Negative electrode material and preparation method thereof, negative electrode plate, battery and electric device

Abstract

The invention relates to the technical field of batteries, in particular to a negative electrode material and a preparation method thereof, a negative electrode plate, a battery and an electric device. The preparation method of the negative electrode material comprises the following steps: mixing a first inorganic salt compound and a second inorganic salt compound, and adding the mixture into a first solvent to form a salt solution; adding the etched graphite into a salt solution, mixing, and drying to obtain an intermediate material; the first inorganic salt compound comprises a molybdenum compound; mixing alkali, a first binder and the intermediate material, and carrying out first sintering to obtain porous graphite; and mixing a lithium compound, a second binder and silane, adding the mixture into a second solvent to form a mixed solution, dispersing the porous graphite into the mixed solution, and carrying out second sintering to obtain the negative electrode material. According to the negative electrode material obtained through the method, the specific capacity and the diffusion coefficient of the negative electrode material are effectively improved, and the cycle rate performance is well improved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a negative electrode material and its preparation method, a negative electrode sheet, a battery, and an electrical device. Background Technology

[0002] Graphite, as one of the main negative electrode materials for batteries, has advantages such as low expansion and good cycle performance; however, its specific capacity is relatively low. Compared with graphite, silicon carbon materials have high specific capacity, but suffer from problems such as high full-charge expansion and poor cycle performance.

[0003] Currently, physically mixing graphite and silicon-carbon can effectively improve the specific capacity of anode materials and enhance cycle performance. However, poor consistency in this physical mixing can still lead to deviations in expansion cycle performance and rate performance. Summary of the Invention

[0004] In view of this, the present invention aims to at least partially solve one of the technical problems in the related art. To this end, the present invention provides a negative electrode material and its preparation method, a negative electrode sheet, a battery, and an electrical device, which can obtain a carbon-silicon coated porous graphite negative electrode material with good specific capacity, initial efficiency, and rate performance, and effectively reduce the expansion of the negative electrode material.

[0005] To solve the above-mentioned technical problems, the present invention is implemented as follows: According to one aspect of the present invention, a method for preparing a negative electrode material is provided, comprising the following steps: A first inorganic salt compound and a second inorganic salt compound are mixed and added to a first solvent to form a salt solution; etched graphite is added to the salt solution and mixed, and then dried to obtain an intermediate material; wherein, the first inorganic salt compound includes a molybdenum compound; The alkali, the first binder and the intermediate material are mixed and subjected to a first sintering to obtain porous graphite. A lithium compound, a second binder, and silane are mixed and added to a second solvent to form a mixture. The porous graphite is then dispersed in the mixture and subjected to a second sintering to obtain the negative electrode material.

[0006] In some of these embodiments, the molybdenum compound includes at least one of molybdenum oxide, molybdenum sulfide, molybdenum chloride, and molybdenum nitrate.

[0007] In some embodiments, the second inorganic salt compound includes at least one of nitrates, carbonates, and chlorides; preferably, the second inorganic salt compound includes at least one of zinc chloride, zinc nitrate, potassium carbonate, and lithium carbonate.

[0008] In some embodiments, the first solvent includes at least one of cyclohexane, petroleum ether, benzene, and n-hexane.

[0009] In some embodiments, the second solvent comprises an organic solvent, said organic solvent including at least one of cyclohexane, xylene, benzene, and butanediol.

[0010] In some embodiments, the first adhesive includes at least one of petroleum asphalt, coal tar pitch, phenolic resin, and furfural resin.

[0011] In some embodiments, the second binder comprises asphalt, which includes at least one of petroleum asphalt, coal tar pitch, and natural asphalt.

[0012] In some of these embodiments, the silane comprises a liquid silane, which includes at least one of methyltrimethoxysilane, phenyltrimethoxysilane, tris(dimethylamino)silane, and tetraethylsilane.

[0013] In some embodiments, the lithium compound includes an inorganic lithium compound, preferably, the lithium compound includes at least one of lithium borate, lithium sulfonate, lithium phosphate, and lithium molybdate.

[0014] In some embodiments, the alkali includes at least one of sodium hydroxide, potassium hydroxide, and barium hydroxide.

[0015] In some embodiments, the mass ratio of the first inorganic salt compound to the second inorganic salt compound is 1:(0.5~2).

[0016] In some embodiments, the mass ratio of the first inorganic salt compound, the second inorganic salt compound, and the etched graphite is (1~5):(1~5):100.

[0017] In some embodiments, the mass ratio of the alkali, the first binder, and the intermediate material is (100~500) (5~10):100.

[0018] In some embodiments, the mass ratio of the lithium compound, the second binder, the silane, and the porous graphite is (1~5):(1~5):(1~5):100.

[0019] In some of these embodiments, the mass concentration of the salt solution is 1 wt% to 10 wt%.

[0020] In some of these embodiments, the first sintering includes: sintering at a first temperature in an inert gas atmosphere, followed by sintering with CO2 at a second temperature; The first temperature ranges from 1200℃ to 1350℃, and the sintering time is from 1h to 6h; the second temperature ranges from 950℃ to 1100℃, the sintering time is from 30min to 300min, and the CO2 flow rate is from 10mL / min to 100mL / min.

[0021] In some of these embodiments, the sintering temperature of the second sintering is 1100℃~1300℃, and the sintering time is 1 h~3 h.

[0022] In some embodiments, the drying method is spray drying, wherein the inlet temperature is 200°C and the outlet temperature is 100°C.

[0023] In some embodiments, the etched graphite is obtained by laser etching of graphite; In the laser etching process, the wavelength of the laser is 150nm~1500nm.

[0024] In some of these embodiments, the laser scanning rate is 0.1 cm / s to 100 cm / s.

[0025] In some of these embodiments, the atmosphere for laser etching is at least one of vacuum, nitrogen, or oxygen.

[0026] In some of these embodiments, the laser etching time is 60s to 600s.

[0027] According to another aspect of the present invention, the present invention provides a negative electrode material, comprising: a negative electrode material prepared by the preparation method of the negative electrode material described in any embodiment of one aspect of the present invention.

[0028] In some of these embodiments, the negative electrode material includes active particles and a carbon coating layer covering at least a portion of the surface of the active particles. The active particles include porous graphite, and the carbon coating layer contains at least silicon and lithium elements with a content not equal to 0.

[0029] In some of these embodiments, the particle size of the negative electrode material is 5 μm to 10 μm.

[0030] According to a third aspect of the present invention, a negative electrode sheet is provided, comprising: a current collector, and a coating on at least a portion of the surface of at least one side of the current collector in the thickness direction; The coating includes the negative electrode material prepared by the method for preparing the negative electrode material described in any embodiment of one aspect of the present invention; And / or, the negative electrode material described in any embodiment of another aspect of the present invention.

[0031] According to a fourth aspect of the present invention, the present invention provides a battery comprising: a negative electrode material prepared by the method for preparing the negative electrode material described in any embodiment of one aspect of the present invention; And / or, the negative electrode material described in any embodiment of another aspect of the present invention; and / or, the negative electrode sheet described in any embodiment of a third aspect of the present invention.

[0032] According to a fifth aspect of the present invention, an electrical device is provided, comprising: a negative electrode plate as described in any embodiment of the third aspect of the present invention; And / or, the battery described in an embodiment of the fourth aspect of the present invention.

[0033] Implementing the technical solution of the present invention has at least the following beneficial effects: 1. In this invention, liquid silane is coated onto the surface of porous graphite by liquid phase method and carbonized to obtain nano-silicon coated porous graphite, which improves the specific capacity of the negative electrode material by relying on the nano-silicon; lithium salt is used to improve the diffusion coefficient of the negative electrode material, thereby further improving the first efficiency and its rate performance.

[0034] 2. In a preferred embodiment of the present invention, the intermediate material is activated by alkali to generate a deep pore structure and a macropore structure, and water vapor is used to create pores again, thereby generating nano- and micro-sized pores on the surface and giving full play to the synergistic effect between the two types of pores. This reduces the expansion of nano-silicon during charging and discharging, thereby improving the liquid retention performance, diffusion coefficient and cycle performance of the negative electrode material.

[0035] 3. In a preferred embodiment of the present invention, laser etching technology is used to etch holes on the surface of graphite and inorganic salts are doped into the pores to improve the solvation capability of the negative electrode material and reduce the cyclic expansion of the negative electrode material.

[0036] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0037] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0038] Figure 1 The image shown is a SEM image of the negative electrode material prepared in Example 1 of this invention.

[0039] The accompanying drawings have illustrated specific embodiments of the invention, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0040] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0041] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0042] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0043] Unless otherwise specified, all technical features and optional technical features of this invention can be combined to form new technical solutions.

[0044] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0045] Unless otherwise specified, the terms "comprising" and "including" as used in this invention can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0046] Currently, the main anode materials used in the market are graphite, which has low expansion and good cycle performance, but suffers from low specific capacity. Silicon-carbon materials, while possessing high specific capacity, exhibit high full-charge expansion and poor cycle performance. Although some researchers have improved specific capacity and cycle performance by physically mixing graphite and silicon-carbon, poor consistency in the physical mixing leads to deviations in expansion and cycle performance. To address the low energy density of graphite, a chemical method is needed to dope graphite with silicon to improve specific capacity while simultaneously addressing expansion and cycle performance.

[0047] In view of the technical problems existing in the prior art, the present invention provides a negative electrode material and its preparation method, a negative electrode sheet, a battery and an electrical device, which can obtain a porous graphite negative electrode material coated with silicon carbide, which has good specific capacity, first efficiency and rate performance, and effectively reduces the expansion of the negative electrode material.

[0048] The specific technical solution of the present invention is as follows: [Preparation methods for negative electrode materials] In some embodiments of the present invention, a method for preparing a negative electrode material is provided, comprising the following steps: S101. The first inorganic salt compound and the second inorganic salt compound are mixed and added to the first solvent to form a salt solution; the etched graphite is added to the salt solution and mixed, and then dried to obtain an intermediate material; wherein the first inorganic salt compound includes a molybdenum compound.

[0049] For example, the molybdenum compound includes, but is not limited to, molybdenum trioxide, molybdenum dioxide, sodium molybdate, ammonium molybdate, etc. The salt solution formed by the first inorganic salt compound, when mixed with the etched graphite, can effectively improve the solvation capability of the negative electrode material. The second inorganic salt compound includes, but is not limited to, nitrates and carbonates, such as zinc carbonate. The salt solution formed by the second inorganic salt compound can effectively improve the porosity of the etched graphite. For example, zinc salts can carbonize and create pores in the etched graphite during the sintering and carbonization process, thereby reducing its expansion performance. The first solvent includes, but is not limited to, deionized water, ethanol, cyclohexane, etc. Preferably, the first solvent can be an organic solvent in which both the molybdenum compound and the second inorganic salt compound have good solubility, thereby forming a salt solution of a certain concentration. The above drying method can be heating drying, freeze drying, or spray drying, etc., and is not specifically limited here.

[0050] S102. Mix the alkali, the first binder and the intermediate material, and perform the first sintering to obtain porous graphite.

[0051] For example, the alkali can be potassium hydroxide, sodium hydroxide, barium hydroxide, or calcium hydroxide, etc. The first binder includes, but is not limited to, asphalt, epoxy resin, etc. After mixing the intermediate material obtained in step S101 with the alkali and binder, a first sintering is performed. The alkali can create deep pores in the intermediate material, while simultaneously generating a partially macroporous structure. Through the synergy of micropores and macropores, expansion can be effectively reduced, and the liquid retention performance and diffusion coefficient of the negative electrode material can be improved. Furthermore, a carbon coating layer can be formed during the first sintering process, thereby effectively improving the cycle rate performance of the negative electrode material.

[0052] S103. Lithium compound, second binder and silane are mixed and added to second solvent to form a mixture. Porous graphite is dispersed in the mixture and second sintering is performed to obtain the negative electrode material.

[0053] For example, lithium compounds include, but are not limited to, inorganic lithium salts such as lithium chloride and lithium nitrate, and organic lithium salts such as n-butyllithium. The second binder includes, but is not limited to, natural asphalt and phenolic resin. Silanes include, but are not limited to, silanes that are liquid at room temperature, such as methylsilane and dimethylsilane. By coating the surface of porous graphite with liquid silane using a liquid-phase method and then carbonizing it, nano-silicon-coated porous graphite is obtained. The nano-silicon enhances the specific capacity, and the lithium salt enhances the diffusion coefficient, thereby improving the initial efficiency and rate performance.

[0054] The negative electrode material prepared by the above preparation method has a graphite core with macroporous and microporous structures, and the surface of the graphite core is coated with a tannin coating layer, which can effectively reduce the expansion of the negative electrode material. At the same time, it can also improve the capacity, the diffusion coefficient of the lithium salt, the initial efficiency, and the rate performance.

[0055] In some embodiments, the molybdenum compound includes at least one of molybdenum oxide, molybdenum sulfide, molybdenum chloride, and molybdenum nitrate.

[0056] As examples, molybdenum compounds include, but are not limited to, molybdenum oxides such as molybdenum dioxide, molybdenum trioxide, etc., molybdenum sulfides such as molybdenum sulfate, molybdenum chlorides such as molybdenum pentachloride, molybdenum tetrachloride or molybdenum trichloride, etc., and molybdenum nitrates such as ammonium hexanitrate molybdate, etc.

[0057] In some embodiments, the second inorganic salt compound includes at least one selected from nitrates, carbonates, and chlorides; preferably, the second inorganic salt compound includes at least one selected from zinc chloride, zinc nitrate, potassium carbonate, and lithium carbonate. Exemplarily, the second inorganic salt compound includes, but is not limited to, nitrates such as zinc nitrate and potassium nitrate, carbonates such as zinc carbonate, potassium carbonate, and lithium carbonate, and chlorides such as zinc chloride, potassium chloride, and lithium chloride.

[0058] In some embodiments, the first solvent includes, but is not limited to, one or more of cyclohexane, petroleum ether, benzene, and n-hexane.

[0059] In some embodiments, the second solvent includes an organic solvent, including, but not limited to, one or more of cyclohexane, xylene, benzene, and butanediol.

[0060] In some embodiments, the first binder includes, but is not limited to, one or more of petroleum asphalt, coal tar pitch, phenolic resin, and furfural resin.

[0061] In some embodiments, the second binder includes bitumen, which includes, but is not limited to, one or more of petroleum bitumen, coal tar pitch, and natural bitumen.

[0062] In some embodiments, the silane includes liquid silane, which includes, but is not limited to, one or more of methyltrimethoxysilane, phenyltrimethoxysilane, tris(dimethylamino)silane, and tetraethylsilane.

[0063] In some embodiments, the lithium compound includes inorganic lithium compounds. Preferably, the lithium compound includes, but is not limited to, one or more of lithium borate, lithium sulfonate, lithium phosphate, and lithium molybdate.

[0064] In some embodiments, the base includes, but is not limited to, one or more of sodium hydroxide, potassium hydroxide, and barium hydroxide.

[0065] In some embodiments, the mass ratio of the first inorganic salt compound to the second inorganic salt compound is 1:(0.5~2).

[0066] For example, the mass ratio of the first inorganic salt compound and the second inorganic salt compound can be any one of 1:0.5, 1:0.8, 1:1, 1:1.2, 1:1.5 or 1:2 or any ratio between any two; thus, the concentration of the salt solution can be well controlled, thereby giving the intermediate material good solvation ability and porosity.

[0067] In some embodiments, the mass ratio of the first inorganic salt compound, the second inorganic salt compound, and the etched graphite is (1~5):(1~5):100.

[0068] For example, the mass ratio of the first inorganic salt compound, the second inorganic salt compound, and the etched graphite can be any one of 1:1:100, 1:2:100, 2:5:100, or 5:4:100, or any ratio between any two of them.

[0069] In some embodiments, the mass ratio of alkali, first binder and intermediate material is (100~500) (5~10):100.

[0070] For example, the mass ratio of the alkali, the first binder, and the intermediate material can be any one of 100:5:100, 200:7:100, 300:8:100, 400:9:100, or 500:10:100, or any ratio between any two of these. This allows the alkali to create pores in the intermediate material, resulting in porous graphite with both macropores and micropores, effectively reducing the expansion of the negative electrode material.

[0071] In some embodiments, the mass ratio of lithium compound, second binder, silane and porous graphite is (1~5):(1~5):(1~5):100.

[0072] For example, the mass ratio of lithium compound, second binder, silane, and porous graphite can be any one of 1:1:1:100, 1:2:2:100, 1:2:3:100, or 5:5:5:100, or any ratio between any two of these. This allows for a uniform silicon-carbon coating layer to be formed on the surface of the porous graphite, thereby improving the specific capacity and cycle rate performance of the anode material.

[0073] In some embodiments, the mass concentration of the salt solution is 1 wt% to 10 wt%. Exemplarily, the mass concentration of the salt solution can be any one of 1 wt%, 1.5 wt%, 2 wt%, 3 wt%, 5 wt%, 8 wt%, or 10 wt%, or any point value between any two.

[0074] In some embodiments, the first sintering includes: sintering at a first temperature in an inert gas atmosphere, followed by sintering with CO2 at a second temperature.

[0075] The first temperature range is 1200℃~1350℃, and the sintering time is 1h~6h; the second temperature range is 950℃~1100℃, the sintering time is 30min~300min, and the CO2 flow rate is 10mL / min~100mL / min.

[0076] For example, the first temperature can be any one of 1200℃, 1250℃, or 1350℃, or any value between any two; the sintering time can be any one of 1h, 3h, or 6h. Similarly, the second temperature can be any one of 950℃, 1050℃, or 1100℃, or any value between any two, and the CO2 flow rate can be any one of 10mL / min, 20mL / min, 50mL / min, 80mL / min, or 100mL / min, or any value between any two.

[0077] In some embodiments, the sintering temperature of the second sintering is 1100℃~1300℃, and the sintering time is 1 h~3 h. The sintering temperature of the second sintering can be any one of 1100℃, 1200℃, or 1300℃, or any point value between any two.

[0078] In some embodiments, the drying method is spray drying, during which the inlet temperature is 200°C and the outlet temperature is 100°C.

[0079] In some embodiments, the graphite is etched by laser etching; wherein, during the laser etching process, the wavelength of the laser is 150nm to 1500nm. Exemplarily, the wavelength of the laser can be any one of 150nm, 200nm, 500nm, 800nm, 1000nm, 1200nm, or 1500nm, or any value between any two of them.

[0080] In some embodiments, the laser scanning rate is 0.1 cm / s to 100 cm / s; exemplaryly, the laser scanning rate can be any value between any one or any two of 0.1 cm / s, 0.5 cm / s, 1 cm / s, 10 cm / s, 50 cm / s, 80 cm / s or 100 cm / s.

[0081] In some embodiments, the laser etching atmosphere is a vacuum or a mixture of nitrogen, oxygen, or one or more other gases.

[0082] In some embodiments, the laser etching time is 60s to 600s. Exemplarily, the laser etching time is any value between any one or any two of 60s, 100s, 200s, 300s, 400s, 500s, or 600s.

[0083] [Anode Material] In some embodiments of the present invention, a negative electrode material is provided, including the negative electrode material prepared by the negative electrode material preparation method in any of the above embodiments.

[0084] In some embodiments, the negative electrode material includes active particles and a carbon coating layer covering at least a portion of the surface of the active particles; the active particles include porous graphite, and the carbon coating layer contains at least silicon and lithium elements in amounts not equal to zero.

[0085] Preferably, the negative electrode material comprises negative electrode particles, the surface of which is uniformly coated with a carbon coating layer, i.e., the negative electrode material has a core-shell structure, and the carbon coating layer contains non-zero lithium and non-zero silicon elements. This negative electrode material possesses all the technical effects and functions, as well as advantages, of the above embodiments, which will not be elaborated further here.

[0086] In some embodiments, the particle size of the negative electrode material is 5 μm to 10 μm. Exemplarily, the particle size of the negative electrode material can be any one of 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm or any value between any two.

[0087] [Negative electrode plate] In some embodiments of the present invention, a negative electrode sheet is provided, comprising: a current collector, and a coating on at least a portion of the surface of at least one side of the current collector in the thickness direction, wherein the coating comprises the negative electrode material prepared by the negative electrode material preparation method in any of the above embodiments.

[0088] In some embodiments, the negative electrode sheet includes the negative electrode material in any of the above embodiments.

[0089] Optionally, the negative electrode current collector includes a copper foil, and a coating is applied to part or all of the surface of one or both sides of the copper foil. The coating includes the negative electrode material in any of the above embodiments. It is understood that it also includes an adhesive, etc. The adhesive can be polyvinylidene fluoride, natural rubber, etc., and there is no specific limitation on the adhesive.

[0090] [Battery] In some embodiments of the present invention, a battery is provided, comprising: a negative electrode material prepared by the negative electrode material preparation method in any of the above embodiments.

[0091] In some embodiments, the battery includes the negative electrode material described in any of the above embodiments.

[0092] In some embodiments, the battery includes the negative electrode sheet as described in any of the above embodiments.

[0093] Optionally, the battery may include an outer packaging that can be used to encapsulate the aforementioned electrode assembly and electrolyte. The outer packaging of the battery can be a rigid shell, such as a hard plastic shell, aluminum shell, steel shell, etc. Specifically, the rigid shell may include a housing and a cover plate, wherein the housing may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates enclosing a receiving cavity, the housing having an opening communicating with the receiving cavity, and the cover plate being able to cover the opening to close the receiving cavity, the electrode assembly being encapsulated within the receiving cavity, and the electrolyte being immersed in the electrode assembly; it can also be a soft pack, such as a pouch-type soft pack; the material of the soft pack can be plastic, and examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0094] The present invention does not impose any particular restrictions on the shape of the battery; it can be cylindrical, square, or any other arbitrary shape, and those skilled in the art can choose according to specific practical needs.

[0095] Optionally, the battery may further include a positive electrode, a negative electrode, and a separator. As an example, the positive electrode includes a positive current collector and a positive electrode material disposed on at least one surface of the positive current collector along its thickness direction. The phrase "positive electrode material disposed on at least one surface of the positive current collector" means that the positive electrode material can be disposed on one surface or two surfaces of the positive current collector along its thickness direction. Here, "surface" can refer to the entire area of ​​the positive current collector or only a portion thereof; this application does not impose any particular limitation, as long as the purpose of this application is achieved. In this invention, the separator is not particularly limited, as long as the purpose of this invention is achieved. Optionally, the positive electrode includes a positive electrode material, which includes, but is not limited to, one or more of LiCoO2, LiNiO2, and LiMn2O4. The negative electrode includes a negative electrode material, which includes the negative electrode material in any of the above embodiments. The membrane includes, but is not limited to, a polymer membrane of at least one of polyethylene, polypropylene, polyacrylonitrile, polysulfonyl, polyarylethersulfone, polyvinyl alcohol, and polyvinylidene fluoride.

[0096] [Electrical appliances] In some embodiments of the present invention, an electrical device is provided, comprising: the negative electrode sheet in any of the above embodiments.

[0097] In some embodiments, the electrical device includes the battery described in any of the above embodiments.

[0098] Optionally, the electrical device thus possesses all the features and advantages of the battery described in the above technical solution, which will not be repeated here. Specifically, the battery can serve as a power source for the electrical device or as an energy storage unit for it. The electrical device can be a vehicle, mobile phone, portable device, laptop, ship, spacecraft, electric toy, power tool, energy storage device, amusement equipment, elevator, and lifting equipment, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, or electric airplane toys, etc.; power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc.; energy storage devices can be energy storage walls, base station energy storage, container energy storage, etc.; amusement equipment can be a carousel, a drop tower, etc. The aforementioned vehicles can be gasoline-powered vehicles, natural gas-powered vehicles, or new energy vehicles, and new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. The vehicle contains a battery, which can be located at the bottom, front, or rear of the vehicle. The battery provides power to the vehicle, for example, as its operating power source. The vehicle may also include a controller and a motor; the controller manages the battery's power supply to the motor, for example, to meet the vehicle's power needs during starting, navigation, and driving. The battery can not only serve as the vehicle's operating power source but also as its driving power source, replacing or partially replacing fuel or natural gas to provide propulsion.

[0099] Since the battery provided in this embodiment of the invention adopts all the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, and will not be described in detail here.

[0100] The present invention will be described in detail below with reference to the accompanying drawings and examples. However, the implementation and protection of the present invention are not limited thereto. The following embodiments are only some embodiments of the present invention and are not intended to limit the present invention.

[0101] Example 1 A method for preparing a negative electrode material includes the following steps: S11. Place the graphite in a laser etching machine, evacuate to 1 Pa, and etch the surface for 300 s using the following parameters: laser wavelength of 500 nm, laser scanning rate of 1 cm / s, and nitrogen atmosphere, to obtain etched graphite.

[0102] S12. Add 3g of molybdenum oxide and 3g of zinc chloride to 120g of cyclohexane solvent to prepare a salt solution with a mass concentration of 5wt%. Then add 100g of etched graphite and mix evenly. Spray dry (inlet temperature 200℃, outlet temperature 100℃, flow rate 0.1kg / h, 1h) to obtain intermediate material.

[0103] S13. Mix 100g of intermediate material, 300g of potassium hydroxide and 8g of petroleum asphalt evenly, then heat to 1250℃ for 3h under nitrogen inert atmosphere, then transfer the obtained material to a rotary kiln and cool to 1050℃. Activate by passing carbon dioxide gas through at a flow rate of 50mL / min for 150min, then allow it to cool naturally to room temperature to obtain porous graphite.

[0104] S14. Dissolve 3g of lithium borate and 3g of asphalt in 500g of xylene organic solvent and disperse evenly. Then add 3g of methyltrimethoxysilane and disperse evenly. Then add 100g of porous graphite and disperse evenly. Spray dry the mixture. The resulting material is carbonized at 1200℃ for 2h under a nitrogen inert atmosphere to obtain lithium silicon amorphous carbon-coated graphite composite material, i.e., negative electrode material.

[0105] Example 2 A method for preparing a negative electrode material includes the following steps: S21. Place the graphite in a laser etching machine, evacuate to 10 Pa, and etch the surface for 600 s using the following parameters: laser wavelength of 150 nm, laser scanning rate of 0.1 cm / s, and nitrogen atmosphere, to obtain etched graphite.

[0106] S22. Add 1g of molybdenum sulfide and 1g of zinc nitrate to 200g of cyclohexane solvent to prepare a salt solution with a mass concentration of 1wt%. Then add 100g of etched graphite and mix evenly. Spray dry to obtain intermediate material.

[0107] S23. Mix 100g of intermediate material, 100g of potassium hydroxide and 5g of coal tar pitch evenly, then heat to 1200℃ for 6h under an inert argon atmosphere. Then transfer the resulting material to a rotary kiln and cool it to 950℃. Introduce carbon dioxide gas at a flow rate of 100mL / min for 300min, and then allow it to cool naturally to room temperature to obtain porous graphite.

[0108] S24. Dissolve 1g of lithium sulfonate and 1g of asphalt in 500g of xylene organic solvent and disperse evenly. Then add 1g of phenyltrimethoxysilane and disperse evenly. Then add 100g of porous graphite and disperse evenly. Spray dry and carbonize at 1100℃ for 3h under an argon inert atmosphere to obtain lithium silicon amorphous carbon-coated graphite composite material, i.e., negative electrode material.

[0109] Example 3 A method for preparing a negative electrode material includes the following steps: S31. Place the graphite in a laser etching machine, evacuate to 10 Pa, and etch the surface for 100 s using the following parameters: laser wavelength of 1500 nm, laser scanning rate of 1000 cm / s, and nitrogen atmosphere, to obtain etched graphite.

[0110] S32. Add 5g of molybdenum chloride and 5g of potassium carbonate to 100g of cyclohexane solvent to prepare a salt solution with a mass concentration of 10wt%. Then add 100g of etched graphite and mix evenly. Spray dry to obtain the intermediate material.

[0111] S33. Mix 100g of intermediate material, 500g of potassium hydroxide and 10g of phenolic resin evenly, then heat to 1350℃ for 1h under an inert argon atmosphere. Then transfer the resulting material to a rotary kiln and cool it to 1100℃. Introduce carbon dioxide gas at a flow rate of 10mL / min for 300min, and then allow it to cool naturally to room temperature to obtain porous graphite.

[0112] S34. Dissolve 5g of lithium phosphate and 5g of asphalt in 500g of butanediol organic solvent and disperse evenly. Then add 5g of tris(dimethylamino)silane and disperse evenly. Then add 100g of porous graphite and disperse evenly. Spray dry and carbonize at 1300℃ for 1h under an argon inert atmosphere to obtain lithium silicon amorphous carbon-coated graphite composite material, i.e., negative electrode material.

[0113] Comparative Example 1 A method for preparing a negative electrode material includes the following steps: S41. Add 3g of molybdenum oxide and 3g of zinc chloride to 120g of cyclohexane solvent to prepare a salt solution with a mass concentration of 5wt%. Then add 100g of graphite and mix evenly. Spray dry (inlet temperature 200℃, outlet temperature 100℃, flow rate 0.1kg / h, 1h) to obtain intermediate material.

[0114] S42. Mix 100g of intermediate material, 300g of potassium hydroxide and 8g of petroleum asphalt evenly, then heat to 1250℃ for 3h under nitrogen inert atmosphere, then transfer the obtained material to a rotary kiln and cool to 1050℃. Activate by passing carbon dioxide gas through at a flow rate of 50mL / min for 150min, then allow it to cool naturally to room temperature to obtain porous graphite.

[0115] S43. Dissolve 3g of lithium borate and 3g of asphalt in 500g of xylene organic solvent and disperse evenly. Then add 3g of methyltrimethoxysilane and disperse evenly. Then add 100g of porous graphite and disperse evenly. Spray dry the mixture. The resulting material is carbonized at 1200℃ for 2h under a nitrogen inert atmosphere to obtain lithium silicon amorphous carbon-coated graphite composite material, i.e., negative electrode material.

[0116] Comparative Example 2 A method for preparing a negative electrode material includes the following steps: S51. Place the graphite in a laser etching machine, evacuate to 1 Pa, and etch the surface for 300 s using the following parameters: laser wavelength of 500 nm, laser scanning rate of 1 cm / s, and nitrogen atmosphere, to obtain etched graphite.

[0117] S52. Disperse 100g of etched graphite into 120g of cyclohexane solvent, mix evenly, and spray dry (inlet temperature 200℃, outlet temperature 100℃, flow rate 0.1kg / h, 1h) to obtain intermediate material.

[0118] S53. Mix 100g of intermediate material, 300g of potassium hydroxide and 8g of petroleum asphalt evenly, then heat to 1250℃ for 3h under nitrogen inert atmosphere, then transfer the obtained material to a rotary kiln and cool to 1050℃. Activate by passing carbon dioxide gas through at a flow rate of 50mL / min for 150min, then allow it to cool naturally to room temperature to obtain porous graphite.

[0119] S54. Dissolve 3g of lithium borate and 3g of asphalt in 500g of xylene organic solvent and disperse evenly. Then add 3g of methyltrimethoxysilane and disperse evenly. Then add 100g of porous graphite and disperse evenly. Spray dry the mixture. The resulting material is carbonized at 1200℃ for 2h under a nitrogen inert atmosphere to obtain lithium silicon amorphous carbon-coated graphite composite material, i.e., negative electrode material.

[0120] Comparative Example 3 A method for preparing a negative electrode material includes the following steps: S61. Place the graphite in a laser etching machine, evacuate to 1 Pa, and etch the surface for 300 s according to the following parameters: laser wavelength of 500 nm, laser scanning rate of 1 cm / s, and nitrogen atmosphere, to obtain etched graphite.

[0121] S62. Add 3g of molybdenum oxide and 3g of zinc chloride to 120g of cyclohexane solvent to prepare a salt solution with a mass concentration of 5wt%. Then add 100g of etched graphite and mix evenly. Spray dry (inlet temperature 200℃, outlet temperature 100℃, flow rate 0.1kg / h, 1h) to obtain intermediate material.

[0122] S63. Mix 100g of intermediate material, 300g of potassium hydroxide and 8g of petroleum asphalt evenly, then heat to 1250℃ for 3h under nitrogen inert atmosphere, then transfer the resulting material to a rotary kiln and cool to 1050℃. Activate by passing carbon dioxide gas through at a flow rate of 50mL / min for 150min, then allow it to cool naturally to room temperature to obtain porous graphite, which can be used as a negative electrode material.

[0123] Test example: 1. SEM testing The negative electrode material prepared in Example 1 was subjected to SEM testing, and the results are as follows: Figure 1 As shown, by Figure 1 It can be seen that the obtained composite material is granular with a small number of microporous structures on the surface and a particle size between 5-10 μm.

[0124] 2. Button cell battery test The lithium-silicon amorphous carbon-coated graphite composite materials prepared in Examples 1-3 and the lithium-silicon amorphous carbon-coated graphite composite materials prepared in Comparative Examples 1-3 were assembled into coin cells according to the following methods: A binder, conductive agent, and solvent are added to the negative electrode material and stirred until homogeneous to form a negative electrode slurry. The negative electrode slurry is then coated onto copper foil, dried, rolled, and cut to obtain the negative electrode sheet. The binder is LA132 binder, the conductive agent is SP conductive agent, and the solvent is double-distilled water. The weight ratio of the negative electrode material, SP conductive agent, LA132 binder, and double-distilled water is 92:4:4:220. A lithium metal sheet is used as the counter electrode, polyethylene propylene (PEP) is used as the separator, and LiPF6 / EC+DEC (LiPF6 concentration is 1.1 mol / L, and the volume ratio of EC to DEC is 1:1) is used as the electrolyte. The battery is assembled in an argon-filled glove box.

[0125] The fabricated button cells were installed on a Wuhan Landian CT2001A battery tester and charged and discharged at a rate of 0.1C, with a charging and discharging voltage range of 0.005V to 2.0V. The initial discharge specific capacity and initial discharge efficiency were measured. The 2C rate discharge capacity was tested, and its rate performance (2C / 0.1C) and cycle performance (0.2C / 0.2C, 100 cycles) were calculated. The diffusion coefficient of the material was tested by GITT, and the OI value of the powder material was tested by XRD. The test results are shown in Table 1.

[0126] Table 1. As can be seen from Table 1, the lithium-silicon amorphous carbon-coated graphite composite materials prepared in Examples 1-3 have significantly higher discharge specific capacity, first efficiency and diffusion coefficient than those in Comparative Examples 1-3. The reason may be that the lithium-doped amorphous carbon coating on the surface of the materials in the examples reduces the defects of the materials and improves the lithium-ion diffusion coefficient. At the same time, the porous structure of the core reduces expansion and OI value and increases specific surface area.

[0127] 3. Soft-pack battery test The lithium-silicon amorphous carbon-coated graphite composite materials prepared in Examples 1-3 and Comparative Examples 1-3 were used as negative electrodes, and the ternary material (LiMn) was used as the negative electrode. 1 / 3 Co 1 / 3 Ni 1 / 3 A 2Ah pouch cell was prepared using O2 as the positive electrode, LiPF6 (solvent EC+DEC, volume ratio 1:1, concentration 1.1mol / L) as the electrolyte, and Celegard 2400 as the separator.

[0128] In the preparation of the negative electrode, a binder, a conductive agent, and a solvent are added to the negative electrode material and stirred to form a uniform negative electrode slurry. The negative electrode slurry is then coated onto copper foil, dried, rolled, and cut to obtain the negative electrode sheet. The binder is LA136D binder, the conductive agent is SP conductive agent, and the solvent is double-distilled water. The weight ratio of the negative electrode material, SP conductive agent, LA136D binder, and double-distilled water is 95:1:4:250.

[0129] In the preparation of the positive electrode, a binder solution is prepared, followed by the addition of a conductive agent and the positive electrode material. The mixture is stirred and stirred until homogeneous to form a positive electrode slurry. This slurry is then coated onto aluminum foil, dried, rolled, and cut to obtain the positive electrode sheet. The binder is PVDF, the conductive agent is SP, and the solvent is N-methylpyrrolidone. The weight ratio of the positive electrode material, conductive agent, binder, and solvent is 97:1:2:140.

[0130] Cyclic performance and rate testing: Cycle performance and rate testing were performed on the pouch cells of each embodiment and comparative example.

[0131] Cyclic performance test: charge / discharge voltage range of 2.8~4.2V, temperature of 25±3.0℃, charge / discharge rate of 0.5C / 1.0C, and number of cycles of 500.

[0132] Rate performance test: Charged at a 3C rate, the charging DCR impedance was tested at different SOCs (10%, 30%, 50%, 70%, 90%). The test results of cycle performance and rate performance are shown in Table 2.

[0133] Table 2. As shown in Table 2, the cycle performance and rate performance of the soft-pack lithium-ion batteries prepared using the composite electrode materials of the various embodiments of the present invention are better than those of the comparative examples. The reasons include: the composite electrode materials of the present invention have a lower OI value and a higher specific surface area, which can improve the liquid retention performance of the materials and improve the cycle performance; at the same time, the composite electrode materials of the embodiments have a lower powder resistivity, which can improve their kinetic performance, thereby improving their constant current ratio during charge and discharge, that is, improving their power performance.

[0134] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0135] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0136] It should be noted that the terms "and / or" or " / " used herein are merely descriptions of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. The singular forms "a," "described," and "the" used in the embodiments of the invention and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0137] In the detailed description and claims, a list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0138] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a negative electrode material, characterized in that, Includes the following steps: A first inorganic salt compound and a second inorganic salt compound are mixed and added to a first solvent to form a salt solution; etched graphite is added to the salt solution and mixed, and then dried to obtain an intermediate material; wherein, the first inorganic salt compound includes a molybdenum compound; The alkali, the first binder and the intermediate material are mixed and subjected to a first sintering to obtain porous graphite. A lithium compound, a second binder, and silane are mixed and added to a second solvent to form a mixture. The porous graphite is then dispersed in the mixture and subjected to a second sintering to obtain the negative electrode material.

2. The method for preparing the negative electrode material according to claim 1, characterized in that, Satisfying at least one of features (1) to (9): (1) The molybdenum compound includes at least one of molybdenum oxide, molybdenum sulfide, molybdenum chloride, and molybdenum nitrate; (2) The second inorganic salt compound includes at least one of nitrate, carbonate, and chloride; preferably, the second inorganic salt compound includes at least one of zinc chloride, zinc nitrate, potassium carbonate, and lithium carbonate; (3) The first solvent includes at least one of cyclohexane, petroleum ether, benzene, and n-hexane; (4) The second solvent includes an organic solvent, which includes at least one of cyclohexane, xylene, benzene, and butanediol; (5) The first adhesive includes at least one of petroleum asphalt, coal tar pitch, phenolic resin, and furfural resin; (6) The second binder includes asphalt, which includes at least one of petroleum asphalt, coal tar pitch, and natural asphalt; (7) The silane includes liquid silane, which includes at least one of methyltrimethoxysilane, phenyltrimethoxysilane, tris(dimethylamino)silane, and tetraethylsilane; (8) The lithium compound includes inorganic lithium compounds, preferably, the lithium compound includes at least one of lithium borate, lithium sulfonate, lithium phosphate, and lithium molybdate; (9) The alkali includes at least one of sodium hydroxide, potassium hydroxide and barium hydroxide.

3. The method for preparing the negative electrode material according to claim 1, characterized in that, It satisfies at least one of the following features (1) to (5): (1) The mass ratio of the first inorganic salt compound to the second inorganic salt compound is 1:(0.5~2); (2) The mass ratio of the first inorganic salt compound, the second inorganic salt compound and the etched graphite is (1~5):(1~5):100; (3) The mass ratio of the alkali, the first binder and the intermediate material is (100~500) (5~10):100; (4) The mass ratio of the lithium compound, the second binder, the silane and the porous graphite is (1~5):(1~5):(1~5):100; (5) The mass concentration of the salt solution is 1wt%~10wt%.

4. The method for preparing the negative electrode material according to claim 1, characterized in that, The first sintering includes: sintering at a first temperature in an inert gas atmosphere, followed by sintering with CO2 at a second temperature; The first temperature range is 1200℃~1350℃, and the sintering time is 1h~6h; the second temperature range is 950℃~1100℃, the sintering time is 30min~300min, and the CO2 flow rate is 10mL / min~100mL / min. And / or, the sintering temperature of the second sintering is 1100℃~1300℃, and the sintering time is 1 h~3 h; And / or, the drying method is spray drying, wherein the inlet temperature is 200°C and the outlet temperature is 100°C during the spray drying process.

5. The method for preparing the negative electrode material according to claim 1, characterized in that, The etched graphite is obtained by laser etching of graphite; In the laser etching process, the wavelength of the laser is 150nm~1500nm; and / or, the scanning rate of the laser is 0.1cm / s~100cm / s; And / or, the atmosphere for laser etching is at least one of vacuum, nitrogen, or oxygen; and / or, the laser etching time is 60s to 600s.

6. A negative electrode material, characterized in that, include: The negative electrode material prepared by the method of any one of claims 1 to 5.

7. The negative electrode material according to claim 6, characterized in that, The negative electrode material includes active particles and a carbon coating layer covering at least a portion of the surface of the active particles. The active particles include porous graphite, and the carbon coating layer contains at least silicon and lithium elements with a content not equal to 0. And / or, the particle size of the negative electrode material is 5μm~10μm.

8. A negative electrode sheet, characterized in that, include: A current collector, and a coating on at least a portion of the surface of at least one side of the current collector in the thickness direction; The coating comprises the negative electrode material prepared by the method of any one of claims 1 to 5; And / or, the negative electrode material as described in claim 6 or 7.

9. A battery, characterized in that, include: The negative electrode material prepared by the method of any one of claims 1 to 5; And / or, the negative electrode material according to claim 7 or 8; and / or, the negative electrode sheet according to claim 8.

10. An electrical appliance, characterized in that, include: The negative electrode sheet as described in claim 8; And / or, the battery of claim 9.

Images