Negative electrode material, negative electrode sheet, and battery

Abstract

The present invention provides a negative electrode material and a preparation method therefor, a negative electrode sheet, and a battery. The negative electrode material comprises a carbon matrix and a silicon material. Upon subjecting the negative electrode material to a Raman spectrum test, the negative electrode material has a graphitized carbon G peak at 1580±20 cm-1, and the intensity of the graphitized carbon G peak is IG. The negative electrode material has a disordered carbon D peak at 1350±20 cm-1, and the intensity of the disordered carbon D peak is ID. The negative electrode material has a disordered silicon peak at 480±10 cm-1, and the intensity of the disordered silicon peak is I480. The negative electrode material has a crystalline silicon peak at 520±10 cm-1, and the intensity of the crystalline silicon peak is I520. Using G to represent the degree of graphitization of the negative electrode material, G=IG / ID. Using Sa to represent the degree of silicon disorder of the negative electrode material, I480 / I520. The negative electrode material satisfies the following relational expression: 0.64<G*Sa<3.0. The negative electrode material satisfying said expression has excellent electrical conductivity and an excellent cycle expansion rate.

Description

Negative electrode material, negative electrode sheet and battery Cross-references to related applications

[0001] This application claims priority to Chinese patent application filed on December 30, 2024, application number 202411977674.7, entitled "Anode material and preparation method thereof, anode sheet and battery". Technical Field

[0002] This invention relates to the field of secondary battery materials technology, and more specifically, to a negative electrode material, a negative electrode sheet, and a battery. Background Technology

[0003] Anode materials are one of the key materials for achieving high capacity and long cycle life in lithium-ion batteries. However, traditional graphite anode materials often have low capacity. Silicon-based anode materials have gradually become popular worldwide due to the high capacity advantage of silicon.

[0004] Silicon possesses a capacity advantage as an anode material, with a theoretical capacity reaching 4200 mAh / g, and silicon electrode materials can serve as anode materials for high-energy-density batteries. However, due to the volume expansion and capacity decay of silicon anode materials, their coulombic efficiency is severely low when used as anode materials in secondary batteries; the coulombic efficiency drops from 100% to 50% of the initial coulombic efficiency in just 200 charge-discharge cycles. Therefore, developing silicon anode materials with high electrochemical stability is crucial for improving the application of silicon anode materials. Currently, the coating of silicon-based materials, such as carbon, metals, oxides, and sulfides, plays a vital role in improving the electrochemical performance of silicon-based materials. However, due to the existence of electrochemical processes, the coating layer of silicon-based materials gradually dissolves, eventually leading to capacity decay. Therefore, developing a stable silicon anode material is a current research hotspot and challenge.

[0005] Porous carbon materials possess abundant pore structures, providing ample embedding space for nano-silicon materials, suppressing the expansion effect of silicon anode materials, and mitigating their pulverization problem. Simultaneously, the carbon framework of porous carbon exhibits excellent electronic conductivity, providing a well-developed conductive network for silicon anode materials, improving their conductivity and enhancing their initial efficiency. Therefore, the field of anode materials has witnessed a surge in the development of silicon-carbon anode materials based on porous carbon. Currently, the vapor deposition method for preparing silicon-carbon anode materials based on porous carbon shows the most potential; however, the prepared deposited silicon-carbon anode materials still possess a high proportion of crystalline silicon and a low degree of graphitization, resulting in a high cycle expansion rate and poor electrical conductivity. Summary of the Invention

[0006] The main objective of this invention is to provide a negative electrode material, a negative electrode sheet, and a battery to solve the problems of high cycle expansion rate and poor conductivity of silicon-containing negative electrode materials in the prior art.

[0007] To achieve the above objectives, according to one aspect of the present invention, a negative electrode material is provided, comprising a carbon matrix and a silicon material.

[0008] Raman spectroscopy was performed on the negative electrode material, and the negative electrode material showed a value at 1580±20 cm⁻¹. -1 The location contains a graphitized carbon G peak, and the intensity of the graphitized carbon G peak is I. G , at 1350±20cm -1 The location has a disordered carbon D peak, and the intensity of the disordered carbon D peak is I. D , at 480±10cm -1 There is a disordered silicon peak at this location, and the intensity of the disordered silicon peak is I. 480 520±10cm -1 The location contains a crystalline silicon peak, and the intensity of the crystalline silicon peak is I. 520 ;

[0009] Let G represent the degree of graphitization of the negative electrode material, G = I. G / I D ;

[0010] Use S a S represents the silicon disorder of the negative electrode material. a =I 480 / I 520 ;

[0011] The negative electrode material satisfies the following relationship: 0.64 < G*S a <3.0.

[0012] According to another aspect of this application, a negative electrode sheet is provided, which contains any of the negative electrode materials described above.

[0013] According to another aspect of this application, a battery is provided that includes the aforementioned negative electrode.

[0014] Applying the technical solution of this invention, the negative electrode material of this application includes a carbon matrix and a silicon material. The higher the graphitization degree of the negative electrode material, the larger the π-π conjugated system of the carbon matrix in the negative electrode material, resulting in more conductive electrons and electron orbitals, and thus higher conductivity of the negative electrode material. Conversely, the higher the silicon disorder degree of the negative electrode material, the larger the interstices between silicon atoms, providing more space for lithium intercalation, and resulting in lower cycle expansion rate of the negative electrode material. The graphitization degree G and silicon disorder degree S of the negative electrode material are related. a When the product of these factors is within the aforementioned range, the negative electrode material can exhibit superior conductivity and cycle expansion rate. This is especially true when the graphitization degree G of the negative electrode material and the silicon disorder degree S... a The product of G*S aWhen the degree of graphitization G is less than 0.64, the degree of graphitization or silicon disorder of the anode material is low, resulting in low conductivity or high cycle expansion rate, and poor performance of the anode material. a When the product of the two is too large, greater than 3.0, it indicates that the graphitization degree of the negative electrode material is too high or the silicon disorder is too large. When the graphitization degree of the negative electrode material is too high, it is easy to cause the carbon matrix pores to collapse, the pore volume to decrease, the deposited silicon content to decrease, and the capacity of the negative electrode material to decrease, which is detrimental to the performance of the negative electrode material. When the silicon disorder of the negative electrode material is too large, the activity of the silicon material is high, and some of the silicon material in the negative electrode material is easy to react with the carbon material to form silicon carbide, which leads to a decrease in the capacity of the negative electrode material. Detailed Implementation

[0015] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0016] As analyzed in the background section of this application, existing technologies suffer from problems such as high cyclic expansion rate and poor conductivity of silicon-containing anode materials. To address these issues, this application provides an anode material, an anode electrode sheet, and a battery.

[0017] According to a typical embodiment of this application, a negative electrode material is provided, comprising a carbon matrix and a silicon material; the negative electrode material is subjected to Raman spectroscopy testing, and the negative electrode material shows a Raman spectrum at 1580±20 cm⁻¹. -1 The location contains a graphitized carbon G peak, and the intensity of the graphitized carbon G peak is I. G , at 1350±20cm -1 The location has a disordered carbon D peak, and the intensity of the disordered carbon D peak is I. D , at 480±10cm -1 There is a disordered silicon peak at this location, and the intensity of the disordered silicon peak is I. 480 520±10cm -1 The location contains a crystalline silicon peak, and the intensity of the crystalline silicon peak is I. 520 ;

[0018] Let G represent the degree of graphitization of the negative electrode material, G = I. G / I D ;

[0019] Use S a S represents the silicon disorder of the negative electrode material. a =I 480 / I 520 ;

[0020] The negative electrode material satisfies the following relationship: 0.64 < G*S a <3.0.

[0021] The anode material of this application includes a carbon matrix and a silicon material. The higher the graphitization degree G of the anode material, the larger the π-π conjugated system of the carbon matrix, the more conductive electrons and electron orbitals it can provide, and the higher the conductivity of the anode material; while the silicon disorder degree S of the anode material... a The higher the degree of graphitization (G) of the anode material, the larger the interstices between silicon atoms, providing more space for lithium intercalation and resulting in a lower cycle expansion rate. The graphitization degree (G) of the anode material is related to the silicon disorder degree (S). a When the product of these factors is within the aforementioned range, the negative electrode material can exhibit superior conductivity and cycle expansion rate. This is especially true when the graphitization degree G of the negative electrode material and the silicon disorder degree S... a The product of G*S a When the degree of graphitization G is less than 0.64, the degree of graphitization or silicon disorder of the anode material is low, resulting in low conductivity or high cycle expansion rate, and poor performance of the anode material. a When the product of the two values ​​is too large, exceeding 3.0, it indicates that the graphitization degree of the negative electrode material is too high or the silicon disorder is too large. When the graphitization degree of the negative electrode material is too high, it is easy to cause the pores of the carbon matrix to collapse, reducing the pore volume that can buffer the volume expansion of the silicon material in the negative electrode material, which is detrimental to the performance of the negative electrode material. When the silicon disorder of the negative electrode material is too large, the activity of the silicon material is high, and some of the silicon material in the negative electrode material is easy to react with the carbon material to form silicon carbide, resulting in a decrease in the capacity of the negative electrode material.

[0022] Specifically, G*S a The value can be 0.65, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 2.95, or any value within the range of any two of the above values, and is not limited herein. Preferably, 0.95 < G*S a <3.0, which significantly improves the conductivity and cyclic expansion rate of the negative electrode material, and has good overall performance.

[0023] In some embodiments of this application, the graphitization degree G of the negative electrode material conforms to 0.8 < G < 1.2. A higher graphitization degree in the negative electrode material results in a larger π-π conjugated system in the carbon matrix, providing more conductive electrons and electron orbitals, thus giving the negative electrode material higher conductivity. Specifically, the graphitization degree G of the negative electrode material is 0.82, 0.85, 0.9, 0.95, 1, 1.05, 1.1, 1.15, 1.19, or any value within the range of any two of the above values; no limitation is made here.

[0024] In some embodiments of this application, the silicon disorder S of the negative electrode material a Conforms to 0.8 < S a A silicon disorder value < 2.5 indicates a suitable inter-atomic spacing in the anode material, providing more space for lithium intercalation and resulting in a lower cycle expansion rate. Specifically, the silicon disorder value of the anode material is 0.85, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.45, or any value within the range of any two of the above values; no limitation is imposed here. Preferably, 1.0 < S a <2.4.

[0025] In some embodiments of this application, the specific surface area of ​​the negative electrode material is less than 100 m². 2 / g, specifically 0.5m 2 / g、1m 2 / g、5m 2 / g, 10m 2 / g, 15m 2 / g、20m 2 / g、25m 2 / g、30m 2 / g、35m 2 / g、40m 2 / g、45m 2 / g, 50m 2 / g、60m 2 / g、70m 2 / g、80m 2 / g、90m 2 / g、95m 2 / g or any value within the range of any two of the above values, without limitation. Controlling the specific surface area of ​​the negative electrode material within the above range is beneficial to improving the first-efficiency and cycle performance of lithium batteries made from this negative electrode material.

[0026] In some embodiments of this application, the silicon content in the negative electrode material is 30% to 60%, and the lithium battery prepared from it has high capacity density and high first-efficiency. Specifically, the silicon content in the negative electrode material can be 30%, 33%, 35%, 37%, 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, or any value within the range of any two of the above values, and is not limited herein.

[0027] In some embodiments of this application, the carbon content in the negative electrode material is 40% to 70%, which is beneficial to further improve the conductivity of the negative electrode material and reduce the cyclic expansion rate of the material. Specifically, the carbon content in the negative electrode material can be 40%, 42%, 45%, 48%, 50%, 53%, 55%, 58%, 60%, 62%, 65%, 70%, or any value within the range of any two of the above values, and is not limited here.

[0028] In some embodiments of this application, the median particle size D50 of the negative electrode material is 5 μm to 10 μm, which is beneficial for further improving the cycle performance of the material. Specifically, the median particle size D50 of the negative electrode material can be 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, or any value within the range of any two of the above values, and is not limited herein.

[0029] In some embodiments of this application, the pore volume of the negative electrode material is less than or equal to 0.05 μm. 3 / g, which is beneficial for improving the stability and cycle performance of the anode material. For example, the pore volume of the anode material can be 0.005m³. 3 / g, 0.01m 3 / g, 0.02m 3 / g, 0.03m 3 / g, 0.04m 3 / g, 0.045m 3 / g, 0.05m 3 / g or any value within the range of any two of the above values, without limitation.

[0030] In some embodiments of this application, the negative electrode material has micropores, i.e., pores with a diameter of less than 2 nm. The pore volume of the micropores accounts for 25% to 45% of the total pore volume of the negative electrode material, which is beneficial for lithium ion intercalation, improves the cycle performance of the battery prepared by the negative electrode material, and further reduces the cycle expansion rate. Specifically, the pore volume percentage of the micropores can be 25%, 27%, 30%, 33%, 35%, 38%, 40%, 42%, 45%, or any value within the range of any two of the above values, and is not limited herein.

[0031] In some embodiments of this application, the negative electrode material has mesopores, i.e., a pore structure with a pore size between 2 nm and 50 nm, and the volume percentage of mesopores in the total pore volume of the negative electrode material is 25% to 95%. Specifically, it can be 25%, 30%, 35%, 40%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, 92%, or 95%, etc., and is not limited herein. Preferably, the volume percentage of mesopores in the total pore volume of the negative electrode material is 80% to 95%. It should be noted that the pores in the negative electrode material are mainly mesopores. When the battery made from the negative electrode material is charged and discharged, the mesopores in the negative electrode material can provide a buffer space for the expansion of the silicon material. On the other hand, it ensures the stress dispersion distribution in the negative electrode material. When the negative electrode material is used in lithium-ion batteries, it can improve the specific capacity of the negative electrode material, alleviate the volume expansion of the silicon material, improve the particle strength of the negative electrode material, and reduce the collapse and breakage of the material structure during electrode rolling or cycling. Thus, under the synergistic effect of the above overall structure, the cycle performance and electrochemical performance of the negative electrode material are improved.

[0032] In some embodiments, the silicon material includes at least one of elemental silicon, silicon oxide, and silicon alloy.

[0033] In some embodiments, the silicon material includes elemental silicon, which includes amorphous silicon and / or crystalline silicon; preferably, the elemental silicon includes amorphous silicon, which expands isotropically during lithium intercalation, thereby reducing the collapse of the pore structure, suppressing rapid capacity decay, and improving the lithium intercalation cycle performance of the anode material.

[0034] In some embodiments, the silicon material includes silicon oxide, the general formula of which is SiO. x Where 0 < x ≤ 2. Specifically, SiO x Specifically, it could be SiO 0.5 SiO 0.7 SiO 0.9 SiO, SiO 1.2 SiO 1.5 SiO 1.8 SiO 1.9 SiO2, etc., are not limited here.

[0035] In some embodiments, the silicon material includes a silicon alloy, which may be at least one of a silicon-lithium alloy, a silicon-magnesium alloy, etc., and is not limited thereto.

[0036] In some embodiments, the silicon material includes silicon particles and a silicon oxide layer on the surface of the silicon particles. The silicon oxide layer includes silicon oxide, the general formula of which is SiO. x Where 0 < x ≤ 2. Specifically, SiO x Specifically, it could be SiO 0.5SiO 0.7 SiO 0.9 SiO, SiO 1.2 SiO 1.5 SiO 1.8 SiO 1.9 SiO2, etc., are not limited here.

[0037] In some embodiments, the silicon material includes silicon particles and a silicon oxide layer on the surface of the silicon particles. The mass percentage of oxygen atoms in the silicon material, based on 100% of the silicon material's mass, is 1% to 18%. Specifically, the mass percentage of oxygen atoms in the silicon material can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, or any value within any two of the above ranges, and is not limited herein. Controlling the mass percentage of oxygen atoms in the silicon material within the above range is beneficial for forming a stable silicon oxide layer on the surface of the silicon particles, reducing direct contact between the silicon particles and the electrolyte, thereby reducing side reactions between the silicon particles and the electrolyte, and improving the cycle stability of the negative electrode material; it also ensures stable activity of the silicon material, increasing the specific capacity of the negative electrode material.

[0038] In some embodiments, the average particle size of the silicon material is 1 nm to 50 nm. Optionally, the average particle size of the silicon material can specifically be 1 nm, 2 nm, 5 nm, 10 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, or any value within the range of any two of the above values, and is not limited herein. The mechanical stress during silicon material expansion decreases as the particle size decreases, and the smaller size can shorten the electron and ion transport path. At the same time, the smaller size of the silicon material increases the gap between adjacent silicon materials, which can reserve space for the expansion of the silicon material. It is understood that when the average particle size of the silicon material is within the above range, the battery capacity of the lithium-ion battery can be guaranteed, and irreversible capacity loss can be reduced. Preferably, the average particle size of the silicon-based material is 1 nm to 10 nm.

[0039] In some embodiments, the morphology of the silicon material includes at least one of dot-like, spherical, ellipsoidal, and sheet-like shapes. The morphology of the silicon material can be selected according to actual needs and is not limited herein.

[0040] In some embodiments of this application, the average particle size of the carbon matrix is ​​5 μm to 10 μm, specifically 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm or any value within the range of any two of the above values, and is not limited herein.

[0041] In some embodiments of this application, the mass content of carbon in the carbon matrix is ​​greater than 95%, which is beneficial to improving the conductivity and overall performance of the negative electrode material. For example, the mass content of carbon in the carbon matrix may be 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.9%, 99.99%, or any value within the range of any two of the above values; no limitation is made herein.

[0042] In some embodiments of this application, the mass content of hydrogen in the negative electrode material is less than 4%, specifically it can be 0.1%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 3.8%, or any value within the range of any two of the above values, and is not limited here.

[0043] In some embodiments, the negative electrode material further includes a coating layer disposed on at least a portion of the surface of a carbon substrate and / or a silicon material. The coating layer includes a carbon material, comprising one or more of graphene, soft carbon, and hard carbon. The coating layer on the outer layer of the negative electrode material has good electrical conductivity, which can improve the conductivity of the negative electrode material. Furthermore, it can coat the active material exposed on the surface of the substrate, reducing the continuous oxidation of the exposed active material during storage, and minimizing the decrease in specific capacity and initial coulombic efficiency (ICE) of the negative electrode material. The coating layer can also reduce the direct contact between the active material and the electrolyte, improving the stability of the SEI film, thereby improving the initial coulombic efficiency of the negative electrode material.

[0044] In some embodiments, the coating layer can be a single-layer coating layer formed from a single material, a coating layer formed from a combination of multiple materials, a multi-layer coating layer formed from a single material, or a multi-layer coating layer formed from multiple materials, etc., and the layer structure of the coating layer can be selected according to actual needs. It is understood that when the coating layer has a multi-layer coating structure, the density is higher.

[0045] In some embodiments, the thickness of the coating layer is from 1 nm to 300 nm. For example, the thickness of the coating layer can be 1 nm, 30 nm, 50 nm, 150 nm, 200 nm, 250 nm, 300 nm, or any value within the range of any two of the above values. The coating layer can reduce the solubility of the negative electrode material, thereby reducing the amount of gas generated by the reaction of the dissolved active material with the electrolyte. Controlling the thickness of the coating layer within the above range is beneficial for maintaining the stability of the particle structure of the negative electrode material during cycling, reducing the amount of exposed active material on the surface of the negative electrode material, reducing the amount of SEI generated during charge and discharge due to exposed active material, and improving the specific capacity and electrochemical performance of the negative electrode material.

[0046] In some embodiments, the thickness of the coating layer is preferably 1 nm to 50 nm, and more preferably, the thickness of the coating layer is 1 nm to 30 nm, which is beneficial to the rapid and reversible insertion and extraction of lithium ions.

[0047] In some embodiments of this application, at least a portion of the silicon material is distributed within the carbon matrix. The silicon material embedded within the carbon matrix can, on the one hand, increase the specific capacity of the negative electrode material, and on the other hand, reduce the porosity of the silicon material after the carbon material fills the active material, thereby increasing the density of the negative electrode material. This effectively reduces the occurrence of side reactions between the battery and the electrolyte prepared from the negative electrode material, which is beneficial for improving the cycle performance and cycle expansion of the battery prepared from the negative electrode material.

[0048] In some of these embodiments, the pore volume of the carbon matrix is ​​0.6 cm³. 3 / g~1.2cm 3 / g, specifically 0.6cm 3 / g, 0.7cm 3 / g, 0.8cm 3 / g, 0.9cm 3 / g, 1cm 3 / g, 1.1cm 3 / g, 1.2cm 3 / g or any value within the range of any two of the above values, without limitation. The remainder after removing silicon material from particles with carbon matrix as the negative electrode material.

[0049] In some of these embodiments, the pore volume of the micropores in the carbon matrix is ​​0.4–0.7 cm³. 3 / g. Here, micropores refer to pores with a diameter less than 2 nm. For example, the pore volume of micropores in a carbon matrix can be 0.4 cm³. 3 / g, 0.45cm 3 / g, 0.5cm 3 / g, 0.55cm 3 / g, 0.6cm 3 / g, 0.65cm 3 / g, 0.7cm 3 / g or any value within the range of any two of the above values, without limitation. The remainder after removing silicon material from particles with carbon matrix as the negative electrode material.

[0050] The carbon matrix is ​​the remaining portion of the anode material particles after removing the silicon material. The method for removing silicon material from the anode material particles is as follows: Under stirring, 150 mL of a 20% HF acid solution is added dropwise to 10 g of anode material. This will generate SiF4 and H2 gases and release heat. After no more gas is generated, the supernatant acid solution is removed by centrifugation. Another 150 mL of a 20% HF acid solution is added to the anode material, and the mixture is stirred for 12 hours. The supernatant acid solution is removed again by centrifugation. The anode material is then washed with pure water until neutral and dried to obtain the anode material after removing the silicon material, i.e., the carbon matrix.

[0051] According to another typical embodiment of this application, a method for preparing a negative electrode material is provided, the method comprising the following steps: depositing silicon on porous carbon using a silicon source to obtain a first silicon-carbon intermediate, wherein the silicon deposition temperature is 450℃~750℃ and the time is 1h~6h; depositing carbon on the first silicon-carbon intermediate using a carbon source to obtain a second silicon-carbon intermediate; subjecting the second silicon-carbon intermediate to rapid thermal shock treatment to obtain a negative electrode material, wherein the rapid thermal shock temperature is 800℃~1200℃ and the time is 1min~5min.

[0052] The anode material preparation method of this application involves sequentially depositing porous carbon with silicon and then with carbon, followed by rapid thermal shock treatment. The rapid thermal shock process subjectes the material to high temperatures quickly, causing the crystalline silicon particles to expand rapidly. Due to uneven internal stress, the crystalline silicon becomes brittle and cracks into smaller particles, increasing the disorder of the silicon material. Simultaneously, the cracking of the silicon crystals provides tiny spaces for lithium-ion insertion, reducing the cycle expansion rate of the silicon-carbon anode material. The carbon matrix and surface-deposited carbon have lower hardness than crystalline silicon. During rapid thermal shock, their flexibility can withstand the stress changes caused by thermal expansion, and at high temperatures, local carbon atom reconstruction occurs, forming more locally graphitized carbon, increasing the graphitization degree and overall conductivity of the material, thereby improving the initial coulombic efficiency of the battery prepared from the anode material. The anode material prepared by the above method contains a carbon matrix and silicon material, and its graphitization degree G and silicon disorder degree S are... a The above relationship is satisfied: 0.64 < G*S a <3.0, with low cyclic expansion rate and high conductivity.

[0053] Specifically, the temperature of the rapid thermal shock can be 800℃, 820℃, 850℃, 870℃, 900℃, 920℃, 950℃, 980℃, 1000℃, 1020℃, 1050℃, 1080℃, 1100℃, 1120℃, 1150℃, 1180℃, or any value within the range of any two of the above values, without limitation. Specifically, the duration of the rapid thermal shock can be 1 min, 1.5 min, 2 min, 2.5 min, 3 min, 3.5 min, 4 min, 4.5 min, 5 min, or any value within the range of any two of the above values, without limitation. When the intensity of rapid thermal shock is insufficient, i.e., the temperature or time of rapid thermal shock treatment is too low, the effect on the silicon-carbon intermediate is relatively limited. Therefore, the improvement in conductivity and cycle expansion performance of the resulting anode material is limited. When the intensity of rapid thermal shock is too high (the temperature is too high and the duration is too long), on the one hand, the silicon crystal will expand excessively, and the excessive stress generated will cause the deposited carbon layer to be damaged. The specific surface area of ​​the resulting anode material will be excessively increased, resulting in excessive SEI formation. The first coulombic efficiency of the battery prepared from the anode material will decrease. On the other hand, the activity of silicon material in the anode material will increase, reacting with carbon material in the carbon matrix to produce silicon carbide, which will reduce the conductivity of the anode material and significantly reduce the capacity of the battery prepared from the anode material.

[0054] The porous carbon used as the starting material can be selected from existing technologies. In some embodiments of this application, the porous carbon is any one or more of biomass-based porous carbon, coal-based porous carbon, soft carbon, and resin-based porous carbon. The porous carbon of the above starting materials has relatively rich pores and has a relatively suitable pore volume and pore size distribution.

[0055] In some preferred embodiments of this application, the pore volume of the porous carbon is 0.6 cm³. 3 / g~1.2cm 3 / g (e.g., 0.6cm) 3 / g, 0.7cm 3 / g, 0.8cm 3 / g, 0.9cm 3 / g, 1cm 3 / g, 1.1cm 3 / g, 1.2cm 3 / g or any value within the range of any two of the above values ​​(not limited here), the pore volume of the micropores is 0.4–0.7 cm³. 3 / g (e.g., 0.4cm) 3 / g, 0.45cm 3 / g, 0.5cm 3 / g, 0.55cm 3 / g, 0.6cm 3 / g, 0.7cm 3 / g or any value within the range of any two of the above values, without limitation), with an average particle size of 5μm to 10μm (e.g., 5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 10μm or any value within the range of any two of the above values, without limitation), the prepared negative electrode material has better conductivity and cycle expansion rate.

[0056] The silicon source mentioned above is preferably a gaseous silicon source. The specific type of gaseous silicon source can be selected from existing technologies, and this application does not impose any particular limitation. For example, the silicon source includes any one or more of silane, silane, fumed silica nanoparticles, dichlorosilane, and trichlorosilane. The aforementioned gaseous silicon sources are beneficial for further improving the silicon disorder in the prepared anode material, thereby improving the performance of the anode material. In some embodiments of this application, the silicon source flow rate is 50 sccm to 500 sccm, which allows the silicon source to deposit at a more suitable rate, thereby improving the performance of the prepared anode material. Specifically, the silicon source flow rate can be 50 sccm, 100 sccm, 200 sccm, 300 sccm, 400 sccm, 450 sccm, 500 sccm, or any value within the range of any two of the above values, and is not limited here.

[0057] In some embodiments of this application, the silicon deposition temperature is 450℃~750℃, and the time is 1h~6h, which is beneficial to improving the deposition effect. The specific silicon deposition temperature can be 450℃, 480℃, 500℃, 520℃, 550℃, 580℃, 600℃, 620℃, 650℃, 680℃, 700℃, 720℃, 750℃, or any value within the range of any two of the above values, and is not limited herein. The silicon deposition time can be 1h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 6h, or any value within the range of any two of the above values, and is not limited herein.

[0058] The specific process for silicon deposition can be selected from existing technologies, such as deposition in an inert atmosphere to reduce oxidation during material deposition. In some embodiments of this application, to further improve the deposition effect and enhance the performance of the prepared anode material, the silicon source and porous carbon are preheated in an inert atmosphere before silicon deposition. The inert atmosphere can be nitrogen, helium, argon, etc., and the flow rate of the inert gas is 50 sccm to 500 sccm, for example, 100 sccm, 200 sccm, 300 sccm, 400 sccm, 450 sccm, or any value within the range of any two of the above values, without limitation. Controlling the inert gas flow rate within the above range not only provides a good inert gas atmosphere but also helps maintain the stability of the material, avoiding excessive airflow that could cause violent movement of the deposited material. In some typical embodiments, the silicon source and porous carbon are preheated in an inert atmosphere before silicon deposition. The preheating temperature of the porous carbon is 450°C to 750°C, such as 450°C, 500°C, 520°C, 550°C, 580°C, 600°C, 620°C, 650°C, 680°C, 700°C, 750°C, or any value within the range of any two of the above values, without limitation. The preheating temperature of the silicon source is 300°C to 450°C, such as 300°C, 350°C, 380°C, 400°C, 450°C, or any value within the range of any two of the above values, without limitation.

[0059] The carbon source for carbon deposition can also be selected from existing technologies, with gaseous carbon sources being preferred, such as any one or more of methane, ethane, propane, natural gas, acetylene, and ethylene.

[0060] In some embodiments of this application, the temperature for carbon deposition is 550°C to 750°C. Specifically, it can be 550°C, 600°C, 620°C, 650°C, 680°C, 700°C, 720°C, 750°C, or any value within the range of any two of the above values. No limitation is made here. Of course, it can also be other values ​​within the above range, which are not limited here.

[0061] In some embodiments of this application, the carbon deposition time is 2h to 6h, specifically 2h, 3h, 4h, 5h, 6h or any value within the range of any two of the above values, and is not limited here.

[0062] In some embodiments of this application, the carbon source and the first silicon-carbon intermediate are preheated in an inert atmosphere before carbon deposition. The inert atmosphere can be selected from existing technologies, such as nitrogen, helium, argon, etc. The flow rate of the inert gas can be 50 sccm to 500 sccm. Preferably, carbon deposition is also carried out in the aforementioned inert gas atmosphere. Preferably, the preheating temperature of the carbon source is 300 to 550°C, such as 300°C, 350°C, 380°C, 400°C, 420°C, 450°C, 470°C, 500°C, 550°C, or any value within the range of any two of the above values, without limitation. The preheating temperature of the first silicon-carbon intermediate is 550 to 750°C, such as 550°C, 600°C, 630°C, 650°C, 680°C, 700°C, 750°C, or any value within the range of any two of the above values, without limitation.

[0063] Regarding the specific process method for the aforementioned rapid thermal shock treatment, those skilled in the art can select from existing technologies. In some embodiments of this application, the heating rate of the rapid thermal shock treatment is 50℃ / s to 200℃ / s, specifically 50℃ / s, 60℃ / s, 70℃ / s, 80℃ / s, 90℃ / s, 100℃ / s, 110℃ / s, 120℃ / s, 130℃ / s, 140℃ / s, 150℃ / s, 160℃ / s, 170℃ / s, 180℃ / s, 190℃ / s, 200℃ / s, or any value within the range of any two of the above values, and is not limited herein.

[0064] In some embodiments of this application, the cooling rate of the rapid thermal shock treatment is 30℃ / s to 50℃ / s, specifically 30℃ / s, 32℃ / s, 34℃ / s, 36℃ / s, 38℃ / s, 40℃ / s, 42℃ / s, 44℃ / s, 46℃ / s, 50℃ / s, or any value within the range of any two of the above values, and is not limited herein. The rapid thermal shock treatment is preferably carried out in an inert gas atmosphere, wherein the inert gas can be nitrogen, helium, argon, etc. Preferably, the flow rate of the inert gas is 50 sccm to 200 sccm. For example, the flow rate of the inert gas can be 50 sccm, 60 sccm, 70 sccm, 80 sccm, 90 sccm, 100 sccm, 110 sccm, 120 sccm, 130 sccm, 140 sccm, 150 sccm, 160 sccm, 170 sccm, 180 sccm, 190 sccm, 200 sccm, or any value within the range of any two of the above values, and is not limited herein. According to another typical embodiment of this application, a negative electrode sheet is provided, which contains any of the above-mentioned negative electrode materials or a negative electrode material prepared by any of the above-mentioned methods for preparing negative electrode materials.

[0065] The graphitization degree G and silicon disorder degree S of the above-mentioned negative electrode material a The product of these factors is within the above range, resulting in superior conductivity and cyclic expansion rate. The negative electrode sheet of this application, due to the use of the aforementioned negative electrode material, exhibits high conductivity and is not prone to expansion.

[0066] According to another typical embodiment of this application, a battery is provided, which includes the aforementioned negative electrode sheet. Because this battery uses a negative electrode sheet containing the aforementioned negative electrode material, it has high conductivity, good cycle performance, is not easily expanded, and possesses good safety and a long service life.

[0067] The beneficial effects that this application can achieve will be further illustrated below with reference to embodiments and comparative examples.

[0068] Example 1

[0069] (1) In an argon atmosphere of 200 sccm, 200 sccm of silane was preheated at 450℃ in preheating chamber 1, resulting in an average particle size of 7.8 μm and a pore volume of 0.85 cm³. 3 / g, micropore volume is 0.45cm³ 3 / g of biomass porous carbon was simultaneously preheated at 600℃ in preheating chamber 2, and then the preheated silane was introduced into preheating chamber 2 to deposit silicon on the porous carbon at 600℃ for 6h to obtain silicon-carbon intermediate 1.

[0070] (2) Turn off the silicon source, and in a 200 sccm argon atmosphere, preheat 50 sccm of propane in preheating chamber 1 at 550°C. Simultaneously, preheat silicon-carbon intermediate 1 in preheating chamber 2 at 600°C. Then, introduce the preheated carbon source into preheating chamber 2 and perform carbon deposition on silicon-carbon intermediate 1 at 600°C for 2 hours to obtain silicon-carbon intermediate 2.

[0071] (3) The silicon-carbon intermediate 2 is placed in a rapid Joule heating device with an argon flow rate of 100 sccm, heated to 800℃ at a heating rate of 100℃ / s, subjected to rapid thermal shock treatment for 1 min, and then cooled to room temperature at a cooling rate of 40℃ / s to obtain the negative electrode material.

[0072] Example 2

[0073] (1) In an argon atmosphere of 200 sccm, 200 sccm of silane was preheated at 450℃ in preheating chamber 1, resulting in an average particle size of 7.8 μm and a pore volume of 0.85 cm³. 3 / g, micropore volume is 0.45cm³ 3 / g of biomass porous carbon was simultaneously preheated at 600℃ in preheating chamber 2, and then the preheated silane was introduced into preheating chamber 2 to deposit silicon on the porous carbon at 600℃ for 6h to obtain silicon-carbon intermediate 1.

[0074] (2) Turn off the silicon source, and in a 200 sccm argon atmosphere, preheat 50 sccm of propane in preheating chamber 1 at 550°C. Simultaneously, preheat silicon-carbon intermediate 1 in preheating chamber 2 at 600°C. Then, introduce the preheated carbon source into preheating chamber 2 and perform carbon deposition on silicon-carbon intermediate 1 at 600°C for 2 hours to obtain silicon-carbon intermediate 2.

[0075] (3) The silicon-carbon intermediate 2 is placed in a rapid Joule heating device with an argon flow rate of 100 sccm, heated to 1000℃ at a heating rate of 100℃ / s, subjected to rapid thermal shock treatment for 1 min, and then cooled to room temperature at a cooling rate of 40℃ / s to obtain the negative electrode material.

[0076] Example 3

[0077] (1) In an argon atmosphere of 200 sccm, 200 sccm of silane was preheated at 450℃ in preheating chamber 1, resulting in an average particle size of 7.8 μm and a pore volume of 0.85 cm³. 3 / g, micropore volume is 0.45cm³ 3 / g of biomass porous carbon was simultaneously preheated at 600℃ in preheating chamber 2, and then the preheated silane was introduced into preheating chamber 2 to deposit silicon on the porous carbon at 600℃ for 6h to obtain silicon-carbon intermediate 1.

[0078] (2) Turn off the silicon source, and in a 200 sccm argon atmosphere, preheat 50 sccm of propane in preheating chamber 1 at 550°C. Simultaneously, preheat silicon-carbon intermediate 1 in preheating chamber 2 at 600°C. Then, introduce the preheated carbon source into preheating chamber 2 and perform carbon deposition on silicon-carbon intermediate 1 at 600°C for 2 hours to obtain silicon-carbon intermediate 2.

[0079] (3) The silicon-carbon intermediate 2 is placed in a rapid Joule heating device with an argon flow rate of 100 sccm, heated to 1200℃ at a heating rate of 100℃ / s, subjected to rapid thermal shock treatment for 1 min, and then cooled to room temperature at a cooling rate of 40℃ / s to obtain the negative electrode material.

[0080] Example 4

[0081] (1) In an argon atmosphere of 200 sccm, 200 sccm of silane was preheated at 450℃ in preheating chamber 1, resulting in an average particle size of 7.8 μm and a pore volume of 0.85 cm³. 3 / g, micropore volume is 0.45cm³ 3 / g of biomass porous carbon was simultaneously preheated at 600℃ in preheating chamber 2, and then the preheated silane was introduced into preheating chamber 2 to deposit silicon on the porous carbon at 600℃ for 6h to obtain silicon-carbon intermediate 1.

[0082] (2) Turn off the silicon source, and in a 200 sccm argon atmosphere, preheat 50 sccm of propane in preheating chamber 1 at 550°C. Simultaneously, preheat silicon-carbon intermediate 1 in preheating chamber 2 at 600°C. Then, introduce the preheated carbon source into preheating chamber 2 and perform carbon deposition on silicon-carbon intermediate 1 at 600°C for 2 hours to obtain silicon-carbon intermediate 2.

[0083] (3) The silicon-carbon intermediate 2 is placed in a rapid Joule heating device with an argon flow rate of 100 sccm, heated to 1000℃ at a heating rate of 100℃ / s, subjected to rapid thermal shock treatment for 3 min, and then cooled to room temperature at a cooling rate of 40℃ / s to obtain the negative electrode material.

[0084] Example 5

[0085] (1) In an argon atmosphere of 200 sccm, 200 sccm of silane was preheated at 450℃ in preheating chamber 1, resulting in an average particle size of 7.8 μm and a pore volume of 0.85 cm³. 3 / g, micropore volume is 0.45cm³ 3 / g of porous carbon is simultaneously preheated at 600℃ in preheating chamber 2, and then the preheated silane is introduced into preheating chamber 2 to perform silicon deposition on the biomass porous carbon at 600℃ for 6h to obtain silicon-carbon intermediate 1.

[0086] (2) Turn off the silicon source, and in a 200 sccm argon atmosphere, preheat 50 sccm of propane in preheating chamber 1 at 550°C. Simultaneously, preheat silicon-carbon intermediate 1 in preheating chamber 2 at 600°C. Then, introduce the preheated carbon source into preheating chamber 2 and perform carbon deposition on silicon-carbon intermediate 1 at 600°C for 2 hours to obtain silicon-carbon intermediate 2.

[0087] (3) The silicon-carbon intermediate 2 is placed in a rapid Joule heating device with an argon flow rate of 100 sccm, heated to 1000℃ at a heating rate of 100℃ / s, subjected to rapid thermal shock treatment for 5 min, and then cooled to room temperature at a cooling rate of 40℃ / s to obtain the negative electrode material.

[0088] Example 6

[0089] The difference from Example 4 is that in step (1), the time for depositing biomass porous carbon is 4 hours.

[0090] Example 7

[0091] The difference from Example 4 is that in step (1), the flow rate of silane is 500 sccm when depositing porous carbon from biomass.

[0092] Example 8

[0093] The difference from Example 4 is that, in step (1), the porous carbon used is resin-based porous carbon with an average particle size of 7.5 μm and a pore volume of 0.9 cm³. 3 / g, micropore volume is 0.55cm³ 3 / g.

[0094] Example 9

[0095] The difference from Example 3 is that in step (1), silicon deposition is performed at 750°C for 6 hours.

[0096] Example 10

[0097] The difference from Example 3 is that in step (2), carbon deposition is performed at 750°C for 2 hours.

[0098] The difference between Example 11 and Example 5 is that the rapid thermal shock treatment (3) is performed twice.

[0099] The difference between Example 12 and Example 1 is that step (3) involves two rapid thermal shock treatments at 700°C.

[0100] Comparative Example 1

[0101] (1) In an argon atmosphere of 200 sccm, 200 sccm of silane was preheated at 450℃ in preheating chamber 1, resulting in an average particle size of 7.8 μm and a pore volume of 0.85 cm³. 3 / g, micropore volume is 0.45cm³ 3 / g of porous carbon is simultaneously preheated at 600℃ in preheating chamber 2, and then the preheated silane is introduced into preheating chamber 2 to deposit silicon on the porous carbon at 600℃ for 6h to obtain silicon-carbon intermediate 1.

[0102] (2) Turn off the silicon source, and in a 200 sccm argon atmosphere, preheat 50 sccm of propane in preheating chamber 1 at 550°C. Simultaneously, preheat silicon-carbon intermediate 1 in preheating chamber 2 at 600°C. Then, introduce the preheated carbon source into preheating chamber 2 and perform carbon deposition on silicon-carbon intermediate 1 at 600°C for 2 hours to obtain silicon-carbon intermediate 2.

[0103] (3) No rapid thermal shock treatment is performed.

[0104] Comparative Example 2

[0105] (1) In an argon atmosphere of 200 sccm, 200 sccm of silane was preheated at 450℃ in preheating chamber 1, resulting in an average particle size of 7.8 μm and a pore volume of 0.85 cm³. 3 / g, micropore volume is 0.45cm³ 3 / g of biomass porous carbon was simultaneously preheated at 600℃ in preheating chamber 2, and then the preheated silane was introduced into preheating chamber 2 to deposit silicon on the porous carbon at 600℃ for 6h to obtain silicon-carbon intermediate 1.

[0106] (2) Turn off the silicon source, and in a 200 sccm argon atmosphere, preheat 50 sccm of propane in preheating chamber 1 at 550°C. Simultaneously, preheat silicon-carbon intermediate 1 in preheating chamber 2 at 600°C. Then, introduce the preheated carbon source into preheating chamber 2 and perform carbon deposition on silicon-carbon intermediate 1 at 600°C for 2 hours to obtain silicon-carbon intermediate 2.

[0107] (3) The silicon-carbon intermediate 2 is placed in a rapid Joule heating device with an argon flow rate of 100 sccm, heated to 700℃ at a heating rate of 100℃ / s, subjected to rapid thermal shock treatment for 5 min, and then cooled to room temperature at a cooling rate of 40℃ / s to obtain silicon-carbon anode material.

[0108] Comparative Example 3

[0109] (1) In an argon atmosphere of 200 sccm, 200 sccm of silane was preheated at 450℃ in preheating chamber 1, resulting in an average particle size of 7.8 μm and a pore volume of 0.85 cm³. 3 / g, micropore volume is 0.45cm³3 / g of biomass porous carbon was simultaneously preheated at 600℃ in preheating chamber 2, and then the preheated silane was introduced into preheating chamber 2 to deposit silicon on the porous carbon at 600℃ for 6h to obtain silicon-carbon intermediate 1.

[0110] (2) Turn off the silicon source, and in a 200 sccm argon atmosphere, preheat 50 sccm of propane in preheating chamber 1 at 550°C. Simultaneously, preheat silicon-carbon intermediate 1 in preheating chamber 2 at 600°C. Then, introduce the preheated carbon source into preheating chamber 2 and perform carbon deposition on silicon-carbon intermediate 1 at 600°C for 2 hours to obtain silicon-carbon intermediate 2.

[0111] (3) The silicon-carbon intermediate 2 is placed in a rapid Joule heating device with an argon flow rate of 100 sccm, heated to 1300℃ at a heating rate of 100℃ / s, subjected to rapid thermal shock treatment for 1 min, and then cooled to room temperature at a cooling rate of 40℃ / s to obtain the silicon-carbon anode material.

[0112] Comparative Example 4

[0113] (1) The average particle size is 7.8 μm and the pore volume is 0.85 cm³. 3 / g, micropore volume is 0.45cm³ 3 / g of biomass porous carbon was placed in a graphitization device with an argon flow rate of 100sccm, heated to 1000℃ at a heating rate of 100℃ / h, and subjected to high-temperature graphitization for 2h. Then, it was cooled to room temperature at a cooling rate of 40℃ / s to obtain graphitized porous carbon.

[0114] (2) In an argon atmosphere of 200 sccm, 200 sccm of silane was preheated at 450°C in preheating chamber 1, and graphitized porous carbon was preheated at 600°C in preheating chamber 2. Then, the preheated silane was introduced into preheating chamber 2 to deposit silicon on the porous carbon at 600°C for 6 hours to obtain silicon-carbon intermediate 1.

[0115] (3) Turn off the silicon source, and in a 200 sccm argon atmosphere, preheat 50 sccm of propane in preheating chamber 1 at 550°C. Simultaneously, preheat silicon-carbon intermediate 1 in preheating chamber 2 at 600°C. Then, introduce the preheated carbon source into preheating chamber 2 and perform carbon deposition on silicon-carbon intermediate 1 at 600°C for 2 hours to obtain silicon-carbon anode material.

[0116] Comparative Example 5

[0117] The difference from Example 1 is that in step (1), 200 sccm of silane is preheated at 400°C in preheating chamber 1, resulting in an average particle size of 7.8 μm and a pore volume of 0.85 cm³. 3 / g, micropore volume is 0.45cm³ 3 / g of biomass porous carbon was simultaneously preheated at 400℃ in preheating chamber 2, and then the preheated silane was introduced into preheating chamber 2 to deposit silicon on the porous carbon at 400℃ for 10h to obtain silicon-carbon intermediate 1.

[0118] The anode materials prepared in the above examples and comparative examples were tested for basic indicators and electrochemical performance according to the following methods. The test results are listed in Tables 1 and 2.

[0119] (1) Test method for carbon content of negative electrode material or carbon matrix:

[0120] Using a Bruker / Elter G4 ICARUS HF / CS-i infrared carbon-sulfur analyzer, the sample was burned in a high-temperature, oxygen-rich environment. The carbon contained in the sample was oxidized into carbon dioxide, which then entered the infrared detector along with the carrier gas. The mass content of carbon was quantitatively calculated by statistically analyzing the changes in the intensity of the infrared absorption wavelength of the carbon dioxide signal.

[0121] (2) Test method for silicon content in negative electrode materials:

[0122] After drying the sample overnight, it was placed in a corundum crucible, and the crucible was placed in a muffle furnace at 1200℃ (Nanyang Xinyu S). A The carbon combustion and silicon or silicon suboxide to silicon dioxide reaction were completed in 2-9-17TP for 480 minutes. During the process, the crucible weight m0, sample weight m1, and total weight of crucible and product after ignition m2 were recorded. The silicon content was calculated according to the following formula: Si%=(m2-m0) / m1×28.09 / 60.09×100%.

[0123] (3) Test method for the conductivity of negative electrode material:

[0124] The conductivity at a pressure of 20 kN was tested using the MCP-PD51 powder resistivity testing system from Mitsubishi Chemical Corporation of Japan, and the volume resistivity of the sample was determined using the four-probe method. This instrument can measure the resistance of the powder, and then the computer automatically calculates the conductivity of the powder.

[0125] (4) Raman testing method for negative electrode materials:

[0126] Raman spectroscopy was performed on 20 sample particles of the negative electrode materials prepared in each embodiment and comparative example using a Renishaw inVia laser confocal Raman spectrometer, and the spectra were collected. After baseline processing, the average value was calculated to obtain I. D ,I G ,I 480 ,I 520 The intensity value is then used to obtain I. G / I D The values ​​of G and I 480 / I 520 The value S a The peak position of peak D is 1350±20cm. -1 The peak position of G is 1580±20cm. -1 I 480 The peak position is 480±10cm -1 I 520 The peak position is 520±10cm -1 .

[0127] (5) Test methods for surface area, pore volume, and pore volume ratio of micropores in negative electrode materials or carbon substrates:

[0128] Using the iPore620 pore size analyzer and the BET pore size distribution test method, the pore size distribution data of the material was obtained through DFT simulation analysis using the isothermal adsorption characteristic curve of nitrogen gas, and then the pore volume ratio, pore volume, and BET specific surface area of ​​the material were obtained.

[0129] (6) Test method for median particle size D50 of negative electrode material:

[0130] The particle size testing method refers to GB / T 19077-2016. The volume-based cumulative particle size distribution of the negative electrode material was measured by a Malvern laser particle size analyzer (Mastersizer3000) and laser diffraction method. D50 represents the particle size corresponding to a cumulative particle size distribution percentage of 50%.

[0131] (7) Methods for testing the average particle size of carbon-based or silicon materials:

[0132] The silicon material or carbon matrix in the negative electrode material is observed by field emission scanning electron microscopy or transmission electron microscopy. The particle size of 5-10 silicon material or carbon matrix particles is randomly measured using a scale bar, and the average particle size is taken as the final average particle size of the silicon material or carbon matrix.

[0133] (8) Test method for hydrogen content in negative electrode materials:

[0134] Referring to the determination of hydrogen content in steel - inert gas pulse melting thermal conductivity method GB / T223.82-2007, the sample is melted in an inert atmosphere while being coated with flux. The hydrogen element contained in the sample decomposes to form stable elemental hydrogen gas. The generated hydrogen gas enters the thermal conductivity detector of the German Fold ONH 2000 oxygen, nitrogen and hydrogen element analyzer along with the carrier gas. The hydrogen content is calculated by quantitatively analyzing the change in heat in the thermal conductivity cell.

[0135] (9) Test method for coating thickness: The material is cross-sectioned using FIB-SEM equipment. Ten particles are randomly selected in the SEM, and the coating thickness of each particle is measured three times. The coating thickness is then calculated.

[0136] (10) Electrochemical performance testing:

[0137] A negative electrode slurry was prepared by mixing negative electrode material, conductive carbon black, and acrylonitrile copolymer (LA133) in a mass ratio of 70:15:15. This slurry was then coated onto copper foil with a thickness of d0. After drying, a negative electrode sheet with a thickness of d1 was formed. A coin cell was assembled in an Ar-filled glove box using a lithium metal sheet as the counter electrode, a 1 mol / L LiPF6 / ethylene carbonate + dimethyl carbonate + methyl ethyl carbonate (v / v = 1:1:1) electrolyte, and a Celgard 2400 separator. The coin cells were then subjected to cycle performance tests on a Blue Electric CT2001A battery testing system at room temperature (25℃±2℃).

[0138] The coin cell was charged and discharged at a current density of 0.1C within a charge-discharge range of 0.01-5V to obtain the initial reversible specific capacity and initial coulombic efficiency of the coin cell.

[0139] The button cell was subjected to 50 repeated charge-discharge cycles at a current density of 1C within the charge-discharge range of 0.01V-5V. The electrode thickness d2 after 50 cycles was obtained, and the electrode expansion rate was calculated as (d2-d0) / (d1-d0)*100%.

[0140] Table 1 Performance parameters of the anode material

[0141] Table 2 Performance parameters of the anode material (carbon matrix) after removing silicon material

[0142] Table 3 Electrochemical performance parameters of the anode material

[0143] Based on the above test data, and by comparing Examples 1 to 3, it can be seen that as the thermal shock temperature increases, the amount of disordered silicon (silicon disorder degree S) generated in the prepared anode material increases. a As carbon graphitization degree (G) increases, the conductivity and initial coulombic efficiency of the anode material increase, while the cycle expansion rate decreases.

[0144] Comparing the test data from Examples 2, 4, and 5, it can be seen that as the duration of rapid thermal shock treatment increases, the amount of disordered silicon (silicon disorder degree S) generated in the prepared anode material increases. a As carbon graphitization degree (G) increases, the conductivity and initial coulombic efficiency of silicon-carbon anode materials rise, while the cycle expansion rate decreases and the capacity slightly decreases.

[0145] In Example 11, two thermal shock treatments were performed, which increased the silicon disorder degree Sa and the carbon graphitization degree G. The higher graphitization degree made it difficult to release the expansion stress of disordered silicon, and the expansion of the anode material was aggravated during lithium intercalation.

[0146] Example 12 underwent two low-temperature thermal shock treatments, which slightly increased the graphitization degree G, but the increase in disordered silicon (silicon disorder Sa) was limited; it still had an excessively high expansion rate compared to Example 1.

[0147] Compared to Example 1, the negative electrode material prepared in Comparative Example 1 did not undergo rapid thermal shock treatment, and the graphitization degree G and silicon disorder degree S of the prepared negative electrode material were different. a The initial reversible specific capacity of the battery prepared with the negative electrode material in Comparative Example 1 was slightly higher, but the conductivity of the negative electrode material prepared in Comparative Example 1 was significantly lower. Consequently, the initial coulombic efficiency of the battery prepared with the negative electrode material in Comparative Example 1 was lower, and the cycle expansion rate was poorer.

[0148] Compared to Example 1, Comparative Example 2 underwent insufficient rapid thermal shock (lower temperature), resulting in a lower degree of graphitization G and silicon disorder S in the prepared negative electrode material. a All are low, G*S a If the value is less than 0.64, the performance improvement of the prepared anode material is limited and still cannot meet the application requirements.

[0149] Compared to Example 1, Comparative Example 3 subjected the rapid thermal shock to excessive intensity (excessively high temperature), causing the silicon crystals to expand excessively. The excessive stress generated by the silicon crystals led to the destruction of deposited carbon, resulting in an excessively large specific surface area of ​​the negative electrode material prepared in Comparative Example 3. Consequently, the initial coulombic efficiency of the battery prepared from the negative electrode material obtained in Comparative Example 3 decreased. Furthermore, the activity of the silicon material in the negative electrode material obtained in Comparative Example 3 increased, making it easier for the silicon material to react with the carbon in the carbon matrix to produce silicon carbide, which led to a decrease in the conductivity of the negative electrode material and a significant reduction in the capacity of the battery prepared from the negative electrode material.

[0150] Compared to Example 1, Comparative Example 4 involved graphitizing the carbon-based raw materials. The anode material prepared in Comparative Example 4 had a higher degree of graphitization, but the disorder of the silicon material in the anode material was lower. (G*S) a A value less than 0.64 leads to a significant decrease in the capacity of batteries made from negative electrode materials and a high rate of cycle expansion.

[0151] Compared to Example 1, Comparative Example 5 performed silicon deposition at a lower temperature. Lower temperatures result in a slower silicon deposition rate and a higher degree of silicon disorder; that is, a lower yield is traded for excessively high disorder in the deposition. a Silicon, silicon disorder S a When the concentration is too high, silicon becomes highly reactive, and some silicon readily reacts with carbon materials during carbon deposition to form silicon carbide, ultimately leading to a decrease in the capacity of the anode material.

[0152] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A negative electrode material, characterized in that, Including carbon-based and silicon-based materials, The negative electrode material was subjected to Raman spectroscopy, and the negative electrode material was spectrally analyzed at 1580±20 cm⁻¹. -1 The location contains a graphitized carbon G peak, the intensity of which is I. G , at 1350±20cm -1 The location has a disordered carbon D peak, the intensity of which is I. D , at 480±10cm -1 The location has disordered silicon peaks, the intensity of which is I. 480 520±10cm -1 The location has a crystalline silicon peak, the intensity of which is I. 520 ; Let G represent the degree of graphitization of the negative electrode material, G = I. G / I D ; Use S a S represents the silicon disorder degree of the negative electrode material. a =I 480 / I 520 ; The negative electrode material satisfies the following relationship: 0.64 < G*S a <3.

0.

2. The negative electrode material according to claim 1, characterized in that, It meets at least one of the following technical features: (1)0.95<G*S a <3.0; (2)G*S a The value is 0.65, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 2.95, or any value within the range of any two of the above values.

3. The negative electrode material according to claim 1, characterized in that, It meets at least one of the following technical features: (1) The degree of graphitization G of the negative electrode material conforms to 0.8 < G < 1.2; (2) The silicon disorder S of the negative electrode material a Conforms to 0.8 < S a <2.5; (3) The silicon disorder S of the negative electrode material a Conforms to 1.0 < S a <2.

4.

4. The negative electrode material according to claim 1, characterized in that, It meets at least one of the following technical features: (1) The silicon content in the negative electrode material is 30% to 60%; (2) The carbon content in the negative electrode material is 40% to 70%.

5. The negative electrode material according to claim 1, characterized in that, It meets at least one of the following technical features: (1) The silicon material includes at least one of elemental silicon, silicon oxide and silicon alloy; (2) The silicon material includes elemental silicon, which includes amorphous silicon and / or crystalline silicon; (3) The silicon material includes silicon oxide, and the general formula of the silicon oxide is SiO. x ; (4) The silicon material includes a silicon alloy, and the silicon alloy includes at least one of a silicon-lithium alloy and a silicon-magnesium alloy; (5) The average particle size of the silicon material is 1 nm to 50 nm.

6. The negative electrode material according to claim 1, characterized in that, It meets at least one of the following technical features: (1) The specific surface area of ​​the negative electrode material is less than 100 m². 2 / g; (2) The median particle size D50 of the negative electrode material is 5μm to 10μm.

7. The negative electrode material according to claim 1, characterized in that, It meets at least one of the following technical features: (1) The pore volume of the negative electrode material is less than or equal to 0.05 m³. 3 / g; (2) The negative electrode material has micropores, and the pore volume of the micropores accounts for 25% to 45% of the total pore volume of the negative electrode material.

8. The negative electrode material according to claim 1, characterized in that, At least a portion of the silicon material is distributed within the carbon matrix.

9. The negative electrode material according to claim 1, characterized in that, The carbon matrix satisfies at least one of the following technical features: (1) The average particle size of the carbon matrix is ​​5 μm to 10 μm; (2) The carbon matrix contains more than 95% carbon by mass; (3) The pore volume of the carbon matrix is ​​0.6 cm³. 3 / g~1.2cm 3 / g; (4) The pore volume of the micropores in the carbon matrix is ​​0.4–0.7 cm³. 3 / g.

10. The negative electrode material according to claim 1, characterized in that, The hydrogen content in the negative electrode material is less than 4% by mass.

11. The negative electrode material according to any one of claims 1 to 10, characterized in that, It meets at least one of the following technical features: (1) The negative electrode material further includes a coating layer, which is disposed on at least a portion of the surface of the carbon matrix and / or the silicon material; (2) The negative electrode material further includes a coating layer, the coating layer including a carbon material, the carbon material including one or more of graphene, soft carbon and hard carbon; (3) The negative electrode material further includes a coating layer, the thickness of which is 1 nm to 300 nm.

12. The negative electrode material according to claim 1, characterized in that, At least a portion of the silicon material is distributed within the carbon matrix.

13. A negative electrode sheet, characterized in that, It contains the negative electrode material according to any one of claims 1 to 12.

14. A battery, characterized in that, Includes the negative electrode sheet as described in claim 13.

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