CN114464765B - Novel positive electrode structure, preparation method thereof and battery - Google Patents

Novel positive electrode structure, preparation method thereof and battery Download PDF

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CN114464765B
CN114464765B CN202011236907.XA CN202011236907A CN114464765B CN 114464765 B CN114464765 B CN 114464765B CN 202011236907 A CN202011236907 A CN 202011236907A CN 114464765 B CN114464765 B CN 114464765B
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positive electrode
active
solid electrolyte
layer
electrode layer
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CN114464765A (en
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许晶晶
张凤蕊
吴晓东
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Suzhou Institute of Nano Tech and Nano Bionics of CAS
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Suzhou Institute of Nano Tech and Nano Bionics of CAS
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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
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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
    • H01M2004/028—Positive electrodes

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
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  • Manufacturing & Machinery (AREA)
  • Inorganic Chemistry (AREA)
  • Secondary Cells (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention discloses a novel positive electrode structure, a preparation method thereof and a battery. The positive electrode structure comprises a current collecting layer, an active positive electrode layer and a solid electrolyte layer, wherein the solid electrolyte layer is composed of continuous polymer solid electrolyte and covers the surface of the active positive electrode layer, the active positive electrode layer comprises positive electrode active material particles, a conductive agent and a binder, and the polymer solid electrolyte is also distributed and filled in pores among the positive electrode active material particles contained in a part of the active positive electrode layer close to the solid electrolyte layer. The invention can realize that the electrode has high electron conductivity while effectively protecting the active material by finely controlling the thickness of each layer, and has the characteristic that electrolyte in the battery cannot be oxidized on the surface of the electrode due to the insulation protection function of solid electrolyte under high voltage, thereby greatly reducing side reaction of the electrolyte at the positive electrode and corrosion of the electrolyte on the electrode active material, and effectively improving the long cycle performance of the battery.

Description

Novel positive electrode structure, preparation method thereof and battery
Technical Field
The invention relates to a novel positive plate, in particular to a novel positive electrode structure and a preparation method thereof, and a battery comprising the novel positive electrode structure, and belongs to the technical field of electrode structures.
Background
Conventional lithium ion batteries are typically composed of a positive electrode, an electrolyte, a separator, and a negative electrode, wherein commercially available positive electrode materials are lithium cobaltate, ternary materials, lithium manganate, lithium nickel manganate, lithium iron phosphate, lithium manganese iron phosphate, and the like. In the charge and discharge process of a lithium battery, particularly under high voltage, electrolyte in the battery is easily oxidized on the surface of an electrode to generate side reaction, and meanwhile, the electrolyte can corrode a positive electrode material to cause dissolution of metal ions, so that the capacity of an active material is attenuated and the long-cycle performance of the battery is deteriorated, and therefore, effective measures are taken to modify the positive electrode material or the positive electrode surface.
In order to protect the positive electrode from the corrosion of the electrolyte and improve the stability of the positive electrode material, the prior art generally adopts a method of surface coating the active material. The surface coating material mainly comprises aluminum oxide, manganese dioxide, lithium titanate, lithium niobate, calcium fluoride, a fast ion conductor, a conductive polymer and the like. Patent publication No. CN110085805A discloses an atomic layer deposition/molecular layer deposition technology for coating a lithium ion battery anode material to form a protective layer, so as to prevent polymer-based electrolyte in a solid lithium ion battery containing the anode material from being decomposed, and further improve the cycle performance of the solid lithium ion battery under high charging voltage. The patent application with publication number CN109449384A discloses a nickel cobalt lithium manganate positive electrode material coated by a nano carbon-containing composite conductive polymer and a preparation method thereof, wherein a layer of high-molecular conductive polymer is coated on the surface of the nickel cobalt lithium manganate to improve the conductivity of an electrode material, but the coating layer has poor lithium ion conductivity, influences the deintercalation of lithium ions and reduces the battery performance. The patent application with publication number CN107706390A discloses a method for double-modifying positive electrode materials by using a fast ion conductor and a conductive polymer, wherein the fast ion conductor is coated by a first layer, and the conductive polymer is coated by a second layer. Publication No. CN110148709A adopts conductive material and cross-linked high voltage resistant system polymer electrolyte to form a layer of coating layer for conducting lithium and conducting electrons on the surface of the positive electrode, so that the performance of the lithium ion battery is effectively improved. Therefore, after the active material with the surface coated is prepared into a pole piece, the side reaction of the positive electrode and electrolyte is relieved, but the problem of poor electron or ion transmission performance exists, and the performance of the battery is affected.
Disclosure of Invention
The invention mainly aims to provide a novel positive electrode structure and a preparation method thereof, so as to overcome the defects in the prior art.
It is still another object of the present invention to provide a battery comprising the novel positive electrode structure.
In order to achieve the purpose of the invention, the technical scheme adopted by the invention comprises the following steps:
The embodiment of the invention provides a novel positive electrode structure, which sequentially comprises the following components: the active positive electrode comprises a current collecting layer, an active positive electrode layer and a solid electrolyte layer, wherein the solid electrolyte layer is composed of continuous polymer solid electrolyte and covers the surface of the active positive electrode layer, the active positive electrode layer comprises positive electrode active material particles, a conductive agent and a binder, and the polymer solid electrolyte is also distributed and filled in pores among the positive electrode active material particles contained in a part of the active positive electrode layer close to the solid electrolyte layer.
In some embodiments, the novel positive electrode structure comprises, in order: the active coating positive electrode comprises a current collecting layer, an active uncoated positive electrode layer, an active coated positive electrode layer and a solid electrolyte layer, wherein the solid electrolyte layer covers the surface of the active coated positive electrode layer, the active uncoated positive electrode layer and the active coated positive electrode layer jointly form the active positive electrode layer, the active coated positive electrode layer further comprises polymer solid electrolyte, the polymer solid electrolyte is coated on the surface of positive electrode active material particles, and the polymer solid electrolyte is distributed and filled in pores among the positive electrode active material particles.
The embodiment of the invention also provides a preparation method of the novel positive electrode structure, which comprises the following steps:
Providing a uniformly mixed reaction system comprising positive electrode active material particles, a conductive agent, a binder and a dispersing agent;
applying the uniform mixed reaction system on a current collecting layer to obtain an active positive electrode layer/current collecting layer composite structure;
Providing a polymer solid electrolyte solution, enabling the active positive electrode layer/current collecting layer composite structure to be in full contact with the polymer solid electrolyte solution, so that the polymer solid electrolyte solution is dispersed on the surface of the active positive electrode layer and is partially dispersed into pores among positive electrode active material particles contained in the active positive electrode layer, and removing a solvent to form a solid electrolyte layer, thereby obtaining the novel positive electrode structure;
Or providing a polymer solid electrolyte precursor solution, enabling the active positive electrode layer/current collecting layer composite structure to be fully contacted with the polymer solid electrolyte precursor solution, so that active monomers in the polymer solid electrolyte precursor solution are formed on the surface of the active positive electrode layer and are partially diffused into pores among positive electrode active material particles contained in the active positive electrode layer, and then carrying out in-situ polymerization reaction under heating treatment or illumination treatment to form the solid electrolyte layer and the active cladding positive electrode layer, thereby obtaining the novel positive electrode structure.
The embodiment of the invention also provides a battery, which comprises a positive electrode, a negative electrode and electrolyte, wherein the positive electrode adopts the novel positive electrode structure.
Further, the electrolyte also comprises a film forming additive, wherein the film forming additive comprises any one or more than two of 1, 3-Propane Sultone (PS), fluoroethylene carbonate (FEC), ethylene carbonate (VC), lithium difluorophosphate (LiPF 2O2), lithium difluorooxalato borate (LiDFOB) and the like.
Further, the content of the film forming additive in the electrolyte is 0.1-5 wt%.
Compared with the prior art, the invention has the beneficial effects that:
1) The novel positive electrode structure provided by the invention comprises a current collecting layer, an active uncoated positive electrode layer, an active coated positive electrode layer and a continuous solid electrolyte thin layer, wherein the mass of polymer solid electrolyte gradually decreases from the surface to the current collecting layer, positive electrode active material particles in the active coated positive electrode layer are coated by the polymer solid electrolyte, and the corrosion and side reaction of electrolyte to the positive electrode material can be effectively inhibited; the lower layer close to the current collecting layer is an active uncoated positive electrode layer with uncoated positive electrode active material particles, and the positive electrode active material particles in the active uncoated positive electrode layer are fully contacted with a conductive additive and a binder to provide a good electron and ion transmission channel;
2) The novel positive electrode structure provided by the invention realizes that the pole piece has high electron conduction capability while effectively protecting the active material by finely controlling the thickness of each layer;
3) The invention also uses a functional electrolyte containing a film-forming additive, and the additive is degraded in the charge and discharge process along with the electrolyte penetrating into the electrode, so that a layer of surface film is generated on the surface of the inner active material particles to further protect the positive electrode active material;
4) The novel positive electrode structure provided by the invention has the characteristic that under high voltage, electrolyte in a battery cannot be oxidized on the surface of an electrode due to the insulation protection effect of the solid electrolyte, so that side reaction of the electrolyte on the positive electrode and corrosion of the electrolyte on electrode active materials are greatly reduced, and the long-cycle performance of the battery is effectively improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments described in the present invention, and other drawings may be obtained according to the drawings without inventive effort to those skilled in the art.
Fig. 1 is a schematic view showing the internal structure of a novel positive electrode structure according to an exemplary embodiment of the present invention.
Detailed Description
In view of the defects in the prior art, the inventor of the present invention has long-term studied and a great deal of practice to provide a technical scheme of the present invention, which mainly provides a novel positive electrode structure, comprising four layers of a current collecting layer, an active uncoated positive electrode layer, an active coated positive electrode layer and a solid electrolyte layer. The technical scheme, the implementation process, the principle and the like are further explained as follows.
The novel positive electrode structure provided by one aspect of the embodiment of the invention sequentially comprises a current collecting layer, an active positive electrode layer and a solid electrolyte layer, wherein the solid electrolyte layer is composed of continuous polymer solid electrolyte and covers the surface of the active positive electrode layer, the active positive electrode layer comprises positive electrode active material particles, a conductive agent and a binder, and the polymer solid electrolyte is also distributed and filled in pores among the positive electrode active material particles contained in a part of the active positive electrode layer close to the solid electrolyte layer.
In some preferred embodiments, the novel positive electrode structure comprises, in order: the active coating positive electrode comprises a current collecting layer, an active uncoated positive electrode layer, an active coated positive electrode layer and a solid electrolyte layer, wherein the solid electrolyte layer covers the surface of the active coated positive electrode layer, the active uncoated positive electrode layer and the active coated positive electrode layer jointly form the active positive electrode layer, the active coated positive electrode layer further comprises polymer solid electrolyte, the polymer solid electrolyte is coated on the surface of positive electrode active material particles, and the polymer solid electrolyte is distributed and filled in pores among the positive electrode active material particles.
In some preferred embodiments, the novel positive electrode structure has a gradually decreasing polymer solid electrolyte content in the direction from the solid electrolyte layer to the current collector layer.
In some preferred embodiments, the solid electrolyte layer is a layered structure containing a polymer electrolyte and has a thickness of 10nm to 10 μm.
Further, the novel positive electrode structure comprises polymer solid electrolyte with a certain concentration gradient from a polymer solid electrolyte thin layer on the surface to a current collecting layer, wherein the surface layer is a continuous polymer solid electrolyte thin layer, and the thickness is 10 nm-5 mu m.
Further, the thickness of the solid electrolyte layer is 50nm to 5 μm.
In some preferred embodiments, the polymer solid electrolyte includes any one or a combination of two or more of a mixture of a polymer and a lithium salt, a mixture of a polyionic liquid and a lithium salt, a mixture of a polymer and an inorganic solid electrolyte, and the like, but is not limited thereto.
Further, the polymer includes a polymer that is insoluble and swellable in a commercial electrolyte, such as, but not limited to, a polyionic liquid poly (dienedimethyl ammonium) bistrifluorosulfonimide salt.
Further, the lithium salt includes any one or a combination of two or more of LiPF 6、LiBF4、LiClO4, liBOB, liFSI, liTFSI, etc., but is not limited thereto.
More specifically, the solid electrolyte of the solid electrolyte layer may be a conventional polymer mixed with lithium salt, such as PEO mixed with LiPF 6, or a polyionic liquid mixed with LiTFSI, or a polymer having other lithium ion conductive properties, or a mixture of a polymer and an inorganic solid electrolyte powder.
Further, the polyionic liquid includes poly (dienedimethyl ammonium) bistrifluorosulfonimide salt, but is not limited thereto. In some preferred embodiments, the polymer solid electrolyte may also be formed by in situ copolymerization of an ionic liquid monomer containing a cation or an anion with a polymer monomer, a lithium salt.
Further, the ionic liquid monomer is any one or a combination of more than two of imidazole ionic liquid, pyrrole ionic liquid, pyridine ionic liquid, piperidine ionic liquid and the like, but is not limited to the above.
Further, the polymer monomer contains any one or a combination of two or more of vinyl, allyl, epoxypropyl, amino, hydroxyl, and the like, but is not limited thereto.
In some preferred embodiments, the solid electrolyte layer, in addition to the layer itself, fills in part the interstices between the particles of the positive electrode active material that enter the active positive electrode layer, and the solid electrolyte that enters the active positive electrode layer will exceed 0.1wt% of the total weight of the active positive electrode layer, i.e., the polymer solid electrolyte content in the active positive electrode layer is above 0.1 wt%.
Further, the content of the polymer solid electrolyte in the active positive electrode layer is preferably 0.1 to 20wt%, that is, the mass of the polymer solid electrolyte in the active coated positive electrode layer exceeds 0.1 to 20% of the total weight of the active positive electrode layer.
Further, the polymer solid electrolyte in the active positive electrode layer is uniformly dispersed therein, and the weight content of the polymer solid electrolyte is 0.2wt% to 20wt%.
Further, the mass of the polymer solid electrolyte in the active positive electrode layer will exceed 0.5% by weight, preferably 0.5 to 20% by weight, of the total mass of the active positive electrode layer.
In some preferred embodiments, the active coated positive electrode layer has a polymer solid electrolyte content of 1 to 10wt%.
In some preferred embodiments, the active positive electrode layer contains positive electrode active material particles which are various positive electrode materials useful in lithium ion batteries, the active positive electrode layer (including active uncoated positive electrode layer and active coated positive electrode layer) has a thickness of 200 to 500 μm, the positive electrode active material particles in the active positive electrode layer have a weight content of 50 to 99wt%, and the optimized active coated positive electrode layer has a weight content of 1 to 10% of the polymer solid electrolyte.
In some preferred embodiments, the solid electrolyte layer, in addition to itself, will partially fill the interstices between the particles of positive electrode active material of the active positive electrode layer, and the depth of the polymer solid electrolyte into the active positive electrode layer will be greater than 5% or more of the total thickness of the active positive electrode layer, i.e., the thickness ratio of the active coated positive electrode layer to the active positive electrode layer is 5:100 or more.
Further, the depth of the polymer solid electrolyte into the active positive electrode layer will be greater than 20% of the active positive electrode layer thickness.
Further, the thickness ratio of the active coating positive electrode layer to the active positive electrode layer is 5-50:100, that is, the thickness of the active coating positive electrode layer is 5% -50% of the total thickness of the active positive electrode layer.
In some preferred embodiments, the ratio of the thickness of the active uncoated positive electrode layer to the active positive electrode layer is 50-95:100, i.e., the thickness of the active uncoated positive electrode layer is 50-95% of the total thickness of the active positive electrode layer.
Further, the thickness ratio of the active uncoated positive electrode layer to the active positive electrode layer is 50-80:100, that is, the thickness of the active uncoated positive electrode layer is 50-80% of the total thickness of the active positive electrode layer.
In some preferred embodiments, the active uncoated positive electrode layer includes positive electrode active material particles, a conductive agent, and a binder, and the positive electrode active material particles are in sufficient contact with the conductive additive, the binder.
Further, the positive electrode active material particles include any one or a combination of two or more of lithium cobaltate, lithium manganate, lithium nickel manganate, ternary positive electrode materials (such as NCM 523), lithium iron phosphate, lithium manganese iron phosphate, and the like, but are not limited thereto.
Further, the conductive agent includes any one or a combination of two or more of acetylene black, SUPER-P, KS-6, carbon nanotubes, graphene, carbon fiber VGCF, etc., but is not limited thereto.
Further, the content of the conductive agent in the active positive electrode layer is 0.5 to 10wt%.
Further, the binder includes any one or a combination of two or more of polyvinylidene fluoride (PVDF), polyacrylic acid, styrene-butadiene rubber, polyamide, polyvinyl alcohol, polyethylenimine, polyimide, and the like, but is not limited thereto.
Further, the content of the binder in the active positive electrode layer is 0.5 to 10wt%.
In some preferred embodiments, the current collector of the present invention may be a sheet or mesh of conductive materials such as aluminum, nickel, carbon fibers, etc. for collecting current, and the typical active positive electrode layer contains a positive electrode active material including lithium cobaltate, lithium manganate, lithium nickel manganate, ternary positive electrode, lithium iron phosphate, lithium iron manganese phosphate, etc., and the typical solid electrolyte layer is a thin layer of continuous polymer solid electrolyte covering the active positive electrode layer.
Further, the thickness of the collector layer is 5 to 30 μm.
In some preferred embodiments, the surface of the positive electrode active material particle is further provided with a protective film formed of a film-forming additive including any one or a combination of two or more of PS, FEC, VC, liPF 2O2 and LiDFOB, etc., but not limited thereto.
Further, the present invention uses a functional electrolyte containing 0.1-5% of a film-forming additive which is degraded during charge and discharge as the electrolyte permeates into the electrode, thereby generating a surface film on the surface of the inner active material particles to further protect the positive electrode active material.
Referring to fig. 1, an internal structure of a novel positive electrode structure according to an exemplary embodiment of the invention is shown, and the novel positive electrode structure of the invention comprises four layers, namely a current collecting layer, an active uncoated positive electrode layer, an active coated positive electrode layer and a solid electrolyte layer. The electrode contains polymer solid electrolyte with a certain concentration gradient from a surface solid electrolyte layer to a current collecting layer, wherein the surface layer is a continuous polymer solid electrolyte thin layer, and the thickness is 10nm-5 mu m; the middle is an active coating positive electrode layer, positive electrode active material particles in the active coating positive electrode layer are coated by polymer solid electrolyte, so that corrosion and side reaction of electrolyte to the positive electrode material can be effectively inhibited, wherein the mass of the polymer solid electrolyte in the active coating positive electrode layer exceeds 0.1-20% of the total weight of the active positive electrode layer, and the thickness of the active coating positive electrode layer is 5-50% of the total thickness of the active positive electrode layer; the lower layer close to the current collecting layer is an active uncoated positive electrode layer with uncoated positive electrode active material particles, the positive electrode active material particles in the layer are fully contacted with a conductive additive and a binder, a good electron and ion transmission channel is provided, and the thickness of the layer is 50% -95% of the total thickness of the active positive electrode layer. The invention realizes that the pole piece has high electron conduction capability while effectively protecting the active material by finely controlling the thickness of each layer. In addition, the invention also uses a functional electrolyte containing 0.1-5% of film forming additive, the additive is degraded in the charge and discharge process along with the electrolyte penetrating into the electrode, thereby generating a surface film on the surface of the inner active material particles to further protect the positive electrode active material.
In summary, the novel positive electrode structure shown in fig. 1 provided by the invention has the characteristic that under high voltage, electrolyte in a battery cannot be oxidized on the surface of an electrode due to the insulation protection effect of solid electrolyte, so that side reaction of the electrolyte at the positive electrode and corrosion of the electrolyte on electrode active materials are greatly reduced, and the long cycle performance of the battery is effectively improved.
Another aspect of an embodiment of the present invention provides a method for preparing the aforementioned novel positive electrode structure, comprising:
Providing a uniformly mixed reaction system comprising positive electrode active material particles, a conductive agent, a binder and a dispersing agent;
applying the uniform mixed reaction system on a current collecting layer to obtain an active positive electrode layer/current collecting layer composite structure;
Providing a polymer solid electrolyte solution, enabling the active positive electrode layer/current collecting layer composite structure to be in full contact with the polymer solid electrolyte solution, so that the polymer solid electrolyte solution is dispersed on the surface of the active positive electrode layer and is partially dispersed into pores among positive electrode active material particles contained in the active positive electrode layer, and then heating to remove a solvent to form a solid electrolyte layer, thereby obtaining the novel positive electrode structure;
Or providing a polymer solid electrolyte precursor solution, enabling the active positive electrode layer/current collecting layer composite structure to be fully contacted with the polymer solid electrolyte precursor solution, so that active monomers in the polymer solid electrolyte precursor solution are formed on the surface of the active positive electrode layer and are partially diffused into pores among positive electrode active material particles contained in the active positive electrode layer, and then carrying out in-situ polymerization reaction under heating treatment or illumination treatment to form the solid electrolyte layer and the active cladding positive electrode layer, thereby obtaining the novel positive electrode structure.
In some preferred embodiments, the heat treatment is at a temperature of 50 to 80 ℃ for a time of 0.5 to 10 hours.
Further, the time of the light treatment is 1-60 min.
In some preferred embodiments, the mass ratio of the positive electrode active material particles, the conductive agent, and the binder is 70-99:0.5-15:0.5-15.
Further, the dispersant may include any one or a combination of two or more of N-methylpyrrolidone (NMP), water, N-dimethylformamide, etc., and particularly preferably, N-methylpyrrolidone, but is not limited thereto.
In some preferred embodiments, the polymer solid electrolyte solution includes a mixture of a solvent and any one or more of a mixture of an ionic liquid monomer, a polymer monomer, a lithium salt and an initiator, a mixture of an ionic liquid and a lithium salt, a mixture of a polymer and an inorganic solid electrolyte, but is not limited thereto.
In some preferred embodiments, the polymer solid electrolyte precursor solution includes a mixture of an ionic liquid monomer and an initiator, a mixture of a polymer monomer and a lithium salt, a mixture of an ionic liquid monomer and a lithium salt, a mixture of a polymer monomer and an inorganic solid electrolyte, or a combination of two or more thereof, and a mixture of a solvent, but is not limited thereto.
In some preferred embodiments, the initiator includes, but is not limited to, a photoinitiator, a thermal initiator, and the like.
Further, the thermal initiator includes any one or a combination of two or more of azobisisobutyronitrile, azobisisoheptonitrile, dibenzoyl peroxide, dialkyl peroxide, potassium persulfate, cumene hydroperoxide, tert-butyl hydroperoxide, etc., but is not limited thereto.
Further, the photoinitiator includes any one or a combination of two or more of 2-hydroxy-methylphenyl propane-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- (4-methylthiophenyl) -2-morpholino-1-propanone, bis (2, 4, 6-trimethylbenzoyl) phenylphosphine oxide, and the like, but is not limited thereto.
In some preferred embodiments, the ionic liquid monomer content in the polymer solid electrolyte precursor solution is 50 to 95wt%, the polymer monomer content is 0 to 40wt%, and the lithium salt content is 5 to 40wt%.
Further, the mass ratio of the initiator to the combination of the ionic liquid monomer and the polymer monomer is 0.5-5:100.
Further, the solvent includes any one or a combination of two or more of acetonitrile, acetone, tetrahydrofuran, dimethyl sulfoxide, N-methylpyrrolidone (NMP), N-dimethylformamide, etc., preferably acetonitrile, but is not limited thereto.
In some more preferred embodiments, the current collecting layer and the active positive electrode layer can be coated on the prepared electrode sheet by a secondary coating method by adopting a traditional transfer coating or extrusion coating and drying mode of the positive electrode of the lithium battery, or adopting a 'slurry pulling' and drying mode.
In some more preferred embodiments, the solid electrolyte layer is prepared by immersing the prepared pole piece containing the current collecting layer and the active positive electrode layer into a solution containing the solid electrolyte, allowing the solid electrolyte to adhere to the surface of the active positive electrode layer, and after part of the solid electrolyte penetrates into the gaps of the active positive electrode layer, heating to completely volatilize the solvent so as to finally realize the surface coverage of the solid electrolyte on the surfaces of the positive electrode and the active particles inside the electrode.
In some more preferred embodiments, the solid electrolyte layer is formed by immersing the finished pole piece containing the current collecting layer and the active positive electrode layer into a solution containing solid electrolyte monomers, allowing the solid electrolyte monomers to adhere to the surface of the active positive electrode layer, and partially penetrating into the gaps of the active positive electrode layer, and finally realizing the mode that the solid electrolyte covers the surface of the active material particles through photoinitiated or thermally initiated polymerization, wherein the thickness of the solid electrolyte layer forming the surface is controlled by the amount of the monomers adhered to the surface of the active positive electrode layer.
In some more preferred embodiments, the solid electrolyte in the active positive electrode layer may also be oxidized by adding film forming additives such as PS, FEC, VC, liPF 2O2 and LiDFOB to the organic solution electrolyte, which may lose electrons in situ in the positive electrode and form an insoluble filling into the active positive electrode layer, thereby forming the final active positive electrode layer structure with dual solid electrolyte protection.
Accordingly, another aspect of an embodiment of the present invention also provides a battery, including a positive electrode, a negative electrode, and an electrolyte, where the positive electrode adopts any one of the foregoing novel positive electrode structures.
In some embodiments, a film-forming additive is further included in the electrolyte, and the film-forming additive includes any one or a combination of two or more of 1, 3-Propane Sultone (PS), fluoroethylene carbonate (FEC), vinylene Carbonate (VC), lithium difluorophosphate (LiPF 2O2), lithium difluorooxalato borate (lipdfob), and the like, but is not limited thereto. The additive is degraded in the charge-discharge process along with the penetration of electrolyte into the electrode, so that a layer of surface film is generated on the surface of the internal active material particles to further protect the positive electrode active material.
Further, the content of the film forming additive in the electrolyte is 0.1-5 wt%.
In some more preferred embodiments, a battery using the novel positive electrode structure is provided, wherein the separator is a conventional commercial lithium ion battery separator or a solid electrolyte coating, the negative electrode is a negative electrode plate for a commercial lithium ion battery, and the electrolyte is commercial lithium ion battery electrolyte to form the battery. Further, positive film forming additives such as PS, FEC, VC, liPF 2O2 and LiDFOB which can lose electrons in situ at the positive electrode and be oxidized to form insoluble substances are added into the electrolyte, and further the total content of the positive film forming additives is not less than 0.2% by weight of the electrolyte in the battery, and optimally not less than 1%.
In summary, the novel positive electrode structure provided by the invention has the characteristic that under high voltage, electrolyte in a battery cannot be oxidized on the surface of an electrode due to the insulation protection effect of the solid electrolyte, so that side reaction of the electrolyte on the positive electrode and corrosion of the electrolyte on electrode active materials are greatly reduced, and the long cycle performance of the battery is effectively improved.
The technical solution of the present invention will be described in further detail below with reference to a number of preferred embodiments and accompanying drawings, and it is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention. The experimental methods, in which specific conditions are not noted in the following examples, are generally conducted under conventional conditions or under conditions recommended by the manufacturer.
Example 1
Preparation of a positive plate:
The positive electrode material Lithium Cobalt Oxide (LCO), the binder PVDF and the conductive agent acetylene black are dissolved in NMP solvent according to the mass ratio of 99:0.5:0.5, and magnetically stirred for 12 hours, so as to obtain the evenly mixed slurry. Then the slurry is coated on the surface of aluminum foil by scraping, and vacuum drying is carried out for 12 hours at 85 ℃ to remove NMP solvent, thus obtaining a pole piece with the thickness of the positive electrode active layer of 200 mu m, and the pole piece is filled into a small disc with the diameter of 15 mm. And (3) dissolving the polyion liquid-polydimethyl diallyl ammonium bis (trifluoromethyl sulfonyl) imide and lithium salt-LiTFSI in acetonitrile solution according to the mass ratio of 3:1, dripping 20 mu L of solid electrolyte-containing solution on the surface of the pole piece by using a pipette, and vacuum drying at 80 ℃ for 10 hours to remove the acetonitrile solution, thereby obtaining the positive pole piece with the solid electrolyte coated on the surface. The mass of the solid electrolyte is 0.1% of the total mass of the active positive electrode layer after weighing and coating the mass of the front and rear electrode plates. The thickness of the coated positive electrode layer is 100 mu m, which accounts for 50% of the active positive electrode layer, and the thickness of the continuous solid electrolyte thin layer on the surface of the pole piece is 10nm.
Assembling and testing of the battery: button cells were assembled using the above-described coated electrode sheets, lithium sheets with a diameter of 16mm were used as the negative electrode, PP with a thickness of 40 μm as the separator, and 1M LiPF 6/EC/DMC/EMC (1:1:1 vol%) and 0.1% fec as the electrolyte. And testing the assembled battery on a Xinwei battery charge-discharge instrument, wherein the testing temperature is 25 ℃, and the testing potential window is 2.7-4.5V.
Experimental results: LCO materials show good cycling stability at high voltages with a 200 cycle capacity retention of 85%. Electrolyte analysis showed lower dissolution of Co 2+ metal ions.
Example 2
Preparation of a positive plate:
The cathode material, namely Lithium Manganate (LMO), the binder, namely PVDF and the conductive agent, namely acetylene black are mixed according to the mass ratio of 80:10:10 are dissolved in NMP solvent and stirred magnetically for 12h to obtain evenly mixed slurry. Then the slurry is coated on the surface of aluminum foil by scraping, and vacuum drying is carried out for 12 hours at 85 ℃ to remove NMP solvent, thus obtaining a pole piece with the thickness of the positive electrode active layer of 500 mu m, and the pole piece is filled into a small disc with the diameter of 15 mm. Dissolving vinyl-containing ionic liquid monomer-1-vinyl-3-butylimidazole bistrifluoromethane sulfonyl imide salt and lithium salt-LiPF 6 in acetone solution according to the mass ratio of 3:1, adding a thermal initiator azodiisobutyronitrile accounting for 1% of the total mass of the monomers, dripping 100 mu L of solid electrolyte-containing solution on the surface of a pole piece by using a liquid-transferring gun, polymerizing the ionic liquid monomer at 50 ℃ for 10 hours, and then drying at 50 ℃ for 10 hours in vacuum to remove the acetone solution, thereby forming high molecular weight polyionic liquid and obtaining the positive pole piece with the solid electrolyte coated on the surface. The mass of the solid electrolyte is 20% of the total mass of the active positive electrode layer after the mass of the pole pieces before and after coating is weighed. The thickness of the coated positive electrode layer is 25 mu m, which accounts for 5% of the positive electrode active layer, and the thickness of the continuous solid electrolyte thin layer on the surface of the pole piece is 5 mu m.
Assembling and testing of the battery: the button cell was assembled using the above-mentioned coated electrode sheet, the negative electrode was a lithium sheet having a diameter of 16mm, the separator was a 40 μm thick PP, and the electrolyte was 1M LiPF 6/EC/DMC/EMC (1:1:1 vol%) and 2% fec. And testing the assembled battery on a Xinwei battery charge-discharge instrument, wherein the test temperature is 55 ℃, and the test potential window is 3.0-4.2V.
Experimental results: LMO materials exhibit good cycling stability at high voltages with a 200 cycle capacity retention of 92%. The electrolyte analysis results showed lower dissolution of Mn 2+ ions.
Example 3
Preparation of a positive plate:
the positive electrode material, namely lithium iron phosphate (LFP), the binder, namely PVDF and the conductive agent, namely acetylene black are dissolved in an NMP solvent according to the mass ratio of 90:5:5, and are magnetically stirred for 12 hours, so that the evenly mixed slurry is obtained. Then the slurry is coated on the surface of aluminum foil by scraping, and vacuum drying is carried out for 12 hours at 85 ℃ to remove NMP solvent, thus obtaining a pole piece with the thickness of the positive electrode active layer of 300 mu m, and the pole piece is filled into a small disc with the diameter of 15 mm. Dissolving vinyl-containing ionic liquid monomer-1-vinyl-3-butylimidazole bistrifluoromethane sulfonyl imide salt, polyethylene glycol diacrylate monomer and lithium salt-LiFeSI in a tetrahydrofuran solution according to the mass ratio of 2:1:2, adding a thermal initiator-dibenzoyl peroxide which is 0.5% of the total mass of the ionic liquid monomer and the polyethylene glycol diacrylate monomer, taking 30 mu L of solid electrolyte-containing solution by using a pipette, dripping the solution on the surface of a pole piece, polymerizing the monomer at 80 ℃ for 0.5h, and then drying the monomer at 80 ℃ in vacuum for 5h to remove the tetrahydrofuran solution, thereby obtaining the positive pole piece with the solid electrolyte coated on the surface. The mass of the solid electrolyte is 2% of the total mass of the active positive electrode layer after weighing and coating the mass of the front and rear electrode plates. The thickness of the coated positive electrode layer is 90 mu m, accounting for 30% of the active positive electrode layer, and the thickness of the continuous solid electrolyte thin layer on the surface of the pole piece is 2 mu m.
Assembling and testing of the battery: the button cell was assembled using the above-mentioned coated electrode sheet, the negative electrode was a lithium sheet having a diameter of 16mm, the separator was a 40 μm thick PP, and the electrolyte was 1M LiPF 6/EC/DMC/EMC (1:1:1 vol%) and 5% FEC. And testing the assembled battery on a Xinwei battery charge-discharge instrument, wherein the testing temperature is 25 ℃, and the testing potential window is 2.7-4.0V.
Experimental results: LFP materials showed good cycling stability with a 200 cycle capacity retention of 98%.
Example 4
Preparation of a positive plate:
The positive electrode material, namely lithium iron phosphate (LFP), the binder, namely PVDF and the conductive agent, namely acetylene black are dissolved in NMP solvent according to the mass ratio of 70:15:15, and are magnetically stirred for 12 hours, so that the evenly mixed slurry is obtained. Then the slurry is coated on the surface of aluminum foil by scraping, and vacuum drying is carried out for 12 hours at 85 ℃ to remove NMP solvent, thus obtaining a pole piece with the thickness of the positive electrode active layer of 300 mu m, and the pole piece is filled into a small disc with the diameter of 15 mm. Dissolving vinyl-containing ionic liquid monomer-1-vinyl-3-butylimidazole bistrifluoromethane sulfonyl imide salt, polyethylene glycol diacrylate monomer and lithium salt-LiBF 4 in acetonitrile solution according to the mass ratio of 2:1:2, adding thermal initiator-isopropylbenzene hydroperoxide which is 1% of the total mass of the ionic liquid monomer and the polyethylene glycol diacrylate monomer, taking 40 mu L of solid electrolyte-containing solution by using a pipette, dripping the solution on the surface of a pole piece, polymerizing the monomer at 70 ℃ for 8h, and then drying the solution at 80 ℃ in vacuum for 12h to remove the acetonitrile solution, thereby obtaining the positive pole piece with the solid electrolyte coated on the surface. The mass of the solid electrolyte is 2% of the total mass of the active positive electrode layer after weighing and coating the mass of the front and rear electrode plates. The thickness of the coated positive electrode layer is 100 mu m, accounting for 40% of the active positive electrode layer, and the thickness of the continuous solid electrolyte thin layer on the surface of the pole piece is 3 mu m.
Assembling and testing of the battery: the button cell was assembled using the above-mentioned coated electrode sheet, the negative electrode was a lithium sheet having a diameter of 16mm, the separator was a PP 40 μm thick, and the electrolyte was 1M LiPF 6/EC/DMC/EMC (1:1:1 vol%) and 2% VC. And testing the assembled battery on a Xinwei battery charge-discharge instrument, wherein the testing temperature is 25 ℃, and the testing potential window is 2.7-4.0V.
Experimental results: LFP materials showed good cycling stability with a 200 cycle capacity retention of 97%.
Example 5
Preparation of a positive plate:
The positive electrode material, namely lithium iron phosphate (LFP), the binder, namely PVDF and the conductive agent, namely acetylene black are dissolved in an NMP solvent according to the mass ratio of 90:5:5, and are magnetically stirred for 12 hours, so that the evenly mixed slurry is obtained. Then the slurry is coated on the surface of aluminum foil by scraping, and vacuum drying is carried out for 12 hours at 85 ℃ to remove NMP solvent, thus obtaining a pole piece with the thickness of the positive electrode active layer of 300 mu m, and the pole piece is filled into a small disc with the diameter of 15 mm. Dissolving vinyl-containing ionic liquid monomer-1-vinyl-3-butylimidazole bistrifluoromethane sulfonyl imide salt, polyethylene glycol diacrylate monomer and lithium salt-LiTFSI in acetonitrile solution according to the mass ratio of 2:1:2, adding photoinitiator 2-hydroxy-methyl phenyl propane-1-ketone accounting for 5% of the total mass of the ionic liquid monomer and the polyethylene glycol diacrylate monomer, taking 30 mu L of solid electrolyte-containing solution by using a pipette, dripping the solution on the surface of a pole piece, UV photocuring for 1-60min, and vacuum drying at 80 ℃ for 12h to remove the acetonitrile solution, thereby obtaining the positive pole piece with the solid electrolyte coated on the surface. The mass of the solid electrolyte is 2% of the total mass of the active positive electrode layer after weighing and coating the mass of the front and rear electrode plates. The thickness of the coated positive electrode layer is 90 mu m, accounting for 30% of the active positive electrode layer, and the thickness of the continuous solid electrolyte thin layer on the surface of the pole piece is 2 mu m.
Assembling and testing of the battery: the button cell was assembled using the above-mentioned coated electrode sheet, the negative electrode was a lithium sheet having a diameter of 16mm, the separator was a 40 μm thick PP, and the electrolyte was 1M LiPF 6/EC/DMC/EMC (1:1:1 vol%) and 5% LiDFOB. And testing the assembled battery on a Xinwei battery charge-discharge instrument, wherein the testing temperature is 25 ℃, and the testing potential window is 2.7-4.0V.
Experimental results: LFP materials show good cycling stability with a 200 cycle capacity retention of 95%.
Example 6
Preparation of a positive plate:
The positive electrode material-ternary positive electrode NCM523, the binder-PVDF and the conductive agent-acetylene black are dissolved in NMP solvent according to the mass ratio of 90:5:5, and magnetically stirred for 12 hours, so as to obtain the uniformly mixed slurry. Then the slurry is coated on the surface of aluminum foil by scraping, and vacuum drying is carried out for 12 hours at 85 ℃ to remove NMP solvent, thus obtaining a pole piece with the thickness of the positive electrode active layer of 200 mu m, and the pole piece is filled into a small disc with the diameter of 15 mm. And (3) dissolving the polyion liquid-polydimethyl diallyl ammonium bis (trifluoromethyl sulfonyl) imide and lithium salt-LiTFSI in acetonitrile solution according to the mass ratio of 3:1, dripping 10 mu L of solid electrolyte-containing solution on the surface of the pole piece by using a pipette, and vacuum drying at 80 ℃ for 12 hours to remove the acetonitrile solution, thereby obtaining the positive pole piece with the solid electrolyte coated on the surface. The mass of the solid electrolyte is 5% of the total mass of the active positive electrode layer after the mass of the pole pieces before and after coating is weighed. The thickness of the coated positive electrode layer is 20 mu m, the coated positive electrode layer accounts for 10% of the active positive electrode layer, and the thickness of the continuous solid electrolyte thin layer on the surface of the pole piece is 10 mu m.
Assembling and testing of the battery: the button cell was assembled using the above-mentioned coated electrode sheet, and a lithium sheet having a diameter of 16mm was used as the negative electrode, and a PP having a thickness of 40 μm was used as the separator, and 1M LiPF 6/EC/DMC/EMC (1:1:1 vol%) and 1% LiPF 2O2 were used as the electrolyte. And testing the assembled battery on a Xinwei battery charge-discharge instrument, wherein the testing temperature is 25 ℃, and the testing potential window is 2.7-4.5V.
Experimental results: NCM materials show good cycling stability at high voltages with a 200 cycle capacity retention of 90%. Electrolyte analysis showed lower dissolution of metal ions.
Example 7
Preparation of a positive plate:
The positive electrode material namely Lithium Nickel Manganese Oxide (LNMO), the binder namely PVDF and the conductive agent namely acetylene black are dissolved in an N, N-dimethylformamide solvent according to the mass ratio of 90:5:5, and the mixture is magnetically stirred for 12 hours, so that the evenly mixed slurry is obtained. Then the slurry is coated on the surface of aluminum foil, and is dried for 12 hours in vacuum at 85 ℃ to remove N, N-dimethylformamide solvent, thus obtaining a pole piece with the thickness of the positive electrode active layer of 100 mu m, and the pole piece is filled into a small disc with the diameter of 15 mm. And (3) dissolving the polyion liquid-polydimethyl diallyl ammonium bis (trifluoromethyl sulfonyl) imide and lithium salt-LiTFSI in acetonitrile solution according to the mass ratio of 3:1, dripping 100 mu L of solid electrolyte-containing solution on the surface of the pole piece by using a pipette, and vacuum drying at 80 ℃ for 12 hours to remove the acetonitrile solution, thereby obtaining the positive pole piece with the solid electrolyte coated on the surface. The mass of the solid electrolyte is 2% of the total mass of the active positive electrode layer after weighing and coating the mass of the front and rear electrode plates. The thickness of the coated positive electrode layer is 50 mu m, the coated positive electrode layer accounts for 50% of the active positive electrode layer, and the thickness of the continuous solid electrolyte thin layer on the surface of the pole piece is 5 mu m.
Assembling and testing of the battery: the button cell was assembled using the above-mentioned coated electrode sheet, the negative electrode was a lithium sheet having a diameter of 16mm, the separator was a 40 μm thick PP, and the electrolyte was 1M LiPF 6/EC/DMC/EMC (1:1:1 vol%) and 5% FEC. And testing the assembled battery on a Xinwei battery charge-discharge instrument, wherein the testing temperature is 25 ℃, and the testing potential window is 3.0-4.9V.
Experimental results: the LNMO material showed good cycling stability at high voltage with a 200 cycle capacity retention of 85%. Electrolyte analysis showed lower dissolution of metal ions.
Example 8
Preparation of a positive plate:
The positive electrode material, namely lithium manganese iron phosphate (LMFP), the binder, namely PVDF and the conductive agent, namely acetylene black are dissolved in an aqueous solvent according to the mass ratio of 90:5:5, and are magnetically stirred for 12 hours, so that the evenly mixed slurry is obtained. Then the slurry is coated on the surface of aluminum foil, and vacuum drying is carried out for 12 hours at 85 ℃ to remove the solvent, thus obtaining the pole piece with the thickness of the positive electrode active layer of 100 mu m, and the pole piece is filled into a small disc with the diameter of 15 mm. And (3) dissolving the polyion liquid-polydimethyl diallyl ammonium bis (trifluoromethyl sulfonyl) imide and lithium salt-LiTFSI in acetonitrile solution according to the mass ratio of 3:1, dripping 100 mu L of solid electrolyte-containing solution on the surface of the pole piece by using a pipette, and vacuum drying at 80 ℃ for 12 hours to remove the acetonitrile solution, thereby obtaining the positive pole piece with the solid electrolyte coated on the surface. The mass of the solid electrolyte is 2% of the total mass of the active positive electrode layer after weighing and coating the mass of the front and rear electrode plates. The thickness of the coated positive electrode layer is 50 mu m, the coated positive electrode layer accounts for 50% of the active positive electrode layer, and the thickness of the continuous solid electrolyte thin layer on the surface of the pole piece is 5 mu m.
Assembling and testing of the battery: the button cell was assembled using the above-mentioned coated electrode sheet, the negative electrode was a lithium sheet having a diameter of 16mm, the separator was a 40 μm thick PP, and the electrolyte was 1M LiPF 6/EC/DMC/EMC (1:1:1 vol%) and 1% LiDFOB. And testing the assembled battery on a Xinwei battery charge-discharge instrument, wherein the testing temperature is 25 ℃, and the testing potential window is 2.7-4.3V.
Experimental results: the LMFP material shows good cycling stability, the 200-cycle capacity retention rate is 93%, and the electrolyte analysis result shows that the Mn 2+ metal ions are dissolved relatively low.
In addition, the inventors conducted the same experiments by replacing the positive electrode active material particles of lithium cobaltate in example 1 with lithium manganate, lithium nickel manganate, ternary positive electrode material, lithium iron phosphate, lithium manganese iron phosphate, etc., respectively, and also obtained similar results to example 1.
In addition, the inventors conducted the same experiment by replacing acetylene black as a conductive agent in example 1 with SUPER-P, KS-6, carbon nanotubes, graphene, carbon fiber VGCF, etc., respectively, and also obtained similar results to example 1.
In addition, the inventors of the present invention conducted the same experiment by replacing the binder polyvinylidene fluoride in example 1 with polyacrylic acid, styrene-butadiene rubber, polyamide, polyvinyl alcohol, polyethylenimine, polyimide, etc., respectively, and also obtained similar results to example 1.
In addition, the inventors conducted the same experiment by replacing the film forming additive FEC in example 1 with PS, VC, liPF 2O2 and lipfob, respectively, and also obtained similar results to example 1.
In addition, the inventors conducted the same experiment by replacing the thermal initiator azobisisobutyronitrile in example 2 with azobisisoheptonitrile, dibenzoyl peroxide, dialkyl peroxide, potassium persulfate, cumene hydroperoxide, t-butyl hydroperoxide, etc., respectively, and also obtained similar results to example 2.
In addition, the present inventors have conducted the same experiment by replacing the photoinitiator 2-hydroxy-methylphenyl propane-1-one in example 5 with 1-hydroxycyclohexylphenyl ketone, 2-methyl-1- (4-methylthiophenyl) -2-morpholino-1-propanone, bis (2, 4, 6-trimethylbenzoyl) phenylphosphine oxide, etc., respectively, and also obtained similar results to example 5.
Comparative example 1
Preparation of a positive plate:
The positive electrode material, namely lithium manganese iron phosphate (LMFP), the binder, namely PVDF and the conductive agent, namely acetylene black are dissolved in an NMP solvent according to the mass ratio of 90:5:5, and are magnetically stirred for 12 hours, so that the evenly mixed slurry is obtained. Then the slurry is coated on the surface of aluminum foil by scraping, and vacuum drying is carried out for 12 hours at 85 ℃ to remove NMP solvent, thus obtaining a pole piece with the thickness of the positive electrode active layer of 100 mu m, and the pole piece is filled into a small-disc electrode with the diameter of 15 mm.
Assembling and testing of the battery: the coin cell was assembled using the above-described pole pieces, the negative electrode was a 16mm diameter lithium sheet, the separator was 40 μm thick PP, and the electrolyte was 1M LiPF 6/EC/DMC/EMC (1:1:1 vol%). And testing the assembled battery on a Xinwei battery charge-discharge instrument, wherein the testing temperature is 25 ℃, and the testing potential window is 2.7-4.3V.
Experimental results: the LMFP electrode which is not modified by the solid electrolyte has poor circulation stability, and the 200-cycle capacity retention rate is 85%. The electrolyte analysis results show higher dissolution of Mn 2+ metal ions.
The various aspects, embodiments, features and examples of the invention are to be considered in all respects as illustrative and not intended to limit the invention, the scope of which is defined solely by the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art without departing from the spirit and scope of the claimed invention.
The use of headings and chapters in this disclosure is not meant to limit the disclosure; each section may apply to any aspect, embodiment, or feature of the present invention.
Throughout this disclosure, where a composition is described as having, comprising, or including a particular component, or where a process is described as having, comprising, or including a particular process step, it is contemplated that the composition of the teachings of the present invention also consist essentially of, or consist of, the recited component, and that the process of the teachings of the present invention also consist essentially of, or consist of, the recited process step.
Unless specifically stated otherwise, the use of the terms "comprising (include, includes, including)", "having (has, has or has)" should generally be understood to be open-ended and not limiting.
It should be understood that the order of steps or order in which a particular action is performed is not critical, as long as the present teachings remain operable. Furthermore, two or more steps or actions may be performed simultaneously.
In addition, the inventors have conducted experiments with other materials, process operations, and process conditions as described in this specification with reference to the foregoing examples, and have all obtained desirable results.
While the invention has been described with reference to an illustrative embodiment, it will be understood by those skilled in the art that various other changes, omissions and/or additions may be made and substantial equivalents may be substituted for elements thereof without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. Moreover, unless specifically stated any use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another.

Claims (22)

1. A novel positive electrode structure, characterized by comprising in order: the active coating positive electrode comprises a current collecting layer, an active uncoated positive electrode layer, an active coated positive electrode layer and a solid electrolyte layer, wherein the solid electrolyte layer consists of continuous polymer solid electrolyte and covers the surface of the active coated positive electrode layer, the active uncoated positive electrode layer and the active coated positive electrode layer jointly form an active positive electrode layer, the active positive electrode layer comprises positive electrode active material particles, a conductive agent and a binder, the active coated positive electrode layer further comprises polymer solid electrolyte, the polymer solid electrolyte is coated on the surfaces of the positive electrode active material particles, and the polymer solid electrolyte is distributed and filled in pores among the positive electrode active material particles contained in a part of the active positive electrode layer close to the solid electrolyte layer;
The content of the polymer solid electrolyte in the novel positive electrode structure gradually decreases along the direction from the solid electrolyte layer to the current collecting layer, wherein the polymer solid electrolyte is selected from any one or more than two of a mixture of a polymer and a lithium salt, a mixture of a polyionic liquid and a lithium salt and a mixture of a polymer and an inorganic solid electrolyte; the polymer is poly (diene dimethyl ammonium) bistrifluorosulfonimide salt of polyion liquid, and the polyion liquid is formed by in-situ copolymerization of ionic liquid monomer containing cations or anions and polymer monomer; the ionic liquid monomer is selected from any one or the combination of more than two of imidazole ionic liquid, pyrrole ionic liquid, pyridine ionic liquid and piperidine ionic liquid; the polymer monomer contains any one or more than two of reactive groups selected from vinyl, allyl, epoxypropyl, amino and hydroxyl;
The content of the polymer solid electrolyte in the active positive electrode layer is 0.1-20wt%, and the thickness ratio of the active coated positive electrode layer to the active positive electrode layer is above 5:100.
2. The novel positive electrode structure according to claim 1, characterized in that: the thickness of the solid electrolyte layer is 10 nm-10 mu m.
3. The novel positive electrode structure according to claim 2, characterized in that: the thickness of the solid electrolyte layer is 10 nm-5 mu m.
4. The novel positive electrode structure according to claim 3, characterized in that: the thickness of the solid electrolyte layer is 50 nm-5 mu m.
5. The novel positive electrode structure according to claim 1, characterized in that: the lithium salt is selected from any one or more than two of LiPF 6、LiBF4、LiClO4 and LiBOB, liFSI, liTFSI.
6. The novel positive electrode structure according to claim 1, characterized in that: the content of the polymer solid electrolyte in the active positive electrode layer is 0.2-20wt%.
7. The novel positive electrode structure according to claim 6, characterized in that: the content of the polymer solid electrolyte in the active positive electrode layer is 0.5-20wt%.
8. The novel positive electrode structure according to claim 1, characterized in that: the content of the positive electrode active material particles in the active positive electrode layer is 50-99wt%.
9. The novel positive electrode structure according to claim 1, characterized in that: the content of the polymer solid electrolyte in the active coating anode layer is 1-10wt%;
and/or the thickness of the active positive electrode layer is 200-500 mu m.
10. The novel positive electrode structure according to claim 1, characterized in that: the thickness ratio of the active coating positive electrode layer to the active positive electrode layer is 5-50:100.
11. The novel positive electrode structure according to claim 1, characterized in that: the thickness ratio of the active uncoated positive electrode layer to the active positive electrode layer is 50-95:100.
12. The novel positive electrode structure according to claim 11, characterized in that: the thickness ratio of the active uncoated positive electrode layer to the active positive electrode layer is 50-80:100.
13. The novel positive electrode structure according to claim 1, characterized in that: the active uncoated positive electrode layer comprises positive electrode active material particles, a conductive agent and a binder, and the positive electrode active material particles are fully contacted with the conductive agent and the binder;
and/or the positive electrode active material particles are selected from any one or more than two of lithium cobaltate, lithium manganate, lithium nickel manganate, ternary positive electrode materials, lithium iron phosphate and lithium manganese iron phosphate;
And/or the conductive agent is selected from any one or more than two of acetylene black, SUPER-P, KS-6, carbon nano tubes, graphene and carbon fibers;
and/or the content of the conductive agent in the active positive electrode layer is 0.5-10wt%;
And/or the binder is selected from any one or more than two of polyvinylidene fluoride, polyacrylic acid, styrene-butadiene rubber, polyamide, polyvinyl alcohol, polyethyleneimine and polyimide;
and/or the content of the binder in the active positive electrode layer is 0.5-10wt%;
And/or the current collecting layer is a sheet or net composed of conductive substances; the conductive substance is selected from any one or the combination of more than two of aluminum, nickel and carbon fibers;
and/or the thickness of the current collecting layer is 5-30 mu m.
14. The novel positive electrode structure according to claim 1 or 2, wherein the surface of the positive electrode active material particles is further provided with a protective film formed of a film forming additive selected from any one or a combination of two or more of 1, 3-propane sultone, fluoroethylene carbonate, vinylene carbonate, lithium difluorophosphate and lithium difluorooxalato borate.
15. The method for producing a novel positive electrode structure according to any one of claims 1 to 14, characterized by comprising:
Providing a uniform mixing reaction system comprising anode active material particles, a conductive agent, a binder and a dispersing agent, wherein the mass ratio of the anode active material particles to the conductive agent to the binder is 70-99: 0.5-15: 0.5-15;
applying the uniform mixed reaction system on a current collecting layer to obtain an active positive electrode layer/current collecting layer composite structure;
Providing a polymer solid electrolyte solution, wherein the polymer solid electrolyte solution comprises a mixed solution of a solvent and any one or more than two of a mixture consisting of ionic liquid monomers, polymer monomers, lithium salts and initiators, a mixture consisting of polyionic liquid and lithium salts and a mixture consisting of polymers and inorganic solid electrolytes; the active positive electrode layer/current collecting layer composite structure is fully contacted with polymer solid electrolyte solution, so that the polymer solid electrolyte solution is dispersed on the surface of the active positive electrode layer and is partially dispersed into pores among positive electrode active material particles contained in the active positive electrode layer, and then the solvent is removed to form a solid electrolyte layer, so that the novel positive electrode structure is obtained;
Or providing a polymer solid electrolyte precursor solution, wherein the content of ionic liquid monomers in the solid electrolyte precursor solution is 50-95 wt%, the content of polymer monomers is 0-40 wt%, and the content of lithium salt is 5-40 wt%; and fully contacting the active positive electrode layer/current collecting layer composite structure with a polymer solid electrolyte precursor solution, so that an active monomer in the polymer solid electrolyte precursor solution is formed on the surface of the active positive electrode layer and is partially diffused into pores among positive electrode active material particles contained in the active positive electrode layer, and then carrying out in-situ polymerization reaction under heating treatment or illumination treatment to form a solid electrolyte layer and an active coated positive electrode layer, thereby obtaining the novel positive electrode structure, wherein the heating treatment temperature is 50-80 ℃, the time is 0.5-10 h, and the illumination treatment time is 1-60 min.
16. The method of manufacturing according to claim 15, wherein: the dispersing agent is selected from any one or more than two of N-methyl pyrrolidone, water and N, N-dimethylformamide.
17. The method of manufacturing according to claim 16, wherein: the dispersing agent is N-methyl pyrrolidone.
18. The method of manufacturing according to claim 15, wherein: the initiator is a photoinitiator and/or a thermal initiator; the thermal initiator is selected from any one or more than two of azodiisobutyronitrile, azodiisoheptonitrile, dibenzoyl peroxide, dialkyl peroxide, potassium persulfate, cumene hydroperoxide and tert-butyl hydroperoxide; the photoinitiator is selected from any one or more than two of 2-hydroxy-methyl phenyl propane-1-ketone, 1-hydroxy cyclohexyl phenyl ketone, 2-methyl-1- (4-methylthiophenyl) -2-morpholinyl-1-acetone and bis (2, 4, 6-trimethylbenzoyl) phenyl phosphine oxide;
And/or the mass ratio of the initiator to the combination of the ionic liquid monomer and the polymer monomer is 0.5-5: 100;
And/or the solvent is selected from any one or more than two of acetonitrile, acetone, tetrahydrofuran, dimethyl sulfoxide, N-methyl pyrrolidone and N, N-dimethylformamide.
19. The method of manufacturing according to claim 18, wherein: the solvent is acetonitrile.
20. A battery comprising a positive electrode, a negative electrode and an electrolyte, wherein the positive electrode adopts the novel positive electrode structure of any one of claims 1 to 14.
21. The battery of claim 20, wherein: the electrolyte also comprises a film forming additive, wherein the film forming additive is selected from any one or more than two of 1, 3-propane sultone, fluoroethylene carbonate, vinylene carbonate, lithium difluorophosphate and lithium difluorooxalato borate.
22. The battery of claim 21, wherein: the content of the film forming additive in the electrolyte is 0.1-5wt%.
CN202011236907.XA 2020-11-09 2020-11-09 Novel positive electrode structure, preparation method thereof and battery Active CN114464765B (en)

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