CN116741939A - Negative plate and mixed lithium-sodium ion battery - Google Patents

Negative plate and mixed lithium-sodium ion battery Download PDF

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Publication number
CN116741939A
CN116741939A CN202210200229.4A CN202210200229A CN116741939A CN 116741939 A CN116741939 A CN 116741939A CN 202210200229 A CN202210200229 A CN 202210200229A CN 116741939 A CN116741939 A CN 116741939A
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China
Prior art keywords
lithium
negative electrode
electrode sheet
ion battery
sodium
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Chinese (zh)
Inventor
黄华文
赵伟
李素丽
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Zhuhai Cosmx Battery Co Ltd
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Zhuhai Cosmx Battery Co Ltd
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Priority to CN202210200229.4A priority Critical patent/CN116741939A/en
Publication of CN116741939A publication Critical patent/CN116741939A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention provides a negative plate and a mixed lithium-sodium ion battery containing the same. The mixed lithium-sodium ion battery belongs to a novel secondary ion battery system. Similar to a sodium ion battery, the initial coulombic efficiency is low because the SEI film is produced at the negative electrode in the initial charge process, and the capacity exertion of the battery is affected. In secondary ion battery systems, pre-supplementation of active metal ions is an effective way to increase the coulombic efficiency of the material. However, in the existing simple sodium ion battery, the active type of metallic sodium is higher, the process of electrode sodium supplementation is still immature, and a certain danger exists, so that the efficient and safe sodium supplementation way is still lacking at present to improve the first-circle coulomb efficiency of the sodium ion battery. The invention provides a strategy of adopting negative electrode lithium supplement to be applied to the mixed lithium-sodium ion battery, and the first-circle coulomb efficiency of the mixed lithium-sodium ion battery is safely and effectively improved.

Description

Negative plate and mixed lithium-sodium ion battery
Technical Field
The invention belongs to the technical field of secondary ion batteries, and particularly relates to a negative plate and a mixed lithium-sodium ion battery comprising the negative plate.
Background
In the field of portable energy storage, lithium ion batteries have been widely used because of their advantages in terms of energy density, cycle life, etc., but due to the lack of lithium resources, it is difficult to realize long-term large-scale use of lithium ion batteries, so scientists have been dedicated to develop new generation energy storage systems in recent years. Sodium ion batteries are paid attention because of their most similar systems to lithium ion batteries and their advantages in terms of low theoretical cost, low temperature, excellent fast charge performance, etc., but because of their lower theoretical energy density, the application fields are limited to some extent. Therefore, the energy storage system with low development cost and high energy density has great application value. The hybrid lithium-sodium battery is a design that can achieve complementary advantages of lithium-ion and sodium-ion batteries. In the battery system, the negative electrode is an indispensable part, and contains an active material capable of storing lithium ions and sodium ions at the same time, and the negative electrode determines the performance of the battery system to a large extent.
Similar to lithium ions, in the process of embedding metal ions into the anode material of the mixed lithium-sodium ion battery in the first circle, a passivation film (SEI film) can be formed on the surface of the material, and part of active metal ions can be consumed in the process, so that the first circle coulomb efficiency of the battery is lower, and the cycle performance of the mixed lithium-sodium ion battery is influenced. How to realize the design of the negative electrode of the mixed lithium-sodium ion battery with high first-circle coulombic efficiency is a great challenge for developing a mixed lithium-sodium ion battery system.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention aims to provide a negative plate and a mixed lithium-sodium ion battery comprising the negative plate, wherein the negative plate is a pre-lithiated negative plate for the mixed lithium-sodium ion battery. The pre-lithiated negative electrode plate is applied to the mixed lithium-sodium ion battery, active lithium in the negative electrode plate participates in the reaction in the first-cycle charge-discharge process to generate the SEI film, so that metal ions provided by the positive electrode can be reduced, the first-cycle coulomb efficiency of the battery is improved, and the cycle stability of the mixed lithium-sodium ion battery is further improved.
The invention aims at realizing the following technical scheme:
a negative electrode sheet including active lithium, a current collector, and an active material layer; the active material layer is coated on the surface of the current collector; the active material layer includes an active material; the mass of active lithium in the negative plate accounts for 0.1-80% of the total mass of the active material.
According to an embodiment of the present invention, the active lithium is metal lithium, and illustratively, the active lithium is metal lithium particles, lithium sheets, lithium strips, or the like.
According to an embodiment of the present invention, the active lithium may be disposed on the surface and/or inside of the current collector; and/or the active lithium may be disposed on the surface and/or inside the active material layer.
According to an embodiment of the present invention, the mass of active lithium in the negative electrode sheet is 0.5 to 40% of the total mass of the active material. Illustratively, the mass of active lithium in the negative electrode sheet comprises 0.1%, 0.5%, 1%, 2%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 70%, or 80% of the total mass of the active material.
According to an embodiment of the present invention, the negative electrode sheet is prepared by at least one of the following methods: a negative electrode advanced formation method, a negative electrode lithium powder spraying method, a negative electrode lithium sheet/belt rolling method and a negative electrode three-layer electrode method.
The negative electrode advanced formation method is to form a negative electrode plate separately, and assemble the negative electrode plate with a positive electrode to assemble a full battery after an SEI film is formed on the surface of the negative electrode plate.
The method for spraying lithium powder on the negative electrode comprises the steps of dispersing metal lithium powder particles coated with a protective layer of lithium ion conductivity and electron conductivity into an organic solvent, and coating the metal lithium powder particles on the surface of a negative electrode plate in a spraying mode; the material forming the protective layer is an inorganic material (such as amorphous carbon, graphite, metal (such as iron), etc.) or a conductive polymer material (such as polyethylene, polypropylene, polystyrene, epoxy resin, polyaniline, etc.).
The negative electrode lithium sheet/strip rolling method is to prepare metal lithium into a sheet shape of a lithium sheet or a lithium strip in advance, and roll-bond the negative electrode sheet and the metal lithium sheet or the lithium strip in a one-layer or multi-layer, one-time or multi-time manner.
The negative electrode three-layer electrode method is to coat metal lithium powder on a copper foil substrate, and coat a protective layer on the outer layer to form a functional current collector; the material forming the protective layer is conductive polymer material (such as polythiophene, polypropylene, polystyrene, polyaniline, polypyrrole, etc.); after the battery cell is injected with the liquid, the protective layer is dissolved in the electrolyte, so that the metallic lithium is contacted with the anode active material layer to achieve the aim of pre-lithiation.
According to the embodiment of the invention, the active material in the negative electrode sheet can be satisfied to have the capability of storing lithium ions and sodium ions at the same time.
According to an embodiment of the present invention, the active material in the negative electrode sheet is selected from, for example, natural graphite, artificial graphite, mesophase micro carbon spheres, hard carbon, soft carbon, sn, snO, snO 2 、Sb、Sb 2 O 3 、Bi、Bi 2 O 3 、TiO 2 At least one of the following. Illustratively, the active material in the negative electrode sheet is selected from hard carbon.
According to an embodiment of the invention, the negative electrode sheet is used for a hybrid lithium sodium ion battery.
According to an embodiment of the present invention, the active material layer in the negative electrode sheet further includes a conductive agent and a binder.
According to an embodiment of the present invention, the conductive agent includes, but is not limited to: a carbon-based material, a metal-based material, a conductive polymer, or a mixture thereof. In some embodiments, the carbon-based material is selected from natural graphite, synthetic graphite, carbon black, acetylene black, ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material is selected from the group consisting of metal powder, metal fiber, copper, nickel, aluminum, silver. In some embodiments, the conductive polymer is a polyphenylene derivative.
According to an embodiment of the present invention, the binder includes, but is not limited to: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), water-based acrylic resins, polyvinyl alcohol, polyvinyl butyral, polyurethane, fluorinated rubber, carboxymethyl cellulose (CMC), polyacrylic acid (PAA), epoxy resins, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinylpyrrolidone, nylon.
According to an embodiment of the invention, the active material layer in the negative electrode sheet comprises the following components in percentage by mass:
75-98 wt% of active material, 1-15 wt% of conductive agent and 1-10 wt% of binder.
Preferably, the active material layer in the negative plate comprises the following components in percentage by mass:
82-96 wt% of active material, 2-10 wt% of conductive agent and 2-8 wt% of binder.
According to an embodiment of the present invention, the particle diameter D50 of the active material in the negative electrode sheet is 0.5 μm to 20.0 μm, and preferably the particle diameter D50 of the active material is 3.0 μm to 15.0 μm.
According to an embodiment of the present invention, the active material in the negative electrode sheet has a BET specific surface area of 0.1 to 20.0m 2 Preferably, the BET specific surface area of the active material is 1.0 to 10.0m 2 /g。
According to an embodiment of the present invention, the current collector includes, but is not limited to: copper foil, carbon coated copper foil, perforated copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, conductive metal coated polymeric substrates, and any combination thereof.
The invention also provides a hybrid lithium-sodium ion battery, which comprises the negative plate.
According to an embodiment of the present invention, the use of the mixed lithium-sodium ion battery is not particularly limited, and the battery can be used for various known uses. For example: standby power, automobiles, motorcycles, electric boats, bicycles, lighting fixtures, toys, game machines, watches, electric tools, cameras, large-sized batteries for home use, energy storage power stations, and the like.
The invention has the beneficial effects that:
the invention provides a negative plate and a mixed lithium-sodium ion battery containing the same. The mixed lithium-sodium ion battery belongs to a novel secondary ion battery system. Similar to a sodium ion battery, the initial coulombic efficiency is low because the SEI film is produced at the negative electrode in the initial charge process, and the capacity exertion of the battery is affected. In secondary ion battery systems, pre-supplementation of active metal ions is an effective way to increase the coulombic efficiency of the material. However, in the existing simple sodium ion battery, the active type of metallic sodium is higher, the process of electrode sodium supplementation is still immature, and a certain danger exists, so that the efficient and safe sodium supplementation way is still lacking at present to improve the first-circle coulomb efficiency of the sodium ion battery. According to the invention, a relatively mature lithium supplementing way is selected through a conversion thought, and the effect of improving the coulombic efficiency of the hard carbon negative electrode of the mixed ion battery is achieved while the mixed lithium-sodium ion battery is constructed by adding active lithium into the hard carbon negative electrode.
Detailed Description
< positive electrode sheet >
The mixed lithium-sodium ion battery also comprises a positive plate, wherein the positive plate comprises a current collector and an active material layer; the active material layer is coated on the surface of the current collector; the active material layer includes an active material having both a capability of storing lithium ions and a capability of storing sodium ions.
According to an embodiment of the present invention, the active material in the positive electrode sheet includes one or more of a transition metal layered oxide, a polyanion material, and a prussian blue-based material.
According to an embodiment of the invention, the transition metal layered oxide is selected, for example, from Na [ Ni ] 0.5 Fe 0.5 ]O 2 、Na[Co 0.5 Fe 0.5 ]O 2 、Na[Ni 0.5 Co 0.5 ]O 2 、Na[Ni 1/3 Fe 1/3 Mn 1/3 ]O 2 、Na[Cu 1/9 Ni 2/9 Fe 1/3 Mn 1/3 ]O 2 Etc.
According to an embodiment of the invention, the polyanionic material has the chemical formula A' x’ M’ y’ (X n’ O m ) z’ F w Wherein A 'is Li and/or Na, M' is a transition metal ion of variable valence, X is one or more of P, S and Si, and X 'is not less than 1, y'>The values of 0, z 'is more than or equal to 1, w is more than or equal to 0, and n' and m accord with the principle of conservation of charge.
According to an embodiment of the invention, M' is one or more of Ti, V, fe and Mn.
According to an embodiment of the invention, the polyanionic material is selected from the group consisting of NaFePO 4 、Na 3 V 2 (PO 4 ) 3 、Na 2 MnP 2 O 7 、Na 2 FeP 2 O 7 、Na 2 FePO 4 F、Na 3 V 2 (PO 4 ) 2 F 3 、Na 3 V 2 (PO 4 ) 2 F 3 、Na 2 Fe 2 (SO 4 ) 3 、NaTi 2 (PO 4 ) 3 And the like.
According to an embodiment of the present invention, the Prussian blue material has a chemical formula a x M z [Fe(CN) 6 ] y Wherein A is an alkali metal cation, M is a transition metal cation, and x is more than or equal to 1 and less than or equal to 2,0.9, y is more than or equal to 1,0.8 and z is more than or equal to 1.
According to the embodiment of the invention, the Prussian blue type material also contains crystal water. Illustratively, the Prussian blue-based material has 0 to 2 crystal waters.
According to embodiments of the present invention, a may be one or more of Li, na, K, rb, cs and Fr, in particular.
According to embodiments of the invention, M may be one or more of Sc, ti, V, cr, mn, fe, co, ni, cu, zr and Mo in particular.
According to an embodiment of the present invention, the Prussian blue type material is selected from LiFe 2 (CN) 6 、LiCoFe(CN) 6 、LiMnFe(CN) 6 、NaFe 2 (CN) 6 、KFe 2 (CN) 6 、NaCuFe(CN) 6 、Na 1.72 Mn[Fe(CN) 6 ] 0.99 、Na 1.92 FeFe(CN) 6 、Na 1.61 Fe 1.89 (CN) 6 、NaNiFe(CN) 6 、Na 2 Fe 2 (CN) 6 、Na 2 MnFe(CN) 6 、Na 2 CoFe(CN) 6 、Na 2 NiFe(CN) 6 And the like.
According to an embodiment of the invention, the positive electrode sheet is used for a hybrid lithium sodium ion battery.
According to an embodiment of the present invention, the active material layer in the positive electrode sheet further includes a conductive agent and a binder.
According to an embodiment of the present invention, the conductive agent includes, but is not limited to: a carbon-based material, a metal-based material, a conductive polymer, or a mixture thereof. In some embodiments, the carbon-based material is selected from natural graphite, synthetic graphite, carbon black, acetylene black, ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material is selected from the group consisting of metal powder, metal fiber, copper, nickel, aluminum, silver. In some embodiments, the conductive polymer is a polyphenylene derivative.
According to an embodiment of the present invention, the binder includes, but is not limited to: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), water-based acrylic resin, polyvinyl alcohol, polyvinyl butyral, polyurethane, fluorinated rubber, carboxymethyl cellulose (CMC), polyacrylic acid (PAA).
According to an embodiment of the invention, the active material layer in the positive electrode sheet comprises the following components in percentage by mass:
75-98 wt% of active material, 1-15 wt% of conductive agent and 1-10 wt% of binder.
Preferably, the active material layer in the positive plate comprises the following components in percentage by mass:
82-96 wt% of active material, 2-10 wt% of conductive agent and 2-8 wt% of binder.
According to an embodiment of the present invention, the current collector includes, but is not limited to: aluminum foil, carbon coated aluminum foil, perforated aluminum foil, stainless steel foil, conductive metal coated polymeric substrates, and any combination thereof.
According to an embodiment of the present invention, the positive electrode sheet may be prepared according to a conventional method in the art. The active material, and optionally the conductive agent and binder are typically dispersed in a solvent (e.g., NMP) to form a uniform positive electrode slurry, which is coated on a current collector, and dried to obtain a positive electrode sheet.
< electrolyte solution >
The mixed lithium-sodium ion battery also comprises an electrolyte, wherein lithium ions and sodium ions need to exist in the electrolyte at the same time, and the mixed lithium-sodium ion battery can be realized by adding lithium salt and sodium salt into the same solvent.
Illustratively, the electrolyte includes a complex organic solvent, a lithium salt, and a sodium salt; the composite organic solvent comprises propylene carbonate and an ether compound, wherein the mass of the propylene carbonate accounts for 10-80 wt% of the total mass of the composite organic solvent, and the mass of the ether compound accounts for 5-40 wt% of the total mass of the composite organic solvent.
According to an embodiment of the invention, the electrolyte is used for mixing lithium sodium ion batteries.
According to an embodiment of the present invention, the propylene carbonate accounts for 20wt% to 80wt% of the total mass of the composite organic solvent, for example, 10wt%, 20wt%, 30wt%, 40wt%, 50wt%, 60wt%, 70wt% or 80wt%.
According to an embodiment of the present invention, the mass of the ether compound is 10wt% to 30wt%, for example, 5wt%, 10wt%, 20wt%, 30wt% or 40wt% of the total mass of the composite organic solvent.
According to an embodiment of the present invention, the ether compound is selected from one or more of ethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether (DEGDME), triethylene glycol dimethyl ether (TRGDME), tetraethylene glycol dimethyl ether (TEGDME), fluoroether (F-EPE), fluoroether (D2), fluoroether (HFPM), fluoroether (MFE), fluoroether (EME), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), 1, 3-Dioxane (DOL), 1, 4-Dioxane (DOX) in any ratio.
According to an embodiment of the present invention, the composite organic solvent further includes other solvents selected from one or more of Ethylene Carbonate (EC), butylene carbonate, difluoroethylene carbonate (DFEC), dimethyl fluorocarbonate, methylethyl fluorocarbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, methylethyl carbonate (EMC), methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl Acetate (EA), propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, methyl difluoroacetate, ethyl difluoroacetate, gamma-butyrolactone (GBL), gamma-valerolactone, delta-valerolactone, sulfolane, dimethyl sulfoxide (DMSO), methylene chloride, dichloroethane, in any ratio.
According to an embodiment of the invention, the lithium salt is selected from lithium hexafluorophosphate (LiPF 6 ) Lithium tetrafluoroborate (LiBF) 4 ) Lithium perchlorate (LiClO) 4 ) Lithium hexafluoroarsenate (LiAsF) 6 ) Lithium hexafluoroantimonate (LiSbF) 6 ) Lithium difluorophosphate (LiPF) 2 O 2 ) 4, 5-dicyano-2-trifluoromethylimidazole Lithium (LiDTI), bis (oxalato) borate Lithium (LiBOB), bis (malonato) borate Lithium (LiBMB), difluoro (oxalato) borate Lithium (LiDFOB), bis (difluoromalonato) borate Lithium (LiBDFMB), (malonato) borate Lithium (LiMOB), (difluoromalonato) borate Lithium (LiDFMOB), tris (oxalato) phosphate Lithium (LiTOP), tris (difluoromalonato) phosphate Lithium (LiTDFMP), tetrafluoro (LiTFOP), difluoro (LiDFOP) lithium dioxalate, bis (fluorosulfonyl) imide lithium (LiLiLiLiSI), bis (trifluoromethanesulfonyl) imide lithium (LiN (SO) 2 F)(SO 2 CF 3 ) Lithium nitrate (LiNO) 3 ) One or more organic/inorganic salts of lithium fluoride (LiF) are mixed in any ratio.
According to an embodiment of the invention, the sodium salt is selected from sodium hexafluorophosphate (NaPF 6 ) Sodium tetrafluoroborate (NaBF) 4 ) Sodium perchlorate (NaClO) 4 ) Sodium hexafluoroarsenate (NaAsF) 6 ) Sodium hexafluoroantimonate (NaSbF) 6 ) Sodium difluorophosphate (NaPF) 2 O 2 ) Sodium 4, 5-dicyano-2-trifluoromethylimidazole (NaDTI), sodium bis (oxalato) borate (NaBOB), sodium bis (malonato) borate (NaBMB), sodium difluorooxalato borate (NaDFOB), sodium bis (difluoromalonato) borate (NaBDFMB), sodium malonato (NaMOB), (difluoromalonato) borate (NaDFMOB), sodium tris (oxalato) phosphate (NaTOP), sodium tris (difluoromalonato) phosphate (NaTDFMP), sodium tetrafluorooxalate phosphate (NaTFOP), sodium difluorodioxalate phosphate (NaDFOP), sodium bis (fluorosulfonyl) imide (NaFSI), sodium bis (trifluoromethanesulfonyl) imide (NaTFSI), (fluorosulfonyl) (trifluoromethanesulfonyl) imide sodium (NaN (SO) 2 F)(SO 2 CF 3 ) Sodium nitrate (NaNO) 3 ) One or more organic/inorganic salts of sodium fluoride (NaF) are mixed in any ratio.
According to an embodiment of the present invention, the concentration of the lithium salt in the electrolyte is 0.2 to 5.0mol/L, for example, 0.2mol/L, 0.5mol/L, 0.8mol/L, 1.0mol/L, 1.2mol/L, 1.5mol/L, 1.8mol/L, 2.0mol/L, 3.0mol/L, 4.0mol/L, or 5.0mol/L.
According to an embodiment of the present invention, the concentration of the sodium salt in the electrolyte is 0.2 to 5.0mol/L, for example, 0.2mol/L, 0.5mol/L, 0.8mol/L, 1.0mol/L, 1.2mol/L, 1.5mol/L, 1.8mol/L, 2.0mol/L, 3.0mol/L, 4.0mol/L or 5.0mol/L.
According to an embodiment of the present invention, the electrolyte may further include an additive selected from one or more of Vinylene Carbonate (VC), vinyl Ethylene Carbonate (VEC), 1, 3-propane sultone, trifluoromethyl ethylene carbonate, dimethyl sulfate, vinyl methyl sulfate, propylene sulfate, vinyl sulfite, succinic anhydride, biphenyl, diphenyl ether, toluene, xylene, cyclohexylbenzene, fluorobenzene, p-fluorotoluene, p-fluoroanisole, t-butylbenzene, t-pentylbenzene, propenolactone, butane sultone, methylene methane disulfonate, ethylene glycol bis (propionitrile) ether, hexamethyldisilazane, heptamethyldisilazane, dimethyl methylphosphonate, diethyl ethylphosphonate, trimethyl phosphate, triethyl phosphate, triphenyl phosphite, tris (trimethylsilyl) borate, tris (trimethylsilyl) phosphate, and a mixture of any ratio.
According to an embodiment of the invention, the mass of the additive is 0.01-10 wt% of the total mass of the electrolyte. The excessive addition of the additive can lead to incomplete dissolution in the electrolyte, and can reduce the mobility of lithium/sodium ions and sodium ions, thereby reducing the performance of the mixed lithium-sodium ion battery; the addition amount of the additive is too small to play a corresponding role. Preferably, the mass of the additive is 1.0wt% to 5.0wt% of the total mass of the electrolyte.
The preparation method of the present invention will be described in further detail with reference to specific examples. It is to be understood that the following examples are illustrative only and are not to be construed as limiting the scope of the invention. All techniques implemented based on the above description of the invention are intended to be included within the scope of the invention.
The experimental methods used in the following examples are all conventional methods unless otherwise specified; the reagents, materials, etc. used in the examples described below are commercially available unless otherwise specified.
The testing method comprises the following steps:
first circle coulombic efficiency: the mixed lithium-sodium ion battery is charged to an upper limit voltage (4.3V) at a constant current of 0.5C at 25 ℃, then charged to a current of 0.05C at a constant voltage of 4.3V, and kept stand for 5 minutes; then, 0.5C constant current is discharged until the voltage is 2.0V, and the recorded discharge capacity is the first-cycle discharge capacity. The first-turn coulombic efficiency is the ratio of the first-turn discharge capacity to the first-turn charge capacity.
Normal temperature cycle life: the mixed lithium-sodium ion battery is charged to an upper limit voltage (4.3V) at a constant current of 0.5C at 25 ℃, then charged to a current of 0.05C at a constant voltage of 4.3V, and kept stand for 5 minutes; then, the mixture was discharged at a constant current of 0.5C to a voltage of 2.0V and allowed to stand for 5 minutes, which was a charge-discharge cycle. The charge/discharge was thus performed, and the ratio of the discharge capacity after 500 th cycle to the discharge capacity at the first cycle was recorded as the 500-cycle capacity retention rate.
Example 1
(1) Preparation of negative electrode sheet
And (3) weighing hard carbon powder obtained by pyrolyzing phenolic resin at 1200 ℃, conducting agent carbon black, binder Styrene Butadiene Rubber (SBR) and thickener sodium carboxymethylcellulose (CMC), dispersing the hard carbon powder, the conducting agent carbon black, the binder Styrene Butadiene Rubber (SBR) and the thickener sodium carboxymethylcellulose (CMC) in a proper amount of deionized water according to a weight ratio of 90:2.5:5.0:2.5, fully stirring the mixture to form uniform negative electrode slurry, coating the negative electrode slurry on a negative electrode current collector copper foil, and then drying, rolling and cutting the negative electrode slurry to obtain the negative electrode sheet.
(2) Pre-lithiation of negative electrode sheets
Inert lithium powder (specifically polyaniline coated lithium powder) is used as a lithium supplementing agent to prepare a dispersion liquid containing the inert lithium powder, and the inert lithium powder dispersion liquid is sprayed on the surface of the negative electrode plate in a non-contact spray coating mode. Wherein the spraying speed is 0.1mL/s, and the mass of active lithium (specifically lithium powder) accounts for 20% of the total mass of the anode active material. And then drying and rolling the pole piece to obtain the pre-lithiated negative pole piece.
(3) Preparation of positive plate
The cathode material Prussian blue type material (Na 2 Mn[Fe(CN) 6 ]) Dispersing conductive agent carbon black and binder polyvinylidene fluoride (PVDF) in a proper amount of N-methyl pyrrolidone (NMP) according to a weight ratio of 90:5:5, fully stirring to form uniform positive electrode slurry, coating the positive electrode slurry on a positive electrode current collector aluminum foil, drying, rolling and cutting to obtain the positive electrode plate.
(4) Preparation of separator
A wet polyethylene diaphragm with the thickness of 5 mu m is selected as a base material, an alumina ceramic coating with the thickness of 2 mu m is coated on one surface of the base material, PVDF-HFP adhesive layers with the thickness of 1 mu m are respectively coated on two sides of the diaphragm, and the diaphragm with the total thickness of 9 mu m is obtained and is cut into required widths for standby.
(5) Preparation of electrolyte
At both water content and oxygen content<In a glove box filled with argon gas at a mass ratio of 1.0:2.0:0.5, ethylene Carbonate (EC), propylene Carbonate (PC) and ethylene glycol dimethyl ether (DME) were mixed, and lithium hexafluorophosphate (LiPF) was added thereto 6 ) And sodium hexafluorophosphate (NaPF) 6 ) The salt concentration is 1.0mol/L, and the mixed ion battery electrolyte is obtained after uniform stirring.
(6) Preparation of mixed lithium-sodium ion battery
And sequentially stacking the positive electrode, the diaphragm and the negative electrode, enabling the isolating film to be positioned between the positive electrode and the negative electrode, welding the electrode lugs and winding to obtain a winding core, placing the winding core in an aluminum plastic film packaging bag, finally injecting the electrolyte, and performing the procedures of vacuum sealing, standing, formation, shaping and the like to obtain the mixed lithium-sodium ion battery.
Examples 2 to 12 and comparative examples 1 to 4
A hybrid lithium-sodium ion battery was prepared in accordance with the method of example 1, except that the manner of prelithiation and the mass ratio of active lithium were adjusted, and specific information thereof is shown in table 1.
Wherein, the advanced formation method in table 1 refers to that the prepared negative electrode sheet is formed separately, and then assembled with the positive electrode to assemble the full battery after the SEI film is formed on the surface of the negative electrode sheet;
the lithium sheet/strip rolling method in table 1 refers to a method of preparing metal lithium into a sheet shape of a lithium sheet or a lithium strip in advance, and rolling and laminating the negative electrode sheet and the metal lithium sheet or the lithium strip in one or more layers, one or more times;
wherein, the three-layer electrode method in table 1 refers to coating metal lithium powder on a copper foil substrate, and then coating a protective layer on an outer layer to form a functional current collector; the material forming the protective layer is polyaniline which is a conductive polymer material.
Table 1 the manner of prelithiation and the mass ratio of active lithium used in the different examples and comparative examples and the corresponding electrochemical properties
From the results of table 1, it is clear from comparative analysis examples 1 to 13 and comparative examples 1 to 4 that the first cycle coulombic efficiency of the battery system can be effectively improved and the cycle stability thereof can be improved by pre-lithiating the negative electrode of the mixed lithium sodium ion battery by means of a negative electrode advance formation method, a negative electrode spraying lithium powder method, a negative electrode lithium sheet/strip rolling method, a negative electrode three-layer electrode method, and the like. Among them, in comparative example 3, since the addition amount of active lithium is too low, the addition amount of active lithium is insufficient to form an SEI film in the first turn; the excessive amount of active lithium in comparative example 4 resulted in a lower proportion of hard carbon material in the negative electrode, and in the subsequent cycle, there was insufficient negative electrode material to store sodium ions, resulting in a faster overall performance decay of the battery.
The result shows that the active lithium in the negative electrode sheet participates in the SEI film generation reaction in the first-cycle charge and discharge process, so that the metal ions provided by the positive electrode can be reduced, the first-cycle coulomb efficiency of the battery is improved, and the cycle stability of the mixed lithium-sodium ion battery is further improved. Compared with the sodium supplementing process, the lithium supplementing process is more mature and safer in development at the current stage. The design of the mixed lithium-sodium ion battery with high first-circle coulomb efficiency is realized by utilizing the pre-lithiation technology, is simple and easy to implement, and greatly promotes the development of the mixed lithium-sodium ion battery.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A negative electrode sheet, characterized in that the negative electrode sheet comprises active lithium, a current collector, and an active material layer; the active material layer is coated on the surface of the current collector; the active material layer includes an active material; the mass of active lithium in the negative plate accounts for 0.1-80% of the total mass of the active material.
2. The negative electrode sheet according to claim 1, wherein the active lithium is metallic lithium.
3. The negative electrode sheet according to claim 1, wherein the active lithium is metallic lithium particles, lithium sheets, or lithium strips.
4. The negative electrode sheet according to any one of claims 1 to 3, wherein the active lithium is provided on the surface and/or inside of a current collector; and/or, the active lithium is disposed on the surface and/or inside the active material layer.
5. The negative electrode sheet according to any one of claim 1, wherein the mass of active lithium in the negative electrode sheet is 0.5 to 40% of the total mass of the active material.
6. The negative electrode sheet according to any one of claims 1 to 3, wherein the negative electrode sheet is produced by at least one of the following methods: a negative electrode advanced formation method, a negative electrode lithium powder spraying method, a negative electrode lithium sheet/belt rolling method and a negative electrode three-layer electrode method.
7. The negative electrode sheet according to claim 6, wherein the negative electrode advanced formation method is to form the negative electrode sheet separately, and assemble the negative electrode sheet with the positive electrode after the SEI film is formed on the surface of the negative electrode sheet;
and/or, the method for spraying lithium powder on the negative electrode refers to dispersing metal lithium powder particles coated with a protective layer of lithium ion conductivity and electron conductivity into an organic solvent, and then coating the metal lithium powder particles on the surface of a negative electrode sheet in a spraying manner; the material forming the protective layer is an inorganic material or a conductive polymer material;
and/or, the negative electrode lithium sheet/strip rolling method refers to that metal lithium is prepared into a sheet shape of a lithium sheet or a lithium strip in advance, and the negative electrode sheet is rolled and attached with the metal lithium sheet or the lithium strip in a one-layer or multi-layer, one-time or multi-time manner;
and/or, the negative electrode three-layer electrode method is to coat metal lithium powder on a copper foil substrate, and then coat a protective layer on the outer layer to form a functional current collector; the material forming the protective layer is a conductive polymer material.
8. A negative electrode sheet according to any one of claims 1 to 3, characterized in thatThe active material in the negative plate is selected from natural graphite, artificial graphite, mesophase micro carbon spheres, hard carbon, soft carbon and Sn, snO, snO 2 、Sb、Sb 2 O 3 、Bi、Bi 2 O 3 、TiO 2 At least one of them.
9. The negative electrode sheet according to any one of claims 1 to 3, wherein the active material layer in the negative electrode sheet further comprises a conductive agent and a binder, the mass percentages of the components being:
75-98 wt% of active material, 1-15 wt% of conductive agent and 1-10 wt% of binder.
10. A hybrid lithium sodium ion battery comprising the negative electrode sheet of any one of claims 1-9.
CN202210200229.4A 2022-03-02 2022-03-02 Negative plate and mixed lithium-sodium ion battery Pending CN116741939A (en)

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