Negative electrode material and manufacturing method thereof, lithium ion battery

Abstract

The present invention provides an anode material and a method for manufacturing the same, and a lithium-ion battery, the anode material including a core and a composite layer located on at least a portion of the surface of the core, the core including graphite, and the composite layer including a carbonaceous material and a non-carbonaceous material. The anode material reduces the specific surface area of ​​the anode material, enhances the interfacial stability of the anode material, improves electrolyte infiltration, reduces interfacial side reactions, enhances lithium ion transmission efficiency, and further improves the electrochemical performance of the anode material through a synergistic effect between the carbonaceous material and the non-carbonaceous material.

Description

[Technical Field]

[0001] The present application relates to the technical field of anode materials, and more particularly to anode materials and methods for producing the same, and lithium ion batteries. [Background technology]

[0002] Lithium-ion batteries, with their advantages of high energy density, long cycle life, low environmental pollution, and no memory effect, are widely used in fields such as portable electronics, electric vehicles, and drones. In recent years, as the range of applications for lithium-ion batteries has expanded, performance requirements have also increased. Because the performance indicators of lithium-ion batteries are closely related to the electrode materials, further improvements in the performance of lithium-ion battery anode materials are essential. While graphite materials have been widely used commercially in the field of lithium-ion battery anode materials, they still suffer from poor compatibility with electrolytes and unstable solid electrolyte interfacial layers (SEIs). These drawbacks result in low initial Coulombic efficiency, poor dynamic transport, and persistent decline in cycle capacity. Research has shown that the electrochemical performance of graphite materials can be improved by coating and compounding graphite with various modifiers.

[0003] Currently, coating layers are primarily divided into two types: carbonaceous and non-carbonaceous. Carbonaceous coatings often use asphalt or resin as the coating precursor, which is mixed in solid or liquid phases and then carbonized at high temperatures. This converts the precursor into a soft or hard carbon material and combines it with graphite particles, reducing the specific surface area of ​​the graphite material and improving its compatibility with the electrolyte. However, the carbonized product of the asphalt or resin is still essentially a carbon material and continues to react irreversibly with the electrolyte components at low potentials, causing the interfacial layer of the graphite material to constantly decompose, repair, and rebuild, resulting in continuous battery capacity degradation.

[0004] Therefore, how to improve the interface stability of the negative electrode material and reduce the interfacial side reactions remains one of the technical challenges to be solved. Summary of the Invention

[0005] The purpose of the present application is to provide an anode material, a manufacturing method thereof, and a lithium ion battery. The anode material of the present application reduces the specific surface area of ​​the anode material, enhances the interfacial stability of the anode material, improves the infiltration of the electrolyte, reduces interfacial side reactions, enhances the lithium ion transmission efficiency, and further improves the electrochemical performance of the anode material through the synergistic effect of the carbonaceous material and the non-carbonaceous material in the composite layer.

[0006] According to a first aspect, the present application provides an anode material, the anode material including a core and a composite layer located on at least a portion of the surface of the core, the core including graphite, and the composite layer including a carbonaceous material and a non-carbonaceous material.

[0007] In some embodiments, the non-carbonaceous material is dispersed in the carbonaceous material.

[0008] In some embodiments, the general chemical formula of the non-carbonaceous material is: x B y where 1≦x≦3 and 1≦y≦5, the element A includes at least one of Li, Na, K, Ca, Mg, Al, Zn, Ti, Nb, Zr, Mo, P, Si, and B, and the element B includes at least one of B, O, F, Si, P, S, Br, and Cl.

[0009] In some embodiments, the graphite comprises at least one of natural graphite, artificial graphite, and microcrystalline graphite.

[0010] In some embodiments, the median diameter of the core is D50, and 0.5 μm≦D50≦30 μm.

[0011] In some embodiments, the mass content of elemental carbon in said graphite is ≧80%.

[0012] In some embodiments, the carbonaceous material comprises at least one of amorphous carbon and graphitic carbon.

[0013] In some embodiments, the composite layer has a thickness of 1 nm to 200 nm.

[0014] In some embodiments, the non-carbonaceous material comprises at least one of LiF, NaF, MgF2, MgO, P2O5, Al2O3, SiO2, and B2O3.

[0015] In some embodiments, the non-carbonaceous material has an average particle size G, where G≦150 nm.

[0016] In some embodiments, the mass ratio of the composite layer to the core is C, and 0.01≦C≦0.5.

[0017] In some embodiments, the mass ratio of the carbonaceous material to the non-carbonaceous material is D, and 0.1≦D≦80.

[0018] In some embodiments, the powder electrical conductivity of the core is E1, the powder electrical conductivity of the negative electrode material is E2, and the ratio of E2 to E1 is E, and 1 <E<1000である。

[0019] In some embodiments, the specific surface area of ​​the core is 6 m 2 / g~15m 2 / g.

[0020] In some embodiments, the specific surface area of ​​the negative electrode material is 1 m 2 / g~5m 2 / g.

[0021] According to a second aspect, the present application provides a method for producing a negative electrode material, the method comprising: preparing a first precursor comprising a core comprising graphite and a polymer layer formed on a surface of the core; depositing an inorganic salt on the surface of the first precursor to obtain a second precursor; and The method includes a step of carbonizing the second precursor to obtain a negative electrode material.

[0022] In some embodiments, producing the first precursor includes polymerizing a first mixed solution containing graphite and an organic molecule monomer, performing solid-liquid separation, and drying to obtain the first precursor.

[0023] In some embodiments, attaching an inorganic salt to the surface of the first precursor to obtain a second precursor includes drying a second mixed solution containing the first precursor and the inorganic salt to obtain the second precursor.

[0024] In some embodiments, the graphite comprises at least one of natural graphite, artificial graphite, and microcrystalline graphite.

[0025] In some embodiments, the median diameter of the graphite is 0.5 μm to 30 μm.

[0026] In some embodiments, the mass ratio of the graphite to the organic molecule monomer is 1:(0.01 to 0.4).

[0027] In some embodiments, the organic molecule monomer comprises at least one of aniline, styrene, fluorostyrene, hydroxyethyl acrylate, acrylate, pyrrole, vinylidene fluoride, tetrafluoroethylene, and dopamine.

[0028] In some embodiments, the first mixed solution and the second mixed solution both contain a solvent, and the solvent includes at least one of water, methanol, ethanol, acetone, N-methylpyrrolidone, and N,N-dimethylformamide.

[0029] In some embodiments, the first mixed solution further comprises an auxiliary agent.

[0030] In some embodiments, the first mixed solution further contains an auxiliary agent, and the mass concentration of the auxiliary agent in the first mixed solution is 0.01 mol / L to 4 mol / L.

[0031] In some embodiments, the first mixed solution further includes an auxiliary agent, and the auxiliary agent includes an initiator, and the initiator includes at least one of ammonium persulfate, sodium persulfate, potassium persulfate, aluminum chloride, and hydrogen peroxide.

[0032] In some embodiments, the first mixed solution further includes an auxiliary agent, and the auxiliary agent includes a catalyst, and the catalyst includes at least one of sodium hydroxide, lithium hydroxide, potassium hydroxide, aqueous ammonia, and sodium carbonate.

[0033] In some embodiments, the first mixed solution further comprises an auxiliary agent, and the auxiliary agent comprises a pH adjusting agent, and the pH adjusting agent comprises at least one of an acidic pH reagent and a basic pH reagent.

[0034] In some embodiments, the first mixed solution further comprises an auxiliary agent, the auxiliary agent comprises a pH adjuster, and the pH of the first mixed solution is 4-10.

[0035] In some embodiments, the first mixed solution further comprises an auxiliary agent, and the auxiliary agent comprises a pH adjuster, and the pH adjuster comprises at least one of hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid.

[0036] In some embodiments, the first mixed solution further includes an auxiliary agent, and the auxiliary agent includes a pH adjuster, and the pH adjuster includes at least one of lithium hydroxide, sodium hydroxide, potassium hydroxide, sodium carbonate, and sodium bicarbonate.

[0037] In some embodiments, the temperature of the polymerization reaction is between 40°C and 100°C.

[0038] In some embodiments, the polymerization reaction time is 3 hours to 48 hours.

[0039] In some embodiments, the polymerization reaction is carried out with stirring.

[0040] In some embodiments, the polymerization reaction is carried out with stirring, and the stirring speed is 50 r / min to 1000 r / min.

[0041] In some embodiments, the solid-liquid separation comprises at least one of filtration and centrifugation.

[0042] In some embodiments, the drying comprises at least one of natural evaporation, blow drying, flash drying, freeze drying, drying under protection of an inert atmosphere, and vacuum drying.

[0043] In some embodiments, the inorganic salt comprises at least one of lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium nitrate, calcium chloride, aluminum nitrate, zinc nitrate, titanium (IV) propoxide, niobium oxalate, zirconium oxide chloride, ammonium molybdate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium metasilicate, sodium borate, ammonium fluoride, titanium oxysulfate, zinc bromide, and zirconium chloride.

[0044] In some embodiments, the mass ratio of the first precursor to the inorganic salt is 1:(0.001 to 0.1).

[0045] In some embodiments, the drying comprises at least one of natural evaporation, blow drying, flash drying, freeze drying, drying under protection of an inert atmosphere, and vacuum drying.

[0046] In some embodiments, the drying temperature is between 60°C and 600°C.

[0047] In some embodiments, the drying time is 0.5 hours to 48 hours.

[0048] In some embodiments, the carbonization process is carried out in a protective atmosphere.

[0049] In some embodiments, the carbonization process is performed in a protective atmosphere, and the protective atmosphere comprises at least one of nitrogen gas, helium gas, neon gas, argon gas, and air.

[0050] In some embodiments, the temperature increase rate in the carbonization treatment is 1° C. / min to 20° C. / min.

[0051] In some embodiments, the temperature maintained during the carbonization treatment is 600°C to 2500°C.

[0052] In some embodiments, the incubation time for the carbonization treatment is 0.1 hours to 10 hours.

[0053] According to a third aspect, the present application provides a lithium-ion battery, the lithium-ion battery comprising the negative electrode material according to the first aspect or the negative electrode material produced by the method for producing the negative electrode material according to the second aspect.

[0054] Compared with the prior art, the technical solution of the present application has at least the following beneficial effects:

[0055] In the negative electrode material provided by the present application, the negative electrode material includes a core and a composite layer located on at least a portion of the surface of the core, wherein the core includes graphite, and the composite layer includes a carbonaceous material and a non-carbonaceous material. The synergistic effect of the carbonaceous material and the non-carbonaceous material in the composite layer can reduce the specific surface area of ​​the negative electrode material, improving the high-temperature storage performance of the negative electrode material and the processability of the electrode sheet; further, the interfacial stability of the negative electrode material can be improved, interfacial side reactions can be reduced, the infiltration of the electrolyte can be increased, and the lithium ion transmission efficiency can be improved, thereby improving the reversible capacity, initial efficiency, and rate performance of the negative electrode material.

[0056] In the method for producing an anode material provided by the present application, a first mixed solution containing a graphite material and an organic molecule monomer is polymerized to obtain a first precursor, and the polymer formed by polymerization of the organic molecule monomer is composited on the surface of the graphite particles to form a polymer layer, and the polymer has highly reactive functional groups. Next, a second mixed solution containing the first precursor and an inorganic salt is thoroughly mixed and then dried. The inorganic salt in the second mixed solution is hydrolyzed to form inorganic ions, and a graft reaction between the highly reactive functional groups in the polymer and the inorganic ions occurs, grafting the inorganic ions into the polymer layer on the surface of the graphite particles to obtain a second precursor. Finally, the second precursor is carbonized. After the carbonization, the organic molecules in the polymer layer are decomposed in situ into a carbonaceous material, and the inorganic ions are converted in situ into a non-carbonaceous material, forming a composite layer containing a carbonaceous material and a non-carbonaceous material on the surface of the graphite particles. The produced negative electrode material has a composite layer uniformly coated on its surface, and the synergistic effect of the carbonaceous material and non-carbonaceous material in the composite layer reduces the specific surface area of ​​the negative electrode material, improving the high-temperature storage performance of the negative electrode material and the processability of the electrode sheet; it also improves the interfacial stability of the negative electrode material, reduces interfacial side reactions, increases the infiltration of the electrolyte, improves the lithium ion transmission efficiency, and improves the reversible capacity, initial efficiency, and rate performance of the negative electrode material. [Brief explanation of the drawings]

[0057] The present application will now be further described with reference to the figures and examples. [Figure 1] 1 is a process flow chart for producing a negative electrode material provided in an example of the present application. [Figure 2] 1 is a structural schematic diagram of a negative electrode material provided in an example of the present application. [Figure 3a] FIG. 1 is a scanning electron microscope image of the negative electrode material prepared in Example 1 of the present application. [Figure 3b] 3A and 3B are scanning electron microscope images at different magnifications of the negative electrode material prepared in Example 1 of the present application. [Figure 4] FIG. 2 is a scanning electron microscope view of a cross section of the negative electrode material prepared in Example 1 of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0058] In order to better understand the technical solution of the present application, the following detailed description of the embodiments of the present application will be given with reference to the accompanying drawings.

[0059] It should be clear that the described embodiments are only some of the embodiments of the present application, but not all of the embodiments, and all other embodiments that a person skilled in the art can obtain based on the embodiments of the present application without performing any creative work fall within the scope of protection of the present application.

[0060] The terms used in the examples of this application are used only for the purpose of describing particular examples and are not intended to limit the application. As used in the examples of this application and the appended claims, the singular forms "a," "the," and "the" are intended to include the plural forms unless the context clearly dictates otherwise.

[0061] It should be understood that the term "and / or" used in this application merely describes the relationship between related objects and indicates that three relationships may exist, for example, A and / or B can indicate three cases: A exists alone, A and B exist simultaneously, and B exists alone. Also, the character " / " in this application generally indicates that the related objects before and after it are in an "or" relationship.

[0062] According to a first aspect, the present application provides a negative electrode material, and as shown in FIG. 2 , the negative electrode material includes a core and a composite layer located on at least a portion of the surface of the core, wherein the core includes graphite and the composite layer includes a carbonaceous material and a non-carbonaceous material.

[0063] In the negative electrode material provided by the present application, the negative electrode material includes a core and a composite layer located on at least a portion of the surface of the core, wherein the core includes graphite, and the composite layer includes a carbonaceous material and a non-carbonaceous material. The synergistic effect of the carbonaceous material and the non-carbonaceous material in the composite layer can reduce the specific surface area of ​​the negative electrode material, improving the high-temperature storage performance of the negative electrode material and the processability of the electrode sheet; further, the interfacial stability of the negative electrode material can be improved, interfacial side reactions can be reduced, the infiltration of the electrolyte can be increased, and the lithium ion transmission efficiency can be improved, thereby improving the reversible capacity, initial efficiency, and rate performance of the negative electrode material.

[0064] In some embodiments, the graphite comprises at least one of natural graphite, artificial graphite, and microcrystalline graphite.

[0065] In some embodiments, the median diameter of the core is D50, and is 0.5 μm≦D50≦30 μm. Specifically, D50 may be 0.5 μm, 1 μm, 3.5 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 19.7 μm, 21.3 μm, 24.5 μm, 26.1 μm, 28.4 μm, 29 μm, or 30 μm, or may be other values ​​within the above ranges, and is not limited thereto.

[0066] In some embodiments, the mass content of carbon element in the graphite is ≧80%, and specifically may be 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 98%, or 99%, or may be other values ​​within the above range, and is not limited thereto.

[0067] In some embodiments, the carbonaceous material includes at least one of amorphous carbon and graphite carbon. Specifically, the amorphous carbon includes soft carbon and hard carbon. In some embodiments, the thickness of the composite layer is 1 nm to 200 nm. Specifically, the thickness of the composite layer may be 1 nm, 2 nm, 5 nm, 10 nm, 15 nm, 30 nm, 50 nm, 80 nm, 100 nm, 110 nm, 150 nm, 180 nm, or 200 nm, etc., but is not limited thereto. If the composite layer is too thin, it is difficult for the carbonaceous material and the non-carbonaceous material to uniformly surround the surface of the graphite material, resulting in a relatively high specific surface area of ​​the anode material. If the composite layer is too thick, the lithium ion transport efficiency at the interface of the anode material decreases, causing a deterioration in the rate performance of the anode material. Therefore, by optimizing and controlling the thickness of the composite layer within the range of 1 nm to 200 nm, it is possible to reduce the specific surface area of ​​the negative electrode material, improve the high-temperature storage performance of the negative electrode material and the processing performance of the electrode sheet, and also improve the lithium ion transmission efficiency at the interface of the negative electrode material, thereby improving the initial efficiency and rate performance of the negative electrode material.

[0068] In some embodiments, the general chemical formula of the non-carbonaceous material is: x B y where 1≦x≦3 and 1≦y≦5, the element A includes at least one of Li, Na, K, Ca, Mg, Al, Zn, Ti, Nb, Zr, Mo, P, Si, and B, and the element B includes at least one of B, O, F, Si, P, S, Br, and Cl.

[0069] In some embodiments, the A element comprises at least one of Li, Na, Mg, Al, P, Si, and B; and the B element is O or F.

[0070] In some embodiments, the non-carbonaceous material is at least one of LiF, NaF, MgF2, MgO, P2O5, Al2O3, SiO2, and B2O3.

[0071] In some embodiments, the non-carbonaceous material is dispersed in the carbonaceous material. Because the carbonaceous material is formed by carbonization of the organic material, it should be understood that the non-carbonaceous material may be attached in ionic form to or within the organic material prior to carbonization, achieving a uniform composite and cross-linking to form a composite layer of alternating non-carbonaceous and carbonaceous materials.

[0072] In some embodiments, the average particle size of the non-carbonaceous material is G, and G≦150 nm, and may be, for example, 0.5 nm, 1 nm, 1.5 nm, 3.6 nm, 4.8 nm, 7 nm, 8.9 nm, 10 nm, 11.2 nm, 15 nm, 20 nm, 30 nm, 50 nm, 80 nm, 100 nm, 120 nm, 140 nm, or 150 nm, etc., and is not limited to the recited values, and other unrecited values ​​within this range also apply. If the average particle size of the non-carbonaceous material in the composite layer is too large, the non-carbonaceous material will not be uniformly distributed in the carbonaceous material, resulting in a high specific surface area of ​​the negative electrode material and poor lithium ion transport performance at the interface.

[0073] In this application, the microscopic features of the negative electrode material surface and the particle size of the non-carbonaceous material were observed using an S-4800 scanning electron microscope, a 1 μm x 1 μm region was randomly selected on a single negative electrode material particle, the particle size distribution of the non-carbonaceous material in the region was statistically analyzed, and the average particle size of the non-carbonaceous material was calculated as G.

[0074] In some embodiments, the mass ratio of the composite layer to the core is C, and 0.01≦C≦0.5. The value of C may be, for example, 0.01, 0.03, 0.07, 0.09, 0.1, 0.17, 0.25, 0.3, 0.35, 0.4, 0.42, 0.48, or 0.5, and is not limited thereto. If the value of C is too low, the content of the composite layer in the negative electrode material is low, making it difficult to form a complete and uniform coating layer on the core surface, resulting in a large specific surface area of ​​the negative electrode material. If the value of C is too high, the content of the composite layer in the negative electrode material is high, making it difficult to form a thick coating layer on the core surface, resulting in poor dynamic performance and low capacity of the negative electrode material.

[0075] In some embodiments, the mass ratio of the carbonaceous material to the non-carbonaceous material is D, and 0.1 ≤ D ≤ 80. Specifically, it may be 0.1, 0.5, 0.8, 1, 5, 10, 18, 24, 30, 35, 40, 50, 62, 74, 80, etc. Of course, it may also be other values within the above range, and is not limited here. When the D value is slightly too low, since the content of the non-carbonaceous material in the composite layer is high, it causes the specific surface area of the negative electrode material to be slightly too large. When the D value is slightly too high, since the content of the carbonaceous material in the composite layer is high, it causes the transmission efficiency of lithium ions at the interface of the negative electrode material to decrease and the rate performance of the negative electrode material to deteriorate.

[0076] In some embodiments, the powder electrical conductivity of the graphite is E1, the powder electrical conductivity of the negative electrode material is E2, the ratio of E2 to E1 is E, and 1 < E < 1000. The value of E may specifically be 1.01, 5, 10, 50, 100, 150, 200, 300, 400, 500, 600, 700, 800, 900, 1000, etc., and is not limited here. Note that the electrical conductivity of graphite refers to the powder electrical conductivity of the uncoated graphite raw material, and the powder electrical conductivity of the negative electrode material refers to the electrical conductivity of the graphite coated with the composite layer. The value of E can represent the electrical conductivity of the negative electrode material. If the value of E is too small, it is difficult to increase the electrical conductivity of the negative electrode material.

[0077] In some embodiments, the specific surface area of the core is 6 m 2 / g to 15 m 2 / g. Specifically, it is 6 m 2 / g, 6.8 m 2 / g, 7.9 m 2 / g, 8.7 m 2 / g, 9.5 m 2 / g, 10 m 2 / g, 11.3 m 2 / g, 12.4 m 2 / g, 13.5 m 2 / g, 14 m 2 / g or 15 m 2 / g, etc., and of course, other values ​​within the above ranges are also possible, and are not limited here.

[0078] In some embodiments, the specific surface area of ​​the negative electrode material is 1 m 2 / g~5m 2 / g, specifically, 1m 2 / g, 1.5m 2 / g, 2.3m 2 / g, 2.8m 2 / g, 3m 2 / g, 3.5m 2 / g, 4m 2 / g, 4.8m 2 / g or 5m 2 / g, etc., and of course, other values ​​within the above ranges are also possible, and are not limited here.

[0079] In the present application, the negative electrode material includes a core and a composite layer located on at least a part of the surface of the core, and the composite layer completely and uniformly covers the surface of the core to reduce the specific surface area of ​​the negative electrode material, so that the specific surface area of ​​the negative electrode material is reduced to 1 m 2 / g~5m 2 / g, which is advantageous for improving the high-temperature storage performance of the negative electrode material and the processability of the electrode sheet, and further advantageous for improving the cycle performance of a lithium-ion battery produced from this negative electrode material.

[0080] According to a second aspect, the present application provides a method for producing a negative electrode material, which includes the following steps S100 to S300, as shown in FIG.

[0081] In step S100, a first precursor is produced, which includes a core containing graphite and a polymer layer formed on the surface of the core.

[0082] In step S200, an inorganic salt is attached to the surface of the first precursor to obtain a second precursor.

[0083] In step S300, the second precursor is carbonized to obtain a negative electrode material.

[0084] In the method for producing an anode material provided by the present application, a first mixed solution containing a graphite material and an organic molecule monomer is polymerized to obtain a first precursor, and the polymer formed by polymerization of the organic molecule monomer is composited on the surface of the graphite particles to form a polymer layer, and highly reactive functional groups are present in the polymer layer. Next, a second mixed solution containing the first precursor and an inorganic salt is thoroughly mixed and then dried. The inorganic salt in the second mixed solution is hydrolyzed to form inorganic ions, and a graft reaction between the highly reactive functional groups in the polymer and the inorganic ions occurs, grafting the inorganic ions into the polymer layer on the surface of the graphite particles to obtain a second precursor. Finally, the second precursor is carbonized. After the carbonization process, the organic molecules in the polymer layer are decomposed in situ into a carbonaceous material, and the inorganic ions are converted in situ into a non-carbonaceous material, forming a composite layer containing a carbonaceous material and a non-carbonaceous material on the surface of the graphite particles. The surface of the produced negative electrode material has a uniformly coated composite layer, and the synergistic effect of the carbonaceous material and the non-carbonaceous material in the composite layer reduces the specific surface area of ​​the negative electrode material, improving the high-temperature storage performance of the negative electrode material and the processability of the electrode sheet; further, it improves the interfacial stability of the negative electrode material, reduces interfacial side reactions, increases the infiltration of the electrolyte, improves the lithium ion transmission efficiency, and improves the reversible capacity, initial efficiency, and rate performance of the negative electrode material.

[0085] In step S100, a first precursor is prepared, and the first precursor includes a core containing graphite and a polymer layer formed on the surface of the core.

[0086] In some embodiments, producing the first precursor includes polymerizing a first mixed solution containing a graphite material and an organic molecule monomer, performing solid-liquid separation, and drying to obtain a first precursor, wherein the first precursor includes a core and a polymer layer located on a surface of the core, and the core includes graphite.

[0087] In some embodiments, the graphite material comprises at least one of natural graphite, artificial graphite, and microcrystalline graphite.

[0088] In some embodiments, the median diameter of the graphite is 0.5 μm to 30 μm, specifically, 0.5 μm, 1 μm, 3.5 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 19.7 μm, 21.3 μm, 24.5 μm, 26.1 μm, 28.4 μm, 29 μm, 30 μm, or the like, and of course, other numerical values ​​within the above ranges are also possible, and are not limited here.

[0089] In some embodiments, the weight ratio of the graphite material to the organic monomer is 1:(0.01-0.4). Specifically, it may be 1:0.01, 1:0.05, 1:0.1, 1:0.15, 1:0.2, 1:0.25, 1:0.3, 1:0.35, or 1:0.4. The recited values ​​are not limiting, and other values ​​within the ranges not recited above also apply. Controlling the weight ratio of the graphite material to the organic monomer can reduce the situation where the polymer coating layer is too thick, which affects the capacity; and it can also reduce the situation where the polymer is too thin, which results in an incomplete polymer coating layer, which further affects the coating integrity and uniformity of the composite layer and reduces the specific surface area of ​​the anode material. In the present application, controlling the weight ratio of the graphite material to the organic monomer can ensure the formation of a uniform polymer coating layer on the surface of the graphite particles and further improve the coating uniformity between the graphite particles and the composite layer.

[0090] In some embodiments, the organic molecule monomer comprises at least one of aniline, styrene, fluorostyrene, hydroxyethyl acrylate, acrylate, pyrrole, vinylidene fluoride, tetrafluoroethylene, and dopamine.

[0091] In some embodiments, the first mixed solution and the second mixed solution both contain a solvent, and the solvent includes at least one of water, methanol, ethanol, acetone, N-methylpyrrolidone, and N,N-dimethylformamide.

[0092] In some embodiments, the first mixed solution further comprises an auxiliary agent. It should be understood that the addition of a chemical reaction auxiliary agent can promote the progress of the polymerization reaction of the organic molecule monomer.

[0093] In some embodiments, the first mixed solution further contains an auxiliary agent, and the mass concentration of the auxiliary agent in the first mixed solution is 0.01 mol / L to 4 mol / L, specifically, 0.01 mol / L, 0.05 mol / L, 0.08 mol / L, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, or 4 mol / L, etc., and of course, may be other values ​​within the above range and is not limited here.

[0094] In some embodiments, the first mixed solution further includes an auxiliary agent, and the auxiliary agent includes an initiator, and the initiator includes at least one of ammonium persulfate, sodium persulfate, potassium persulfate, aluminum chloride, and hydrogen peroxide.

[0095] In some embodiments, the first mixed solution further includes an auxiliary agent, and the auxiliary agent includes a catalyst, and the catalyst includes at least one of sodium hydroxide, lithium hydroxide, potassium hydroxide, aqueous ammonia, and sodium carbonate.

[0096] In some embodiments, the first mixed solution further includes an auxiliary agent, which includes a pH adjuster, and the pH adjuster includes at least one of an acidic pH reagent and a basic pH reagent. Specifically, the acidic pH adjuster used may be at least one of hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid, and the basic pH adjuster used may be at least one of lithium hydroxide, sodium hydroxide, potassium hydroxide, sodium carbonate, and sodium bicarbonate. The pH value of the first mixed solution here is adjusted depending on the polymerization reaction environment required by different organic molecule monomers.

[0097] In some embodiments, the first mixed solution further includes an auxiliary agent, which includes a pH adjuster, and the pH of the first mixed solution is 4 to 10, and specifically may be 4, 5, 6, 7, 8, 9, or 10, etc., and is not limited to the listed values, and other unlisted values ​​within this range also apply.

[0098] In some embodiments, the temperature of the polymerization reaction is 40° C. to 100° C. Specifically, the temperature of the polymerization reaction may be 40° C., 45° C., 50° C., 55° C., 60° C., 70° C., 80° C., 90° C., 100° C., or the like, and is not limited thereto.

[0099] In some embodiments, the polymerization reaction time is 3 hours to 48 hours, and specifically may be 3 hours, 5 hours, 8 hours, 12 hours, 15 hours, 18 hours, 20 hours, 24 hours, 30 hours, 36 hours, 40 hours, 45 hours, or 48 hours, etc., and of course may be other values ​​within the above range and are not limited thereto.

[0100] In some embodiments, the polymerization reaction is carried out with stirring, and the polymer formed by polymerization of the organic molecule monomer wraps around the surface of the graphite to form a polymer layer.

[0101] In the present invention, by controlling the temperature and time of the polymerization reaction, the amount of chemical reaction aid added, etc., it is possible to promote a sufficient polymerization reaction of organic monomer molecules, and the polymer formed by polymerization under stirring can be more uniformly wrapped around the surface of graphite.

[0102] In some embodiments, the polymerization reaction is carried out with stirring, and the stirring speed is 50 r / min to 1000 r / min, specifically, 50 r / min, 100 r / min, 200 r / min, 300 r / min, 400 r / min, 500 r / min, 800 r / min, 1000 r / min, etc., and of course, other values ​​within the above range are also possible and are not limited thereto. Controlling the stirring speed within the above range is advantageous for allowing the polymer produced by the polymerization reaction to wrap more uniformly around the surface of the graphite.

[0103] In some embodiments, the polymerization reaction is carried out under ultraviolet irradiation. It should be understood that ultraviolet irradiation can promote the polymerization reaction of organic molecule monomers. In some embodiments, the solid-liquid separation comprises at least one of filtration and centrifugation. In step S200, an inorganic salt is attached to the surface of the first precursor to obtain a second precursor.

[0104] In some embodiments, attaching an inorganic salt to the surface of the first precursor to obtain a second precursor includes drying a second mixed solution containing the first precursor and the inorganic salt to obtain the second precursor.

[0105] In some embodiments, the inorganic salt comprises at least one of lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium nitrate, calcium chloride, aluminum nitrate, zinc nitrate, titanium (IV) propoxide, niobium oxalate, zirconium chloride oxide, ammonium molybdate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium metasilicate, sodium borate, ammonium fluoride, titanium oxysulfate, zinc bromide, and zirconium chloride.

[0106] In some embodiments, the mass ratio of the first precursor to the inorganic salt is 1:(0.001 to 0.1), specifically, 1:0.001, 1:0.003, 1:0.005, 1:0.01, 1:0.02, 1:0.05, 1:0.06, 1:0.09, or 1:0.1. The mass ratio is not limited to the recited values, and other unrecited values ​​within this range also apply. Controlling the mass ratio of the first precursor to the inorganic salt can control the mass ratio of the carbonaceous material to the non-carbonaceous material in the composite layer, thereby reducing the situation in which the carbonaceous material content in the composite layer is too high, resulting in a slightly large specific surface area of ​​the negative electrode material; and can also reduce the situation in which the non-carbonaceous material content in the composite layer is too high, resulting in a decrease in lithium ion transport efficiency at the interface of the negative electrode material and a deterioration in the rate performance of the negative electrode material. By controlling the mass ratio of the first precursor to the inorganic salt, the present application can ensure that the anode material has a low specific surface area, and further improve the lithium ion transmission efficiency at the interface of the anode material, thereby improving the rate performance of the anode material.

[0107] In some embodiments, the drying means comprises at least one of natural evaporation, blow drying, flash drying, freeze drying, drying under protection of an inert atmosphere, and vacuum drying.

[0108] In some embodiments, the drying temperature is 60°C to 600°C, and specifically may be 60°C, 100°C, 200°C, 300°C, 400°C, 500°C, or 600°C, etc., and of course may be other values ​​within the above range, and is not limited thereto.

[0109] In some embodiments, the drying time is 0.5 hours to 48 hours, and specifically may be 0.5 hours, 1 hour, 5 hours, 10 hours, 12 hours, 15 hours, 18 hours, 24 hours, 36 hours, 45 hours, or 48 hours, etc., and of course may be other values ​​within the above range and is not limited thereto.

[0110] In step S300, the second precursor is carbonized to obtain a negative electrode material.

[0111] In some embodiments, the carbonization is performed in a protective atmosphere, which may include at least one of nitrogen gas, helium gas, neon gas, argon gas, and air. It should be understood that using nitrogen gas, helium gas, neon gas, argon gas, or the like as a protective atmosphere during the carbonization process can effectively inhibit the oxidation of the graphite material, reduce the risk of the graphite material being burned at high temperatures, and ensure stability and uniformity during the carbonization process. Furthermore, during low-temperature heat treatment, such as at temperatures below 700°C, using air can promote beneficial phase transitions in the surface state of the graphite material, attach oxygen-containing functional groups to the surface of the graphite material, improve the electrolyte wetting and interfacial stability of the composite graphite anode material, and enhance its electrochemical performance. Therefore, by selecting an appropriate atmosphere protection method according to different application needs and carbonization conditions, the chemical composition and surface state of the graphite material can be effectively controlled, and its performance and application effects can be further adjusted.

[0112] In some embodiments, the temperature rise rate in the carbonization treatment is 1°C / min to 20°C / min, and specifically may be 1°C / min, 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, 12°C / min, 15°C / min, 18°C / min, or 20°C / min, or may be any other value within the above range, and is not limited thereto.

[0113] In some embodiments, the temperature for the carbonization treatment is 600°C to 2500°C, and specifically may be 600°C, 800°C, 900°C, 1000°C, 1200°C, 1500°C, 1800°C, 2000°C, 2200°C, 2300°C, or 2500°C, or may be any other value within the above range, and is not limited thereto.

[0114] In some embodiments, the incubation time for the carbonization treatment is 0.1 hours to 10 hours, and specifically may be 0.1 hours, 0.5 hours, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours, or may be any other value within the above range, and is not limited thereto.

[0115] According to a third aspect, the present application provides a lithium-ion battery, the lithium-ion battery comprising the negative electrode material according to the first aspect or the negative electrode material produced by the method for producing the negative electrode material according to the second aspect.

[0116] Example Example 1 (1) 100 g of natural graphite was taken and dispersed in 200 ml of deionized water, and 5 g of aniline monomer was added thereto, followed by thorough stirring until the mixture became homogeneous, thereby forming a first mixed solution. (2) The first mixed solution was stirred at 45°C, and 15 ml of ammonium persulfate aqueous solution (having a concentration of 2 mol / L) was added dropwise thereto while controlling the stirring speed at 300 r / min. After the addition was completed, the mixture was stirred continuously for 120 minutes to carry out a polymerization reaction, filtered, and oven-dried to obtain a first precursor, which included a core and polyaniline located on the surface of the core, and the core included natural graphite. (3) 100 g of the first precursor and 200 ml of deionized water were mixed uniformly, and then 2.5 g of LiOH.HO was added and stirred until uniform to form a second mixed solution. The second mixed solution was stirred at 90°C to evaporate the solvent, and then dried to obtain the second precursor. (4) The second precursor was heated to 1250°C in a nitrogen gas atmosphere and then carbonized for 4 hours to obtain a negative electrode material. The negative electrode material produced in this example included a core and a composite layer located on at least a portion of the surface of the core, the composite layer including hard carbon and lithium oxide (LiO), and the core including natural graphite. FIG. 3a is a scanning electron microscope image of the negative electrode material prepared in Example 1, and FIG. 3b is a scanning electron microscope image of the negative electrode material prepared in Example 1 at a different magnification. As shown in FIGS. 3a and 3b, the surfaces of the particles of the negative electrode material prepared in Example 1 contained a co-composite of carbonaceous material and non-carbonaceous material nanoparticles, and were generally smooth. FIG. 4 is a scanning electron microscope image of the cross section of the negative electrode material prepared in Example 1. As shown in FIG. 4, the thickness of the composite layer of the negative electrode material prepared in Example 1 was about 60 nm.

[0117] Example 2 (1) 100 g of natural graphite was taken and dispersed in 200 ml of deionized water, and 5 g of aniline monomer was added thereto, followed by thorough stirring until the mixture became homogeneous, thereby forming a first mixed solution. (2) The first mixed solution was stirred at 45°C, and 15 ml of ammonium persulfate aqueous solution (having a concentration of 2 mol / L) was added dropwise thereto while controlling the stirring speed at 300 r / min. After the addition was completed, the mixture was stirred continuously for 120 minutes to carry out a polymerization reaction, filtered, and oven-dried to obtain a first precursor, which included a core and polyaniline located on the surface of the core, and the core included natural graphite. (3) 100 g of the first precursor and 200 ml of deionized water were taken and mixed uniformly, and then 7.5 g of (NH4)2HPO4 was added and stirred until uniform to form a second mixed solution. The second mixed solution was stirred at 90°C to evaporate the solvent, and then dried to obtain the second precursor. (4) The second precursor was heated to 1250°C in a nitrogen gas atmosphere and then carbonized for 4 hours to obtain a negative electrode material. The negative electrode material produced in this example included a core and a composite layer located on at least a portion of the surface of the core, the composite layer including hard carbon and diphosphorus pentoxide (PO), the core including natural graphite, and the thickness of the composite layer was approximately 55 nm.

[0118] Example 3 (1) 100 g of natural graphite was taken and dispersed in 200 ml of deionized water, and 5 g of aniline monomer was added thereto, followed by thorough stirring until the mixture became homogeneous, thereby forming a first mixed solution. (2) The first mixed solution was stirred at 45°C, and 15 ml of ammonium persulfate aqueous solution (having a concentration of 2 mol / L) was added dropwise thereto while controlling the stirring speed at 300 r / min. After the addition was completed, the mixture was stirred continuously for 120 minutes to carry out a polymerization reaction, filtered, and oven-dried to obtain a first precursor, which included a core and polyaniline located on the surface of the core, and the core included natural graphite. (3) 100 g of the first precursor and 200 ml of deionized water were taken and mixed uniformly, and then 7.5 g of NHF was added and stirred until uniform to form a second mixed solution. The second mixed solution was stirred at 90°C to evaporate the solvent, and then dried to obtain a second precursor. (4) The second precursor was heated to 1250°C in a nitrogen gas atmosphere and then carbonized for 4 hours to obtain a negative electrode material. The negative electrode material produced in this example included a core and a composite layer located on at least a portion of the surface of the core, the composite layer including hard carbon and fluorocarbon (CF), the core including natural graphite, and the thickness of the composite layer was 65 nm. It should be noted that the fluorocarbon (CF4) in the composite layer of this example was a carbon material doped with fluorine, that is, the fluorocarbon (CF4) in the composite layer contained a carbonaceous material and a non-carbonaceous material.

[0119] Example 4 (1) 100 g of natural graphite was taken and dispersed in 200 ml of ethanol, and 10 g of styrene monomer was added thereto, followed by thorough stirring until the mixture became homogeneous, thereby forming a first mixed solution. (2) The first mixed solution was continuously stirred at 65°C for 120 minutes to carry out a polymerization reaction, and the stirring speed was controlled to 400 r / min. The solution was filtered and oven-dried to obtain a first precursor, which included a core and polystyrene located on the surface of the core, and the core included natural graphite. (3) 100 g of the first precursor and 200 ml of deionized water were mixed uniformly, and then 2.5 g of LiOH.HO was added and stirred until uniform to form a second mixed solution. The second mixed solution was stirred at 90°C to evaporate the solvent, and then dried to obtain the second precursor. (4) The second precursor was heated to 1250°C in a nitrogen gas atmosphere and then carbonized for 4 hours to obtain a negative electrode material. The negative electrode material produced in this example included a core and a composite layer located on at least a portion of the surface of the core, the composite layer including hard carbon and lithium oxide (LiO), the core including natural graphite, and the thickness of the composite layer was 55 nm.

[0120] Example 5 (1) 100 g of natural graphite was dispersed in 200 ml of ethanol, and 10 g of fluorostyrene monomer was added thereto, followed by thorough stirring until the mixture became homogeneous, thereby forming a first mixed solution. (2) The first mixed solution was continuously stirred at 65°C for 120 minutes to carry out a polymerization reaction, and the stirring speed was controlled to 500 r / min. The solution was filtered and oven-dried to obtain a first precursor, which included a core and polyfluorostyrene located on the surface of the core, and the core included natural graphite. (3) 100 g of the first precursor and 200 ml of deionized water were mixed uniformly, and then 2.5 g of LiOH.HO was added and stirred until uniform to form a second mixed solution. The second mixed solution was stirred at 90°C to evaporate the solvent, and then dried to obtain the second precursor. (4) The second precursor was heated to 1250°C in a nitrogen gas atmosphere and then carbonized for 4 hours to obtain a negative electrode material. The negative electrode material produced in this example included a core and a composite layer located on at least a portion of the surface of the core. The composite layer included hard carbon, lithium fluoride (LiF), and lithium oxide (LiO). The core included natural graphite. The thickness of the composite layer was 55 nm.

[0121] Example 6 (1) 100 g of natural graphite was taken and dispersed in 200 ml of ethanol, and 10 g of dopamine monomer was added thereto, followed by thorough stirring until the mixture became homogeneous, thereby forming a first mixed solution. (2) The first mixed solution was continuously stirred at 65°C for 180 minutes to carry out a polymerization reaction, and the stirring speed was controlled to 500 r / min. The solution was filtered and oven-dried to obtain a first precursor, which included a core and polydopamine located on the surface of the core, and the core included natural graphite. (3) 100 g of the first precursor and 200 ml of deionized water were mixed uniformly, and then 2.5 g of LiOH.HO was added and stirred until uniform to form a second mixed solution. The second mixed solution was stirred at 90°C to evaporate the solvent, and then dried to obtain the second precursor. (4) The second precursor was heated to 1250°C in a nitrogen gas atmosphere and then carbonized for 4 hours to obtain a negative electrode material. The negative electrode material produced in this example included a core and a composite layer located on at least a portion of the surface of the core, the composite layer including soft carbon and lithium oxide (LiO), the core including graphite, and the thickness of the composite layer was 60 nm.

[0122] Example 7 (1) 100 g of natural graphite was taken and dispersed in 200 ml of deionized water, and 5 g of dopamine was added thereto, followed by thorough stirring until the mixture became homogeneous, thereby forming a first mixed solution. (2) The first mixed solution was stirred at 40°C, and 15 ml of ammonia water (having a concentration of 4 mol / L) was added dropwise as a polymerization catalyst while controlling the stirring speed at 300 r / min. After the addition was completed, the mixture was stirred continuously for 120 minutes to carry out a polymerization reaction, filtered, and oven-dried to obtain a first precursor. The first precursor included a core and polydopamine located on the surface of the core, and the core included natural graphite. (3) 100 g of the first precursor and 200 ml of deionized water were mixed uniformly, and then 2.5 g of LiOH.HO was added and stirred until uniform to form a second mixed solution. The second mixed solution was stirred at 90°C to evaporate the solvent, and then dried to obtain the second precursor. (4) The second precursor was heated to 1250°C in a nitrogen gas atmosphere and then carbonized for 4 hours to obtain a negative electrode material. The negative electrode material produced in this example included a core and a composite layer located on at least a portion of the surface of the core, the composite layer including hard carbon and lithium oxide (LiO), the core including artificial graphite, and the thickness of the composite layer was 50 nm.

[0123] Example 8 The differences from Example 1 are as follows: (3) 100 g of the first precursor and 200 ml of deionized water were mixed uniformly, and then 24.5 g of Al(NO3)3·9H2O was added and stirred until uniform to form a second mixed solution. The second mixed solution was stirred at 90°C to evaporate the solvent, and then dried to obtain the second precursor. The negative electrode material produced in this example included a core and a composite layer located on at least a portion of the surface of the core, the composite layer including hard carbon and aluminum oxide (Al2O3), the core including graphite, and the thickness of the composite layer was 100 nm.

[0124] Example 9 The differences from Example 1 are as follows: natural graphite was replaced with artificial graphite of the same particle size distribution, and other process parameters were completely the same as those in Example 1. The negative electrode material produced in this example included a core and a composite layer located on at least a portion of the surface of the core, the composite layer including hard carbon and lithium oxide (LiO), the core including artificial graphite, and the thickness of the composite layer was 70 nm.

[0125] Example 10 The differences from Example 1 are as follows: (4) The second precursor was heated to 2000° C. in an argon gas atmosphere, and then carbonized for 4 hours to obtain a negative electrode material. The negative electrode material produced in this example included a core and a composite layer located on at least a portion of the surface of the core, the composite layer including hard carbon and lithium oxide (LiO), the core including natural graphite, and the thickness of the composite layer was 150 nm.

[0126] Example 11 The differences from Example 1 are as follows: (4) The second precursor was heated to 1600° C. in an argon gas atmosphere, and then carbonized for 4 hours to obtain a negative electrode material. The negative electrode material produced in this example included a core and a composite layer located on at least a portion of the surface of the core, the composite layer including hard carbon and lithium oxide (LiO), the core including natural graphite, and the thickness of the composite layer was 120 nm.

[0127] Example 12 The differences from Example 1 are as follows: (1) 100 g of natural graphite was taken and dispersed in 200 ml of deionized water, and 5 g of aniline monomer was added, followed by thorough stirring until homogeneous to form a first mixed solution, and a phosphoric acid solution was added to adjust the pH of the first mixed solution to 4.5. The negative electrode material produced in this example included a core and a composite layer located on at least a portion of the surface of the core, the composite layer including hard carbon and lithium oxide (LiO), and the core including natural graphite.

[0128] Example 13 The differences from Example 1 are as follows: (1) 100 g of natural graphite was taken and dispersed in 200 ml of deionized water, and 5 g of aniline monomer was added, followed by thorough stirring until homogeneous to form a first mixed solution, and sodium hydroxide solution was added to adjust the pH of the first mixed solution to 8.5. The negative electrode material produced in this example included a core and a composite layer located on at least a portion of the surface of the core, the composite layer including hard carbon and lithium oxide (LiO), and the core including natural graphite.

[0129] Comparative Example 1 (1) 100 g of natural graphite was taken and dispersed in 200 ml of deionized water, and 5 g of aniline monomer was added thereto, followed by thorough stirring until the mixture became homogeneous, to form a mixed solution. (2) The mixed solution was stirred at 45°C, and 15 ml of ammonium persulfate aqueous solution (concentration: 2 mol / L) was added dropwise thereto while controlling the stirring speed at 500 r / min. After the addition, the solution was continuously stirred for 120 min to carry out a polymerization reaction. The solution was then filtered and oven-dried to obtain a precursor, which included a core and polyaniline located on the surface of the core, and the core included natural graphite. (3) The precursor was heated to 1250°C under a nitrogen gas atmosphere and then carbonized for 4 hours to obtain the negative electrode material. The negative electrode material produced in this comparative example included a core and a carbon coating layer located on at least a portion of the surface of the core, and the core included natural graphite.

[0130] Comparative Example 2 (1) 100 g of natural graphite material was taken and mixed uniformly with 200 ml of deionized water, and 2.5 g of LiOH.HO was added and stirred until uniform, forming a mixed solution. The mixed solution was then stirred at 90 °C and evaporated to dryness to obtain a precursor. (3) The precursor was heated to 1250°C under a nitrogen gas atmosphere and then carbonized for 4 hours to obtain the negative electrode material. The negative electrode material produced in this comparative example included a core and a lithium oxide coating layer located on at least a portion of the surface of the core, and the core included graphite.

[0131] Comparative Example 3 (1) Similar to Example 9, 100 g of artificial graphite was taken and dispersed in 200 ml of deionized water, and 5 g of aniline monomer was added, followed by thorough stirring until homogeneous to form a mixed solution. (2) The mixed solution was stirred at 45°C, and the stirring speed was controlled to 300 r / min. Then, 15 ml of ammonium persulfate aqueous solution (concentration: 2 mol / L) was added dropwise thereto. After the addition was completed, the mixture was stirred continuously for 120 min to carry out a polymerization reaction. The mixture was then filtered and oven-dried to obtain a precursor. The precursor contained a core and polyaniline located on the surface of the core, and the core contained artificial graphite. (3) The precursor was heated to 1250°C under a nitrogen gas atmosphere and then carbonized for 4 hours to obtain the negative electrode material. The negative electrode material produced in this comparative example included a core and a carbon coating layer located on at least a portion of the surface of the core, and the core included artificial graphite.

[0132] Measurement method (1)Measuring method for the average particle size of negative electrode material: The particle size distribution range of the negative electrode material was measured using a Malvern laser granulometer. (2) Measurement method for the specific surface area of ​​the negative electrode material: The amount of gas adsorbed on a solid surface was measured at constant and low temperatures under different relative pressures, and then the specific surface area of ​​the material was calculated by determining the monolayer adsorption amount of the sample based on the Brunauer-Emmett-Teller adsorption theory and its formula (BET formula). (3) Observation of the surface smoothness of negative electrode material particles: The micromorphology of the surface of the negative electrode material was observed using an S-4800 scanning electron microscope. (4) Method for measuring the average particle size of non-carbonaceous materials: The microscopic morphology of the negative electrode material surface and the particle size of the non-carbonaceous material were observed using an S-4800 scanning electron microscope. A 1 μm x 1 μm area was randomly selected on a single negative electrode material particle, and the particle size distribution of the non-carbonaceous material in the area was statistically analyzed, and the average particle size of the non-carbonaceous material was calculated as G. (5) Measurement method for composite layer thickness: The graphite particles were cut using a focused ion beam to obtain cross sections, and the microscopic features of the cross sections of the anode material and the thickness of the composite layer were observed using an S-4800 scanning electron microscope. (6) Measurement of powder electrical conductivity: The powder electrical conductivity of the negative electrode material was measured using a powder resistivity measurement system. (7) Measurement of electrochemical performance For the negative electrode materials prepared in Examples 1 to 13 and Comparative Examples 1 to 3, the negative electrode materials, carboxymethyl cellulose, and styrene-butadiene rubber were dissolved in deionized water in a mass ratio of 96.5:1.5:1 to adjust the solid content to 50%. The mixture was applied to a copper foil current collector and dried in a vacuum oven to obtain a negative electrode sheet. A lithium metal sheet was used as the counter electrode, and button-type batteries were assembled in an argon-filled glove box. Charge-discharge measurements were performed at a current density of 0.1 C over a charge-discharge range of 0.01 to 1.5 V. Cycle charging and discharging was performed to obtain the first reversible specific capacity, first cycle charge capacity, and first cycle discharge capacity. The first coulombic efficiency = first cycle discharge capacity / first cycle charge capacity. Cycle charging and discharging was performed at different rates to obtain the rate performance.

[0133] The results of the above performance measurements are shown in detail in Table 1. Table 1 shows the negative electrode materials produced in each example and comparative example and the performance parameters of the batteries produced therefrom.

[0134] [Table 1]

[0135] As shown in Table 1, in Examples 1 to 13, a first mixed solution containing a graphite material and an organic molecule monomer was polymerized to obtain a first precursor. The polymer formed by the polymerization of the organic molecule monomer was composited on the surface of the graphite particles to form a polymer layer, and the polymer had a highly reactive functional group. Next, the first precursor was thoroughly mixed with a second mixed solution containing an inorganic salt, and then the mixture was dried. During the drying process, the inorganic salt in the second mixed solution was hydrolyzed to form inorganic ions. The highly reactive functional groups in the polymer reacted with the inorganic ions to graft the inorganic ions onto the polymer layer on the surface of the graphite particles, thereby obtaining a second precursor. Finally, the second precursor was carbonized. After the carbonization process, the organic molecules in the polymer layer were decomposed in situ into a carbonaceous material, and the inorganic ions were converted in situ into a non-carbonaceous material, forming a composite layer containing a carbonaceous material and a non-carbonaceous material on the surface of the graphite particles. The surface of the produced negative electrode material has a uniformly coated composite layer, and the synergistic effect of the carbonaceous material and non-carbonaceous material in the composite layer reduces the specific surface area of ​​the negative electrode material, improving the high-temperature storage performance of the negative electrode material and the processability of the electrode sheet; further, it improves the interfacial stability of the negative electrode material, reduces interfacial side reactions, increases the infiltration of electrolyte, improves the lithium ion transmission efficiency, improves the reversible capacity and initial efficiency of the negative electrode material, and improves the rate performance of the negative electrode material.

[0136] Compared with Example 1, the anode material of Comparative Example 1 was produced by directly carbonizing the first precursor during the manufacturing process. The coating layer of the produced anode material was a single carbon coating layer, which was prone to irreversible reactions with the electrolyte components at low potentials. This resulted in the SEI film constantly undergoing repair and formation, reducing the interfacial stability of the anode material and causing severe side reactions with the electrolyte, resulting in a decrease in the lithium ion transmission efficiency, a decrease in the powder electrical conductivity of the anode material, and a decrease in the reversible capacity, initial efficiency, and rate performance of the material.

[0137] Compared with Example 1, the negative electrode material of Comparative Example 2 was produced by directly combining natural graphite material with a non-carbonaceous material during the manufacturing process. The coating layer of the produced negative electrode material was a single non-carbonaceous material coating layer, and the specific surface area of ​​the negative electrode material was relatively large, which increased the contact between the material and the electrolyte, resulting in severe interfacial side reactions, reduced interfacial stability of the material, and reduced lithium ion transmission efficiency. As a result, the powder electrical conductivity of the negative electrode material decreased, and its reversible capacity and rate performance also decreased, and the initial efficiency also decreased significantly.

[0138] In Example 9 and Comparative Example 3, artificial graphite was used as the raw material. Compared to Example 9, the negative electrode material in Comparative Example 3 was produced by directly carbonizing the first precursor during the manufacturing process. The coating layer of the produced negative electrode material was a single carbon coating layer, and the surface stability of the negative electrode material was relatively low. The side reaction with the electrolyte was more severe at low potential, and the performance indicators such as the initial Coulombic efficiency, powder electrical conductivity, and rate performance were all deteriorated to different degrees.

[0139] Although the present application has described the detailed process equipment and process flow of the present application through the above examples, the applicant declares that the present application is not limited to the above detailed process equipment and process flow, that is, the present application is not limited to the above detailed process equipment and process flow. As is obvious to those skilled in the art, any improvements to the present application, such as equivalent replacement of each raw material of the product of the present application, addition of auxiliary components, and selection of specific methods, are all within the scope of protection and disclosure of the present application.

[0140] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority from a Chinese patent application filed with the China Patent Office on September 27, 2023, bearing application number 202311279012.8 and entitled "Negative electrode material and manufacturing method thereof, for lithium ion batteries," the entire contents of which are incorporated herein by reference.

Claims

1. A negative electrode material, The negative electrode material includes a core and a composite layer located on at least a portion of the surface of the core, the core including graphite, and the composite layer including a carbonaceous material and a non-carbonaceous material.

2. 2. The negative electrode material according to claim 1, wherein the non-carbonaceous material is dispersed in the carbonaceous material.

3. The general chemical formula of the non-carbonaceous material is: ｘ B ｙ 2. The negative electrode material according to claim 1, wherein 1≦x≦3 and 1≦y≦5, the A element includes at least one of Li, Na, K, Ca, Mg, Al, Zn, Ti, Nb, Zr, Mo, P, Si, and B, and the B element includes at least one of B, O, F, Si, P, S, Br, and Cl.

4. 2. The negative electrode material according to claim 1, wherein the negative electrode material satisfies at least one of the following technical features: (1) The graphite includes at least one of natural graphite, artificial graphite, and microcrystalline graphite; (2) The median diameter of the core is D50, and 0.5 μm≦D50≦30 μm; (3) The mass content of carbon element in the graphite is ≧80%; (4) The carbonaceous material includes at least one of amorphous carbon and graphite carbon; (5) The thickness of the composite layer is 1 nm to 200 nm; (6) The non-carbonaceous material is LiF, NaF, or MgF ２ , MgO, P ２ O ５ , Al ２ O ３ , SiO ２ , B ２ O ３ Contains at least one of: (7) The non-carbonaceous material has an average particle size G, and G≦150 nm.

5. 4. The negative electrode material according to claim 1, wherein the negative electrode material satisfies at least one of the following technical features: (1) the mass ratio of the composite layer to the core is C, and 0.01≦C≦0.5; (2) the mass ratio of the carbonaceous material to the non-carbonaceous material is D, and 0.1≦D≦80; (3) The electrical conductivity of the core powder is E １ and the powder electrical conductivity of the negative electrode material is E ２ and E ２ and E １ the ratio of E to 1000; (4) The specific surface area of ​​the core is 6 m ２ / g to 15m ２ / g; (5) The specific surface area of ​​the negative electrode material is 1 m ２ / g to 5m ２ / g.

6. preparing a first precursor comprising a core comprising graphite and a polymer layer formed on a surface of the core; depositing an inorganic salt on the surface of the first precursor to obtain a second precursor; and a step of carbonizing the second precursor to obtain a negative electrode material.

7. Producing the first precursor comprises:

7. The method according to claim 6, further comprising the steps of polymerizing a first mixed solution containing graphite and an organic molecule monomer, performing solid-liquid separation, and drying to obtain the first precursor.

8. 7. The manufacturing method according to claim 6, wherein obtaining the second precursor by adhering an inorganic salt to the surface of the first precursor includes a step of drying a second mixed solution containing the first precursor and the inorganic salt to obtain the second precursor.

9. 8. The method according to claim 7, wherein at least one of the following technical features is satisfied: (1) The graphite includes at least one of natural graphite, artificial graphite, and microcrystalline graphite; (2) The median diameter of the graphite is 0.5 μm to 30 μm; (3) The mass ratio of the graphite to the organic molecule monomer is 1:(0.01-0.4); (4) The organic molecule monomer includes at least one of aniline, styrene, fluorostyrene, hydroxyethyl acrylate, acrylate, pyrrole, vinylidene fluoride, tetrafluoroethylene, and dopamine; (5) The first mixed solution and the second mixed solution both contain a solvent, and the solvent contains at least one of water, methanol, ethanol, acetone, N-methylpyrrolidone, and N,N-dimethylformamide.

10. 8. The method according to claim 7, wherein at least one of the following technical features is satisfied: (1) The first mixed solution further contains an auxiliary; (2) The first mixed solution further contains an auxiliary agent, and the mass concentration of the auxiliary agent in the first mixed solution is 0.01 mol / L to 4 mol / L; (3) The first mixed solution further contains an auxiliary agent, the auxiliary agent contains an initiator, and the initiator contains at least one of ammonium persulfate, sodium persulfate, potassium persulfate, aluminum chloride, and hydrogen peroxide; (4) The first mixed solution further contains an auxiliary agent, and the auxiliary agent contains a catalyst, and the catalyst contains at least one of sodium hydroxide, lithium hydroxide, potassium hydroxide, ammonia water, and sodium carbonate; (5) The first mixed solution further contains an auxiliary agent, and the auxiliary agent contains a pH adjusting agent, and the pH adjusting agent contains at least one of an acidic pH reagent and a basic pH reagent; (6) The first mixed solution further contains an auxiliary agent, the auxiliary agent contains a pH adjuster, and the pH of the first mixed solution is 4 to 10; (7) The first mixed solution further contains an auxiliary agent, and the auxiliary agent contains a pH adjuster, and the pH adjuster contains at least one of hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid; (8) The first mixed solution further contains an auxiliary agent, and the auxiliary agent contains a pH adjuster, and the pH adjuster contains at least one of lithium hydroxide, sodium hydroxide, potassium hydroxide, sodium carbonate, and sodium bicarbonate.

11. 8. The method according to claim 7, wherein at least one of the following technical features is satisfied: (1) The temperature of the polymerization reaction is 40°C to 100°C; (2) The polymerization reaction time is 3 hours to 48 hours; (3) The polymerization reaction is carried out with stirring; (4) The polymerization reaction is carried out under stirring, and the stirring speed is 50 r / min to 1000 r / min; (5) The solid-liquid separation includes at least one of filtration and centrifugation.

12. 9. The method according to claim 8, wherein at least one of the following technical features is satisfied: (1) The inorganic salt includes at least one of lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium nitrate, calcium chloride, aluminum nitrate, zinc nitrate, titanium (IV) propoxide, niobium oxalate, zirconium chloride oxide, ammonium molybdate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium metasilicate, sodium borate, ammonium fluoride, titanium oxysulfate, zinc bromide, and zirconium chloride; (2) the mass ratio of the first precursor to the inorganic salt is 1:(0.001-0.1); (3) The drying includes at least one of natural evaporation, air drying, flash drying, freeze drying, drying under protection of an inert atmosphere, and vacuum drying; (4) The drying temperature is 60°C to 600°C; (5) The drying time is 0.5 hours to 48 hours; (6) The carbonization treatment is carried out in a protective atmosphere; (7) The carbonization treatment is performed in a protective atmosphere, and the protective atmosphere contains at least one of nitrogen gas, helium gas, neon gas, argon gas, and air; (8) The temperature rising rate in the carbonization treatment is 1°C / min to 20°C / min; (9) The temperature for the carbonization treatment is 600°C to 2500°C; (10) The heat retention time for the carbonization treatment is 0.1 to 10 hours.

13. A lithium ion battery comprising the negative electrode material according to any one of claims 1 to 5 or the negative electrode material produced by the method for producing the negative electrode material according to any one of claims 6 to 12.

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