Composite negative electrode material, preparation method therefor and use thereof

Abstract

Provided in the embodiments of the present application are a composite negative electrode material, a preparation method therefor and the use thereof. The composite negative electrode material comprises an inner core and a composite coating layer, wherein the inner core comprises one of a silicon-based material, a tin-based material and a phosphorus-based material, and the composite coating layer comprises a fast electron conductor material and a fast ion conductor material, the fast electron conductor material coating part of the surface of the inner core, and the fast ion conductor material covering the surface of the inner core not covered by the fast electron conductor material. The composite coating layer can achieve full coverage on the surface of the inner core, and has good electronic / ionic conductivity at the same time, such that the composite negative electrode material has high cycle stability and good rate performance.

Description

Composite anode materials, their preparation methods and applications

[0001] This application claims priority to Chinese Patent Application No. 202411935090.3, filed on December 24, 2024, with the China National Intellectual Property Administration and entitled “Composite Anode Material and Preparation Method Thereof and Application”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of lithium battery anode technology, specifically to a composite anode material, its preparation method, and its application. Background Technology

[0003] Compared to commercial graphite anode materials, silicon-based and phosphorus-based materials have higher theoretical specific capacities and are considered ideal anode materials for developing lithium-ion batteries with higher energy densities. However, the dramatic volume expansion and low conductivity of silicon-based and phosphorus-based anode materials during lithium intercalation severely affect their structural stability and kinetic performance, thereby impacting the cycle life and rate performance of lithium-ion batteries.

[0004] To address the aforementioned issues with silicon-based and phosphorus-based materials, a common industry practice is to construct a carbon coating layer on the surface of these anode materials. While carbon coating improves the electronic conductivity to some extent, it is typically difficult to achieve complete coverage of the surface. For example, carbon coating may increase the specific surface area of ​​the material, exacerbating side reactions between the surface and the electrolyte, and affecting the battery's cycle life. Summary of the Invention

[0005] In view of this, embodiments of this application provide a novel composite anode material, its preparation method, and its application, so that lithium-ion batteries using this composite anode material can achieve both good cycle performance and rate performance.

[0006] Specifically, the first aspect of this application provides a composite negative electrode material, comprising:

[0007] The core comprises one of silicon-based materials, tin-based materials, and phosphorus-based materials;

[0008] The composite coating layer includes a fast electron conductor material and a fast ion conductor material, wherein the fast electron conductor material coats a portion of the surface of the core, and the fast ion conductor material covers the surface of the core that is not covered by the fast electron conductor material.

[0009] By setting a composite coating layer containing fast electron conductor material and fast ion conductor material on the surface of the core, and the composite coating layer can achieve full coverage of the core surface, the volume expansion of the core and the side reaction between the core and the electrolyte are effectively suppressed, thereby ensuring high cycle stability of the composite anode material. In addition, the composite coating layer has good electronic conductivity and ion conductivity, so the composite anode material can have good rate performance.

[0010] In this application embodiment, the fast electron conductor material includes one or more of amorphous carbon, carbon nanotubes, graphene, and conductive polymers; the fast ion conductor material includes one or more of lithium silicate, sodium silicate, lithium aluminate, lithium phosphate, aluminum phosphate, oxide solid electrolyte, sulfide solid electrolyte, halide solid electrolyte, and polymer solid electrolyte.

[0011] In this embodiment of the application, the fast electron conductor material is discontinuously distributed on the surface of the core; the fast ion conductor material is discontinuously distributed on the surface of the core.

[0012] In some embodiments of this application, the composite coating layer includes multiple coating regions of the fast electron conductor material and multiple coating regions of the fast ion conductor material distributed alternately on the surface of the core. The island-like discontinuous distribution of the fast electron conductor material and the fast ion conductor material on the surface of the core is beneficial to ensuring their respective high adhesion stability and makes it easier to achieve full coverage of the core surface.

[0013] In this embodiment, the fast ion conductor material has a coverage rate of 1%-50% on the core surface, and the fast electron conductor material has a coverage rate of 50%-99% on the core surface. This is beneficial for the above-mentioned composite anode material to have both good ionic conductivity and electronic conductivity, so as to have good rate performance.

[0014] In this embodiment, the coating thickness of the fast electron conductor material on the core surface and the coating thickness of the fast ion conductor material on the core surface are independently within the range of 0.5 nm to 20 nm. The relatively thin coating thickness of the fast electron conductor material and the fast ion conductor material does not significantly affect the specific capacity of the core material.

[0015] In some embodiments of this application, the coating thickness of the fast electron conductor material on the core surface is the same as the coating thickness of the fast ion conductor material on the core surface. In this case, the composite negative electrode material formed after the core is coated has the smallest specific surface area and stronger tolerance to the stress generated by the lithium intercalation expansion of the core material.

[0016] In this embodiment of the application, the mass percentage of the composite coating layer in the composite anode material is greater than 0% and less than or equal to 10%. In this case, the composite coating layer can effectively improve the ion and electron transport performance of the composite anode material without causing a significant decrease in its specific capacity.

[0017] In this embodiment, the fast ion conductor material accounts for 1%-75% of the mass of the composite coating layer. The composite coating layer contains appropriate amounts of both fast ion and fast electron conductor materials, which helps the composite anode material to maintain good ionic and electronic conductivity.

[0018] In this embodiment of the application, the fast ion conductor material accounts for 0.1%-8% of the mass of the composite anode material. This helps to ensure that the composite anode material has good ion transport performance and high specific capacity.

[0019] In this embodiment, the mass of the fast electron conductor material is 0.1%-10% of the mass of the core. Coating a suitable amount of the fast electron conductor material on the surface of the core can improve the electron transport performance of the composite anode material while ensuring its high specific capacity.

[0020] In this embodiment, the silicon-based material includes one or more of elemental silicon, silicon alloys, silicon oxides, and silicon-carbon composite materials; the tin-based material includes one or more of elemental tin, tin alloys, tin oxides, and tin-carbon composite materials; and the phosphorus-based material includes one or more of elemental phosphorus and phosphorus-carbon composite materials. These core materials exhibit significant volume expansion effects, making it essential to coat their surfaces with the aforementioned composite coating layers to improve their structural and interfacial stability.

[0021] In this embodiment, the particle size of the core is 1-20 μm. Having a suitable particle size in the core material avoids both excessively large particle sizes that would lengthen the lithium-ion diffusion path and degrade the material's rate performance, and excessively small particle sizes that would result in low compaction density.

[0022] The second aspect of this application provides a method for preparing a composite negative electrode material, including the following steps:

[0023] A fast electron conductor material is formed on the surface of a core material; wherein the fast electron conductor material covers a portion of the surface of the core material, and the core material includes one of silicon-based materials, tin-based materials, and phosphorus-based materials;

[0024] A core material with the fast electron conductor material on its surface is mixed with a solution of a fast ion conductor material raw material. The resulting mixture is filtered and vacuum dried to form a fast ion conductor material on the core surface not covered by the fast electron conductor material, thus obtaining a core material with a composite coating layer on its surface, i.e., obtaining a composite negative electrode material; wherein, the composite coating layer includes the fast electron conductor material and the fast ion conductor material.

[0025] The above-mentioned method for preparing composite anode materials is simple and easy to operate. It can produce a composite coating layer that fully covers the core material and contains both fast electron conductor materials and fast ion conductor materials, thus endowing the resulting composite anode material with good cycle stability and rate performance.

[0026] In this embodiment of the application, the raw materials for the fast ion conductor material include one or more of the following: aromatic hydrocarbon lithium salts, sodium hydroxide, lithium hydroxide, lithium phosphate, lithium phosphate, aluminum phosphate, lithium aluminum phosphate, lithium metaphosphate, oxide solid electrolytes, sulfide solid electrolytes, halide solid electrolytes, and polymer solid electrolytes.

[0027] A third aspect of this application provides a negative electrode sheet, which includes a current collector and a negative electrode active material layer disposed on the current collector. The negative electrode active material layer includes a composite negative electrode material as described in the first aspect of this application, or a composite negative electrode material prepared by the preparation method described in the second aspect of this application. The negative electrode sheet using the above-mentioned composite negative electrode material exhibits high cycle stability and good rate performance.

[0028] A fourth aspect of this application provides a battery including a positive electrode, a negative electrode, and an electrolyte between the positive and negative electrodes. The negative electrode includes the negative electrode as described in the third aspect of this application, or a composite negative electrode material as described in the first aspect of this application. The battery can be a liquid battery, a solid-state battery, or a semi-solid-state battery. The battery can be a lithium-ion secondary battery.

[0029] Since the negative electrode of this battery uses the composite negative electrode material provided in the embodiments of this application, it can have good cycle stability and rate performance.

[0030] The fifth aspect of this application provides an electrical device, wherein the electrical device has an electrical component and a battery as described in the fourth aspect of this application, the electrical component and the battery are connected, and by using the battery to power the electrical component, the user experience and market competitiveness of the electrical device can be improved.

[0031] A sixth aspect of this application provides an energy storage device, which includes a battery as described in a fourth aspect of this application. The battery stores electrical energy in the energy storage device. Using the battery provided in this application can improve the performance of the energy storage device and enhance product competitiveness. Attached Figure Description

[0032] Figure 1 is a structural schematic diagram of the composite negative electrode material 100 provided in an embodiment of this application.

[0033] Figure 2 is a schematic diagram of a preparation method of the composite negative electrode material 100 provided in the embodiments of this application.

[0034] Figure 3 is a schematic cross-sectional view of the negative electrode sheet 200 provided in an embodiment of this application.

[0035] Figure 4 is a schematic diagram of a battery 300 provided in an embodiment of this application.

[0036] Figure 5 is a structural schematic diagram of an electrical device 400 provided in an embodiment of this application.

[0037] Figure 6 is a structural schematic diagram of an energy storage device 500 provided in an embodiment of this application.

[0038] Figure 7 summarizes the transmission electron microscopy (TEM) images of the composite anode materials prepared in Comparative Example 1 and Example 1.

[0039] Figure 8 summarizes the room temperature discharge rate curves of the pouch cells made using the composite negative electrode materials of Example 1 and Comparative Example 1.

[0040] Figure 9 summarizes the room temperature cycling performance curves of the pouch cells made using the composite negative electrode materials of Example 1 and Comparative Example 1. Detailed Implementation

[0041] The embodiments of this application will now be described in conjunction with the accompanying drawings.

[0042] Silicon-based and phosphorus-based anode materials, which have high theoretical specific capacity, exhibit significant volume changes during battery charging and discharging, leading to numerous negative impacts. Taking silicon-based materials as an example, particle breakage / pulverization causes structural damage to the active anode material layer containing it, even detaching it from the electrode sheet, reducing battery capacity. This breakage / pulverization also exposes fresh interfaces, and continuous contact between these fresh interfaces and the electrolyte triggers the formation, destruction, and regeneration of the SEI (solid electrolyte interface) film, increasing interfacial side reactions between the silicon-based material and the electrolyte. This results in electrolyte consumption and loss of active lithium, ultimately leading to battery capacity loss and reduced cycle life. Furthermore, silicon-based materials have low intrinsic conductivity and poor kinetic performance, affecting the improvement of battery charge / discharge rate performance. To alleviate the lithium intercalation volume expansion problem of silicon-based materials, the industry typically employs coating layers on the silicon surface, such as conductive carbon coating layers or non-conductive polymer or ceramic coating layers. While the carbon coating in the former method can improve the electronic conductivity of silicon-based materials, it may also increase the specific surface area of ​​the resulting composite material, exacerbating side reactions between the silicon-based material surface and the electrolyte, thus affecting the cycle life of the battery. The coating used in the latter method leads to a decrease in the electronic conductivity of the composite material, reducing its rate performance. Therefore, this application provides a composite anode material with minimal volume expansion and good rate performance, along with its preparation method and applications.

[0043] Please refer to Figure 1, which is a schematic diagram of a composite anode material 100 provided in an embodiment of this application. The composite anode material 100 includes a core 10 and a composite coating layer 20. The composite coating layer 20 coats the core 10. The core 10 includes one of a silicon-based material, a phosphorus-based material, or a tin-based material. The composite coating layer 20 includes a fast electron conductor material 21 and a fast ion conductor material 22. The fast electron conductor material 21 coats a portion of the surface of the core 10, and the fast ion conductor material 22 covers the surface of the core 10 not covered by the fast electron conductor material 21.

[0044] The silicon-based, phosphorus-based, and tin-based materials used in the core 10 are negative electrode materials with significant volume expansion effects. By setting a composite coating layer 20 composed of fast electron conductors and fast ion conductors on the surface of such a core 10, firstly, the composite coating layer 20 can limit the volume expansion of the core 10 during lithium intercalation, ensuring the particle integrity of the composite negative electrode material 100 and its long-term structural stability. Secondly, the composite coating layer 20 can achieve full coverage of the surface of the core 10, thereby effectively isolating the core 10 from the electrolyte, stabilizing the interface of the core 10, and effectively suppressing the capacity decay caused by side reactions between the core 10 and the electrolyte during charge-discharge cycles, thus improving the cycle stability of the composite negative electrode material 100. Thirdly, the composite coating layer 20 on the surface of the core 10 contains both fast electron conductor material and fast ion conductor material, which can ensure that the composite anode material 100 has high electronic conductivity and ion conductivity at the same time, which is conducive to the rapid transport of ions and electrons inside the composite anode material 100 particles, so that the material has a high fast charge and discharge capability (i.e., rate performance).

[0045] In this embodiment, the fast electron conductor material 21 may be one or more of amorphous carbon, carbon nanotubes, graphene, and conductive polymers (such as polyaniline, polypyrrole, etc.). In some embodiments, the fast electron conductor material 21 is amorphous carbon, which can be coated on the surface of the core 10 by chemical vapor deposition.

[0046] In this embodiment, the fast ion conductor material 22 may include one or more of lithium silicate, sodium silicate, lithium aluminate, lithium phosphate, aluminum phosphate, oxide solid electrolyte, sulfide solid electrolyte, halide solid electrolyte, and polymer solid electrolyte. These materials have high ionic conductivity. By using a composite coating layer 20 containing these materials and the fast electron conductor material to coat the core 10, the ion transport performance of the resulting composite anode material 100 is improved.

[0047] Lithium silicate and sodium silicate are particularly suitable when the core 10 is a silicon-based material. For example, fast-ion conductor materials made of lithium silicate can be formed on the core through in-situ reaction after mixing the silicon-based material with an aprotic solvent of aromatic hydrocarbon lithium (such as biphenyl lithium); they can also be formed on the core through in-situ reaction after mixing the silicon-based material with an ethanol solution of lithium hydroxide (LiOH). For example, fast-ion conductor materials made of sodium silicate can be formed on the core through in-situ reaction after mixing the silicon-based material with an ethanol solution of sodium lithium hydroxide (NaOH).

[0048] For example, the oxide solid electrolyte may include, but is not limited to, one or more of the following substances: lithium aluminum titanium phosphate (LATP, chemical formula may be Li 1+x Alx Ti 2-x (PO4)3, 0 < x < 2), lithium aluminum germanium phosphate (chemical formula can be Li 1+x Al x Ge 2-x (PO4)3,0<x<2), Li7La3Zr2O 12 Lithium lanthanum zirconium tantalum oxide.

[0049] Sulfide solid electrolytes may include, but are not limited to, one or more of the following substances: crystalline Li a M b P c S d (M = Ge, Sn, Si or one of them, a + 4b + 5c = 2d, for example Li) 10 GeP2S 12 Li-PS systems (e.g., glassy Li2S-P2S5) and Li6PS5X (X = Cl, Br, I).

[0050] Halogenated solid electrolytes may include, but are not limited to, one or more of the following substances: Li3InCl6, Li2ZrCl6, and Li3InBr6.

[0051] Polymer solid electrolytes may include, but are not limited to, one or more of the following substances: PEO (polyethylene oxide), PAN (polyacrylonitrile), PVDF (polyvinylidene fluoride), PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene copolymer), and PMMA (polymethyl methacrylate).

[0052] In some embodiments of this application, the fast ion conductor material 22 is one or more of lithium phosphate, aluminum phosphate, lithium metaphosphate, lithium silicate, and sodium silicate.

[0053] In this application, the composite coating layer 20 is a composite coating layer composed of a fast electron conductor material and a fast ion conductor material distributed alternately. "Alternating distribution" refers to their alternating distribution on the surface of the core. Specifically, the composite coating layer 20 has a 100% coverage rate on the surface of the core 10. In this case, the fast ion conductor material 22 completely covers the surface of the core 10 that is not covered by the fast electron conductor material 21. This complete coverage of the core 10 surface by the composite coating layer 20 can better isolate the core 10 from the electrolyte, avoiding interfacial side reactions and ensuring better cycle stability of the composite negative electrode material 100.

[0054] In this embodiment, the fast electron conductor material 21 is discontinuously distributed on the surface of the core 10. That is, the fast electron conductor material 21 is a discontinuous film structure. The fast electron conductor material 21 is in direct contact with the core 10. The fast electron conductor material can be discontinuously attached to the surface of the core 10 by chemical vapor deposition (CVD), physical vapor deposition (PVD), or solid-phase coating, forming a structure in which the fast electron conductor material 21 covers part of the surface of the core 10. The surface of the core 10 not covered by the fast electron conductor material 21 becomes a potential site for active ions (such as Li). + The fast ion conductor material 22 is disposed on the surface of the core 10 not covered by the fast electron conductor material 21, and correspondingly, the fast ion conductor material 22 is also discontinuously distributed on the surface of the core 10. The fast ion conductor material 22 is in direct contact with the core 10.

[0055] Among them, the fast electron conductor material 21 and the fast ion conductor material 22 can be distributed discontinuously on the surface of the core 10 in a dotted pattern, or discontinuously on the surface of the core 10 in an island pattern, or a combination of dotted and island patterns. The morphology and distribution of these two coating materials can be obtained by TEM (Transmission Electron Microscopy) observation of the composite negative electrode material 100.

[0056] In some embodiments of this application, the composite coating layer 20 includes coating regions of multiple fast electron conductor materials 21 and multiple fast ion conductor materials 22 distributed alternately on the surface of the core 10 (as shown in Figure 2 below). In this case, the fast electron conductor materials 21 and fast ion conductor materials 22 are distributed discontinuously in an island-like pattern on the surface of the core 10. The thickness of each fast electron conductor material coating region may be the same or different; the thickness of each fast ion conductor material coating region may be the same or different.

[0057] In some embodiments of this application, the fast electron conductor material 21 has a coverage rate of 50%-99% on the surface of the core 10. That is, the core area covered by the fast electron conductor material 21 accounts for 50%-99% of the total surface area of ​​the core 10, i.e., the fast electron conductor material 21 covers 50%-99% of the surface area of ​​the core 10. This coverage rate can be obtained by combining SEM and / or TEM images of the composite anode material 100 with software statistics. A suitable fast conductor material coating coverage rate can ensure both improved electron conductivity of the core 10 coated with the fast conductor material and sufficient active ion transport channels are retained. For example, the coverage rate of the fast electron conductor material 21 on the core surface can specifically be 52%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%, etc.

[0058] In some embodiments of this application, the coverage of the fast ion conductor material 22 on the surface of the core 10 can be 1%-50%. A suitable coverage range of the fast ion conductor material on the surface of the core 10 facilitates the composite negative electrode material 100 in achieving both good ionic conductivity and electronic conductivity. Specifically, the coverage of the fast ion conductor material 22 on the surface of the core can be 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, or 45%, etc.

[0059] In this embodiment, the coating thickness of the fast electron conductor material 21 on the surface of the core 10 and the coating thickness of the fast ion conductor material 22 on the surface of the core 10 are independently within the range of 0.5 nm to 20 nm. Having the fast electron conductor material and the fast ion conductor material within an appropriate range on the core surface can effectively suppress volume expansion of the core 10 material without significantly affecting its specific capacity. In some embodiments, the coating thickness of the fast electron conductor material 21 on the surface of the core 10 and the coating thickness of the fast ion conductor material 22 on the surface of the core 10 are independently within the range of 2 nm to 10 nm.

[0060] In some embodiments of this application, the coating thickness of the fast electron conductor material 21 on the surface of the core 10 is the same as the coating thickness of the fast ion conductor material 22 on the surface of the core 10. In this case, the composite negative electrode material 100 formed after coating the core 10 has the smallest specific surface area and is more resistant to the stress generated by the lithium intercalation expansion of the core material.

[0061] In this embodiment of the application, the mass percentage of the composite coating layer 20 in the composite anode material 100 is in the range of greater than 0% to less than or equal to 10%. This allows for the improvement of the ion and electron transport performance of the composite anode material 100 using the composite coating layer 20 without significantly reducing the specific capacity of the composite anode material. In some embodiments, the mass percentage of the composite coating layer 20 in the composite anode material 100 is 0.1%-5%.

[0062] In this embodiment, the fast ion conductor material 22 accounts for 1%-75% of the mass of the composite coating layer 20. That is, the fast ion conductor material accounts for 1%-50% of the mass of the composite coating layer 20. This is more conducive to the composite negative electrode material 100 achieving both good electronic conductivity and ion conductivity. For example, this mass percentage can be 2%, 5%, 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70%, etc. Since the composite coating layer 20 is composed of a fast ion conductor material and a fast electron conductor material, the fast electron conductor material accounts for 25%-95% of the mass of the composite coating layer 20.

[0063] In some embodiments of this application, the fast ion conductor material 22 accounts for 0.1%-8% of the mass of the composite anode material 100. In this case, while utilizing the fast ion conductor material 22 to improve the ion transport performance of the composite anode material 100, a high specific capacity can be ensured. This mass percentage can be characterized by inductively coupled plasma atomic emission spectrometry (ICP-AES). Exemplarily, this mass percentage can further be 0.1%-5%, specifically 0.2%, 0.5%, 0.8%, 1.0%, 1.5%, 2%, 2.5%, 3%, 4%, 5%, etc.

[0064] In some embodiments of this application, the mass of the fast electron conductor material 21 is 0.1%-10% of the mass of the core 10. Appropriate partial coating of the fast electron conductor material on the surface of the core can improve the electron transport performance of the composite anode material 100 while ensuring that the composite anode material 100 has a high specific capacity. This parameter value can be characterized by inductively coupled plasma atomic emission spectroscopy (ICP-AES). Specifically, the mass of the fast electron conductor material 21 is 0.2%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, etc., of the mass of the core 10.

[0065] In some possible embodiments of this application, the surface of the fast electron conductor material 21 is further distributed with a fast ion conductor material 22.

[0066] In this application, the silicon-based material may include one or more of elemental silicon, silicon alloys, silicon oxides, and silicon-carbon composite materials. The silicon-carbon composite material may include a composite of at least one of elemental silicon, silicon alloys, and silicon oxides with a carbon material. Similarly, the tin-based material may include one or more of elemental tin, tin alloys, tin oxides, and tin-carbon composite materials. The phosphorus-based material includes one or more of elemental phosphorus and phosphorus-carbon composite materials. The phosphorus-carbon composite material may be a composite of elemental phosphorus and a carbon material. In some embodiments of this application, the core 10 is a silicon-based material, which has the highest theoretical specific capacity.

[0067] In some embodiments of this application, the particle size of the core 10 can be 1μm-20μm. This particle size refers to its volumetric median particle size, specifically the particle size at which the cumulative volume distribution reaches 50%, i.e., the D50 particle size. Having a suitable particle size for the core material avoids both excessively large particle sizes that would lengthen the lithium-ion diffusion path and degrade the material's rate performance, and excessively small particle sizes that would result in low compaction density. For example, the particle size of the core 10 can be 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, etc. The core 10 can be regular or irregular granular, such as spherical or near-spherical particles.

[0068] This application also provides a method for preparing the composite negative electrode material 100 described above. Referring to Figure 2, Figure 2 is a schematic flowchart of a method for preparing the composite negative electrode material 100 provided in this application embodiment. The preparation method includes the following steps S10 and S20.

[0069] S10, a fast electron conductor material 21 is formed on the surface of the core 10; wherein, the fast electron conductor material 21 covers part of the surface of the core 10, and the core 10 includes one of silicon-based materials, tin-based materials, and phosphorus-based materials.

[0070] S20, the core 10 with fast electron conductor material 21 on its surface is mixed with a solution of fast ion conductor material raw material, the resulting mixture is filtered and vacuum dried, and fast ion conductor material 22 is formed on the surface of the core 10 not covered by fast electron conductor material 21, thus obtaining a core 10 with a composite coating layer 20 on its surface, that is, obtaining a composite negative electrode material; the composite coating layer 20 includes fast electron conductor material 21 and fast ion conductor material 22.

[0071] As described above, the fast electron conductor material 21 may be one or more of amorphous carbon, carbon nanotubes, graphene, and conductive polymers (such as polyaniline, polypyrrole, etc.). In step S10, the formation method of the fast electron conductor material 21 on the surface of the core 10 is not limited, and may include, for example, vapor deposition (including physical vapor deposition or chemical vapor deposition (CVD)) or solid-phase coating (such as ball milling, sand milling, etc.). Physical vapor deposition may include, for example, evaporation or magnetron sputtering. Vapor deposition or solid-phase coating can easily form a fast electron conductor material 21 covering part of the core surface on the surface of the core 10, leaving part of the core 10 surface exposed, reserving space for subsequent coating of the fast ion conductor material.

[0072] In some embodiments of this application, the fast electron conductor material 21 is amorphous carbon, which can be formed on the surface of the core 10 by CVD to form an amorphous carbon coating layer. Specifically, the construction method of the amorphous carbon coating layer includes: placing the core material to be coated in a deposition apparatus, controlling the temperature and pressure in the deposition apparatus to reach certain conditions, and introducing an organic carbon source gas into the deposition apparatus to thermally decompose and deposit the organic carbon source to form the carbon coating layer. The specific distribution of the carbon coating material on the core surface (such as coverage and distribution density) can be controlled by adjusting parameters including the temperature, pressure, flow rate of the organic carbon source, and deposition time.

[0073] In addition, conductive polymer coatings can also be formed via vapor deposition. Carbon nanotubes and graphene can generally be formed via solid-phase coating.

[0074] In step S20, the fast ion conductor material 22 is formed on the surface of the core 10 by liquid-phase coating, or wet coating. The core 10 with the fast electron conductor material 21 on its surface is mixed with a solution containing the fast ion conductor material raw material. Based on the wettability / flowability of the solution, it can be easily adsorbed onto the core surface not covered by the fast electron conductor material 21, thereby forming a fast ion conductor material coating area. Together with the fast electron conductor material, it achieves complete coating of the surface of the core 10.

[0075] The solvent in the solution of the fast ion conductor material raw material may include one or more of water, ethanol, and aprotic organic solvents. The specific solvent may be determined according to the coating layer raw material used. The aprotic organic solvent may include one or more of tetrahydrofuran (THF), 2-methyltetrahydrofuran, diethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether, N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), p-xylene, anisole, etc., but is not limited to these.

[0076] In some embodiments of this application, the raw material for the fast ion conductor material is either the raw material used to form the fast ion conductor material or the fast ion conductor material itself. For example, the raw material used to form a fast ion conductor material of lithium silicate can be an aromatic hydrocarbon lithium salt or lithium hydroxide (LiOH). After the silicon-based core material is mixed with a solution of the raw material, an in-situ reaction can occur to form lithium silicate. As another example, the raw material used to form a fast ion conductor material of sodium silicate can be sodium hydroxide. After the raw material is mixed with the silicon-based core material, an in-situ reaction can occur to form a sodium silicate fast ion conductor material.

[0077] In some embodiments of this application, the raw materials for forming the fast ion conductor material include aromatic hydrocarbon lithium salts. These aromatic hydrocarbon lithium salts can be obtained by reacting aromatic substances (such as biphenyl, p-toluene, naphthalene, etc.), metallic lithium, and an aprotic organic solvent. Specifically, the aromatic hydrocarbon lithium salts can include at least one of lithium biphenyl, lithium p-toluene, and lithium naphthylene. When the silicon-based material is contacted (e.g., immersed) in a solution of the organic solvent containing the aromatic hydrocarbon lithium salt, a lithiation reaction can occur on the surface of the silicon-based material to form lithium silicate. The aprotic organic solvent can include, but is not limited to, one or more of tetrahydrofuran (THF), 2-methyltetrahydrofuran, diethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether, N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), p-xylene, and anisole.

[0078] In another embodiment of this application, the solution of the raw material for forming the fast ion conductor material is an ethanol solution of LiOH. When the silicon-based material comes into contact with the ethanol solution of LiOH (e.g., is immersed in it), the surface layer of the silicon-based material can react to form lithium silicate. In yet another embodiment of this application, the solution of the raw material for forming the fast ion conductor material is an ethanol solution of NaOH. When the silicon-based material comes into contact with the ethanol solution of NaOH (e.g., is immersed in it), the surface layer of the silicon-based material can react to form sodium silicate.

[0079] In another embodiment of this application, the solution of the raw materials for forming the fast ion conductor material includes aluminum hydroxide sol and an aqueous solution of LiOH. The aluminum hydroxide sol is formed by hydrolysis of aluminum isopropoxide in a mixed solution containing anhydrous ethanol and water. After the aluminum hydroxide sol is mixed with the core material to be coated (such as a silicon-based material), due to the different charge states of the exposed surfaces of the aluminum hydroxide sol and the silicon-based material, the electropositive aluminum hydroxide sol is more easily adsorbed / bound to the exposed electronegative surface of the silicon-based material. Then, an aqueous solution of LiOH is added, and after heat treatment under certain conditions, a lithium aluminate coating material is formed on the surface of the silicon-based material through the reaction of aluminum hydroxide and LiOH.

[0080] In some other embodiments of this application, in step S20, the fast ion conductor material raw material is the fast ion conductor material itself, such as one or more selected from oxide solid electrolytes, sulfide solid electrolytes, halide solid electrolytes, polymer solid electrolytes, lithium phosphate, and aluminum phosphate. Exemplarily, the core material can be immersed in a solution of these fast ion conductor materials so that the fast ion conductor material can be adsorbed onto the surface of the core material not coated with it. The immersed material is then filtered, and the solids are collected. The solids are then vacuum-dried to remove the solvent, forming the fast ion conductor material in the core material. In some embodiments, after the vacuum drying, a heat treatment at an appropriate temperature is performed to enhance the bonding force between the fast ion conductor material and the core material.

[0081] In some embodiments of this application, in step S20, the fast ion conductor material 22 may also be formed on the surface of the fast electron conductor material 21.

[0082] The method for preparing the composite anode material provided in this application involves coating a fast electron conductor material onto a portion of the core surface, followed by a wet coating process to form a fast ion conductor material on the uncoated core surface. This achieves complete coating of the core surface, thereby isolating the core from interfacial side reactions with the electrolyte. This enhances the cycle stability of the composite anode material while ensuring both high electronic conductivity and ion conductivity, resulting in excellent rate performance. The preparation method is simple and suitable for industrial production.

[0083] Referring to Figure 3, which is a cross-sectional structural diagram of a negative electrode sheet 200 provided in an embodiment of this application, the negative electrode sheet 200 includes a negative electrode current collector 201 and a negative electrode active material layer 202 disposed on the negative electrode current collector 201. The negative electrode active material layer 202 includes the composite negative electrode material 100 described above in the embodiment of this application. The negative electrode active material layer 202 may be disposed on one side surface or opposite two sides of the negative electrode current collector 201. The composite negative electrode material 100 serves as the negative electrode active material of the negative electrode sheet 200. The negative electrode active material layer 202 may use only the aforementioned composite negative electrode material 100 as the negative electrode active material, or it may simultaneously use the aforementioned composite negative electrode material 100 and other negative electrode active materials (e.g., graphite).

[0084] The negative electrode active material layer 202 also includes a conductive agent and a binder. Exemplary binders may include, but are not limited to, one or more of sodium alginate, carboxymethyl cellulose (CMC) or its salts, styrene-butadiene rubber (SBR), polyacrylic acid (PAA) or its salts, polyacrylate, polyacrylamide (PAM), etc. Exemplary conductive agents may include one or more of Super P carbon black, acetylene black, Ketjen black, amorphous carbon, carbon nanotubes, graphene, etc. The negative electrode current collector 201 may be a metal foil (e.g., aluminum foil) or a carbon-coated metal foil, etc.

[0085] This application also provides a battery, which includes the negative electrode sheet described above in this application embodiment. It will be understood that the negative electrode of this battery also includes the composite negative electrode material 100 described above in this application embodiment.

[0086] Referring to Figure 4, Figure 4 is a schematic diagram of a battery 300 provided in an embodiment of this application. The battery 300 includes a positive electrode 301, a negative electrode 302, an electrolyte 303 located between the positive electrode 301 and the negative electrode 302, and a corresponding circuit. The negative electrode 302 includes the negative electrode sheet 200 described above in the embodiment of this application.

[0087] In some embodiments of this application, the battery 300 can be a liquid battery, a solid-state battery, or a semi-solid-state battery. In some embodiments of this application, the battery 300 is a liquid battery, and the electrolyte 303 is a liquid electrolyte. In this case, the battery 300 also includes a separator 304 (as shown in Figure 4) located between the positive electrode 301 and the negative electrode 302. The separator 304 has ion conductivity and electronic insulation, and is used to separate the positive electrode 301 and the negative electrode 302 to prevent short circuits between them. In other embodiments of this application, the battery 300 is a solid-state or semi-solid-state battery, and correspondingly, the electrolyte 303 is a solid-state or semi-solid-state electrolyte membrane.

[0088] The positive electrode 301 can be any commercially available or self-prepared battery positive electrode, and this application does not impose any special limitations. Generally, the positive electrode 301 includes a positive electrode current collector and a positive electrode active material layer disposed thereon. The positive electrode active material layer includes a positive electrode active material, a binder, and an optional conductive agent. The separator 304 can be, but is not limited to, single-layer polypropylene (PP), single-layer polyethylene (PE), double-layer PP / PE, double-layer PP / PP, triple-layer PP / PE / PP, etc.

[0089] The aforementioned battery 300 can be a lithium-ion secondary battery or a sodium-ion secondary battery, etc. The composite anode material 100 with a core of silicon-based, phosphorus-based, or tin-based materials can be used in lithium-ion secondary batteries. The composite anode material 100 with a core of phosphorus-based materials can be used in sodium-ion secondary batteries.

[0090] Battery 300 stores and releases energy through the insertion and extraction of active ions (lithium ions in the case of a lithium secondary battery) between the positive electrode 301 and the negative electrode 302. The charging / discharging principle of battery 300 is explained below using a liquid lithium secondary battery as an example. As shown in Figure 4, during charging, under the action of an external circuit, lithium ions (Li... + Electrons (e-) are released from the positive electrode active material in the positive electrode 301, migrate through the liquid electrolyte 303 and separator 304 to the negative electrode 302, and simultaneously, electrons (e-) flow from the external circuit from the positive electrode 301 to the negative electrode 302, increasing the open-circuit voltage of the battery 300 and storing electrical energy. During discharge, Li... + The negative electrode active material in the negative electrode 302 is released and migrates back to the positive electrode 301 through the liquid electrolyte 303 and the separator 304. Corresponding electrons (e-) migrate from the negative electrode 302 to the positive electrode 301 from the external circuit, reducing the battery voltage and releasing electrical energy to perform work, such as supplying electrical energy to the load electrically connected to the battery 300. In Figure 4, the rightward arrow represents the charging process, and the leftward arrow represents the discharging process.

[0091] In the battery 300 provided in this application embodiment, the negative electrode 302 adopts the composite negative electrode material 100 provided in this application embodiment. Because the composite negative electrode material 100 has high structural stability and kinetic performance, it is beneficial to improve the cycle stability and rate performance of the battery 300. This battery can be used in consumer electronic devices (such as mobile phones, tablets, laptops, and wearable electronic devices), as well as in mobile devices (such as electric vehicles, electric bicycles), drones, energy storage devices, base stations, and other equipment products to improve product performance.

[0092] Referring to Figure 5, which is a schematic diagram of a device 400 provided in an embodiment of this application, the device 400 includes a housing 401, electronic components (not shown in Figure 5) housed within the housing 401, and the battery 300 described in this embodiment. The electronic components are electrically connected to the battery 300. The battery 300 provides power to the electronic components. The electronic components are electrical elements within the device 400.

[0093] The electrical device 400 can be any device that uses electricity, including consumer electronics such as mobile phones, tablets, desktop computers, laptops, portable computers, power banks, smart screens, digital cameras, speakers, wearable devices (such as glasses, watches, bracelets, headphones, etc.), augmented reality (AR) devices, virtual reality (VR) devices, and in-vehicle devices; it can also be mobile devices such as vehicles (e.g., electric cars, electric bicycles, electric buses, electric trucks, etc.), ships, aerospace equipment, drones, etc. Using the battery provided in this application embodiment can improve the performance of these electrical devices, thereby enhancing product competitiveness. In one embodiment of this application, the electrical device 400 shown in FIG5 can specifically be a mobile phone. The casing 401 of the mobile phone can include a front cover assembled on the front side of the phone and a back cover assembled on the rear side, and the battery 300 can be fixed inside the back cover.

[0094] This application also provides an energy storage device, including a receiving cavity and a battery housed in the receiving cavity, wherein the battery stores electrical energy for the energy storage device. The energy storage device generally includes multiple batteries 300 as described above.

[0095] Referring to Figure 6, Figure 6 is a structural schematic diagram of an energy storage device 500 provided in an embodiment of this application. The energy storage device 500 includes a receiving cavity 51 and a battery pack 52. The battery pack 52 is housed within the receiving cavity 51 and can be a module formed by multiple batteries 300 connected in series, parallel, or in combination. Any two batteries 300 can be connected in series or parallel. Specifically, the energy storage device shown in Figure 6 can be a battery pack. In some embodiments, the energy storage device 500 may further include a Battery Management System (BMS) 53, which can be electrically connected to the battery pack 52. The BMS 53 can be used to monitor the status information of each battery 300 in the battery pack 52, such as temperature, voltage, current, internal resistance, etc., and control the charging / discharging status of each battery 300.

[0096] This application also provides an energy storage system, which includes a power converter electrically connected to the energy storage device described in this application. The number of energy storage devices or power converters can be one or more. The power converter is used to convert the voltage and / or current output from the energy storage device and output it to the power grid or electrical load, and / or to convert the voltage and / or current output from an external power source and input it to the energy storage device.

[0097] The technical solution of this application will be further described below with reference to several embodiments.

[0098] Example 1

[0099] The preparation of a composite anode material includes:

[0100] (1) The silicon-based material to be coated (specifically, silicon powder with an average particle size of 7 μm) is placed in a chemical vapor deposition (CVD) furnace, heated to maintain the furnace temperature at 600 °C, and argon gas is introduced to maintain the furnace pressure at 500 Pa. Then, acetylene gas is introduced into the furnace at a flow rate of 20 sccm (i.e., 20 mL / min) for 2 h to allow acetylene to decompose and deposit on the surface of the silicon-based material to generate amorphous carbon, thus obtaining a silicon-based material coated with amorphous carbon. The amorphous carbon does not completely cover the entire surface of the silicon-based material, but only covers a portion of its surface.

[0101] (2) Dissolve NaOH in ethanol and stir thoroughly to obtain an ethanol solution with a NaOH concentration of 0.01 wt%.

[0102] (3) The silicon-based material whose surface is partially coated with amorphous carbon is immersed in the above-mentioned NaOH ethanol solution and stirred at 25°C for 24 hours to allow the silicon-based material not coated with amorphous carbon to react with NaOH to generate a fast ion conductor material (specifically sodium silicate). The resulting reaction material is then filtered, and the filtered solid is washed with ethanol and then vacuum dried to obtain a silicon-based material whose surface is completely coated with a composite coating layer, i.e., a composite anode material. The composite coating layer includes amorphous carbon and sodium silicate, with sodium silicate covering the surface of the silicon-based material not covered by amorphous carbon.

[0103] Comparative Example 1

[0104] The difference from Example 1 is that only the silicon-based material is coated with amorphous carbon in the same way as step (1) of Example 1.

[0105] Figure 7 summarizes TEM images of the composite anode materials prepared in Comparative Example 1 and Example 1. By observing the differences in the crystal structure of the materials, it can be seen that in the left image of Figure 7, the area outlined by the blue circle (lighter grayscale) is the distribution area of ​​amorphous carbon. It can be seen that some surfaces of the silicon particles (as indicated by the arrows) do not contain this amorphous carbon. In the right image of Figure 7, the area outlined by the blue circle is the distribution area of ​​amorphous carbon, and the area outlined by the yellow circle (as indicated by the dashed arrows) is the distribution area of ​​fast ion conductor material (specifically lithium silicate). This fast ion conductor material is located in the gap between adjacent amorphous carbon material distribution areas. The composite coating layer composed of these two materials can completely cover the surface of the silicon particles, that is, their coverage rate on the silicon particle surface is 100%.

[0106] Furthermore, based on the TEM images of the composite anode material, the fast electron conductors and fast ion conductors on the surface of the silicon particles were distinguished according to their crystal form. Statistical analysis of the coverage of these two materials revealed that the amorphous carbon covered 76.2% of the silicon-based material surface, while the fast ion conductor material covered 23.8%. Moreover, the fast ion conductor material accounted for 1.2 wt% of the mass of the composite anode material in Example 1, and the amorphous carbon accounted for 0.8% of the mass of the silicon-based material.

[0107] Example 2

[0108] The preparation of a composite anode material includes:

[0109] (1) Provide a silicon-based material whose surface is covered with amorphous carbon portions (same as in Example 1);

[0110] (2) Dissolve biphenyl in tetrahydrofuran (THF) solvent and add metallic lithium. Stir thoroughly at room temperature to obtain a THF solution with a concentration of 0.05 wt% for biphenyl lithium, which is the aryl lithium reagent.

[0111] (3) Under an inert atmosphere, the silicon-based material with an amorphous carbon coating layer on its surface is immersed in the THF solution of the aforementioned lithium biphenyl and stirred at 25°C for 2 hours to allow the silicon-based material not coated with amorphous carbon to undergo a pre-lithiation reaction to generate a fast-ion conductor material (specifically, lithium silicate). The resulting reaction material is then filtered, the solids are collected, and the solids are washed with THF and then vacuum dried to obtain a silicon-based material whose surface is completely coated with a composite coating layer, i.e., a composite anode material. The composite coating layer comprises amorphous carbon and lithium silicate, with lithium silicate covering the surface of the silicon-based material not covered by amorphous carbon.

[0112] Example 3

[0113] The preparation of a composite anode material includes:

[0114] (1) Provide a silicon-based material whose surface is covered with amorphous carbon portions (same as in Example 1);

[0115] (2) The fast ion conductor material—lithium aluminum titanium phosphate (LATP, chemical formula Li) 1.3 Al 0.3 Ti 1.7 (PO4)3) was dissolved in p-xylene solvent and stirred thoroughly to obtain a p-xylene solution of LATP with a concentration of 0.1 wt%.

[0116] (3) The silicon-based material whose surface is partially coated with amorphous carbon is immersed in the above-mentioned LATP in p-xylene solution and stirred at 25°C for 24 hours to coat the surface of the silicon-based material not coated with amorphous carbon with LATP. Then, the resulting reaction material is filtered, and the filtered solid is washed with p-xylene and then vacuum dried to obtain a silicon-based material whose surface is completely coated with the composite coating layer, that is, to obtain the composite anode material. The composite coating layer includes amorphous carbon and LATP, with LATP covering the surface of the silicon-based material not covered by amorphous carbon.

[0117] Example 4

[0118] The preparation of a composite anode material differs from that of Example 1 in that the acetylene gas vapor deposition time in step (1) is 1 hour. In Example 1, TEM characterization of the silicon-based material coated with amorphous carbon and statistical analysis using software revealed that the amorphous carbon coverage on the silicon-based material surface was 50%. Correspondingly, in the composite anode material prepared in Example 4, the fast ion conductor material—sodium silicate—had a 50% coverage on the silicon-based material surface.

[0119] Example 5

[0120] The preparation of a composite anode material includes:

[0121] (1) Provide a silicon-based material whose surface is covered with amorphous carbon portions (same as in Example 1);

[0122] (2) Dissolve naphthalene in dimethyl ethylene glycol (DME) solvent, add lithium metal, and stir thoroughly at room temperature to obtain a DME solution with a concentration of 0.05 wt% naphthalene lithium, which is the aryl lithium reagent.

[0123] (3) Under an inert atmosphere, the silicon-based material with an amorphous carbon coating layer on its surface is immersed in the DME solution of lithium naphthalene and reacted at 25°C for 2 hours to allow the silicon-based material not coated with amorphous carbon to undergo a pre-lithiation reaction to generate a fast-ion conductor material (specifically, lithium silicate). The resulting reactants are then filtered, the solids are collected, and the solids are washed with DME and then vacuum dried to obtain a silicon-based material whose surface is completely coated with a composite coating layer, i.e., a composite anode material. The composite coating layer comprises amorphous carbon and lithium silicate, with lithium silicate covering the surface of the silicon-based material not covered by amorphous carbon.

[0124] Example 6

[0125] The preparation of a composite anode material includes:

[0126] (1) Provide a silicon-based material whose surface is covered with amorphous carbon portions (same as in Example 1);

[0127] (2) The silicon-based material whose surface is partially coated with amorphous carbon and lithium phosphate are dissolved in an appropriate amount of deionized water at a mass ratio of 50:1. The mixture is stirred evenly to obtain a mixture. The mixture is then subjected to ultrasonic treatment to further promote the adhesion of lithium phosphate to the surface of the silicon-based material that is not coated with amorphous carbon.

[0128] (3) The above-mentioned ultrasonically processed material is filtered, and the filtered solid is transferred to a vacuum oven and dried at 60°C to remove water. Then it is heated to 400°C in an inert atmosphere to promote the bonding stability of lithium phosphate on the surface of silicon-based material, so as to obtain silicon-based material whose surface is completely covered by composite coating layer, that is, the desired composite anode material is obtained.

[0129] In the composite anode material prepared in Example 6, the composite coating layer includes amorphous carbon and lithium phosphate. The lithium phosphate covers the surface of the silicon-based material not covered by the amorphous carbon, with a coverage rate of 23.8% on the surface of the silicon-based material. Furthermore, the mass percentage of lithium phosphate in this composite anode material is 2%.

[0130] Example 7

[0131] The preparation of a composite anode material includes:

[0132] (1) Dissolve aluminum isopropoxide in anhydrous ethanol by stirring, and then add the mixed solution formed by mixing deionized water and anhydrous ethanol to cause aluminum isopropoxide to undergo slow hydrolysis and form aluminum hydroxide sol.

[0133] (2) The silicon-based material with amorphous carbon part on the surface (same as in Example 1) is dispersed in ethanol and the above aluminum hydroxide sol is added so that the positively charged aluminum hydroxide sol and the negatively charged exposed surface of the silicon-based material are combined to obtain the first mixture.

[0134] (3) Add an aqueous solution of LiOH to the first mixture and transfer the resulting second mixture to a high-pressure reactor at 150°C for reaction. Specifically, aluminum hydroxide reacts with lithium hydroxide to transform into lithium aluminate, thereby achieving its coating on the surface of the silicon-based material. A silicon-based material with a composite coating layer containing lithium aluminate and amorphous carbon is obtained, i.e., a composite anode material is obtained.

[0135] (4) The silicon-based material coated with the above lithium aluminate is fully annealed at 500°C to stabilize the crystal form of lithium aluminate.

[0136] The composite anode materials obtained in Comparative Example 1 and each embodiment were prepared into anode sheets and pouch cells respectively in the following manner.

[0137] The specific preparation steps of the negative electrode sheet include: mixing graphite as the negative electrode active material and various composite negative electrode materials with binder (specifically polyacrylic acid) and conductive carbon black in a mass ratio of 50:40:6:4, dispersing them in solvent water, and stirring evenly to obtain a negative electrode slurry; uniformly coating the negative electrode slurry onto a copper foil current collector, drying it at room temperature, and then transferring it to a 120°C forced-air oven to dry for 1 hour to form a negative electrode active material layer, followed by cold pressing and die cutting to obtain the negative electrode sheet.

[0138] The specific preparation steps of the soft-pack full battery include: 1) Preparing the positive electrode sheet: The positive electrode material lithium cobalt oxide (LiCoO2) is mixed with binder (polyvinylidene fluoride PVDF) and conductive carbon black at a mass ratio of 98:1:1 and dispersed in N-methylpyrrolidone (NMP). After stirring evenly, a positive electrode slurry is obtained. The positive electrode slurry is uniformly coated on a carbon-coated aluminum foil with a thickness of 9μm, dried at room temperature, and then transferred to a 120℃ forced-air oven to dry for 1 hour to form a positive electrode active material layer. After cold pressing and die cutting, the positive electrode sheet is obtained; 2) The above negative electrode sheets are stacked with the separator and positive electrode sheets in a stacking manner to obtain the battery cell. The battery cell is placed in an aluminum-plastic film packaging shell, electrolyte is injected into the shell, and then sealed in sequence. After standing, hot and cold pressing, formation, capacity testing and other processes, the soft-pack battery is obtained.

[0139] The room temperature discharge rate of each pouch cell was tested, specifically as follows: at 25°C, each pouch cell was charged at a constant current of 0.7C to 4.53V, then charged at a constant voltage of 4.53V to a cutoff current of 0.05C, and then discharged at 0.2C to 1.5V. In the subsequent 2nd to 5th cycles, the above charge-discharge process was repeated, with the discharge rate increased from 0.2C to 0.5C, 1C, 1.5C, and 2C respectively. The discharge capacity at different discharge rates was recorded, and discharge rate curves were plotted. Figure 8 summarizes the room temperature discharge rate curves of the pouch cells made using the composite negative electrode material of Example 1 and Comparative Example 1. The discharge rate performance of the batteries was measured by the ratio of the 2C discharge capacity to the 0.2C discharge capacity, and the results are summarized in Table 1 below.

[0140] The room temperature cycling performance of the above-mentioned pouch batteries was tested, specifically as follows: at 25°C, each pouch battery was charged at a constant current of 0.5C to 4.53V, then charged at a constant voltage of 4.53V to a cutoff current of 0.05C, and then discharged at 0.5C to 1.5V. This cycle was repeated, and the discharge capacity at different numbers of cycles was recorded. The ratio of the discharge capacity after n cycles to the discharge capacity of the first cycle was taken as the capacity retention rate after n cycles. The results are summarized in Table 1 below. Figure 9 summarizes the room temperature cycling performance curves of the pouch batteries made using the composite negative electrode materials of Example 1 and Comparative Example 1.

[0141] Table 1

[0142] As can be seen from Table 1, compared with silicon-based materials whose surface is partially covered by amorphous carbon (Comparative Example 1), the composite anode material provided in this application embodiment achieves full coverage of the silicon-based material surface by setting a composite coating layer containing amorphous carbon and fast ion conductor material on the surface of the silicon-based material, thereby effectively improving its cycle performance and rate performance.

[0143] The above description merely illustrates exemplary embodiments of this application, and while the description is specific and detailed, it should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

[0144] In this application, "and / or" describes 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, where A and B can be singular or plural. The character " / " generally indicates that the related objects before and after it are in an "or" relationship.

[0145] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0146] Furthermore, the numerical range indicated by "-" in this application refers to the range including the values ​​before and after "-", which are respectively taken as the minimum and maximum values. In this application, expressions regarding parameter ranges, such as "greater than or equal to (≥)", "less than or equal to (≤)", "above", and "below", all include the stated number. The numerical values ​​and ranges involved in the embodiments of this application are approximate values, and may have a certain range of errors due to the influence of manufacturing processes / testing methods, etc. These errors are negligible to those skilled in the art.

[0147] It should be understood that the terms "first," "second," and various numerical designations used herein are merely for descriptive convenience and are not intended to limit the scope of this application. Furthermore, in the various embodiments of this application, the sequence numbers of the aforementioned processes do not imply a sequential order of execution; some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

Claims

1. A composite negative electrode material, characterized in that, The composite anode material includes: The core comprises one of silicon-based materials, tin-based materials, and phosphorus-based materials; The composite coating layer includes a fast electron conductor material and a fast ion conductor material, wherein the fast electron conductor material coats a portion of the surface of the core, and the fast ion conductor material covers the surface of the core that is not covered by the fast electron conductor material.

2. The composite negative electrode material as described in claim 1, characterized in that, The fast electron conductor material includes one or more of amorphous carbon, carbon nanotubes, graphene, and conductive polymers; the fast ion conductor material includes one or more of lithium silicate, sodium silicate, lithium aluminate, lithium phosphate, aluminum phosphate, oxide solid electrolyte, sulfide solid electrolyte, halide solid electrolyte, and polymer solid electrolyte.

3. The composite negative electrode material as described in claim 1 or 2, characterized in that, The fast electron conductor material is discontinuously distributed on the surface of the core; the fast ion conductor material is discontinuously distributed on the surface of the core.

4. The composite negative electrode material as described in claim 3, characterized in that, The composite coating layer includes multiple coating regions of the fast electron conductor material and multiple coating regions of the fast ion conductor material distributed alternately on the surface of the core.

5. The composite negative electrode material according to any one of claims 1-4, characterized in that, The fast ion conductor material has a coverage of 1%-50% on the core surface, and the fast electron conductor material has a coverage of 50%-99% on the core surface.

6. The composite negative electrode material according to any one of claims 1-5, characterized in that, The coating thickness of the fast electron conductor material on the core surface and the coating thickness of the fast ion conductor material on the core surface are independently in the range of 0.5 nm to 20 nm.

7. The composite negative electrode material as described in claim 6, characterized in that, The coating thickness of the fast electron conductor material on the core surface is the same as the coating thickness of the fast ion conductor material on the core surface.

8. The composite negative electrode material according to any one of claims 1-7, characterized in that, In the composite negative electrode material, the mass percentage of the composite coating layer is in the range of greater than 0% to less than or equal to 10%.

9. The composite negative electrode material according to any one of claims 1-8, characterized in that, In the composite anode material, the fast ion conductor material accounts for 0.1%-8% of the mass.

10. The composite negative electrode material according to any one of claims 1-9, characterized in that, The mass of the fast electron conductor material is 0.1%-10% of the mass of the core.

11. The composite negative electrode material according to any one of claims 1-10, characterized in that, The silicon-based material includes one or more of elemental silicon, silicon alloys, silicon oxides, and silicon-carbon composites; the tin-based material includes one or more of elemental tin, tin alloys, tin oxides, and tin-carbon composites; and the phosphorus-based material includes one or more of elemental phosphorus and phosphorus-carbon composites.

12. A method for preparing a composite negative electrode material, characterized in that, Includes the following steps: A fast electron conductor material is formed on the surface of a core material; wherein the fast electron conductor material covers a portion of the surface of the core material, and the core material includes one of silicon-based materials, tin-based materials, and phosphorus-based materials; A core material coated with the fast electron conductor material is mixed with a solution of a fast ion conductor material raw material. The resulting mixture is filtered and vacuum dried to form a fast ion conductor material on the surface of the core that is not covered by the fast electron conductor material, thus obtaining a core with a composite coating layer, i.e., obtaining a composite negative electrode material; wherein, the composite coating layer includes the fast electron conductor material and the fast ion conductor material.

13. The preparation method according to claim 12, characterized in that, The raw materials for the fast ion conductor material include aromatic hydrocarbon lithium salts, or sodium hydroxide, or lithium hydroxide, or aluminum hydroxide sol and lithium hydroxide.

14. The preparation method according to claim 12, characterized in that, The raw materials for the fast ion conductor material include one or more of lithium phosphate, aluminum phosphate, oxide solid electrolyte, sulfide solid electrolyte, halide solid electrolyte, and polymer solid electrolyte.

15. The preparation method according to any one of claims 12-14, characterized in that, The fast electron conductor material is formed on the surface of the core material by vapor deposition or solid-phase coating.

16. A negative electrode sheet, characterized in that, The negative electrode sheet includes a current collector and a negative electrode active material layer disposed on the current collector, characterized in that the negative electrode active material layer includes a composite negative electrode material as described in any one of claims 1-11, or includes a composite negative electrode material prepared by the preparation method described in any one of claims 12-15.

17. A battery, characterized in that, It includes a positive electrode, a negative electrode, and an electrolyte between the positive electrode and the negative electrode, wherein the negative electrode includes the negative electrode as described in claim 16, or the negative electrode includes a composite negative electrode material as described in any one of claims 1-11.

18. An electrical appliance, characterized in that, The electrical device includes an electrical component and a battery as described in claim 17, wherein the electrical component is connected to the battery and the battery supplies power to the electrical component.

19. An energy storage device, characterized in that, The energy storage device includes the battery as described in claim 17.

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