Composite lithium supplement agent, positive plate, battery, battery pack and electric equipment

Abstract

The invention provides a composite lithium supplement agent, a positive plate, a battery and electric equipment, the composite lithium supplement agent comprises a lithium supplement agent matrix, a first coating layer existing on the surface of the lithium supplement agent matrix, and a second coating layer located on the side, away from the lithium supplement agent matrix, of the first coating layer, the first coating layer comprises an oxide, the oxide comprises MxOy, m comprises one or more of Al, Si, Mn, Zn, Sn, Cu, Mo, Ge and Ti, x is larger than or equal to 1 and smaller than or equal to 2, y is larger than or equal to 1 and smaller than or equal to 3, the second coating layer comprises a conductive material and a hydrophobic polymer, the composite lithium supplement agent has the low moisture absorption rate and the low surface residual alkali content, and therefore the charge-discharge specific capacity of the battery is remarkably improved.

Description

[0001] The present invention claims priority to a Chinese patent invention filed with the Patent Office of China on April 3, 2025, with application number 202510421379.1 and titled “A composite lithium supplement, positive electrode sheet, battery and electrical equipment”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present invention belongs to the technical field of lithium-ion batteries, and in particular relates to a composite lithium supplement, a positive electrode sheet, a battery, a battery pack and electrical equipment. Background Art

[0003] During the first charge of a lithium-ion battery, the SEI film formed on the surface of the negative electrode will irreversibly consume the lithium ions in the battery system, thereby affecting the energy density and cycle life of the lithium-ion battery. To address this problem, the "pre-lithiation" technology came into being. Pre-lithiation is to add a lithium supplement to the lithium-ion battery to compensate for the lithium ions consumed by the formation of the SEI film during the first charge, which can significantly improve the initial capacity and cycle life of the battery. Among the lithium supplement technologies for lithium-ion batteries, positive electrode lithium supplementation is widely used because of its simple process, strong compatibility, and high lithium supplementation efficiency. However, in the existing technology, the lithium supplement has a high moisture absorption rate and a high surface residual alkali content, which easily triggers side reactions and consumes active lithium ions. At the same time, it leads to the formation of an unstable interface layer at the interface between the electrode and the electrolyte, increases the interface impedance, and causes the battery's charge and discharge specific capacity to be poor. Therefore, there is an urgent need for a lithium supplement with both a low moisture absorption rate and a low surface residual alkali content to improve the battery's charge and discharge specific capacity. Summary of the Invention

[0004] The present invention provides a composite lithium supplement, a positive electrode sheet, a battery, a battery pack and an electrical device, which at least solve the problems of high moisture absorption rate and high surface residual alkali content of the lithium supplement in the prior art.

[0005] The present invention provides a composite lithium supplement, comprising a lithium supplement matrix, a first coating layer present on the surface of the lithium supplement matrix, and a second coating layer located on a side of the first coating layer away from the lithium supplement matrix, wherein the first coating layer comprises an oxide, and the oxide comprises M x O y , wherein M includes one or more elements selected from Al, Si, Mn, Zn, Sn, Cu, Mo, Ge, and Ti, 1≤x≤2, 1≤y≤3, and the second coating layer includes a conductive material and a hydrophobic polymer.

[0006] According to one embodiment of the present invention, the mass ratio of the lithium supplement matrix to the oxide is 1:a, 0<a≤10%;

[0007] And / or, the mass ratio of the lithium supplement matrix to the conductive material is 1:b, 0<b≤10%;

[0008] And / or, the mass ratio of the lithium supplement agent matrix to the hydrophobic polymer is 1:c, 0<c≤10%.

[0009] According to one embodiment of the present invention, 0.1%≤a≤2%;

[0010] And / or, b:c=(1-5):(1-5).

[0011] According to one embodiment of the present invention, the particle size D50 of the oxide is 10 nm to 300 nm;

[0012] And / or, the particle size D50 of the conductive material is 10 nm-300 nm;

[0013] And / or, the particle size D50 of the lithium supplement matrix is ​​1 μm-30 μm.

[0014] According to one embodiment of the present invention, the lithium supplement matrix includes one or more of Li6CoO4, Li6ZnO4, Li5AlO4, Li7NbO6, and Li8SnO6;

[0015] And / or, the conductive material includes an inorganic conductive carbon material and / or an organic conjugated polymer, the inorganic conductive carbon material includes one or more of graphene, carbon nanotubes, fullerene, activated carbon, and acetylene black, and the organic conjugated polymer includes one or more of polydopamine, polypyrrole, polyaniline, polyacetylene, polythiophene, polyphenylene vinylene, and polyparaphenylene imide;

[0016] And / or, the hydrophobic polymer includes one or more of polysiloxane, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, polystyrene, polybutylene, and polyfluoroethylene-chlorotrifluoroethylene.

[0017] Another aspect of the present invention provides a method for preparing the composite lithium supplement, comprising the following steps:

[0018] (1) subjecting a mixture containing a lithium supplement agent matrix and an oxide to a first heat treatment to form a first coating layer on the surface of the lithium supplement agent matrix to obtain a first intermediate;

[0019] (2) The first intermediate, the conductive material and the hydrophobic polymer are mixed and then subjected to a second heat treatment to form a second coating layer on the side of the first coating layer of the first intermediate facing away from the lithium supplement agent matrix, thereby obtaining a composite lithium supplement agent.

[0020] According to one embodiment of the present invention, in the first heat treatment, the treatment temperature is 300° C.-800° C., and the treatment time is 2 h-10 h;

[0021] And / or, in the second heat treatment, the treatment temperature is 100° C.-500° C., and the treatment time is 2 h-10 h.

[0022] Another aspect of the present invention provides a positive electrode sheet comprising a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode active material layer comprises the above-mentioned composite lithium supplement or the composite lithium supplement prepared according to the above-mentioned preparation method.

[0023] Another aspect of the present invention provides a battery comprising the above-mentioned positive electrode sheet.

[0024] Another aspect of the present invention provides a battery pack comprising at least two batteries as described above that are connected to each other.

[0025] Another aspect of the present invention provides an electrical device comprising the above-mentioned battery or the above-mentioned battery pack.

[0026] The composite lithium supplement agent of the present invention comprises a lithium supplement agent matrix, a first coating layer present on the surface of the lithium supplement agent matrix, and a second coating layer located on the side of the first coating layer away from the lithium supplement agent matrix, wherein the first coating layer comprises an oxide, and the oxide comprises M x O y , where M comprises one or more of Al, Si, Mn, Zn, Sn, Cu, Mo, Ge, and Ti, 1≤x≤2, and 1≤y≤3, and the second coating layer comprises a conductive material and a hydrophobic polymer. This composite lithium supplement has a low moisture absorption rate and low surface residual alkali content, and can improve the battery's charge and discharge specific capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the structure of the composite lithium supplement of the present invention;

[0028] Figure 2 This is a SEM image of the composite lithium supplement in Example 1 of the present invention;

[0029] Figure 3 This is the SEM image of the lithium supplement agent in Comparative Example 1 of the present invention.

[0030] Description of reference numerals:

[0031] 1-lithium supplement matrix; 2-first coating layer; 3-second coating layer. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0033] In the related technologies, there are common defects such as high moisture absorption rate and high residual alkali content on the surface of lithium supplements, which need to be solved urgently.

[0034] In view of this, the embodiment of the present invention provides a composite lithium supplement. Figure 1 is a schematic structural diagram of the composite lithium supplement of the present invention, as shown in FIG. Figure 1 As shown, the composite lithium supplement comprises a lithium supplement matrix 1, a first coating layer 2 on the surface of the lithium supplement matrix 1, and a second coating layer 3 on the side of the first coating layer 2 facing away from the lithium supplement matrix 1, wherein the first coating layer 2 comprises an oxide, and the oxide comprises M x O y , wherein M includes one or more elements selected from Al, Si, Mn, Zn, Sn, Cu, Mo, Ge, and Ti, 1≤x≤2, 1≤y≤3, and the second coating layer 3 includes a conductive material and a hydrophobic polymer.

[0035] According to the inventor's research, under the composition system of the composite lithium supplement agent, the oxide M in the first coating layer x O y At high temperatures, it can react with residual alkali (such as LiOH and Li2CO3) on the surface of the composite lithium supplement agent to reduce the surface residual content of the composite lithium supplement agent, thereby reducing the risk of gelation during the positive electrode slurrying process; the conductive material in the second coating layer has good conductivity, which helps to improve the conductivity of the composite lithium supplement agent. At the same time, the hydrophobic polymer forms a hydrophobic protective layer to effectively reduce the absorption of water, thereby reducing the moisture absorption rate of the composite lithium supplement agent; the hydrophobic polymer in the second coating layer can further reduce the moisture absorption rate of the composite lithium supplement agent, thereby improving the stability of the composite lithium supplement agent and improving the charge and discharge specific capacity of the battery.

[0036] For example, M x O y where x can be 1 or 2, etc., and y can be 1, 2, or 3, etc.

[0037] In some embodiments, M includes one or more elements selected from the group consisting of Al, Si, Mn, Zn, and Ti, which can react better with residual alkali on the surface of the composite lithium supplement, further reducing the residual alkali content on the surface of the composite lithium supplement. Furthermore, M is preferably Al and / or Mn.

[0038] In some embodiments, the mass ratio of the lithium supplement agent matrix to the oxide is 1:a, 0<a≤10%, while reducing the residual content without affecting the electrochemical properties (such as electrical conductivity and lithium ion conductivity) of the lithium supplement agent matrix.

[0039] Illustratively, a may be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc.

[0040] The present invention reduces the moisture absorption rate of the composite lithium supplement agent without affecting the lithium ion conductivity and electrochemical activity of the composite lithium supplement agent by controlling the mass ratio of the lithium supplement agent matrix to the conductive material and the mass ratio of the lithium supplement agent matrix to the hydrophobic polymer.

[0041] In some embodiments, the mass ratio of the lithium supplementing agent matrix to the conductive material is 1:b, 0<b≤10%.

[0042] Illustratively, b may be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc.

[0043] In some embodiments, the mass ratio of the lithium supplementing agent matrix to the hydrophobic polymer is 1:c, 0<c≤10%.

[0044] Illustratively, c may be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc.

[0045] In some embodiments, 0.1%≤a≤2%, which can save the amount of oxide used and effectively reduce the residual amount on the surface of the composite lithium supplement agent.

[0046] Illustratively, a may be 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, 1.1%, 1.3%, 1.6%, 1.8% or 2%, etc.

[0047] In some embodiments, b:c=(1-5):(1-5), so that the composite lithium supplement has a lower moisture absorption rate and better conductivity.

[0048] Exemplarily, b:c can be 1:1, 1:2, 1:3, 1:4, 1:5, 2:1, 2:2, 3:2, 5:2, 1:3, 2:3, 5:3, 1:4, 3:4, 5:4, 1:5, 2:5, 3:5 or 4:5, etc.

[0049] In some embodiments, the particle size D50 of the oxide is 10 nm-300 nm, which helps the oxide form a uniform and continuous first coating layer on the surface of the lithium supplement agent matrix. The oxide has higher reactivity and more effectively reduces the residual amount on the surface of the composite lithium supplement agent.

[0050] For example, the particle size D50 of the oxide may be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 70 nm, 100 nm, 150 nm, 200 nm, 250 nm, or 300 nm, etc.

[0051] In the embodiments of the present invention, the particle size D50 of the oxide is the average particle size D50 of the oxide, which refers to the particle size corresponding to 50% of the total volume of the oxide, starting from the smallest particle size on the particle size distribution curve. The particle size D50 of the oxide can be measured using conventional particle size measurement instruments in the art, such as a laser particle size analyzer.

[0052] In some embodiments, the particle size D50 of the conductive material is 10 nm to 300 nm, which helps the conductive material to be evenly distributed in the hydrophobic polymer, and forms a uniform and continuous second coating layer on the surface of the first coating layer of the lithium supplement agent away from the lithium supplement agent matrix, thereby better reducing the moisture absorption rate of the composite lithium supplement agent.

[0053] For example, the particle size D50 of the conductive material may be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 70 nm, 100 nm, 150 nm, 200 nm, 250 nm or 300 nm, etc.

[0054] In the embodiments of the present invention, the particle size D50 of the conductive material is the average particle size D50 of the conductive material, which refers to the particle size corresponding to 50% of the total volume of the conductive material, starting from the smallest particle size on the particle size distribution curve. The particle size D50 of the conductive material can be measured using conventional particle size measurement instruments in the art, such as a laser particle size analyzer.

[0055] In some embodiments, the particle size D50 of the lithium supplement agent matrix is ​​1 μm-30 μm, which has excellent mechanical stability and can better resist volume changes during charging and discharging, while also improving the reactivity of the lithium supplement agent matrix and the diffusion rate of lithium ions.

[0056] For example, the particle size D50 of the lithium supplement matrix may be 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm or 30 μm.

[0057] In the embodiments of the present invention, the particle size D50 of the lithium supplement matrix is ​​the average particle size D50 of the lithium supplement matrix. It refers to the particle size corresponding to 50% of the total volume of the lithium supplement matrix, starting from the smallest particle size on the particle size distribution curve of the lithium supplement matrix. The particle size D50 of the lithium supplement matrix can be measured using conventional particle size measurement instruments in the art, such as a laser particle size analyzer.

[0058] In some embodiments, the lithium supplement matrix includes one or more of Li6CoO4, Li6ZnO4, Li5AlO4, Li7NbO6, and Li8SnO6. These lithium supplement matrices have a high lithium content and can significantly improve the battery capacity.

[0059] In some embodiments, the lithium supplement matrix is ​​preferably Li6CoO4, which has high lithium ion conductivity and stable cycle performance, and can further improve the capacity and cycle life of the battery.

[0060] In some embodiments, the conductive material includes an inorganic conductive carbon material and / or an organic conjugated polymer, the inorganic conductive carbon material includes one or more of graphene, carbon nanotubes, fullerenes, activated carbon, and acetylene black, and the organic conjugated polymer includes one or more of polydopamine, polypyrrole, polyaniline, polyacetylene, polythiophene, polyphenylene vinylene, and polyparaphenylene imide, further improving the conductivity and stability of the composite lithium supplement.

[0061] In some embodiments, the hydrophobic polymer includes one or more of polysiloxane, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, polystyrene, polybutylene, polyvinyl fluoride-chlorotrifluoroethylene, and the like, which can reduce the penetration and adsorption of water and effectively reduce the moisture absorption rate of the composite lithium supplement. Furthermore, the hydrophobic polymer includes polyvinylidene fluoride and / or polysiloxane. Polyvinylidene fluoride and polysiloxane have excellent chemical stability, mechanical properties, and hydrophobicity, which can significantly reduce the moisture absorption rate of the composite lithium supplement while imparting excellent stability to the composite lithium supplement.

[0062] Another aspect of the present invention provides a method for preparing the composite lithium supplement, comprising the following steps:

[0063] (1) subjecting a mixture containing a lithium supplement agent matrix and an oxide to a first heat treatment to form a first coating layer on the surface of the lithium supplement agent matrix to obtain a first intermediate;

[0064] (2) The first intermediate, the conductive material and the hydrophobic polymer are mixed and then subjected to a second heat treatment to form a second coating layer on the side of the first coating layer of the first intermediate away from the lithium supplement agent matrix, thereby obtaining a composite lithium supplement agent.

[0065] The composite lithium supplement prepared by the preparation method has low moisture absorption rate and surface residual alkali content. At the same time, the preparation method is simple in process and convenient for industrial production.

[0066] In some embodiments, the preparation process of the lithium supplement agent matrix includes: grinding and mixing a lithium source and a doping metal source, and performing a sintering process to obtain the lithium supplement agent matrix.

[0067] In some embodiments, the lithium source includes one or more of lithium hydroxide, lithium oxide, lithium carbonate, and lithium oxalate, and the doping metal source includes one or more of cobalt source, zinc source, aluminum source, niobium source, and tin source.

[0068] In some embodiments, the cobalt source includes one or more of cobalt carbonate, cobaltous oxide, cobalt hydroxide, cobalt oxalate, and cobalt acetate; the zinc source includes one or more of zinc hydroxide, zinc oxide, zinc carbonate, and zinc acetate; the aluminum source includes one or more of aluminum hydroxide, aluminum oxide, and aluminum carbonate; the niobium source includes niobium pentoxide; and the tin source includes tin oxide and / or tin sulfide.

[0069] In some embodiments, the sintering temperature is 400-1000° C., preferably 600-800° C., and the sintering time is 3-12 hours, preferably 5-7 hours, which can promote the densification of the lithium supplement matrix and the formation of the crystal phase.

[0070] For example, the sintering temperature may be 400°C, 500°C, 600°C, 700°C, 800°C, 900°C or 1000°C, and the sintering time may be 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h or 12h, etc.

[0071] In some embodiments, the heating rate refers to the rate at which the temperature is increased from the starting temperature to the target sintering temperature (400-1000°C). The heating rate of the sintering process is 1°C / min-7°C / min, which can reduce internal stress and crack formation in the lithium supplement matrix. Furthermore, the heating rate of the sintering process is preferably 1°C / min-3°C / min.

[0072] For example, the heating rate of the sintering process may be 1° C. / min, 2° C. / min, 3° C. / min, 4° C. / min, 5° C. / min, 6° C. / min, or 7° C. / min.

[0073] In some embodiments, the preparation process of the lithium supplement agent matrix further includes natural cooling to room temperature after sintering, and crushing the cooled product in an anhydrous environment to obtain the lithium supplement agent, which helps to ensure the structural integrity and performance stability of the lithium supplement agent matrix.

[0074] In some embodiments, in the first heat treatment, the treatment temperature is 300°C-800°C, preferably 500°C-700°C, and the treatment time is 2h-10h, preferably 7h-9h, which can form a dense and stable first coating layer on the surface of the lithium supplement agent matrix.

[0075] Illustratively, in the first heat treatment, the treatment temperature can be 300°C, 400°C, 500°C, 600°C, 700°C or 800°C, etc., and the treatment time can be 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10h, etc.

[0076] In some embodiments, the heating rate of the first heat treatment is 1° C. / min-7° C. / min, preferably 1° C. / min-3° C. / min, which can reduce the internal stress and crack formation of the first coating layer.

[0077] For example, the heating rate of the first heat treatment may be 1° C. / min, 2° C. / min, 3° C. / min, 4° C. / min, 5° C. / min, 6° C. / min, or 7° C. / min.

[0078] In some embodiments, in step 1), the first heat treatment further includes natural cooling to room temperature, and the cooled product is crushed in an anhydrous environment to obtain a first intermediate, which helps to ensure the structural integrity and performance stability of the first intermediate.

[0079] In some embodiments, in the second heat treatment, the treatment temperature is 100°C-500°C, preferably 100°C-200°C, and the treatment time is 2h-10h, preferably 3h-5h, so that a dense and stable second coating layer can be formed on the side of the first coating layer away from the lithium supplement agent.

[0080] For example, in the second heat treatment, the treatment temperature may be 100°C, 200°C, 300°C, 400°C or 500°C, and the treatment time may be 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10h.

[0081] In some embodiments, the heating rate of the second heat treatment is 1° C. / min-7° C. / min, preferably 1° C. / min-3° C. / min, which can reduce the internal stress and crack formation of the second coating layer.

[0082] For example, the heating rate of the second heat treatment may be 1° C. / min, 2° C. / min, 3° C. / min, 4° C. / min, 5° C. / min, 6° C. / min, or 7° C. / min.

[0083] In some embodiments, in step 2), the second heat treatment further includes natural cooling to room temperature, and the cooled product is crushed in an anhydrous environment to obtain a composite lithium supplement, which can ensure the structural integrity and performance stability of the composite lithium supplement.

[0084] In some embodiments, to avoid interference from impurities and moisture in the air, the sintering process, the first heat treatment, and the second heat treatment are all performed under an inert atmosphere, wherein the inert gas can be selected from one or more of argon, nitrogen, helium, and neon. Under the protection of the inert gas, side reactions are avoided, the product has high purity, good air stability, and uniform particle size distribution.

[0085] Another aspect of the present invention provides a positive electrode sheet comprising a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode active material layer comprises the above-mentioned composite lithium supplement or the composite lithium supplement prepared according to the above-mentioned preparation method.

[0086] In the embodiment of the present invention, the positive electrode active material layer may be provided on one surface of the positive electrode current collector in the thickness direction, or on two opposite surfaces of the positive electrode current collector in the thickness direction.

[0087] Generally, in order to improve the structural stability and conductivity of the positive electrode active material layer, the positive electrode active material layer may further include a binder and a conductive agent.

[0088] Specifically, in the positive electrode active material layer, the mass percentage of the composite lithium supplement agent can be 70% to 99%, for example, 70%, 75%, 80%, 85%, 90%, 93%, 95%, 97%, 99% or a range consisting of any two thereof, the mass fraction of the conductive agent can be 0.5% to 15%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 8%, 10%, 13%, 15% or a range consisting of any two thereof, and the mass fraction of the binder can be 0.5% to 15%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 8%, 10%, 13%, 15% or a range consisting of any two thereof.

[0089] In an embodiment of the present invention, the binder in the positive electrode active material layer can be any binder suitable for the positive electrode known in the art, such as polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), tetrafluoroethylene and its copolymers, polyvinylidene fluoride and its copolymers, polyolefins and their copolymers (for example, polyethylene-polyethylene glycol block copolymers, etc.), polyethers and their copolymers (for example, polyethylene oxide, etc.), polyphenylene ethers and their copolymers, polysiloxanes and their copolymers (for example, polydimethylsiloxane, poly(dimethylsiloxane-co-alkylmethylsiloxane)), polyesters and their copolymers (for example, polyvinyl esters, polyvinyl acetate, polyacrylates, etc.), carboxymethyl cellulose, styrene-butadiene latex, nitrile rubber, and polyacrylic acid (PAA). Specifically, the polyolefin includes one or more of polyethylene, polypropylene, ethylene / propylene copolymer, ethylene / vinylidene fluoride copolymer, and propylene / vinylidene fluoride copolymer; polytetrafluoroethylene and its copolymers can be one or more of tetrafluoroethylene / ethylene copolymer, tetrafluoroethylene / propylene copolymer, tetrafluoroethylene / vinylidene fluoride copolymer, tetrafluoroethylene / ether copolymer, tetrafluoroethylene / branched polyether copolymer, tetrafluoroethylene / vinyl ether copolymer, tetrafluoroethylene / branched polyether / vinyl ether copolymer, and tetrafluoroethylene / silicone copolymer.

[0090] In the embodiment of the present invention, the conductive agent in the positive electrode active material layer can be a conventional conductive material in the art, such as one or more of conductive carbon black, conductive graphite, carbon nanotubes (CNTs), carbon fibers, graphene, acetylene black, and Ketjen black.

[0091] The embodiment of the present invention may adopt a conventional positive electrode current collector in the art, for example, the positive electrode current collector includes copper foil.

[0092] In an embodiment of the present invention, the positive electrode sheet can be prepared by a wet process (coating method) (i.e., after the positive electrode slurry used to form the positive electrode active material layer is coated on the surface of the positive electrode collector, the positive electrode active material layer is formed on the surface of the positive electrode collector through processes such as drying and rolling to prepare the positive electrode sheet).

[0093] In specific implementation, the materials used to form the positive electrode active material layer, such as the composite lithium supplement agent, the conductive agent, and the binder, can be placed in a solvent and dispersed evenly to obtain a positive electrode slurry; the positive electrode slurry is coated on the surface of the positive electrode current collector and dried in a drying equipment such as an oven to remove the solvent to obtain a pole piece precursor; then, conventional rolling equipment is used to roll the pole piece precursor under certain pressure and roller gap conditions, and then the pole piece precursor after rolling is cut into pieces (i.e., cut into negative pole pieces of preset size) to obtain a positive pole piece.

[0094] In the embodiments of the present invention, unless otherwise specified, the processes of coating, drying, rolling and the like involved are all conventional operations in the art, and the equipment used may be conventional equipment in the art, without particular limitation.

[0095] Another aspect of the present invention provides a battery comprising the above-mentioned positive electrode sheet.

[0096] In some embodiments, the battery may be a lithium-ion battery.

[0097] Generally speaking, a battery includes an electrolyte, a cell, and a casing that encapsulates the cell. The electrolyte is injected into the cell within the casing, and the cell includes a positive electrode sheet, a negative electrode sheet, and a separator located between the positive and negative electrodes. The cell can be a laminated cell, where the positive electrode sheet, separator, and negative electrode sheet are stacked in an alternating pattern. Alternatively, the cell can be a wound cell, where the positive electrode sheet, separator, and negative electrode sheet are stacked and then wound.

[0098] The electrolyte of the embodiment of the present invention can be a conventional electrolyte in the field. For example, the electrolyte is a non-aqueous electrolyte, which may specifically include an organic solvent, an additive and an electrolyte salt. The organic solvent includes, for example, one or more of ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC) and propylene carbonate (PC), the additive includes, for example, fluoroethylene carbonate (FEC), the additive includes, for example, vinylene carbonate (VC), the electrolyte salt may include a lithium salt, the lithium salt includes, for example, lithium hexafluorophosphate (LiPF6), etc., but is not limited thereto.

[0099] In the embodiment of the present invention, the separator is used to separate the positive electrode sheet and the negative electrode sheet to prevent the positive electrode sheet and the negative electrode sheet from short-circuiting. The embodiment of the present invention can adopt conventional separators in the art without special limitation.

[0100] In the embodiment of the present invention, conventional shell materials in the art may be used to encapsulate the battery cell. The shell may include, for example, a soft packaging material such as an aluminum-plastic film, but is not limited thereto.

[0101] In the embodiment of the present invention, a lithium sheet may be used as the negative electrode.

[0102] In the embodiment of the present invention, components such as positive electrode sheets, separators and negative electrode sheets can be assembled into a battery by conventional methods in the field. For example, the positive electrode sheets, separators and negative electrode sheets can be stacked in an alternating manner to produce a laminated battery cell (or wound into a wound battery cell); the battery cell is then placed in a shell (outer packaging), and after conventional processes such as liquid injection (i.e., injecting electrolyte) and packaging, the battery is produced.

[0103] An embodiment of the present invention further provides a battery pack, comprising at least two batteries as described above that are connected to each other. The battery pack has corresponding advantages to the batteries described above, which will not be described in detail.

[0104] The battery pack includes a plurality of the above-mentioned batteries, which are connected as single cells to form a battery pack. These batteries can be electrically connected by conventional methods in the art, such as in series, in parallel, or a combination of these connection methods, without particular limitation. These batteries can be electrically connected by conventional methods in the art, such as in series, in parallel, or a combination of these connection methods, without particular limitation.

[0105] Another aspect of the present invention provides an electrical device comprising the above-mentioned battery or the above-mentioned battery pack. The electrical device has the advantages corresponding to the above-mentioned positive electrode sheet, which will not be described in detail.

[0106] The electrical equipment in the embodiments of the present invention can be conventional electrical equipment in this field, such as power equipment (such as electric vehicles, electric cars), electronic equipment (such as mobile phones, tablets, laptops, digital cameras, etc.), wearable devices (such as watches, bracelets, VR glasses, etc.), energy storage power stations, etc., without special restrictions.

[0107] The present invention is further described below through specific examples.

[0108] Example 1

[0109] The composite lithium supplement provided in this embodiment is prepared by the following steps:

[0110] 1) lithium hydroxide and cobalt carbonate are mixed and ground in a molar ratio of 6:1, and the ground mixture is placed in an inert gas Ar protection for sintering treatment, heated to 700°C at a heating rate of 4°C / min, and maintained at 700°C for 8 hours. After the sintering is completed, the mixture is cooled to room temperature in the furnace and crushed to obtain Li6CoO4 powder, a lithium supplement matrix;

[0111] 2) mechanically mixing Li6CoO4 powder and MnO in a mass ratio of 100:1 to obtain a first mixture, placing the first mixture in an inert gas Ar protection for a first heat treatment, heating to 500°C at a heating rate of 4°C / min, maintaining at 500°C for 4 hours, then cooling to room temperature with the furnace, and crushing to obtain a first intermediate (including a lithium supplement agent matrix and a first coating layer coated on the surface of the lithium supplement agent matrix);

[0112] 3) The carbon nanotubes and polyvinylidene fluoride were uniformly mixed in a mass ratio of 2:1 to obtain a second mixture, and then the first intermediate and the second mixture were mechanically mixed in a mass ratio of 98:2 for 2 hours to obtain a third mixture. The third mixture was placed in an inert gas Ar protection for a second heat treatment, heated to 100°C at a heating rate of 1°C / min, maintained at 100°C for 3 hours, and then cooled to room temperature with the furnace, and crushed to obtain a composite lithium supplement.

[0113] Example 2

[0114] The difference between this embodiment and embodiment 1 is that in step 3), carbon nanotubes and polyvinylidene fluoride are uniformly mixed in a mass ratio of 3:1 to obtain a second mixture, and then the first intermediate and the second mixture are mechanically mixed in a mass ratio of 98:2 for 2 hours to obtain a third mixture. The third mixture is placed in an inert gas Ar protection for a second heat treatment, heated to 100°C at a heating rate of 1°C / min, maintained at 100°C for 3 hours, then cooled to room temperature with the furnace, and crushed to obtain a composite lithium supplement.

[0115] Example 3

[0116] The difference between this embodiment and embodiment 1 is that in step 2), Li6CoO4 powder and MnO are mechanically mixed in a mass ratio of 100:2 to obtain a first mixture, and the first mixture is placed in an inert gas Ar protection for a first heat treatment, heated to 500°C at a heating rate of 4°C / min, maintained at 500°C for 4 hours, then cooled to room temperature with the furnace, and crushed to obtain a first intermediate (including a lithium supplement agent matrix and a first coating layer coated on the surface of the lithium supplement agent matrix).

[0117] Example 4

[0118] The difference between this embodiment and embodiment 1 is that, in step 2), Li6CoO4 powder and MnO are mechanically mixed in a mass ratio of 100:2 to obtain a first mixture, and the first mixture is placed in an inert gas Ar protection for a first heat treatment, heated to 500°C at a heating rate of 4°C / min, maintained at 500°C for 4 hours, then cooled to room temperature in the furnace, and crushed to obtain a first intermediate (including a lithium supplement agent matrix and a first coating layer coated on the surface of the lithium supplement agent matrix);

[0119] In step 3), the carbon nanotubes and polyvinylidene fluoride are uniformly mixed in a mass ratio of 3:1 to obtain a second mixture, and then the first intermediate and the second mixture are mechanically mixed in a mass ratio of 98:2 for 2 hours to obtain a third mixture. The third mixture is placed in an inert gas Ar protection for a second heat treatment, heated to 100°C at a heating rate of 1°C / min, maintained at 100°C for 3 hours, then cooled to room temperature with the furnace, and crushed to obtain a composite lithium supplement.

[0120] Example 5

[0121] The difference between this embodiment and embodiment 1 is that in step 2), Li6CoO4 powder and Al2O3 are mechanically mixed in a mass ratio of 100:1 to obtain a first mixture, and the first mixture is placed in an inert gas Ar protection for a first heat treatment, heated to 500°C at a heating rate of 4°C / min, maintained at 500°C for 4 hours, then cooled to room temperature with the furnace, and crushed to obtain a first intermediate (including a lithium supplement agent matrix and a first coating layer coated on the surface of the lithium supplement agent matrix).

[0122] Example 6

[0123] The difference between this embodiment and embodiment 1 is that in step 2), Li6CoO4 powder and SiO2 are mechanically mixed in a mass ratio of 100:1 to obtain a first mixture, and the first mixture is placed in an inert gas Ar protection for a first heat treatment, heated to 500°C at a heating rate of 4°C / min, maintained at 500°C for 4 hours, and then cooled to room temperature with the furnace. After crushing, a first intermediate (including a lithium supplement agent matrix and a first coating layer coated on the surface of the lithium supplement agent matrix) is obtained.

[0124] Example 7

[0125] The composite lithium supplement of this embodiment is prepared by the following steps:

[0126] 1) lithium carbonate and zinc carbonate are mixed and ground in a molar ratio of 3:1, and the ground mixture is placed in an inert gas Ar protection for sintering treatment, heated to 700°C at a heating rate of 4°C / min, and maintained at 700°C for 8 hours. After the sintering is completed, the mixture is cooled to room temperature in the furnace and crushed to obtain Li6ZnO4 powder, a lithium supplement matrix;

[0127] 2) mechanically mixing Li6ZnO4 powder and CuO in a mass ratio of 97:3 to obtain a first mixture, placing the first mixture in an inert gas Ar protection for a first heat treatment, heating to 500°C at a heating rate of 4°C / min, maintaining at 500°C for 4 hours, then cooling to room temperature with the furnace, and crushing to obtain a first intermediate (including a lithium supplement agent matrix and a first coating layer coated on the surface of the lithium supplement agent matrix);

[0128] 3) The activated carbon and the polysiloxane were mixed uniformly in a mass ratio of 1:1 to obtain a second mixture, and then the first intermediate and the second mixture were mechanically mixed in a mass ratio of 96:4 for 2 hours to obtain a third mixture. The third mixture was placed in an inert gas Ar protection for a second heat treatment, heated to 100°C at a heating rate of 1°C / min, maintained at 100°C for 3 hours, and then cooled to room temperature with the furnace, and crushed to obtain a composite lithium supplement.

[0129] Example 8

[0130] The composite lithium supplement of this embodiment is prepared by the following steps:

[0131] 1) lithium oxalate and aluminum hydroxide were mixed and ground in a molar ratio of 3:1, and the ground mixture was placed in an inert gas Ar protection for sintering treatment, heated to 700°C at a heating rate of 4°C / min, and maintained at 700°C for 8 hours. After the sintering was completed, the mixture was cooled to room temperature in the furnace and crushed to obtain Li5AlO4 powder, a lithium supplement matrix;

[0132] 2) mechanically mixing Li5AlO4 powder and Al2O3 in a mass ratio of 92:8 to obtain a first mixture, placing the first mixture in an inert gas Ar protection for a first heat treatment, heating to 500°C at a heating rate of 4°C / min, maintaining at 500°C for 4 hours, then cooling to room temperature with the furnace, and crushing to obtain a first intermediate (including a lithium supplement agent matrix and a first coating layer coated on the surface of the lithium supplement agent matrix);

[0133] 3) Graphene and polyethylene were mixed uniformly in a mass ratio of 5:1 to obtain a second mixture, and then the first intermediate and the second mixture were mechanically mixed in a mass ratio of 95:5 for 2 hours to obtain a third mixture. The third mixture was placed in an inert gas Ar protection for a second heat treatment, heated to 100°C at a heating rate of 1°C / min, maintained at 100°C for 3 hours, and then cooled to room temperature with the furnace, and crushed to obtain a composite lithium supplement.

[0134] Example 9

[0135] The composite lithium supplement of this embodiment is prepared by the following steps:

[0136] 1) lithium oxalate and tin oxide were mixed and ground in a molar ratio of 3:1, and the ground mixture was placed in an inert gas Ar protection for sintering treatment, heated to 700°C at a heating rate of 4°C / min, and maintained at 700°C for 8 hours. After the sintering was completed, the mixture was cooled to room temperature in the furnace and crushed to obtain Li8SnO6 powder, a lithium supplement matrix;

[0137] 2) mechanically mixing Li8SnO6 powder and TiO2 in a mass ratio of 92:8 to obtain a first mixture, placing the first mixture in an inert gas Ar protection for a first heat treatment, heating to 500°C at a heating rate of 4°C / min, maintaining at 500°C for 4 hours, then cooling to room temperature with the furnace, and crushing to obtain a first intermediate (including a lithium supplement agent matrix and a first coating layer coated on the surface of the lithium supplement agent matrix);

[0138] 3) polyaniline and polytetrafluoroethylene were mixed uniformly in a mass ratio of 1:5 to obtain a second mixture, and then the first intermediate and the second mixture were mechanically mixed in a mass ratio of 96:4 for 2 hours to obtain a third mixture. The third mixture was placed in an inert gas Ar protection for a second heat treatment, heated to 100°C at a heating rate of 1°C / min, maintained at 100°C for 3 hours, and then cooled to room temperature in the furnace, and crushed to obtain a composite lithium supplement.

[0139] Example 10

[0140] The composite lithium supplement of this embodiment is prepared by the following steps:

[0141] 1) lithium oxide and cobalt hydroxide are mixed and ground in a molar ratio of 3:1, and the ground mixture is placed in an inert gas Ar protection for sintering treatment, heated to 700°C at a heating rate of 4°C / min, maintained at 700°C for 8 hours, and then cooled to room temperature in the furnace, and crushed to obtain Li6CoO4 powder, a lithium supplement matrix;

[0142] 2) mechanically mixing Li6CoO4 powder and TiO2 in a mass ratio of 97:3 to obtain a first mixture, placing the first mixture in an inert gas Ar protection for a first heat treatment, heating to 500°C at a heating rate of 4°C / min, maintaining at 500°C for 4 hours, then cooling to room temperature with the furnace, and crushing to obtain a first intermediate (including a lithium supplement agent matrix and a first coating layer coated on the surface of the lithium supplement agent matrix);

[0143] 3) polyphenylene vinylene and polyvinylidene fluoride are uniformly mixed in a mass ratio of 3:2 to obtain a second mixture, and then the first intermediate and the second mixture are mechanically mixed in a mass ratio of 97:3 for 2 hours to obtain a third mixture, and the third mixture is placed in an inert gas Ar protection for a second heat treatment, heated to 100°C at a heating rate of 1°C / min, maintained at 100°C for 3 hours, and then cooled to room temperature with the furnace, and crushed to obtain a composite lithium supplement.

[0144] Example 11

[0145] The difference between this embodiment and embodiment 1 is that: in step 3), the carbon nanotubes and polyvinylidene fluoride are uniformly mixed in a mass ratio of 6:1 to obtain a second mixture, and then the first intermediate and the second mixture are mechanically mixed in a mass ratio of 98:2 for 2 hours to obtain a third mixture. The third mixture is placed in an inert gas Ar protection for a second heat treatment, heated to 100°C at a heating rate of 1°C / min, maintained at 100°C for 3 hours, then cooled to room temperature with the furnace, and crushed to obtain a composite lithium supplement.

[0146] Example 12

[0147] The difference between this embodiment and embodiment 1 is that: in step 2), Li6CoO4 powder and MnO are mechanically mixed in a mass ratio of 89:11 to obtain a first mixture, and the first mixture is placed in an inert gas Ar protection for a first heat treatment, heated to 500°C at a heating rate of 4°C / min, maintained at 500°C for 4 hours, then cooled to room temperature with the furnace, and crushed to obtain a first intermediate (including a lithium supplement agent matrix and a first coating layer coated on the surface of the lithium supplement agent matrix).

[0148] Example 13

[0149] The difference between this embodiment and embodiment 1 is that in step 2), Li6CoO4 powder and MnO are mechanically mixed in a mass ratio of 99.9:0.1 to obtain a first mixture, and the first mixture is placed in an inert gas Ar protection for a first heat treatment, heated to 500°C at a heating rate of 4°C / min, maintained at 500°C for 4 hours, then cooled to room temperature with the furnace, and crushed to obtain a first intermediate (including a lithium supplement agent matrix and a first coating layer coated on the surface of the lithium supplement agent matrix).

[0150] Example 14

[0151] The composite lithium supplement of this embodiment is prepared by the following steps:

[0152] 1) lithium hydroxide and cobalt carbonate are mixed and ground in a molar ratio of 6:1, and the ground mixture is placed in an inert gas Ar protection for sintering treatment, heated to 700°C at a heating rate of 4°C / min, and maintained at 700°C for 8 hours. After the sintering is completed, the mixture is cooled to room temperature in the furnace and crushed to obtain Li6CoO4 powder, a lithium supplement matrix;

[0153] 2) mechanically mixing Li6CoO4 powder and MnO in a mass ratio of 91:9 to obtain a first mixture, placing the first mixture in an inert gas Ar protection for a first heat treatment, heating to 500°C at a heating rate of 4°C / min, maintaining at 500°C for 4 hours, then cooling to room temperature with the furnace, and crushing to obtain a first intermediate (including a lithium supplement agent matrix and a first coating layer coated on the surface of the lithium supplement agent matrix);

[0154] 3) The carbon nanotubes and polyvinylidene fluoride were uniformly mixed in a mass ratio of 2:1 to obtain a second mixture, and then the first intermediate and the second mixture were mechanically mixed in a mass ratio of 98:2 for 2 hours to obtain a third mixture. The third mixture was placed in an inert gas Ar protection for a second heat treatment, heated to 100°C at a heating rate of 1°C / min, maintained at 100°C for 3 hours, and then cooled to room temperature with the furnace, and crushed to obtain a composite lithium supplement.

[0155] Example 15

[0156] The difference between this embodiment and embodiment 1 is that: in step 1), lithium hydroxide and niobium pentoxide are mixed and ground in a molar ratio of 14:1, and the ground mixture is placed in an inert gas Ar protection for sintering treatment, heated to 700°C at a heating rate of 4°C / min, and maintained at 700°C for 8 hours. After sintering, the mixture is cooled to room temperature in the furnace and crushed to obtain the lithium supplement agent matrix Li7NbO6 powder.

[0157] Comparative Example 1

[0158] The difference between this comparative example and Example 1 is that no manganese oxide, conductive material and hydrophobic polymer are added, and the lithium supplement is prepared by the following steps:

[0159] Lithium hydroxide and cobalt carbonate are mixed and ground in a molar ratio of 6:1, and the ground mixture is placed in an inert gas Ar protection for sintering treatment, heated to 700°C at a heating rate of 4°C / min, maintained at 700°C for 8 hours, and then cooled to room temperature with the furnace. After crushing, the lithium supplement Li6CoO4 powder is obtained.

[0160] Comparative Example 2

[0161] The lithium supplement provided in this comparative example is prepared by the following steps:

[0162] 1) lithium hydroxide and cobalt carbonate are mixed and ground in a molar ratio of 6:1, the ground mixture is placed in an inert gas Ar protection for sintering treatment, heated to 700°C at a heating rate of 4°C / min, maintained at 700°C for 8 hours, and cooled to room temperature in the furnace after sintering. The lithium supplement Li6CoO4 powder is obtained after crushing;

[0163] 2) mechanically mixing Li6CoO4 powder and MnO in a mass ratio of 99:1 to obtain a first mixture, placing the first mixture in an inert gas Ar protection for a first heat treatment, heating to 500°C at a heating rate of 4°C / min, maintaining at 500°C for 4 hours, and then cooling to room temperature with the furnace. After crushing, a lithium supplement agent (including a lithium supplement agent matrix and a first coating layer coated on the surface of the lithium supplement agent matrix) is obtained.

[0164] Comparative Example 3

[0165] The lithium supplement provided in this comparative example is prepared by the following steps:

[0166] 1) lithium hydroxide and cobalt carbonate are mixed and ground in a molar ratio of 6:1, and the ground mixture is placed in an inert gas Ar protection for sintering treatment, heated to 700°C at a heating rate of 4°C / min, and maintained at 700°C for 8 hours. After the sintering is completed, the mixture is cooled to room temperature in the furnace and crushed to obtain Li6CoO4 powder, a lithium supplement matrix;

[0167] 2) Mechanically mixing Li6CoO4 powder and Al2O3 in a mass ratio of 99:1 to obtain a first mixture, placing the first mixture in an inert gas Ar protection for a first heat treatment, heating to 500°C at a heating rate of 4°C / min, maintaining at 500°C for 4 hours, and then cooling to room temperature with the furnace. After crushing, a lithium supplement agent (including a lithium supplement agent matrix and a first coating layer coated on the surface of the lithium supplement agent matrix) is obtained.

[0168] Comparative Example 4

[0169] The lithium supplement provided in this comparative example is prepared by the following steps:

[0170] 1) lithium hydroxide and cobalt carbonate are mixed and ground in a molar ratio of 6:1, and the ground mixture is placed in an inert gas Ar protection for sintering treatment, heated to 700°C at a heating rate of 4°C / min, and maintained at 700°C for 8 hours. After the sintering is completed, the mixture is cooled to room temperature in the furnace and crushed to obtain Li6CoO4 powder, a lithium supplement matrix;

[0171] 2) Mechanically mixing Li6CoO4 powder and SiO2 in a mass ratio of 99:1 to obtain a first mixture, placing the first mixture in an inert gas Ar protection for a first heat treatment, heating to 500°C at a heating rate of 4°C / min, maintaining at 500°C for 4 hours, and then cooling to room temperature with the furnace. After crushing, a lithium supplement agent (including a lithium supplement agent matrix and a first coating layer coated on the surface of the lithium supplement agent matrix) is obtained.

[0172] Comparative Example 5

[0173] The difference between this comparative example and Example 1 is that no manganese oxide is added, and the composite lithium supplement is prepared by the following steps:

[0174] 1) lithium hydroxide and cobalt carbonate are mixed and ground in a molar ratio of 6:1, and the ground mixture is placed in an inert gas Ar protection for sintering treatment, heated to 700°C at a heating rate of 4°C / min, maintained at 700°C for 8 hours, and then cooled to room temperature in the furnace, and crushed to obtain Li6CoO4 powder, a lithium supplement matrix;

[0175] 2) The carbon nanotubes and polyvinylidene fluoride were uniformly mixed in a mass ratio of 2:1 to obtain a second mixture, and then the Li6CoO4 powder and the second mixture were mechanically mixed in a mass ratio of 98:2 for 2 hours to obtain a third mixture. The third mixture was placed in an inert gas Ar protection for a second heat treatment, heated to 100°C at a heating rate of 1°C / min, maintained at 100°C for 3 hours, and then cooled to room temperature in the furnace. After crushing, a lithium supplement (including a lithium supplement matrix and a second coating layer coated on the surface of the lithium supplement matrix) was obtained.

[0176] Comparative Example 6

[0177] The difference between this comparative example and Example 1 is that no conductive material is added, and the composite lithium supplement is prepared by the following steps:

[0178] 1) lithium hydroxide and cobalt carbonate are mixed and ground in a molar ratio of 6:1, the ground mixture is placed in an inert gas Ar protection for sintering treatment, heated to 700°C at a heating rate of 4°C / min, maintained at 700°C for 8 hours, then cooled to room temperature with the furnace, and crushed to obtain lithium supplement Li6CoO4 powder;

[0179] 2) mechanically mixing Li6CoO4 powder and MnO in a mass ratio of 99:1 to obtain a first mixture, placing the first mixture in an inert gas Ar protection for a first heat treatment, heating to 500°C at a heating rate of 4°C / min, maintaining at 500°C for 4 hours, then cooling to room temperature with the furnace, and crushing to obtain a first intermediate (including a lithium supplement agent matrix and a first coating layer coated on the surface of the lithium supplement agent matrix);

[0180] 3) Mechanically mixing the first intermediate and polyvinylidene fluoride at a mass ratio of 98:2 for 2 hours to obtain a third mixture, and placing the third mixture in an inert gas Ar protection for a second heat treatment, heating to 100° C. at a heating rate of 1° C. / min, maintaining at 100° C. for 3 hours, and then cooling to room temperature with the furnace, and crushing to obtain a composite lithium supplement.

[0181] Comparative Example 7

[0182] The difference between this comparative example and Example 1 is that no hydrophobic polymer is added, and the composite lithium supplement is prepared by the following steps:

[0183] 1) lithium hydroxide and cobalt carbonate are mixed and ground in a molar ratio of 6:1, the ground mixture is placed in an inert gas Ar protection for sintering treatment, heated to 700°C at a heating rate of 4°C / min, maintained at 700°C for 8 hours, then cooled to room temperature with the furnace, and crushed to obtain lithium supplement Li6CoO4 powder;

[0184] 2) mechanically mixing Li6CoO4 powder and MnO in a mass ratio of 99:1 to obtain a first mixture, placing the first mixture in an inert gas Ar protection for a first heat treatment, heating to 500°C at a heating rate of 4°C / min, maintaining at 500°C for 4 hours, then cooling to room temperature with the furnace, and crushing to obtain a first intermediate (including a lithium supplement agent matrix and a first coating layer coated on the surface of the lithium supplement agent matrix);

[0185] 3) Mechanically mixing the first intermediate and the carbon nanotubes at a mass ratio of 98:2 for 2 hours to obtain a third mixture, and placing the third mixture in an inert gas Ar protection for a second heat treatment, heating to 100° C. at a heating rate of 1° C. / min, maintaining at 100° C. for 3 hours, and then cooling to room temperature with the furnace, and crushing to obtain a composite lithium supplement.

[0186] Test example

[0187] The composite lithium supplement, polyvinylidene fluoride, acetylene black, and N-methylpyrrolidone were mixed in a mass ratio of 9:14:1:22 and stirred at 50°C for 8 hours to obtain a uniform slurry. The slurry was then coated on an aluminum foil surface and vacuum-dried at 50°C for 12 hours to obtain a positive electrode sheet. The positive electrode sheet was then cut into small pieces suitable for button cells in a glove box and pressed. The resulting positive electrode sheet, lithium sheet, commercial PE separator for lithium batteries, electrolyte (EC, EMC, DMC mass ratio = 1:1:1), gasket, and spring assembly were then converted into a button cell.

[0188] The type of the lithium supplement agent matrix, the type of the oxide, the type of the conductive material, the type of the hydrophobic polymer, the mass ratio r1 of the lithium supplement agent matrix and the oxide, the mass ratio r2 of the lithium supplement agent matrix and the conductive material, the mass ratio r3 of the lithium supplement agent matrix and the hydrophobic polymer, the mass ratio r4 of the conductive material and the hydrophobic polymer, the particle size D50 of the lithium supplement agent matrix, the particle size D50 of the oxide and the particle size D50 of the conductive material in each embodiment and comparative example are summarized in Table 1. Except for the differences shown in Table 1, the other conditions are basically the same.

[0189] Table 1

[0190]

[0191]

[0192]

[0193] 1) Moisture absorption performance test

[0194] Under constant temperature and humidity conditions of 25°C and 30% humidity, a 0.2000g-0.3000g sample (composite lithium supplements or lithium supplements prepared in the Examples and Comparative Examples) was placed on a high-precision balance. The sample weight change was recorded every 300 seconds for a total of 15 measurements. The moisture absorption rate of the material was calculated using the formula v = [(m1-m2) / m1] / t, where m1 and m2 are the sample masses (g) before and after the test, respectively, and t is the test interval (s), which was 4200 seconds. The test results are shown in Table 2.

[0195] 2) Residual alkali performance test

[0196] Potentiometric titration method, using methanol as a solvent to dissolve the residual alkali on the surface of the composite lithium supplement agent or the lithium supplement agent prepared in the examples and comparative examples to obtain a test solution, and the test solution was subjected to potentiometric titration test, and titration was performed using 0.01M HCl standard solution to obtain a titration curve, and the LiOH and Li2CO3 contents (i.e., the residual alkali content) in the composite lithium supplement agent or the lithium supplement agent were respectively tested. The test results are shown in Table 2.

[0197] 3) 0.01C first charge specific capacity, 0.01C first discharge specific capacity

[0198] The test was conducted using Xinwei's button battery test channel with a voltage window of 2.5-4.3V, a charge current of 0.05C, a 4.3V constant voltage charge cutoff current of 0.01C, a discharge current of 0.05C, and a test temperature of 25°C. The test results are shown in Table 2.

[0199] Table 2

[0200]

[0201]

[0202] Figure 3 This is a SEM image of the lithium supplement matrix in Comparative Example 1 of the present invention. Figure 2 This is the SEM image of the composite lithium supplement in Example 1 of the present invention. Figure 3 , Figure 2 It can be seen that a dense, uniform and continuous first coating layer and a second coating layer are formed on the surface of the lithium supplement agent matrix.

[0203] The following conclusions can be drawn from Table 2:

[0204] By comparing Examples 1-15 with Comparative Examples 1-7, it can be seen that the lithium supplements in Comparative Example 1, which consist of a single lithium supplement matrix, Comparative Examples 2-4, which consist of a matrix coated only with a first coating layer, Comparative Example 5, which consists of a matrix coated only with a second coating layer containing a conductive material and a hydrophobic polymer, and Comparative Examples 6-7, which consist of a matrix coated only with a second coating layer containing either a conductive material or a hydrophobic polymer, have high moisture absorption rates and residual alkali contents, resulting in poor battery charge-discharge capacity. In contrast, the composite lithium supplement in Examples 1-15, which has a first coating layer and a second coating layer coated on the surface of the matrix, exhibits a low moisture absorption rate and low surface residual alkali content, significantly improving the battery's charge-discharge capacity.

[0205] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite lithium supplement, characterized in that: The invention comprises a lithium supplement agent matrix, a first coating layer existing on the surface of the lithium supplement agent matrix, and a second coating layer located on a side of the first coating layer away from the lithium supplement agent matrix; The first coating layer includes an oxide; the oxide includes M x O y , wherein M includes one or more elements selected from the group consisting of Al, Si, Mn, Zn, Sn, Cu, Mo, Ge, and Ti, 1≤x≤2, and 1≤y≤3; The second coating layer includes a conductive material and a hydrophobic polymer.

2. The composite lithium supplement according to claim 1, characterized in that The mass ratio of the lithium supplement matrix to the oxide is 1:a, 0<a≤10%; And / or, the mass ratio of the lithium supplement matrix to the conductive material is 1:b, 0<b≤10%; And / or, the mass ratio of the lithium supplement agent matrix to the hydrophobic polymer is 1:c, 0<c≤10%.

3. The composite lithium supplement according to claim 2, characterized in that: 0.1％≤a≤2％； And / or, b:c=(1-5):(1-5).

4. The composite lithium supplement according to any one of claims 1 to 3, characterized in that: The particle size D50 of the oxide is 10nm-300nm; And / or, the particle size D50 of the conductive material is 10 nm-300 nm; And / or, the particle size D50 of the lithium supplement matrix is ​​1 μm-30 μm.

5. The composite lithium supplement according to any one of claims 1 to 4, characterized in that: The lithium supplement matrix includes one or more of Li6CoO4, Li6ZnO4, Li5AlO4, Li7NbO6, and Li8SnO6; And / or, the conductive material includes an inorganic conductive carbon material and / or an organic conjugated polymer, the inorganic conductive carbon material includes one or more of graphene, carbon nanotubes, fullerene, activated carbon, and acetylene black, and the organic conjugated polymer includes one or more of polydopamine, polypyrrole, polyaniline, polyacetylene, polythiophene, polyphenylene vinylene, and polyparaphenylene imide; And / or, the hydrophobic polymer includes one or more of polysiloxane, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, polystyrene, polybutylene, and polyfluoroethylene-chlorotrifluoroethylene.

6. A method for preparing the composite lithium supplement according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) subjecting a mixture containing a lithium supplement agent matrix and an oxide to a first heat treatment to form a first coating layer on the surface of the lithium supplement agent matrix to obtain a first intermediate; (2) The first intermediate, the conductive material and the hydrophobic polymer are mixed and then subjected to a second heat treatment to form a second coating layer on the side of the first coating layer of the first intermediate facing away from the lithium supplement agent matrix, thereby obtaining a composite lithium supplement agent.

7. The preparation method according to claim 6, characterized in that In the first heat treatment, the treatment temperature is 300°C-800°C, and the treatment time is 2h-10h; And / or, in the second heat treatment, the treatment temperature is 100° C.-500° C., and the treatment time is 2 h-10 h.

8. A positive electrode sheet, characterized in that: The invention comprises a positive electrode current collector and a positive electrode active material layer provided on at least one side surface of the positive electrode current collector, wherein the positive electrode active material layer comprises the composite lithium supplement agent according to any one of claims 1 to 5 or the composite lithium supplement agent prepared according to the preparation method according to claim 6 or 7.

9. A battery, characterized in that: Including the positive electrode sheet according to claim 8.

10. A battery pack, characterized in that: The method comprises at least two batteries according to claim 9 connected to each other.

11. An electrical device, characterized in that: Including the battery according to claim 9 or the battery pack according to claim 10.

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