Carbon material, negative electrode material and battery

Abstract

A carbon material, a negative electrode material and a battery. The carbon material has pores; the total pore volume of the carbon material is 0.5 cm3 / g to 1.6 cm3 / g; and the crushing strength of the carbon material is U1 kN / cm2, and 0.05≤U1≤0.3. The carbon material has a suitable porosity, and can provide enough accommodating space for a silicon material and relieve the volume expansion of the silicon material; moreover, the crushing strength of the carbon material can be controlled within a suitable range to enable the carbon material to have a good structural stability, and therefore the collapse and fragmentation of the structure of the carbon material caused by volume expansion during lithium intercalation and deintercalation can be reduced, side reactions can be decreased, and the capacity and cycle performance of the negative electrode material can be improved.

Description

Carbon materials, negative electrode materials and batteries

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed on December 28, 2023, with application number 202311853136.2 and entitled “Carbon materials, negative electrode materials, preparation methods thereof, and batteries”. Technical Field

[0003] The present invention relates to the technical field of negative electrode materials, and in particular to carbon materials, negative electrode materials and batteries. Background Art

[0004] Lithium-ion batteries have the advantages of high energy density, long cycle life, low environmental pollution, and no memory effect. Therefore, they are widely used in electric vehicles and consumer electronics. Currently, commercial lithium-ion batteries mainly use graphite-based anode materials, but their theoretical capacity in lithium-ion batteries is only 372mAh / g, which can no longer meet the current demand for high capacity and high energy density of lithium-ion batteries. In order to improve the energy density of lithium-ion batteries, people have begun to search for high-capacity anode materials. Silicon-based anode materials have attracted attention due to their theoretical specific capacity of up to 4200mAh / g and are considered to have the most development potential for lithium-ion battery anode materials.

[0005] However, silicon undergoes huge volume changes during the process of lithium extraction / insertion, which can easily lead to the pulverization of silicon particles and subsequent detachment from the current collector. The repeated changes in the volume of silicon-based negative electrode materials during the electrochemical cycle cause the solid electrolyte interface (SEI film) formed on the surface of the silicon-based negative electrode material to be continuously destroyed and regenerated, resulting in continuous consumption of lithium ions, and ultimately leading to rapid capacity decay. Based on the above shortcomings of silicon, people have begun to study silicon and carbon composite materials, among which the research results of carbon-coated silicon composite materials are quite fruitful. Carbon materials coated on the surface of silicon particles can alleviate the huge volume changes of silicon-based negative electrode materials, build a conductive network, improve the conductive performance, and to a certain extent suppress the volume expansion of crystalline silicon, but cannot fundamentally solve the problem.

[0006] Compared with crystalline silicon, amorphous silicon materials have smaller volume expansion, which can reduce the volume expansion of silicon-carbon composite materials. During the synthesis process, amorphous silicon-carbon materials retain some pores of porous carbon, which has a certain buffering effect on the volume expansion of silicon-carbon composite materials. However, the large number of pores will lead to a decrease in the structural stability of the silicon-carbon composite material, and the material will be easily broken, resulting in poor material performance.

[0007] Therefore, how to suppress the volume expansion of silicon-based negative electrode materials and improve the structural stability of negative electrode materials is a problem that still needs to be solved.

[0008] Summary of the Invention

[0009] The present application provides a carbon material, a negative electrode material and a battery. The carbon material of the present application has suitable pores, which can provide sufficient accommodation space for silicon material and alleviate the volume expansion of silicon material. At the same time, the crushing strength of the carbon material is controlled within a suitable range, so that the carbon material has excellent structural stability, which can reduce the collapse and breakage of the carbon material structure caused by volume expansion during the lithium insertion and extraction process, reduce the occurrence of side reactions, and improve the capacity and cycle performance of the negative electrode material.

[0010] In a first aspect, the present application provides a carbon material having pores, wherein the total pore volume of the carbon material is 0.5 cm 3 / g~1.6cm 3 / g, the crushing strength of the carbon material is U1kN / cm 2 , 0.05≤U1≤0.3.

[0011] In some embodiments, the pores in the carbon material include open pores and closed pores, and the carbon material includes at least one of the following characteristics:

[0012] (1) The volume ratio of closed pores in the carbon material to the total pore volume is A%, 1.0≤A≤5.0;

[0013] (2) the volume ratio of the open pores in the carbon material to the total pore volume is B%, 95.0≤B≤99.0;

[0014] (3) The pores in the carbon material include micropores, mesopores and macropores, wherein the volume proportion of the micropores in the total pore volume is 60% to 97%.

[0015] In some embodiments, the carbon material includes at least one of biomass-based porous carbon, synthetic polymer-based porous carbon, and tar coal-based porous carbon.

[0016] In a second aspect, the present application provides a negative electrode material, the negative electrode material comprising a carbon material and a silicon material, the carbon material having pores, at least part of the silicon material being distributed within the pores of the carbon material; the total pore volume of the negative electrode material after removing the silicon material is 0.5 cm 3 / g~1.6cm 3 / g, crushing strength is U1kN / cm 2 , 0.05≤U1≤0.3.

[0017] In some embodiments, the pores in the carbon material include open pores and closed pores, and the carbon material includes at least one of the following characteristics:

[0018] (1) The volume ratio of closed pores in the carbon material to the total pore volume is A%, 1.0≤A≤5.0;

[0019] (2) the volume ratio of the open pores in the carbon material to the total pore volume is B%, 95.0≤B≤99.0;

[0020] (3) The pores in the carbon material include micropores, mesopores and macropores, wherein the volume proportion of the micropores in the total pore volume is 60% to 97%.

[0021] In some embodiments, the carbon material includes at least one of biomass-based porous carbon, synthetic polymer-based porous carbon, and tar coal-based porous carbon.

[0022] In a third aspect, the present application provides a negative electrode material, comprising a carbon material and a silicon material, wherein the carbon material has pores, and at least a portion of the silicon material is distributed in the pores of the carbon material;

[0023] The negative electrode material has pores, including open pores and closed pores; the volume of the closed pores accounts for P1% of the volume of the negative electrode material, 0.1≤P1≤5, and the volume of the open pores accounts for P2% of the volume of the negative electrode material, 0.1≤P2≤20;

[0024] The crushing strength of the negative electrode material is U2kN / cm 2 , 0.35≤U2≤1.5.

[0025] In some embodiments, the negative electrode material includes at least one of the following features:

[0026] (1) The total pore volume of the negative electrode material after removing the silicon material is 0.3 cm 3 / g~1.5cm 3 / g;

[0027] (2) The pores in the negative electrode material after removing the silicon material include micropores, mesopores and macropores, wherein the volume proportion of the micropores in the total pore volume is 50% to 90%;

[0028] (3) After removing the silicon material, the closed pores in the negative electrode material account for 3.0% to 6.0% of the total pore volume;

[0029] (4) After the silicon material is removed, the volume ratio of the open pores in the negative electrode material to the total pore volume is 94.0% to 97.0%.

[0030] In some embodiments, the negative electrode material includes at least one of the following features:

[0031] (5) The silicon material includes at least one of amorphous silicon, crystalline silicon, silicon oxide or silicon alloy;

[0032] (6) The average particle size of the silicon material is 1 nm to 5 nm.

[0033] In some embodiments, based on 100% by mass of the negative electrode material, the mass content of the silicon element is 10% to 85%.

[0034] In some embodiments, the true density of the negative electrode material is ρg / cm 3 , 1.2≤ρ≤3.0.

[0035] In some embodiments, the total pore volume of the negative electrode material is 0.01 cm 3 / g~0.10cm 3 / g.

[0036] In some embodiments, the particle size of the negative electrode material satisfies: 1 μm ≤ D min ≤3μm, 6μm≤D 50 ≤8μm, D max ≤30μm.

[0037] In some embodiments, the specific surface area of ​​the negative electrode material is 0.8 m 2 / g~20m 2 / g.

[0038] In a fourth aspect, the present application includes a battery, comprising the carbon material described in any embodiment of the first aspect and the negative electrode material described in any embodiment of the second aspect and the third aspect.

[0039] Compared with the prior art, the technical solution of this application has at least the following beneficial effects:

[0040] The carbon material provided in this application has pores, and the total pore volume of the carbon material is 0.5 cm 3 / g~1.6cm 3 / g, the carbon material has suitable pores, and these pores can provide sufficient accommodation space for the silicon material, alleviating the volume expansion of the silicon material; and the crushing strength of the carbon material is U1kN / cm 2 , 0.05≤U1≤0.3; the crushing strength of the carbon material is related to the pores in the carbon material. The crushing strength of the carbon material is within the above range, so that the carbon material has excellent structural stability, and the carbon material after being composited with the silicon material can also have excellent structural stability, which can reduce the collapse and breakage of the carbon material structure caused by the volume expansion of the silicon material during the lithium insertion and extraction process, reduce the occurrence of side reactions, and thus improve the capacity and cycle performance of the negative electrode material.

[0041] The negative electrode material provided by the present application includes a carbon material and a silicon material. The carbon material has pores, and at least part of the silicon material is distributed in the pores of the carbon material, which can increase the capacity of the negative electrode material. At the same time, the pores are reduced after the carbon material is filled with the silicon material, which can increase the density of the negative electrode material, thereby improving the structural stability of the negative electrode material, thereby improving the cycle performance of the negative electrode material; at the same time, the negative electrode material has pores, and the pores include open pores and closed pores. The volume ratio of the closed pore volume in the negative electrode material is P1%, 0.1≤P1≤5.0, and the volume ratio of the open pore volume in the negative electrode material is P2%, 0.1≤P2≤20, and the crushing strength of the negative electrode material is U2kN / cm 2 , 0.35≤U2≤1.5. Since the volume ratio of closed pores in the negative electrode material is within the above range, there are appropriate open and closed pores inside the negative electrode material, which can improve the structural stability of the negative electrode material and the crushing strength of the negative electrode material, thereby reducing the probability of the negative electrode material breaking during the cycle and improving the cycle performance of the negative electrode material. In addition, the appropriate closed pores inside the negative electrode material can also provide a certain buffer space for the volume expansion of the silicon material, inhibiting the volume expansion of the negative electrode material, reducing the collapse and breakage of the negative electrode material structure caused by volume expansion during the lithium insertion and extraction process, and improving the cycle performance of the negative electrode material. In addition, since the volume of the pores in the negative electrode material accounts for a volume ratio in the negative electrode material within the above range, on the one hand, the silicon material is filled in the pores of the carbon material, which can increase the capacity of the negative electrode material; on the other hand, the internal pores of the carbon material are reduced after being filled with the silicon material, thereby increasing the density of the negative electrode material, improving the structural stability of the negative electrode material, and thus increasing the crushing strength of the negative electrode material. At the same time, the pores in the negative electrode material within a suitable range can also provide a certain buffer space for the volume expansion of the silicon material, inhibiting the volume expansion of the negative electrode material, thereby reducing the collapse and breakage of the negative electrode material structure caused by volume expansion during the lithium insertion and extraction process, and improving the cycle performance of the negative electrode material. In addition, the volume ratio of the pores in the negative electrode material within the above range can also reduce the contact area between the electrolyte and the negative electrode material, thereby making it difficult for the electrolyte to penetrate into the interior of the negative electrode material, thereby effectively reducing the occurrence of side reactions between the negative electrode material and the electrolyte, and improving the electrochemical performance of the negative electrode material. In summary, the present application controls the volume ratio of closed pores and open pores in the negative electrode material within a suitable range so that suitable closed pores and open pores exist in the negative electrode material, thereby improving the crushing strength of the negative electrode material through the synergistic effect between the closed pores and open pores, and finding a balance between the closed pore volume ratio, open pore volume ratio and crushing strength of the negative electrode material, thereby inhibiting the volume expansion of the negative electrode material, improving the structural stability of the negative electrode material, and further improving the electrochemical performance of the negative electrode material.

[0042] The present application also provides a method for preparing a negative electrode material, first, a mixture containing a carbon source and an activator is carbonized at 800°C to 1100°C, during the carbonization process, the carbon source is cracked in the above temperature range to form a carbon material, and at the same time, the carbon material reacts with the activator, the activator invades the interior of the carbon material, and forms a large number of pores inside the carbon material, thereby obtaining a carbon material with pores; at the same time, by controlling the reaction temperature of the above preparation process, the carbon material has a suitable pore structure, and these pore structures, after being compounded with the silicon material, can provide sufficient buffer space for the volume expansion of the silicon material, thereby inhibiting the volume expansion of the negative electrode material; at the same time, the presence of suitable pores in the carbon material can also improve the crushing strength of the carbon material and improve the structural stability of the carbon material; secondly, the carbon material prepared above is vapor-deposited using silicon source gas for 30min to 150min. During the vapor deposition process, the suitable pores in the carbon material are conducive to the silicon source gas entering the interior of the carbon material and passing through The silicon material penetrates through the pores in the carbon material into the interior of the carbon material, and the silicon material is formed inside the carbon material and is evenly filled in the pores of the carbon material to obtain an active substance, thereby increasing the capacity of the negative electrode material; at the same time, the presence of a suitable pore structure in the carbon material can also provide a certain buffer space for the volume expansion of the silicon material, and can improve the structural stability of the carbon material to a certain extent; by controlling the deposition time within the above range, on the one hand, the silicon material can be fully and evenly filled in the pores of the carbon material, which is beneficial to improving the capacity of the negative electrode material. At the same time, the appropriate filling of the silicon material can reduce some of the pores in the carbon material, thereby helping to improve the structural stability of the negative electrode material and improve the crushing strength of the negative electrode material; on the other hand, the excessive filling of the silicon material can be reduced, thereby controlling the pore structure in the negative electrode material within a suitable range, thereby providing a certain buffer space for the volume expansion of the silicon material, inhibiting the volume expansion of the negative electrode material, and improving the cycle performance of the negative electrode material. Finally, by carbon-coating the active material, direct contact between the active material and the electrolyte can be further isolated, the occurrence of side reactions on the surface of the negative electrode material can be reduced, the excessive growth of the solid electrolyte interface (SEI film) on the surface of the negative electrode material can be inhibited, the consumption of active lithium ions can be reduced, and the capacity, first efficiency and cycle performance of the negative electrode material can be further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The present invention will be further described below with reference to the accompanying drawings and examples.

[0044] FIG1 is a scanning electron microscope image of the negative electrode material prepared in Example 1 of the present application;

[0045] FIG2 is a cross-sectional view of the negative electrode material prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0046] In order to better understand the technical solution of the present invention, the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0047] It should be understood that the embodiments described are only a portion of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative work are within the scope of protection of the present invention.

[0048] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The singular forms "a", "an", "the" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0049] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0050] In a first aspect, the present application provides a carbon material having pores, and the total pore volume of the carbon material is 0.5 cm 3 / g~1.6cm 3 / g, the crushing strength of carbon material is U1kN / cm 2 , 0.05≤U1≤0.3.

[0051] The carbon material provided in this application has pores, and the total pore volume of the carbon material is 0.5 cm 3 / g~1.6cm 3 / g, the carbon material has suitable pores, and these pores can provide sufficient accommodation space for the silicon material, alleviating the volume expansion of the silicon material; and the crushing strength of the carbon material is U1kN / cm 2 , 0.05≤U1≤0.3; the crushing strength of the carbon material is closely related to the pores in the carbon material. The crushing strength of the carbon material is within the above range, so that the carbon material has excellent structural stability, and the carbon material after the composite silicon material can also have excellent structural stability, which can reduce the collapse and breakage of the carbon material structure caused by the volume expansion of the silicon material during the lithium insertion and extraction process of the silicon material, reduce the occurrence of side reactions between the carbon material after the composite silicon material and the electrolyte, and thus improve the capacity and cycle performance of the carbon material after the negative composite silicon material.

[0052] In some embodiments, the pores in the carbon material include open pores and closed pores.

[0053] In some embodiments, the volume fraction of closed pores in the carbon material in the total pore volume is A%, 1.0≤A≤5.0, specifically 1.0%, 1.2%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5% or 5.0%, etc., and of course it can also be other values ​​within the above range, which are not limited here. It can be understood that controlling the volume fraction of closed pores in the carbon material within the above range and having suitable open pores and closed pores in the carbon material is beneficial to improving the structural stability of the carbon material and improving the crushing strength of the carbon material. On the other hand, in the process of compounding the carbon material with silicon, the suitable closed pores in the carbon material can provide a certain buffer space for the volume expansion of silicon, thereby suppressing the volume expansion of the carbon material after compounding the silicon material and improving the cycle performance of the carbon material after compounding the silicon material. Preferably, the volume fraction of closed pores in the carbon material is 1.5% to 4.0%.

[0054] In some embodiments, the volume fraction of open pores in the carbon material in the total pore volume is B%, 95.0≤B≤99.0, specifically 95.0%, 95.5%, 96.0%, 96.5%, 97.0%, 98.5%, 98.6%, 98.7%, 98.8% or 99.0%, etc., and of course it can also be other values ​​within the above range, which is not limited here. It can be understood that the volume fraction of open pores in the carbon material is within the above range. In the process of compounding the carbon material and the silicon material, the silicon material can penetrate and diffuse into the interior of the carbon material through the open pores in the carbon material to fill it. On the one hand, it can increase the specific capacity of the negative electrode material. On the other hand, the pores of the carbon material after being filled with the silicon material are reduced, which can increase the density of the negative electrode material and improve the structural stability of the negative electrode material. Preferably, the volume fraction of open pores in the carbon material is 96.0% to 98.5%.

[0055] In this application, the crushing strength of the carbon material can be specifically 0.05 kN / cm 2 , 0.08kN / cm 2 , 0.1kN / cm 2 , 0.15kN / cm 2 , 0.2kN / cm 2 , 0.25kN / cm 2 or 0.3kN / cm 2 It is understood that the crushing strength of the carbon material within the above range is beneficial to improving the structural stability of the carbon material and reducing the probability of the carbon material being broken during the recycling process.

[0056] In some embodiments, the total pore volume of the carbon material is 0.5 cm 3 / g~1.6cm 3 / g, specifically 0.5cm3 / g, 0.8cm 3 / g, 1.0cm 3 / g, 1.1cm 3 / g, 1.15cm 3 / g, 1.2cm 3 / g, 1.3cm 3 / g, 1.5cm 3 / g or 1.6cm 3 / g, etc., and of course other values ​​within the above range are also possible and are not limited here. It can be understood that the carbon material has abundant pores, which can accommodate the silicon material and reserve space for the volume expansion of the silicon material, thereby alleviating the expansion effect of the negative electrode material prepared from the carbon material and improving the cycle stability of the negative electrode material prepared from the carbon material.

[0057] In some embodiments, the pores in the carbon material include micropores, mesopores and macropores, wherein the volume fraction of micropores in the total pore volume is 60% to 97%, specifically 60%, 70%, 75%, 80%, 85%, 90%, 95%, 96% or 97%, etc., and of course other values ​​within the above range can also be used, which are not limited here. It can be understood that by controlling the volume fraction of micropores in the carbon material, the adsorption capacity of the carbon material on the silicon material can be increased, the diffusion of the silicon material in the carbon material can be promoted, and the deposition uniformity of the silicon material in the carbon material can be improved, and the deposition of the silicon material on the surface of the carbon material can be reduced. The present application controls the volume fraction of micropores in the carbon material within the above range, thereby reducing the deposition of the silicon material on the surface of the carbon material during the deposition of the carbon material and the silicon material, so that the silicon material can be uniformly deposited in the pores of the carbon material rather than on the surface, thereby suppressing the volume expansion of the negative electrode material prepared from the carbon material and improving the electrochemical performance of the negative electrode material prepared from the carbon material.

[0058] In some embodiments, the carbon material includes at least one of biomass-based porous carbon, synthetic polymer-based porous carbon, and tar coal-based porous carbon.

[0059] In a second aspect, the present application provides a negative electrode material, comprising the carbon material and the silicon material of the first aspect, wherein at least a portion of the silicon material is distributed within the pores of the carbon material. That is, the negative electrode material comprises the carbon material and the silicon material, the carbon material has pores, and at least a portion of the silicon material is distributed within the pores of the carbon material; the total pore volume of the negative electrode material excluding the silicon material is 0.5 cm 3 / g~1.6cm 3 / g, crushing strength is U1kN / cm 2, 0.05≤U1≤0.3. It can be understood that the silicon material is filled in the pores of the carbon material, which can increase the capacity of the negative electrode material. At the same time, the pores of the carbon material are reduced after the silicon material is filled, which can increase the density of the negative electrode material, improve the structural stability of the negative electrode material, and thus improve the cycle performance of the battery prepared with the negative electrode material. In addition, the pores in the carbon material can also provide sufficient buffer space for the volume expansion of the silicon material, inhibit the volume expansion of the negative electrode material, reduce the collapse and fragmentation of the structure of the negative electrode material due to volume expansion during the lithium insertion and extraction process, effectively reduce the occurrence of side reactions between the negative electrode material and the electrolyte, and improve the capacity and cycle performance of the negative electrode material.

[0060] In a third aspect, the present application provides a negative electrode material, the negative electrode material comprising a carbon material and a silicon material, the carbon material having pores, and at least a portion of the silicon material being distributed in the pores of the carbon material;

[0061] The negative electrode material has pores, which include open pores and closed pores. The volume of the closed pores accounts for P1% of the volume of the negative electrode material, 0.1≤P1≤5, and the volume of the open pores accounts for P2% of the volume of the negative electrode material, 0.1≤P2≤20; and the crushing strength of the negative electrode material is U2kN / cm2, 0.35≤U2≤1.5.

[0062] The negative electrode material provided by the present application includes a carbon material and a silicon material. The carbon material has pores, and at least part of the silicon material is distributed in the pores of the carbon material, which can increase the capacity of the negative electrode material. At the same time, the pores are reduced after the carbon material is filled with the silicon material, which can increase the density of the negative electrode material, thereby improving the structural stability of the negative electrode material, and thereby improving the cycle performance of the battery prepared by the negative electrode material; at the same time, the negative electrode material has pores, and the pores include open pores and closed pores. The volume ratio of the closed pore volume in the negative electrode material is P1%, 0.1≤P1≤5.0, and the volume ratio of the open pore volume in the negative electrode material is P2%, 0.1≤P2≤20, and the crushing strength of the negative electrode material is U2kN / cm 2, 0.35≤U2≤1.5. When the volume ratio of closed pores in the negative electrode material is within the above range, the negative electrode material has appropriate open and closed pores, which can improve the structural stability of the negative electrode material and the crushing strength of the negative electrode material, thereby reducing the probability of the negative electrode material breaking during the cycle and improving the cycle performance of the negative electrode material. In addition, the appropriate closed pores in the negative electrode material can also provide a certain buffer space for the volume expansion of the silicon material, inhibiting the volume expansion of the negative electrode material, reducing the collapse and breakage of the negative electrode material structure caused by volume expansion during the lithium insertion and extraction process, and improving the cycle performance of the negative electrode material. In addition, since the volume of the openings in the negative electrode material accounts for a certain proportion of the volume of the negative electrode material in the above range, on the one hand, the silicon material is filled in the pores of the carbon material, which can increase the capacity of the negative electrode material; on the other hand, the internal pores of the carbon material are reduced after being filled with the silicon material, thereby increasing the density of the negative electrode material, improving the structural stability of the negative electrode material, and thus improving the crushing strength of the negative electrode material. At the same time, the openings in the negative electrode material within a suitable range can also provide a certain buffer space for the volume expansion of the silicon material, inhibiting the volume expansion of the negative electrode material, thereby reducing the collapse and breakage of the negative electrode material structure caused by volume expansion during the lithium insertion and extraction process, and improving the cycle performance of the negative electrode material. In addition, the volume of the openings in the negative electrode material accounts for a certain proportion of the volume of the negative electrode material in the above range, which can also reduce the contact area between the electrolyte and the negative electrode material, thereby making it difficult for the electrolyte to penetrate into the interior of the negative electrode material, effectively reducing the occurrence of side reactions between the negative electrode material and the electrolyte, and improving the electrochemical performance of the negative electrode material. In summary, the present application controls the volume ratio of closed pores and open pores in the negative electrode material within an appropriate range, so that appropriate closed pores and open pores exist in the negative electrode material, thereby improving the crushing strength of the negative electrode material through the synergistic effect between the closed pores and open pores, and finding a balance between the closed pore volume ratio, open pore volume ratio and crushing strength of the negative electrode material, thereby inhibiting the volume expansion of the negative electrode material, improving the structural stability of the negative electrode material, and further improving the electrochemical performance of the negative electrode material.

[0063] In the present application, the volume proportion of the closed-pore pore volume in the negative electrode material can be specifically 0.1%, 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, etc., and of course it can also be other values ​​within the above range, which is not limited here. It can be understood that when the volume proportion of the closed-pore pore volume in the negative electrode material is less than 0.1%, the pore space inside the negative electrode material is too small, and at this time there is not enough pore space inside the negative electrode material to withstand the volume expansion of the silicon material during the lithium insertion and extraction process; when the volume proportion of the closed-pore pore volume in the negative electrode material is greater than 5%, there are more pores inside the negative electrode material, the structural stability of the negative electrode material decreases, resulting in a decrease in the crushing strength of the negative electrode material, and the pole piece prepared from the negative electrode material is prone to breakage, cracking and other problems during the roller pressing process, resulting in poor processing performance of the negative electrode material. Therefore, by controlling the volume of closed-cell pores in the negative electrode material to between 0.1% and 5%, the present application can improve the structural stability of the negative electrode material, increase the crushing strength of the negative electrode material, effectively inhibit the volume expansion of the silicon material, reduce the expansion rate of the negative electrode material, and thus improve the cycle performance of the negative electrode material. Preferably, the volume of closed-cell pores in the negative electrode material accounts for 0.1% to 3%, more preferably 0.2% to 2%, and even more preferably 0.5% to 2%.

[0064] In the present application, the volume ratio of the pore volume of the open pores in the negative electrode material can be specifically 0.1%, 0.5%, 1%, 2%, 5%, 8%, 10%, 12%, 15%, 18% or 20%, etc., and of course it can also be other values ​​within the above range, which is not limited here. It can be understood that when the volume ratio of the pore volume of the open pores in the negative electrode material is less than 0.1%, the silicon material filled in the carbon material is too much, resulting in too little pore space inside the negative electrode material, and there is not enough pore space inside the negative electrode material to withstand the volume expansion of the silicon material during the lithium insertion and extraction process; when the volume ratio of the pore volume of the open pores in the negative electrode material is greater than 20%, on the one hand, the silicon material filled in the pores of the carbon material is too little, resulting in a low capacity of the negative electrode material; on the other hand, the presence of more pores inside the negative electrode material reduces the density of the negative electrode material and the structural stability of the negative electrode material, resulting in a decrease in the crushing strength of the negative electrode material. The electrode sheet prepared from the negative electrode material is prone to breakage, cracking and other problems during the roller pressing process, resulting in poor processing performance of the negative electrode material. In addition, the large number of open pores in the negative electrode material increases its contact area with the electrolyte, exacerbating the side reactions between the negative electrode material and the electrolyte, resulting in a decrease in the electrochemical performance of the negative electrode material. Therefore, the present application controls the volume of the open pores in the negative electrode material to between 0.1% and 20%, which, on the one hand, is beneficial to increasing the capacity of the negative electrode material; on the other hand, it can improve the structural stability of the negative electrode material and increase the crushing strength of the negative electrode material; at the same time, it can also reduce the occurrence of side reactions between the electrolyte and the negative electrode material, effectively inhibit the volume expansion of the negative electrode material, reduce the expansion rate, and thus improve the electrochemical performance of the negative electrode material. Preferably, the volume proportion of the open pores in the negative electrode material is 0.1% to 10%, and more preferably 0.2% to 5%.

[0065] The crushing strength of the negative electrode material can be specifically 0.35kN / cm 2 , 0.4kN / cm 2 , 0.5kN / cm 2 , 0.8kN / cm 2 , 1.0kN / cm 2 , 1.1kN / cm 2 , 1.2kN / cm 2 , 1.3kN / cm 2 , 1.4kN / cm 2 or 1.5kN / cm 2Etc., of course, it can also be other values ​​within the above range, which are not limited here. It can be understood that the crushing strength of the negative electrode material refers to the ability of the negative electrode material to resist crushing when subjected to external force. If the crushing strength of the negative electrode material is low, the negative electrode material is prone to crushing. The present application controls the crushing strength of the negative electrode material within the above range. The structural stability of the negative electrode material is good, and it can withstand the expansion stress generated during the insertion and removal of lithium from the silicon material, reducing the probability of the negative electrode material being broken during the cycle, thereby improving the electrochemical performance of the negative electrode material. Preferably, the crushing strength of the negative electrode material is 0.2kN / cm 2 ~1.2kN / cm 2 , further preferably, the crushing strength of the negative electrode material is 0.5kN / cm 2 ~1.0kN / cm 2 .

[0066] In some embodiments, the total pore volume of the negative electrode material after removing the silicon material is 0.3 cm 3 / g~1.5cm 3 / g, specifically 0.3cm 3 / g, 0.5cm 3 / g, 0.8cm 3 / g, 1.0cm 3 / g, 1.1cm 3 / g, 1.2cm 3 / g, 1.3cm 3 / g or 1.5cm 3 / g, etc., but are not limited to the listed values. Other values ​​not listed within this numerical range are also applicable. It can be understood that the negative electrode material after removing the silicon material has abundant pores. These pores can accommodate the silicon material and reserve space for the volume expansion of the silicon material, thereby alleviating the expansion effect of the negative electrode material and improving the cycle stability of the negative electrode material.

[0067] In some embodiments, the pores in the negative electrode material after removing the silicon material include micropores, mesopores and macropores, wherein the volume proportion of the micropores in the total pore volume is 50% to 90%, specifically 50%, 60%, 65%, 70%, 75%, 80%, 85%, 86% or 90%, etc., and of course other values ​​within the above range are also possible, which are not limited here. It can be understood that the negative electrode material after removing the silicon material is mostly carbon material. The present application controls the volume proportion of micropores in the carbon material within the above range, and then in the process of depositing the carbon material and the silicon material, it can reduce the deposition of the silicon material on the surface of the carbon material, so that the silicon material can be evenly deposited in the pores of the carbon material rather than on the surface, thereby suppressing the volume expansion of the negative electrode material and improving the electrochemical performance of the negative electrode material.

[0068] In some embodiments, the volume percentage of closed pores in the negative electrode material after the silicon material is removed is 3.0% to 6.0% of the total volume, and specifically can be 3.0%, 3.5%, 4.0%, 4.2%, 4.5%, 5.0%, 5.5% or 6.0%, etc., and of course other values ​​within the above range are also possible, and are not limited here. It can be understood that the volume percentage of closed pores in the negative electrode material after the silicon material is removed is within the above range, and the presence of suitable closed pores in the negative electrode material can improve the structural stability of the negative electrode material, improve the crushing strength of the negative electrode material, thereby reducing the probability of the negative electrode material breaking during the cycle, and improving the cycle performance of the negative electrode material.

[0069] In some embodiments, the volume proportion of the openings in the negative electrode material after removing the silicon material in the total volume is 94.0% to 97.0%, specifically 94.0%, 94.5%, 95%, 95.0%, 95.5%, 96%, 96.5% or 97%, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0070] In some embodiments, the silicon material includes at least one of amorphous silicon, crystalline silicon, silicon oxide, or a silicon alloy.

[0071] In some embodiments, the average particle size of the silicon material is 1 nm to 5 nm, specifically 1 nm, 1.5 nm, 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, or 5 nm, but is not limited to the listed values. Other values ​​not listed within this numerical range are also applicable. It can be understood that controlling the average particle size of the silicon material within this range is beneficial to improving the uniformity of the silicon material distribution within the pores of the carbon material, which is beneficial to suppressing the volume expansion of the negative electrode material, and is beneficial to improving the capacity and cycle performance of the negative electrode material.

[0072] In some embodiments, based on the mass of the negative electrode material being 100%, the mass percentage of silicon is 10% to 85%, specifically 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 82%, 83%, or 85%, etc., and other values ​​within the above range are also possible, without limitation herein. It is understood that controlling the mass content of silicon in the negative electrode material within the above range is beneficial to increasing the capacity of the negative electrode material, suppressing the volume expansion of the negative electrode material, improving the structural stability of the negative electrode material, and thereby improving the cycle performance of the negative electrode material.

[0073] In some embodiments, the negative electrode material further includes a carbon layer located on at least a portion of its surface.

[0074] In some embodiments, the negative electrode material further includes a carbon layer located on at least a portion of its surface, wherein the carbon layer includes amorphous carbon. It is understood that the carbon layer on the surface of the negative electrode material can further isolate the negative electrode material from direct contact with the electrolyte, effectively reducing the occurrence of side reactions between the negative electrode material and the electrolyte, inhibiting excessive growth of the solid electrolyte interface (SEI) film on the surface of the negative electrode material, reducing the consumption of active lithium ions, and further improving the capacity, initial efficiency, and cycle performance of the negative electrode material.

[0075] In some embodiments, the negative electrode material further includes a carbon layer located on at least a portion of its surface. The thickness of the carbon layer is 5 nm to 500 nm, specifically 5 nm, 10 nm, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, or 500 nm, but is not limited to these values. Other values ​​not listed within this range are also applicable. Preferably, the thickness of the carbon layer is 10 nm to 100 nm.

[0076] In some embodiments, the true density of the negative electrode material is pg / cm 3 , 1.2≤ρ≤3.0. The true density of the negative electrode material can be specifically 1.2g / cm 3 , 1.3g / cm 3 , 1.5g / cm 3 , 1.8g / cm 3 , 2.0g / cm 3 , 2.1g / cm 3 , 2.5g / cm 3 , 2.8g / cm 3 or 3.0g / cm 3 It is understandable that controlling the true density of the negative electrode material within the above range is beneficial to improving the energy density of the battery made of the negative electrode material.

[0077] In some embodiments, the total pore volume of the negative electrode material is 0.01 cm 3 / g~0.10cm 3 / g, specifically 0.01cm 3 / g, 0.02cm 3 / g, 0.05cm 3 / g, 0.06cm 3 / g, 0.07cm 3 / g, 0.08cm 3 / g or 0.10cm 3 / g, etc., but are not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0078] In some embodiments, the particle size of the negative electrode material satisfies: 1 μm ≤ D min≤3μm, 6μm≤D 50 ≤8μm, D max ≤30μm.

[0079] Specifically, the particle size D of the negative electrode material min It can be 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2 μm, 2.3 μm, 2.5 μm or 3 μm, etc., which is not limited here; the particle size D of the negative electrode material 50 It can be 6μm, 6.2μm, 6.5μm, 6.8μm, 7μm, 7.3μm, 7.5μm or 8μm, etc., which is not limited here; the particle size D of the negative electrode material max It can be 1μm, 3μm, 5μm, 8μm, 10μm, 15μm, 18μm, 20μm, 25μm or 30μm, etc., and is not limited here.

[0080] In some embodiments, the specific surface area of ​​the negative electrode material is 0.8 m 2 / g~20m 2 / g, specifically 0.8m 2 / g, 1.0m 2 / g、5m 2 / g、8m 2 / g、10m 2 / g、12m 2 / g、14m 2 / g、15m 2 / g、16m 2 / g、18m 2 / g or 20m 2 / g, etc., and of course, other values ​​within the above range can also be used, which are not limited here. It can be understood that controlling the specific surface area of ​​the negative electrode material within the above range is beneficial to improving the cycle performance of the battery made of the negative electrode material.

[0081] In a fourth aspect, the present application provides a method for preparing a negative electrode material, comprising the following steps:

[0082] Step S10: carbonizing the mixture containing the carbon source and the activator at 800°C to 1100°C to obtain a carbon material having pores; wherein the total pore volume of the carbon material is 0.5 cm 3 / g~1.6cm 3 / g, the crushing strength of carbon material is U1kN / cm 2 , 0.05≤U1≤0.3;

[0083] Step S20, performing vapor deposition on the porous carbon material using a silicon source gas for 30 minutes to 150 minutes to obtain an active material;

[0084] Step S30 , performing carbon coating treatment on the active material to obtain a negative electrode material.

[0085] The present application provides a method for preparing a negative electrode material, which first carbonizes a mixture containing a carbon source and an activator at 800°C to 1100°C. During the carbonization process, the carbon source is cracked in the above temperature range to form a carbon material, and the carbon material reacts with the activator. The activator invades the interior of the carbon material and forms a large number of pores inside the carbon material to obtain a carbon material with pores. At the same time, by controlling the reaction temperature of the above preparation process, the carbon material has a suitable pore structure. After being compounded with the silicon material, these pore structures can provide sufficient buffer space for the volume expansion of the silicon material, thereby inhibiting the volume expansion of the negative electrode material. At the same time, the presence of suitable pores in the carbon material can also improve the crushing strength of the carbon material and improve the structural stability of the carbon material. Secondly, the carbon material prepared above is vapor-deposited using silicon source gas for 30min to 150min. During the vapor deposition process, the carbon material has suitable pores, which is conducive to the silicon source gas entering the interior of the carbon material. The silicon source gas penetrates into the interior of the carbon material through the pores in the carbon material, and forms silicon material inside the carbon material that is uniformly filled in the pores of the carbon material to obtain active substances, thereby increasing the capacity of the negative electrode material; at the same time, there is a suitable pore structure in the carbon material, which can provide a certain buffer space for the volume expansion of the silicon material, and can also improve the structural stability of the carbon material to a certain extent; by controlling the deposition time within the above range, on the one hand, the silicon material can be fully and uniformly filled in the pores of the carbon material, which is beneficial to improving the capacity of the negative electrode material. At the same time, the appropriate filling of the silicon material can reduce some of the pores in the carbon material, thereby helping to improve the structural stability of the negative electrode material and improve the crushing strength of the negative electrode material; on the other hand, it can reduce the overfilling of the silicon material, and can control the pore structure in the negative electrode material within a suitable range, thereby providing a certain buffer space for the volume expansion of the silicon material, inhibiting the volume expansion of the negative electrode material, and improving the cycle performance of the negative electrode material. Finally, by carbon-coating the active material, direct contact between the active material and the electrolyte can be further isolated, the occurrence of side reactions on the surface of the negative electrode material can be reduced, the excessive growth of the solid electrolyte interface (SEI film) on the surface of the negative electrode material can be inhibited, the consumption of active lithium ions can be reduced, and the capacity, first efficiency and cycle performance of the negative electrode material can be further improved.

[0086] The preparation method of the present application is described in detail below with reference to the examples:

[0087] Step S10: carbonizing the mixture containing the carbon source and the activator at 800°C to 1100°C to obtain a carbon material having pores; wherein the total pore volume of the carbon material is 0.5 cm 3 / g~1.6cm 3 / g, the crushing strength of carbon material is U1kN / cm 2 , 0.05≤U1≤0.3.

[0088] In the present application, the temperature of the carbonization treatment can specifically be 800°C, 850°C, 900°C, 950°C, 1000°C or 1100°C, etc., and is not limited here. It can be understood that during the carbonization treatment process, the activation effect of the activator increases with the increase of the carbonization temperature. The higher the carbonization temperature, the better the activation effect of the activator, the more complete the activation of the carbon material, and the smaller the proportion of closed pores in the carbon material. By controlling the carbonization temperature within the above range, the present application can achieve the regulation of the specific pore volume ratio and the open pore volume ratio in the carbon material, and then prepare a carbon material with a suitable open pore and closed pore volume ratio.

[0089] In some embodiments, before step S10, the method further includes placing the carbon source at 200° C. to 300° C. for a pre-activation treatment for 3 h to 5 h.

[0090] Specifically, the temperature of the pre-activation treatment can be 200°C, 230°C, 250°C, 260°C, 280°C, or 300°C, etc., and is not limited here; the time of the pre-activation treatment can be 3 hours, 3.5 hours, 4 hours, 4.5 hours, 4.6 hours, 4.8 hours, or 5 hours, etc., and is not limited here. It can be understood that pre-activating the carbon source can increase the reactivity of the carbon source, increase the reaction efficiency between the carbon source and the activator, and promote the carbonization reaction; at the same time, pre-activating the carbon source can also remove impurities on the surface of the carbon source.

[0091] In some embodiments, the carbonization treatment time is 1 h to 10 h, specifically 1 h, 2 h, 3 h, 5 h, 6 h, 8 h, 9 h or 10 h, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0092] In some embodiments, the carbon source includes at least one of lignin, coconut shell, coal tar, phenolic resin, starch, glucose, and rice hull.

[0093] In some embodiments, the activator includes at least one of potassium hydroxide and sodium hydroxide.

[0094] In some embodiments, the mass ratio of the carbon source to the activator is (5:1) to (1:10), specifically 5:1, 5:1.5, 5:5, 5:6, 5:10, 1:1, 1:1.5, 1:2, 1:5, 1:10, etc., which is not limited here.

[0095] In some embodiments, the carbonization product is further subjected to acid washing and water washing until the pH value is 6.5 to 7.5, followed by solid-liquid separation, drying and sieving to obtain a carbon material having pores.

[0096] In some embodiments, the pores in the carbon material include micropores, mesopores and macropores, wherein the volume proportion of the micropores in the total pore volume is 60% to 97%, specifically 60%, 70%, 75%, 80%, 85%, 90%, 95%, 96% or 97%, etc., and of course it can also be other values ​​within the above range, which are not limited here. It can be understood that by controlling the volume proportion of micropores in the carbon material, the adsorption capacity of the carbon material on the silicon material can be increased, the diffusion of the silicon material in the carbon material can be promoted, and the deposition uniformity of the silicon material in the carbon material can be improved, and the deposition of the silicon material on the surface of the carbon material can be reduced. The present application controls the volume proportion of the micropores in the carbon material within the above range, thereby reducing the deposition of the silicon material on the surface of the carbon material during the deposition of the carbon material and the silicon material, so that the silicon material can be uniformly deposited in the pores of the carbon material rather than on the surface, thereby suppressing the volume expansion of the negative electrode material and improving the electrochemical performance of the negative electrode material.

[0097] In some embodiments, the carbon material includes at least one of biomass-based porous carbon, synthetic polymer-based porous carbon, and tar coal-based porous carbon.

[0098] In some embodiments, the total pore volume of the carbon material is 0.5 cm 3 / g~1.6cm 3 / g, specifically 0.5cm 3 / g, 0.8cm 3 / g, 1.0cm 3 / g, 1.1cm 3 / g, 1.15cm 3 / g, 1.2cm 3 / g, 1.3cm 3 / g, 1.5cm 3 / g or 1.6cm 3 / g, etc., and of course other values ​​within the above range are also possible and are not limited here. It can be understood that the carbon material has abundant pores, which can accommodate the silicon material and reserve space for the volume expansion of the silicon material, thereby alleviating the expansion effect of the negative electrode material and improving the cycle stability of the battery prepared with the negative electrode material.

[0099] In some embodiments, the pores in the carbon material include open pores and closed pores.

[0100] In some embodiments, the volume fraction of closed pores in the carbon material in the total pore volume is A%, 1.0≤A≤5.0, and specifically can be 1.0%, 1.2%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5% or 5.0%, etc., and of course it can also be other values ​​within the above range, which is not limited here. It can be understood that controlling the volume fraction of closed pores in the carbon material within the above range and having appropriate open and closed pores in the carbon material is beneficial to improving the structural stability of the carbon material and improving the crushing strength of the carbon material. On the other hand, in the process of compounding the carbon material with silicon, the appropriate closed pores in the carbon material can provide a certain buffer space for the volume expansion of silicon, thereby suppressing the volume expansion of the negative electrode material and improving the cycle performance of the negative electrode material. Preferably, the volume fraction of closed pores in the carbon material is 1.5% to 4.0%.

[0101] In some embodiments, the volume fraction of open pores in the carbon material in the total pore volume is B%, 95.0≤B≤99.0, specifically 95.0%, 95.5%, 96.0%, 96.5%, 97.0%, 98.5%, 98.6%, 98.7%, 98.8% or 99.0%, etc., and of course it can also be other values ​​within the above range, which is not limited here. It can be understood that the volume fraction of open pores in the carbon material is within the above range. In the process of compounding the carbon material with silicon, silicon can penetrate and diffuse into the interior of the carbon material through the open pores in the carbon material for filling. On the one hand, it can increase the specific capacity of the negative electrode material. On the other hand, the pores of the carbon material after being filled with silicon material are reduced, which can increase the density of the negative electrode material and improve the structural stability of the negative electrode material. Preferably, the volume fraction of open pores in the carbon material is 96.0% to 98.5%.

[0102] Step S20 , performing vapor deposition on the porous carbon material using silicon source gas for 30 minutes to 150 minutes to obtain an active material.

[0103] In some embodiments, the silicon source gas includes at least one of monosilane, disilane, dimethylsilane, dichlorosilane, trichlorosilane, and silicon tetrachloride.

[0104] In some embodiments, the temperature of vapor deposition is 400°C to 600°C, specifically 400°C, 450°C, 500°C, 520°C, 550°C, 560°C or 600°C, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0105] In some embodiments, the heating rate of vapor deposition is 1°C / min to 10°C / min, specifically 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 or 10°C / min, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0106] In some embodiments, vapor deposition is performed under a protective atmosphere.

[0107] In some embodiments, vapor deposition is performed under a protective atmosphere comprising at least one of nitrogen, argon, helium, neon, krypton, and xenon.

[0108] In some embodiments, vapor deposition is carried out under a protective atmosphere, and the flow ratio of silicon source gas to protective atmosphere is (2:1): (1:4), specifically 2:1, 2:1.5, 2:2, 2:3, 2:4, 1:1, 1:1.5, 1:2, 1:3, 1:4, etc., which are not limited here.

[0109] Step S30 , performing carbon coating treatment on the active material to obtain a negative electrode material.

[0110] In some embodiments, the carbon coating process includes at least one of a vapor phase carbon coating process, a liquid phase carbon coating process, and a solid phase carbon coating process.

[0111] In some embodiments, the carbon coating treatment step specifically includes: heating the active material, introducing a carbon source gas and a protective gas, and thermally cracking the carbon source gas to obtain a negative electrode material.

[0112] In some embodiments, the carbon coating treatment step specifically includes: heating the active material, introducing a carbon source gas and a protective gas, and thermally cracking the carbon source gas to obtain a negative electrode material; wherein the carbon source gas is at least one of methane, ethylene, acetylene, ethane, propane, propylene, propyne, butane, cyclohexane and carbon dioxide.

[0113] In some embodiments, the carbon coating treatment step specifically includes: heating the active material, introducing a carbon source gas and a protective gas, and thermally cracking the carbon source gas to obtain a negative electrode material; wherein the protective gas includes at least one of nitrogen, argon, helium, neon, krypton and xenon.

[0114] In some embodiments, the carbon coating treatment step specifically includes: heating the active material, introducing a carbon source gas and a protective gas, and thermally cracking the carbon source gas to obtain a negative electrode material; wherein the flow ratio of the carbon source gas and the protective gas is (1:20) to (1:2), and specifically can be 1:1, 1:1.5, 1:2, 20:1, 20:1.5, 20:2, etc., which is not limited here.

[0115] In some embodiments, the carbon coating treatment step specifically includes: heating the active material, introducing a carbon source gas and a protective gas, and thermally cracking the carbon source gas to obtain a negative electrode material; wherein the thermal cracking temperature is 600°C to 800°C, and the thermal cracking time is 30min to 150min.

[0116] Specifically, the thermal cracking temperature can be 600°C, 650°C, 700°C, 750°C, 760°C, 780°C or 800°C, etc., which is not limited here; the thermal cracking time can be 30min, 45min, 60min, 70min, 80min, 100min, 120min or 150min, etc., which is not limited here.

[0117] In some embodiments, the carbon coating step specifically includes: carbonizing a mixture obtained by mixing the active material with a liquid carbon source to obtain a negative electrode material.

[0118] In some embodiments, the step of carbon coating treatment specifically includes: carbonizing the mixture obtained by mixing the active substance with the liquid carbon source to obtain a negative electrode material; wherein the mass ratio of the liquid carbon source to the active substance is (1:2) to (1:20) 1:1, 1:5, 1:10, 1:15, 1:20, 2:1, 2:5, 2:10, 2:15, 2:20, etc., which is not limited here.

[0119] In some embodiments, the carbon coating step specifically includes: carbonizing a mixture obtained by mixing the active substance with a liquid carbon source to obtain a negative electrode material; wherein the liquid carbon source includes at least one of n-hexane, toluene, benzene, xylene, methanol, ethanol, propanol, butanol, pentanol, acetone, butanone, 2-pentanone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate and pentyl acetate.

[0120] In some embodiments, the carbon coating step specifically includes: carbonizing the mixture obtained by mixing the active substance with the liquid carbon source to obtain a negative electrode material; wherein the carbonization temperature is 600°C to 900°C, and the carbonization time is 1h to 5h.

[0121] Specifically, the temperature of carbonization treatment can be 600℃, 650℃, 700℃, 750℃, 760℃, 800℃ or 900℃, etc., which is not limited here; the time of thermal cracking can be 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h or 5h, etc., which is not limited here.

[0122] In some embodiments, the carbon coating step specifically includes: carbonizing a mixture obtained by mixing the active material with a solid carbon source to obtain a negative electrode material.

[0123] In some embodiments, the carbon coating step specifically includes: carbonizing the mixture obtained by mixing the active substance with the solid carbon source to obtain the negative electrode material, wherein the carbonization temperature is 600°C to 900°C, and the carbonization time is 1h to 5h.

[0124] Specifically, the temperature of carbonization treatment can be 600℃, 650℃, 700℃, 750℃, 760℃, 800℃ or 900℃, etc., which is not limited here; the time of thermal cracking can be 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h or 5h, etc., which is not limited here.

[0125] In some embodiments, a mixture obtained by mixing an active substance with a solid carbon source is carbonized to obtain a negative electrode material, wherein the solid carbon source includes at least one of sugars, esters, hydrocarbons, organic acids and high molecular polymers.

[0126] In some embodiments, the carbon coating step specifically includes: carbonizing a mixture obtained by mixing the active substance with a solid carbon source to obtain a negative electrode material, wherein the solid carbon source includes at least one of polyvinyl chloride, polyvinyl butyral, polyacrylonitrile, polyacrylic acid, polyethylene glycol, polypyrrole, polyaniline, sucrose, glucose, maltose, citric acid, asphalt, furfural resin, epoxy resin and phenolic resin.

[0127] In some embodiments, the carbon coating step specifically includes: carbonizing the mixture obtained by mixing the active material with the solid carbon source to obtain the negative electrode material, wherein the mass ratio of the solid carbon source to the active material is (1:1): (1:10).

[0128] In some embodiments, the method further comprises shaping, screening and demagnetizing the carbon-coated product to obtain a negative electrode material.

[0129] In some embodiments, the method further comprises shaping, screening and demagnetizing the carbon-coated product to obtain a negative electrode material; wherein the shaping comprises at least one of crushing, pulverizing, gas crushing or grinding.

[0130] In a fifth aspect, the present application includes a lithium-ion battery, which includes the above-mentioned negative electrode material or the negative electrode material prepared by the above-mentioned preparation method.

[0131] Example 1

[0132] (1) Weigh 50 g of lignin and place it in a preheating furnace for preactivation treatment at 300 °C for 3 h to obtain preactivated lignin.

[0133] (2) Weigh 30 g of the above-mentioned preactivated lignin and 15 g of potassium hydroxide, grind and mix them evenly to obtain a mixture; place the mixture in a vacuum box furnace, heat it to 800° C., and keep the temperature constant for 3 hours.

[0134] (3) The carbonized product is acid-washed and water-washed to a pH of 7.0, and then filtered, dried, and sieved to obtain a porous carbon material.

[0135] (4) Weigh 4 g of the above-mentioned carbon material and place it in a tube furnace. Raise the temperature to 460°C at a rate of 5°C / min, introduce disilane and nitrogen into the tube furnace at a flow ratio of 1:2, and maintain the temperature for 60 minutes to obtain an active material. Then, raise the temperature to 650°C at a rate of 5°C / min, introduce propane and nitrogen into the tube furnace at a flow ratio of 2:7, and maintain the temperature for 30 minutes.

[0136] (5) The obtained sample is crushed, sieved, and demagnetized to obtain the negative electrode material.

[0137] The negative electrode material prepared in this embodiment includes a carbon material and a silicon material. The carbon material has pores, including open pores and closed pores. At least part of the silicon material is distributed in the pores of the carbon material. The carbon material is a biomatrix porous carbon, the silicon material is amorphous silicon, and the average particle size of the silicon material is 3.8 nm. The D of the negative electrode material is 1.34 nm. min 2.1μm, D 50 8.5μm, D max It is 24.0μm.

[0138] The parameters of the carbon material in this embodiment are detailed in Table 1.

[0139] The parameters of the negative electrode material after removing the silicon material in this embodiment are detailed in Table 2.

[0140] The parameters of the negative electrode material in this embodiment are detailed in Table 3.

[0141] FIG1 is a scanning electron microscope image of the negative electrode material prepared in Example 1 of the present application.

[0142] FIG2 is a cross-sectional view of the negative electrode material prepared in Example 1 of the present application. As shown in FIG2 , the negative electrode material has pores, and at least part of the silicon is filled in the pores of the carbon material.

[0143] Example 2

[0144] The difference from Example 1 is that the constant temperature time for vapor deposition of disilane and carbon material in step (4) is 30 minutes, and the other conditions are exactly the same as those in Example 1.

[0145] The negative electrode material prepared in this embodiment includes a carbon material and a silicon material. The carbon material has pores, including open pores and closed pores. At least part of the silicon material is distributed in the pores of the carbon material. The carbon material is a biomatrix porous carbon, the silicon material is amorphous silicon, and the average particle size of the silicon material is 2.4 nm. The D of the negative electrode material is 2.4 nm. min 2.1μm, D 50 8.5μm, D max It is 24.0μm.

[0146] The parameters of the carbon material in this embodiment are detailed in Table 1.

[0147] The parameters of the negative electrode material after removing the silicon material in this embodiment are detailed in Table 2.

[0148] The parameters of the negative electrode material in this embodiment are detailed in Table 3.

[0149] Example 3

[0150] The difference from Example 1 is that the constant temperature time for vapor deposition of disilane and carbon material in step (4) is 70 minutes, and the other conditions are exactly the same as those in Example 1.

[0151] The negative electrode material prepared in this embodiment includes a carbon material and a silicon material. The carbon material has pores, including open pores and closed pores. At least part of the silicon material is distributed in the pores of the carbon material. The carbon material is a biomatrix porous carbon, the silicon material is amorphous silicon, and the average particle size of the silicon material is 3.8 nm. The D of the negative electrode material is 1.34 nm. min 2.1μm, D 50 8.5μm, D max It is 24.0μm.

[0152] The parameters of the carbon material in this embodiment are detailed in Table 1.

[0153] The parameters of the negative electrode material after removing the silicon material in this embodiment are detailed in Table 2.

[0154] The parameters of the negative electrode material in this embodiment are detailed in Table 3.

[0155] Example 4

[0156] The difference from Example 1 is that the constant temperature time for vapor deposition of disilane and carbon material in step (4) is 80 minutes, and the other conditions are exactly the same as those in Example 1.

[0157] The negative electrode material prepared in this embodiment includes a carbon material and a silicon material. The carbon material has pores, including open pores and closed pores. At least part of the silicon material is distributed in the pores of the carbon material. The carbon material is a biomatrix porous carbon, the silicon material is amorphous silicon, and the average particle size of the silicon material is 3.8 nm. The D of the negative electrode material is 1.34 nm. min 2.1μm, D 50 8.5μm, D max It is 24.0μm.

[0158] The parameters of the carbon material in this embodiment are detailed in Table 1.

[0159] The parameters of the negative electrode material after removing the silicon material in this embodiment are detailed in Table 2.

[0160] The parameters of the negative electrode material in this embodiment are detailed in Table 3.

[0161] Example 5

[0162] The difference from Example 1 is that the constant temperature time for vapor deposition of disilane and carbon material in step (4) is 90 minutes, and the other conditions are exactly the same as those in Example 1.

[0163] The negative electrode material prepared in this embodiment includes a carbon material and a silicon material. The carbon material has pores, including open pores and closed pores. At least part of the silicon material is distributed in the pores of the carbon material. The carbon material is a biomatrix porous carbon, the silicon material is amorphous silicon, and the average particle size of the silicon material is 3.8 nm. The D of the negative electrode material is 1.34 nm. min 2.1μm, D 50 8.5μm, D max It is 24.0μm.

[0164] The parameters of the carbon material in this embodiment are detailed in Table 1.

[0165] The parameters of the negative electrode material after removing the silicon material in this embodiment are detailed in Table 2.

[0166] The parameters of the negative electrode material in this embodiment are detailed in Table 3.

[0167] Example 6

[0168] The difference from Example 1 is that the constant temperature time for vapor deposition of disilane and carbon material in step (4) is 150 min, and the other conditions are exactly the same as those in Example 1.

[0169] The negative electrode material prepared in this embodiment includes a carbon material and a silicon material. The carbon material has pores, including open pores and closed pores. At least part of the silicon material is distributed in the pores of the carbon material. The carbon material is a biomatrix porous carbon, the silicon material is amorphous silicon, and the average particle size of the silicon material is 4.9 nm. The D of the negative electrode material is 1.34 nm. min2.5μm, D 50 8.9μm, D max It is 26.0μm.

[0170] The parameters of the carbon material in this embodiment are detailed in Table 1.

[0171] The parameters of the negative electrode material after removing the silicon material in this embodiment are detailed in Table 2.

[0172] The parameters of the negative electrode material in this embodiment are detailed in Table 3.

[0173] Example 7

[0174] The difference from Example 4 is that the carbonization temperature in step (2) is 900° C., and the other conditions are exactly the same as those in Example 1.

[0175] The negative electrode material prepared in this embodiment includes a carbon material and a silicon material. The carbon material has pores, including open pores and closed pores. At least part of the silicon material is distributed in the pores of the carbon material. The carbon material is a biomatrix porous carbon, the silicon material is amorphous silicon, and the average particle size of the silicon material is 3.9 nm. The D of the negative electrode material is 1.34 nm. min 2.2μm, D 50 8.6μm, D max It is 24.0μm.

[0176] The parameters of the carbon material in this embodiment are detailed in Table 1.

[0177] The parameters of the negative electrode material after removing the silicon material in this embodiment are detailed in Table 2.

[0178] The parameters of the negative electrode material in this embodiment are detailed in Table 3.

[0179] Example 8

[0180] The difference from Example 4 is that the carbonization temperature in step (2) is 1000° C., and the other conditions are exactly the same as those in Example 1.

[0181] The negative electrode material prepared in this embodiment includes a carbon material and a silicon material. The carbon material has pores, including open pores and closed pores. At least part of the silicon material is distributed in the pores of the carbon material. The carbon material is a biomatrix porous carbon, the silicon material is amorphous silicon, and the average particle size of the silicon material is 4.0 nm. The D of the negative electrode material is 1.34 nm. min 2.2μm, D 50 8.6μm, D max It is 24.0μm.

[0182] The parameters of the carbon material in this embodiment are detailed in Table 1.

[0183] The parameters of the negative electrode material after removing the silicon material in this embodiment are detailed in Table 2.

[0184] The parameters of the negative electrode material in this embodiment are detailed in Table 3.

[0185] Example 9

[0186] The difference from Example 4 is that the carbonization temperature in step (2) is 1100° C., and the other conditions are exactly the same as those in Example 1.

[0187] The negative electrode material prepared in this embodiment includes a carbon material and a silicon material. The carbon material has pores, including open pores and closed pores. At least part of the silicon material is distributed in the pores of the carbon material. The carbon material is a biomatrix porous carbon, the silicon material is amorphous silicon, and the average particle size of the silicon material is 4.3 nm. The D of the negative electrode material is 1.3 nm. min 2.2μm, D 50 8.6μm, D max It is 24.0μm.

[0188] The parameters of the carbon material in this embodiment are detailed in Table 1.

[0189] The parameters of the negative electrode material after removing the silicon material in this embodiment are detailed in Table 2.

[0190] The parameters of the negative electrode material in this embodiment are detailed in Table 3.

[0191] Example 10

[0192] (1) Weigh 50 g of lignin and place it in a preheating furnace for preactivation treatment at 300 °C for 3 h to obtain preactivated lignin.

[0193] (2) Weigh 30 g of the above-mentioned preactivated lignin and 15 g of potassium hydroxide, grind and mix them evenly to obtain a mixture; place the mixture in a vacuum box furnace, heat it to 1000° C., and keep the temperature constant for 3 hours.

[0194] (3) The carbonized product is acid-washed and water-washed to a pH of 7.0, and then filtered, dried, and sieved to obtain a porous carbon material.

[0195] (4) Weigh 4 g of the above-mentioned carbon material and place it in a tubular furnace. Raise the temperature to 400°C at a rate of 5°C / min, introduce disilane and nitrogen into the tubular furnace at a flow ratio of 1:2, and maintain the temperature for 90 minutes to obtain an active material. Then, raise the temperature to 650°C at a rate of 5°C / min, introduce propane and nitrogen into the tubular furnace at a flow ratio of 2:7, and maintain the temperature for 30 minutes.

[0196] (5) The obtained sample is crushed, sieved, and demagnetized to obtain the negative electrode material.

[0197] The negative electrode material prepared in this embodiment includes a carbon material and a silicon material. The carbon material has pores, including open pores and closed pores. At least part of the silicon material is distributed in the pores of the carbon material. The carbon material is a biomatrix porous carbon, the silicon material is amorphous silicon, and the average particle size of the silicon material is 3.6 nm. The D of the negative electrode material is 1.34 nm. min 2.2μm, D 50 8.6μm, D max It is 24.0μm.

[0198] The parameters of the carbon material in this embodiment are detailed in Table 1.

[0199] The parameters of the negative electrode material after removing the silicon material in this embodiment are detailed in Table 2.

[0200] The parameters of the negative electrode material in this embodiment are detailed in Table 3.

[0201] Example 11

[0202] The difference from Example 10 is that (4) 4 g of the above-mentioned carbon material was weighed and placed in a tubular furnace, the temperature was raised to 510°C at 5°C / min, disilane and nitrogen were introduced into the tubular furnace at a flow ratio of 1:2, and the temperature was kept constant for 75 minutes to obtain an active substance; then the temperature was raised to 650°C at 5°C / min, propane and nitrogen were introduced into the tubular furnace at a flow ratio of 2:7, and the temperature was kept constant for 30 minutes.

[0203] The remaining conditions are exactly the same as in Example 10.

[0204] The negative electrode material prepared in this embodiment includes a carbon material and a silicon material. The carbon material has pores, including open pores and closed pores. At least part of the silicon material is distributed in the pores of the carbon material. The carbon material is a biomatrix porous carbon, the silicon material is amorphous silicon, and the average particle size of the silicon material is 4.2 nm. The D of the negative electrode material is 1.34 nm. min 2.2μm, D 50 8.6μm, D max It is 24.0μm.

[0205] The parameters of the carbon material in this embodiment are detailed in Table 1.

[0206] The parameters of the negative electrode material after removing the silicon material in this embodiment are detailed in Table 2.

[0207] The parameters of the negative electrode material in this embodiment are detailed in Table 3.

[0208] Example 12

[0209] The difference from Example 10 is that (4) 4 g of the above-mentioned carbon material was weighed and placed in a tubular furnace, the temperature was raised to 550°C at 5°C / min, disilane and nitrogen were introduced into the tubular furnace at a flow ratio of 1:2, and the temperature was kept constant for 70 minutes to obtain an active material; then the temperature was raised to 650°C at 5°C / min, propane and nitrogen were introduced into the tubular furnace at a flow ratio of 2:7, and the temperature was kept constant for 30 minutes.

[0210] The remaining conditions are exactly the same as in Example 10.

[0211] The negative electrode material prepared in this embodiment includes a carbon material and a silicon material. The carbon material has pores, including open pores and closed pores. At least part of the silicon material is distributed in the pores of the carbon material. The carbon material is a biomatrix porous carbon, the silicon material is amorphous silicon, and the average particle size of the silicon material is 4.4 nm. The D of the negative electrode material is 1.34 nm. min 2.2μm, D 50 8.6μm, D max It is 24.0μm.

[0212] The parameters of the carbon material in this embodiment are detailed in Table 1.

[0213] The parameters of the negative electrode material after removing the silicon material in this embodiment are detailed in Table 2.

[0214] The parameters of the negative electrode material in this embodiment are detailed in Table 3.

[0215] Example 13

[0216] The difference from Example 10 is that (4) 4 g of the above-mentioned carbon material was weighed and placed in a tubular furnace, the temperature was raised to 600°C at 5°C / min, disilane and nitrogen were introduced into the tubular furnace at a flow ratio of 1:2, and the temperature was kept constant for 65 minutes to obtain an active substance; then the temperature was raised to 650°C at 5°C / min, propane and nitrogen were introduced into the tubular furnace at a flow ratio of 2:7, and the temperature was kept constant for 30 minutes.

[0217] The remaining conditions are exactly the same as those in Example 1.

[0218] The negative electrode material prepared in this embodiment includes a carbon material and a silicon material. The carbon material has pores, including open pores and closed pores. At least part of the silicon material is distributed in the pores of the carbon material. The carbon material is a biomatrix porous carbon, the silicon material is amorphous silicon, and the average particle size of the silicon material is 4.7 nm. The D of the negative electrode material is 1.34 nm. min 2.2μm, D 50 8.6μm, D max It is 24.0μm.

[0219] The parameters of the carbon material in this embodiment are detailed in Table 1.

[0220] The parameters of the negative electrode material after removing the silicon material in this embodiment are detailed in Table 2.

[0221] The parameters of the negative electrode material in this embodiment are detailed in Table 3.

[0222] Example 14

[0223] (1) Weigh 30 g of coconut shell carbon and 15 g of potassium hydroxide, grind and mix them evenly to obtain a mixture; place the mixture in a vacuum box furnace, heat it to 1000°C, and keep the temperature constant for 3 hours.

[0224] (2) The carbonized product is acid-washed and water-washed to a pH of 7.0, and then filtered, dried, and sieved to obtain a porous carbon material.

[0225] (3) Weigh 4 g of the above-mentioned carbon material and place it in a tube furnace. Raise the temperature to 460°C at a rate of 5°C / min, introduce disilane and nitrogen into the tube furnace at a flow ratio of 1:2, and maintain the temperature for 80 minutes to obtain an active material. Then, raise the temperature to 650°C at a rate of 5°C / min, introduce propane and nitrogen into the tube furnace at a flow ratio of 2:7, and maintain the temperature for 30 minutes.

[0226] (4) The obtained sample is crushed, sieved, and demagnetized to obtain the negative electrode material.

[0227] The negative electrode material prepared in this embodiment includes a carbon material and a silicon material. The carbon material has pores, including open pores and closed pores. At least part of the silicon material is distributed in the pores of the carbon material. The carbon material is a biomatrix porous carbon, the silicon material is amorphous silicon, and the average particle size of the silicon material is 3.6 nm. The D of the negative electrode material is 1.34 nm. min 2.0μm, D 50 8.5μm, D max It is 24.0μm.

[0228] The parameters of the carbon material in this embodiment are detailed in Table 1.

[0229] The parameters of the negative electrode material after removing the silicon material in this embodiment are detailed in Table 2.

[0230] The parameters of the negative electrode material in this embodiment are detailed in Table 3.

[0231] Example 15

[0232] The difference from Example 4 is that, (2) 30 g of the above-mentioned preactivated lignin and 10 g of potassium hydroxide were weighed and ground and mixed uniformly to obtain a mixture; the mixture was placed in a vacuum box furnace, heated to 800° C., and kept at this temperature for 3 h.

[0233] The negative electrode material prepared in this embodiment includes a carbon material and a silicon material. The carbon material has pores, including open pores and closed pores. At least part of the silicon material is distributed in the pores of the carbon material. The carbon material is a biomatrix porous carbon, the silicon material is amorphous silicon, and the average particle size of the silicon material is 4.1 nm. The D of the negative electrode material is 1.34 nm. min 2.0μm, D 50 8.5μm, D max It is 24.0μm.

[0234] The parameters of the carbon material in this embodiment are detailed in Table 1.

[0235] The parameters of the negative electrode material after removing the silicon material in this embodiment are detailed in Table 2.

[0236] The parameters of the negative electrode material in this embodiment are detailed in Table 3.

[0237] Example 16

[0238] The difference from Example 4 is that, (4) 4 g of the above-mentioned carbon material was weighed and placed in a tube furnace, the temperature was raised to 460°C at 5°C / min, disilane and nitrogen were introduced into the tube furnace at a flow ratio of 1:2, and the temperature was kept constant for 80 minutes to obtain an active substance; the active substance was mixed with sucrose at a mass ratio of 1:1, and then the mixed material was placed in a high-temperature box furnace, nitrogen was introduced, and carbonization treatment was carried out at 650°C, and the temperature was kept constant for 5 hours.

[0239] The negative electrode material prepared in this embodiment includes a carbon material and a silicon material. The carbon material has pores, including open pores and closed pores. At least part of the silicon material is distributed in the pores of the carbon material. The carbon material is a biomatrix porous carbon, the silicon material is amorphous silicon, and the average particle size of the silicon material is 3.6 nm. The D of the negative electrode material is 1.34 nm. min 2.0μm, D 50 8.5μm, D max It is 24.0μm.

[0240] The parameters of the carbon material in this embodiment are detailed in Table 1.

[0241] The parameters of the negative electrode material after removing the silicon material in this embodiment are detailed in Table 2.

[0242] The parameters of the negative electrode material in this embodiment are detailed in Table 3.

[0243] Example 17

[0244] The difference from Example 4 is that, (4) 4 g of the above-mentioned carbon material was weighed and placed in a tube furnace, the temperature was raised to 460°C at 5°C / min, disilane and nitrogen were introduced into the tube furnace at a flow ratio of 1:2, and the temperature was kept constant for 80 minutes to obtain an active substance; the active substance was mixed with ethanol at a mass ratio of 1:2, and then the mixed material was placed in a high-temperature box furnace, nitrogen was introduced, and carbonization treatment was carried out at 650°C and kept warm for 2 hours.

[0245] The negative electrode material prepared in this embodiment includes a carbon material and a silicon material. The carbon material has pores, including open pores and closed pores. At least part of the silicon material is distributed in the pores of the carbon material. The carbon material is a biomatrix porous carbon, the silicon material is amorphous silicon, and the average particle size of the silicon material is 3.6 nm. The D of the negative electrode material is 1.34 nm. min 2.0μm, D 50 8.5μm, D max It is 24.0μm.

[0246] The parameters of the carbon material in this embodiment are detailed in Table 1.

[0247] The parameters of the negative electrode material after removing the silicon material in this embodiment are detailed in Table 2.

[0248] The parameters of the negative electrode material in this embodiment are detailed in Table 3.

[0249] Example 18

[0250] The difference from Example 4 is that: (1) 100 g of coal tar, 30 g of calcium oxide and 15 g of potassium hydroxide were weighed, ground and mixed uniformly to obtain a mixture; the mixture was placed in a vacuum box furnace, heated to 800° C., and kept at this temperature for 3 h.

[0251] The negative electrode material prepared in this embodiment includes a carbon material and a silicon material. The carbon material has pores, including open pores and closed pores. At least part of the silicon material is distributed in the pores of the carbon material. The carbon material is tar coal-based porous carbon, the silicon material is amorphous silicon, and the average particle size of the silicon material is 3.6 nm. The D of the negative electrode material is 1.34 nm. min 2.0μm, D 50 8.5μm, D max It is 24.0μm.

[0252] The parameters of the carbon material in this embodiment are detailed in Table 1.

[0253] The parameters of the negative electrode material after removing the silicon material in this embodiment are detailed in Table 2.

[0254] The parameters of the negative electrode material in this embodiment are detailed in Table 3.

[0255] Example 19

[0256] The difference from Example 4 is that (2) 40 g of the above-mentioned preactivated lignin and 10 g of potassium hydroxide were weighed and ground and mixed uniformly to obtain a mixture; the mixture was placed in a vacuum box furnace, heated to 800° C., and kept at this temperature for 3 h.

[0257] The negative electrode material prepared in this embodiment includes a carbon material and a silicon material. The carbon material has pores, including open pores and closed pores. At least part of the silicon material is distributed in the pores of the carbon material. The carbon material is a biomatrix porous carbon, the silicon material is amorphous silicon, and the average particle size of the silicon material is 3.6 nm. The D of the negative electrode material is 1.34 nm. min 2.0μm, D 50 8.5μm, D max It is 24.0μm.

[0258] The parameters of the carbon material in this embodiment are detailed in Table 1.

[0259] The parameters of the negative electrode material after removing the silicon material in this embodiment are detailed in Table 2.

[0260] The parameters of the negative electrode material in this embodiment are detailed in Table 3.

[0261] Example 20

[0262] The difference from Example 4 is that, (2) 30 g of the above-mentioned preactivated lignin and 10 g of potassium hydroxide were weighed and ground and mixed uniformly to obtain a mixture; the mixture was placed in a vacuum box furnace, heated to 800° C., and kept at this temperature for 3 h.

[0263] The negative electrode material prepared in this embodiment includes a carbon material and a silicon material. The carbon material has pores, including open pores and closed pores. At least part of the silicon material is distributed in the pores of the carbon material. The carbon material is a biomatrix porous carbon, the silicon material is amorphous silicon, and the average particle size of the silicon material is 3.6 nm. The D of the negative electrode material is 1.34 nm. min 2.0μm, D 50 8.5μm, D max It is 24.0μm.

[0264] The parameters of the carbon material in this embodiment are detailed in Table 1.

[0265] The parameters of the negative electrode material after removing the silicon material in this embodiment are detailed in Table 2.

[0266] The parameters of the negative electrode material in this embodiment are detailed in Table 3.

[0267] Comparative Example 1

[0268] The difference from Example 1 is that the carbonization temperature in step (2) is 700° C., and the other conditions are exactly the same as those in Example 1.

[0269] The negative electrode material prepared in this comparative example includes a carbon material and a silicon material. The carbon material has pores, including open pores and closed pores. At least part of the silicon material is distributed in the pores of the carbon material. The carbon material is a biomatrix porous carbon, the silicon material is amorphous silicon, the average particle size of the silicon material is 3.6 nm, and the D of the negative electrode material is 0.1447 nm. min 2.0μm, D 50 8.5μm, D max It is 24.0μm.

[0270] The parameters of the carbon materials in this comparative example are detailed in Table 1.

[0271] The parameters of the negative electrode material after removing the silicon material in this comparative example are detailed in Table 2.

[0272] The parameters of the negative electrode materials in this comparative example are detailed in Table 3.

[0273] Comparative Example 2

[0274] The difference from Example 4 is that the carbonization temperature in step (2) is 1200° C., and the other conditions are exactly the same as those in Example 4.

[0275] The negative electrode material prepared in this comparative example includes a carbon material and a silicon material. The carbon material has pores, including open pores and closed pores. At least part of the silicon material is distributed in the pores of the carbon material. The carbon material is a biomatrix porous carbon, the silicon material is amorphous silicon, the average particle size of the silicon material is 3.6 nm, and the D of the negative electrode material is 0.1447 nm. min 2.0μm, D 50 8.5μm, D max It is 24.0μm.

[0276] The parameters of the carbon materials in this comparative example are detailed in Table 1.

[0277] The parameters of the negative electrode material after removing the silicon material in this comparative example are detailed in Table 2.

[0278] The parameters of the negative electrode materials in this comparative example are detailed in Table 3.

[0279] Comparative Example 3

[0280] The difference from Example 1 is that the constant temperature time for vapor deposition of disilane and carbon material in step (4) is 15 minutes, and the other conditions are exactly the same as those in Example 1.

[0281] The negative electrode material prepared in this comparative example includes a carbon material and a silicon material. The carbon material has pores, including open pores and closed pores. At least part of the silicon material is distributed in the pores of the carbon material. The carbon material is a biomatrix porous carbon, the silicon material is amorphous silicon, the average particle size of the silicon material is 1.0 nm, and the D of the negative electrode material is 1.0 nm. min 2.0μm, D 508.5μm, D max It is 24.0μm.

[0282] The parameters of the carbon material in this comparative example are the same as those in Example 1.

[0283] The parameters of the negative electrode material after removing the silicon material in this comparative example are detailed in Table 2.

[0284] The parameters of the negative electrode materials in this comparative example are detailed in Table 3.

[0285] Comparative Example 4

[0286] The difference from Example 1 is that the constant temperature time for vapor deposition of disilane and carbon material in step (4) is 180 min, and the other conditions are exactly the same as those in Example 1.

[0287] The negative electrode material prepared in this comparative example includes a carbon material and a silicon material. The carbon material has pores, including open pores and closed pores. At least part of the silicon material is distributed in the pores of the carbon material. The carbon material is a biomatrix porous carbon, the silicon material is amorphous silicon, the average particle size of the silicon material is 7.6 nm, and the D of the negative electrode material is 1.5 nm. min 2.7μm, D 50 9.5μm, D max It is 27.0μm.

[0288] The parameters of the carbon material in this comparative example are the same as those in Example 1.

[0289] The parameters of the negative electrode material after removing the silicon material in this comparative example are detailed in Table 2.

[0290] The parameters of the negative electrode materials in this comparative example are detailed in Table 3.

[0291] Test Method

[0292] (1) Test method for the volume ratio of closed pores, volume ratio of open pores, and total volume of carbon materials, negative electrode materials, and negative electrode materials after silicon materials are removed:

[0293] The volume proportion of open pores is the ratio of the open pore volume to the total volume, and the volume proportion of closed pores is the ratio of the closed pore volume to the total volume. The open pore volume is determined by a nitrogen adsorption and desorption instrument, which uses a Lihua Lianke model iBOX26 instrument; the closed pore volume is determined by a volume difference method, 5g of carbon material or negative electrode material is placed in a 10mL measuring cylinder, 6mL of pure water is added to the measuring cylinder, and ultrasonic oscillation is performed for 1h. When the carbon material or negative electrode material is completely dissolved in water, ultrasonic oscillation is performed for another 30min. The liquid level value of the measuring cylinder at this time is recorded, and the liquid level value minus the volume of pure water is obtained to obtain the skeleton volume and closed pore volume of the carbon material or negative electrode material. The skeleton volume of the carbon material or negative electrode material is the ratio of mass to true density, thereby obtaining the closed pore volume. The total volume is the sum of the skeleton volume, open pore volume and closed pore volume.

[0294] (2) Test method for crushing strength of carbon materials and negative electrode materials:

[0295] 5g of carbon material or negative electrode material is placed on a plate with a diameter of 1.3cm 2 After holding the material in the metal sleeve for 1 minute at multiple different pressures, the pressurized material is removed and its total pore volume is measured using a pore size analyzer. If the decrease rate of the total pore volume of the pressurized material relative to the total pore volume of the raw material is 0-2%, the strength P experienced by the material at that pressure is the material's crushing strength, where P = F / S. When carbon material or negative electrode material particles break, the total pore volume of the material decreases.

[0296] (3) Etching test

[0297] Add 68% concentrated nitric acid by mass to the negative electrode material and soak it for 1 hour. Then, add 20% HF acid solution by mass to the negative electrode material drop by drop, which will produce yellow smoke. Repeat the addition several times until no yellow smoke is produced in the solution. Finally, use 68% concentrated nitric acid by mass to digest the residue, then wash and dry it to obtain the negative electrode material after removing the silicon material.

[0298] (4) Test method for true density of negative electrode material:

[0299] The density was measured by JW-M100 precision high-pressure tester. 5g of negative electrode material was placed on a 1.3cm diameter 2 After maintaining the sample at 5T for 30 minutes in a metal sleeve, the sample is ground and passed through a 1000-mesh sieve. The resulting sample is dissolved in an appropriate amount of solvent. The device is assembled and debugged and calibrated according to the instructions. The prepared sample is added to the device, and preliminary adjustments are made. The device is then started and the experiment is carried out. During the experiment, the temperature and gas collection status need to be continuously monitored and recorded. When the gas volume in the collector reaches a certain level, the experiment can be terminated. The obtained data is used to calculate the proportion of the substance to be tested in the sample.

[0300] (5) Testing method for specific surface area of ​​negative electrode material:

[0301] The specific surface area was measured using a Micromeritics TriStar 3000 surface area and pore size analyzer.

[0302] (6) Test method for pore size distribution of carbon materials:

[0303] The carbon material was tested using the Lihua Lianke iPore620 pore size tester and the BET pore size distribution test method. The isothermal adsorption characteristic curve of nitrogen was used to obtain the pore size distribution data of the carbon material through DFT simulation analysis, and then the total pore volume of the carbon material and the volume ratio of the pore volume of micropores, mesopores and macropores in the total pore volume were obtained.

[0304] (7) Test method for the mass content of silicon in negative electrode materials:

[0305] After drying the sample overnight, place it in a corundum crucible, and then place the crucible in a muffle furnace (Nanyang Xinyu SA2-9-17TP) at 1200°C for 480 minutes to complete the combustion of carbon and the oxidation reaction of silicon or silicon oxide to silicon dioxide. During the process, the crucible weight m0, sample weight m1, and total weight of the crucible and product after calcination m2 were recorded, and the silicon content was calculated according to the following formula: Si% = (m2-m0) / m1×28.09 / 60.09×100%.

[0306] (8) Test method for particle size of negative electrode material:

[0307] The particle size distribution range of the composite negative electrode material was tested by Malvern laser particle size analyzer.

[0308] (9) Electrochemical performance test:

[0309] Electrochemical cycling performance was tested using the following method: The negative electrode materials, conductive agent, and binder prepared in Examples 1-18 and Comparative Examples 1-4 were dissolved in a solvent at a ratio of 94:1:5 by mass, with a solids content controlled at 50%. The mixture was then coated onto a copper foil current collector and vacuum-dried to produce a negative electrode. 18650 cylindrical cells were then assembled using conventional production processes using a ternary positive electrode prepared using a conventional process, a 1 mol / L lithium hexafluorophosphate (LiPF6) / (ethylene carbonate (EC) + dimethyl carbonate (DMC) + ethyl methyl carbonate (EMC)) (v / v = 1:1:1) electrolyte, a Celgard 2400 separator, and a casing. Cylindrical cells were charged and discharged using a LAND battery test system from Wuhan Jinnuo Electronics Co., Ltd. at room temperature, with a constant current of 0.2C and a voltage limit of 2.75-4.2V. The first reversible capacity, first cycle charge capacity, and first cycle discharge capacity were obtained. First cycle coulombic efficiency = first cycle discharge capacity / first cycle charge capacity.

[0310] Repeat the cycle for 50 times, and use a micrometer to measure the thickness of the lithium-ion battery electrode, which is H1. The expansion rate after 50 cycles = (H1-H0) / H0×100%.

[0311] Repeat the cycle for 50 cycles and record the discharge capacity as the remaining capacity of the lithium-ion battery; capacity retention rate = remaining capacity / initial capacity*100%.

[0312] The test results are detailed in Tables 1 and 2.

[0313] Table 1 Performance parameters of carbon materials prepared in Examples and Comparative Examples

[0314] According to the test results in Table 1, the carbon materials prepared in Examples 1 to 20 of the present application have pores, and the total pore volume of the carbon materials is 0.5 cm 3 / g~1.6cm 3 / g, the carbon material has suitable pores, and these pores can provide sufficient accommodation space for the silicon material, alleviating the volume expansion of the silicon material; and the crushing strength of the carbon material is U1kN / cm 2 , 0.05≤U1≤0.3; the crushing strength of the carbon material is closely related to the pores in the carbon material. The crushing strength of the carbon material is within the above range, so that the carbon material has excellent structural stability, so that the carbon material after composite silicon material can also have excellent structural stability, thereby reducing the collapse and breakage of the carbon material structure caused by the volume expansion of the silicon material during the lithium insertion and extraction process, thereby reducing the occurrence of side reactions, and thus improving the capacity and cycle performance of the negative electrode material.

[0315] Compared with Example 1, the carbonization temperature is lowered during the preparation of the carbon material in Comparative Example 1, the activation degree of the carbon material is weakened, the pores in the carbon material are reduced, and the crushing strength of the carbon material is higher. After the subsequent composite silicon material, the space in the carbon material to alleviate the volume expansion of the silicon material is reduced, and the carbon material is difficult to withstand the expansion stress generated by the silicon material during the lithium insertion and extraction process. The carbon material is prone to breakage, which in turn affects the cycle stability of the negative electrode material prepared from the carbon material.

[0316] Compared with Example 1, the carbonization temperature in the carbon material preparation process of Comparative Example 2 increases, the activation degree of the carbon material is enhanced, the pores in the carbon material increase, and the crushing strength of the carbon material is too low. After the subsequent composite silicon material, the carbon material is difficult to withstand the expansion stress generated by the silicon material during the lithium insertion and extraction process. The carbon material is prone to breakage, which in turn affects the cycle stability of the negative electrode material prepared from the carbon material.

[0317] Table 2 Performance parameters of negative electrode materials after removing silicon material in Examples and Comparative Examples

[0318] Table 3 Performance parameters of negative electrode materials prepared in Examples and Comparative Examples

[0319] As can be seen from the test data in Table 3, the negative electrode materials prepared in Examples 1 to 20 include carbon materials and silicon materials. The carbon material has pores, and at least part of the silicon material is distributed in the pores of the carbon material, which can increase the capacity of the negative electrode material. At the same time, the pores are reduced after the carbon material is filled with the silicon material, which can increase the density of the negative electrode material, thereby improving the structural stability of the negative electrode material and further improving the cycle performance of the negative electrode material. At the same time, the negative electrode material has pores, and the pores include open pores and closed pores. The volume ratio of the closed pores in the negative electrode material is P1%, 0.1≤P1≤5.0, and the volume ratio of the open pores in the negative electrode material is P2%, 0.1≤P2≤20, and the crushing strength of the negative electrode material is U2kN / cm 2 , 0.35≤U2≤1.5. Since the volume ratio of closed pores in the negative electrode material is within the above range, there are appropriate open and closed pores inside the negative electrode material, which can improve the structural stability of the negative electrode material and the crushing strength of the negative electrode material, thereby reducing the probability of the negative electrode material breaking during the cycle and improving the cycle performance of the negative electrode material. In addition, the appropriate closed pores inside the negative electrode material can also provide a certain buffer space for the volume expansion of the silicon material, inhibiting the volume expansion of the negative electrode material, reducing the collapse and breakage of the negative electrode material structure caused by volume expansion during the lithium insertion and extraction process, and improving the cycle performance of the negative electrode material. In addition, since the volume of the pores in the negative electrode material accounts for a certain proportion of the volume of the negative electrode material in the negative electrode material within the above range, on the one hand, the silicon material is filled in the pores of the carbon material to increase the capacity of the negative electrode material; on the other hand, the internal pores of the carbon material are reduced after being filled with the silicon material, thereby increasing the density of the negative electrode material, improving the structural stability of the negative electrode material, and thus increasing the crushing strength of the negative electrode material. At the same time, the pores in the negative electrode material within a suitable range can also provide a certain buffer space for the volume expansion of the silicon material, inhibiting the volume expansion of the negative electrode material, thereby reducing the collapse and fragmentation of the negative electrode material structure caused by volume expansion during the lithium insertion and extraction process, and improving the cycle performance of the negative electrode material. In addition, the volume of the pores in the negative electrode material accounts for a certain proportion of the volume of the negative electrode material in the negative electrode material within the above range, which can also reduce the contact area between the electrolyte and the negative electrode material, thereby making it difficult for the electrolyte to penetrate into the interior of the negative electrode material, thereby effectively reducing the occurrence of side reactions between the negative electrode material and the electrolyte, and thereby improving the electrochemical performance of the negative electrode material. In summary, the present application controls the volume ratio of closed pores and open pores in the negative electrode material within an appropriate range, so that appropriate closed pores and open pores exist in the negative electrode material, thereby improving the crushing strength of the negative electrode material through the synergistic effect between the closed pores and open pores, and finding a balance between the closed pore volume ratio, open pore volume ratio and crushing strength of the negative electrode material, thereby suppressing the volume expansion of the negative electrode material, improving the structural stability of the negative electrode material, and thereby improving the electrochemical performance of the negative electrode material.

[0320] By comparing the test data of Examples 1 to 6, it can be seen that as the time for vapor deposition of the silicon source gas and the carbon material increases, the mass content of silicon in the negative electrode material increases, and the capacity of the negative electrode material also increases accordingly. At the same time, due to the increase in the amount of silicon deposition, the volume proportion of the open pores in the negative electrode material decreases, the total pore volume of the negative electrode material decreases, and the crushing strength of the negative electrode material increases, but the expansion rate of the negative electrode material increases, and the cycle performance also decreases.

[0321] By comparing the test data of Example 4 and Examples 7 to 9, it can be seen that as the carbonization temperature increases during the preparation of the carbon material, the closed pore volume ratio in the negative electrode material decreases, the pores in the negative electrode material decrease, and the expansion rate of the negative electrode material increases. However, since the crushing strength of the negative electrode material increases accordingly, the cycle performance of the negative electrode material increases.

[0322] By comparing the test data of Examples 10 to 13, it can be seen that as the disilane cracking temperature increases, the disilane cracking rate accelerates, which will cause some of the pores inside the carbon material to be unable to be filled, and closed pores are formed. The volume proportion of closed pores in the negative electrode material increases, but the increase in cracking temperature may cause the amorphous silicon inside the negative electrode material to be converted into crystalline silicon, thereby increasing the expansion effect of the negative electrode material. At the same time, the increase in closed pores inside the negative electrode material leads to a decrease in the crushing strength of the material, thereby causing a decrease in the cycle performance of the negative electrode material.

[0323] Compared with Example 1, in the negative electrode material prepared in Comparative Example 1, during the preparation process of the carbon material, the carbonization temperature of the carbon source and activator carbonization treatment process is reduced, the activation degree of the carbon material is weakened, the total pore volume of the carbon material is reduced, the pore structure in the carbon material is reduced, the volume proportion of the micropores in the carbon material is reduced, and the silicon material is difficult to be uniformly deposited in the carbon material, resulting in an increase in the expansion rate of the negative electrode material, and an excessive proportion of closed pores in the carbon material. After the carbon material and the silicon material are deposited, the closed pores inside the carbon material increase, resulting in a decrease in the crushing strength of the negative electrode material. The negative electrode material is easily broken during the cycle, resulting in a decrease in the capacity and cycle performance of the negative electrode material.

[0324] Compared with Example 4, in the negative electrode material prepared in Comparative Example 2, during the preparation process of the carbon material, the carbonization temperature of the carbon source and activator carbonization treatment process increases, the activation degree of the carbon material increases, and the volume proportion of closed pores in the carbon material decreases. At the same time, after deposition with the silicon material, the number of open pores in the negative electrode material decreases, so the crushing strength of the negative electrode material increases, but the space in the negative electrode material that can be used to alleviate the volume expansion of the silicon material decreases, thereby increasing the expansion rate of the negative electrode material, resulting in a decrease in the cycle performance of the negative electrode material.

[0325] Compared with Example 1, in the negative electrode material prepared in Comparative Example 3, the time for vapor deposition of silicon source gas and carbon material is too short, and the content of silicon deposited in the carbon material is relatively low, resulting in a decrease in the capacity of the negative electrode material.

[0326] Compared with Example 1, in the negative electrode material prepared in Comparative Example 4, the time for vapor deposition of silicon source gas and carbon material is too long, the amount of silicon deposited in the carbon material increases, the capacity of the negative electrode material increases, and at the same time, the proportion of open pores in the negative electrode material decreases, and the crushing strength of the carbon material increases. However, there is too little space in the negative electrode material that can be used to alleviate the volume expansion of silicon, and the expansion rate of the negative electrode material increases, resulting in a decrease in the cycle performance of the negative electrode material.

[0327] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A carbon material, characterized in that, The carbon material has pores, and the total pore volume of the carbon material is 0.5 cm 3 / g to 1.6 cm 3 / g, and the crushing strength of the carbon material is U1 kN / cm 2 , 0.05 ≤ U1 ≤ 0.

3.

2. The carbon material according to claim 1, characterized in that, The pores in the carbon material include open pores and closed pores, and the carbon material includes at least one of the following characteristics: (1) The volume percentage of the closed pores in the total pore volume of the carbon material is A%, where 1.0 ≤ A ≤ 5.0; (2) The volume percentage of the open pores in the total pore volume of the carbon material is B%, where 95.0 ≤ B ≤ 99.0; (3) The pores in the carbon material include micropores, mesopores, and macropores. Among them, the volume percentage of the micropores in the total pore volume is 60% - 97%.

3. The carbon material according to claim 1, wherein The carbon material includes at least one of biomass-based porous carbon, synthetic polymer-based porous carbon, and tar coal-based porous carbon.

4. A negative electrode material, characterized in that, The negative electrode material includes a carbon material and a silicon material. The carbon material has pores, and at least part of the silicon material is distributed in the pores of the carbon material; the total pore volume in the negative electrode material after removing the silicon material is 0.5 cm 3 / g to 1.6 cm 3 / g, and the crushing strength is U1 kN / cm 2 , where 0.05 ≤ U1 ≤ 0.

3.

5. The negative electrode material according to claim 4, characterized in that, The pores in the carbon material include open pores and closed pores, and the carbon material includes at least one of the following characteristics: (1) The volume percentage of the closed pores in the total pore volume of the carbon material is A%, where 1.0 ≤ A ≤ 5.0; (2) The volume percentage of the open pores in the total pore volume of the carbon material is B%, where 95.0 ≤ B ≤ 99.0; (3) The pores in the carbon material include micropores, mesopores, and macropores. Among them, the volume percentage of the micropores in the total pore volume is 60% - 97%.

6. The negative electrode material according to claim 4, characterized in that, The carbon material includes at least one of biomass-based porous carbon, synthetic polymer-based porous carbon, and tar coal-based porous carbon.

7. A negative electrode material, characterized in that, The negative electrode material includes a carbon material and a silicon material. The carbon material has pores, and at least part of the silicon material is distributed in the pores of the carbon material; The negative electrode material has pores, and the pores include open pores and closed pores; the volume percentage of the closed pores in the negative electrode material is P1%, where 0.1 ≤ P1 ≤ 5, and the volume percentage of the open pores in the negative electrode material is P2%, where 0.1 ≤ P2 ≤ 20; and the crushing strength of the negative electrode material is U2 kN / cm 2 , 0.35 ≤ U2 ≤ 1.

5.

8. The negative electrode material according to claim 7, wherein, The negative electrode material includes at least one of the following characteristics: (1) The total pore volume of the negative electrode material after removing the silicon material is 0.3 cm 3 / g to 1.5 cm 3 / g; (2) The pores in the negative electrode material after removing the silicon material include micropores, mesopores, and macropores. Among them, the volume percentage of the micropores in the total pore volume is 50% - 90%; (3) The volume percentage of the closed pores in the total pore volume of the negative electrode material after removing the silicon material is 3.0% - 6.0%; (4) The volume percentage of the open pores in the total pore volume of the negative electrode material after removing the silicon material is 94.0% - 97.0%.

9. The negative electrode material according to claim 7, characterized in that, The negative electrode material includes at least one of the following characteristics: (5) The silicon material includes at least one of amorphous silicon, crystalline silicon, silicon oxide, or silicon alloy; (6) The average particle size of the silicon material is 1 nm - 5 nm.

10. The negative electrode material according to claim 7, wherein Based on the mass of the negative electrode material being 100%, the mass content of the silicon element is 10% - 85%.

11. The negative electrode material according to claim 7, characterized in that, The true density of the negative electrode material is ρ g / cm 3 , where 1.2 ≤ ρ ≤ 3.

0.

12. The negative electrode material according to claim 7, wherein The total pore volume of the negative electrode material is 0.01 cm 3 / g to 0.10 cm 3 / g.

13. The negative electrode material according to claim 7, characterized in that, The particle size of the negative electrode material satisfies: 1 μm ≤ D min ≤ 3 μm, 6 μm ≤ D 50 ≤ 8 μm, D max ≤ 30 μm.

14. The negative electrode material according to claim 7, characterized in that, The specific surface area of the negative electrode material is 0.8 m 2 / g to 20 m 2 / g.

15. A battery, characterized in that, The battery includes the carbon material according to any one of claims 1 - 3 or the negative electrode material according to any one of claims 4 - 14.

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