alloy reference electrode whose electrode potential value is precisely known. By measuring the cell's electromotive force, the electrode potential of the electrode to be measured can be calculated. The electrode reaction occurring on the reference electrode must be a single, reversible reaction to ensure electrode potential stability and good reproducibility. This invention uses an alloy reference electrode as the reference electrode, which has a stable potential in lithium-ion batteries (sodium-ion or potassium-ion batteries) and can be used as a reference electrode to monitor the changes in positive and negative electrode voltages during long-cycle operation.

[0018] A second aspect of the present invention provides a method for preparing the alloy reference electrode described in the first aspect of the present invention, comprising the following steps: The metal materials, battery separator, first electrolyte, and electrodes are assembled into a battery, and then charge and discharge cycles are performed. The first electrolyte contains metal ions. During charge-discharge cycles, the metal ions in the first electrolyte undergo an alloying reaction with the metal material to obtain the reference electrode. The metal material is a reference electrode, and the electrode is the positive electrode and negative electrode of the battery; or, the metal material is the positive electrode of the battery, and the electrode is the negative electrode of the battery; or, the metal material is the negative electrode of the battery, and the electrode is the positive electrode of the battery.

[0019] In some embodiments of the present invention, the preparation method of the alloy reference electrode includes the following steps: assembling a metal material, a battery separator, a first electrolyte, and a battery positive electrode or a battery negative electrode into a two-electrode battery, and then performing charge-discharge cycles to allow the metal ions in the first electrolyte to undergo an alloying reaction with the metal material to obtain the reference electrode.

[0020] In some embodiments of the present invention, the preparation method of the alloy reference electrode includes the following steps: assembling a battery positive electrode, a first separator, a metal material, a second separator, a battery negative electrode, and a first electrolyte into a battery, and then performing charge-discharge cycles to allow the metal ions in the first electrolyte to undergo an alloying reaction with the metal material to obtain the reference electrode.

[0021] In this invention, the metal material undergoes an alloying reaction with metal ions (e.g., lithium ions, sodium ions, or potassium ions) in the electrolyte, forming an alloy layer or alloy particles on the surface of the metal material. The metal material not only undergoes an alloying reaction with metal ions (e.g., sodium ions, potassium ions, or lithium ions) in the first electrolyte, but also ensures the free migration of metal ions between the positive and negative electrodes of the battery.

[0022] In some embodiments of the present invention, in the method for preparing the alloy reference electrode, the positive electrode material of the battery positive electrode includes at least one of layered metal oxide material and graphite.

[0023] In some embodiments of the present invention, in the method for preparing the alloy reference electrode, the cathode material of the battery cathode includes LiCoO2, graphite, metal-doped lithium cobalt oxide, LiMnO2, LiNiO2, NMC series cathode materials, LiMn2O4, and LiMn. 1.5 M 0.5 O2, LiXPO4, and at least one of polyanionic cathode materials; LiXPO4 has an olivine structure.

[0024] In some embodiments of the present invention, the polyanionic cathode material is selected from at least one of LiNiPO4, LiMnPO4, LiCoPO4, Li3V2(PO4)2, Li2MSiO4, Li2Fe2(SO4)3, LiFeSO4F, and LiFeBO3.

[0025] In some embodiments of the present invention, LiMn 1.5 M 0.5 In O2, M is selected from at least one of Ni, Mg, Al, Cr, Zn, Ti, Fe, and Cu. LiMn2O4 and LiMn 1.5 M 0.5 All O2 particles have a cubic spinel structure.

[0026] In some embodiments of the present invention, in LiXPO4, X is selected from at least one of Fe, Mn, Co, and Ni.

[0027] In some embodiments of the present invention, the metal in the metal-doped lithium cobalt oxide material is selected from at least one of Mn, Al, Fe, and Cr.

[0028] In some embodiments of the present invention, the NMC series cathode material includes at least one of NMC811, NMC622, and NMC532.

[0029] In the method for preparing the alloy reference electrode, the negative electrode of the battery can be a commercially available metal electrode sheet or other commonly used electrode materials, including but not limited to lithium metal sheets, graphite, and Li4Ti5O. 12 Hard carbon anode, soft carbon anode, silicon anode, silicon-aluminum alloy, SnMC alloy anode, aluminum foil, tin foil, bismuth metal, antimony metal.

[0030] In some embodiments of the present invention, the first electrolyte includes a metal salt, a solvent, and an additive.

[0031] In some embodiments of the present invention, the solvent in the first electrolyte includes at least one selected from esters, sulfones, ethers, and nitriles. In some embodiments of the present invention, the solvent in the first electrolyte includes propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), methyl methyl carbonate (EMC), methyl propionate (MP), ethyl propionate (EP), ethyl acetate (EA), trimethyl phosphate (TMP), triethyl phosphate (TEP), triphenyl phosphate (TPP), tetrahydrofuran (THF), methyltetrahydrofuran (MeTHF), 2-methyltetrahydrofuran (2MeTHF), 1,3-dioxolane (DOL), and 4-methyl-1,3-dioxolane. At least one of the following: pentane (4MeDOL), dimethoxymethane (DMM), 1,2-dimethoxypropane (DMP), ethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether (G2), triethylene glycol dimethyl ether (G3), tetraethylene glycol dimethyl ether (G4), dimethyl sulfone (MSM), sulfolane (TMS), methyl ethyl sulfone (EMS), vinyl sulfite (ES), propylene sulfite (PS), dimethyl sulfite (DMS), diethyl sulfite (DES), acetonitrile (AN), adiponitrile (HN), N,N-dimethylformamide (DMF), and glutaronitrile (GLN).

[0032] In some embodiments of the present invention, the metal salt in the first electrolyte is a sodium salt, a lithium salt, or a potassium salt.

[0033] In some embodiments of the present invention, the lithium salt in the first electrolyte includes at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(perfluoroethylsulfonyl)imide (LiBETI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(oxalatoborate)borate (LiBOB), lithium (fluorosulfonyl)(perfluorobutylsulfonyl)imide (LiFNFSI), and lithium (trifluoromethanesulfonyl)(perfluorobutylsulfonyl)imide (LiTNFSI).

[0034] In some embodiments of the present invention, the sodium salt in the first electrolyte includes at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium perchlorate, sodium hexafluoroarsenate, sodium trifluoromethanesulfonate, sodium bis(trifluoromethanesulfonyl)imide, sodium bis(perfluoroethylsulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium bis(oxalatoborate), sodium (fluorosulfonyl)(perfluorobutylsulfonyl)imide, and sodium (trifluoromethanesulfonyl)(perfluorobutylsulfonyl)imide.

[0035] In some embodiments of the present invention, the potassium salt in the first electrolyte includes at least one of potassium hexafluorophosphate, potassium tetrafluoroborate, potassium perchlorate, potassium hexafluoroarsenate, potassium trifluoromethanesulfonate, bis(trifluoromethanesulfonyl)imide potassium, bis(perfluoroethylsulfonyl)imide potassium, bis(fluorosulfonyl)imide potassium, potassium bis(oxalatoborate), potassium (fluorosulfonyl)(perfluorobutylsulfonyl)imide potassium, and potassium (trifluoromethanesulfonyl)(perfluorobutylsulfonyl)imide potassium.

[0036] In some embodiments of the present invention, the additives in the first electrolyte include at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), propylene sulfite (PS), and ethylene sulfate (VEC).

[0037] In some embodiments of the present invention, the mass of the additive in the first electrolyte is 0.5-5% of the total mass of the metal salt and the solvent; in some embodiments of the present invention, the mass of the additive in the first electrolyte is 1-3% of the total mass of the metal salt and the solvent.

[0038] In some embodiments of the present invention, the concentration of the metal salt in the first electrolyte is 0.1-10 mol / L; in some embodiments of the present invention, the concentration of the metal salt in the first electrolyte is 0.5-6 mol / L; in some embodiments of the present invention, the concentration of the metal salt in the first electrolyte is 1-5 mol / L.

[0039] In some embodiments of the present invention, the first electrolyte is prepared in a glove box.

[0040] In some embodiments of the present invention, the first electrolyte is prepared under a protective atmosphere.

[0041] In some embodiments of the present invention, the protective atmosphere includes at least one of nitrogen, argon, helium, hydrogen, and a mixture of argon.

[0042] In some embodiments of the present invention, the volume fraction of hydrogen in the mixture of hydrogen and argon is 1-10%.

[0043] In some embodiments of the present invention, the material of the battery separator is selected from at least one of glass fiber, polyethylene, and polypropylene.

[0044] In some embodiments of the present invention, the battery separator is a polypropylene / polyethylene / polypropylene three-layer composite electrode.

[0045] In some embodiments of the present invention, the charging and discharging voltage in the method for preparing the alloy reference electrode is 3-5.2V. In some embodiments of the present invention, when the graphite positive electrode is connected to the aluminum negative electrode, the charging and discharging voltage in the method for preparing the alloy reference electrode is 3-5.2V.

[0046] In some embodiments of the present invention, the charging and discharging current density is 0.4-0.6 mA / cm². 2 .

[0047] In some embodiments of the present invention, the charge-discharge reaction cycle number is 8-12 times in the preparation method of the alloy reference electrode.

[0048] A third aspect of the present invention provides a three-electrode pouch cell, the three-electrode pouch cell comprising a three-electrode pouch cell positive electrode, a first separator, an alloy reference electrode as described in the first aspect of the present invention, a second separator, a three-electrode pouch cell negative electrode, and a second electrolyte.

[0049] Three-electrode pouch batteries are a new type of energy storage device with lower molding costs and higher safety. Unlike button batteries, which have smaller capacities and higher requirements for operating voltage and current, three-electrode pouch batteries have larger capacities, lower costs, and higher safety. Three-electrode pouch batteries can achieve higher capacities, making them more suitable for practical applications. Voltage changes throughout the entire charge-discharge process can be observed, unaffected by internal resistance. The changing trends of positive and negative electrode voltages under different cycles can be detected non-destructively. Monitoring the battery using a three-electrode pouch battery system is simple, low-cost, and easy to test.

[0050] In some embodiments of the present invention, the three-electrode pouch battery is a sodium-ion battery, a potassium-ion battery, or a lithium-ion battery.

[0051] In some embodiments of the present invention, the positive electrode material of the three-electrode soft-pack battery includes at least one of layered metal oxide material and graphite.

[0052] In some embodiments of the present invention, the positive electrode material of the three-electrode soft-pack battery includes LiCoO2, graphite, metal-doped lithium cobalt oxide, LiMnO2, LiNiO2, NMC series positive electrode materials, LiMn2O4, and LiMn. 1.5 M 0.5 O2, LiXPO4, and at least one of polyanionic cathode materials; LiXPO4 has an olivine structure.

[0053] In some embodiments of the present invention, the polyanionic cathode material is selected from at least one of LiNiPO4, LiMnPO4, LiCoPO4, Li3V2(PO4)2, Li2MSiO4, Li2Fe2(SO4)3, LiFeSO4F, and LiFeBO3.

[0054] In some embodiments of the present invention, LiMn 1.5 M 0.5 In O2, M is selected from at least one of Ni, Mg, Al, Cr, Zn, Ti, Fe, and Cu. LiMn2O4 and LiMn 1.5 M 0.5 All O2 particles have a cubic spinel structure.

[0055] In some embodiments of the present invention, in LiXPO4, X is selected from at least one of Fe, Mn, Co, and Ni.

[0056] In some embodiments of the present invention, the metal in the metal-doped lithium cobalt oxide material is selected from at least one of Mn, Al, Fe, and Cr.

[0057] In some embodiments of the present invention, the NMC series cathode material includes at least one of NMC811, NMC622, and NMC532.

[0058] In a three-electrode pouch cell, the negative electrode can be a commercially available metal electrode sheet or other commonly used electrode materials, including but not limited to lithium metal sheets, graphite, and Li4Ti5O. 12 Hard carbon anode, soft carbon anode, silicon anode, silicon-aluminum alloy, SnMC alloy anode, aluminum foil, tin foil, bismuth metal, antimony metal.

[0059] In some embodiments of the present invention, the second electrolyte includes a metal salt, a solvent, and an additive.

[0060] In some embodiments of the present invention, the solvent in the second electrolyte includes at least one selected from esters, sulfones, ethers, and nitriles. In some embodiments of the present invention, the solvent in the second electrolyte includes propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), methyl ethyl carbonate (EMC), methyl propionate (MP), ethyl propionate (EP), ethyl acetate (EA), trimethyl phosphate (TMP), triethyl phosphate (TEP), triphenyl phosphate (TPP), tetrahydrofuran (THF), methyltetrahydrofuran (MeTHF), 2-methyltetrahydrofuran (2MeTHF), 1,3-dioxolane (DOL), and 4-methyl-1,3-dioxolane. At least one of the following: pentane (4MeDOL), dimethoxymethane (DMM), 1,2-dimethoxypropane (DMP), ethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether (G2), triethylene glycol dimethyl ether (G3), tetraethylene glycol dimethyl ether (G4), dimethyl sulfone (MSM), sulfolane (TMS), methyl ethyl sulfone (EMS), vinyl sulfite (ES), propylene sulfite (PS), dimethyl sulfite (DMS), diethyl sulfite (DES), acetonitrile (AN), adiponitrile (HN), N,N-dimethylformamide (DMF), and glutaronitrile (GLN).

[0061] In some embodiments of the present invention, the metal salt in the second electrolyte is a sodium salt, lithium salt, or potassium salt.

[0062] In some embodiments of the present invention, the lithium salt in the second electrolyte includes at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(perfluoroethylsulfonyl)imide (LiBETI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(oxalatoborate)borate (LiBOB), lithium (fluorosulfonyl)(perfluorobutylsulfonyl)imide (LiFNFSI), and lithium (trifluoromethanesulfonyl)(perfluorobutylsulfonyl)imide (LiTNFSI).

[0063] In some embodiments of the present invention, the sodium salt in the second electrolyte includes at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium perchlorate, sodium hexafluoroarsenate, sodium trifluoromethanesulfonate, sodium bis(trifluoromethanesulfonyl)imide, sodium bis(perfluoroethylsulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium bis(oxalatoborate), sodium (fluorosulfonyl)(perfluorobutylsulfonyl)imide, and sodium (trifluoromethanesulfonyl)(perfluorobutylsulfonyl)imide.

[0064] In some embodiments of the present invention, the potassium salt in the second electrolyte includes at least one of potassium hexafluorophosphate, potassium tetrafluoroborate, potassium perchlorate, potassium hexafluoroarsenate, potassium trifluoromethanesulfonate, potassium bis(trifluoromethanesulfonyl)imide, potassium bis(perfluoroethylsulfonyl)imide, potassium bisfluorosulfonylimide, potassium bis(oxalatoborate), potassium (fluorosulfonyl)(perfluorobutylsulfonyl)imide, and potassium (trifluoromethanesulfonyl)(perfluorobutylsulfonyl)imide.

[0065] In some embodiments of the present invention, the additives in the second electrolyte include at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), propylene sulfite (PS), and ethylene sulfate (VEC).

[0066] In some embodiments of the present invention, the mass of the additive in the second electrolyte is 0.5-5% of the total mass of the metal salt and the solvent; in some embodiments of the present invention, the mass of the additive in the second electrolyte is 1-3% of the total mass of the metal salt and the solvent.

[0067] In some embodiments of the present invention, the concentration of the metal salt in the second electrolyte is 0.1-10 mol / L; in some embodiments of the present invention, the concentration of the metal salt in the second electrolyte is 0.5-6 mol / L; in some embodiments of the present invention, the concentration of the metal salt in the second electrolyte is 1-5 mol / L.

[0068] In some embodiments of the present invention, the second electrolyte is prepared in a glove box.

[0069] In some embodiments of the present invention, the second electrolyte is prepared under a protective atmosphere.

[0070] In some embodiments of the present invention, the protective atmosphere includes at least one of nitrogen, argon, helium, hydrogen, and a mixture of argon.

[0071] In some embodiments of the present invention, the volume fraction of hydrogen in the mixture of hydrogen and argon is 1-10%.

[0072] In some embodiments of the present invention, the material of the first diaphragm is selected from at least one of glass fiber, polyethylene, and polypropylene.

[0073] In some embodiments of the present invention, the material of the second diaphragm is selected from at least one of glass fiber, polyethylene, and polypropylene.

[0074] In some embodiments of the present invention, the first diaphragm is a polypropylene / polyethylene / polypropylene three-layer composite electrode.

[0075] In some embodiments of the present invention, the second diaphragm is a polypropylene / polyethylene / polypropylene three-layer composite electrode.

[0076] A fourth aspect of the present invention provides a method for preparing the three-electrode pouch cell described in the third aspect of the present invention, wherein the method for preparing the three-electrode pouch cell is either method one or method two. The first method includes the following steps: The positive electrode of the three-electrode soft-pack battery, the first separator, the metal material, the second separator, the negative electrode of the three-electrode soft-pack battery, and the second electrolyte are assembled into a three-electrode soft-pack battery pack. The positive or negative electrode of the three-electrode soft-pack battery is electrically connected to the metal material, and then charge-discharge cycles are performed to allow the metal ions in the second electrolyte to undergo an alloying reaction with the metal material. The three-electrode soft-pack battery is prepared by connecting the positive electrode of the three-electrode soft-pack battery to the negative electrode of the three-electrode soft-pack battery. The second method includes the following steps: The positive electrode of the three-electrode soft-pack battery, the first separator, the alloy reference electrode described in the first aspect of the present invention, the second separator, the negative electrode of the three-electrode soft-pack battery, and the second electrolyte are assembled into a three-electrode soft-pack battery pack.

[0077] In this invention, the three-electrode pouch battery is prepared using two methods. The first method involves directly fabricating the three-electrode pouch battery. In the fabricated pouch battery, a reference electrode (i.e., a metal material) is first cyclically exchanged with either the positive or negative electrode to form a reference electrode (foam alloy or alloy) with a stable potential. Then, charge-discharge cycles are performed on the positive and negative electrodes, and the potential changes at the positive and negative electrodes are monitored using the reference electrode. The second method involves first fabricating a reference electrode by cyclically exchanging the foam metal (metal) with either the positive or negative electrode material several times within a two-electrode pouch battery to obtain a foam alloy (alloy). This foam alloy (alloy) is then removed. The three-electrode pouch battery is assembled in the following order: positive electrode, separator, reference electrode (foam alloy or alloy), separator, and negative electrode. Finally, it is sealed with an aluminum-plastic film to obtain the lithium-ion three-electrode pouch battery.

[0078] In some embodiments of the present invention, the preparation method of the three-electrode soft-pack battery includes the following steps: encapsulating the positive electrode, the first separator, the metal material, the second separator, and the negative electrode of the three-electrode soft-pack battery with an aluminum-plastic film, and then injecting the second electrolyte to assemble a three-electrode soft-pack battery pack. The positive or negative electrode of the three-electrode soft-pack battery is electrically connected to the metal material, and then charge-discharge cycles are performed to allow the metal ions in the second electrolyte to undergo an alloying reaction with the metal material. The three-electrode pouch cell is prepared by connecting the positive electrode of the three-electrode pouch cell to the negative electrode of the three-electrode pouch cell.

[0079] In some embodiments of the present invention, the preparation method of the three-electrode soft-pack battery includes the following steps: assembling the battery cells in the order of the positive electrode, the first separator, the alloy reference electrode described in the first aspect of the present invention, the second separator, and the negative electrode of the three-electrode soft-pack battery; then encapsulating them with an aluminum-plastic film; and finally injecting a second electrolyte to assemble a three-electrode soft-pack battery pack. In some embodiments of the present invention, the preparation method of the three-electrode soft-pack battery includes the following steps: assembling the battery cells in the order of the positive electrode, the first separator, the alloy reference electrode described in the first aspect of the present invention, the second separator, and the negative electrode of the three-electrode soft-pack battery; then encapsulating them with an aluminum-plastic film; drying them; then placing them in a glove box and injecting a second electrolyte; sealing them to obtain a three-electrode soft-pack battery pack. The second electrolyte is injected to completely wet the first and second separators; the amount of the second electrolyte needs to meet the requirements of battery cycling; and then sealing is performed.

[0080] In this invention, the first electrolyte and the second electrolyte can be the same or different. The materials of the first diaphragm and the second diaphragm can be the same or different.

[0081] In some embodiments of the present invention, the drying temperature is 110-130°C.

[0082] In some embodiments of the present invention, the drying time is 60-80 hours.

[0083] In some embodiments of the present invention, the aluminum-plastic film comprises a nylon layer, an aluminum foil layer, and a heat-sealing layer stacked together. The nylon layer, aluminum foil layer, and heat-sealing layer are all bonded together using adhesives. The nylon layer is located on the outermost layer to reduce external force, the middle layer is the aluminum foil layer, and the heat-sealing layer is near the innermost layer; each layer is bonded together with adhesives. The aluminum-plastic film possesses extremely high barrier properties, good cold-stamping formability, puncture resistance, electrolyte stability, high-temperature resistance, and insulation properties.

[0084] In some embodiments of the present invention, the charging and discharging voltage in the preparation method of the three-electrode pouch battery is 3-5.2V. In some embodiments of the present invention, when the graphite positive electrode is connected to the aluminum negative electrode, the charging and discharging voltage in the preparation method of the three-electrode pouch battery is 3-5.2V.

[0085] A fifth aspect of the present invention provides an electrical device comprising the three-electrode pouch battery described in the third aspect of the present invention.

[0086] The beneficial effects of this invention are as follows: The alloy reference electrode of this invention has a stable potential, does not dissolve in the electrolyte at high temperatures, and does not chemically react with the electrolyte. When applied to a three-electrode pouch cell, it allows observation of the potential changes of each electrode (i.e., the positive or negative electrode of the three-electrode pouch cell) during the entire battery's charge and discharge process. It enables non-destructive monitoring of individual electrodes during charge and discharge cycles, providing stable and reliable monitoring results. It can be used for monitoring the positive and negative electrode voltages of long-cycle batteries, offering advantages such as simple operation, low cost, and ease of testing. Furthermore, the alloy reference electrode of this invention does not interfere with electrical signals, ensuring the accuracy of the monitoring data.

[0087] The three-electrode soft-pack battery of the present invention introduces an alloy reference electrode that does not react with the second electrolyte and has a fixed potential. During the long cycle of the battery, the voltage changes of the positive and negative electrodes throughout the entire charge and discharge process can be monitored non-destructively without being affected by internal resistance. Furthermore, the influence of the positive and negative electrodes on the cell can be separated to observe the individual changes of the positive and negative electrodes. It has the advantages of simple operation, low cost, and easy testing. Attached Figure Description

[0088] Figure 1 This is a schematic diagram of the structure of the three-electrode soft-pack battery in Example 1, where 1 and 7 are aluminum-plastic films, 2 is the positive electrode, 3 is the first separator, 4 is the reference electrode, 5 is the second separator, and 6 is the negative electrode.

[0089] Figure 2 This is a schematic diagram of the internal structure of the three-electrode pouch cell in Example 1.

[0090] Figure 3 This is a voltage-time test graph of the three-electrode pouch cell in Example 1.

[0091] Figure 4 The voltage-time test graph is for the three-electrode pouch cell in Comparative Example 1.

[0092] Figure 5 This is a potential diagram of the lithium-aluminum alloy in Example 1.

[0093] Figure 6 The image shows the XRD pattern of the lithium-aluminum alloy in Example 1.

[0094] Figure 7 This is a potential difference test diagram between the graphite positive electrode and the reference electrode in the three-electrode pouch cell of Example 1.

[0095] Figure 8This is a potential difference test diagram between the graphite positive electrode and the reference electrode in the three-electrode pouch cell of Comparative Example 2.

[0096] Figure 9 The image shows a cross-sectional SEM image of the lithium-aluminum reference electrode alloy layer after charging in Example 1.

[0097] Figure 10 This is a cross-sectional SEM image of the lithium-aluminum reference electrode alloy layer after discharge in Example 1.

[0098] Figure 11 The image shows the SEM image of the lithium-aluminum reference electrode synthesized in Example 1 before it was immersed in a high-concentration lithium hexafluorophosphate electrolyte of 4 mol / L for 72 hours.

[0099] Figure 12 The image shows a SEM image of the lithium-aluminum reference electrode synthesized in Example 1 after immersion in a high-concentration lithium hexafluorophosphate electrolyte of 4 mol / L for 72 hours.

[0100] Figure 13 The image shows the nominal stress-displacement curve of the lithium-aluminum reference electrode synthesized in Example 1. Detailed Implementation

[0101] The specific implementation of the present invention will be further described in detail below with reference to the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that any processes not specifically described in detail below are those that can be implemented or understood by those skilled in the art by referring to the prior art. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0102] Example 1 This example provides a method for fabricating a three-electrode pouch cell. A schematic diagram of the resulting three-electrode pouch cell is shown below. Figure 1 As shown in the diagram, the internal structure of a three-electrode pouch cell is as follows: Figure 2 As shown.

[0103] The specific steps of the preparation method in this example are as follows: (1) A traditional two-electrode soft-pack battery was assembled by combining a graphite cathode with metallic aluminum. The battery was then charged and discharged to obtain a lithium-aluminum alloy with a stable potential, serving as the reference electrode. The charge / discharge voltage was 3-5.2V, the cycle count was 10, and the constant current discharge density was 0.5 mA / cm². 2 The electrolyte is a 4 mol / L lithium hexafluorophosphate electrolyte, which is prepared by dissolving lithium hexafluorophosphate in ethyl methyl carbonate (EMC) to prepare a 4 mol / L solution, and then adding 2% vinylene carbonate (VC, as an additive) of the total mass of ethyl methyl carbonate and lithium hexafluorophosphate to obtain a lithium-aluminum alloy, which is used as a reference electrode.

[0104] (2) The positive electrode tab is welded to the positive electrode plate with tab adhesive, and the negative electrode tab is welded to the negative electrode plate.

[0105] (3) Seal the positive electrode 2, the first separator 3, the lithium aluminum alloy 4 (i.e. the reference electrode in step 1), the second separator 5, and the negative electrode 6 in an aluminum-plastic film in sequence. The positive electrode is made of graphite electrode sheet (the positive electrode material is graphite), and the negative electrode is made of graphite electrode sheet. Leave a gas chamber to obtain a three-electrode soft pack battery pack. The first separator and the second separator are made of the same material, which is a thick glass fiber separator.

[0106] (4) Place the prepared three-electrode soft-pack battery pack in an oven at 120°C for 72 hours, seal it and place it in a glove box.

[0107] (5) Weigh 4 mol of lithium hexafluorophosphate in the glove box, add it to ethyl methyl carbonate (EMC) to dissolve, and then make up to 1 L. At the same time, add 2% of vinylene carbonate (VC, as an additive) of the total mass of (lithium hexafluorophosphate and ethyl methyl carbonate), stir evenly, and prepare a 4 mol / L lithium hexafluorophosphate electrolyte.

[0108] (6) Inject the prepared electrolyte into the three-electrode soft-pack battery to make it completely wetted, and finally complete the assembly of the three-electrode soft-pack battery by encapsulation.

[0109] Examples 2-9 The only difference between the preparation method of the three-electrode soft-pack battery in Examples 2-9 and Example 1 is that the positive electrode material in step (3) is different. The positive electrode materials in Examples 2-9 are LiCoO2, LiMnO2, LiNiO2, NMC811, NMC622, NMC532, LiMn2O4, and LiFePO4, respectively.

[0110] Examples 10-12 The only difference between the preparation method of the three-electrode soft-pack battery in Examples 10-12 and Example 1 is that the negative electrode in step (3) is different. The negative electrodes in Examples 10-12 are lithium sheet, silicon negative electrode and silicon-aluminum alloy in sequence.

[0111] Examples 13-17 The only difference between the preparation method of the three-electrode soft-pack battery in Examples 13-17 and Example 1 is that the lithium salt in the electrolyte in step (5) is different from that in Example 1. The lithium salts in the electrolyte of Examples 13-17 are lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bisfluorosulfonylimide (LiFSI), and lithium bis(oxalateborate)borate (LiBOB).

[0112] Examples 18-34 The preparation method of the three-electrode soft-pack battery in Examples 18-34 differs from that in Example 1 only in that the solvent in the electrolyte in step (5) is different from that in Example 1. The solvents in the electrolytes of Examples 18-34 are, in order, propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), methyl propionate (MP), ethyl acetate (EA), trimethyl phosphate (TMP), triethyl phosphate (TEP), tetrahydrofuran (THF), methyl tetrahydrofuran (MeTHF), 2-methyltetrahydrofuran (2MeTHF), 1,3-dioxolane (DOL), 4-methyl-1,3-dioxolane (4MeDOL), diethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether (G2), triethylene glycol dimethyl ether (G3), and tetraethylene glycol dimethyl ether (G4).

[0113] Examples 35-43 The preparation method of the three-electrode soft-pack battery in Examples 35-43 differs from that in Example 1 only in that the solvent in the electrolyte in step (5) is different from that in Example 1. The solvents in the electrolytes of Examples 35-43 are, in order, the solvents in the electrolytes of Examples 35-43. DMC:EC:EMC=1:1:1(v:v:v)、DEC:EC=1:1(v:v)、DMC:EC=1:1(v:v)、DEC:DMC:EC=1:1:1(v:v:v)、DEC:EC:E MC=1:1:1(v:v:v), EC:EMC=3:7(v:v), DEC:EC:EMC=1:1:1(v:v:v), EC:EMC=3:7(v:v), DMC:EC=7:3(v:v).

[0114] EMC stands for ethyl methyl carbonate.

[0115] Examples 44-47 The only difference between the preparation methods of the three-electrode soft-pack batteries in Examples 44-47 and Example 1 is that the concentration of lithium salt in step (5) is different. The lithium salt concentrations in Examples 44-47 are 1 mol / L, 2 mol / L, 3 mol / L and 5 mol / L, respectively.

[0116] Examples 48-50 The only difference between the preparation method of the three-electrode soft-pack battery in Examples 48-50 and Example 1 is that the types of additives in step (5) are different. The additives in Examples 48-50 are fluoroethylene carbonate (FEC), propylene sulfite (PS), and ethylene sulfate (VEC) in sequence.

[0117] Example 51 This example provides a method for preparing a three-electrode pouch cell, the specific steps of which are as follows: (1) The positive electrode tab is welded to the positive electrode plate with tab adhesive, and the negative electrode tab is welded to the negative electrode plate.

[0118] (2) The positive electrode, the first separator, the aluminum foam, the second separator, and the negative electrode are sealed in an aluminum-plastic film in sequence. The positive electrode uses a graphite electrode sheet (i.e., the positive electrode material is graphite) and the negative electrode uses a graphite electrode sheet. An air chamber is left to obtain a three-electrode soft-pack battery pack. The first separator and the second separator are made of the same material, which is a glass fiber thin separator.

[0119] (3) Place the prepared three-electrode soft-pack battery pack in an oven at 120°C for 72 hours, seal it and place it in a glove box.

[0120] (4) Weigh 1 mol of lithium hexafluorophosphate in a glove box, add it to ethyl methyl carbonate (EMC) to dissolve, and then make up to 1 L. At the same time, add 2% VC (as an additive) of the total mass of lithium hexafluorophosphate and ethyl methyl carbonate, stir evenly, and prepare a 1 mol / L lithium hexafluorophosphate electrolyte. Let it stand for twelve hours to obtain the electrolyte.

[0121] (5) Inject the prepared electrolyte into the three-electrode soft-pack battery to completely wet it, and finally complete the assembly of the three-electrode soft-pack battery by encapsulation.

[0122] (6) Connect the graphite positive electrode to the aluminum foam and obtain a lithium-aluminum alloy with a stable potential, i.e., a reference electrode, by charge-discharge cycling at a voltage of 3-5.2V. The charge-discharge voltage is 3-5.2V and the constant current discharge current density is 0.5 mA / cm². 2 Finally, the positive electrode is connected to the negative electrode, and the negative electrode is connected to the lithium aluminum alloy reference electrode. Only the channel between the positive and negative electrodes has current, while the other two channels are used to detect the electrode potential.

[0123] Examples 52-59 The only difference between the preparation method of the three-electrode soft-pack battery in Examples 52-59 and that in Example 51 is that the positive electrode material in step (2) is different. Specifically, the positive electrode materials in Examples 52-59 are LiCoO2, LiMnO2, LiNiO2, NMC811, NMC622, NMC532, LiMn2O4, and LiFePO4 in sequence.

[0124] Examples 60-62 The only difference between the preparation method of the three-electrode soft-pack battery in Examples 60-62 and that in Example 51 is that the negative electrode in step (2) is different. Specifically, the negative electrodes in Examples 60-62 are lithium sheet, silicon negative electrode, and silicon-aluminum alloy in sequence.

[0125] Examples 63-67 The only difference between the preparation method of the three-electrode soft-pack battery in Examples 63-67 and that in Example 51 is that the lithium salt in the electrolyte in step (4) is different. Specifically, the lithium salts in Examples 63-67 are lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bisfluorosulfonylimide (LiFSI), and lithium bis(oxalateborate)borate (LiBOB).

[0126] Examples 68-84 The preparation method of the three-electrode soft-pack battery in Examples 68-84 differs from that in Example 51 only in that the solvent in the electrolyte in step (4) is different. The solvents in the electrolyte in step (4) of Examples 68-84 are, in order, propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), methyl propionate (MP), ethyl acetate (EA), trimethyl phosphate (TMP), triethyl phosphate (TEP), tetrahydrofuran (THF), methyl tetrahydrofuran (MeTHF), 2-methyltetrahydrofuran (2MeTHF), 1,3-dioxolane (DOL), 4-methyl-1,3-dioxolane (4MeDOL), diethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether (G2), triethylene glycol dimethyl ether (G3), and tetraethylene glycol dimethyl ether (G4).

[0127] Examples 85-93 The only difference between the preparation method of the three-electrode soft-pack battery in Examples 85-93 and that in Example 51 is that the solvent in the electrolyte in step (4) is a mixed solvent. The solvents in the electrolyte in Examples 85-93 are DMC:EC:EMC=1:1:1(v:v:v), DEC:EC=1:1(v:v), DMC:EC=1:1(v:v), DEC:DMC:EC=1:1:1(v:v:v), DEC:EC:EMC=1:1:1(v:v:v), EC:EMC=3:7(v:v), DEC:EC:EMC=1:1:1(v:v:v), EC:EMC=3:7(v:v), and DMC:EC=7:3(v:v).

[0128] Examples 94-97 The only difference between the preparation methods of the three-electrode soft-pack batteries in Examples 94-97 and those in Example 51 is that the concentration of the electrolyte in step (4) is different. The lithium salt concentrations of the electrolytes in Examples 94-97 are 2 mol / L, 3 mol / L, 4 mol / L, and 5 mol / L, respectively.

[0129] Examples 98-100 The only difference between the preparation method of the three-electrode soft-pack battery in Examples 98-100 and that in Example 51 is that the additives used in the electrolyte in step (4) are different. The additives used in the electrolyte in Examples 98-100 are fluoroethylene carbonate (FEC), propylene sulfite (PS), and ethylene sulfate (VEC) in sequence.

[0130] Example 101 This example provides a method for preparing a three-electrode pouch cell, the specific steps of which are as follows: (1) A traditional two-electrode soft-pack battery is assembled by combining a hard carbon negative electrode with metallic tin. The charge / discharge voltage is 3-5.2V, and the constant current discharge current density is 0.5 mA / cm². 2 The electrolyte is a 1 mol / L sodium hexafluorophosphate electrolyte, which is prepared by dissolving 1 mol of sodium hexafluorophosphate in ethyl methyl carbonate (EMC), bringing the volume to 1 L, and adding 2% vinylene carbonate (VC, as an additive) of the total mass of sodium hexafluorophosphate and ethyl methyl carbonate, stirring until homogeneous; thus, a sodium-tin alloy with a stable potential is obtained, which is the reference electrode.

[0131] (2) The positive electrode tab is welded to the positive electrode plate with tab adhesive, and the negative electrode tab is welded to the negative electrode plate.

[0132] (3) The positive electrode, the first separator, the sodium-tin alloy (i.e. the reference electrode), the second separator, and the hard carbon negative electrode are sequentially sealed in an aluminum-plastic film. The positive electrode uses a sodium nickel iron manganese oxide electrode sheet (i.e., the positive electrode material is sodium nickel iron manganese oxide). A gas chamber is left open to obtain a three-electrode soft-pack battery pack. The first separator and the second separator are made of the same material, which is a thick glass fiber separator.

[0133] (4) Place the prepared three-electrode soft-pack battery pack in an oven at 120°C for 72 hours, seal it and place it in a glove box.

[0134] (5) Weigh 1 mol of sodium hexafluorophosphate in the glove box, add it to ethyl methyl carbonate (EMC) to dissolve, and then make up to 1 L. At the same time, add 2% VC (as an additive) of the total mass of ethyl methyl carbonate and sodium hexafluorophosphate, stir well, and prepare a 1 mol / L sodium hexafluorophosphate electrolyte.

[0135] (6) Inject the prepared electrolyte into the three-electrode soft-pack battery to make it completely wetted, and finally complete the assembly of the three-electrode soft-pack battery by encapsulation.

[0136] Examples 102-109 The preparation methods of the three-electrode soft-pack batteries in Examples 102-109 differ from those in Example 101 only in that the positive electrode material in step (3) is different. The positive electrode materials in Examples 102-109 are NaCoO2, NaMnO2, NaNiO2, and Na...2 / 3 [Fe 1 / 2 Mn 1 / 2 ]O2, Na3V2(PO4)3, NaFePO4, Na2Mn[Fe(CN)6], Na2FePO4F.

[0137] Examples 110-112 The only difference between the preparation method of the three-electrode soft-pack battery in Examples 110-112 and that in Example 101 is that the negative electrode in step (3) is different. The negative electrodes in Examples 110-112 are sodium sheet, silicon negative electrode, and silicon-aluminum alloy, respectively.

[0138] Examples 113-117 The preparation method of the three-electrode soft-pack battery in Examples 113-117 differs from that in Example 101 only in that the sodium salt in the electrolyte in step (5) is different. The sodium salt in the electrolyte of Examples 113-117 is sodium tetrafluoroborate (NaBF4), sodium perchlorate (NaClO4), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium bis(fluorosulfonyl)imide (NaFSI), and sodium bis(oxalateborate)borate (NaBOB).

[0139] Examples 118-134 The preparation method of the three-electrode soft-pack battery in Examples 118-134 differs from that in Example 101 only in that the solvent in the electrolyte in step (5) is different. The solvents in the electrolytes of Examples 118-134 are, in order, propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), methyl propionate (MP), ethyl acetate (EA), trimethyl phosphate (TMP), triethyl phosphate (TEP), tetrahydrofuran (THF), methyl tetrahydrofuran (MeTHF), 2-methyltetrahydrofuran (2MeTHF), 1,3-dioxolane (DOL), 4-methyl-1,3-dioxolane (4MeDOL), diethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether (G2), triethylene glycol dimethyl ether (G3), and tetraethylene glycol dimethyl ether (G4).

[0140] Examples 135-143 The difference between the preparation method of the three-electrode soft-pack battery in Examples 135-143 and that in Example 101 is that the solvent in the electrolyte in step (5) is a mixed solvent. The solvents in the electrolytes of Examples 135-143 are DMC:EC:EMC=1:1:1(v:v:v), DEC:EC=1:1(v:v), DMC:EC=1:1(v:v), DEC:DMC:EC=1:1:1(v:v:v), DEC:EC:EMC=1:1:1(v:v:v), EC:EMC=3:7(v:v), DEC:EC:EMC=1:1:1(v:v:v), EC:EMC=3:7(v:v), and DMC:EC=7:3(v:v).

[0141] Examples 144-147 The only difference between the preparation method of the three-electrode soft-pack battery in Examples 144-147 and that in Example 101 is that the sodium salt concentration of the electrolyte in step (5) is different. The sodium salt concentrations of the electrolyte in Examples 144-147 are 2 mol / L, 3 mol / L, 4 mol / L and 5 mol / L, respectively.

[0142] Examples 148-150 The only difference between the preparation method of the three-electrode soft-pack battery in Examples 148-150 and that in Example 101 is that the additives in the electrolyte in step (5) are different. The additives in Examples 148-150 are, in order: fluoroethylene carbonate (FEC), propylene sulfite (PS), and ethylene sulfate (VEC).

[0143] Example 151 This example provides a method for preparing a three-electrode pouch cell, the specific steps of which are as follows: (1) The positive electrode tab is welded to the positive electrode plate with tab adhesive, and the negative electrode tab is welded to the negative electrode plate.

[0144] (2) Seal the positive electrode, the first separator, the foamed tin, the second separator, and the hard carbon negative electrode in an aluminum-plastic film in sequence. The positive electrode uses a sodium nickel iron manganese oxide electrode sheet (the positive electrode material is sodium nickel iron manganese oxide), and the negative electrode uses a hard carbon electrode sheet. Leave a gas chamber to obtain a three-electrode soft-pack battery pack. The first separator and the second separator are made of the same material, which is a glass fiber thin separator.

[0145] (3) Place the prepared three-electrode soft-pack battery pack in an oven and dry it at 120°C for 72 hours. Seal it and put it in a glove box.

[0146] (4) Weigh 1 mol of sodium hexafluorophosphate in the glove box, add it to ethyl methyl carbonate (EMC) to dissolve, and then make up to 1 L. At the same time, add 2% VC (as an additive) of the total mass of sodium hexafluorophosphate and ethyl methyl carbonate, stir evenly, and prepare a 1 mol / L sodium hexafluorophosphate electrolyte. Let it stand for twelve hours.

[0147] (5) Inject the prepared electrolyte into the three-electrode soft-pack battery to completely wet it, and finally complete the assembly of the three-electrode soft-pack battery by encapsulation.

[0148] (6) Connect the positive electrode to the foamed tin, and charge and discharge it at a voltage of 3-5.2V, with a constant current discharge current density of 0.5 mA / cm². 2 A sodium-tin alloy with a stable potential is obtained, which serves as the reference electrode. Finally, the positive electrode is connected to the negative electrode, and the negative electrode is connected to the sodium-tin alloy reference electrode. Only the channel between the positive and negative electrodes carries current, while the other two channels are used to detect the electrode potential.

[0149] Examples 152-159 The preparation method of the three-electrode soft-pack battery in Examples 152-159 differs from that in Example 151 only in that the positive electrode material in step (2) is different. The positive electrode materials in Examples 152-159 are NaCoO2, NaMnO2, NaNiO2, and Na... 2 / 3 [Fe 1 / 2 Mn 1 / 2 ]O2, Na3V2(PO4)3, NaFePO4, Na2Mn[Fe(CN)6], Na2FePO4F.

[0150] Examples 160-162 The only difference between the preparation method of the three-electrode soft-pack battery in Examples 160-162 and that in Example 151 is that the negative electrode in step (2) is different. The negative electrodes in Examples 160-162 are sodium sheet, silicon negative electrode, and silicon-aluminum alloy, respectively.

[0151] Examples 163-167 The preparation method of the three-electrode soft-pack battery in Examples 163-167 differs from that in Example 151 only in that the sodium salt in the electrolyte in step (4) is different. The sodium salts in Examples 163-167 are sodium tetrafluoroborate (NaBF4), sodium perchlorate (NaClO4), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium bis(fluorosulfonyl)imide (NaFSI), and sodium bis(oxalateborate)borate (NaBOB).

[0152] Examples 168-184 The preparation method of the three-electrode soft-pack battery in Examples 168-184 differs from that in Example 151 only in that the solvent in the electrolyte in step (4) is different. The solvents in Examples 168-184 are, in order, propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), methyl propionate (MP), ethyl acetate (EA), trimethyl phosphate (TMP), triethyl phosphate (TEP), tetrahydrofuran (THF), methyl tetrahydrofuran (MeTHF), 2-methyltetrahydrofuran (2MeTHF), 1,3-dioxolane (DOL), 4-methyl-1,3-dioxolane (4MeDOL), dimethyl ethylene glycol (DME), diethylene glycol (G2), triethylene glycol (G3), and tetraethylene glycol (G4).

[0153] Examples 185-193 The difference between the preparation method of the three-electrode soft-pack battery in Examples 185-193 and that in Example 151 is that the solvent in the electrolyte in step (4) is a mixed solvent. The solvents in Examples 185-193 are DMC:EC:EMC=1:1:1(v:v:v), DEC:EC=1:1(v:v), DMC:EC=1:1(v:v), DEC:DMC:EC=1:1:1(v:v:v), DEC:EC:EMC=1:1:1(v:v:v), EC:EMC=3:7(v:v), DEC:EC:EMC=1:1:1(v:v:v), EC:EMC=3:7(v:v), and DMC:EC=7:3(v:v).

[0154] Examples 194-197 The only difference between the preparation method of the three-electrode soft-pack battery in Examples 194-197 and that in Example 151 is that the concentration of sodium salt in the electrolyte in step (4) is different. The concentrations of sodium salt in Examples 194-197 are 2 mol / L, 3 mol / L, 4 mol / L and 5 mol / L, respectively.

[0155] Examples 198-200 The only difference between the preparation method of the three-electrode soft-pack battery in Examples 198-200 and that in Example 151 is that the additives in the electrolyte in step (4) are different. The additives in Examples 198-200 are fluoroethylene carbonate (FEC), propylene sulfite (PS), and ethylene sulfate (VEC) in sequence.

[0156] Comparative Example 1 The only difference between the preparation method of the three-electrode soft-pack battery in this example and that in Example 1 is that lithium metal (as a reference electrode) is used instead of the lithium-aluminum alloy in Example 1, while the other parameters and steps are the same as in Example 1.

[0157] Comparative Example 2 This example provides a method for preparing a three-electrode pouch cell, the specific steps of which are as follows: Step 1: Provide a copper wire with a diameter D of 50μm as a prefabricated electrode. Stack the positive electrode, separator, prefabricated electrode, separator and negative electrode in sequence and then laminate them to form a prefabricated battery cell. Both the positive and negative electrodes are graphite electrodes.

[0158] Step 2: The prefabricated cells are encapsulated using aluminum-plastic film, followed by high-temperature baking, electrolyte injection, vacuum sealing, settling, formation, and capacity testing to obtain a single soft-pack prefabricated battery.

[0159] Step 3: Using a charge-discharge device, charge the positive electrode and copper wire with a current of 20 μA for 4 hours, then charge the negative electrode and copper wire with a current of 20 μA for 4 hours to obtain the reference electrode. At this time, after activation, elemental lithium is formed on the surface of the copper wire. The thickness of the elemental lithium on the surface of the copper wire is measured to be 5 μm. The copper wire with elemental lithium attached at this time is the reference electrode, resulting in a three-electrode soft-pack battery.

[0160] Performance testing: The voltage change over time of the three-electrode pouch cells in Example 1 and Comparative Example 1 was tested under the following conditions: positive and negative electrode charge / discharge voltages of 3-5.2V, and constant current 1C charge / discharge. Specifically... Figure 3 and Figure 4 As shown. By Figure 3-4 It can be seen that the potential difference curves between the positive and negative electrodes and the lithium-aluminum alloy reference electrode in Example 1 are significantly different from those of the conventional lithium metal reference electrode (Comparative Example 1), and remain stable, indicating that the alloy reference electrode of the present invention is different from the conventional reference electrode and has good performance.

[0161] The potential diagram of the lithium-aluminum alloy prepared in Example 1 is shown in the figure below. Figure 5 As shown, the charging current density is 0.5 mA / cm². 2 As time goes on, the potential of the lithium-aluminum alloy remains basically unchanged, proving that the lithium-aluminum alloy prepared in Example 1 of this invention has a stable potential. When the lithium-aluminum alloy is used as a reference electrode that does not participate in the electrochemical reaction, it has an even greater advantage in potential stability.

[0162] The XRD pattern of the lithium-aluminum alloy in Example 1 was measured using an X-ray diffractometer, as shown below. Figure 6 As shown. By Figure 6As can be seen, in Example 1 of the present invention, a lithium-aluminum alloy was successfully synthesized, in which lithium and aluminum exist in the form of an alloy rather than in the form of elemental lithium.

[0163] The potential difference change between the graphite positive electrode and the reference electrode in the three-electrode pouch cells of Example 1 and Comparative Example 2 were tested respectively. The test conditions were: positive and negative electrode charge / discharge voltage of 3-5.2V, constant current 1C charge / discharge. The specific test results are as follows: Figure 7 and Figure 8 As shown. By Figure 7 and Figure 8 It can be seen that the lithium-aluminum alloy reference electrode has a significant advantage in stability compared to the traditional lithium-plated copper wire.

[0164] The three-electrode pouch cells assembled in Example 1 and Comparative Example 2 were subjected to cycle life testing using a Xinwei electrochemical workstation at charge-discharge voltages of 3-5.2V and constant current charge-discharge currents of 1C. The charge-discharge curves of the full charge, positive electrode, and negative electrode, as well as the EIS impedance diagrams of the full charge, positive electrode, and negative electrode, were monitored using the three-electrode pouch cell prepared in Example 1. By comparing the test results of the positive and negative electrodes at different cycle numbers, the state changes of the positive and negative electrodes during cycling can be obtained, thus achieving non-destructive analysis of lithium-ion battery life degradation. The positive-negative electrode voltage, negative-reference voltage, and positive-reference voltage test data of the three-electrode pouch cells prepared in Example 1 and Comparative Example 2 at different cycle numbers are shown in Tables 1 and 2, respectively. Then, using graphite as the positive electrode and aluminum as the negative electrode, a lithium-aluminum alloy reference electrode was prepared according to the preparation method in Example 1. During the preparation process, the cross-sectional SEM image of the lithium-aluminum reference electrode at the end of charging is shown in Table 1. Figure 9 As shown, the cross-sectional SEM image of the lithium-aluminum reference electrode at the end of the discharge stage is as follows. Figure 10 As shown. By Figure 9 and Figure 10 It can be seen that the alloy reference electrode exhibits a small number of columnar pores after lithium extraction, but still maintains structural stability, and the alloy volume remains almost unchanged, indicating that the lithium-aluminum alloy is relatively stable. In addition, charge-discharge cycles were performed during the preparation of the lithium-aluminum alloy reference electrode, forming a lithium-aluminum alloy layer. After 50 charge-discharge cycles, the thickness of the lithium-aluminum alloy layer is greater than 50 μm and remains relatively stable. Therefore, the lithium-aluminum alloy, as a reference electrode that does not participate in lithium extraction and insertion, can exhibit better stability, proving that the present invention has the advantage of high stability.

[0165] Table 1. Voltage parameters of the three-electrode pouch cell in Example 1

[0166] Table 2 Voltage parameters of the three-electrode pouch cell in Comparative Example 2

[0167] As shown in Tables 1 and 2, compared with Comparative Example 2, using the lithium-aluminum alloy prepared in Example 1 of this invention as a reference electrode can accurately and stably monitor the positive and negative electrode voltages of the three-electrode soft-pack battery, and can still monitor the positive and negative electrode potentials of the battery relatively stably after 50 cycles.

[0168] The lithium-aluminum reference electrode synthesized in Example 1 was immersed in a 4 mol / L high-concentration lithium hexafluorophosphate electrolyte for 72 hours. Scanning electron microscopy (SEM) images of the lithium-aluminum reference electrode synthesized in Example 1 before and after immersion were obtained, as shown below. Figure 11 and Figure 12 As shown. By Figure 11 and Figure 12 The comparison shows that the lithium-aluminum reference electrode synthesized in Example 1 did not show significant changes when immersed in the high-concentration electrolyte used to assemble the three-electrode soft pack, indicating that the reference electrode of the present invention has good corrosion resistance in the corresponding electrolyte.

[0169] The nominal stress-displacement curve of the lithium-aluminum reference electrode synthesized in Example 1 was tested under the following conditions: a microscale uniaxial tensile test with both ends clamped, a displacement loading rate of 1 micrometer per second, and a displacement resolution of 50 nanometers. The loading and fracture process were observed in situ using an optical microscope. Specific data are as follows: Figure 13 As shown, the lithium-aluminum reference electrode synthesized in Example 1 has a fracture strength of approximately 83 MPa in a uniaxial tensile test, exhibiting good mechanical properties that meet the requirements for use as a reference electrode.

[0170] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. An alloy reference electrode, characterized in that: The alloy reference electrode comprises a metallic material and an alloy layer located on the surface of the metallic material; The alloy layer contains alloy particles; The alloy particles include aluminum-lithium alloy particles, aluminum-sodium alloy particles, aluminum-potassium alloy particles, sodium-tin alloy particles, lithium-tin alloy particles, potassium-tin alloy particles, sodium-bismuth alloy particles, potassium-bismuth alloy particles, or lithium-bismuth alloy particles, sodium-antimony alloy particles, potassium-antimony alloy particles, or lithium-antimony alloy particles.

2. The alloy reference electrode according to claim 1, characterized in that: The metallic material includes foamed metal or metal sheet; the foamed metal includes at least one of foamed aluminum, foamed tin, foamed bismuth, and foamed antimony; the metal sheet includes at least one of aluminum, tin, bismuth, and antimony.

3. The alloy reference electrode according to claim 1, characterized in that: The metal material is a porous foam metal, and the alloy particles are loaded on the surface and / or within the pores of the foam metal.

4. The method for preparing the alloy reference electrode according to any one of claims 1-3, characterized in that: Includes the following steps: The metal materials, battery separator, first electrolyte, and electrodes are assembled into a battery, and then charge and discharge cycles are performed. The first electrolyte contains metal ions. During charge-discharge cycles, the metal ions in the first electrolyte undergo an alloying reaction with the metal material to obtain the reference electrode. The metal material is a reference electrode, and the electrode is the positive electrode and negative electrode of the battery; or, the metal material is the positive electrode of the battery, and the electrode is the negative electrode of the battery; or, the metal material is the negative electrode of the battery, and the electrode is the positive electrode of the battery.

5. The method for preparing the alloy reference electrode according to claim 4, characterized in that: The charging and discharging voltage is 3-5.2V; And / or, the charging / discharging current density is 0.4-0.6 mA / cm². 2 ; And / or, the charge-discharge reaction is repeated 8-12 times.

6. A three-electrode soft-pack battery, characterized in that: The three-electrode pouch cell includes a three-electrode pouch cell positive electrode, a first separator, an alloy reference electrode as described in any one of claims 1-3, a second separator, a three-electrode pouch cell negative electrode, and a second electrolyte.

7. The three-electrode soft-pack battery according to claim 6, characterized in that: The three-electrode soft-pack battery is a sodium-ion battery, a potassium-ion battery, or a lithium-ion battery.

8. The three-electrode soft-pack battery according to claim 6, characterized in that: The second electrolyte contains a metal salt, an additive, and a solvent; the additive includes at least one of vinylene carbonate, fluoroethylene carbonate, propylene sulfite, and vinyl sulfate.

9. The method for preparing the three-electrode soft-pack battery according to any one of claims 6-8, characterized in that: The preparation method of the three-electrode soft-pack battery is either Method 1 or Method 2. The first method includes the following steps: The positive electrode of the three-electrode soft-pack battery, the first separator, the metal material, the second separator, the negative electrode of the three-electrode soft-pack battery, and the second electrolyte are assembled into a three-electrode soft-pack battery pack. The positive or negative electrode of the three-electrode soft-pack battery is electrically connected to the metal material, and then charge-discharge cycles are performed to allow the metal ions in the second electrolyte to undergo an alloying reaction with the metal material. The positive electrode of the three-electrode soft-pack battery is connected to the negative electrode of the three-electrode soft-pack battery to obtain the three-electrode soft-pack battery. The second method includes the following steps: The three-electrode soft-pack battery positive electrode, the first separator, the alloy reference electrode according to any one of claims 1-3, the second separator, the three-electrode soft-pack battery negative electrode, and the second electrolyte are assembled into a three-electrode soft-pack battery pack.

10. An electrical appliance, characterized in that: The electrical device contains a three-electrode pouch battery as described in any one of claims 6-8.

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