CN112886011A - Composite lithium supplementing film and preparation method and application thereof - Google Patents

Composite lithium supplementing film and preparation method and application thereof Download PDF

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Publication number
CN112886011A
CN112886011A CN202110003678.5A CN202110003678A CN112886011A CN 112886011 A CN112886011 A CN 112886011A CN 202110003678 A CN202110003678 A CN 202110003678A CN 112886011 A CN112886011 A CN 112886011A
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lithium
layer
supplement
ion conductor
film
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李文龙
赵育松
邱昭政
梁世硕
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Kunshan Bao Innovative Energy Technology Co Ltd
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Kunshan Bao Innovative Energy Technology Co Ltd
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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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • 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
    • 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
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/381—Alkaline or alkaline earth metals elements
    • H01M4/382—Lithium
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • 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 discloses a composite lithium supplementing film and a preparation method and application thereof, wherein the composite lithium supplementing film comprises: buffer layer, lithium supplement layer and protective layer. The buffer layer comprises an ion conductive material, so that the lithium insertion speed and the lithium insertion uniformity of lithium ions in the pre-lithiation process of the lithium supplement layer can be reduced, the generation of lithium dendrites after lithium supplement is inhibited, and the potential safety hazard is reduced; the lithium supplement layer is arranged on the surface of the buffer layer and comprises a lithium supplement material and an ion conductor material, so that the loss of active lithium can be made up in the charge-discharge process, and the first coulombic efficiency and specific capacity of the lithium ion battery are improved; the protective layer is arranged on the surface of the lithium supplement layer, so that the lithium supplement layer can be prevented from being etched by electrolyte or ambient atmosphere, and a relatively stable state is maintained in the production and storage processes. Therefore, the composite lithium supplementing film can improve the safety performance and the pre-lithiation effect of the lithium supplementing pole piece while improving the electrochemical performance of the battery, and obviously improves the energy density and the cycling stability of the lithium ion battery.

Description

Composite lithium supplementing film and preparation method and application thereof
Technical Field
The invention belongs to the technical field of energy storage devices, and particularly relates to a composite lithium supplement film and a preparation method and application thereof.
Background
The lithium ion battery is widely applied to the fields of portable electronic devices, electric automobiles, smart power grids and the like. In recent years, with the rapid development of new energy automobiles, smart grids and distributed energy storage, higher requirements are put forward on the energy density of energy storage devices. However, the safety problems of lithium ion batteries, insufficient energy density and failure to operate under extreme atmospheric conditions limit their further development. The graphite cathode of the traditional lithium ion battery can not meet the existing requirements, and the high-energy-density cathode material becomes a new hot spot pursued by enterprises.
The silicon-based material cathode is the most preferred cathode improving material for battery enterprises and lithium battery manufacturers due to the abundant reserve capacity and the ultrahigh theoretical specific capacity, and is one of the most potential next-generation lithium ion battery cathode materials. In the first charging process of the lithium ion battery, the organic electrolyte can be reduced and decomposed on the surface of a negative electrode such as graphite and the like to form a Solid Electrolyte Interface (SEI) film, so that a large amount of lithium from the positive electrode is permanently consumed, the coulomb efficiency of the first cycle is low, and the capacity and the energy density of the lithium ion battery are reduced. The existing graphite material has 5% -10% of first irreversible lithium loss, and for a high-capacity negative electrode material silicon, under the condition of complete lithium intercalation, the specific capacity can reach 4200mAh/g, but the specific capacity is accompanied by volume expansion of up to 300%, so that the pure silicon material can be subjected to particle crushing and differentiation in the lithium intercalation process, an SEI film is continuously formed to lose lithium from a positive electrode, and the irreversible capacity loss of silicon reaches 15% -35%. Because of the problems of pure Si, attempts have been made to use another silicon oxide-SiOxAs a cathode material, the bonding energy of Si-O bond is twice of that of Si-Si bond, meanwhile, Li reacts with O element in the material in the process of lithium intercalation,generation of LixAnd O, the oxides of Li lose activity subsequently, and become a buffer layer inside the silicon oxide particles, so that the volume expansion of the material can be well inhibited in the charge-discharge process, and the cycle performance of the material is improved. Due to SiOxThe first lithium intercalation process generates metallic lithium oxide LixO, which results in the first coulombic efficiency of the silicon oxide material being only about 70%, and in recent years, through many technological improvements, the first efficiency is also only improved by about 80%, which is far from 90% of the graphite material, while the lithium supplement technology can effectively avoid the shortage of the silicon-carbon negative electrode, and improve the energy density, specifically, the lithium supplement technology mainly includes two aspects: on one hand, the content of active lithium ions is increased, the loss of active lithium in the first-week charging and discharging process is compensated, and the first-week reversible capacity of the battery is improved. On the other hand, the volume of the negative electrode material is pre-expanded, the cracking and polarization of material particles in the lithium embedding process are reduced, and the mechanical stability and the cyclicity of the negative electrode are improved. However, the lithium supplement technology also has the difficulties of high technical barrier, strict environmental requirements and the like, and once the lithium supplement process is not good in holding, lithium dendrite is easily caused.
Researchers increase the addition amount of a positive electrode material, use a pre-lithiation additive, use an electrochemical pre-lithiation additive, pre-lithiate an electrode in a contact short circuit mode and the like, and can compensate the irreversible capacity loss of the first circulation to a certain extent. The stabilized lithium powder has the advantages of simple process, easy operation, low cost and suitability for large-scale production and is widely researched. Has great application prospect in the prelithiation process of the lithium ion battery. At present, researchers adopt the following lithium powder lithium supplementing processes, the simplest and most direct method is a direct mixing method, namely lithium powder is added in the process of pulping of a negative electrode material, but by the method, a plurality of cavities are left in the pole piece or on the surface of the pole piece after the lithium powder is dissolved, so that not only is the compaction density reduced, but also lithium dendrites are possibly generated in a thinner area of the pole piece; the other is a spraying method, i.e. spraying lithium powder on the surface of the prepared cathode, which is mainly divided into dry spraying and wet spraying. Lithium powder is sprayed on the surface of the negative electrode by a dry method to supplement lithium, so that the lithium powder is convenient and direct in practical application operation, but the method has great potential safety hazard due to the existence of large dust; meanwhile, the fluctuation range of the prelithiation is wide by a dusting mode and is difficult to control. Some people dissolve lithium powder in an organic solvent and spray the lithium powder on the surface of the negative plate, although the dust problem encountered by dry spraying is effectively solved by the wet spraying, the lithium powder has low density and is easy to float, and the lithium powder is difficult to disperse uniformly when being directly added into the solvent.
Thus, the existing prelithiation processes are in need of improvement.
Disclosure of Invention
The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, one object of the present invention is to provide a composite lithium supplementing film, a preparation method and an application thereof, wherein the composite lithium supplementing film can compensate for the loss of active lithium during the charge and discharge process, and improve the first coulomb efficiency and energy density of a lithium ion battery.
In one aspect of the invention, a composite lithium replenishment film is provided. According to an embodiment of the present invention, the lithium replenishment film includes:
a buffer layer comprising an ion conducting material;
a lithium supplement layer provided on a surface of the buffer layer, and including a lithium supplement material and an ion conductor material;
and the protective layer is arranged on the surface of the lithium supplement layer.
According to the composite lithium supplementing film provided by the embodiment of the invention, the composite lithium supplementing film comprises the buffer layer, the lithium supplementing layer and the protective layer, wherein the buffer layer comprises the ion conducting material, so that the lithium embedding speed and the lithium embedding uniformity of lithium ions in the pre-lithiation process of the lithium supplementing layer can be reduced, the generation of lithium dendrites after lithium supplementation is inhibited, the potential safety hazard is reduced, the use efficiency of lithium powder is further improved, and the lithium supplementing amount and the lithium supplementing effect are ensured; the lithium supplement layer is arranged on the surface of the buffer layer and comprises a lithium supplement material and an ion conductor material, the lithium supplement material of the lithium supplement layer can effectively replace lithium from a positive electrode consumed when an SEI film is formed on a negative electrode, so that the loss of active lithium can be compensated in the charging and discharging process, the first coulombic efficiency and the specific capacity of the lithium ion battery are improved, in addition, the defects that the lithium supplement material is high in activity, not easy to disperse, difficult to use and the like can be overcome by adding the ion conductor material in the lithium supplement layer, and the prepared lithium supplement layer has quick lithium ion conductivity; the protective layer is arranged on the surface of the lithium supplement layer, so that the lithium supplement layer can be prevented from being etched by electrolyte or ambient atmosphere, and the relatively stable state of the composite lithium supplement film is maintained in the production and storage processes. Therefore, the composite lithium supplementing film can improve the safety performance and the pre-lithiation effect of the lithium supplementing pole piece while improving the electrochemical performance of the battery, and obviously improves the energy density and the cycling stability of the lithium ion battery.
In addition, the composite lithium supplement film according to the above embodiment of the present invention may further have the following additional technical features:
in some embodiments of the present invention, the buffer layer has a thickness of 1 to 5 μm. Therefore, the lithium inserting speed and the lithium inserting uniformity of lithium ions in the lithium inserting layer pre-lithiation process can be reduced, the generation of lithium dendrites after lithium inserting is restrained, potential safety hazards are reduced, the service efficiency of lithium powder is further improved, and the lithium inserting amount and the lithium inserting effect are guaranteed.
In some embodiments of the present invention, the thickness of the lithium supplement layer is 1 to 20 μm. Therefore, the loss of active lithium can be made up in the charging and discharging process, and the first coulomb efficiency and specific capacity of the lithium ion battery are improved.
In some embodiments of the present invention, the particle size of the lithium supplement material is 0.5 to 5 microns. Therefore, the loss of active lithium can be made up in the charging and discharging process, and the first coulomb efficiency and specific capacity of the lithium ion battery are improved.
In some embodiments of the present invention, the thickness of the protective layer is 1 to 10 μm. Therefore, the lithium supplement layer can be prevented from being etched by the electrolyte or the ambient atmosphere, and a relatively stable state can be maintained in the production and storage processes.
In some embodiments of the invention, the buffer layer comprises at least one of an ion conductor polymer, an ion conductor oxide, and an electron conductor material. Therefore, the lithium inserting speed and the lithium inserting uniformity of lithium ions in the lithium inserting layer pre-lithiation process can be reduced, the generation of lithium dendrites after lithium inserting is restrained, potential safety hazards are reduced, the service efficiency of lithium powder is further improved, and the lithium inserting amount and the lithium inserting effect are guaranteed.
In some embodiments of the present invention, the buffer layer includes 30 to 70 parts by weight of the ion conductor polymer, 30 to 70 parts by weight of the ion conductor oxide, and 0.05 to 0.5 parts by weight of the electron conductor material. Therefore, the lithium inserting speed and the lithium inserting uniformity of lithium ions in the lithium inserting layer pre-lithiation process can be reduced, the generation of lithium dendrites after lithium inserting is restrained, potential safety hazards are reduced, the service efficiency of lithium powder is further improved, and the lithium inserting amount and the lithium inserting effect are guaranteed.
In some embodiments of the invention, the ion conductor material comprises at least one of an ion conductor polymer and an ion conductor oxide. Therefore, the defects of high activity, difficult dispersion, difficult use and the like of the lithium supplement material can be overcome by adding a small amount of the ion conductor material into the lithium supplement material, so that the prepared lithium supplement layer has quick lithium ion conductivity.
In some embodiments of the present invention, the lithium supplement layer includes 50 to 95 parts by weight of the lithium supplement material, 0.5 to 5 parts by weight of the ion conductor polymer, and 0 to 50 parts by weight of the ion conductor oxide. Therefore, the loss of active lithium can be made up in the charging and discharging process, and the first coulomb efficiency and specific capacity of the lithium ion battery are improved.
In some embodiments of the invention, the protective layer comprises at least one of the ion conductor polymer and the ion conductor oxide. Therefore, the lithium supplement layer can be prevented from being etched by the electrolyte or the ambient atmosphere, and a relatively stable state can be maintained in the production and storage processes.
In some embodiments of the present invention, the protective layer includes 30 to 70 parts by weight of the ion conductor polymer and 30 to 70 parts by weight of the ion conductor oxide. Therefore, the lithium supplement layer can be prevented from being etched by the electrolyte or the ambient atmosphere, and a relatively stable state can be maintained in the production and storage processes.
In some embodiments of the present invention, the lithium supplement material includes at least one of metallic lithium powder, lithium silicon alloy, lithium tin alloy, lithium magnesium alloy, lithium copper alloy, lithium germanium alloy, lithium-containing oxide, lithium-containing sulfide, lithium-containing nitride, and lithium-containing fluoride. Therefore, the loss of active lithium can be made up in the charging and discharging process, and the first coulomb efficiency and specific capacity of the lithium ion battery are improved.
In some embodiments of the present invention, the ionic conductor polymer comprises at least one of polyethylene oxide or a modification thereof, polyvinylidene fluoride or a modification thereof, a polyacrylate polymer or a modification thereof, a polyacrylonitrile polymer or a modification thereof, a polyether polymer or a modification thereof, a polysiloxane or a modification thereof, and a polyanionic single-ion conductor polymer.
In some embodiments of the invention, the ion conductor oxide comprises at least one of a perovskite-type lithium ion conductor LLTO, a LISICON-type lithium ion conductor LZGO, and a garnet-type lithium ion conductor LLZO.
In some embodiments of the present invention, the electron conductor material comprises at least one of graphite, graphene, carbon nanotubes, carbon fibers, acetylene black, ketjen black, Super P, copper powder, and silver powder.
In a second aspect of the invention, the invention provides a method for preparing the composite lithium-supplementing film. According to an embodiment of the invention, the method for preparing the composite lithium supplementing film comprises the following steps:
(1) applying a buffer layer slurry obtained by mixing at least one of an ion conductor polymer, an ion conductor oxide and an electron conductor material with an organic solvent onto a carrier substrate to form a buffer layer on the carrier substrate;
(2) applying a lithium supplement layer slurry obtained by mixing a lithium supplement material, an ion conductor material and an organic solvent on the buffer layer so as to form a lithium supplement layer on the buffer layer;
(3) and applying a protective layer slurry obtained by mixing at least one of the ion conductor polymer and the ion conductor oxide with an organic solvent onto the lithium supplement layer so as to form a protective layer on the lithium supplement layer, thereby obtaining the composite lithium supplement film.
According to the method for preparing the composite lithium-supplementing film, the buffer layer slurry obtained by mixing at least one of the ion conductor polymer, the ion conductor oxide and the electron conductor material with the organic solvent is applied to the carrier substrate, namely, the buffer layer is formed on the carrier substrate; then applying lithium supplement layer slurry obtained by mixing a lithium supplement material, an ion conductor material and an organic solvent on the buffer layer, namely forming a lithium supplement layer on the buffer layer; and then applying a protective layer slurry obtained by mixing at least one of the ion conductor polymer and the ion conductor oxide with an organic solvent on the lithium supplement layer, namely forming the protective layer on the lithium supplement layer, thereby obtaining the composite lithium supplement film of the buffer layer, the lithium supplement layer and the protective layer. The buffer layer comprises an ion conductive material, so that the lithium insertion speed and the lithium insertion uniformity of lithium ions in the pre-lithiation process of the lithium supplement layer can be reduced, the generation of lithium dendrites after lithium supplement is inhibited, potential safety hazards are reduced, the use efficiency of lithium powder is improved, and the lithium supplement amount and the lithium supplement effect are ensured; the lithium supplement layer is arranged on the surface of the buffer layer and comprises a lithium supplement material and an ionic conductor material, the lithium supplement material of the lithium supplement layer can effectively replace lithium from a positive electrode consumed when an SEI film is formed on a negative electrode, so that the loss of active lithium can be made up in the charging and discharging process, the first coulombic efficiency and the specific capacity of the lithium ion battery are improved, in addition, the defects that the lithium supplement material is high in activity, not easy to disperse, difficult to use and the like can be overcome by adding the ionic conductor material into the lithium supplement layer, and the prepared lithium supplement layer has quick lithium ion conductivity; the protective layer is arranged on the surface of the lithium supplement layer, so that the lithium supplement layer can be prevented from being etched by electrolyte or ambient atmosphere, and the relatively stable state of the composite lithium supplement film is maintained in the production and storage processes. Therefore, the composite lithium supplementing film can improve the safety performance and the pre-lithiation effect of the lithium supplementing pole piece while improving the electrochemical performance of the battery, and obviously improves the energy density and the cycling stability of the lithium ion battery.
In addition, the method for preparing the composite lithium supplement film according to the above embodiment of the present invention may further have the following additional technical features:
in some embodiments of the invention, in step (1) (2) (3), the organic solvent comprises at least one of N-methylpyrrolidone, dimethylacetamide, dimethylformamide, dimethylacetamide, dimethylsulfoxide, N-dimethylacetamide, N-diethylformamide, acetone, and xylene.
In some embodiments of the present invention, in the step (1), the buffer layer slurry has a solid content of 5 to 20 wt% and a viscosity of 1200 to 2500 mPa.s. Therefore, the uniformity of the buffer layer and certain bonding strength between the buffer layer and the lithium supplement layer and the carrier substrate can be ensured.
In some embodiments of the invention, in the step (2), the lithium supplement layer slurry has a solid content of 5 to 20 wt% and a viscosity of 1200 to 2500 mpa.s. Therefore, the uniformity of the lithium supplement layer and certain bonding strength between the lithium supplement layer and the buffer layer and between the lithium supplement layer and the protective layer can be ensured.
In some embodiments of the present invention, in the step (3), the protective layer slurry has a solid content of 5 to 20 wt% and a viscosity of 1200 to 2500 mPa.s. Therefore, the uniformity of the protective layer and certain bonding strength between the protective layer and the lithium supplement layer can be ensured.
In a third aspect of the invention, a negative electrode is presented. According to an embodiment of the invention, the negative electrode comprises a negative electrode material layer and a lithium supplement film, wherein the lithium supplement film is arranged on the surface of the negative electrode material layer, the lithium supplement film is the composite lithium supplement film or the composite lithium supplement film obtained by the method, and a buffer layer of the composite lithium supplement film is in contact with the negative electrode material layer. Therefore, the battery cathode has high first coulombic efficiency, high energy density, high cycle stability and high safety.
In a fourth aspect of the present invention, a lithium battery is provided. According to an embodiment of the present invention, the lithium battery has the negative electrode described above. Therefore, the lithium battery has high first coulombic efficiency, high energy density, high cycle stability and high safety.
In a fifth aspect of the present invention, a vehicle is provided. According to an embodiment of the present invention, the vehicle has the lithium battery described above. Therefore, the vehicle loaded with the lithium battery with high first coulombic efficiency, high energy density, high cycle stability and high safety has excellent cruising ability, long cycle life and high safety.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1 is a schematic structural diagram of a composite lithium replenishment film according to one embodiment of the invention;
FIG. 2 is a schematic flow diagram of a method for preparing a composite lithium replenishment film according to one embodiment of the invention;
fig. 3 is a schematic structural view of an anode according to an embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
In one aspect of the invention, a composite lithium replenishment film is provided. According to an embodiment of the present invention, referring to fig. 1, the composite lithium supplement film includes: buffer layer 100, lithium supplement layer 200, and protective layer 300.
According to the embodiment of the invention, the buffer layer 100 comprises an ion conducting material, specifically, the buffer layer 100 comprises at least one of an ion conducting polymer, an ion conducting oxide and an electronic conducting material, and the buffer layer prevents a lithium supplement layer from being in direct contact with a negative electrode, so that the reaction rate of metal lithium is reduced, the lithium embedding speed and the lithium embedding uniformity of lithium ions in the lithium supplement layer pre-lithiation process are reduced, the generation of lithium dendrites after lithium supplement is inhibited, the potential safety hazard is reduced, the use efficiency of lithium powder is further improved, and the lithium supplement amount and the lithium supplement effect are ensured. Further, the buffer layer 100 includes 30 to 70 parts by weight of an ion conductor polymer, 30 to 70 parts by weight of an ion conductor oxide, and 0.05 to 0.5 part by weight of an electron conductor material. The inventor finds that the buffer layer contains an electronic conductive material and an ionic conductive material, and has an electronic and ionic conduction function, lithium ions can be diffused to the surface of the negative electrode through the buffer layer, so that the risk of residual dead lithium on the surface of the negative electrode is reduced, the utilization rate of metal lithium is improved, the problem of overhigh temperature of a pole piece caused by heat generation in the lithium supplementing process is reduced, and the formation of a good SEI film in the lithium supplementing process is facilitated. The electronic conductive material can reduce the interface impedance of the buffer layer, improve the cycle and rate performance of the battery, lead the conductive agent to generate de-intercalation reaction with lithium ions when the addition amount of the conductive agent is too high, consume active lithium and influence the performance of the battery, and when the conductive agent is not added at all, the impedance of the lithium supplementing layer is larger, the lithium supplementing effect is obviously reduced, and the performance of the battery is influenced. The ion conductor polymer has light weight, good viscoelasticity and excellent machinability, but an ion transmission area in the ion conductor polymer mainly occurs in an amorphous area, the unmodified polymer has high crystallinity at normal temperature, low ion conductivity and poor stability at high temperature; the ionic conductor oxide has high ionic conductivity and good thermal stability, but has poor mechanical properties and is difficult to form independently. The invention uses the compounding of the ion conductor polymer and the ion conductor oxide, and by adding the oxide powder into the polymer matrix, the invention combines the advantages of the two, reduces the orderliness of the polymer material chain segment and the crystallinity thereof, constructs a flexible ordered space network, increases the lithium ion transmission channel, and improves the conductivity and the ion mobility. When the content of the ionic conductor oxide is too high, the forming is difficult, the flexibility of the buffer layer is reduced, and the buffer layer is easy to crack.
It should be noted that the specific types of the ion conductor polymer, the ion conductor oxide and the electron conductor material can be selected by those skilled in the art according to actual needs, for example, the ion conductor polymer includes at least one of polyethylene oxide or its modified product, polyvinylidene fluoride or its modified product, polyacrylate polymer or its modified product, polyacrylonitrile polymer or its modified product, polyether polymer or its modified product, polysiloxane or its modified product, and polyanionic single ion conductor polymer; the ion conductor oxide comprises at least one of perovskite type lithium ion conductor LLTO, LISICON type lithium ion conductor LZGO and garnet type lithium ion conductor LLZO; the electronic conductor material includes at least one of graphite, graphene, carbon nanotubes, carbon fibers, acetylene black, ketjen black, Super P, copper powder, and silver powder.
Further, the thickness of the buffer layer 100 is 1 to 5 micrometers. The inventor finds that if the buffer layer is too thin, the lithium insertion speed and the lithium insertion uniformity of lithium ions in the pre-lithiation process of the lithium supplement layer cannot be effectively reduced, so that the generation of lithium dendrites after lithium supplement cannot be effectively inhibited, and potential safety hazards are increased; and if the buffer layer is too thick, the energy density of the lithium battery may be reduced.
According to an embodiment of the present invention, the lithium supplement layer 200 is disposed on a surface of the buffer layer 100, preferably, the lithium supplement layer 200 is disposed on the entire surface of the buffer layer 100, and the lithium supplement layer 200 includes a lithium supplement material and an ion conductor material. The inventor finds that the lithium supplement material of the lithium supplement layer can effectively replace lithium from a positive electrode consumed when an SEI film is formed on a negative electrode, so that the loss of active lithium can be made up in the charging and discharging process, the first coulombic efficiency and the specific capacity of the lithium ion battery are improved, in addition, the defects of high activity, difficulty in dispersion, difficulty in use and the like of the lithium supplement material can be overcome by adding the ion conductor material into the lithium supplement layer, and the prepared lithium supplement layer has quick lithium ion conductivity.
Specifically, the ion conductor material includes at least one of an ion conductor polymer and an ion conductor oxide. Further, the lithium supplement layer 200 includes 50 to 95 parts by weight of a lithium supplement material, 0.5 to 5 parts by weight of an ion conductor polymer, and 0 to 50 parts by weight of an ion conductor oxide. The inventor finds that the ion conductor polymer has light weight, good viscoelasticity and excellent machinability, but an ion transmission area in the ion conductor polymer mainly occurs in an amorphous area, the unmodified polymer has high crystallinity at normal temperature, low ion conductivity and poor stability at high temperature; the ionic conductor oxide has high ionic conductivity and good thermal stability, but has poor mechanical properties and is difficult to form independently. The invention uses the compounding of the ion conductor polymer and the ion conductor oxide, and by adding the oxide powder into the polymer matrix, the invention combines the advantages of the two, reduces the orderliness of the polymer material chain segment and the crystallinity thereof, constructs a flexible ordered space network, increases the lithium ion transmission channel, and improves the conductivity and the ion mobility. When the content of the ionic conductor oxide is too high, the buffer layer is difficult to form, the flexibility of the buffer layer is reduced, and the buffer layer is easy to crack.
Therefore, the lithium supplement layer formed by the lithium supplement method can make up for the loss of active lithium in the charging and discharging process, improve the first coulombic efficiency and specific capacity of the lithium ion battery, and has good dispersibility. It should be noted that, a person skilled in the art can select a specific type of the lithium supplement material according to actual needs, for example, the lithium supplement material includes at least one of metallic lithium powder, lithium silicon alloy, lithium tin alloy, lithium magnesium alloy, lithium copper alloy, lithium germanium alloy, lithium-containing oxide, lithium-containing sulfide, lithium-containing nitride and lithium-containing fluoride, and preferably metallic lithium powder. Meanwhile, the types of the ion conductor polymer and the ion conductor oxide are the same as those described above, and are not described in detail here.
Further, the thickness of the lithium supplement layer 200 is 1-20 microns. The inventor finds that if the lithium supplement layer is too thin, the loss of active lithium cannot be effectively compensated in the charging and discharging process, so that the first coulomb efficiency and energy density of the lithium ion battery cannot be effectively improved; if the lithium supplement layer is too thick, the migration rate of lithium ions in the lithium supplement composite film is too slow, and lithium is easily supplemented to be excessive to form lithium precipitation, so that potential safety hazards are caused. In addition, the particle size of the lithium supplement material is 0.5-5 microns, the inventor finds that the particle size of the lithium powder can directly influence the dispersion stability of the lithium powder in the slurry and the control of the lithium supplement amount, and if the particle size of the lithium powder is too small, the lithium powder is difficult to uniformly disperse, and the uniformity of lithium supplement is poor; the lithium powder with too large particle size increases the coating thickness, the lithium supplement amount is difficult to control, and the lithium supplement layer is too thick, thus affecting the battery performance.
According to the embodiment of the invention, the protective layer 300 is disposed on the surface of the lithium supplement layer 200, and the protective layer 300 can prevent the lithium supplement layer 200 from being etched by the electrolyte or the ambient atmosphere, thereby maintaining the relatively stable state of the composite lithium supplement film during the production and storage processes. Preferably, the protective layer 300 is provided on the entire surface of the lithium supplement layer 200, and particularly, the protective layer 300 includes at least one of an ion conductor polymer and an ion conductor oxide. Further, the protective layer 300 includes 30 to 70 parts by weight of an ion conductor polymer and 30 to 70 parts by weight of an ion conductor oxide. The inventor finds that the ion conductor polymer has light weight, good viscoelasticity and excellent machinability, but an ion transmission area in the ion conductor polymer mainly occurs in an amorphous area, the unmodified polymer has high crystallinity at normal temperature, low ion conductivity and poor stability at high temperature; the ionic conductor oxide has high ionic conductivity and good thermal stability, but has poor mechanical properties and is difficult to form independently. The invention uses the compounding of the ion conductor polymer and the ion conductor oxide, and by adding the oxide powder into the polymer matrix, the invention combines the advantages of the two, reduces the orderliness of the polymer material chain segment and the crystallinity thereof, constructs a flexible ordered space network, increases the lithium ion transmission channel, and improves the conductivity and the ion mobility. When the content of the ionic conductor oxide is too high, the buffer layer is difficult to form, the flexibility of the buffer layer is reduced, and the buffer layer is easy to crack.
Therefore, the protective layer obtained by adopting the composition can prevent the lithium supplement layer from being etched by electrolyte or environmental atmosphere, and maintains a relatively stable state in the production and storage processes. It should be noted that the types of the ion conductor polymer and the ion conductor oxide are the same as those described above, and are not described herein again.
Further, the thickness of the passivation layer 300 is 1 to 10 μm. The inventor finds that if the protective layer is too thin, the lithium supplement layer cannot be effectively prevented from being etched by electrolyte or ambient atmosphere, and further a relatively stable state cannot be maintained in the production and storage processes; if the protective layer is too thick, the energy density of the lithium battery may be reduced.
Furthermore, the unit surface capacity provided by the lithium supplement layer in the composite lithium supplement film is 30-100% of the unit surface capacity of the corresponding negative electrode.
The inventor finds that the composite lithium supplementing film comprises a buffer layer, a lithium supplementing layer and a protective layer, wherein the buffer layer comprises an ion conductive material, so that the lithium embedding speed and the lithium embedding uniformity of lithium ions in the lithium supplementing layer pre-lithiation process can be reduced, the generation of lithium dendrites after lithium supplementation is inhibited, the potential safety hazard is reduced, the use efficiency of lithium powder is further improved, and the lithium supplementing amount and the lithium supplementing effect are ensured; the lithium supplement layer is arranged on the surface of the buffer layer and comprises a lithium supplement material and an ionic conductor material, the lithium supplement material of the lithium supplement layer can effectively replace lithium from a positive electrode consumed when an SEI film is formed on a negative electrode, so that the loss of active lithium can be made up in the charging and discharging process, the first coulombic efficiency and the specific capacity of the lithium ion battery are improved, in addition, the defects that the lithium supplement material is high in activity, not easy to disperse, difficult to use and the like can be overcome by adding the ionic conductor material into the lithium supplement layer, and the prepared lithium supplement layer has quick lithium ion conductivity; the protective layer is arranged on the surface of the lithium supplement layer, so that the lithium supplement layer can be prevented from being etched by electrolyte or ambient atmosphere, and the relatively stable state of the composite lithium supplement film is maintained in the production and storage processes. Therefore, the composite lithium supplementing film can improve the safety performance and the pre-lithiation effect of the lithium supplementing pole piece while improving the electrochemical performance of the battery, and obviously improves the energy density and the cycling stability of the lithium ion battery.
In a second aspect of the invention, the invention provides a method for preparing the composite lithium-supplementing film. According to an embodiment of the invention, referring to fig. 2, the method comprises:
s100: applying a buffer layer slurry obtained by mixing at least one of an ion conductor polymer, an ion conductor oxide and an electron conductor material with an organic solvent onto a carrier substrate
In the step, at room temperature with relative humidity of below 20%, at least one of 30-70 parts by weight of ion conductor polymer, 30-70 parts by weight of ion conductor oxide and 0.05-0.5 part by weight of electronic conductor material is mixed with an organic solvent, the mixture is subjected to ultrasonic treatment for 5-10 min after being uniformly mixed, the obtained buffer layer slurry is subjected to tape casting film formation (tape casting mode is not limited) on a carrier matrix, and the buffer layer slurry is continuously dried for 2-6 h at 60-100 ℃ so as to form the buffer layer on the carrier matrix, wherein the thickness of the buffer layer is 1-5 microns. It should be noted that the specific type of the organic solvent can be selected by those skilled in the art according to actual needs, and for example, the organic solvent includes at least one of N-methylpyrrolidone, dimethylacetamide, dimethylformamide, dimethylacetamide, dimethylsulfoxide, N-dimethylacetamide, N-diethylformamide, acetone, and xylene, and preferably N-methylpyrrolidone or dimethylformamide. In addition, the specific type of the carrier substrate, for example, the protective film of PET, can be selected by those skilled in the art according to actual needs. Meanwhile, the types of the ion conductor polymer, the ion conductor oxide, and the electron conductor material are the same as those described above, and are not described in detail here.
Further, the solid content of the buffer layer slurry is 5-20 wt%, and the viscosity is 1200-2500 mPa.s. The inventors found that if the buffer layer slurry has too low a solid content or too low a viscosity, it results in low bonding strength of the buffer layer to the support substrate and the lithium supplement layer; if the solid content or viscosity of the buffer layer is too high, the uniformity and consistency of the buffer layer are affected. Therefore, by adopting the buffer layer slurry with the solid content and the viscosity range, the uniformity and the consistency of the buffer layer and certain bonding strength between the buffer layer and the lithium supplement layer and between the buffer layer and the carrier substrate can be ensured, so that the cycling stability and the safety of the battery are improved.
S200: applying lithium-supplementing layer slurry obtained by mixing lithium-supplementing material, ion conductor material and organic solvent on the buffer layer
In the step, under a room temperature environment with a relative humidity of below 20%, 50-95 parts by weight of a lithium supplement material, an ion conductor material comprising at least one of 0.5-5 parts by weight of an ion conductor polymer and 0-50 parts by weight of an ion conductor oxide, and an organic solvent are mixed, the mixture is subjected to ultrasonic treatment for 5-10 min after being uniformly mixed, the obtained lithium supplement layer slurry is subjected to tape casting to form a film on a buffer layer (the tape casting mode is not limited), the drying is continued for 2-6 h at 60-100 ℃ so as to form a lithium supplement layer on the buffer layer, the thickness of the lithium supplement layer is 1-20 micrometers, and the unit area capacity provided by the lithium supplement layer is 30-100% of the unit area capacity of a corresponding negative electrode.
It should be noted that the types of the lithium supplement material, the ion conductor polymer, the ion conductor oxide and the organic solvent are the same as those described above, and are not described herein again. Wherein the particle size of the lithium supplement material is 0.5-5 microns.
Further, the solid content of the lithium supplement layer slurry is 5-20 wt%, and the viscosity is 1200-2500 mPa.s. The inventor finds that if the solid content or viscosity of the lithium supplement layer slurry is too low, the bonding strength of the lithium supplement layer with the buffer layer and the protective layer is low; if the solid content or viscosity of the lithium supplement layer is too high, the uniformity and consistency of the lithium supplement layer are affected. Therefore, the uniformity and consistency of the lithium supplement layer and certain bonding strength between the lithium supplement layer and the buffer layer and between the lithium supplement layer and the protective layer can be ensured, and the cycling stability and the safety of the battery are improved.
S300: applying a protective layer slurry obtained by mixing at least one of an ion conductive polymer and an ion conductive oxide with an organic solvent onto a lithium supplement layer
In the step, at least one of 30-70 parts by weight of ion conductor polymer and 30-70 parts by weight of ion conductor oxide is mixed with an organic solvent in a room temperature environment with the relative humidity of below 20%, the mixture is uniformly mixed and then is subjected to ultrasonic treatment for 5-10 min, the obtained protective layer slurry is subjected to tape casting film formation (the tape casting mode is not limited) on a lithium supplement layer, the drying is continued for 2-6 h at the temperature of 60-100 ℃, so that a protective layer is formed on the lithium supplement layer, the thickness of the protective layer is 1-10 microns, the dried multilayer structure is rolled, the rolling pressure is 0.5-5 MPa, and finally the carrier matrix is removed, so that the composite lithium supplement film can be obtained. It should be noted that the types of the ion conductor polymer, the ion conductor oxide and the organic solvent are the same as those described above, and are not described herein again.
Further, the solid content of the protective layer slurry is 5-20 wt%, and the viscosity is 1200-2500 mPa.s. The inventors found that if the solid content or viscosity of the protective layer slurry is too low, the bonding strength of the protective layer and the lithium supplement layer is low; if the solid content or viscosity of the protective layer is too high, the uniformity and consistency of the protective layer are affected. Therefore, the uniformity and consistency of the protective layer and certain bonding strength between the protective layer and the lithium supplement layer can be ensured, and the cycling stability and safety of the battery are improved.
The inventors found that a buffer layer slurry obtained by mixing at least one of an ion conductor polymer, an ion conductor oxide, and an electron conductor material with an organic solvent is applied on a support substrate, that is, a buffer layer is formed on the support substrate; then applying lithium supplement layer slurry obtained by mixing a lithium supplement material, an ion conductor material and an organic solvent on the buffer layer, namely forming a lithium supplement layer on the buffer layer; and then applying a protective layer slurry obtained by mixing at least one of the ion conductor polymer and the ion conductor oxide with an organic solvent on the lithium supplement layer, namely forming the protective layer on the lithium supplement layer, thereby obtaining the composite lithium supplement film of the buffer layer, the lithium supplement layer and the protective layer. Wherein, the buffer layer has avoided mending lithium layer and negative pole direct contact, has reduced the reaction rate of metal lithium to reduce lithium ion and inlay lithium speed and the lithium homogeneity of lithium in the lithium layer lithiation in advance on mending, restrain the production of lithium dendrite behind the lithium of mending, reduce the potential safety hazard, and then improved the availability factor of lithium powder, guaranteed mend lithium volume and mended lithium effect. The lithium supplement layer is arranged on the surface of the buffer layer and comprises a lithium supplement material and an ion conductor material, lithium of the lithium supplement layer can effectively replace lithium from a positive electrode consumed when an SEI film is formed on a negative electrode, so that the loss of active lithium can be made up in the charging and discharging process, the first coulombic efficiency and the specific capacity of the lithium ion battery are improved, in addition, the defects of high activity, difficult dispersion, difficult use and the like of the lithium supplement material can be overcome by adding a small amount of the ion conductor material in the lithium supplement material, and the prepared lithium supplement layer has quick lithium ion conductivity; the protective layer is arranged on the surface of the lithium supplement layer, so that the lithium supplement layer can be prevented from being etched by electrolyte or ambient atmosphere, and the relatively stable state of the composite lithium supplement film is maintained in the production and storage processes. Therefore, the composite lithium supplementing film can improve the safety performance and the pre-lithiation effect of the lithium supplementing pole piece while improving the electrochemical performance of the battery, and obviously improves the energy density and the cycling stability of the lithium ion battery.
In a third aspect of the invention, a negative electrode is presented. Referring to fig. 3, according to an embodiment of the present invention, the negative electrode includes a negative electrode material layer 500 and a lithium supplement film 400, wherein the lithium supplement film 400 is disposed on a surface of the negative electrode material layer 500, and the lithium supplement film 400 is the above composite lithium supplement film or the composite lithium supplement film obtained by the above method, and the buffer layer 100 of the composite lithium supplement film is in contact with the negative electrode material layer 500. The inventor finds that in the process of dissolving and lithium inserting of the composite lithium supplementing film, the buffer layer can reduce the lithium inserting speed of lithium ions in the process of pre-lithiation of the lithium supplementing layer and keep the lithium inserting uniformity, the protective layer can prevent the lithium supplementing layer from being etched by electrolyte or environmental atmosphere, so that a relatively stable state is maintained in the production and storage processes, and meanwhile, lithium of the lithium supplementing layer can effectively replace lithium from a positive electrode consumed in the process of forming an SEI (solid electrolyte interface) film on a negative electrode, so that the loss of active lithium can be compensated in the charging and discharging processes, the first coulomb efficiency and the specific capacity of the lithium ion battery are improved, in addition, after a lithium source in the lithium supplementing layer in the composite lithium supplementing film is inserted into a negative electrode active material, a polymer composite electrolyte material is reserved in the composite lithium supplementing film, the generation of lithium dendrites after lithium supplementing can be inhibited, the potential safety hazard is reduced, the use efficiency of lithium. Therefore, by arranging the composite lithium supplement film on the negative electrode material layer, the electrochemical performance of the battery is improved, the safety performance and the pre-lithiation effect of the lithium supplement electrode piece are improved, and the energy density and the cycling stability of the lithium ion battery are improved.
Specifically, a negative electrode active material, a conductive agent, a binder, a dispersant and a solvent are stirred and mixed uniformly to form negative electrode slurry; and then uniformly coating the mixed negative electrode slurry on the surface of the copper foil, drying and rolling to obtain a negative electrode plate, namely the negative electrode material layer 500. It should be noted that, a person skilled in the art may select specific types of the negative electrode active material, the conductive agent, the binder, the dispersant and the solvent according to actual needs, for example, at least one of a carbon-based negative electrode, a silicon-based negative electrode, and an oxide-based negative electrode as the negative electrode active material; the conductive agent is carbon black; the binder is styrene butadiene rubber; the dispersant is sodium carboxymethyl cellulose; the solvent is water. In addition, the negative active material, the conductive agent, the binder, the dispersant, the solvent mixing ratio and the like in the process of preparing the negative pole piece are all conventional settings in the field, and the characteristics and advantages described for the composite lithium supplement film and the preparation method thereof are also applicable to the negative pole, and are not described again here. And the composite lithium supplement film formed on the negative electrode material layer 500 may be formed on one or both surfaces of the negative electrode material layer 500, and those skilled in the art may select the composite lithium supplement film according to actual needs.
In a fourth aspect of the present invention, a lithium battery is provided. According to an embodiment of the present invention, the lithium battery has the negative electrode described above. Therefore, the lithium battery has high first coulombic efficiency, high energy density, high cycle stability and high safety. It should be noted that the features and advantages described above for the negative electrode are also applicable to the lithium battery, and are not described in detail here.
In a fifth aspect of the present invention, a vehicle is provided. According to an embodiment of the present invention, the vehicle has the lithium battery described above. Therefore, the vehicle loaded with the lithium battery with high first coulombic efficiency, high energy density and high safety has excellent cruising ability, long cycle life and high safety. It should be noted that the features and advantages described above for the lithium battery are also applicable to the vehicle and will not be described here.
The scheme of the invention will be explained with reference to the examples. It will be appreciated by those skilled in the art that the following examples are illustrative of the invention only and should not be taken as limiting the scope of the invention. The examples, where specific techniques or conditions are not indicated, are to be construed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.
Example 1
Step 1: under the room temperature environment with the relative humidity lower than 20%, dispersing LLZO and Super P in an NMP solvent containing PVDF, sealing and stirring for 30min, carrying out ultrasonic treatment for 5min, carrying out tape casting on the obtained buffer layer slurry (8 parts by weight of LLZO, 0.05 part by weight of Super P, 9 parts by weight of PVDF, 82.95 parts by weight of solvent NMP, 17.05 wt% of solid content of the buffer layer slurry and 2000-2200 mPa. s) to form a film, drying for 2h at 65 ℃, and then forming a buffer layer on the PET protective film, wherein the thickness of the buffer layer is 2 microns;
step 2: uniformly mixing metal lithium powder (with the particle size of 3 microns) and LLZO under a room temperature environment with the relative humidity of lower than 20%, then adding the mixture into an NMP solvent containing PVDF, sealing and stirring for 30min, carrying out ultrasonic treatment for 5min, casting the obtained lithium supplement layer slurry (8 parts by weight of the metal lithium powder in the lithium supplement layer slurry, 4 parts by weight of LLZO, 0.2 part by weight of PVDF, 87.8 parts by weight of the NMP solvent, 12.2 wt% of the solid content of the lithium supplement layer slurry and 2000-2200 mPa.s) on a buffer layer to form a film, drying for 2h at 75 ℃, and then forming a lithium supplement layer on the buffer layer, wherein the thickness of the lithium supplement layer is 8 microns;
and step 3: dispersing LLZO in an NMP solvent containing PVDF under a room temperature environment with the relative humidity lower than 20%, sealing and stirring for 30min, carrying out ultrasonic treatment for 5min, casting the obtained protective layer slurry (8 parts by weight of LLZO, 9 parts by weight of PVDF and 83 parts by weight of NMP in the solvent, wherein the solid content of the protective layer slurry is 17 wt% and the viscosity is 2000-2200 mPa.s) on a lithium supplement layer to form a film, drying for 6h at 85 ℃, so as to form a protective layer on the lithium supplement layer, wherein the thickness of the protective layer is 3 microns, rolling the dried multilayer structure, and applying the pressure of 3MPa to obtain the required composite lithium supplement film.
And 4, step 4: with SiOxThe negative electrode active material is/C, the carbon black is used as a conductive agent, the styrene butadiene rubber is used as a binder, and the carboxymethyl isSodium cellulose is used as a dispersing agent, water is used as a solvent, and the raw materials are stirred and mixed uniformly to form negative electrode slurry; and (3) uniformly coating the mixed negative electrode slurry on the surface of copper foil, drying, rolling to obtain a negative electrode material layer, and finally performing simple pressure separation to compositely press the composite lithium supplement film obtained in the step (3) on the surface of the negative electrode material layer to obtain the pre-lithiated negative electrode piece.
Example 2
Step 1: dispersing LLZO and CNT in an NMP solvent containing PVDF under a room temperature environment with the relative humidity lower than 20%, sealing and stirring for 30min, carrying out ultrasonic treatment for 5min, casting the obtained buffer layer slurry (8 parts by weight of LLZO, 0.02 part by weight of CNT, 5 parts by weight of PVDF, 86.98 parts by weight of solvent NMP, 13.02 wt% of solid content of the buffer layer slurry and 1600-1700 mPa.s of viscosity) on a PET protective film to form a film, drying for 2h at 65 ℃ to form a buffer layer on the PET protective film, wherein the thickness of the buffer layer is 3 microns;
step 2: uniformly mixing lithium metal powder (with the particle size of 3 microns) and LLZO (lithium manganese oxide) at room temperature with the relative humidity of lower than 20%, adding the mixture into an NMP (N-methyl pyrrolidone) solvent containing PVDF (polyvinylidene fluoride), sealing and stirring for 30min, carrying out ultrasonic treatment for 5min, casting the obtained slurry of a lithium supplement layer (6 parts by weight of the lithium metal powder, 5 parts by weight of LLZO, 0.4 part by weight of PVDF, 88.6 parts by weight of NMP (N-methyl pyrrolidone) solvent, 11.4 wt% of solid content of the slurry of the lithium supplement layer and 1600-1700 mPa.s) on a buffer layer to form a film, drying for 2h at 75 ℃, and then forming the lithium supplement layer on the buffer layer, wherein the thickness of the lithium supplement layer is 10 microns;
and step 3: dispersing LLZO in an NMP solvent containing PVDF under a room temperature environment with the relative humidity lower than 20%, sealing and stirring for 30min, carrying out ultrasonic treatment for 5min, casting the obtained protective layer slurry (8 parts by weight of LLZO, 5 parts by weight of PVDF and 87 parts by weight of NMP solvent, the solid content of the protective layer slurry is 13 wt%, and the viscosity is 1600-1700 mPa.s) on a lithium supplement layer to form a film, drying for 6h at 85 ℃, so as to form a protective layer on the lithium supplement layer, wherein the thickness of the protective layer is 5 microns, rolling the dried multilayer structure, and applying the pressure of 5MPa to obtain the required composite lithium supplement film.
And 4, step 4: with SiOxThe preparation method comprises the following steps of (1) taking carbon black as a negative active material, taking styrene butadiene rubber as a conductive agent, taking sodium carboxymethyl cellulose as a dispersing agent and water as a solvent, and uniformly stirring and mixing the raw materials to form negative slurry; and (3) uniformly coating the mixed negative electrode slurry on the surface of copper foil, drying, rolling to obtain a negative electrode material layer, and finally performing simple pressure separation to compositely press the composite lithium supplement film obtained in the step (3) on the surface of the negative electrode material layer to obtain the pre-lithiated negative electrode piece.
Example 3
Step 1: dispersing LLZO and CNT in a DMF solvent containing PEO under a room temperature environment with the relative humidity of lower than 20%, sealing and stirring for 30min, carrying out ultrasonic treatment for 5min, casting the obtained buffer layer slurry (10 parts by weight of LLZO, 0.01 part by weight of CNT, 5 parts by weight of PEO, 84.99 parts by weight of DMF solvent, 15.01 wt% of solid content of the buffer layer slurry and 1600-1700 mPa.s viscosity) on a PET protective film to form a film, and drying at 65 ℃ for 2h to form a buffer layer on the PET protective film, wherein the thickness of the buffer layer is 4 microns;
step 2: uniformly mixing metal lithium powder (with the particle size of 3 microns) and LLZO in a room temperature environment with the relative humidity of lower than 20%, then adding the mixture into a DMF (dimethyl formamide) solvent containing PEO (polyethylene oxide), sealing and stirring for 30min, carrying out ultrasonic treatment for 5min, casting the obtained lithium supplement layer slurry (7.5 parts by weight of the metal lithium powder, 2.5 parts by weight of LLZO, 0.3 part by weight of PEO, 89.7 parts by weight of DMF (solvent), 10.3 wt% of solid content of the lithium supplement layer slurry and 1200-1300 mPa.s) on a buffer layer to form a film, drying for 2h at 75 ℃, so as to form a lithium supplement layer on the buffer layer, wherein the thickness of the lithium supplement layer is 15 microns;
and step 3: dispersing LLZO in a DMF (dimethyl formamide) solvent containing PEO under a room temperature environment with the relative humidity lower than 20%, sealing and stirring for 30min, carrying out ultrasonic treatment for 5min, casting the obtained protective layer slurry (10 parts by weight of LLZO, 5 parts by weight of PEO, 85 parts by weight of DMF (dimethyl formamide) solvent, 15 wt% of solid content of the protective layer slurry and 1600-1700 mPa.s viscosity) on a lithium supplement layer to form a film, drying at 85 ℃ for 6h to form a protective layer on the lithium supplement layer, wherein the thickness of the protective layer is 5 microns, rolling the dried multilayer structure, and applying the pressure of 2MPa to obtain the required composite lithium supplement film.
And 4, step 4: SiOx/C is used as a negative electrode active material, carbon black is used as a conductive agent, styrene butadiene rubber is used as a binder, sodium carboxymethylcellulose is used as a dispersant, water is used as a solvent, and the raw materials are stirred and mixed uniformly to form negative electrode slurry; and (3) uniformly coating the mixed negative electrode slurry on the surface of copper foil, drying, rolling to obtain a negative electrode material layer, and finally performing simple pressure separation to compositely press the composite lithium supplement film obtained in the step (3) on the surface of the negative electrode material layer to obtain the pre-lithiated negative electrode piece.
Example 4
Step 1: dispersing LLTO and CNT in a DMF solvent containing PEO under a room temperature environment with the relative humidity lower than 20%, sealing and stirring for 30min, carrying out ultrasonic treatment for 5min, casting the obtained buffer layer slurry (5 parts by weight of LLTO, 0.01 part by weight of CNT, 3 parts by weight of PEO, 91.99 parts by weight of DMF solvent, 8.01 wt% of the solid content of the buffer layer slurry and 1200-1300 mPa.s of viscosity) on a PET protective film to form a film, drying for 2h at 65 ℃, and then forming a buffer layer on the PET protective film, wherein the thickness of the buffer layer is 2 microns;
step 2: uniformly mixing metal lithium powder (with the particle size of 0.8 micrometer) and LLTO in a room temperature environment with the relative humidity of lower than 20%, then adding the mixture into a DMF (dimethyl formamide) solvent containing PEO (polyethylene oxide), sealing and stirring for 30min, carrying out ultrasonic treatment for 5min, casting the obtained lithium supplement layer slurry (comprising 9 parts by weight of the metal lithium powder, 2 parts by weight of LLTO, 0.5 part by weight of PEO, 88.5 parts by weight of DMF (solvent), 11.5 wt% of solid content of the lithium supplement layer slurry and 1200-1300 mPa.s) on a buffer layer to form a film, drying for 2h at 75 ℃, and then forming a lithium supplement layer on the buffer layer, wherein the thickness of the lithium supplement layer is 5 micrometers;
and step 3: under the room temperature environment with the relative humidity lower than 20%, dispersing LLTO in a DMF solvent containing PEO, sealing and stirring for 30min, carrying out ultrasonic treatment for 5min, casting the obtained protective layer slurry (5 parts by weight of LLTO, 3 parts by weight of PEO, 92 parts by weight of DMF solvent, 8 wt% of solid content of the protective layer slurry and 1200-1300 mPa.s of viscosity) on a lithium supplement layer to form a film, drying at 85 ℃ for 6h to form a protective layer on the lithium supplement layer, wherein the thickness of the protective layer is 2 microns, rolling the dried multilayer structure, and applying the pressure of 2MPa to obtain the required composite lithium supplement film.
And 4, step 4: with SiOxThe preparation method comprises the following steps of (1) taking carbon black as a negative active material, taking styrene butadiene rubber as a conductive agent, taking sodium carboxymethyl cellulose as a dispersing agent and water as a solvent, and uniformly stirring and mixing the raw materials to form negative slurry; and uniformly coating the mixed negative electrode slurry on the surface of copper foil, drying, rolling to obtain a negative electrode material layer, and finally performing simple pressure separation to compositely press the composite lithium supplement film obtained in the step 3 on the surface of the negative electrode material layer to obtain the pre-lithiated negative electrode piece.
Example 5
Step 1: dispersing LZGO and Super P in a DMSO solvent containing PAN under a room temperature environment with the relative humidity lower than 20%, sealing and stirring for 30min, carrying out ultrasonic treatment for 5min, casting the obtained buffer layer slurry (8 parts by weight of LZGO, 0.05 part by weight of Super P, 10 parts by weight of PAN, 81.95 parts by weight of solvent DMSO, 18.05 wt% of the solid content of the buffer layer slurry and 2200-2300 mPa.s of viscosity) on a PET protective film to form a film, drying for 2h at 65 ℃ to form a buffer layer on the PET protective film, wherein the thickness of the buffer layer is 4 microns;
step 2: under the room temperature environment with the relative humidity of lower than 20 percent, Li is addedxMixing Si (particle size of 0.5 micrometer) and LZGO uniformly, adding the mixture into DMSO solvent containing PAN, sealing and stirring for 30min, performing ultrasonic treatment for 5min, and adding the obtained lithium supplement layer slurry (Li in the lithium supplement layer slurry)x5 parts of Si, 5 parts of LZGO, 0.3 part of PAN, 89.7 parts of DMSO as a solvent, 10.3 wt% of solid content of slurry of the lithium supplement layer and 2200-2300 mPa.s of viscosity), casting the slurry on the buffer layer to form a film, drying the film at 75 ℃ for 2 hours to form a lithium supplement layer on the buffer layer, wherein the thickness of the lithium supplement layer is 15 microns;
and step 3: under the room temperature environment with the relative humidity lower than 20%, the LZGO is dispersed in a DMSO (dimethyl sulfoxide) solvent containing PAN (polyacrylonitrile) and sealed and stirred for 30min, ultrasonic treatment is carried out for 5min, the obtained protective layer slurry (8 parts by weight of the LZGO, 10 parts by weight of PAN, 82 parts by weight of DMSO solvent, 18 wt% of solid content of the protective layer slurry and 2200-2300 mPa.s of viscosity) is cast on a lithium supplement layer to form a film, the film is dried at 85 ℃ for 6h so as to form a protective layer on the lithium supplement layer, the thickness of the protective layer is 8 microns, the dried multilayer structure is rolled, and the pressure of 3MPa is applied to obtain the required composite lithium supplement film.
And 4, step 4: with SiOxThe preparation method comprises the following steps of (1) taking carbon black as a negative active material, taking styrene butadiene rubber as a conductive agent, taking sodium carboxymethyl cellulose as a dispersing agent and water as a solvent, and uniformly stirring and mixing the raw materials to form negative slurry; and (3) uniformly coating the mixed negative electrode slurry on the surface of copper foil, drying, rolling to obtain a negative electrode material layer, and finally performing simple pressure separation to compositely press the composite lithium supplement film obtained in the step (3) on the surface of the negative electrode material layer to obtain the pre-lithiated negative electrode piece.
Evaluation:
the first coulombic efficiency, the ionic conductivity and the cycle stability of the negative electrode sheets obtained in examples 1 to 5 were evaluated, and the evaluation results are shown in table 1.
TABLE 1
First time efficiency Ionic conductivity Retention of 50-week cycle capacity
Example 1 86.2％ 5.8×10-4 99.1％
Example 2 85.1％ 3.5×10-4 98.7％
Example 3 83.5％ 2.2×10-4 97.2％
Example 4 86.6％ 8.6×10-4 98.8％
Example 5 83.7％ 1.6×10-4 97.1％
According to the preparation method of the lithium-supplementing composite membrane with the multilayer structure, the buffer layer prevents the lithium-supplementing layer from being in direct contact with the negative electrode, and the reaction rate of metal lithium is reduced, so that the lithium-embedding speed and the lithium-embedding uniformity of lithium ions in the pre-lithiation process of the lithium-supplementing layer are reduced, the generation of lithium dendrites after lithium supplementation is inhibited, the potential safety hazard is reduced, the use efficiency of lithium powder is further improved, and the lithium supplementing amount and the lithium supplementing effect are ensured. The lithium supplement layer is arranged on the surface of the buffer layer, and can effectively replace lithium from a positive electrode consumed when an SEI film is formed on a negative electrode, so that the loss of active lithium can be made up in the charging and discharging process, the first coulombic efficiency and the specific capacity of the lithium ion battery are improved, in addition, the defects of high activity, difficult dispersion, difficult use and the like of the lithium supplement material can be overcome by adding a small amount of ion conductor material in the lithium supplement material, and the prepared lithium supplement layer has quick lithium ion conductivity; the protective layer is arranged on the surface of the lithium supplement layer, so that the lithium supplement layer can be prevented from being etched by electrolyte or ambient atmosphere, and the relatively stable state of the composite lithium supplement film is maintained in the production and storage processes. Therefore, the composite lithium supplementing film can improve the safety performance and the pre-lithiation effect of the lithium supplementing pole piece while improving the electrochemical performance of the battery, and obviously improves the energy density and the cycling stability of the lithium ion battery.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.

Claims (10)

1. A composite lithium replenishment film, comprising:
a buffer layer comprising an ion conducting material;
a lithium supplement layer provided on a surface of the buffer layer, and including a lithium supplement material and an ion conductor material;
and the protective layer is arranged on the surface of the lithium supplement layer.
2. The composite lithium supplementing film according to claim 1, wherein the buffer layer has a thickness of 1 to 5 μm;
optionally, the thickness of the lithium supplement layer is 1-20 microns;
optionally, the particle size of the lithium supplement material is 0.5-5 microns;
optionally, the thickness of the protective layer is 1-10 microns.
3. The composite lithium replenishing film according to claim 1 or 2, wherein the buffer layer comprises at least one of an ion conductor polymer, an ion conductor oxide, and an electron conductor material;
optionally, the buffer layer comprises 30 to 70 parts by weight of the ionic conductor polymer, 30 to 70 parts by weight of the ionic conductor oxide, and 0.05 to 0.5 parts by weight of the electronic conductor material;
optionally, the ionic conductor material comprises at least one of an ionic conductor polymer and an ionic conductor oxide;
optionally, the lithium supplement layer comprises 50 to 95 parts by weight of the lithium supplement material, 0.5 to 5 parts by weight of the ion conductor polymer and 0 to 50 parts by weight of the ion conductor oxide;
optionally, the protective layer comprises at least one of the ion conductor polymer and the ion conductor oxide;
optionally, the protective layer includes 30 to 70 parts by weight of the ion conductor polymer and 30 to 70 parts by weight of the ion conductor oxide.
4. The composite lithium replenishment film of claim 3, wherein the lithium replenishment material comprises at least one of metallic lithium powder, a lithium silicon alloy, a lithium tin alloy, a lithium magnesium alloy, a lithium copper alloy, a lithium germanium alloy, a lithium-containing oxide, a lithium-containing sulfide, a lithium-containing nitride, and a lithium-containing fluoride;
optionally, the ionic conductor polymer comprises at least one of polyethylene oxide or a modified product thereof, polyvinylidene fluoride or a modified product thereof, polyacrylate polymer or a modified product thereof, polyacrylonitrile polymer or a modified product thereof, polyether polymer or a modified product thereof, polysiloxane or a modified product thereof, and polyanion single-ion conductor type polymer;
optionally, the ion conductor oxide comprises at least one of a perovskite-type lithium ion conductor LLTO, a LISICON-type lithium ion conductor LZGO, and a garnet-type lithium ion conductor LLZO;
optionally, the electronic conductor material comprises at least one of graphite, graphene, carbon nanotubes, carbon fibers, acetylene black, ketjen black, Super P, copper powder, and silver powder.
5. A method of making the composite lithium replenishment film of any one of claims 1 to 4, comprising:
(1) applying a buffer layer slurry obtained by mixing at least one of an ion conductor polymer, an ion conductor oxide and an electron conductor material with an organic solvent onto a carrier substrate to form a buffer layer on the carrier substrate;
(2) applying a lithium supplement layer slurry obtained by mixing a lithium supplement material, an ion conductor material and an organic solvent on the buffer layer so as to form a lithium supplement layer on the buffer layer;
(3) and applying a protective layer slurry obtained by mixing at least one of the ion conductor polymer and the ion conductor oxide with an organic solvent onto the lithium supplement layer so as to form a protective layer on the lithium supplement layer, thereby obtaining the composite lithium supplement film.
6. The method of claim 5, wherein in steps (1) (2) (3), the organic solvent comprises at least one of N-methylpyrrolidone, dimethylacetamide, dimethylformamide, dimethylacetamide, dimethylsulfoxide, N-dimethylacetamide, N-diethylformamide, acetone, and xylene;
optionally, in the step (1), the solid content of the buffer layer slurry is 5-20 wt%, and the viscosity is 1200-2500 mPa.s;
optionally, in the step (2), the solid content of the lithium supplement layer slurry is 5-20 wt%, and the viscosity is 1200-2500 mPa.s;
optionally, in the step (3), the solid content of the protective layer slurry is 5-20 wt%, and the viscosity is 1200-2500 mPa.s.
7. An anode, characterized in that the anode comprises an anode material layer and a lithium supplement film, wherein the lithium supplement film is arranged on the surface of the anode material layer, the lithium supplement film is the composite lithium supplement film of any one of claims 1 to 4 or the composite lithium supplement film obtained by the method of claim 5 or 6, and the buffer layer of the composite lithium supplement film is in contact with the anode material layer.
8. The anode according to claim 7, wherein the anode material layer comprises at least one of a carbon-based anode layer, a silicon-based anode layer, and a tin-based anode layer.
9. A lithium battery, characterized in that it comprises the negative electrode of claim 8.
10. A vehicle characterized in that it has the lithium battery of claim 9.
CN202110003678.5A 2021-01-04 2021-01-04 Composite lithium supplementing film and preparation method and application thereof Pending CN112886011A (en)

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CN115332725A (en) * 2022-08-22 2022-11-11 珠海冠宇动力电池有限公司 Diaphragm and battery
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