A positive electrode material, a preparation method thereof, a positive electrode sheet, and a lithium ion battery

Abstract

The application provides a positive electrode material and a preparation method thereof, a positive electrode sheet and a lithium ion battery, and comprises a positive electrode active material and a coating layer coated on the surface of the positive electrode active material, wherein the coating layer comprises a lithium-rich reverse perovskite lithium supplement and a conductive agent, the mass content of the lithium-rich reverse perovskite lithium supplement is 0.01-10% of the mass of the positive electrode active material, and the mass content of the conductive agent is 0.01-3% of the mass of the positive electrode active material. Compared with the prior art, the positive electrode material provided by the application uses a lithium-rich reverse perovskite compound as a lithium supplement, is simultaneously compounded with the positive electrode active material to form a coating type structure, can additionally provide a large amount of lithium ions, makes up for the irreversible lithium loss of the negative electrode, and improves the reversible capacity of the full battery system.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lithium ion batteries, in particular to a positive electrode material, a preparation method thereof, a positive electrode sheet and a lithium ion battery. BACKGROUND

[0002] The available energy content of a lithium ion battery within a certain charge and discharge cycle will decrease due to complex degradation mechanisms, which is usually referred to as "aging mechanism". Common degradation mechanisms are divided into two types, one is active lithium loss (capacity decay) and internal resistance increase (power loss). Among them, the active lithium loss is due to the occurrence of side reactions in the lithium consumption process, such as the formation of SEI film in the process of negative electrode lithiation, lithium precipitation due to insufficient kinetics, and active material loss, etc. In particular, high-capacity silicon-oxygen materials will form by-products such as lithium silicate and lithium oxide during the first lithiation process, resulting in a large loss of active lithium, so that the initial efficiency of conventional silicon-oxygen materials is lower than 80%. In addition, high-capacity Si and Sn negative electrode materials, due to the large volume change during lithiation / delithiation, result in continuous breaking and reformation of SEI, leading to continuous loss of active lithium. In order to make up for the loss of active lithium, various "pre-lithiation" methods have been developed to compensate for the irreversible loss of the negative electrode to increase the reversible capacity, thereby obtaining higher weight energy or volume energy density.

[0003] Current pre-lithiation is divided into negative electrode pre-lithiation and positive electrode pre-lithiation. The negative electrode pre-lithiation is mainly to prepare high pre-lithiation negative electrode powder material, or to supplement lithium by lithium sheet, lithium strip process or to use chemical pre-lithiation, but these methods have high risk coefficient and high cost in the preparation process, and are not compatible with the existing process. While the positive electrode pre-lithiation is to add a lithium supplement additive directly in the preparation process of the positive electrode slurry, and to use the lithium ion provided by the positive electrode lithium supplement additive to compensate for the irreversible lithium consumption of the negative electrode during battery charging.

[0004] In order to apply the positive electrode lithium supplement additive to the battery system, the following conditions need to be met: (1) higher lithium storage capacity in weight and volume than existing cathode materials; (2) the delithiation potential during charging should be lower than the maximum potential of the cathode charging, and the lithiation potential should be lower than the minimum potential during discharging; (3) the lithium supplement additive should not have a significant negative impact on the stability of the electrode material, electrolyte and the entire battery.

[0005] The currently used positive electrode lithium supplementing additives include ternary lithium-rich additives (such as Li5FeO4, Li2NiO2, etc.), nano-composites based on conversion reaction (Li2O:M series, M can be Co, Fe, Mn, etc.), binary lithium compounds (such as Li2O2, Li2O and Li3N), etc., but all have certain defects: 1) the conventional ternary lithium-rich additives have low capacity and strong alkalinity, and are not easy to process; 2) the nano-composites based on conversion reaction will form inert transition metal compounds after the first delithiation; 3) the binary lithium compounds have high lithium supplementing capacity, but produce more gas, and the Li3N has high cost and is unstable, and the Li2O, Li2O2, etc. increase the delithiation overpotential due to the low ion / electron conductivity and poor contact with the conductive network.

[0006] Therefore, it is urgent to develop new positive electrode lithium supplementing additive materials. SUMMARY

[0007] One of the purposes of the present application is to provide a composite positive electrode material with a positive electrode lithium supplementing agent added, which can provide a large amount of lithium ions to compensate for the irreversible lithium loss of the negative electrode and improve the reversible capacity of the battery system.

[0008] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0009] A positive electrode material comprises a positive electrode active material and a coating layer coated on the surface of the positive electrode active material, wherein the coating layer comprises a lithium-rich reverse perovskite lithium supplementing agent and a conductive agent, the mass content of the lithium-rich reverse perovskite lithium supplementing agent is 0.01-10% of the mass of the positive electrode active material, and the mass content of the conductive agent is 0.01-3% of the mass of the positive electrode active material.

[0010] Preferably, the thickness of the coating layer is 2-100 nm.

[0011] Preferably, the lithium-rich reverse perovskite lithium supplementing agent is an amorphous lithium-rich reverse perovskite lithium supplementing agent or a microcrystalline lithium-rich reverse perovskite lithium supplementing agent.

[0012] Preferably, the lithium-rich reverse perovskite lithium supplementing agent is Li 3-f OH a (X1) b (X2) c (X3) d S e ; wherein X1, X2 and X3 are each independently selected from any one of F, Cl and Br; a is 0 or 1, b+c+d+2*e=0.95-1.15, and b>0, c>0, d>0, e>0, 0

[0013] Preferably, the conductive agent is at least one of graphene, graphene oxide, single-walled carbon nanotubes, multi-walled carbon nanotubes, and conductive carbon black.

[0014] A second object of the present application is to provide a preparation method of the positive electrode material as described in any one of the above.

[0015] S1, dispersing the conductive agent in an organic solvent, then adding the positive electrode active material and the lithium-rich anti-perovskite lithium supplementing agent according to a mass ratio, dispersing to obtain a composite slurry;

[0016] S2, drying the composite slurry in a protective atmosphere, the drying temperature is 100-180℃, and the drying time is 2-30min, and the positive electrode material is obtained after drying.

[0017] Preferably, in step S2, the drying is spray drying in a spray dryer or drying in a tube furnace.

[0018] Preferably, in step S2, the drying step is: pouring the composite slurry into a magnetic boat, drying in a tube furnace in a protective atmosphere, the drying temperature is 100-180℃, the drying time is 2-30min, then heating at 700-900℃ for 2h, taking out the magnetic boat in an environment with a humidity of ≤5% and quenching in liquid nitrogen to obtain the positive electrode material.

[0019] A third object of the present application is to provide a positive electrode sheet, comprising a positive electrode current collector and a positive electrode active material layer coated on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer comprises the positive electrode material as described in any one of the above.

[0020] A fourth object of the present application is to provide a lithium ion battery, comprising a positive electrode sheet, a negative electrode sheet, and a separator interposed between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet is the positive electrode sheet as described above.

[0021] Compared with the prior art, the positive electrode material provided by the present application has the following beneficial effects: the positive electrode material provided by the present application uses a lithium-rich anti-perovskite compound as a lithium supplementing agent, and simultaneously forms a coated structure with the positive electrode active material, which on the one hand ensures the lithium supplementing effect of the lithium-rich anti-perovskite compound due to the uniform coating, and on the other hand increases the connection between the lithium-rich anti-perovskite compound and the positive electrode by using the conductive agent as a transition structure, promotes the transmission of electrons to improve the poor conductivity of the anti-perovskite structure, and the flexible conductive structure also protects the anti-perovskite structure to improve its brittleness and increase the structural strength of the anti-perovskite compound. Therefore, the lithium supplementing agent structure provided by the present application is stable and has good electrical performance, can additionally provide a large amount of lithium ions, makes up for the irreversible loss of lithium at the negative electrode, and improves the reversible capacity of the full battery system. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 This is a schematic diagram of the structure of the cathode material of the present invention. Detailed Implementation

[0023] 1. Cathode materials and their preparation methods

[0024] A first aspect of the present invention is to provide a positive electrode material, comprising a positive electrode active material and a coating layer coated on the surface of the positive electrode active material, wherein the coating layer comprises a lithium-rich anti-perovskite lithium supplement agent and a conductive agent, wherein the mass content of the lithium-rich anti-perovskite lithium supplement agent is 0.01 to 10% of the mass of the positive electrode active material; and the mass content of the conductive agent is 0.01 to 3% of the mass of the positive electrode active material.

[0025] Specifically, the mass content of the lithium-rich anti-perovskite lithium supplement can be 0.01-1%, 1-3%, 3-5%, 5-8%, or 8-10% of the mass of the positive electrode active material; the mass content of the conductive agent can be 0.01-0.1%, 0.1-0.5%, 0.5-1%, 1-2%, or 2-3% of the mass of the positive electrode active material.

[0026] Among them, anti-perovskite materials are isomorphic to perovskite and can be represented as ABX3, but the positive and negative ions occupy opposite positions in the structure. That is, the A-site and B-site ions of perovskite are cations, and X is an anion; while the A-site and B-site ions of anti-perovskite are anions. Therefore, anti-perovskite has unique cation-rich characteristics and exhibits a wide range of physical properties.

[0027] This invention applies lithium-rich anti-perovskite compounds as positive electrode lithium replenishing agents in lithium-ion batteries. Lithium-rich anti-perovskites, such as Li₂HOX and Li₃OX (X = Cl, Br, I), have high theoretical capacities, with a lithium content of 40%–60%. They exhibit high delithiation capacity between 3 and 5V, with Li₂OHCl releasing up to 812 mAh·g. -1 Furthermore, lithium-rich anti-perovskite compounds also possess ultrafast lithium-ion conductivity (10⁻⁶). -6 ~10 -3 S·cm -1 They possess advantages such as high electrochemical stability (with an upper voltage window of 5-7V), good wettability with electrode materials, and low interfacial impedance. Furthermore, due to the unique physicochemical properties of lithium-rich anti-perovskites, they exhibit low melting points and easy processing, such as Li3OCl and Li3OCl. 0.5 Br 0.5 The melting points of all of them are below 300℃, which makes them more conducive to material processing and structural design. The processing and preparation process is simple and low-cost.

[0028] But if the lithium-rich anti-perovskite is directly mixed into the positive electrode structure, it cannot form a coating layer structure with the positive electrode active material, which will cause the enrichment of the lithium supplement agent and the unevenness of lithium extraction, thereby increasing the risk of lithium extraction of the lithium ion battery. If the lithium-rich anti-perovskite is directly used to coat the positive electrode active material, the poor conductivity of the anti-perovskite structure cannot effectively control the coating thickness, which will affect the electronic conductivity. Therefore, the conductive agent is added in the present application, the conductive agent coats the inner layer of the positive electrode active material, and the anti-perovskite nano-particles are uniformly and densely dispersed and combined with the positive electrode active material and the conductive agent. On the one hand, the conductive agent promotes electron transmission and accelerates the electron conduction between the positive electrode material and the current collector; on the other hand, the conductive agent protects the anti-perovskite structure, improves the brittleness thereof, and increases the connection between the anti-perovskite structure and the positive electrode as a transition structure. In addition, the lithium-rich anti-perovskite structure is moderate, not resistant to large external mechanical impact and showing strong brittleness. Directly using the lithium-rich anti-perovskite to coat the positive electrode active material cannot guarantee the structural strength of the positive electrode material. The introduction of the flexible conductive agent can increase the structural strength of the lithium-rich anti-perovskite and ensure the stability of the positive electrode material.

[0029] In some embodiments, the lithium-rich anti-perovskite is a nano-particle. The ultra-fine nano-particle anti-perovskite can quickly conduct ions and achieve the effect of lithium supplement.

[0030] In some embodiments, the thickness of the coating layer can be 2-10 nm, 10-20 nm, 20-30 nm, 30-40 nm, 40-50 nm, 50-60 nm, 60-70 nm, 70-80 nm, 80-90 nm, or 90-100 nm. A suitable coating layer is more conducive to the electron transfer between the current collector and the positive electrode active material.

[0031] In some embodiments, the lithium-rich anti-perovskite lithium supplement agent is an amorphous lithium-rich anti-perovskite lithium supplement agent or a microcrystalline lithium-rich anti-perovskite lithium supplement agent. The energy gap of the lithium-rich anti-perovskite is relatively wide, the electronic conductivity is poor, and the ion conductivity of the defect-free lithium-rich anti-perovskite crystal is relatively weak. The concentration of a large amount of crystalline lithium-rich anti-perovskite will also restrict the electron conduction and ion conduction of the positive electrode active material layer. The present application uses an amorphous or microcrystalline lithium-rich anti-perovskite as a lithium supplement agent, and introduces a conductive agent in the coating layer, which can greatly improve the ion diffusion capacity of the lithium-rich anti-perovskite, and the formation of a suitable coating layer thickness and a large amount of conductive agent network will be more conducive to the electron transfer between the current collector and the positive electrode particles, and ensure the uniform lithium supplement effect of the lithium-rich anti-perovskite structure.

[0032] In some embodiments, the lithium-rich anti-perovskite lithium supplement agent is Li 3-f OH a (X1) b (X2) c (X3) d Se ; wherein X1, X2, X3 are independently selected from any one of F, Cl, Br; a is 0 or 1, b+c+d+2*e = 0.95-1.15, and b>0, c>0, d>0, e>0, 0

[0033] In some embodiments, when a is 0, the lithium-rich inverse perovskite lithium supplementing agent can be Li3OX (X=F, Cl or Br), Li3O(X1) b (X2) c (X1, X2 are two different elements from F, Cl or Br, b+c=0.95-1.15, and b>0, c>0), Li3OX b S e (X is one element from F, Cl or Br, b+2*e=0.95-1.15, and b>0, e>0), Li3O(X1) b (X2) c (X3) d (X1, X2, X3 are three different elements from F, Cl or Br, b+c+d=0.95-1.15, and b>0, c>0, d>0), Li3O(X1) b (X2) c S e (X1, X2 are two different elements from F, Cl or Br, b+c+2*e=0.95-1.15, and b>0, c>0, e>0).

[0034] In some embodiments, when a is 1, the lithium-rich inverse perovskite lithium supplementing agent can be Li2OHX (X=F, Cl or Br), Li2OH(X1) b (X2) c (X1, X2 are two different elements from F, Cl or Br, b+c=0.95-1.15, and b>0, c>0), Li2OHX b S e (X is one element from F, Cl or Br, b+2*e=0.95-1.15, and b>0, e>0), Li2OH(X1) b (X2) c (X3) d (X1, X2, X3 are three different elements from F, Cl or Br, b+c+d=0.95-1.15, and b>0, c>0, d>0), Li2OH(X1) b (X2) c S e (X1, X2 are two different elements from F, Cl or Br, b+c+2*e=0.95-1.15, and b>0, c>0, e>0).

[0035] Preferably, the conductive agent is at least one of graphene, graphene oxide, single-walled carbon nanotubes, multi-walled carbon nanotubes, and conductive carbon black.

[0036] Preferably, the positive electrode active material can be one or more of a combination of compounds represented by the chemical formulae such as Li g Ni x Co y M z O 2-h N h Preferably, the positive electrode active material can be one or more of a combination of compounds represented by the chemical formulae such as Li 0.5 Mn 1.5 O4, LiCoPO4, LiMnPO4, LiFePO4, LiNiPO4, LiCoFSO4, CuS2, FeS2, MoS2, NiS, TiS2, etc. More preferably, the positive electrode active material is any one of lithium cobaltate, a ternary layered positive electrode material, or lithium iron phosphate.

[0037] The preparation method of the positive electrode material comprises the following steps:

[0038] S1, dispersing a conductive agent in an organic solvent, then adding a positive electrode active material and a lithium-rich anti-perovskite lithium supplement according to a mass ratio, dispersing to obtain a composite slurry;

[0039] S2, drying the composite slurry in a protective atmosphere, the drying temperature is 100-180°C, and the drying time is 2-30 min, and the positive electrode material is obtained after drying.

[0040] Preferably, the conductive agent is at least one of graphene, graphene oxide, single-walled carbon nanotubes, multi-walled carbon nanotubes, and conductive carbon black.

[0041] Preferably, in step S2, the drying is spray drying in a spray dryer, or drying in a tube furnace.

[0042] Preferably, in step S2, the drying step is: pouring the composite slurry into a magnetic boat, drying in a tube furnace under a protective atmosphere, the drying temperature is 100-180℃, the drying time is 2-30min, after drying, heating at 700-900℃ for 2h, taking out the magnetic boat under ambient humidity≤5% and putting into liquid nitrogen for quenching, to obtain the positive electrode material.

[0043] 2. Positive electrode sheet

[0044] The second aspect of the present application provides a positive electrode sheet, comprising a positive electrode current collector and a positive electrode active material layer coated on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer comprises the positive electrode material according to any one of the above.

[0045] 3. Lithium ion battery

[0046] The third aspect of the present application provides a lithium ion battery, comprising a positive electrode sheet, a negative electrode sheet and a separator interposed between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet is the positive electrode sheet according to the above.

[0047] The active material layer coated on the negative electrode sheet can be one or more of, but not limited to, graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, silicon-based material, tin-based material, lithium titanate or other metals capable of forming alloys with lithium, etc. The graphite can be selected from one or more of artificial graphite, natural graphite and modified graphite; the silicon-based material can be selected from one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites and silicon alloys; the tin-based material can be selected from one or more of elemental tin, tin oxide compounds and tin alloys. Due to the lithium supplementing performance of the positive electrode of the present application, the positive electrode material of the present application is matched with the silicon-oxygen material for use, which can effectively solve the loss of active lithium of the negative electrode material, thereby obtaining higher weight energy or volume energy density.

[0048] The separator can be various materials suitable for lithium ion battery separators in the art, for example, it can be a combination of one or more of, but not limited to, polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester and natural fiber, etc.

[0049] In order to make the technical solutions and advantages of the present application clearer, the present application and its beneficial effects will be described in further detail below with reference to the specific embodiments and the accompanying drawings, but the embodiments of the present application are not limited thereto.

[0050] Example 1

[0051] A positive electrode material, comprising a positive electrode active material and a coating layer coated on the surface of the positive electrode active material, wherein the coating layer comprises a lithium-rich anti-perovskite lithium supplement and a conductive agent, the mass content of the lithium-rich anti-perovskite lithium supplement is 0.01-10% of the mass of the positive electrode active material; and the mass content of the conductive agent is 0.01-3% of the mass of the positive electrode active material.

[0052] The preparation method of the positive electrode material is as follows:

[0053] S1, 0.8g of single-walled carbon nanotubes is added to 200g of dimethyl carbonate solvent and uniformly dispersed by ultrasonic or stirring, then 300g of commercial lithium cobalt oxide positive electrode material and 10g of Li3OCl 0.5 Br 0.5 anti-perovskite powder and dispersed by ultrasonic or stirring until a uniform slurry is formed to obtain a composite slurry;

[0054] S2, the composite slurry is sprayed and dried in a spray dryer with N2 or Ar as protection, the heating temperature is 100-180℃, the heating time is 2-30min, and after drying, it is sealed and stored to obtain LCO@Li3OCl 0.5 Br 0.5 -CNT positive electrode material.

[0055] Example 2

[0056] Different from example 1 is the lithium-rich anti-perovskite lithium supplement added, the lithium-rich anti-perovskite lithium supplement of this embodiment is Li3OF 0.29 Cl 0.41 Br 0.30 , and the obtained positive electrode material is LCO@Li3OF 0.29 Cl 0.41 Br 0.30 -CNT.

[0057] The rest is the same as example 1, which will not be repeated here.

[0058] Example 3

[0059] Different from example 1 is the lithium-rich anti-perovskite lithium supplement added, the lithium-rich anti-perovskite lithium supplement of this embodiment is Li2OHF 0.29 Cl 0.41 Br 0.30 ; and the obtained positive electrode material is LCO@Li2OHF 0.29 Cl 0.41 Br 0.30 -CNT.

[0060] The rest is the same as example 1, which will not be repeated here.

[0061] Example 4

[0062] The difference between this embodiment and embodiment 1 is the mass ratio of the lithium-rich anti-perovskite lithium supplement to the positive active material. The commercial lithium cobalt oxide positive material in this embodiment is 200 g, Li3OCl 0.5 Br 0.5 The anti-perovskite powder is 10 g.

[0063] The rest is the same as embodiment 1, which will not be repeated here.

[0064] Embodiment 5

[0065] The difference between this embodiment and embodiment 1 is the mass ratio of the lithium-rich anti-perovskite lithium supplement to the positive active material. The commercial lithium cobalt oxide positive material in this embodiment is 100 g, Li3OCl 0.5 Br 0.5 The anti-perovskite powder is 10 g.

[0066] The rest is the same as embodiment 1, which will not be repeated here.

[0067] Embodiment 6

[0068] The difference between this embodiment and embodiment 1 is the mass ratio of the lithium-rich anti-perovskite lithium supplement to the positive active material. The commercial lithium cobalt oxide positive material in this embodiment is 1000 g, Li3OCl 0.5 Br 0.5 The anti-perovskite powder is 10 g.

[0069] The rest is the same as embodiment 1, which will not be repeated here.

[0070] Embodiment 7

[0071] The difference between this embodiment and embodiment 2 is the mass ratio of the lithium-rich anti-perovskite lithium supplement to the positive active material. The commercial lithium cobalt oxide positive material in this embodiment is 200 g, Li3OF 0.29 Cl 0.41 Br 0.30 The anti-perovskite powder is 10 g.

[0072] The rest is the same as embodiment 2, which will not be repeated here.

[0073] Embodiment 8

[0074] The difference between this embodiment and embodiment 2 is the mass ratio of the lithium-rich anti-perovskite lithium supplement to the positive active material. The commercial lithium cobalt oxide positive material in this embodiment is 100 g, Li3OF 0.29 Cl 0.41 Br 0.30 The anti-perovskite powder is 10 g.

[0075] The rest is the same as embodiment 2, which will not be repeated here.

[0076] Example 9

[0077] Different from example 2, the mass ratio of the added lithium-rich anti-perovskite lithium supplement to the positive active material. The commercial lithium cobalt oxide positive material in this example is 1000g, Li3OF 0.29 Cl 0.41 Br 0.30 Anti-perovskite powder is 10g.

[0078] The rest is the same as example 2, which will not be repeated here.

[0079] Example 10

[0080] Different from example 1, the preparation method of the positive material.

[0081] S1, 0.8g of single-walled carbon nanotubes is added to 200g of dimethyl carbonate solvent and dispersed uniformly by ultrasonic or stirring, then 300g of commercial lithium cobalt oxide positive material and 10g of Li3OCl 0.5 Br 0.5 Anti-perovskite powder is added and dispersed by ultrasonic or stirring until a uniform slurry is formed to obtain a composite slurry;

[0082] S2, pour the composite slurry into a magnetic boat, dry in a tube furnace, and use N2 or Ar as protection, heating temperature is 100-180℃, heating time is 2-30min, after drying, then heat at 800℃ for 2h, take out the magnetic boat and put into liquid nitrogen for quenching, the operation environment humidity is ≤5%, to obtain LCO@Li3OCl 0.5 Br 0.5 -CNT positive material, collect the powder and seal for storage.

[0083] The rest is the same as example 1, which will not be repeated here.

[0084] Example 11

[0085] Different from example 2, the preparation method of the positive material.

[0086] S1, 0.8g of single-walled carbon nanotubes is added to 200g of dimethyl carbonate solvent and dispersed uniformly by ultrasonic or stirring, then 300g of commercial lithium cobalt oxide positive material and 10g of Li3OF 0.29 Cl 0.41 Br 0.30 Anti-perovskite powder is added and dispersed by ultrasonic or stirring until a uniform slurry is formed to obtain a composite slurry;

[0087] S2, pour the composite slurry into a magnetic boat, dry in a tube furnace, and have N2 or Ar as protection, heating temperature 100-180℃, heating time 2-30min, after drying, then heat at 800℃ for 2h, take out the magnetic boat and put into liquid nitrogen for quenching, operating environment humidity ≤5%, obtain LCO@Li3OF 0.29 Cl 0.41 Br 0.30 -CNT positive electrode material, collect the powder and seal for storage.

[0088] The rest is the same as example 2, which will not be repeated here.

[0089] Example 12

[0090] Different from example 11 is the mass ratio of the added lithium-rich anti-perovskite lithium supplement to the positive electrode active material. The commercial lithium cobaltate positive electrode material in this embodiment is 200g, and the Li3OF 0.29 Cl 0.41 Br 0.30 The anti-perovskite powder is 10g.

[0091] The rest is the same as example 11, which will not be repeated here.

[0092] Comparative example 1

[0093] Different from example 1 is the positive electrode material structure, and the coating layer of this comparative example does not contain a conductive agent.

[0094] The preparation method is: take 200g of dimethyl carbonate solvent, then add 300g of commercial lithium cobaltate positive electrode material and 10g of Li3OCl 0.5 Br 0.5 anti-perovskite powder, and disperse by ultrasonic or stirring until a uniform slurry is formed. The composite slurry is sprayed and dried in a spray dryer, and has N2 or Ar as protection, heating temperature 100-180℃, heating time 2-30min, and is sealed after drying.

[0095] The rest is the same as example 1, which will not be repeated here.

[0096] Comparative example 2

[0097] Different from example 2 is the positive electrode material structure, and the coating layer of this comparative example does not contain a conductive agent.

[0098] The preparation method is: take 200g of dimethyl carbonate solvent, then add 300g of commercial lithium cobaltate positive electrode material and 10g of Li3OF 0.29 Cl 0.41 Br 0.30The anti-perovskite powder is dispersed by ultrasonic or stirring until a uniform slurry is formed. The composite slurry is spray dried in a spray dryer with N2or Ar as protection, the heating temperature is 100-180℃, the heating time is 2-30min, and the dried product is stored in a sealed container.

[0099] The rest is the same as in Example 2, which will not be repeated here.

[0100] Comparative Example 3

[0101] The positive electrode material of this comparative example is a conventional commercial lithium cobalt oxide positive electrode material.

[0102] The positive electrode materials of Examples 1-12 and Comparative Examples 1-3 above are prepared into positive electrode sheets, and their charge-discharge performance is tested (0.1C constant current charge cut-off voltage 4.5V, constant voltage to 0.02C, 0.1C discharge cut-off voltage 3V).

[0103] Preparation method of the positive electrode sheet: the positive electrode material is mixed with a conductive agent and a binder, and an appropriate amount of NMP solvent is added dropwise to form a uniform slurry by grinding, wherein the mass ratio of the positive electrode material: conductive agent: binder is 90:5:5, and the solid content of the slurry is between 50-68%; then the obtained slurry is uniformly coated on an Al foil, and dried at 110℃ under vacuum conditions to obtain a positive electrode sheet.

[0104] The obtained positive electrode sheet is punched into an electrode sheet with a diameter of 12mm, weighed, and assembled into a coin cell in a glove box, with a Li sheet as a reference electrode and a counter electrode, and a commercial lithium ion battery electrolyte used as the coin cell electrolyte.

[0105] The test results are shown in Table 1.

[0106] Table 1

[0107]

[0108] In the full battery system, under the condition of a certain negative electrode, the energy density of the system is not high, the energy density of the system depends on the active lithium content of the system, and the low first efficiency negative electrode will form an SEI film, consuming a large amount of active lithium ions. High charge capacity can effectively compensate for the irreversible loss of the negative electrode, which helps to improve the energy density.

[0109] From the test results of the above Examples 1-12 and Comparative Examples 1-3, compared with the conventional commercial lithium cobalt oxide cathode material, the introduction of lithium-rich reverse perovskite lithium supplement can effectively increase the charge capacity of the cathode, and different types of lithium-rich reverse perovskite lithium supplement will cause the charge capacity to be different, through the comparison of Examples 1-3, it can be known that the lithium-rich reverse perovskite lithium supplement in Example 2 is more obvious for the improvement of the charge capacity. However, if only the lithium-rich reverse perovskite lithium supplement is introduced (see Comparative Examples 1-2), the improvement of the charge specific capacity of the battery is limited, which is mainly because the reverse perovskite structure has poor conductivity, and the coating thickness cannot be effectively controlled, which will affect the electronic conductivity. After introducing the conductive agent in the coating layer, such as Examples 1-12, the charge capacity of the battery can be further improved. In addition, by adjusting the preparation process of the sample, the charge capacity can be further improved, the irreversible loss of the anode can be better compensated, and the lithium supplement effect of the cathode can be better achieved.

[0110] According to the disclosure and teaching of the above description, those skilled in the art of the present application can also make changes and modifications to the above embodiments. Therefore, the present application is not limited to the above specific embodiments, and any obvious improvements, replacements or modifications made by those skilled in the art on the basis of the present application all belong to the protection scope of the present application. In addition, although some specific terms are used in the present specification, these terms are only for convenience of description and do not constitute any limitation on the present application.

Claims

1. A lithium-ion battery cathode material, characterized in that, The positive electrode active material and a coating layer coated on the surface of the positive electrode active material, wherein the coating layer comprises a lithium-rich reverse perovskite lithium supplement and a conductive agent, the mass content of the lithium-rich reverse perovskite lithium supplement is 3-10% of the mass of the positive electrode active material, and the mass content of the conductive agent is 0.5-3% of the mass of the positive electrode active material; The lithium-rich reverse perovskite lithium supplement is Li3OX, and X is F, Cl or Br. or the lithium-rich anti-perovskite lithium supplementing agent is Li3O (X1) b (X2) c , X1 and X2 are two different elements selected from F, Cl and Br, b + c = 0.95-1.15, and b > 0 and c > 0; or the lithium-rich anti-perovskite lithium supplementing agent is Li3O (X1) b (X2) c (X3) d X1, X2, X3 are three different elements selected from F, Cl or Br, b+c+d=0.95~1.15, and b>0, c>0, d>0; The conductive agent is at least one of graphene, graphene oxide, single-walled carbon nanotubes and multi-walled carbon nanotubes.

2. The lithium-ion battery cathode material of claim 1, wherein, The thickness of the coating layer is 2-100 nm.

3. The lithium-ion battery cathode material of claim 1, wherein, The lithium-rich reverse perovskite lithium supplement is an amorphous lithium-rich reverse perovskite lithium supplement or a microcrystalline lithium-rich reverse perovskite lithium supplement.

4. The method for preparing the lithium-ion battery cathode material according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: S1. The conductive agent is dispersed in an organic solvent, and then the positive electrode active material and the lithium-rich reverse perovskite lithium supplement are added in a mass ratio to obtain a composite slurry; S2. The composite slurry is dried in a protective atmosphere, the drying temperature is 100-180 DEG C, and the drying time is 2-30 min, and the positive electrode material is obtained after drying.

5. The method for preparing the lithium-ion battery cathode material as described in claim 4, characterized in that, In step S2, the drying is spray drying in a spray dryer or drying in a tube furnace.

6. The method for preparing the lithium-ion battery cathode material as described in claim 5, characterized in that, In step S2, the drying step is: the composite slurry is poured into a porcelain boat, and dried in a tube furnace in a protective atmosphere, the drying temperature is 100-180 DEG C, the drying time is 2-30 min, and then the porcelain boat is taken out and immersed in liquid nitrogen for quenching under an ambient humidity of ≤5%, and the positive electrode material is obtained.

7. A lithium-ion battery positive electrode sheet comprising a positive electrode current collector and a positive electrode active material layer coated on at least one surface of the positive electrode current collector, characterized in that, The positive electrode active material layer comprises the positive electrode material according to any one of claims 1-3.

8. A lithium-ion battery comprising a positive electrode sheet, a negative electrode sheet, and a separator interposed between the positive electrode sheet and the negative electrode sheet, characterized by, The positive electrode sheet is the positive electrode sheet according to claim 7.

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