CN117457855A - Preparation method of pre-lithiated negative electrode plate and lithium ion battery - Google Patents
Preparation method of pre-lithiated negative electrode plate and lithium ion battery Download PDFInfo
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- CN117457855A CN117457855A CN202311417890.1A CN202311417890A CN117457855A CN 117457855 A CN117457855 A CN 117457855A CN 202311417890 A CN202311417890 A CN 202311417890A CN 117457855 A CN117457855 A CN 117457855A
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- lithium
- negative electrode
- lithiated
- lithiation
- electrode sheet
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 17
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 17
- 238000002360 preparation method Methods 0.000 title claims abstract description 10
- 238000006138 lithiation reaction Methods 0.000 claims abstract description 29
- 239000011241 protective layer Substances 0.000 claims abstract description 19
- 239000003792 electrolyte Substances 0.000 claims abstract description 15
- 238000001035 drying Methods 0.000 claims abstract description 10
- 238000005406 washing Methods 0.000 claims abstract description 10
- 238000004519 manufacturing process Methods 0.000 claims abstract description 7
- 238000006243 chemical reaction Methods 0.000 claims abstract description 6
- 239000011261 inert gas Substances 0.000 claims abstract description 4
- 229910052744 lithium Inorganic materials 0.000 claims description 28
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 27
- 238000000034 method Methods 0.000 claims description 16
- 239000007773 negative electrode material Substances 0.000 claims description 11
- 239000010410 layer Substances 0.000 claims description 10
- -1 lithium hexafluorophosphate Chemical compound 0.000 claims description 9
- JWUJQDFVADABEY-UHFFFAOYSA-N 2-methyltetrahydrofuran Chemical compound CC1CCCO1 JWUJQDFVADABEY-UHFFFAOYSA-N 0.000 claims description 6
- 239000007774 positive electrode material Substances 0.000 claims description 6
- 239000002904 solvent Substances 0.000 claims description 6
- 239000000126 substance Substances 0.000 claims description 6
- XTHFKEDIFFGKHM-UHFFFAOYSA-N Dimethoxyethane Chemical compound COCCOC XTHFKEDIFFGKHM-UHFFFAOYSA-N 0.000 claims description 4
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 claims description 4
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 claims description 4
- 150000001875 compounds Chemical class 0.000 claims description 4
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 claims description 4
- 229910003002 lithium salt Inorganic materials 0.000 claims description 4
- 159000000002 lithium salts Chemical class 0.000 claims description 4
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 claims description 3
- 239000000463 material Substances 0.000 claims description 3
- 239000000843 powder Substances 0.000 claims description 3
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 claims description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 2
- 229910019142 PO4 Inorganic materials 0.000 claims description 2
- 239000002033 PVDF binder Substances 0.000 claims description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 2
- HFCVPDYCRZVZDF-UHFFFAOYSA-N [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O Chemical compound [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O HFCVPDYCRZVZDF-UHFFFAOYSA-N 0.000 claims description 2
- YWJVFBOUPMWANA-UHFFFAOYSA-H [Li+].[V+5].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O Chemical compound [Li+].[V+5].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O YWJVFBOUPMWANA-UHFFFAOYSA-H 0.000 claims description 2
- 239000000654 additive Substances 0.000 claims description 2
- 230000000996 additive effect Effects 0.000 claims description 2
- 239000003575 carbonaceous material Substances 0.000 claims description 2
- 239000000919 ceramic Substances 0.000 claims description 2
- 239000003599 detergent Substances 0.000 claims description 2
- RAABOESOVLLHRU-UHFFFAOYSA-N diazene Chemical compound N=N RAABOESOVLLHRU-UHFFFAOYSA-N 0.000 claims description 2
- 229910000071 diazene Inorganic materials 0.000 claims description 2
- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 claims description 2
- NKDDWNXOKDWJAK-UHFFFAOYSA-N dimethoxymethane Chemical compound COCOC NKDDWNXOKDWJAK-UHFFFAOYSA-N 0.000 claims description 2
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 claims description 2
- 239000011888 foil Substances 0.000 claims description 2
- DEUISMFZZMAAOJ-UHFFFAOYSA-N lithium dihydrogen borate oxalic acid Chemical compound B([O-])(O)O.C(C(=O)O)(=O)O.C(C(=O)O)(=O)O.[Li+] DEUISMFZZMAAOJ-UHFFFAOYSA-N 0.000 claims description 2
- MHCFAGZWMAWTNR-UHFFFAOYSA-M lithium perchlorate Chemical compound [Li+].[O-]Cl(=O)(=O)=O MHCFAGZWMAWTNR-UHFFFAOYSA-M 0.000 claims description 2
- 229910001486 lithium perchlorate Inorganic materials 0.000 claims description 2
- 229910001496 lithium tetrafluoroborate Inorganic materials 0.000 claims description 2
- DVATZODUVBMYHN-UHFFFAOYSA-K lithium;iron(2+);manganese(2+);phosphate Chemical compound [Li+].[Mn+2].[Fe+2].[O-]P([O-])([O-])=O DVATZODUVBMYHN-UHFFFAOYSA-K 0.000 claims description 2
- 238000001755 magnetron sputter deposition Methods 0.000 claims description 2
- 229910052748 manganese Inorganic materials 0.000 claims description 2
- 239000011572 manganese Substances 0.000 claims description 2
- 239000000203 mixture Substances 0.000 claims description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims description 2
- 239000010452 phosphate Substances 0.000 claims description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 2
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 claims description 2
- 230000035484 reaction time Effects 0.000 claims description 2
- 239000002153 silicon-carbon composite material Substances 0.000 claims description 2
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 claims description 2
- 239000011366 tin-based material Substances 0.000 claims description 2
- LSGOVYNHVSXFFJ-UHFFFAOYSA-N vanadate(3-) Chemical compound [O-][V]([O-])([O-])=O LSGOVYNHVSXFFJ-UHFFFAOYSA-N 0.000 claims description 2
- 125000005287 vanadyl group Chemical group 0.000 claims description 2
- 238000007740 vapor deposition Methods 0.000 claims description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims 1
- SYRDSFGUUQPYOB-UHFFFAOYSA-N [Li+].[Li+].[Li+].[O-]B([O-])[O-].FC(=O)C(F)=O Chemical compound [Li+].[Li+].[Li+].[O-]B([O-])[O-].FC(=O)C(F)=O SYRDSFGUUQPYOB-UHFFFAOYSA-N 0.000 claims 1
- 229910052814 silicon oxide Inorganic materials 0.000 claims 1
- 230000009257 reactivity Effects 0.000 abstract description 4
- 150000002500 ions Chemical class 0.000 abstract description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 9
- 239000010439 graphite Substances 0.000 description 9
- 229910002804 graphite Inorganic materials 0.000 description 9
- 239000012528 membrane Substances 0.000 description 5
- 238000003860 storage Methods 0.000 description 4
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical group [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 3
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
- 239000011889 copper foil Substances 0.000 description 3
- 238000007086 side reaction Methods 0.000 description 3
- GBVSONMCEKNESD-UHFFFAOYSA-N 1,1'-biphenyl;lithium Chemical compound [Li].C1=CC=CC=C1C1=CC=CC=C1 GBVSONMCEKNESD-UHFFFAOYSA-N 0.000 description 2
- SBLRHMKNNHXPHG-UHFFFAOYSA-N 4-fluoro-1,3-dioxolan-2-one Chemical compound FC1COC(=O)O1 SBLRHMKNNHXPHG-UHFFFAOYSA-N 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 239000006229 carbon black Substances 0.000 description 2
- 239000006258 conductive agent Substances 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- VDVLPSWVDYJFRW-UHFFFAOYSA-N lithium;bis(fluorosulfonyl)azanide Chemical compound [Li+].FS(=O)(=O)[N-]S(F)(=O)=O VDVLPSWVDYJFRW-UHFFFAOYSA-N 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 238000001291 vacuum drying Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- BTBUEUYNUDRHOZ-UHFFFAOYSA-N Borate Chemical compound [O-]B([O-])[O-] BTBUEUYNUDRHOZ-UHFFFAOYSA-N 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- OBNDGIHQAIXEAO-UHFFFAOYSA-N [O].[Si] Chemical compound [O].[Si] OBNDGIHQAIXEAO-UHFFFAOYSA-N 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000007784 solid electrolyte Substances 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
Classifications
-
- 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
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- 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
- H01M4/139—Processes of manufacture
-
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention provides a preparation method of a pre-lithiated negative electrode plate, which comprises the following steps: manufacturing a lithium ion battery negative plate; pre-lithiation treatment is carried out on the negative electrode plate to obtain a pre-lithiated negative electrode plate; in a dry or inert gas environment, placing the pre-lithiated negative electrode sheet into electrolyte for reaction, and washing and drying to form a compact and ion-conducting protective layer on the surface of the pre-lithiated negative electrode sheet; the pre-lithiated negative electrode sheet has higher reactivity, when conventional electrolyte is injected, lithium ions in the pre-lithiated negative electrode interact with the conventional electrolyte to form a thin SEI film on the surface of the electrode sheet, and a protective layer is formed on the surface after washing and drying, so that the protective layer is compact and stable and conducts ions, the stability of electrochemical performance can be ensured, and the safety of the pre-lithiated electrode sheet can be improved.
Description
Technical Field
The invention relates to the field of lithium ion batteries, in particular to a preparation method of a pre-lithiated negative plate and a lithium ion battery.
Background
The lithium ion battery is widely applied to the fields of electric automobiles, energy storage, 3C and the like due to the advantages of high energy density, high voltage platform, long cycle life and the like. However, in the first charge and discharge process of the lithium ion battery, a solid electrolyte film (SEI film) is formed on the surface of the negative electrode, so that irreversible loss of active lithium is caused, and the battery has larger capacity loss (5-10% of graphite and 10-30% of silicon).
Therefore, a pre-lithiation strategy is provided, an additional lithium source is introduced into the anode and the cathode, capacity loss caused by SEI film growth is compensated, and the effects of improving the energy density and the cycle performance of the lithium ion battery are achieved.
Current negative electrode prelithiation methods include contact prelithiation, electrochemical prelithiation or chemical prelithiation; in document Advanced Energy Materials (2021, 11, 2100925), stable Lithium Metal Powder (SLMP) is dispersed in toluene solution, and added dropwise to the surface of a negative electrode sheet to supplement lithium; in literature Nano button (2016, 16, 282-288), the degree of prelithiation is regulated by controlling the current and the cut-off voltage; the university of martial arts patent CN112490394B implements prelithiation by liquid phase reaction of the negative electrode material with a lithiating agent.
The chemical reactivity of the negative electrode plate is increased along with the increase of the lithium content of the negative electrode plate, and the negative electrode plate is unstable in air and easily generates side reactions with oxygen, water and the like to influence the electrochemical performance of the electrode plate; the pre-lithiated cathode has high requirements on environment, such as inert gas environment, and the pre-lithiated pole piece has certain potential safety hazard in the storage process, so that the pre-lithiated pole piece is difficult to be compatible with the actual production process.
Therefore, we propose a preparation method of a pre-lithiated negative electrode plate with interface protection to solve the problem of side reaction of lithium with oxygen, water and the like in the air.
Disclosure of Invention
The invention aims to solve the defects in the prior art, and adopts the following technical scheme:
the preparation method of the pre-lithiated negative electrode plate comprises the following steps:
s1: manufacturing a lithium ion battery negative plate;
s2: pre-lithiation treatment is carried out on the negative electrode plate to obtain a pre-lithiated negative electrode plate;
s3: and (3) in a dry or inert gas environment, placing the pre-lithiated negative electrode sheet into an electrolyte for reaction, and washing and drying to form a compact and ion-conducting protective layer on the surface of the pre-lithiated negative electrode sheet.
By the solution treatment method, a protective layer is formed on the surface of the pre-lithiated cathode, so that the pre-lithiated cathode is prevented from being contacted with air, and the pre-lithiated pole piece is stored for a long time and is better compatible with the actual battery manufacturing process.
Further preferably, in step S1, the negative electrode sheet includes a negative electrode current collector, and an active material layer covering the surface of the negative electrode current collector; the negative electrode current collector is copper foil, and the negative electrode active material layer is one or more compounds selected from carbon materials, silicon-carbon composite materials, silicon oxygen compound materials, tin-based materials and lithium titanate.
Further preferably, in step S2, the pre-lithiation method comprises one or more combinations of stable metallic lithium powder pre-lithiation, lithium foil pre-lithiation, vapor deposition pre-lithiation, magnetron sputtering pre-lithiation, electrochemical pre-lithiation, chemical pre-lithiation, and additive pre-lithiation.
Further preferably, in step S3, the electrolyte is a mixture of a lithium salt and a solvent, and the lithium salt is one or more of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium perchlorate, lithium dioxalate borate, lithium difluorooxalato borate, lithium diimine, and lithium bistrifluoromethylsulfonyliminate; the solvent is one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, tetrahydrofuran, 2-methyl-tetrahydrofuran, dimethoxymethane and 1, 2-dimethoxyethane.
Further preferably, in step S3, the reaction time of the negative electrode sheet in the electrolyte is 10-60min.
Further preferably, in step S3, the detergent is 2-methyltetrahydrofuran, the washing times are 1-5 times, the drying conditions are 50-70 ℃, and the drying time is 1-3 hours.
A lithium ion battery comprises a positive plate, a diaphragm, electrolyte and the pre-lithiated negative plate with a protective layer.
Further preferably, the positive electrode sheet includes a positive electrode current collector, and a positive electrode active material layer covering the surface of the positive electrode current collector; the positive electrode active material layer is one or more compounds including, but not limited to, lithium cobaltate, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadyl phosphate, lithium vanadate, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, and lithium-rich manganese base.
Further preferably, the membrane is one of a PVDF rubberized membrane, a ceramic membrane, a PE base membrane and a PP base membrane.
Compared with the prior art, the invention has the beneficial effects that:
the pre-lithiated negative electrode sheet has higher reactivity, when conventional electrolyte is injected, lithium ions in the pre-lithiated negative electrode interact with the conventional electrolyte to form a thin SEI film on the surface of the electrode sheet, and a protective layer is formed on the surface after washing and drying, so that the protective layer is compact and stable and conducts ions, the stability of electrochemical performance can be ensured, and the safety of the pre-lithiated electrode sheet can be improved.
According to the invention, a protective layer is formed on the surface of the pre-lithiated cathode by a solution treatment method, so that the pre-lithiated cathode is prevented from being contacted with air, and the pre-lithiated pole piece is stored for a long time, and is better compatible with the actual battery manufacturing process.
Drawings
FIG. 1 is a schematic flow chart of the present invention;
fig. 2 is a graph of the first charge and discharge of the battery cell 1;
fig. 3 is a graph of the first charge and discharge of the cells 2, 3;
fig. 4 is a graph of the first charge and discharge of the cells 4, 5;
fig. 5 is a graph of the first charge and discharge of the cells 6, 7.
In the figure: negative electrode current collector 10, negative electrode active material layer 20, pre-lithiated negative electrode active material layer 30, protective layer 40.
Description of the embodiments
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments.
Examples
Referring to FIG. 1
Preparing a negative plate: graphite with unit capacity of 350 mAh/g, graphite, conductive agent carbon black, CMC and SBR according to 91:5:1.5:2.5, the solvent is NMP, the negative electrode active material 20 is obtained by fully stirring and mixing, the negative electrode active material is uniformly coated on the negative electrode current collector 10 (copper foil), and the negative electrode current collector is placed into a vacuum oven for heating at 60 ℃ for 24 hours, so as to obtain the negative electrode sheet 1.
Pre-lithiation of the negative electrode sheet: the negative electrode sheet was subjected to chemical prelithiation. The lithiation solution is a 1 mol/L2-methyltetrahydrofuran solution of biphenyl lithium, and the negative electrode plate is immersed into the lithiation solution to react for 10 min to obtain a negative electrode plate 2; after 48 hours of storage in a dry environment, the negative electrode sheet 3 was obtained.
Interface protection of the pre-lithiated negative electrode plate: immersing the pre-lithiated anode sheet 2 in a 1 mol/L lithium bis (fluorosulfonyl) imide (LiFSI) fluoroethylene carbonate (FEC) solution for 10 min, then washing twice with 2-methyltetrahydrofuran, and finally, vacuum drying the electrode at 60 ℃ to form a pre-lithiated anode sheet protective layer 40, thereby obtaining an anode sheet 4; after 48 hours of storage in a dry environment, the negative electrode sheet 5 was obtained.
Preparation of the battery cell: and preparing a positive plate by using lithium iron phosphate as a positive electrode material, respectively matching with the negative plates 1,2, 3, 4 and 5, and then preparing a coiled 3.5Ah soft-packed battery according to the conventional procedures in the industry, namely the battery cores 1,2, 3, 4 and 5, and testing the performance.
Examples
Referring to FIG. 1
Preparing a negative plate: graphite with unit capacity of 350 mAh/g, graphite, conductive agent carbon black, CMC and SBR according to 91:5:1.5:2.5, the solvent is NMP, the negative electrode active material 20 is obtained by fully stirring and mixing, the negative electrode active material is uniformly coated on a negative electrode current collector 10 (copper foil), and the negative electrode active material is placed into a vacuum oven for heating at 60 ℃ for 24 hours, so as to obtain a negative electrode plate.
Pre-lithiation of the negative electrode sheet: the negative electrode sheet was subjected to chemical prelithiation. The lithiation solution is a 1 mol/L2-methyltetrahydrofuran solution of biphenyl lithium, and the negative electrode plate is immersed into the lithiation solution to react for 10 min, so as to obtain the pre-lithiation negative electrode plate.
Interface protection of the pre-lithiated negative electrode plate: the pre-lithiated negative electrode sheet is immersed in 1 mol/L of lithium hexafluorophosphate (LiPF 6) dimethyl carbonate (DMC): ethylene Carbonate (EC) =1: 1, washing with 2-methyltetrahydrofuran twice, and finally, vacuum drying at 60 ℃ to form a pre-lithiated negative electrode sheet protective layer to obtain a negative electrode sheet 6; after 48 hours of storage in a dry environment, the negative electrode sheet 7 was obtained.
Preparation of the battery cell: and preparing a positive plate by using lithium iron phosphate as a positive electrode material, respectively matching with the negative plates 6 and 7, and preparing a coiled 3.5Ah soft-package battery according to the conventional procedures in the industry, and recording the coiled 3.5Ah soft-package battery as the test performance of the battery cores 6 and 7.
Comparison of experimental data in the above examples is shown in the following table:
fig. 2 shows the first charge and discharge curve of the battery 1 mounted on the graphite negative electrode without pre-lithiation, and it can be seen that the charge capacity of the battery is 4076.9 mAh, the discharge capacity is 3668.5 mAh, and the first cycle efficiency is 89.98%.
Fig. 3 shows the first charge-discharge curve of the battery 2 mounted on the pre-lithiated graphite negative electrode, and shows that the charge capacity of the battery is 4031.9 mAh, the discharge capacity is 3819.8 mAh, and the first cycle efficiency is 94.74%, which is improved by 4.76% compared with the non-pre-lithiated graphite negative electrode. Indicating that pre-lithiation can reduce the loss of active lithium in a graphite anode; when the pole piece is placed under a dry environment for 48h, the charging capacity of the corresponding battery 3 is 4027.2 mAh, the discharge capacity is 3774.1 mAh, and the first-week efficiency is 93.72%. Compared with a pole piece which is not placed in a dry environment, the initial effect is reduced by 1.02 percent. The pre-lithiated cathode and air are proved to have side reactions, which reduce the electrochemical performance.
Fig. 4 shows the first charge-discharge curve of the battery 4 with interface protection, in which the battery has a charge capacity of 4018.8mAh, a discharge capacity of 3839.7mAh, and a first cycle efficiency of 95.54%. When the pole piece is placed for 48 hours in a dry environment, the capacity of the corresponding battery 5 is 4028.7mAh, the discharge capacity is 3831.6mAh, the first-week efficiency is 95.11%, and the reduction is 0.43%. The protective layer can effectively inhibit the reaction of the pre-lithiated anode and air, and improves the stability of the pre-lithiated anode in air.
Fig. 5 shows the first charge-discharge curve of the battery 6 with interface protection, in which the battery has a charge capacity of 3619.2mAh, a discharge capacity of 3449.1mAh, and a first cycle efficiency of 95.30%. When the pole piece is placed for 48 hours in a dry environment, the charging capacity of the corresponding battery 7 is 3625.9mAh, the discharge capacity is 3441.5mAh, the first-week efficiency is 94.91%, and the reduction is 0.39%. The protective layer can effectively inhibit the reaction of the pre-lithiated anode and air, and improves the stability of the pre-lithiated anode in air.
The method comprises the following steps: the pre-lithiated negative electrode sheet has higher reactivity, when conventional electrolyte is injected, lithium ions in the pre-lithiated negative electrode interact with the conventional electrolyte to form a thin SEI film on the surface of the electrode sheet, and a protective layer is formed on the surface after washing and drying, so that the protective layer is compact and stable and conducts ions, the stability of electrochemical performance can be ensured, and the safety of the pre-lithiated electrode sheet can be improved.
According to the invention, a protective layer is formed on the surface of the pre-lithiated cathode by a solution treatment method, so that the pre-lithiated cathode is prevented from being contacted with air, and the pre-lithiated pole piece is stored for a long time, and is better compatible with the actual battery manufacturing process.
Claims (9)
1. The preparation method of the pre-lithiated negative electrode plate is characterized by comprising the following steps of:
s1: manufacturing a lithium ion battery negative plate;
s2: pre-lithiation treatment is carried out on the negative electrode plate to obtain a pre-lithiated negative electrode plate;
s3: and (3) in a dry or inert gas environment, placing the pre-lithiated negative electrode sheet into an electrolyte for reaction, washing and drying to form a protective layer on the surface of the pre-lithiated negative electrode sheet.
2. The method for preparing a pre-lithiated negative electrode sheet of claim 1, wherein in step S1, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer covering the surface of the negative electrode current collector; the negative electrode active material layer is one or more compounds selected from carbon materials, silicon-carbon composite materials, silicon oxide materials, tin-based materials and lithium titanate.
3. The method for preparing a pre-lithiated negative electrode sheet of claim 1, wherein in step S2, the pre-lithiation method comprises one or more combinations of stable metallic lithium powder pre-lithiation, lithium foil pre-lithiation, vapor deposition pre-lithiation, magnetron sputtering pre-lithiation, electrochemical pre-lithiation, chemical pre-lithiation, and additive pre-lithiation.
4. The method for preparing a pre-lithiated negative electrode sheet according to claim 1, wherein in step S3, the electrolyte is a mixture of a lithium salt and a solvent, and the lithium salt is one or more of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium perchlorate, lithium dioxalate borate, lithium difluorooxalate borate, lithium diimine, and lithium bistrifluoromethylsulfonyliminate; the solvent is one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, tetrahydrofuran, 2-methyl-tetrahydrofuran, dimethoxymethane and 1, 2-dimethoxyethane.
5. The method for preparing a pre-lithiated negative electrode sheet of claim 1, wherein in step S3, the reaction time of the negative electrode sheet in the electrolyte is 10-60min.
6. The method for preparing the pre-lithiated negative electrode plate according to claim 1, wherein in step S3, the detergent is 2-methyltetrahydrofuran, the washing times are 1-5 times, the drying conditions are 50-70 ℃, and the drying time is 1-3 hours.
7. A lithium ion battery, comprising a positive plate, a diaphragm, an electrolyte and a pre-lithiated negative plate with a protective layer obtained by the preparation method of any one of claims 1-6.
8. The lithium ion battery of claim 7, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer covering the surface of the positive electrode current collector; the positive electrode active material layer is one or more compounds including, but not limited to, lithium cobaltate, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadyl phosphate, lithium vanadate, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, and lithium-rich manganese base.
9. The lithium ion battery of claim 7, wherein the separator is one of a PVDF rubberized separator, a ceramic separator, a PE-based film, and a PP-based film.
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