CN113851603A - Lithium pre-embedding method of negative plate, lithium pre-embedded negative plate and lithium ion battery - Google Patents
Lithium pre-embedding method of negative plate, lithium pre-embedded negative plate and lithium ion battery Download PDFInfo
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- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 210
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 204
- 238000000034 method Methods 0.000 title claims abstract description 50
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 38
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 36
- 239000007773 negative electrode material Substances 0.000 claims abstract description 37
- 239000013589 supplement Substances 0.000 claims abstract description 28
- 238000009830 intercalation Methods 0.000 claims abstract description 23
- 230000002687 intercalation Effects 0.000 claims abstract description 19
- 239000000126 substance Substances 0.000 claims abstract description 17
- 239000011230 binding agent Substances 0.000 claims description 16
- 230000008569 process Effects 0.000 claims description 15
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 14
- 238000010438 heat treatment Methods 0.000 claims description 14
- 239000006258 conductive agent Substances 0.000 claims description 10
- 239000011888 foil Substances 0.000 claims description 8
- 229910002804 graphite Inorganic materials 0.000 claims description 5
- 239000010439 graphite Substances 0.000 claims description 5
- 239000000843 powder Substances 0.000 claims description 5
- 229910021384 soft carbon Inorganic materials 0.000 claims description 4
- 239000002033 PVDF binder Substances 0.000 claims description 3
- 239000004642 Polyimide Substances 0.000 claims description 3
- HMDDXIMCDZRSNE-UHFFFAOYSA-N [C].[Si] Chemical compound [C].[Si] HMDDXIMCDZRSNE-UHFFFAOYSA-N 0.000 claims description 3
- 239000006230 acetylene black Substances 0.000 claims description 3
- 239000002041 carbon nanotube Substances 0.000 claims description 3
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 3
- 230000005674 electromagnetic induction Effects 0.000 claims description 3
- 229910021389 graphene Inorganic materials 0.000 claims description 3
- 229910021385 hard carbon Inorganic materials 0.000 claims description 3
- 239000003273 ketjen black Substances 0.000 claims description 3
- 239000005543 nano-size silicon particle Substances 0.000 claims description 3
- 229920001721 polyimide Polymers 0.000 claims description 3
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 3
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 3
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 3
- 239000003792 electrolyte Substances 0.000 abstract description 27
- 229910052751 metal Inorganic materials 0.000 abstract description 20
- 239000002184 metal Substances 0.000 abstract description 20
- 230000000694 effects Effects 0.000 abstract description 13
- 230000009471 action Effects 0.000 abstract description 11
- 238000002347 injection Methods 0.000 abstract description 9
- 239000007924 injection Substances 0.000 abstract description 9
- 230000008595 infiltration Effects 0.000 abstract description 8
- 238000001764 infiltration Methods 0.000 abstract description 8
- 238000007086 side reaction Methods 0.000 abstract description 8
- 239000000956 alloy Substances 0.000 abstract description 7
- 229910045601 alloy Inorganic materials 0.000 abstract description 7
- 150000001875 compounds Chemical class 0.000 abstract description 7
- 238000011049 filling Methods 0.000 abstract description 3
- 230000000052 comparative effect Effects 0.000 description 9
- 230000009286 beneficial effect Effects 0.000 description 6
- 239000011248 coating agent Substances 0.000 description 4
- 238000000576 coating method Methods 0.000 description 4
- 238000007731 hot pressing Methods 0.000 description 4
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 3
- 239000011889 copper foil Substances 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 238000005096 rolling process Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 229910013872 LiPF Inorganic materials 0.000 description 2
- 101150058243 Lipf gene Proteins 0.000 description 2
- 238000005056 compaction Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 239000007784 solid electrolyte Substances 0.000 description 2
- 238000009736 wetting Methods 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 239000011267 electrode slurry Substances 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000003446 memory effect Effects 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000006479 redox reaction Methods 0.000 description 1
- 230000000284 resting effect Effects 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
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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
- H01M4/04—Processes of manufacture in general
- H01M4/0402—Methods of deposition of the material
- H01M4/0409—Methods of deposition of the material by a doctor blade method, slip-casting or roller coating
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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
- 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
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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
- H01M4/04—Processes of manufacture in general
- H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
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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
- H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
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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
- H01M4/139—Processes of manufacture
- H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
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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
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
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- 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
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
The invention provides a lithium pre-embedding method of a negative plate, a lithium pre-embedded negative plate and a lithium ion battery. The negative plate comprises a negative active material, and the lithium pre-intercalation method comprises the following steps: step S1, adding a lithium source on the surface of the negative plate to obtain a pre-lithium-supplement negative plate; and step S2, baking the lithium pre-filling negative plate in vacuum or inert atmosphere to enable at least part of lithium elements in the lithium source to be embedded into the negative plate, so as to obtain the lithium pre-embedded negative plate. The potential difference between the lithium source and the negative active material is utilized, and the chemical action between the lithium source and the negative active material is accelerated under the action of heat, so that lithium elements in the lithium source are embedded into the negative plate in a compound or alloy mode, and the obtained pre-embedded lithium negative plate is used as the negative plate of the lithium ion battery, so that the problems of poor electrolyte infiltration effect caused by metal lithium on the surface of the negative electrode, short cycle life of the lithium ion battery caused by side reaction of electrolyte components and the metal lithium during electrolyte injection and the like in the prior art are solved.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a lithium pre-embedding method of a negative plate, a lithium pre-embedded negative plate and a lithium ion battery.
Background
The lithium ion battery has the advantages of high energy density, long cycle life, no memory effect and the like, so that the lithium ion battery becomes the first choice of consumer electronic batteries and new energy automobile power batteries. However, lithium loss caused by the formation of a Solid Electrolyte Interface (SEI) film in the first charge-discharge process of the lithium ion battery electrode material limits the exertion of the energy density of the lithium ion battery, and is particularly obvious in a silicon-based negative electrode material system, and the cycle life of the lithium ion battery is shortened due to the loss of active lithium caused by side reactions in the cycle process. Lithium supplement to the pole piece is an effective means for improving the energy density and the cycle life of the lithium ion battery.
At present, adding metal lithium on the surface of a negative electrode is the most effective technical scheme for lithium supplement, two lithium sources of lithium powder and a lithium belt are mainly used in the prior art, but a layer of metal lithium is arranged on the surface of a negative electrode plate after lithium supplement, which not only causes poor contact between the negative electrode and a diaphragm, but also influences the infiltration of electrolyte on the negative electrode plate, and generates side reaction with electrolyte components after the electrolyte is injected, a film forming additive is consumed, and the performance of a lithium ion battery is further deteriorated by the obtained by-products.
Disclosure of Invention
The invention mainly aims to provide a method for pre-embedding lithium into a negative plate, the pre-embedded lithium negative plate and a lithium ion battery, so as to solve the problem that the negative plate after lithium supplement in the prior art has poor infiltration effect in an electrolyte.
In order to achieve the above object, according to one aspect of the present invention, there is provided a pre-lithium intercalation method of a negative electrode sheet, the negative electrode sheet including a negative electrode active material, the pre-lithium intercalation method including: step S1, adding a lithium source on the surface of the negative plate to obtain a pre-lithium-supplement negative plate; and step S2, baking the lithium pre-filling negative plate in vacuum or inert atmosphere to enable at least part of lithium elements in the lithium source to be embedded into the negative plate, so as to obtain the lithium pre-embedded negative plate.
Further, the baking temperature is 30-100 ℃, preferably 40-90 ℃, and the baking time is preferably 6-48 h.
Further, the baking comprises a two-stage baking process, wherein the two-stage baking process comprises: the method comprises the steps of carrying out first-stage baking on a lithium pre-supplement negative plate at 40-60 ℃ to obtain a first-stage baked negative plate, and carrying out second-stage baking on the first-stage baked negative plate at 60-90 ℃ to obtain a lithium pre-embedded negative plate, wherein the first-stage baking time is preferably 1-12 hours, the second-stage baking time is preferably 6-24 hours, and the heating rates of the first-stage baking and the second-stage baking are preferably 0.5-2 ℃/min respectively and independently.
Further, the thickness of the lithium source is 2-10 μm, preferably, the lithium source is a lithium metal simple substance, and preferably, the lithium metal simple substance is lithium powder or lithium foil.
Further, the baking is performed by any one of oven heat baking, electromagnetic induction type heating baking, and near-infrared heating baking.
Further, before the step S2, the method for pre-lithium intercalation further includes: assembling the lithium pre-supplement negative plate, the positive plate and the diaphragm to obtain a bare cell; and step S2, baking the naked battery cell.
Further, the negative plate comprises a negative current collector and a negative material, the negative material comprises a negative active material, a conductive agent and a binder, and the mass ratio of the negative active material to the conductive agent to the binder is preferably 87-97: 1-8: 2 to 5.
Further, the negative electrode active material is selected from any one or more of graphite, soft carbon, hard carbon, nano silicon carbon and SiO, the binder is preferably selected from any one or more of PVDF, CMC, PVA, PAA, PTFE, SBR, LA series binders and polyimide, and the electrical agent is preferably selected from any one or more of carbon nano tube, Ketjen black, carbon black, acetylene black, Super p, ks6 and graphene.
According to another aspect of the invention, the lithium pre-intercalation negative electrode sheet is prepared by adopting the lithium pre-intercalation method.
According to still another aspect of the present invention, there is provided a lithium ion battery comprising a positive electrode unit, a negative electrode unit and a separator, wherein the negative electrode unit is the above-mentioned pre-lithium-intercalation negative electrode sheet.
By applying the technical scheme of the invention, the pre-lithium-added negative plate is baked in vacuum or inert atmosphere, and because the potential difference exists between the lithium source and the negative active material, the chemical action between the lithium source and the negative active material is accelerated under the action of heat, so that the lithium element in the lithium source is embedded into the negative plate in the form of a compound or an alloy, and the pre-lithium-added negative plate is obtained. The lithium pre-embedded negative plate is used for preparing the negative plate of the lithium ion battery, and can solve the problems of poor electrolyte infiltration effect caused by metal lithium on the surface of the negative plate, short cycle life of the lithium ion battery caused by side reaction of electrolyte components and the metal lithium during electrolyte injection and the like in the prior art.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail with reference to examples.
As analyzed by the background art, in the prior art, the negative plate after lithium supplement has a poor wetting effect in the electrolyte, and in order to solve the problem, the invention provides a method for pre-embedding lithium into the negative plate, the pre-embedded lithium negative plate and a lithium ion battery.
In an exemplary embodiment of the present application, there is provided a pre-lithium intercalation method of a negative electrode sheet including a negative electrode active material, the pre-lithium intercalation method including: step S1, adding a lithium source on the surface of the negative plate to obtain a pre-lithium-supplement negative plate; and step S2, baking the lithium pre-filling negative plate in vacuum or inert atmosphere to enable at least part of lithium elements in the lithium source to be embedded into the negative plate, so as to obtain the lithium pre-embedded negative plate.
According to the method, the lithium pre-added negative plate is baked in vacuum or inert atmosphere, and due to the fact that potential difference exists between the lithium source and the negative active material, under the action of heat, the chemical action between the lithium source and the negative active material is accelerated, so that lithium elements in the lithium source are embedded into the negative plate in the form of compounds or alloys, and the lithium pre-added negative plate is obtained. The lithium pre-embedded negative plate is used for preparing the negative plate of the lithium ion battery, and can solve the problems of poor electrolyte infiltration effect caused by metal lithium on the surface of the negative plate, short cycle life of the lithium ion battery caused by side reaction of electrolyte components and the metal lithium during electrolyte injection and the like in the prior art.
The inert atmosphere may be an inert gas such as argon or helium.
In an embodiment of the present application, the baking temperature is 30 to 100 ℃, preferably 40 to 90 ℃, and the baking time is preferably 6 to 48 hours. The baking temperature can promote the lithium source to diffuse into the negative plate as much as possible and accelerate the chemical action between the lithium source and the negative active material, so that the lithium element is finally embedded into the negative plate, and the residual of the metal lithium on the surface of the negative plate is reduced as much as possible. Meanwhile, the method is beneficial to avoiding damaging components such as a binder in the negative plate at an excessively high baking temperature.
In some embodiments, the baking comprises a two-stage baking process, the two-stage baking process comprising: the method comprises the steps of carrying out first-stage baking on a lithium pre-supplement negative plate at 40-60 ℃ to obtain a first-stage baked negative plate, and carrying out second-stage baking on the first-stage baked negative plate at 60-90 ℃ to obtain a lithium pre-embedded negative plate, wherein the first-stage baking time is preferably 1-12 hours, the second-stage baking time is preferably 6-24 hours, and the heating rates of the first-stage baking and the second-stage baking are preferably 0.5-2 ℃/min respectively and independently. Compared with one-section baking, the adoption of the two-section baking process and the control of the baking temperature and the heating rate of each section are more beneficial to the stable control of the baking process, thereby reducing the side effect caused by overlarge temperature fluctuation.
The thickness of the lithium source is too small, the amount of the lithium source embedded into the negative plate is too small, the thickness of the lithium source is too large, and partial lithium source can not be embedded into the negative plate easily, the thickness of the lithium source is preferably 2-10 μm, the lithium source is preferably a lithium metal simple substance, and the lithium metal simple substance is preferably lithium powder or lithium foil. On one hand, the lithium ion battery is more favorable for playing the thermal diffusion effect of the lithium source entering the negative plate during baking, and on the other hand, the potential difference between the lithium simple substance and the negative active material can promote the lithium source to be completely oxidized into lithium ions and be embedded into the negative plate in the form of a compound or an alloy. The control of the thickness of the lithium source is beneficial to leading the surface capacity of lithium supplement on the surface of the negative electrode to reach 0.2-2.0 mAh/cm2。
The baking in the present application mainly means heating in a dry environment, and therefore any baking method capable of achieving the object is considered to be applicable to the present application, and the baking method is preferably any one selected from oven heat baking, electromagnetic induction type heat baking, and near infrared heat baking. Not only can better control the baking process, but also is beneficial to reducing the cost.
The method can be used for manufacturing the lithium pre-supplement negative plate. In an embodiment of the present application, before the step S2, the method for pre-lithium intercalation further includes: assembling the lithium pre-supplement negative plate, the positive plate and the diaphragm to obtain a bare cell; and step S2, baking the naked battery cell.
This application also can be toasted naked electric core after assembling into it with mending lithium negative pole piece in advance to when the realization imbeds the negative pole piece with the lithium source inside, can be as far as possible again with the steam evaporation that gets into naked electric core in the assembling process, thereby further improve the electrical property of naked electric core.
In addition, the assembly process can adopt a common battery cell assembly process in the field, for example, a hot pressing process is adopted to assemble the lithium pre-supplement negative electrode plate, the positive electrode plate and the diaphragm, in order to improve the assembly efficiency of the bare battery cell, the preferred hot pressing temperature is 60-100 ℃, the hot pressing pressure is 5-15 t, and the hot pressing time is 10-60 s.
In some embodiments of the present application, the negative electrode sheet includes a negative electrode current collector and a negative electrode material, where the negative electrode current collector may be a current collector used in a conventional negative electrode, which is not repeated herein. Preferably, the negative electrode material comprises a negative electrode active material, a conductive agent and a binder, and the mass ratio of the negative electrode active material to the conductive agent to the binder is preferably 87-97: 1-8: 2 to 5.
According to the method, natural potential difference between a lithium simple substance and a negative electrode active material is utilized, and in order to further utilize the potential difference to achieve a better lithium intercalation effect, the negative electrode active material is preferably selected from any one or more of graphite, soft carbon, hard carbon, nano silicon carbon and SiO. The potential difference between the carbon material and the lithium simple substance is more beneficial to oxidizing the lithium simple substance into lithium ions through oxidation-reduction reaction between the lithium simple substance and the negative active material, and the lithium ions are combined with the negative active material in a compound or alloy mode, so that the negative plate is embedded by lithium.
In one embodiment of the present application, the preferred binder is selected from any one or more of PVDF, CMC, PVA, PAA, PTFE, SBR, LA series binders, and polyimide.
On one hand, the kind of the binder can ensure the firmness of the negative electrode slurry on the negative electrode current collector, and on the other hand, the negative electrode active material, the conductive agent and the binder in the proportion are beneficial to exerting the respective performances of the negative electrode active material and the conductive agent.
Preferably, the conductive agent is selected from one or more of carbon nanotubes, ketjen black, carbon black, acetylene black, Super p, ks6, and graphene. Therefore, the adaptability of the lithium pre-intercalated negative electrode plate to the negative electrode active material and the binder is favorably improved, and the conductivity of the lithium pre-intercalated negative electrode plate is favorably improved.
In another exemplary embodiment of the present application, a pre-lithium intercalation negative electrode sheet is provided, which is prepared by the aforementioned pre-lithium intercalation method.
And baking the lithium pre-embedded negative plate in vacuum or inert atmosphere, wherein the chemical action between the lithium source and the negative active material is accelerated under the action of heat due to the potential difference between the lithium source and the negative active material, so that lithium in the lithium source is embedded into the negative plate in the form of a compound or an alloy to obtain the lithium pre-embedded negative plate. The lithium pre-embedded negative plate is used for preparing the negative plate of the lithium ion battery, and can solve the problems of poor electrolyte infiltration effect caused by metal lithium on the surface of the negative plate, short cycle life of the lithium ion battery caused by side reaction of electrolyte components and the metal lithium during electrolyte injection and the like in the prior art.
In yet another exemplary embodiment of the present application, there is provided a lithium ion battery including a positive electrode unit, a negative electrode unit, and a separator, the negative electrode unit being the above-described pre-lithium-intercalation negative electrode sheet.
The lithium ion battery prepared by the pre-embedded lithium negative plate obtained by embedding lithium into the negative active material can solve the problems of poor electrolyte infiltration effect, side reaction between electrolyte components and metal lithium during electrolyte injection and the like caused by metal lithium on the surface of the negative electrode in the prior art, thereby improving the energy density and the cycle life of the lithium ion battery.
The preparation process of the lithium ion battery comprises the process of electrolyte injection on a bare cell, preferably adopts the mode of high-temperature cell injection and placement, and the temperature of an injection cell and the resting temperature are 30-60 ℃, preferably 40-50 ℃, so that a better solid electrolyte interface film can be formed on the surface of a negative electrode.
The advantageous effects of the present application will be described below with reference to specific examples and comparative examples.
Example 1
Uniformly mixing 95 parts of graphite, 1 part of SP, 1.5 parts of CMC and 2.5 parts of SBR, coating the mixture on the surface of a copper foil current collector to obtain a negative plate, drying the negative plate, rolling the negative plate to a designed compaction density, and attaching an ultrathin metal lithium foil with the thickness of 4 microns to the surface of the negative plate to obtain the lithium pre-supplement negative plate. And placing the lithium pre-added negative plate in a vacuum oven at 80 ℃ for baking for 12h to finish the embedding of lithium elements into the negative plate, thereby obtaining the lithium pre-embedded negative plate.
Example 2
And uniformly mixing 85 parts of graphite, 10 parts of SiO, 1 part of SP, 1.5 parts of CMC and 2.5 parts of SBR, coating the mixture on the surface of a copper foil current collector to obtain a negative plate, drying the negative plate, rolling the negative plate to 70% of designed compaction density, coating 5 mu m of lithium powder on the surface of the negative plate, and rolling the negative plate to obtain the lithium pre-supplement negative plate. And placing the lithium pre-added negative plate in a vacuum oven at 60 ℃ for baking for 24h to finish the embedding of lithium elements into the negative plate, thereby obtaining the lithium pre-embedded negative plate.
Example 3
Example 3 differs from example 1 in that,
and (3) attaching an ultrathin metal lithium foil with the thickness of 2 microns to the surface of the negative electrode to finally obtain the pre-lithium-supplement negative electrode plate.
Example 4
Example 4 differs from example 1 in that,
and (3) attaching an ultrathin metal lithium foil with the thickness of 10 microns to the surface of the negative electrode to finally obtain the pre-lithium-supplement negative electrode plate.
Example 5
Example 5 differs from example 1 in that,
and (3) attaching an ultrathin metal lithium foil with the thickness of 1.5 microns to the surface of the negative electrode to finally obtain the lithium pre-supplement negative electrode plate.
Example 6
Example 6 differs from example 1 in that,
and (3) attaching an ultrathin metal lithium foil with the thickness of 12 microns to the surface of the negative electrode to finally obtain the pre-lithium-supplement negative electrode plate.
Example 7
Example 7 differs from example 1 in that,
and placing the lithium pre-added negative plate in a vacuum oven at 40 ℃ for baking for 12h to finish the embedding of lithium elements into the negative plate, and finally obtaining the lithium pre-embedded negative plate.
Example 8
Example 8 differs from example 1 in that,
and placing the lithium pre-added negative plate in a vacuum oven at 90 ℃ for baking for 12h to finish the embedding of lithium elements into the negative plate, and finally obtaining the lithium pre-embedded negative plate.
Example 9
Example 9 differs from example 1 in that,
and placing the lithium pre-added negative plate in a vacuum oven at 30 ℃ for baking for 12h to finish the embedding of lithium elements into the negative plate, and finally obtaining the lithium pre-embedded negative plate.
Example 10
Example 10 differs from example 1 in that,
and placing the lithium pre-added negative plate in a vacuum oven at 100 ℃ for baking for 12h to finish the embedding of lithium elements into the negative plate, and finally obtaining the lithium pre-embedded negative plate.
Example 11
Example 11 differs from example 1 in that,
and placing the lithium pre-added negative plate in a vacuum oven at 80 ℃ for baking for 6h to finish the embedding of lithium elements into the negative plate, and finally obtaining the lithium pre-embedded negative plate.
Example 12
Example 12 differs from example 1 in that,
and placing the lithium pre-added negative plate in a vacuum oven at 80 ℃ for baking for 48h to finish the embedding of lithium elements into the negative plate, and finally obtaining the lithium pre-embedded negative plate.
Example 13
Example 13 differs from example 1 in that,
and (3) carrying out first-stage baking on the lithium pre-added negative plate at 40 ℃ for 12h to obtain a primary baked negative plate, carrying out second-stage baking on the primary baked negative plate at 60 ℃ for 18h to obtain a lithium pre-embedded negative plate, wherein the heating rates of the first-stage baking and the second-stage baking are respectively 1 ℃/min independently, and finally obtaining the lithium pre-embedded negative plate.
Example 14
Example 14 differs from example 13 in that,
and (3) baking the lithium pre-added negative plate at 50 ℃ for the first period to obtain a baked negative plate, and finally obtaining the lithium pre-embedded negative plate.
Example 15
Example 15 differs from example 13 in that,
and (3) carrying out first-stage baking on the lithium pre-supplement negative plate at the temperature of 60 ℃ to obtain a primary baked negative plate, and finally obtaining the lithium pre-embedded negative plate.
Example 16
Example 16 differs from example 13 in that,
and (3) carrying out first-stage baking on the lithium pre-supplement negative plate at the temperature of 30 ℃ to obtain a primary baked negative plate, and finally obtaining the lithium pre-embedded negative plate.
Example 17
Example 17 differs from example 13 in that,
and (3) carrying out second-stage baking on the negative plate subjected to the primary baking at 75 ℃ to finally obtain the pre-embedded lithium negative plate.
Example 18
Example 18 differs from example 13 in that,
and (3) carrying out second-stage baking on the negative plate subjected to the primary baking at 90 ℃ to finally obtain the pre-embedded lithium negative plate.
Example 19
Example 19 differs from example 13 in that,
and (3) carrying out second-stage baking on the negative plate subjected to the primary baking at 50 ℃ to finally obtain the pre-embedded lithium negative plate.
Example 20
Example 20 differs from example 13 in that,
the heating rates of the first stage baking and the second stage baking are respectively 0.5 ℃/min independently, and finally the pre-embedded lithium negative plate is obtained.
Example 21
Example 21 differs from example 13 in that,
the heating rates of the first stage baking and the second stage baking are respectively and independently 2 ℃/min, and finally the pre-embedded lithium negative plate is obtained.
Example 22
Example 22 differs from example 13 in that,
the heating rates of the first stage baking and the second stage baking are respectively 0.3 ℃/min independently, and finally the pre-embedded lithium negative plate is obtained.
Example 23
Example 23 differs from example 13 in that,
the heating rates of the first stage baking and the second stage baking are respectively and independently 2.5 ℃/min, and finally the pre-embedded lithium negative plate is obtained.
Example 24
Example 24 differs from example 13 in that,
the time for the first stage of baking is 1h, the time for the second stage of baking is 24h, and finally the pre-embedded lithium negative plate is obtained.
Example 25
Example 25 differs from example 13 in that,
the time for the first stage of baking is 10 hours, the time for the second stage of baking is 6 hours, and finally the pre-embedded lithium negative plate is obtained.
Example 26
Example 26 differs from example 1 in that,
and uniformly mixing 96.5 parts of soft carbon, 1 part of SP, 1 part of PAA and 1.5 parts of SBR, and coating the mixture on the surface of a copper foil current collector to finally obtain the pre-embedded lithium negative electrode plate.
Comparative example 1
Comparative example 1 is different from example 1 in that,
the pre-lithium-supplement negative plate is not baked.
Comparative example 2
Comparative example 2 is different from example 2 in that,
the pre-lithium-supplement negative plate is not baked.
The pre-lithium-embedded negative electrode sheets of the above examples 1, 3 to 26 and comparative example 1, the lithium iron phosphate positive electrode and the PE diaphragm are respectively combined into a cell, and LiPF is injected6EC is EMC 3:7 electrolyte; lithium-insertion negative electrode sheets obtained in example 2 and comparative example 2, NCM811 positive electrode and PE diaphragm were assembled into a cell, and LiPF was injected6And EC EMC FEC 3:6:1 electrolyte to obtain a lithium ion battery.
The lithium ion batteries of example 1, example 2, examples 3 to 26, comparative example 1 and comparative example 2 were each tested for capacity (0.33C rate), 50% SOC dc resistance, electrolyte wetting time, and cycle life (1C/1C charge/discharge rate), and the test results are shown in table 1.
TABLE 1
From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects:
according to the method, the lithium pre-added negative plate is baked in vacuum or inert atmosphere, and due to the fact that potential difference exists between the lithium source and the negative active material, under the action of heat, the chemical action between the lithium source and the negative active material is accelerated, so that lithium elements in the lithium source are embedded into the negative plate in the form of compounds or alloys, and the lithium pre-added negative plate is obtained. The lithium pre-embedded negative plate is used for preparing the negative plate of the lithium ion battery, and can solve the problems of poor electrolyte infiltration effect caused by metal lithium on the surface of the negative plate, short cycle life of the lithium ion battery caused by side reaction of electrolyte components and the metal lithium during electrolyte injection and the like in the prior art.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement 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 method for pre-intercalating lithium in a negative electrode sheet including a negative electrode active material, the method comprising:
step S1, adding a lithium source on the surface of the negative plate to obtain a pre-lithium-supplement negative plate;
step S2, baking the lithium pre-intercalation negative electrode sheet in vacuum or inert atmosphere to enable at least part of lithium elements in the lithium source to be intercalated into the negative electrode sheet, so as to obtain the lithium pre-intercalation negative electrode sheet.
2. The method for pre-embedding lithium according to claim 1, wherein the baking temperature is 30-100 ℃, preferably 40-90 ℃, and the baking time is preferably 6-48 h.
3. The method of pre-intercalating lithium according to claim 1 or 2, wherein said baking comprises a two-stage baking process comprising:
the pre-lithium-supplement negative plate is subjected to first-stage baking at the temperature of 40-60 ℃ to obtain a primary baked negative plate,
carrying out second-stage baking on the primarily baked negative plate at the temperature of 60-90 ℃ to obtain the pre-lithium-embedded negative plate,
preferably, the time for the first stage of baking is 1-12 hours, the time for the second stage of baking is 6-24 hours, and the heating rates of the first stage of baking and the second stage of baking are 0.5-2 ℃/min respectively and independently.
4. The method according to claim 1, wherein the thickness of the lithium source is 2-10 μm, preferably the lithium source is a lithium metal simple substance, preferably the lithium metal simple substance is lithium powder or lithium foil.
5. The method for pre-embedding lithium according to any one of claims 1 to 4, wherein the baking manner is selected from any one of oven thermal baking, electromagnetic induction type heating baking and near infrared heating baking.
6. The pre-lithium intercalation method according to any of the claims 1 to 5, wherein before said step S2, said pre-lithium intercalation method further comprises:
assembling the lithium pre-supplement negative plate, the positive plate and the diaphragm to obtain a bare cell;
and the step S2 is used for baking the naked battery cell.
7. The pre-lithium intercalation method according to any one of claims 1 to 5, wherein the negative electrode sheet comprises a negative electrode current collector and a negative electrode material, the negative electrode material comprises the negative electrode active material, a conductive agent and a binder, and the mass ratio of the negative electrode active material, the conductive agent and the binder is preferably 87-97: 1-8: 2 to 5.
8. The pre-lithium intercalation method according to claim 7, wherein the negative active material is selected from any one or more of graphite, soft carbon, hard carbon, nano silicon carbon, SiO, preferably the binder is selected from any one or more of PVDF, CMC, PVA, PAA, PTFE, SBR, LA series binders and polyimide, preferably the conductive agent is selected from any one or more of carbon nanotube, Ketjen black, carbon black, acetylene black, Super p, ks6, graphene.
9. A lithium pre-intercalated negative electrode sheet prepared by the lithium pre-intercalation method according to any one of claims 1 to 8.
10. A lithium ion battery comprising a positive electrode unit, a negative electrode unit and a diaphragm, wherein the negative electrode unit is the pre-lithium-intercalated negative electrode sheet defined in claim 9.
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| CN114678494A (en) * | 2022-03-28 | 2022-06-28 | 蜂巢能源科技股份有限公司 | Method for pre-lithiating negative electrode and simultaneously obtaining SEI (solid electrolyte interface) film, negative electrode and lithium ion battery |
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