Graphite negative electrode, preparation method therefor, and use thereof

Abstract

The present application relates to, but is not limited to, the technical field of secondary batteries, and discloses a graphite negative electrode, a preparation method therefor, and a use thereof. The graphite negative electrode comprises an active substance, the active substance comprising at least two of graphite component 1, graphite component 2, graphite component 3, and graphite component 4, and not comprising only graphite component 1 and graphite component 4 at the same time. Graphite component 1 and graphite component 2 each have a secondary-particle structure, graphite component 1 is a secondary particle that has undergone spheroidization, and graphite component 2 comprises a coating layer. Graphite component 3 and graphite component 4 each have a single-particle structure, graphite component 3 comprises a coating layer, and graphite component 4 does not comprise a coating layer. The graphite negative electrode has high specific capacity and compaction density, as well as good cycling performance, and can also well solve the problems of lithium precipitation and the capacity recovery rate after high-temperature storage (for example, the capacity recovery rate after storage at 60°C for 84 days exceeds 89%, or even exceeds 90%).

Description

A graphite anode, its preparation method and application

[0001] This application claims priority to Chinese Patent Application No. 202411619167.6, filed on November 13, 2024, entitled "A Graphite Anode and Its Preparation Method and Application", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to, but is not limited to, the field of secondary battery technology, and in particular to a graphite anode, its preparation method, and its application. Background Technology

[0003] While traditional lithium-ion batteries are widely used in the market, further improvements in their energy density and power density face numerous challenges, including issues with electrode material stability, electrolyte window limitations, and electrode structure design. Graphite, as a traditional choice for lithium-ion battery anode materials, possesses advantages such as high electronic conductivity, a large lithium-ion diffusion coefficient, stable layered structure, and low lithium intercalation potential, making it one of the most widely used and technologically mature anode materials in commercial applications. However, with the continuous increase in the performance requirements of lithium-ion batteries, traditional graphite anode materials are gradually showing limitations in specific capacity and compaction density, cycle performance, lithium plating, and capacity recovery rate after high-temperature storage (high-temperature performance).

[0004] Therefore, there is an urgent need to develop a high-capacity, high-density graphite anode material, which will significantly improve the energy density and cycle life of lithium-ion batteries, providing more efficient and reliable energy solutions for electric vehicles, portable electronic devices, and large-scale energy storage systems. In one alternative implementation, achieving high capacity and high density of graphite anode materials to improve the fast-charging capability of lithium-ion batteries comes at the cost of energy density. Furthermore, the resulting graphite anode suffers from technical problems such as poor cycle performance, lithium plating, and poor capacity recovery rate after high-temperature storage (high-temperature performance).

[0005] Therefore, there is an urgent need to provide a new graphite anode that can solve the problems of specific capacity, compaction density, cycle performance, lithium plating, and capacity recovery rate after high-temperature storage (high-temperature performance) without sacrificing energy density. Summary of the Invention

[0006] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0007] This application proposes a graphite anode, its preparation method, and its application. The graphite anode has high specific capacity and compaction density, as well as good cycle performance, and can effectively solve the problems of lithium plating and capacity recovery rate after high-temperature storage (high-temperature performance).

[0008] This application also proposes a graphite anode.

[0009] This application also proposes a method for preparing a graphite anode.

[0010] This application also proposes a graphite negative electrode sheet.

[0011] This application also proposes a method for preparing a graphite negative electrode sheet.

[0012] This application also proposes the application of the above-mentioned graphite anode.

[0013] According to one aspect of this application, a graphite anode is provided, comprising an active material, said active material comprising at least two of graphite component 1, graphite component 2, graphite component 3, and graphite component 4, and not simultaneously comprising only graphite component 1 and graphite component 4.

[0014] Both graphite component 1 and graphite component 2 have a secondary particle structure, and graphite component 1 is a secondary particle that has undergone spheroidization treatment, while graphite component 2 contains a coating layer.

[0015] Both graphite component 3 and graphite component 4 have a single-particle structure, and graphite component 3 contains a coating layer while graphite component 4 does not contain a coating layer.

[0016] In some embodiments of this application, the graphite component 1 accounts for 0% to 30% of the mass of the active material; and / or, the graphite component 2 accounts for 0% to 70% of the mass of the active material; and / or, the graphite component 3 accounts for 0% to 70% of the mass of the active material; and / or, the graphite component 4 accounts for 0% to 30% of the mass of the active material; and / or, the particle size D of the graphite component 1... 50 The particle size D of the graphite component 2 is between 11.5 μm and 14 μm; and / or the particle size D of the graphite component 2 is between 11.5 μm and 14 μm. 50 Between 13 μm and 15 μm; and / or, the particle size D of the graphite component 3. 50 The particle size D of the graphite component 4 is between 9 μm and 13 μm; and / or the particle size D of the graphite component 4 is between 9 μm and 13 μm. 50 Between 8μm and 11μm.

[0017] According to an optional embodiment of this application, at least the following beneficial effects are achieved: the graphite anode of this application includes an active material, which comprises at least two of four different graphite components, and the content and particle size D of each graphite component are specified. 50The specific selection of graphite anodes in this application results in high specific capacity and compaction density, as well as good cycle performance. It can also effectively solve the problems of lithium plating and capacity recovery rate after high-temperature storage (e.g., capacity recovery rate of more than 89% or even more than 90% after storage at 60°C for 84 days).

[0018] The graphite anode described in this application balances the contradictory relationship between graphite anode kinetics (cycle performance) and energy density by adjusting the amount and particle size of each different graphite component in the active material. Graphite component 1 is introduced to balance high-temperature performance and kinetic performance. In graphite component 2, coating agent technology is used to reduce the coating amount, which effectively improves the kinetic performance of the active material on the one hand, and ensures that the high-temperature performance and cycle life of the active material do not deteriorate on the other hand. Graphite components 3 and 4 with single-particle structures respectively improve the capacity and compaction density of the active material, reduce costs, and help ensure high-temperature performance, thereby achieving good kinetic characteristics of the battery even under high capacity and high compaction conditions.

[0019] This application designs a multi-component graphite anode, utilizing the different advantages and characteristics of each graphite component to balance the kinetics and energy density of the anode sheet; the two secondary particle components, graphite component 1 and graphite component 2, can be regarded as kinetic performance switches, and the fast charging performance can be quantitatively controlled by adjusting their proportion; the two single particle components, graphite component 3 and graphite component 4, serve as the cornerstone of the graphite anode capacity and compaction density, ensuring the energy density and high-temperature performance of the graphite anode.

[0020] In some embodiments of this application, the particle sizes of graphite component 1, graphite component 2, graphite component 3, and graphite component 4 are different from each other. This helps to reduce the voids in the active material, thereby increasing the compaction density.

[0021] In some embodiments of this application, the active material comprises graphite component 2, graphite component 3, and graphite component 4. The active material formed by combining these three graphite components exhibits better cycle performance and high-temperature performance compared to active materials formed by combining other two or three graphite components.

[0022] In some embodiments of this application, the coating layer in the graphite component 1 is composed of soft carbon. The raw material for preparing the soft carbon coating layer of the graphite component 1 is conventional pitch.

[0023] In some embodiments of this application, the graphite component 1 accounts for 0% to 30% of the mass of the active material. Optionally, the graphite component 1 accounts for 10% to 25% of the mass of the active material. Specifically, for example, it is 10%, 15%, 20%, or 25%.

[0024] In some embodiments of this application, the particle size D of the graphite component 1 50 Optionally, the particle size D of the graphite component 1 is between 11.5 μm and 14 μm. 50 Optionally, the particle size D of the graphite component 1 is between 12 μm and 14 μm. 50 Between 12.5μm and 13.5μm. Specifically, for example, 12μm, 12.5μm, 13μm, 13.5μm, and 14μm.

[0025] In some embodiments of this application, the graphite component 2 accounts for 0% to 70% of the mass of the active material. Optionally, the graphite component 2 accounts for 15% to 60% of the mass of the active material. Alternatively, the graphite component 2 accounts for 40% to 60% of the mass of the active material. Specifically, for example, it is 15%, 20%, 30%, 40%, 50%, or 60%.

[0026] In some embodiments of this application, the particle size D of the graphite component 2 50 Optionally, the particle size D of the graphite component 2 is between 13 μm and 15 μm. 50 Optionally, the particle size D of the graphite component 2 is between 13 μm and 14.5 μm. 50 Between 13.5μm and 14.5μm. Specifically, for example, 13μm, 13.5μm, 14μm, and 14.5μm.

[0027] In some embodiments of this application, the graphite component 3 accounts for 0% to 70% of the mass of the active material. Optionally, the graphite component 3 accounts for 10% to 60% of the mass of the active material. Alternatively, the graphite component 3 accounts for 10% to 20% of the mass of the active material. Specifically, for example, it is 10%, 20%, 30%, 40%, 50%, or 60%.

[0028] In some embodiments of this application, the particle size D of the graphite component 3 50 Optionally, the particle size D of the graphite component 3 is between 9 μm and 13 μm. 50 Optionally, the particle size D of the graphite component 3 is between 9.5 μm and 12.5 μm. 50 Between 10μm and 12μm. Specifically, for example, 9.5μm, 10μm, 11μm, and 12μm.

[0029] In some embodiments of this application, the graphite component 4 accounts for 0% to 30% of the mass of the active material. Optionally, the graphite component 4 accounts for 10% to 30% of the mass of the active material. Alternatively, the graphite component 4 accounts for 10% to 20% of the mass of the active material. Specifically, for example, it is 10%, 15%, 20%, 25%, or 30%.

[0030] In some embodiments of this application, the particle size D of the graphite component 4 50 Optionally, the particle size D of the graphite component 4 is between 8 μm and 11 μm. 50 Optionally, the particle size D of the graphite component 4 is between 9 μm and 11 μm. 50 Between 9.5μm and 10.5μm. Specifically, for example, 9μm, 9.5μm, 10μm, and 10.5μm.

[0031] In some embodiments of this application, both graphite component 1 and graphite component 2 contain a coating layer, and the mass percentage of the coating layer in graphite component 1 is greater than the mass percentage of the coating layer in graphite component 2.

[0032] In some embodiments of this application, the graphite component 1 includes a coating layer, which accounts for 1.2% to 2% of the mass of the graphite component 1. Optionally, the coating layer accounts for 1.5% to 2% of the mass of the graphite component 1. The mass percentage of this coating layer is also referred to as the residual carbon value, i.e., the residual carbon value is 1.2% to 2%.

[0033] In some embodiments of this application, the coating layer in the graphite component 2 accounts for 0.2% to 1.5% of the mass of the graphite component 2. Optionally, the coating layer in the graphite component 2 accounts for 0.5% to 1% of the mass of the graphite component 2.

[0034] In some embodiments of this application, the coating layer in the graphite component 2 is composed of hard carbon, soft carbon, graphene, solid electrolyte, or carbon nanotubes.

[0035] The raw materials for preparing the hard carbon coating layer of graphite component 2 are at least one of cross-linked pitch, resin, and biomass carbon source. Examples of biomass carbon sources include corn stalks, soybean stalks, and wheat stalks; examples of resins include polycarbonate resin and epoxy resin.

[0036] In some embodiments of this application, the coating layer of the graphite component 3 is a conductive coating layer.

[0037] In some embodiments of this application, the composition of the conductive coating layer of the graphite component 3 is selected from at least one of graphene, carbon nanofibers, and MXene (MXene is a two-dimensional material made of transition metal carbides or nitrides).

[0038] According to another aspect of this application, a method for preparing the above-mentioned graphite anode is proposed, comprising the following steps:

[0039] The graphite component 1, the graphite component 2, the graphite component 3, and the graphite component 4 are mixed to obtain the graphite negative electrode.

[0040] In some embodiments of this application, the raw material for the graphite component 1 includes petroleum coke, such as raw petroleum coke or calcined petroleum coke.

[0041] In some embodiments of this application, the sulfur content in the petroleum coke is less than or equal to 1.5% by mass. This relatively low impurity content helps maintain the electrochemical performance of the graphite anode.

[0042] In some embodiments of this application, the preparation process of the graphite component 1 includes: spheroidizing petroleum coke, then graphitizing it, adding asphalt, granulating it, and obtaining the graphite component 1.

[0043] In some embodiments of this application, when the raw material is raw petroleum coke, the raw petroleum coke can be heat-treated before spheroidization.

[0044] In some embodiments of this application, the heat treatment temperature is 400°C to 700°C, and optionally, the heat treatment temperature is 450°C to 650°C.

[0045] In some embodiments of this application, the heat treatment time is 1 to 2 hours, and optionally, the heat treatment time is 1.5 to 1.8 hours.

[0046] In some embodiments of this application, the graphitization treatment temperature is 2800°C to 3500°C, and optionally, the graphitization treatment temperature is 2900°C to 3200°C.

[0047] In some embodiments of this application, the graphitization process takes 2 to 12 hours, and optionally, it takes 3 to 10 hours.

[0048] In some embodiments of this application, the amount of asphalt added is 1% to 5% of the mass of petroleum coke, and optionally, the amount of asphalt added is 1.5% to 2.5% of the mass of petroleum coke.

[0049] In some embodiments of this application, the granulation temperature is 700°C to 800°C, and optionally, the granulation temperature is 750°C to 780°C.

[0050] In some embodiments of this application, the granulation time is from 30 minutes to 5 hours, and optionally, the granulation time is from 1.5 hours to 4.5 hours. Granulation can obtain graphite components with secondary particle structure characteristics.

[0051] In some embodiments of this application, the preparation process of the graphite component 1 includes: heat-treating raw petroleum coke at a temperature of 400°C to 700°C for 1 to 2 hours, then performing spheroidization treatment, followed by graphitization treatment at a temperature of 2800°C to 3500°C for 2 to 12 hours, adding asphalt, granulating at a temperature of 700°C to 800°C for 30 minutes to 5 hours, to obtain the graphite component 1.

[0052] In some embodiments of this application, the raw material for the graphite component 2 includes needle coke, such as raw needle coke or calcined needle coke.

[0053] In some embodiments of this application, the preparation process of the graphite component 2 includes: granulating needle coke, then graphitizing it, and then coating it to obtain the graphite component 2.

[0054] In some embodiments of this application, the coating process includes at least one of soft carbon liquid phase coating, hard carbon liquid phase coating, solid electrolyte coating, graphene coating, or carbon nanotube coating.

[0055] In some embodiments of this application, the coating process employs conventional solid-phase coating or liquid-phase coating processes.

[0056] In some embodiments of this application, during the coating process, at least one of asphalt, resin, biomass carbon source, solid electrolyte, graphene or carbon nanotubes may be added, with the amount added being 0.5% to 5.5% of the mass of needle coke. Optionally, the amount added is 0.5% to 5% of the mass of needle coke.

[0057] In some embodiments of this application, the granulation and graphitization processes in the preparation of graphite component 2 are the same as those in the preparation of graphite component 1.

[0058] In some embodiments of this application, the raw material for the graphite component 3 includes at least one of petroleum coke or needle coke. For example, it is one of raw petroleum coke, calcined petroleum coke, raw needle coke, and calcined needle coke.

[0059] In some embodiments of this application, the preparation process of the graphite component 3 includes: graphitizing petroleum coke or needle coke, then adding asphalt and conductive materials, mixing, and heating to obtain the graphite component 3.

[0060] In some embodiments of this application, when the raw material is raw petroleum coke, the raw petroleum coke can be heat-treated before graphitization. When the raw material is calcined petroleum coke, raw needle coke, or calcined needle coke, no heat treatment is required.

[0061] In some embodiments of this application, the mass of the asphalt accounts for 0.1% to 6% of the mass of the petroleum coke or needle coke; alternatively, the mass of the asphalt accounts for 0.1% to 5% of the mass of the petroleum coke or needle coke. Adding a small amount of asphalt helps the conductive material to uniformly coat the petroleum coke or needle coke.

[0062] In some embodiments of this application, the conductive material accounts for 0.5% to 3% of the mass of the petroleum coke or needle coke. Optionally, the conductive material accounts for 0.5% to 2% of the mass of the petroleum coke or needle coke.

[0063] In some embodiments of this application, the temperature of the mixture of asphalt and conductive material is 900°C to 1300°C, and the heating time is 30 minutes to 5 hours.

[0064] In some embodiments of this application, the heat treatment and graphitization processes in the preparation of graphite component 3 are the same as those in the preparation of graphite component 1.

[0065] In some embodiments of this application, the raw material for the graphite component 4 includes petroleum coke. For example, it may be at least one of raw petroleum coke or calcined petroleum coke.

[0066] In some embodiments of this application, the preparation process of the graphite component 4 includes: spheroidizing petroleum coke and then graphitizing it to obtain the graphite component 4. The preparation process of the graphite component 4 does not involve granulation or coating.

[0067] In some embodiments of this application, when the raw material is raw petroleum coke, the raw petroleum coke can be heat-treated before spheroidization.

[0068] In some embodiments of this application, the heat treatment and graphitization processes in the preparation of graphite component 4 are the same as those in the preparation of graphite component 1.

[0069] According to an optional embodiment of this application, at least the following beneficial effects are achieved: This application optimizes the interaction and influence of each graphite component through different designs for each graphite component; in graphite component 1, the kinetics and high-temperature performance are adjusted to a balanced state through spheroidization treatment; in graphite component 2, the stability of the graphite anode is further improved by coating technology, which reduces the coating amount without damaging the kinetics; the surface of graphite component 3 is coated with a conductive coating layer that increases compaction density and reduces charge transfer impedance, providing a basis for the use of graphite anode under high compaction; graphite component 4 uses petroleum coke as raw material, which can not only improve the processing performance of graphite anode, but also significantly reduce the raw material cost of graphite electrode sheets.

[0070] According to another aspect of this application, a graphite negative electrode sheet is provided, the components of which include the above-mentioned graphite negative electrode, current collector and additives.

[0071] According to an optional embodiment of this application, at least the following beneficial effects are achieved: the graphite negative electrode sheet described in this application has high specific capacity and compaction density, as well as good cycle performance, and can also effectively solve the problems of lithium plating and capacity recovery rate after high-temperature storage (e.g., capacity recovery rate exceeding 89% or even exceeding 90% after 84 days of storage at 60°C).

[0072] In some embodiments of this application, the current collector includes copper foil and aluminum foil.

[0073] The graphite negative electrode sheet according to an optional embodiment of this application has at least the following beneficial effects: the compaction density of the graphite negative electrode sheet of this application is not less than 1.74 g / cc, and optionally, the compaction density of the graphite negative electrode sheet exceeds 1.80 g / cc.

[0074] In some embodiments of this application, the additives include at least one of conductive agents, binders, and dispersants.

[0075] In some embodiments of this application, the additives simultaneously include conductive agents, binders, and dispersants. In the graphite negative electrode sheet, the mass ratio of graphite negative electrode, conductive agent, binder, and dispersant is 96:(1-4):(0.5-2):(0.5-2). Optionally, the mass ratio of graphite negative electrode, conductive agent, binder, and dispersant is 96:(2-2.5):(0.8-1.2):(0.5-1.2).

[0076] In some embodiments of this application, the conductive agent may be a conventional conductive agent, such as conductive carbon black SP, acetylene black, Ketjen black, conductive graphite (such as KS-6, KS-15, SFG-6, SFG-15 or Ks-6), carbon fiber or carbon nanotube.

[0077] Conductive agents are added during electrode fabrication to ensure good charge-discharge performance. These conductive materials collect microcurrents between active materials and between the active materials and the current collector (e.g., copper foil), reducing electrode contact resistance and accelerating electron movement. They also effectively increase the migration rate of lithium ions within the electrode material, thereby improving charge-discharge efficiency. Conventional conductive agents used in this field can be added in standard amounts; no restrictive provisions are made.

[0078] In some embodiments of this application, the adhesive may be a conventional adhesive. Optionally, the adhesive may be a fluoropolymer and / or synthetic rubber. Optionally, the adhesive may be one or a combination of at least two of the following: polyvinylidene fluoride, polyvinylidene fluoride (PVDF), polytetrafluoroethylene, styrene-butadiene rubber (SBR), fluoropolymers, or ethylene propylene diene rubber.

[0079] The adhesives include: combinations of polyvinylidene fluoride and polyvinylidene fluoride, combinations of polytetrafluoroethylene and styrene-butadiene rubber, combinations of styrene-butadiene rubber, fluorinated rubber and ethylene propylene diene rubber, combinations of polytetrafluoroethylene, styrene-butadiene rubber and fluorinated rubber, combinations of polyvinylidene fluoride, polyvinylidene fluoride, polytetrafluoroethylene and styrene-butadiene rubber, combinations of polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber, fluorinated rubber and ethylene propylene diene rubber, etc.

[0080] In some embodiments of this application, the dispersant may be a conventional dispersant, such as sodium carboxymethyl cellulose (CMC-Na).

[0081] In some embodiments of this application, the additive further includes a solvent, such as deionized water.

[0082] In some embodiments of this application, the compaction density of the graphite negative electrode sheet exceeds 1.65 g / cc, for example, from 1.7 g / cc to 1.8 g / cc. The ultimate compaction density of the graphite negative electrode sheet is, for example, from 1.74 g / cc to 1.82 g / cc.

[0083] According to another aspect of this application, a method for preparing a graphite negative electrode sheet is proposed, comprising the following steps:

[0084] The graphite anode is mixed with an additive, the resulting mixture is coated onto a current collector, dried, and pressed to obtain the graphite anode sheet.

[0085] In some embodiments of this application, the coating amount on the current collector is 80 g / m³. 2 Up to 120g / m 2 Optionally, the coating amount on the current collector is 100 g / m³. 2Up to 110g / m 2 .

[0086] In some embodiments of this application, the solid content of the mixture is 40% to 50%, and optionally, the solid content of the mixture is 43% to 50%.

[0087] In some embodiments of this application, after the pressing is completed, a cutting operation is also included. Cutting can obtain a graphite negative electrode sheet of a specific size.

[0088] According to another aspect of this application, a secondary battery is proposed, comprising the aforementioned graphite negative electrode sheet.

[0089] The secondary battery according to an optional embodiment of this application has at least the following beneficial effects: the secondary battery described in this application has good cycle performance and can also effectively solve the problems of lithium plating and capacity recovery rate after high-temperature storage (e.g., the capacity recovery rate after 84 days of storage at 60°C exceeds 89%, or even exceeds 90%).

[0090] In some embodiments of this application, the secondary battery is a lithium-ion battery.

[0091] In some embodiments of this application, the secondary battery further includes a positive electrode sheet, the raw materials for which the positive electrode sheet is prepared include a positive electrode active material, which is a conventional positive electrode active material, such as lithium iron phosphate or nickel-cobalt-manganese type positive electrode active materials.

[0092] In some embodiments of this application, the raw materials for preparing the positive electrode sheet also include conductive agents and binders. These are all conventional conductive agents and binders in the art.

[0093] In some embodiments of this application, the secondary battery further includes an electrolyte comprising a lithium salt.

[0094] In some embodiments of this application, the lithium salt may be at least one of LiPF6, LiBF4, and LiTFSI. Any conventional lithium salt may be used. No particular limitation is made.

[0095] In some embodiments of this application, the solvent of the electrolyte includes one or more of propylene carbonate, ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, N,N-dimethylacetamide, fluoroethylene carbonate, methyl propionate, ethyl propionate, ethyl acetate, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, dimethoxymethane, 1,2-dimethoxypropane, triethylene glycol dimethyl ether, dimethyl sulfone, dimethyl ether, vinyl sulfite, propylene sulfite, dimethyl sulfite, diethyl sulfite, or crown ether (12-crown-4).

[0096] In some embodiments of this application, the solvent is a mixture of ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC).

[0097] In some embodiments of this application, the volume ratio of EC, DEC and EMC in the solvent is (32-46):(25-36):30.

[0098] In some embodiments of this application, the electrolyte further contains additives; the mass fraction of the additives in the electrolyte is 0.1% to 18%, optionally, the mass fraction of the additives in the electrolyte is 6% to 12%. Typical but non-limiting mass fractions of the additives in the electrolyte are 0.5%, 1.5%, 2.5%, 3.5%, 4.5%, 5.5%, 6.5%, 7.5%, 8.5%, 9.5%, 10.5%, and 12%.

[0099] Understandably, there are no particular restrictions on electrolyte additives, and conventional electrolyte additives can be used.

[0100] Adding one or more additives to the electrolyte can further improve one or more properties of a secondary battery. Based on their function, additives include film-forming additives (such as carbon dioxide, sulfur dioxide, lithium carbonate, carbonates, thiolated organic solvents, halogenated organic film-forming additives, etc.), overcharge protection additives (with redox couples: ortho- and para-dimethoxy-substituted benzenes, polymerization increases internal resistance, blocking charging, such as biphenyl, cyclohexylbenzene, etc.), stabilizers, additives that improve high and low temperature performance, conductive additives, or flame retardant additives (organophosphorus compounds, organofluorine compounds, halogenated alkyl phosphates, etc.).

[0101] In some embodiments of this application, the additives include fluoroethylene carbonate (FEC), vinylene carbonate (VC), cyclohexylbenzene (CHB), ethylene carbonate, 1,3-propanesulfonate lactone (PS), 1,4-butanesulfonate lactone, vinyl sulfate, propylene sulfate, ethylene sulfate, vinyl sulfite, propylene sulfite, dimethyl sulfite, diethyl sulfite, ethylene sulfite, methyl chloroformate, succinic anhydride (SA), dimethyl sulfoxide, anisole, acetamide, diazabenzene, and m-diazabenzene. One or more of the following: benzene, 12-crown ether-4, 18-crown ether-6, 4-fluoroanisole, fluorochain ether, difluoromethyl vinyl carbonate, trifluoromethyl vinyl carbonate, chlorovinyl carbonate, bromovinyl carbonate, trifluoroethylphosphonic acid, bromobutyrolactone, fluoroacetic acid ethane, phosphate ester, phosphite ester, phosphazene, ethanolamine, dimethyl carbide, cyclobutyl sulfone, 1,3-dioxocyclopentane, acetonitrile, long-chain olefins, aluminum oxide, magnesium oxide, barium oxide, potassium carbonate, calcium carbonate, carbon dioxide, sulfur dioxide, or lithium carbonate.

[0102] The additives can be used alone or in combination of two or more of the above-mentioned additives.

[0103] In some embodiments of this application, the electrolyte contains vinylene carbonate (VC), 1,3-propanesulfonate lactone (PS), fluoroethylene carbonate (FEC), and cyclohexylbenzene (CHB).

[0104] In some embodiments of this application, the secondary battery further includes a separator. There are no particular limitations on the separator; any common separator in the art can be used. Examples include polyethylene (PE) separators, polypropylene (PP) separators, or PE / PP composite separators.

[0105] According to another aspect of this application, an electrical device is proposed, comprising the aforementioned secondary battery.

[0106] According to an optional embodiment of the present application, the electrical device has at least the following beneficial effects: the secondary battery of the present application has a high energy density, which can support higher energy output, and at the same time, it can maintain good working performance even in high temperature environments, meeting the needs of electric vehicles, smartphones and other electronic devices; the secondary battery of the present application has good thermal stability and chemical stability, reducing the risk of safety accidents during the use of the electrical device.

[0107] In some embodiments of this application, the electrical device is an electric vehicle. It can also be other electrical devices such as energy storage systems, power tools, drones, mobile devices such as wearable products, laptops, and mobile phones.

[0108] In some embodiments of this application, the electrical device is an electric car or an electric bicycle. It can also be other electric vehicles, such as electric motorcycles, electric scooters, electric wheelchairs, etc.

[0109] Other features and advantages of this application will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing this application.

[0110] After reading and understanding the accompanying diagrams and detailed descriptions, the other aspects can be understood. Attached Figure Description

[0111] The accompanying drawings are used to provide a further understanding of the technical solutions of this application and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of this application and do not constitute a limitation on the technical solutions of this application.

[0112] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0113] Figure 1 is a schematic diagram of the dispersion of graphite components on the current collector side of the graphite negative electrode sheet in Embodiment 1 of this application;

[0114] Figure 2 is a scanning electron microscope (SEM) image of the graphite negative electrode sheet of Embodiment 1 of this application.

[0115] Explanation of reference numerals in the attached figures: 1 represents graphite component 1; 2 represents graphite component 2; 3 represents graphite component 3; 4 represents graphite component 4; 5 represents current collector. Detailed Implementation

[0116] The following will clearly and completely describe the concept and technical effects of this application in conjunction with embodiments, so as to fully understand the purpose, features and effects of this application. Obviously, the described embodiments are only a part of the embodiments of this application, not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are all within the scope of protection of this application. Unless otherwise specified, the experimental methods used in the embodiments are conventional methods; the materials and reagents used, unless otherwise specified, are commercially available. Unless otherwise specified, the same parameter value is the same in each embodiment. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0117] In the description of this application, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. "Between a and b" includes the endpoint values ​​of a and b.

[0118] Example 1

[0119] A graphite anode includes an active material comprising graphite component 1, graphite component 2, graphite component 3, and graphite component 4.

[0120] Graphite component 1 accounts for 15% of the mass of the active material;

[0121] Graphite component 2 accounts for 50% of the mass of the active material;

[0122] Graphite component 3 accounts for 20% of the mass of the active material;

[0123] Graphite component 4 accounts for 15% of the mass of the active material;

[0124] Particle size D of graphite component 1 50 It is 13.4 μm;

[0125] Particle size D of graphite component 2 50 It is 14.3 μm;

[0126] Particle size D of graphite component 3 50 It is 10.7 μm;

[0127] Particle size D of graphite component 4 50 It is 9.8μm;

[0128] Graphite component 1 has a secondary particle structure. Graphite component 1 is a secondary particle that has undergone spheroidization treatment. Graphite component 1 contains a coating layer. The coating layer is composed of soft carbon and its mass is 1.5% of the mass of graphite component 1.

[0129] Graphite component 2 has a secondary particle structure and contains a coating layer composed of hard carbon. The mass of the coating layer is 0.5% of the mass of graphite component 2.

[0130] Both graphite components 3 and 4 have a single-particle structure. Graphite component 3 contains a coating layer, which consists of graphene, and the mass of graphene is 1% of the mass of graphite component 3. Graphite component 4 does not contain a coating layer.

[0131] The above-mentioned method for preparing the graphite anode includes the following steps:

[0132] Graphite component 1, graphite component 2, graphite component 3 and graphite component 4 are mixed to obtain a graphite anode;

[0133] The preparation process of graphite component 1 includes: heat-treating raw petroleum coke at a temperature of 500°C for 1 hour, then performing spheroidization treatment (spheroidization treatment is a conventional process in this field), followed by graphitization treatment at a temperature of 3000°C for 3 hours, adding asphalt (the mass of the asphalt is 7.5% of the mass of the raw petroleum coke), granulating at a temperature of 750°C for 2 hours, and obtaining graphite component 1;

[0134] The preparation process of graphite component 2 includes: granulating needle coke at a temperature of 750℃ for 2 hours, then graphitizing at a temperature of 3000℃ for 3 hours, then adding polycarbonate resin (the mass of polycarbonate resin is 5% of the mass of needle coke), and coating with conventional liquid phase coating process to obtain graphite component 2;

[0135] The preparation process of graphite component 3 includes: graphitizing petroleum coke after calcination at a temperature of 3000℃ for 3 hours; then adding asphalt (the mass of the asphalt is 5% of the mass of the petroleum coke after calcination, and the softening point temperature of the asphalt is 300℃) and a conductive material (the conductive material is graphene, and the mass of the graphene is 1.0% of the mass of the petroleum coke after calcination); heating to 350℃ and stirring; and then heating at a temperature of 1000℃ for 2 hours to obtain graphite component 3.

[0136] The preparation process of graphite component 4 includes: heat-treating raw petroleum coke at 550℃ for 1.5 hours, followed by spheroidization and graphitization at 3200℃ for 1.5 hours to obtain graphite component 4. The preparation process of graphite component 4 does not involve granulation or coating.

[0137] A graphite negative electrode sheet, the graphite negative electrode sheet comprising a graphite negative electrode, a current collector 5 (current collector 5 is copper foil), a conductive agent, a binder and a dispersant.

[0138] In the graphite negative electrode sheet, the mass ratio of graphite negative electrode, conductive agent, binder and dispersant is 96:2:1:1.

[0139] The conductive agent is conductive carbon black SP; the binder is styrene-butadiene rubber (SBR); and the dispersant is sodium carboxymethyl cellulose (CMC-Na).

[0140] The compaction density of the graphite negative electrode sheet is 1.70 g / cc. The ultimate compaction density of the graphite negative electrode sheet is verified by adjusting the parameters of the roller press during the rolling process.

[0141] A method for preparing a graphite negative electrode sheet includes the following steps:

[0142] A graphite anode was mixed with a conductive agent, a binder, a dispersant, and deionized water to obtain a mixture (the solid content of the mixture was 45%). The coating amount was 100 g / m². 2 The coating is applied to the upper and lower surfaces of copper foil, dried, and then rolled twice to obtain a graphite negative electrode sheet.

[0143] Figure 1 is a schematic diagram of the dispersion of graphite components on the current collector side of the graphite negative electrode sheet in Embodiment 1 of this application; as can be seen from Figure 1, the four graphite components in the active material are dispersed with each other.

[0144] Figure 2 is a scanning electron microscope (SEM) image of the graphite negative electrode sheet of Embodiment 1 of this application.

[0145] Assembling the above-mentioned graphite negative electrode sheet with a lithium sheet forms a half-cell, which is then used to test the specific capacity of the active material.

[0146] The above-mentioned graphite negative electrode sheet is assembled with a PP (polypropylene) separator, an electrolyte (0.1 mol / L LiPF6EC as solvent), and a lithium iron phosphate positive electrode to form a soft-pack full cell. The soft-pack full cell is used to test the cell's initial coulombic efficiency (first efficiency), capacity retention rate after 500 charge-discharge cycles in the 2C stage, degree of lithium plating after 50 charge-discharge cycles in the 3C stage, and capacity recovery rate after storage at 60°C for 84 days.

[0147] Examples 2 to 18 and Comparative Examples 1 to 11

[0148] The preparation process of the graphite anodes corresponding to Examples 2 to 18 and Comparative Examples 1 to 16 is similar to that of Example 1. The only differences are the content of each graphite component in the active material, the particle size of each graphite component, and the composition or mass ratio of the coating layer. The specific details are shown in Table 1 (for ease of comparison, Table 1 also lists the composition characteristics of the active material corresponding to Example 1. The characteristics of Examples 2 to 18 and Comparative Examples 1 to 16 not listed in Table 1 are the same as those of Example 1).

[0149] The specific capacity of the active material is tested as follows: the half-cell is tested under the conditions of 0.1C, charging cutoff voltage of 2V, and discharging cutoff voltage of 0.05V to obtain the specific capacity of the active material.

[0150] Ultimate compaction density of graphite negative electrode sheet: This is verified by adjusting the pressure of the rollers of the roller mill. The presence of bulging edges on the electrode surface is used to determine whether the pressure is too high. The compaction density of the electrode sheet that just does not show overpressure is the ultimate compaction density of the graphite negative electrode sheet.

[0151] The initial coulombic efficiency (SOC) of the battery cell is tested under the conditions of a charging cutoff voltage of 3.75V and a discharging cutoff voltage of 2V. The charging process is divided into two steps: first, charging to 50% SOC with a current of 0.05C, and then charging to 100% SOC with a current of 0.33C (100% SOC means fully charged). The discharging current is 0.33C.

[0152] The capacity retention rate after 500 charge-discharge cycles in the 2C stage and the degree of lithium plating after 50 charge-discharge cycles in the 3C stage were both tested under the conditions of a charging cutoff voltage of 3.75V and a discharging cutoff voltage of 2V.

[0153] The test process for the capacity recovery rate after 84 days of storage at 60℃ is as follows: the battery is charged to 3.75V at 0.33C at 25℃, stored in a 60℃ environment for 84 days, then discharged to 2V at 0.33C, then charged to 3.75V at 0.33C and discharged to 2V at 0.33C to obtain the recovered capacity C1. C1 divided by the initial capacity (the initial capacity is the capacity before high-temperature storage) is the capacity recovery rate after 84 days of storage at 60℃.

[0154] When the coating components of graphite component 1 and graphite component 2 in Table 1 are soft carbon, the raw material corresponding to the soft carbon is conventional bitumen. When the coating component of graphite component 2 is hard carbon, the raw material corresponding to the hard carbon is biomass raw material (such as corn straw powder).

[0155] Table 1 (0% in Table 1 indicates that the corresponding graphite component is not present)

[0156] The results of the active material specific capacity, the ultimate compaction density of the graphite negative electrode sheet, the cell's first efficiency, the capacity retention rate after 500 charge-discharge cycles in the 2C stage, the degree of lithium plating after 50 charge-discharge cycles in the 3C stage, and the capacity recovery rate after 84 days of storage at 60°C for Examples 1 to 18 and Comparative Examples 1 to 11 are shown in Table 2.

[0157] Table 2

[0158] The active material in the multi-component graphite negative electrode sheet proposed in this application is composed of different graphite components, each with different functions and effects. Graphite component 1 is made from raw petroleum coke or calcined petroleum coke, which undergoes spheroidization, graphitization, and granulation to form graphite with a secondary particle structure. The purpose of introducing graphite component 1 is to balance high-temperature performance and kinetic performance, utilizing the advantages of raw materials and secondary particle structure to maximize the intrinsic kinetic performance of the graphite material. Spheroidization removes high-activity sites such as end faces and edges of graphite particles to ensure high-temperature performance. In Examples 1, 2, Comparative Examples 1, and 5, the proportion of graphite component 1 was adjusted for verification. In Example 2, as the proportion of graphite component 1 decreased, the kinetic performance decreased significantly, and the capacity retention rate after 500 charge-discharge cycles in the 2C stage was lower than that in Example 1, accompanied by a slight degree of lithium plating. Furthermore, since the content of graphite components was changed in Comparative Examples 1 and 5, the kinetics of graphite component 1 itself could not be highlighted. Therefore, the capacity, compaction density, cycle retention rate and lithium plating in Comparative Examples 1 and 5 were all poor.

[0159] Graphite component 2 is made from needle-shaped raw coke or calcined needle-shaped coke, and is liquid-phase coated to obtain secondary particulate graphite with low residual carbon content (i.e., low coating layer content). The aim is to improve the compaction density and capacity of the graphite negative electrode sheet by utilizing the unique streamlined shape of the raw material, and to reduce residual carbon content while ensuring kinetic performance at 3C levels through coating technology. The content of graphite component 2 was adjusted in Examples 1, 4, 5, Comparative Example 2, and Comparative Example 6 to verify this. In Examples 4 and 5, the proportion of graphite component 2 was increased and decreased compared to Example 1, respectively. It was found that the kinetic performance improved with increasing the proportion of graphite component 2. When the proportion of graphite component 2 reached 50%, the kinetic requirements at 3C levels were met. Further increasing the proportion of graphite component 2 did not significantly improve kinetic performance and easily led to deterioration of high-temperature performance, resulting in unsatisfactory high-temperature storage performance. Comparative Examples 2 and 6 further demonstrated the problem of deteriorated high-temperature performance. Moreover, due to the influence of the secondary particulate structure of graphite component 2, the capacity and initial efficiency in Comparative Examples 2 and 6 were significantly lower than in Example 1.

[0160] Graphite component 3 is made from calcined petroleum coke as raw material, coated with graphene, carbon nanofibers, etc., to form large-particle graphite with a conductive coating layer that improves compaction density and reduces charge transfer resistance. The purpose is to improve the capacity and compaction density of the active material. In Examples 1, 5, 10, Comparative Example 3, and Comparative Example 7, the proportion of graphite component 3 was adjusted. In Examples 5 and 10, the proportion of graphite component 3 increased and decreased compared to Example 1, respectively. As the proportion of graphite component 3 increased, both capacity and compaction density improved. However, due to insufficient kinetic performance, the cycle retention rate and lithium plating were poor. When the proportion of graphite component 3 was low, the capacity and compaction density of the active material became the limiting point. Comparative Examples 3 and 7 further highlighted the characteristics of graphite component 3, which had insufficient kinetic performance but high capacity and compaction density.

[0161] Graphite component 4 uses petroleum coke as raw material to obtain single-particle structure graphite, which reduces costs and compensates for the insufficient kinetic properties of single-particle structure graphite. The poor high-temperature performance of petroleum coke is improved through spheroidization. Comparing Examples 1, 3, 4, and 8, it can be observed that as the proportion of graphite component 4 decreases, the capacity and high-temperature performance of the active material deteriorate. Similar to graphite component 3, excessively high proportions lead to deterioration in fast-charging performance, which becomes a limiting factor.

[0162] In the process of adjusting the proportion of each graphite component (Examples 1, 6 to 10), it can be found that by increasing or decreasing the proportion of a certain graphite component, the capacity and compaction density of the active material can be controlled. Graphite component 1 and graphite component 2 can be regarded as switches for adjusting kinetic performance, while graphite component 3 and graphite component 4 can be regarded as switches for capacity and compaction density.

[0163] Furthermore, in Examples 11 to 18 and Comparative Examples 9 to 11, by adjusting the particle size and coating composition of each graphite component, it was found that the particle size of each graphite component has a significant impact on the cell's capacity, compaction density, and first-time efficiency. This is because changes in the graphite particle size lead to changes in the partial structure of the particles on the electrode surface, resulting in an increase or decrease in pore structure, thereby causing changes in compaction density and first-time efficiency. Simultaneously, the particle size itself has a crucial influence on kinetic performance; as the particle size increases, the kinetic performance gradually weakens. In Examples 13 to 15, by changing the coating composition, the surface coating of each graphite component was altered, and satisfactory electrochemical performance was observed when the proportions and particle sizes were appropriate.

[0164] In summary, by using a variety of different graphite components in combination, and by adjusting the particle size and proportion of the graphite components in the active material, this application enables the graphite anode and graphite anode sheet obtained to have excellent electrical properties.

[0165] The embodiments of this application have been described in detail above, but this application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this application.

Claims

1. A graphite anode comprising an active material, wherein the active material comprises at least two of graphite component 1, graphite component 2, graphite component 3, and graphite component 4, and not simultaneously comprises only graphite component 1 and graphite component 4. Both graphite component 1 and graphite component 2 have a secondary particle structure, and graphite component 1 is a secondary particle that has undergone spheroidization treatment, while graphite component 2 contains a coating layer. Both graphite component 3 and graphite component 4 have a single-particle structure, and graphite component 3 contains a coating layer while graphite component 4 does not contain a coating layer.

2. The graphite negative electrode according to claim 1, wherein The graphite component 1 comprises 0% to 30% of the active material by mass; and / or, the graphite component 2 comprises 0% to 70% of the active material by mass; and / or, the graphite component 3 comprises 0% to 70% of the active material by mass; and / or, the graphite component 4 comprises 0% to 30% of the active material by mass; and / or, the particle size D of the graphite component 1... 50 The particle size D of the graphite component 2 is between 11.5 μm and 14 μm; and / or the particle size D of the graphite component 2 is between 11.5 μm and 14 μm. 50 Between 13 μm and 15 μm; and / or, the particle size D of the graphite component 3. 50 The particle size D of the graphite component 4 is between 9 μm and 13 μm; and / or the particle size D of the graphite component 4 is between 9 μm and 13 μm. 50 Between 8μm and 11μm.

3. The graphite negative electrode according to claim 1 or 2, wherein The active material comprises graphite component 2, graphite component 3 and graphite component 4; And / or, the graphite component 2 accounts for 15% to 60% of the mass of the active material; and / or the particle size D of the graphite component 2 is between 13 μm and 14.5 μm 50 between 13 μm and 14.5 μm; And / or, the graphite component 3 accounts for 10% to 60% of the mass of the active material; and / or the particle size D of the graphite component 3 is between 9.5 μm and 12.5 μm 50 between 9.5 μm and 12.5 μm; And / or, the graphite component 4 accounts for 10% to 30% of the mass of the active material; and / or the particle size D of the graphite component 4 is between 9 μm and 11 μm. 50 between 9 μm and 11 μm.

4. The graphite negative electrode according to any one of claims 1 to 3, wherein, The graphite component 1 accounts for 10% to 25% of the mass of the active material; and / or the particle size D of the graphite component 1 is between 12 μm and 14 μm. 50 between 12 μm and 14 μm; And / or, the graphite component 1 contains a coating layer, the coating layer accounting for 1.2% to 2% of the mass of the graphite component 1; And / or, the coating layer in the graphite component 2 accounts for 0.2% to 1.5% of the mass of the graphite component 2; And / or, the coating layer of the graphite component 3 is a conductive coating layer.

5. A method for preparing a graphite anode as described in any one of claims 1 to 4, comprising the following steps: The graphite component 1, the graphite component 2, the graphite component 3, and the graphite component 4 are mixed to obtain the graphite negative electrode.

6. The production method according to claim 5, wherein The raw materials for graphite component 1 include petroleum coke; And / or, the raw material for the graphite component 2 includes needle coke; And / or, the raw material for the graphite component 3 includes at least one of petroleum coke or needle coke; And / or, the raw material for the graphite component 4 includes petroleum coke.

7. The production method according to claim 5 or 6, wherein The preparation process of the graphite component 1 includes: spheroidizing petroleum coke, then graphitizing it, adding asphalt, granulating it, and obtaining the graphite component 1. And / or, the preparation process of the graphite component 2 includes: granulating needle coke, then graphitizing it, and then coating it to obtain the graphite component 2; the coating process is at least one of the following after graphitization: soft carbon liquid phase coating, hard carbon liquid phase coating, solid electrolyte coating, graphene coating, and carbon nanotube coating. And / or, the preparation process of the graphite component 3 includes: graphitizing petroleum coke or needle coke, then adding asphalt and conductive materials, mixing, and heating to obtain the graphite component 3; And / or, the preparation process of the graphite component 4 includes: spheroidizing petroleum coke and then graphitizing it to obtain the graphite component 4.

8. A graphite negative electrode sheet, wherein the graphite negative electrode sheet comprises the graphite negative electrode, current collector, and additives as described in any one of claims 1 to 4.

9. A secondary battery comprising the graphite negative electrode sheet as described in claim 8.

10. An electrical device comprising the secondary battery as described in claim 9.

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