Negative electrode material and electrochemical device

Abstract

Provided in the present application are a negative electrode material and an electrochemical device. The negative electrode material comprises a silicon-containing material and a carbon-containing material, and the negative electrode material has a pore structure, the pore structure having the following distribution characteristics: using the BET method to test the negative electrode material, it is measured that the negative electrode material has a first pore structure having a pore size of 2 nm-20 nm and a second pore structure having a pore size of 20 nm-80 nm; the pore volume of the first pore structure is V1, the pore volume of the second pore structure is V2, and the specific surface area of the negative electrode material is S, where 0.1 μm≥(V1+V2) / S≥0.01 μm, 0.8≥V1 / V2≥0.01, and 10.0 m2 / g≥S≥0.1 m2 / g. The present application improves the capacity, rate performance, cycle efficiency, and performance under high-temperature and low-temperature conditions of the negative electrode material by optimizing the pore structure of the negative electrode material.

Description

Anode materials and electrochemical devices

[0001] This application claims priority to Chinese Patent Application No. 202411131889.7, filed with the State Intellectual Property Office of China on August 19, 2024, entitled "Anode Material and Preparation Method Thereof, Electrochemical Device", the contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of electrochemical energy storage, specifically to a negative electrode material and an electrochemical device. Background Technology

[0003] In recent years, lithium-ion batteries have been widely used in various fields. With breakthroughs in the research and development of cathode materials with high specific capacity and high voltage, traditional graphite-based anode materials can no longer meet the performance requirements of next-generation lithium-ion batteries, and anode materials with higher capacity and better performance urgently need to be developed. Compared with graphite, elemental silicon is considered an ideal anode material to replace graphite due to its higher theoretical specific capacity and suitable operating voltage. However, the large volume expansion in the alloying / dealloying reaction of elemental silicon with lithium leads to rapid capacity decay in electrochemical devices (e.g., lithium-ion batteries).

[0004] In related technologies, silicon is dispersed in porous carbon materials to prepare silicon-carbon anode materials in order to alleviate the volume expansion of silicon. However, the above-mentioned silicon-carbon anode materials have poor conductivity, uneven silicon dispersion in porous carbon materials, low silicon deposition in porous carbon materials, and are prone to side reactions with electrolytes, causing the dissolution of active components inside the silicon-carbon anode material. As a result, the volume expansion and electrochemical performance of silicon-carbon anode materials are still not ideal and need to be improved.

[0005] Application content

[0006] This application provides a negative electrode material that can reduce volume expansion, improve conductivity, rate performance, and cycle stability.

[0007] In addition, embodiments of this application also provide a method for preparing the aforementioned negative electrode material and an electrochemical device including the aforementioned negative electrode material.

[0008] This application provides a negative electrode material, including a silicon-containing material and a carbon-containing material, wherein the negative electrode material has a porous structure, and the porous structure has the following distribution characteristics:

[0009] The negative electrode material was tested using the BET method. The results showed that the negative electrode material has a first pore structure with a pore size of 2nm to 20nm and a second pore structure with a pore size of 20nm to 80nm. The pore volume of the first pore structure is V1, and the pore volume of the second pore structure is V2. The specific surface area of ​​the negative electrode material is S, where 0.1μm ≥ (V1 + V2) / S ≥ 0.01μm, 0.8 ≥ V1 / V2 ≥ 0.01, and 10.0m... 2 / g≥S≥0.1m 2 / g.

[0010] This application also provides an electrochemical device, which includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the negative electrode includes a negative electrode active material, and the negative electrode active material includes the negative electrode material as described above.

[0011] Compared to existing technologies, the negative electrode material provided in this application has specific pore structure distribution characteristics. The ratio of the total pore volume of the first and second pore structures to the specific surface area of ​​the negative electrode material ((V1+V2) / S) represents the homogenization depth of the pore structure. Suitable homogenization depth ((V1+V2) / S), the pore volume ratio of the first and second pore structures (V1 / V2), and the specific surface area (S) of the negative electrode material can improve lithium-ion transport efficiency by adjusting the diffusion flux and diffusion depth of the electrolyte and slurry in the negative electrode material, thereby improving the rate performance of the negative electrode material. At the same time, due to the suitable pore structure, the negative electrode material can still maintain good lithium-ion diffusion ability under high and low temperature environments, exhibiting excellent high and low temperature performance. Attached Figure Description

[0012] Figure 1 is a process flow diagram of the preparation method of the negative electrode material provided in the embodiment of this application.

[0013] Figure 2 is a schematic diagram of the electrochemical device provided in the embodiment of this application. Detailed Implementation

[0014] The following are preferred embodiments of the present application. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principles of the embodiments of the present application, and these improvements and modifications are also considered to be within the protection scope of the embodiments of the present application.

[0015] This application provides an anode material comprising silicon-containing and carbon-containing materials. The anode material has a porous structure with the following distribution characteristics: Using the BET method, the anode material is found to have a first pore structure with a pore size of 2nm to 20nm and a second pore structure with a pore size of 20nm to 80nm. The pore volume of the first pore structure is V1, the pore volume of the second pore structure is V2, and the specific surface area of ​​the anode material is S, where 0.1μm ≥ (V1 + V2) / S ≥ 0.01μm, 0.8 ≥ V1 / V2 ≥ 0.01, and 10.0m... 2 / g≥S≥0.1m 2 / g.

[0016] The ratio of the total pore volume of the first and second pore structures in the negative electrode material to the specific surface area of ​​the negative electrode material is 0.1μm ≥ (V1 + V2) / S ≥ 0.01μm. This ratio represents the homogenization depth of the pore structure of the negative electrode material. Standardizing pore structures with different pore sizes reflects the diffusion depth of the electrolyte in the negative electrode material, affecting the lithium-ion transport speed within the pore channels. When this depth is too large (greater than 0.1μm), the electrolyte wetting efficiency is low, and the lithium-ion transport efficiency is significantly reduced. When this depth is too small (less than 0.01μm), it leads to uncontrolled electrolyte wetting, causing the electrolyte to rapidly enter the interior of the negative electrode material, resulting in excessive oxidation of the active material and gas production. This leads to problems such as reduced structural stability, cycle stability, and rate performance of the negative electrode material. Therefore, by adjusting the ratio of the pore structure volume to the specific surface area of ​​the negative electrode material within the above range, a suitable pore structure depth value can be obtained, which helps to balance the lithium-ion transport performance, promote the transport of lithium-ions inside the negative electrode material, and thus improve the stability and rate performance of the negative electrode material.

[0017] Maintaining the pore volume ratio (V1 / V2) of the first to second pore structures in the anode material within the range of 0.01 to 0.8 can effectively adjust the hydrophilicity of the anode material particles and further improve its low-temperature and rate performance. This is because a pore volume distribution within this range can effectively expand the lithium-ion transport interface while shortening the lithium-ion transport path, thereby reducing lithium-ion transport resistance, improving lithium-ion transport efficiency, and enhancing the rate performance of the anode material. Furthermore, even in low-temperature environments with low lithium-ion transport efficiency, the anode material can still maintain good lithium-ion diffusion capabilities, exhibiting excellent low-temperature performance. In addition, a reasonable pore volume distribution can simultaneously adjust the wettability of the anode material in both polar and non-polar solvents.

[0018] As mentioned earlier, pore volume distribution affects the wettability of electrolytes and polar solvents. Specifically, taking a pore size of 20 nm as the boundary, the first pore structure with a pore size of 2 nm to 20 nm (excluding 20 nm) includes micropores (2 to 5 nm) and mesopores (5 nm to 20 nm, excluding 20 nm) that are close to the size of micropores. The presence of the first pore structure results in a slower electrolyte wetting rate and a greater increase in the specific surface area of ​​the negative electrode material. However, if the proportion of the first pore structure is too high, it will lead to particle agglomeration, reduced rate performance, and electrolyte degradation. It will also further cause the pore structure to close, resulting in excessive local thickness of the SEI and affecting the lithium-ion transport path. Secondary pore structures with pore sizes in the range of 20 nm to 80 nm include mesopores (20 nm to 50 nm) and macropores (50 nm to 80 nm) that are close to the size of mesopores. The presence of secondary pore structures is beneficial for balancing the specific surface area of ​​the negative electrode material, improving wetting efficiency, improving the uniformity of electrolyte degradation, forming a stable and uniform SEI, and optimizing the lithium-ion transport path. However, an excessive proportion of secondary pore structures may cause the slurry to diffuse rapidly in the negative electrode material during the preparation of the electrochemical device, resulting in side reactions with the active components, which may lead to particle pulverization during cycling and reduce cycling performance. If the proportion of secondary pore structures is too small, it will reduce the electrolyte wetting efficiency and will not help to alleviate the volume expansion effect during charging and discharging.

[0019] In some implementations, V1 / V2 is 0.01, 0.03, 0.05, 0.08, 0.1, 0.2, 0.3, 0.5, 0.6, 0.7, 0.8 or within any two of the above values; controlling V1 / V2 within the range of 0.01 to 0.8 is also beneficial for balancing the electrolyte wetting rate of the negative electrode material.

[0020] The specific surface area S of the negative electrode material ranges from 10.0 m². 2 / g≥S≥0.1m 2 Specific surface area (S) is a key factor in mass transfer and reaction between the negative electrode material and the electrolyte. A specific surface area within the aforementioned range provides more active reaction sites and channels for the negative electrode material, which is beneficial for lithium-ion adsorption and diffusion rates, accelerates charge and discharge rates, and improves the performance of the prepared battery.

[0021] In some implementations, S is 0.1m. 2 / g, 0.5m 2 / g、1m 2 / g、2m 2 / g、3m 2 / g、4m 2 / g、5m 2 / g、6m 2 / g、7m 2 / g、8m 2 / g、9m2 / g, 10m 2 / g or within the range of any two of the above values.

[0022] In some implementations, (V1+V2) / S is 0.01μm, 0.02μm, 0.03μm, 0.04μm, 0.05μm, 0.06μm, 0.07μm, 0.08μm, 0.09μm, 0.1μm, or within the range of any two of the above values.

[0023] Therefore, the V1, V2, and S of the negative electrode material are controlled within the following ranges: 0.1 μm ≥ (V1 + V2) / S ≥ 0.01 μm, 0.8 ≥ V1 / V2 ≥ 0.01, 10.0 μm 2 / g≥S≥0.1m 2 By homogenizing the pore structure depth value, it can be found that the electrolyte wetting efficiency is best in the depth range of 0.01μm to 0.1μm, which is conducive to balancing the uniformity of electrolyte degradation, forming a stable and uniform SEI, optimizing the lithium ion transport path, and thus improving the stability and rate performance of the anode material.

[0024] Furthermore, the hole structure described above can be satisfied by adjusting the hole volumes of the first and second hole structures. In some embodiments, the hole volume V1 can be 0.5 cm³. 3 / g≥V1≥0.001cm 3 / g, V1 within the above range can shorten the lithium-ion transport path, which is beneficial to improving the diffusion rate of lithium ions inside the negative electrode material.

[0025] In some embodiments, the pore volume V2 can be 5.0 cm². 3 / g≥V2≥0.01cm 3 / g, the V2 within the above range provides sufficient space for electrolyte wetting and anode material volume expansion, increases the adsorption and release rate of lithium ions, and improves the structural stability of anode material.

[0026] The aforementioned pore structure of the negative electrode material determines its hydrophilicity and oleophilicity, affecting its dispersion in the slurry during battery fabrication and the wetting depth of the electrolyte during electrochemical reactions, thus impacting the performance of the battery ultimately fabricated from the negative electrode material. In the embodiments of this application, the negative electrode material possesses the aforementioned pore structure, which can improve the solid-liquid reaction efficiency on the negative electrode material surface, including lithium-ion diffusion efficiency, ion diffusion flux, and diffusion depth, thereby improving the storage performance and rate performance of batteries fabricated from the negative electrode material under high and low temperature conditions.

[0027] In some embodiments, the range of the volume distribution particle size D50 of the negative electrode material can be 2.0 μm to 15.0 μm, and further can be 4.0 μm to 10.0 μm. Exemplarily, the volume distribution particle size D50 of the negative electrode material can be 2.0 μm, 3.0 μm, 4.0 μm, 5.0 μm, 6.0 μm, 7.0 μm, 8.0 μm, 9.0 μm, 10.0 μm, 11.0 μm, 12.0 μm, 13.0 μm, 14.0 μm or 15.0 μm, etc. Controlling the particle size of the negative electrode material within the above range helps to ensure the consistency of the negative electrode material, thereby improving the performance stability of the negative electrode material; it can also increase the specific surface area of the negative electrode material, which helps to improve the transport rate of lithium ions in the negative electrode material and the reaction activity of the electrode; at the same time, it reduces the particle size of the negative electrode material being too low (less than 2 μm), thereby reducing the volume expansion of the negative electrode material during light charge and discharge, which is beneficial to maintaining the structural stability and cycle life of the negative electrode material.

[0028] In some embodiments, the negative electrode material can mainly include silicon-containing materials and carbon-containing materials, and the phases can mainly include elemental silicon, silicon oxides, silicates or elemental carbon-based materials, etc.

[0029] In some embodiments, the total mass of the silicon-containing material and the carbon-containing material can account for 40% to 97.5% of the total mass of the negative electrode material, and further can be 40% to 90%, and further can be 40% to 80%. Exemplarily, it can be 40%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85% or 90%, etc. Limiting the total mass ratio of the silicon-containing material and the carbon-containing material ensures that the composition of the negative electrode powder material is within a certain range, which helps to control the chemical composition of the negative electrode material and ensure the performance of the negative electrode material is stable and reliable in the electrochemical device.

[0030] In some embodiments, the chemical general formula of the silicon oxide is SiO x , where 0 < x ≤ 2. Exemplarily, x can be 0.05, 0.11, 0.21, 0.26, 0.31, 0.41, 0.51, 0.59, 0.61, 0.69, 0.71, 0.74, 0.76, 0.79, 0.89, 0.99, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2, etc., which is not limited herein. Further, 0 < x < 1. The silicon oxide can be a material formed by silicon particles dispersed in SiO2, or a material having a tetrahedral structural unit, where the silicon atom is located at the center of the tetrahedral structural unit, and the silicon atom and / or oxygen atom are located at the four vertices of the tetrahedral structural unit.

[0031] In some embodiments, the mass of carbon element accounts for 1.5% to 45.5% of the total mass of the negative electrode material, and may further be 5% to 40%, and may be exemplary 1.5%, 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 45.5%, etc.

[0032] In some embodiments, the negative electrode material includes a carbon coating layer, for example, with a silicon-containing material as the core and a carbon material forming a carbon coating layer on the surface of the core, thereby forming the main body of the negative electrode material. The carbon coating layer has several advantages. First, it helps to prevent direct contact between the active silicon material in the core and the slurry, suppressing side reactions and reducing SEI overgrowth, loss of active silicon and lithium, and improving the capacity and first-time efficiency of the anode material. Second, the silicon core has poor conductivity, and the carbon coating layer helps to form a conductive network, improving the conductivity of the anode material. The coating layer also ensures contact of the conductive network during cycling, reducing the formation of active materials such as "dead silicon" that detach from the conductive network and improving the cycling performance of the anode material. Third, the carbon coating layer provides a stable physical interface, suppressing excessive particle expansion. It also serves as a framework for SEI growth, forming a stable SEI layer, further stabilizing the solid-liquid interface, suppressing expansion, and improving safety. Fourth, the coating layer can further regulate the surface pore structure. By adjusting the coating process parameters and controlling the specific surface area, it can improve rate performance and high / low temperature performance. It can also reasonably construct an expansion buffer space, reducing the deformation of the anode material.

[0033] In some embodiments, the anode material may further include one or more doping elements. Specifically, the doping elements may include at least one of hydrogen, oxygen, lithium, magnesium, aluminum, nitrogen, phosphorus, sulfur, boron, fluorine, molybdenum, sodium, potassium, calcium, titanium, niobium, lanthanum, tin, selenium, and cerium. Element doping of the anode material can optimize its structure and performance, and improve its cycle life and safety. Doping elements (e.g., doping with hydrogen, oxygen, lithium, nitrogen, phosphorus, boron, sulfur, fluorine, sodium, potassium, calcium, titanium, niobium, tin, selenium, or cerium) can improve the electrochemical performance of the anode material, including increasing lithium-ion storage capacity, increasing conductivity, and reducing electrode polarization, thereby improving battery performance and cycle life. Some doping elements (such as magnesium, aluminum, or lanthanum) can slow down the volume expansion of the anode material during lithium-ion insertion / extraction, reducing material loss and structural damage, thereby improving the cycle life of the anode material.

[0034] In some embodiments, the content of the dopant element in the negative electrode material can be 25 ppm to 120,000 ppm, more specifically 50 ppm to 80,000 ppm, and further specifically 100 ppm to 50,000 ppm. Exemplary values ​​include 25 ppm, 50 ppm, 100 ppm, 500 ppm, 1000 ppm, 5000 ppm, 10000 ppm, 30,000 ppm, 50,000 ppm, 75,000 ppm, 80,000 ppm, 100,000 ppm, or 120,000 ppm. Controlling the content of the dopant element in the negative electrode material within the above range can optimize the structure and performance of the negative electrode material. If the content is too low (below 25 ppm), it may not achieve the goal of optimizing electrochemical performance, leading to reduced storage capacity, decreased conductivity, and reduced structural stability of the negative electrode material. If the content is too high (above 120,000 ppm), it may lead to problems such as deterioration of the electrochemical performance of the negative electrode material, impaired structural stability, and increased cost.

[0035] In some embodiments, the oil absorption value of the negative electrode material can be 25 mL / 100g to 85 mL / 100g, more specifically 35 mL / 100g to 75 mL / 100g, and exemplary values ​​include 25 mL / 100g, 35 mL / 100g, 45 mL / 100g, 55 mL / 100g, 65 mL / 100g, 75 mL / 100g, or 85 mL / 100g. The testing method involves dripping oil into the negative electrode material at a constant rate while simultaneously stirring at a constant speed. The viscosity of the mixture of oil and negative electrode material gradually increases and reaches a peak. The oil absorption value of the negative electrode material is calculated based on the amount of oil dripped at 70% of the maximum torque. An oil absorption value within the above range is beneficial for the production and processing of the negative electrode material, ensuring its wetting ability with the electrolyte, improving lithium-ion conductivity, and enhancing the electrochemical performance of the negative electrode material. Furthermore, it ensures the stability and safety of the battery while maintaining its performance and cycle life.

[0036] In some embodiments, the pH value of the negative electrode material can be 7.5–12.0, more specifically 9–11, and exemplary values ​​can be 7.5, 8, 9, 10, 11, or 12. The pH value at which the negative electrode material is stable in water is tested according to GB / T 24533-2019. The pH value of the negative electrode material can affect the interfacial reaction and interaction between the electrode and the electrolyte. pH values ​​within the aforementioned range are beneficial for improving the stability and cycle life of the negative electrode material, as well as facilitating control and quality management during the production process.

[0037] In some embodiments, the isothermal adsorption hysteresis integral area of ​​the negative electrode material can be 1.0 × 10⁻⁶. -4 ~5.0×10-2 The isothermal curves obtained by testing the pore size distribution of the negative electrode material according to GB / T 21650.3-2011 method were used to calculate the integral area of ​​the isothermal adsorption hysteresis loop of the negative electrode material. The test procedure was as follows: N2 reached adsorption and desorption equilibrium at different relative pressures under liquid nitrogen (77K, -196℃). The integral area of ​​the isothermal adsorption hysteresis curve is an important parameter for evaluating the pore structure and specific surface area of ​​the negative electrode material. Further controlling the values ​​of the pore structure and specific surface area of ​​the negative electrode material within the above range helps to control the interfacial side reactions of the negative electrode powder and improve the cycle capacity retention rate of the negative electrode material.

[0038] In some embodiments, the pore size range of the negative electrode material can be 0.5 nm to 300 nm, more specifically 2 nm to 150 nm, and even further specifically 2 nm to 80 nm. The pore size distribution of the negative electrode material is obtained using BJH, HK, and DFT models based on the isotherms of the adsorption and desorption branches. The pore size range of the negative electrode material is 0.5 nm to 300 nm, where smaller pore sizes can provide a higher specific surface area, while larger pore sizes are beneficial for ion penetration and diffusion.

[0039] Compared with the prior art, the negative electrode material provided in this application has the following beneficial effects:

[0040] 1. The anode material has a pore structure with a nanoscale pore size distribution (first pore structure and second pore structure). A reasonable pore size distribution can balance the pore volume and specific surface area of ​​the anode material to obtain a suitable pore structure depth, thereby controlling the wetting efficiency of the electrolyte on the anode material, balancing the uniformity of electrolyte degradation, forming a stable and uniform SEI, optimizing the lithium ion transport path, and mitigating volume expansion. This improves the capacity, rate performance, structural stability, cycle efficiency, and storage performance and electrochemical performance of the anode material under high and low temperature conditions.

[0041] 2. The carbon coating layer in the anode material can reduce the loss of active silicon and active lithium, thereby improving the capacity and first-time efficiency of the anode material. The carbon coating layer also facilitates the formation of a conductive network, which can improve the conductivity and cycle performance of the anode material. Furthermore, the carbon coating layer can provide a stable physical interface, construct an expansion buffer space, suppress excessive particle expansion, reduce the deformation of the anode material, and improve safety. In addition, the carbon coating layer can control the filling of the nanoscale pore structure by adjusting the carbon coating, thereby changing the pore volume and pore area of ​​the anode material, and further regulating the specific surface area of ​​the anode material, thus improving the rate performance and high and low temperature performance of the anode material.

[0042] Please refer to Figure 1. The method for preparing the negative electrode material provided in this application embodiment specifically includes the following steps:

[0043] Step S1 involves particle size screening, cleaning, and drying of the silicon source to obtain the core.

[0044] Specifically, the silicon source material undergoes pretreatment, including selecting the silicon source, classifying it, and screening for suitable particle size. The silicon source is then ultrasonically cleaned using deionized water and alcohol, followed by centrifugation and vacuum drying. After drying, it is sieved and dispersed to obtain the core. It is understood that the cleaning process is not limited to ultrasonic cleaning; any method that can clean the raw material is acceptable. Similarly, the drying process is not limited to vacuum drying; any method that can dry the raw material is acceptable.

[0045] In some embodiments, the silicon source may include at least one of elemental silicon, silicon suboxide, silicon dioxide, and silicates. Different silicon sources have different crystal structures, morphologies, and chemical properties. By selecting a suitable silicon source, the properties of silicon-based materials can be controlled.

[0046] In some embodiments, the cleaning time can be 30 min to 360 min; the centrifugation time can be 60 min to 120 min. Within the above range, the silicon source can be cleaned, soluble salts and small molecule organic matter on the surface of the silicon source can be washed away, the impurity content can be reduced, and thus the occurrence of surface side reactions can be reduced.

[0047] In some embodiments, the drying time can be 3 hours to 48 hours, and the drying temperature can be 45°C to 80°C. Using low-temperature vacuum drying can effectively control the degree of oxidation on the material surface and regulate the reaction interface.

[0048] The screening of silicon source material particle size in this step can control the specific surface area of ​​the material, thereby controlling the subsequent reaction efficiency. It can also ensure the high consistency of the specific surface area between raw material particles, which is beneficial to the uniformity of the subsequent preparation process and effectively reduces the differences between anode material particles.

[0049] Step S2 involves doping the core with elements via plasma to obtain a doped core. The doped elements may include at least one of hydrogen, oxygen, lithium, magnesium, aluminum, nitrogen, phosphorus, sulfur, boron, fluorine, molybdenum, sodium, potassium, calcium, titanium, niobium, lanthanum, tin, selenium, and cerium.

[0050] Specifically, plasma is used for elemental doping. Solid-state doping sources can be used for metallic doping, while gas-phase doping sources of corresponding compounds can be used for non-metallic doping.

[0051] First, evacuate the reaction chamber to a pressure ≤0.1 Pa. Once the pressure meets the requirement, maintain this state for approximately 30 minutes. Then, introduce an argon-hydrogen mixture at a 1:1 ratio at a flow rate of 500 mL / min to 3000 mL / min. After introducing the argon, control the pressure to 1000–8000 Pa using a vacuum valve. Activate the plasma for plasma treatment. Begin doping the core sample. After plasma emission, immerse the dopant source (solid-state) in the plasma (adjust the immersion depth according to the melting and boiling points of different elements to ensure the dopant source maintains its solid shape) for doping reaction. The reaction time can be 6.0 h to 48.0 h, controlling the doping amount. Alternatively, a gaseous dopant source can be directly introduced into the reaction chamber at a flow rate of 300 mL / min to 1500 mL / min, with the pressure controlled at 2000 Pa to 10000 Pa for doping reaction treatment. The treatment time is 1.0 h to 24.0 h. These two phase dopant sources can also be used in combination.

[0052] After doping, hydrogen gas is introduced at a rate of 500 mL / min to 1000 mL / min, with the pressure controlled at 100 Pa to 1000 Pa, and the treatment time is 15 min to 60 min. Using hydrogen gas for treatment, through reduction, introduces hydrogen atoms into these defects or active sites, saturating surface defects and reducing the number of different active sites. This coordinates the electrolyte degradation efficiency, optimizes the core surface reaction interface, reduces excessive degradation of the core material and uneven expansion stress, and is beneficial for improving the high and low temperature storage performance, rate capability, and cycle performance of the final anode material.

[0053] After the above processing is completed, the material is discharged and then subjected to high-temperature heat treatment. The temperature of the high-temperature heat treatment is controlled at 350-950℃, and the treatment time is controlled at 2.0-24.0h. After the high-temperature heat treatment is completed, the material is broken up and sieved.

[0054] The core is doped via plasma, resulting in high uniformity, rapid reaction, and a wide temperature control range. High-energy plasma ions bombard the dopant source, causing them to be stripped from the bulk to form highly active microparticles. These microparticles then combine with the core via plasma for doping, enabling low-temperature doping with high efficiency. This effectively improves the utilization rate of the dopant element and enhances its electrochemical performance.

[0055] Step S3: Add the doped core to a deionized aqueous solution of a surfactant, and add nano-silica and milling beads for ball milling to obtain the precursor of the anode material.

[0056] Specifically, the surfactant is first dissolved in an appropriate amount of deionized water to prepare a liquid dispersion, which is then added to the core in a certain proportion. Nano-silica is then added, and finally the material is treated with a high-energy ball mill to improve its pore structure. After the ball milling is completed, it can be centrifuged to dehydrate and dried under an Ar atmosphere.

[0057] Dissolving the surfactant in an appropriate amount of deionized water to prepare a liquid dispersion ensures that the surfactant can be fully dissolved and uniformly dispersed in the deionized water. This helps to increase the contact area between the surfactant and the core, promoting the reaction. Using deionized water to dissolve the surfactant reduces the interference of impurities in the water on the reaction, ensuring the repeatability and accuracy of the production process.

[0058] In some embodiments, the surfactant may include one of the following: an alkaline solution and an organic oxidant. Using an alkaline solution or an organic oxidant as a surfactant is beneficial for promoting the interaction between the silicon source and nano-silica to form the desired nanostructure. The alkaline solution provides an alkaline environment that promotes the surface activation of the silicon source, while the organic oxidant can provide oxygen atoms to promote the oxidation reaction of the silicon source and initiate chemical reactions on its surface. These reactions help to regulate the interaction between the silicon source and nano-silica, achieving the desired control and optimization of the nanoscale pore structure.

[0059] In some embodiments, the particle size of nano-silica can be less than or equal to 80 nm. Nano-silica with the above particle size range can be subjected to mechanical force and heat energy to cause silicon particles to collide and rub during ball milling, so that micropores and mesopores with a pore size of less than or equal to 80 nm are formed on the surface of the material, and a unique pore size distribution is formed.

[0060] In some embodiments, the mass ratio of the core, surfactant, deionized water, nano-silica, and milling beads is 1:(0.1–0.5):(1–5):(0.01–0.05):(0.3–2). The mass ratio of the core, water, and surfactant can be 1:1–5:0.1–0.5; the mass ratio of the core to the milling beads can be 1:0.3–2; finally, nano-silica with a particle size of less than 80 nm is added at a mass ratio of 1:0.01–0.05 to the core. Different material ratios affect the reaction conditions and energy transfer efficiency during the ball milling process, as well as the size distribution, uniform surface structure, and electrochemical performance of the anode material precursor. Within the above-defined range, by precisely controlling the mass ratio of the core, surfactant, deionized water, nano-silica, and milling beads, the appropriate proportions of various components in the reaction process can be ensured to achieve the desired reaction pathway and product quality.

[0061] In some embodiments, the ball milling time can be 30 min to 90 min, more specifically 30 min to 60 min, and exemplaryly 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, or 90 min. Controlling the ball milling time within the above range can sufficiently achieve the desired material structure adjustment and particle size refinement.

[0062] In some embodiments, the drying temperature can be set at 60–120°C, and the drying time can be 24–72 hours. Under these conditions, moisture can be removed from the material while maintaining the structural integrity and stability of the material to the maximum extent.

[0063] Ball milling technology is used to co-mill nanoparticles with large particles, causing the nanoparticles to adsorb onto the surface of the large particle core, forming a coating on the core surface. This coating layer can act as a template agent, and subsequent treatment or removal methods, such as sintering or dissolution, allow the nanoparticles to be removed, thus forming a prototype with a porous structure, enabling the control of the pore structure. Simultaneously, the ball milling process is optimized, significantly reducing the ball-to-material ratio and minimizing excessive particle size reduction.

[0064] Step S4: Carbon coating is applied to the negative electrode material precursor to obtain the negative electrode material matrix.

[0065] Specifically, after placing the negative electrode material precursor obtained in step S3 into the deposition reaction chamber, a protective gas is introduced into the chamber to purge oxygen. When the oxygen concentration drops below 1 ppm, oxygen purging continues for 30 minutes. Then, the coating source gas is introduced, adjusting the flow rate and time according to different coating sources. After coating is completed, the introduction of the coating source gas is stopped, and the coating layer can be further heat-treated.

[0066] In some embodiments, carbon coating may include placing the anode material precursor in a reaction apparatus and introducing a coating source gas for chemical vapor deposition. Chemical vapor deposition can achieve uniformity, controllability, high efficiency, high surface activity, and good encapsulation of the carbon layer on the material surface, thereby improving the performance and application potential of the anode material.

[0067] In some embodiments, the coating source gas may include at least one of methane, ethane, acetylene, ethylene, and propane, providing carbon atoms during the coating process for depositing a carbon layer.

[0068] In some embodiments, the carbon coating temperature can be 450°C to 1000°C, and the time can be 1 hour to 48 hours. By adjusting the temperature and time, the carbon coating process can be controlled and optimized to ensure the formation and stability of the carbon layer.

[0069] In some embodiments, the flow rate of the coating source gas can be from 300 mL / min to 3000 mL / min. Controlling the flow rate of the coating source gas can adjust the supply rate of the carbon source, affecting the thickness and morphology of the carbon layer. By adjusting the flow rate, the deposition rate and uniformity of the carbon layer can be controlled, thereby optimizing the quality and performance of the carbon coating.

[0070] In some embodiments, the heat treatment temperature can be 600℃ to 1000℃, the heat treatment time can be 0 to 12 hours, and the flow rate of the protective gas remains constant during the heat treatment. The heat treatment process can further stabilize and improve the structure and properties of the carbon layer, promote the crystallization and densification of the carbon layer, and enhance the bonding force and stability between the carbon layer and the anode material.

[0071] Coating the anode material precursor offers several advantages: First, it prevents direct contact between the active silicon in the precursor and the electrolyte, inhibiting side reactions, reducing SEI overgrowth, mitigating volume expansion, and improving cycle performance, capacity, and first-efficiency. Second, it improves the conductivity of the anode material, enhancing its capacity utilization. Silicon-based anode material precursors suffer from poor conductivity; improving conductivity and other indicators ensures contact of the conductive network during cycling, reducing the formation of active materials like "dead silicon" that detach from the conductive network and improving cycle performance. Third, the coating layer provides a stable physical interface, inhibiting excessive particle expansion. It also serves as a framework for SEI growth, forming a stable SEI layer, stabilizing the solid-liquid interface, reducing expansion effects, improving cycle performance, and enhancing safety. Fourth, the coating layer allows for further control of the surface and interface nanostructure. By adjusting coating process parameters, the surface pore structure of the anode material can be further optimized, and the specific surface area can be controlled, achieving improvements in rate capability and high / low temperature performance.

[0072] Step S5: Remove the nano-silica from the negative electrode material matrix using an alkaline solution to obtain the negative electrode material. The negative electrode material has the pore structure characteristics described above, which will not be elaborated further here.

[0073] Specifically, after adding alkaline solution to the negative electrode material matrix, the temperature is raised to allow for stirring. After stirring, the material is filtered, sieved, and dried at around 100°C for approximately 24 to 48 hours. Subsequently, the material is dispersed and sieved to reduce particle agglomeration, further vacuum dried, and then encapsulated under inert gas protection to form a finished negative electrode material with a surface interface structure.

[0074] In some embodiments, the alkaline solution can be obtained by dissolving lithium hydroxide in water. A polar solvent, such as water, is a suitable reaction medium. The hydrolysis reaction dissolves lithium hydroxide in water to form a solution, which can increase the reaction rate between silicon dioxide and lithium ions.

[0075] In some embodiments, the mass ratio of the negative electrode material matrix, water, and lithium hydroxide can be 1:(1.5-5):(0.1-0.5). Reacting at this mass ratio can increase the reaction rate and accelerate the removal of nano-silica.

[0076] In some embodiments, the reaction conditions may include: a temperature of 60°C to 90°C, a time of 30 min to 360 min, and a stirring speed of 1000 rpm to 3000 rpm. Increasing the reaction temperature and controlling it between 60°C and 90°C, and allowing the reaction to proceed fully at the above-mentioned stirring speed, is beneficial for improving reaction efficiency.

[0077] Step S5 aims to remove the porous nano-silica, forming a negative electrode material with a surface porous structure. Simultaneously, the graded treatment breaks up powder agglomerates and controls the negative electrode material within an optimized particle size range. Further drying controls the moisture content of the negative electrode material, reducing its impact on the electrochemical performance.

[0078] Compared with the prior art, the method for preparing the negative electrode material provided in this application has the following beneficial effects:

[0079] 1. Using nano-silica with a particle size of 80nm or less, ball milling is performed with the core in the presence of a surfactant, causing the nano-silica to deposit on the core surface and form a porous surface prototype. Simultaneously, optimizing the ball milling process can significantly reduce the ball-to-material ratio, effectively forming a specific pore structure on the core surface. This pore structure has a first pore structure with a pore size of 2nm to 20nm and a second pore structure with a pore size of 20nm to 80nm. The distribution and volume ratio of the pore structure directly adjust the specific surface area of ​​the negative electrode material. This specific pore structure distribution regulates the wetting rate of the electrolyte in the negative electrode material, shortens the lithium ion transport path to the core, and improves the solid-liquid reaction efficiency on the negative electrode material surface, including the diffusion efficiency, ion diffusion flux, and diffusion depth of reacting ions at the interface. This is beneficial for improving the capacity, rate performance, structural stability, cycle efficiency, and storage performance and electrochemical performance under high and low temperature conditions of the negative electrode material.

[0080] 2. A carbon coating layer is formed on the surface of the anode material precursor using a carbon deposition process. This optimizes the pore structure, forms a conductive network, improves the transport rate of lithium ions in the anode material, constructs an expansion buffer space, and reduces the deformation of the anode material.

[0081] 3. This preparation method is simple, low-cost, and easy to mechanize and automate, which is conducive to the large-scale production of anode materials and has excellent commercial prospects.

[0082] Referring to Figure 2, this application embodiment also provides an electrochemical device (e.g., a lithium-ion battery). The electrochemical device 100 includes the aforementioned negative electrode material or the negative electrode material prepared by the aforementioned method. The electrochemical device 100 includes a positive electrode 10, a negative electrode 20, a separator 30, and an electrolyte 40. The separator 30 is disposed between the positive electrode 10 and the negative electrode 20, and the negative electrode 20 includes the aforementioned negative electrode material. Using the aforementioned negative electrode material to prepare the electrochemical device 100 allows for control of the wetting rate, reducing the rapid diffusion of the electrolyte within the negative electrode material and preventing side reactions with the active components. It also has a larger transport interface, shortening the lithium-ion diffusion path, thereby improving the battery's rate performance and high / low temperature performance.

[0083] The following specific examples further illustrate the aforementioned negative electrode material, its preparation method, and electrochemical device.

[0084] Example 1

[0085] Step 1: The SiO raw material is graded and screened to select raw materials with D50 in the range of 5.0μm to 6.0μm. The screened SiO raw material is ultrasonically cleaned with deionized water and alcohol for 60 min respectively. After cleaning, it is centrifuged to dehydrate and vacuum dried at 80℃. After drying for 24 h, it is broken up and sieved to obtain the kernel.

[0086] Step 2: Weigh 1000g of the core and place it in a plasma vacuum chamber. Evacuate the chamber and, when the pressure drops to 0.1Pa, introduce H2 for plasma treatment at a flow rate of 1500mL / min, controlling the pressure to 3000Pa for 30min. After plasma treatment, perform heat treatment under argon protection at 800℃ for 12.0h. After heat treatment, break up the core and sieve it to obtain the doped core.

[0087] Step 3: Weigh 1000g of the doped core. Mix the doped core with water and lithium hydroxide in a ratio of 1:3:0.15 to prepare a ball milling slurry. The mass ratio of the doped core to the milling beads is 1:1. Ball milling time is 60min. After ball milling, centrifuge to dehydrate and continue vacuum drying at 100℃ for approximately 48h to obtain the anode material precursor.

[0088] Step 4: Weigh 1000g of the negative electrode material precursor and place it in the deposition chamber. Introduce argon gas to remove oxygen at a flow rate of 4000mL / min. When the oxygen content is below 1ppm, start heating to 600℃ and introduce a mixed carbon source gas of methane and acetylene (1:1) at a flow rate of 2000mL / min. The reaction time is approximately 10.0h. After the reaction is complete, stop introducing the sample of the coating source gas, continue introducing argon gas, and heat to 900℃ for another 3h. After the treatment is complete, clean and sieve to obtain the negative electrode material matrix.

[0089] Step 5: Weigh 1000g of the negative electrode material matrix and treat it with lithium hydroxide solvent. The mass ratio of the negative electrode material matrix, water, and lithium hydroxide is 1:4:0.1. After adding the material to the alkaline solution, heat to 80℃ and treat for approximately 30 minutes, stirring at a high speed of 3000 rpm during the process. After stirring, filter and sieve, controlling the particle size D50 to be between 5.0 and 6.0. Dry at approximately 80℃ for about 24 hours. After drying, seal under inert gas protection to obtain the negative electrode material.

[0090] Example 2

[0091] Step 1: The SiO raw material is graded and screened to select raw materials with D50 in the range of 5.0μm to 6.0μm. The screened SiO raw material is ultrasonically cleaned with deionized water and alcohol for 60 min respectively. After cleaning, it is centrifuged to dehydrate and vacuum dried at 80℃. After drying for 24 h, it is broken up and sieved to obtain the kernel.

[0092] Step 2: Weigh 1000g of the core and place it in the plasma vacuum chamber. Evacuate the chamber and, when the pressure drops to 0.1Pa, introduce a hydrogen-argon mixture at a 1:1 ratio and a flow rate of 2500mL / min. Control the pressure to 4000Pa and start the plasma generator to begin the heating reaction. After the plasma photosphere stably encapsulates the material, immerse the lithium strip into the plasma photosphere, adjusting the distance to keep the material solid. The doping reaction takes approximately 24 hours. After the doping reaction is complete, remove the lithium strip and stop the Ar gas. Continue introducing H2 for plasma treatment at a flow rate of 1000mL / min, controlling the pressure to 600Pa, for 30 minutes. After plasma treatment, perform heat treatment under argon protection at 800℃ for 12.0 hours. After heat treatment, break up the core and sieve it to obtain the doped core.

[0093] Step 3: Weigh 1000g of the doped core. Mix the doped core with water and lithium hydroxide in a ratio of 1:3:0.15 to prepare a ball milling slurry. The mass ratio of the doped core to the milling beads is 1:1. Ball milling time is 60min. After ball milling, centrifuge to dehydrate and continue vacuum drying at 100℃ for approximately 48h to obtain the anode material precursor.

[0094] Step 4: Weigh 1000g of the negative electrode material precursor and place it in the deposition chamber. Introduce argon gas to remove oxygen at a flow rate of 4000mL / min. When the oxygen content is below 1ppm, start heating to 600℃ and introduce a mixed carbon source gas of methane and acetylene (1:1) at a flow rate of 2000mL / min. The reaction time is approximately 10.0h. After the reaction is complete, stop introducing the sample of the coating source gas, continue introducing argon gas, and heat to 900℃ for another 3h. After the treatment is complete, clean and sieve to obtain the negative electrode material matrix.

[0095] Step 5: Weigh 1000g of the negative electrode material matrix and treat it with lithium hydroxide solvent. The mass ratio of the negative electrode material matrix, water, and lithium hydroxide is 1:4:0.2. After adding the material to the alkaline solution, heat to 75℃ and treat for approximately 30 minutes, stirring at a high speed of 3000 rpm during the process. After stirring, filter and sieve, controlling the particle size D50 to be between 5.0 and 6.0. Dry at approximately 80℃ for about 24 hours. After drying, seal under inert gas protection to obtain the negative electrode material.

[0096] Example 3

[0097] Step 1: The SiO raw material is graded and screened to select raw materials with D50 in the range of 5.0μm to 6.0μm. The screened SiO raw material is ultrasonically cleaned with deionized water and alcohol for 60 min respectively. After cleaning, it is centrifuged to dehydrate and vacuum dried at 80℃. After drying for 24 h, it is broken up and sieved to obtain the kernel.

[0098] Step 2: Weigh 1000g of the core and place it in the plasma vacuum chamber. Evacuate the chamber and, when the pressure drops to 0.1Pa, introduce a hydrogen-argon mixture at a 1:1 ratio and a flow rate of 2500mL / min. Control the pressure to 4000Pa and start the plasma generator to begin the heating reaction. After the plasma photosphere stably encapsulates the material, immerse the magnesium ribbon in the plasma photosphere, adjusting the distance to keep the material solid. The doping reaction takes approximately 24 hours. After the doping reaction is complete, remove the magnesium ribbon and stop the Ar gas. Continue to introduce H2 for plasma treatment at a flow rate of 1000mL / min, controlling the pressure to 600Pa for 30 minutes. After plasma treatment, perform heat treatment under argon protection at 800℃ for 12.0 hours. After heat treatment, break up the core and sieve it to obtain the doped core.

[0099] Step 3: Weigh 1000g of the doped core. Mix the doped core with water and lithium hydroxide in a ratio of 1:3:0.15 to prepare a ball milling slurry. The mass ratio of the doped core to the milling beads is 1:1. Ball milling time is 60min. After ball milling, centrifuge to dehydrate and continue vacuum drying at 100℃ for approximately 48h to obtain the anode material precursor.

[0100] Step 4: Weigh 1000g of the negative electrode material precursor and place it in the deposition chamber. Introduce argon gas to remove oxygen at a flow rate of 4000mL / min. When the oxygen content is below 1ppm, start heating to 600℃ and introduce a mixed carbon source gas of methane and acetylene (1:1) at a flow rate of 2000mL / min. The reaction time is approximately 10.0h. After the reaction is complete, stop introducing the sample of the coating source gas, continue introducing argon gas, and heat to 900℃ for another 3h. After the treatment is complete, clean and sieve to obtain the negative electrode material matrix.

[0101] Step 5: Weigh 1000g of the negative electrode material matrix and treat it with lithium hydroxide solvent. The mass ratio of the negative electrode material matrix, water, and lithium hydroxide is 1:4:0.3. After adding the material to the alkaline solution, heat to 75℃ and treat for approximately 30 minutes, stirring at a high speed of 3000 rpm during the process. After stirring, filter and sieve, controlling the particle size D50 to be between 5.0 and 6.0. Dry at approximately 80℃ for about 24 hours. After drying, seal under inert gas protection to obtain the negative electrode material.

[0102] Example 4

[0103] Step 1: The SiO raw material is graded and screened to select raw materials with D50 in the range of 5.0μm to 6.0μm. The screened SiO raw material is ultrasonically cleaned with deionized water and alcohol for 60 min respectively. After cleaning, it is centrifuged to dehydrate and vacuum dried at 80℃. After drying for 24 h, it is broken up and sieved to obtain the kernel.

[0104] Step 2: Weigh 1000g of the core and place it in the plasma vacuum chamber. Evacuate the chamber and, when the pressure drops to 0.1Pa, introduce a hydrogen-argon mixture at a 1:1 ratio and a flow rate of 2500mL / min. Control the pressure to 4000Pa and start the plasma generator to begin the heating reaction. After the plasma photospheres stably encapsulate the material, introduce gaseous titanium tetrachloride at a flow rate of 800mL / min. The doping reaction takes approximately 24 hours. After the doping reaction is complete, stop introducing titanium tetrachloride and continue introducing H2 for plasma treatment at a flow rate of 1000mL / min, controlling the pressure to 6000Pa for 30 minutes. After plasma treatment, perform heat treatment under argon protection at 800℃ for 12.0 hours. After heat treatment, break up the core and sieve it to obtain the doped core.

[0105] Step 3: Weigh 1000g of the doped core. Mix the doped core with water and lithium hydroxide in a ratio of 1:3:0.15 to prepare a ball milling slurry. The mass ratio of the doped core to the milling beads is 1:1. Ball milling time is 60min. After ball milling, centrifuge to dehydrate and continue vacuum drying at 100℃ for approximately 48h to obtain the anode material precursor.

[0106] Step 4: Weigh 1000g of the negative electrode material precursor and place it in the deposition chamber. Introduce argon gas to remove oxygen at a flow rate of 4000mL / min. When the oxygen content is below 1ppm, start heating to 600℃ and introduce a mixed carbon source gas of methane and acetylene (1:1) at a flow rate of 2000mL / min. The reaction time is approximately 10.0h. After the reaction is complete, stop introducing the sample of the coating source gas, continue introducing argon gas, and heat to 900℃ for another 3h. After the treatment is complete, clean and sieve to obtain the negative electrode material matrix.

[0107] Step 5: Weigh 1000g of the negative electrode material matrix and treat it with lithium hydroxide solvent. The mass ratio of the negative electrode material matrix, water, and lithium hydroxide is 1:5:0.1. After adding the material to the alkaline solution, heat to 90℃ and treat for approximately 45 minutes, stirring at a high speed of 3000 rpm during the process. After stirring, filter and sieve, controlling the particle size D50 to be between 5.0 and 6.0. Dry at approximately 80℃ for about 24 hours. After drying, seal under inert gas protection to obtain the negative electrode material.

[0108] Example 5

[0109] Step 1: The SiO raw material is graded and screened to select raw materials with D50 in the range of 5.0μm to 6.0μm. The screened SiO raw material is ultrasonically cleaned with deionized water and alcohol for 60 min respectively. After cleaning, it is centrifuged to dehydrate and vacuum dried at 80℃. After drying for 24 h, it is broken up and sieved to obtain the kernel.

[0110] Step 2: Weigh 1000g of the core and place it in a plasma vacuum chamber. Evacuate the chamber and, when the pressure drops to 0.1Pa, introduce H2 for plasma treatment at a flow rate of 3000mL / min, controlling the pressure to 6000Pa for 30min. After plasma treatment, perform heat treatment under argon protection at 950℃ for 12.0h. After heat treatment, break up and sieve to obtain the doped core.

[0111] Step 3: Weigh 1000g of the surface-treated core. Mix the doped core with water and lithium hydroxide in a ratio of 1:1:0.15 to prepare a ball milling slurry. The mass ratio of the doped core to the milling beads is 1:3. The ball milling time is 360min. After ball milling, centrifuge to dehydrate and continue vacuum drying at 100℃ for approximately 48h to obtain the anode material precursor.

[0112] Step 4: Weigh 1000g of the negative electrode material precursor and place it in the deposition chamber. Introduce argon gas to remove oxygen at a flow rate of 4000mL / min. When the oxygen content is below 1ppm, start heating to 600℃ and introduce acetylene carbon source gas at a flow rate of 3000mL / min. The reaction time is approximately 10.0h. After the reaction is complete, stop introducing the coating source gas sample, keep introducing argon gas, and heat to 900℃ for another 3h. After the treatment is complete, clean and sieve to obtain the negative electrode material matrix.

[0113] Step 5: Weigh 1000g of the negative electrode material matrix and treat it with lithium hydroxide solvent. The mass ratio of the negative electrode material matrix, water, and lithium hydroxide is 1:4:0.1. After adding the material to the alkaline solution, heat to 80℃ and treat for approximately 30 minutes, stirring at a high speed of 3000 rpm during the process. After stirring, filter and sieve, controlling the particle size D50 to be between 5.0 and 6.0. Dry at approximately 80℃ for about 24 hours. After drying, seal under inert gas protection to obtain the negative electrode material.

[0114] Example 6

[0115] Step 1: The SiO raw material is graded and screened to select raw materials with D50 in the range of 5.0μm to 6.0μm. The screened SiO raw material is ultrasonically cleaned with deionized water and alcohol for 60 min respectively. After cleaning, it is centrifuged to dehydrate and vacuum dried at 80℃. After drying for 24 h, it is broken up and sieved to obtain the kernel.

[0116] Step 2: Weigh 1000g of the core and place it in the plasma vacuum chamber. Evacuate the chamber and, when the pressure drops to 0.1Pa, introduce a hydrogen-argon mixture at a 1:1 ratio and a flow rate of 1500mL / min. Control the pressure to 3000Pa and start the plasma generator to begin the heating reaction. After the plasma photospheres stably encapsulate the material, introduce gaseous titanium tetrachloride at a flow rate of 300mL / min for approximately 1.0h. After the doping reaction is complete, stop introducing titanium tetrachloride and continue introducing H2 for plasma treatment at a flow rate of 300mL / min, controlling the pressure to 4000Pa for 30min. After plasma treatment, perform heat treatment under argon protection at 400℃ for 3.0h. After heat treatment, break up and sieve to obtain the doped core.

[0117] Step 3: Weigh 1000g of the doped core. Mix the doped core with water and lithium hydroxide in a ratio of 1:3:0.15 to prepare a ball milling slurry. The mass ratio of the doped core to the milling beads is 1:1. Ball milling time is 60min. After ball milling, centrifuge to dehydrate and continue vacuum drying at 100℃ for approximately 48h to obtain the anode material precursor.

[0118] Step 4: Weigh 1000g of the negative electrode material precursor and place it in the deposition chamber. Introduce argon gas to remove oxygen at a flow rate of 4000mL / min. When the oxygen content is below 1ppm, start heating to 600℃ and introduce a mixed carbon source gas of methane and acetylene (1:1) at a flow rate of 2000mL / min. The reaction time is approximately 10.0h. After the reaction is complete, stop introducing the sample of the coating source gas, continue introducing argon gas, and heat to 900℃ for another 3h. After the treatment is complete, clean and sieve to obtain the negative electrode material matrix.

[0119] Step 5: Weigh 1000g of the negative electrode material matrix and treat it with lithium hydroxide solvent. The mass ratio of the negative electrode material matrix, water, and lithium hydroxide is 1:5:0.1. After adding the material to the alkaline solution, heat to 90℃ and treat for approximately 45 minutes, stirring at a high speed of 3000 rpm during the process. After stirring, filter and sieve, controlling the particle size D50 to be between 5.0 and 6.0. Dry at approximately 80℃ for about 24 hours. After drying, seal under inert gas protection to obtain the negative electrode material.

[0120] Example 7

[0121] Step 1: The SiO raw material is graded and screened to select raw materials with D50 in the range of 5.0μm to 6.0μm. The screened SiO raw material is ultrasonically cleaned with deionized water and alcohol for 60 min respectively. After cleaning, it is centrifuged to dehydrate and vacuum dried at 80℃. After drying for 24 h, it is broken up and sieved to obtain the kernel.

[0122] Step 2: Weigh 1000g of the core and place it in the plasma vacuum chamber. Evacuate the chamber and, when the pressure drops to 0.1Pa, introduce a hydrogen-argon mixture at a 1:1 ratio and a flow rate of 1500mL / min. Control the pressure to 3000Pa and start the plasma generator to begin the heating reaction. After the plasma photospheres stably encapsulate the material, introduce gaseous titanium tetrachloride at a flow rate of 600mL / min for approximately 0.5 hours. After the doping reaction is complete, stop introducing titanium tetrachloride and continue introducing H2 for plasma treatment at a flow rate of 300mL / min, controlling the pressure to 4000Pa for 30 minutes. After plasma treatment, perform heat treatment under argon protection at 400℃ for 3.0 hours. After heat treatment, break up the core and sieve it to obtain the doped core.

[0123] Step 3: Weigh 1000g of the doped core. Mix the doped core with water and lithium hydroxide in a ratio of 1:3:0.15 to prepare a ball milling slurry. The mass ratio of the doped core to the milling beads is 1:1. Ball milling time is 60min. After ball milling, centrifuge to dehydrate and continue vacuum drying at 100℃ for approximately 48h to obtain the anode material precursor.

[0124] Step 4: Weigh 1000g of the negative electrode material precursor and place it in the deposition chamber. Introduce argon gas to remove oxygen at a flow rate of 4000mL / min. When the oxygen content is below 1ppm, start heating to 600℃ and introduce a mixed carbon source gas of methane and acetylene (1:1) at a flow rate of 2000mL / min. The reaction time is approximately 10.0h. After the reaction is complete, stop introducing the sample of the coating source gas, continue introducing argon gas, and heat to 900℃ for another 3h. After the treatment is complete, clean and sieve to obtain the negative electrode material matrix.

[0125] Step 5: Weigh 1000g of the negative electrode material matrix and treat it with lithium hydroxide solvent. The mass ratio of the negative electrode material matrix, water, and lithium hydroxide is 1:5:0.1. After adding the material to the alkaline solution, heat to 90℃ and treat for approximately 45 minutes, stirring at a high speed of 3000 rpm during the process. After stirring, filter and sieve, controlling the particle size D50 to be between 5.0 and 6.0. Dry at approximately 80℃ for about 24 hours. After drying, seal under inert gas protection to obtain the negative electrode material.

[0126] Example 8

[0127] Step 1: The SiO raw material is graded and screened to select raw materials with D50 in the range of 5.0μm to 6.0μm. The screened SiO raw material is ultrasonically cleaned with deionized water and alcohol for 60 min respectively. After cleaning, it is centrifuged to dehydrate and vacuum dried at 80℃. After drying for 24 h, it is broken up and sieved to obtain the kernel.

[0128] Step 2: Weigh 1000g of the core and place it in a plasma vacuum chamber. Evacuate the chamber and, when the pressure drops to 0.1Pa, introduce H2 for plasma treatment at a flow rate of 3000mL / min, controlling the pressure to 1000Pa for 30min. After plasma treatment, perform heat treatment under argon protection at 950℃ for 12.0h. After heat treatment, break up and sieve to obtain the doped core.

[0129] Step 3: Weigh 1000g of the surface-treated core. Mix the doped core with water and lithium hydroxide in a ratio of 1:1:0.15 to prepare a ball milling slurry. The mass ratio of the doped core to the milling beads is 1:3. The ball milling time is 180min. After ball milling, centrifuge to dehydrate and continue vacuum drying at 100℃ for approximately 48h to obtain the anode material precursor.

[0130] Step 4: Weigh 1000g of the negative electrode material precursor and place it in the deposition chamber. Introduce argon gas to remove oxygen at a flow rate of 4000mL / min. When the oxygen content is below 1ppm, start heating to 600℃ and introduce acetylene carbon source gas at a flow rate of 1500mL / min. The reaction time is approximately 24.0h. After the reaction is complete, stop introducing the coating source gas sample, continue introducing argon gas, and heat to 900℃ for another 3h. After the treatment is complete, clean and sieve to obtain the negative electrode material matrix.

[0131] Step 5: Weigh 1000g of the negative electrode material matrix and treat it with lithium hydroxide solvent. The mass ratio of the negative electrode material matrix, water, and lithium hydroxide is 1:4:0.1. After adding the material to the alkaline solution, heat to 80℃ and treat for approximately 30 minutes, stirring at a high speed of 3000 rpm during the process. After stirring, filter and sieve, controlling the particle size D50 to be between 5.0 and 6.0. Dry at approximately 80℃ for about 24 hours. After drying, seal under inert gas protection to obtain the negative electrode material.

[0132] Example 9

[0133] Step 1: The SiO raw material is graded and screened to select raw materials with D50 in the range of 5.0μm to 6.0μm. The screened SiO raw material is ultrasonically cleaned with deionized water and alcohol for 60 min respectively. After cleaning, it is centrifuged to dehydrate and vacuum dried at 80℃. After drying for 24 h, it is broken up and sieved to obtain the kernel.

[0134] Step 2: Weigh 1000g of the core and place it in a plasma vacuum chamber. Evacuate the chamber and, when the pressure drops to 0.1Pa, introduce H2 for plasma treatment at a flow rate of 500mL / min, controlling the pressure to 1000Pa for 30min. After plasma treatment, perform heat treatment under argon protection at 950℃ for 12.0h. After heat treatment, break up the core and sieve it to obtain the doped core.

[0135] Step 3: Weigh 1000g of the surface-treated core. Mix the doped core with water and lithium hydroxide in a ratio of 1:1:0.15 to prepare a ball milling slurry. The mass ratio of the doped core to the milling beads is 1:3. The ball milling time is 180min. After ball milling, centrifuge to dehydrate and continue vacuum drying at 100℃ for approximately 48h to obtain the anode material precursor.

[0136] Step 4: Weigh 1000g of the negative electrode material precursor and place it in the deposition chamber. Introduce argon gas to remove oxygen at a flow rate of 4000mL / min. When the oxygen content is below 1ppm, start heating to 600℃ and introduce acetylene carbon source gas. The flow rate of the mixed coating source gas is 300mL / min. The reaction time is approximately 48.0h. After the reaction is complete, stop introducing the coating source gas sample, keep introducing argon gas, and heat to 900℃ to continue treatment for 3h. After treatment, clean and sieve to obtain the negative electrode material matrix.

[0137] Step 5: Weigh 1000g of the negative electrode material matrix and treat it with lithium hydroxide solvent. The mass ratio of the negative electrode material matrix, water, and lithium hydroxide is 1:3:0.1. After adding the material to the alkaline solution, heat to 80℃ and treat for approximately 30 minutes, stirring at a high speed of 3000 rpm during the process. After stirring, filter and sieve, controlling the particle size D50 to be between 5.0 and 6.0. Dry at approximately 80℃ for about 24 hours. After drying, seal under inert gas protection to obtain the negative electrode material.

[0138] Example 10

[0139] Step 1: The SiO raw material is graded and screened to select raw materials with D50 in the range of 5.0μm to 6.0μm. The screened SiO raw material is ultrasonically cleaned with deionized water and alcohol for 60 min respectively. After cleaning, it is centrifuged to dehydrate and vacuum dried at 80℃. After drying for 24 h, it is broken up and sieved to obtain the kernel.

[0140] Step 2: Weigh 1000g of the core and place it in a plasma vacuum chamber. Evacuate the chamber and, when the pressure drops to 0.1Pa, introduce H2 for plasma treatment at a flow rate of 500mL / min, controlling the pressure to 1000Pa for 30min. After plasma treatment, perform heat treatment under argon protection at 950℃ for 12.0h. After heat treatment, break up the core and sieve it to obtain the doped core.

[0141] Step 3: Weigh 1000g of the surface-treated core. Mix the doped core with water and lithium hydroxide in a ratio of 1:1:0.1 to prepare a ball milling slurry. The mass ratio of the doped core to the milling beads is 1:0.3. Ball mill for 30 minutes. After ball milling, centrifuge to dehydrate and continue vacuum drying at 100℃ for approximately 48 hours to obtain the anode material precursor.

[0142] Step 4: Weigh 1000g of the negative electrode material precursor and place it in the deposition chamber. Introduce argon gas to remove oxygen at a flow rate of 4000mL / min. When the oxygen content is below 1ppm, start heating to 600℃ and introduce acetylene carbon source gas. The flow rate of the mixed coating source gas is 300mL / min. The reaction time is approximately 48.0h. After the reaction is complete, stop introducing the coating source gas sample, keep introducing argon gas, and heat to 900℃ to continue treatment for 3h. After treatment, clean and sieve to obtain the negative electrode material matrix.

[0143] Step 5: Weigh 1000g of the negative electrode material matrix and treat it with lithium hydroxide solvent. The mass ratio of the negative electrode material matrix, water, and lithium hydroxide is 1:3:0.1. After adding the material to the alkaline solution, heat to 80℃ and treat for approximately 30 minutes, stirring at a high speed of 3000 rpm during the process. After stirring, filter and sieve, controlling the particle size D50 to be between 5.0 and 6.0. Dry at approximately 80℃ for about 24 hours. After drying, seal under inert gas protection to obtain the negative electrode material.

[0144] Comparative Example 1

[0145] Step 1: The SiO raw material is graded and screened to select raw materials with D50 in the range of 5.0μm to 6.0μm. The screened SiO raw material is ultrasonically cleaned with deionized water and alcohol for 60 min respectively. After cleaning, it is centrifuged to dehydrate and vacuum dried at 80℃. After drying for 24 h, it is broken up and sieved to obtain the kernel.

[0146] Step 2: Weigh 1000g of the core and place it in the deposition chamber. Introduce argon gas to remove oxygen at a flow rate of 4000mL / min. When the oxygen content is below 1ppm, start heating to 600℃ and introduce a mixed carbon source gas of methane and acetylene (1:1) at a flow rate of 2000mL / min. The reaction time is approximately 10.0h. After the reaction is complete, stop introducing the sample of the coating source gas, continue to introduce argon gas, and heat to 900℃ for another 3h. After the treatment is complete, clean and sieve to obtain the negative electrode material matrix.

[0147] Step 3: Further sieve the above-mentioned negative electrode material matrix to control the particle size D50 between 5.0 and 6.0. After grading, further vacuum dry for 24 hours at a drying temperature of 80°C. After drying, vacuum seal and store under inert gas protection to obtain the negative electrode material.

[0148] Comparative Example 2

[0149] Step 1: The SiO raw material is graded and screened to select raw materials with D50 in the range of 5.0μm to 6.0μm. The screened SiO raw material is ultrasonically cleaned with deionized water and alcohol for 60 min respectively. After cleaning, it is centrifuged to dehydrate and vacuum dried at 80℃. After drying for 24 h, it is broken up and sieved to obtain the kernel.

[0150] Step 2: Weigh 1000g of the core and place it in the plasma vacuum chamber. Evacuate the chamber and, when the pressure drops to 0.1Pa, introduce a hydrogen-argon mixture at a 1:1 ratio and a flow rate of 2500mL / min. Control the pressure to 4000Pa and start the plasma generator to begin the heating reaction. After the plasma photosphere stably encapsulates the material, immerse the lithium strip into the plasma photosphere, adjusting the distance to keep the material solid. The doping reaction takes approximately 24 hours. After the doping reaction is complete, remove the lithium strip and stop the Ar gas. Continue introducing H2 for plasma treatment at a flow rate of 1000mL / min, controlling the pressure to 600Pa, for 30 minutes. After plasma treatment, perform heat treatment under argon protection at 800℃ for 12.0 hours. After heat treatment, break up the core and sieve it to obtain the doped core.

[0151] Step 3: Weigh 1000g of the doped core and place it in the deposition chamber. Introduce argon gas to remove oxygen at a flow rate of 4000mL / min until the oxygen content is below 1ppm. Then, raise the temperature to 600℃ and introduce a mixed carbon source gas of methane and acetylene (1:1) at a flow rate of 2000mL / min. The reaction time is approximately 10.0h. After the reaction is complete, stop introducing the sample of the coating source gas, continue to introduce argon gas, raise the temperature to 900℃ and continue the treatment for 3h. After the treatment is completed, clean and sieve to obtain the negative electrode material matrix.

[0152] Step 4: Further sieve the above-mentioned negative electrode material matrix to control the particle size D50 between 5.0 and 6.0. After grading, further vacuum dry for 24 hours at a drying temperature of 80°C. After drying, vacuum seal and store under inert gas protection to obtain the negative electrode material.

[0153] Comparative Example 3

[0154] Step 1: The SiO raw material is graded and screened to select raw materials with D50 in the range of 5.0μm to 6.0μm. The screened SiO raw material is ultrasonically cleaned with deionized water and alcohol for 60 min respectively. After cleaning, it is centrifuged to dehydrate and vacuum dried at 80℃. After drying for 24 h, it is broken up and sieved to obtain the kernel.

[0155] Step 2: Weigh 1000g of the core and place it in the plasma vacuum chamber. Evacuate the chamber and, when the pressure drops to 0.1Pa, introduce a 1:1 H2 / Ar mixture for plasma treatment at a flow rate of 3000mL / min, controlling the pressure to 8000Pa for 300min. After plasma treatment, perform heat treatment under argon protection at 950℃ for 12.0h. After heat treatment, break up and sieve to obtain the doped core.

[0156] Step 3: Weigh 1000g of the surface-treated core. Mix the doped core with water and lithium hydroxide in a ratio of 1:1:2 to prepare a ball milling slurry. The mass ratio of the doped core to the milling beads is 1:1. The ball milling time is 360min. After ball milling, centrifuge to dehydrate and continue vacuum drying at 100℃ for approximately 48h to obtain the anode material precursor.

[0157] Step 4: Weigh 1000g of the core and place it in the deposition chamber. Introduce argon gas to remove oxygen at a flow rate of 4000mL / min. When the oxygen content is below 1ppm, start heating to 800℃ and introduce a mixed carbon source gas of methane and acetylene (1:1) at a flow rate of 2000mL / min. The reaction time is approximately 10.0h. After the reaction is complete, stop introducing the sample of the coating source gas, continue to introduce argon gas, and heat to 900℃ for another 3h. After the treatment is complete, clean and sieve to obtain the negative electrode material matrix.

[0158] Step 3: Further sieve the above-mentioned negative electrode material matrix to control the particle size D50 between 5.0 and 6.0. After grading, further vacuum dry for 24 hours at a drying temperature of 80°C. After drying, vacuum seal and store under inert gas protection to obtain the negative electrode material.

[0159] Comparative Example 4

[0160] Step 1: The SiO raw material is graded and screened to select raw materials with D50 in the range of 5.0μm to 6.0μm. The screened SiO raw material is ultrasonically cleaned with deionized water and alcohol for 60 min respectively. After cleaning, it is centrifuged to dehydrate and vacuum dried at 80℃. After drying for 24 h, it is broken up and sieved to obtain the kernel.

[0161] Step 2: Weigh 1000g of the core and place it in the deposition chamber. Introduce argon gas to remove oxygen at a flow rate of 4000mL / min. When the oxygen content is below 1ppm, start heating to 600℃ and introduce a mixed carbon source gas of methane and acetylene (1:1) at a flow rate of 2000mL / min. The reaction time is approximately 10.0h. After the reaction is complete, stop introducing the sample of the coating source gas, continue to introduce argon gas, and heat to 900℃ for another 3h. After the treatment is complete, clean and sieve to obtain the negative electrode material matrix.

[0162] Step 3: Further sieve the above-mentioned negative electrode material matrix to control the particle size D50 between 5.0 and 6.0. After grading, further vacuum dry for 24 hours at a drying temperature of 80°C. After drying, vacuum seal and store under inert gas protection to obtain the negative electrode material.

[0163] The negative electrode materials obtained in Examples 1-10 and Comparative Examples 1-4 were subjected to the following tests.

[0164] 1. Material performance tests were conducted on Examples 1-10 and Comparative Examples 1-4. The material performance test results for Examples 1-5 are shown in Table 1, the material performance test results for Examples 6-10 are shown in Table 2, and the material performance test results for Comparative Examples 1-4 are shown in Table 3.

[0165] (1) Particle size test: D50 was measured using a Matersizer 3000 according to the method of GB / T 19077-2016, and it exhibits a symmetrical distribution similar to a normal distribution. In its volume reference distribution, the cumulative 50% diameter is D50.

[0166] Test complete.

[0167] (2) Carbon content test: According to the technical method of GB / T 20123-2006, the sample is burned in a high-temperature furnace with oxygen to generate and release CO2 gas. This method is used to separate C element from metal elements and their compounds. The C content in the sample is calculated by measuring the CO2 content.

[0168] (3) Moisture content test: The moisture content in the negative electrode material was determined by Karl Fischer coulometric analysis according to the test method specified in GB / T 24533-2019. The moisture in the sample was volatilized into water vapor at high temperature and entered the electrolytic cell to react with Karl Fischer reagent. The water content was determined by the change in potential.

[0169] (4) Pore volume and specific surface area test: The BET method is used to test the pore volume in the pore size range of 2nm to 20nm, the pore volume in the pore size range of 20nm to 80nm, and the specific surface area of ​​the negative electrode material is S.

[0170] (5) Doping element content test: According to GB / T 24533-2019, the ICP method is used for testing. Specifically, the graphite digester is heated and digested in an open atmospheric pressure environment, and the content of each element is tested by ICP-OES.

[0171] (6) Oil absorption value test: The test was conducted according to GB / T 3780.2-2017 "Carbon Black Part 2: Determination of Oil Absorption Value". A certain mass of powder sample was placed in the mixing chamber, and linseed oil was dripped onto the sample at a constant speed while being stirred simultaneously by two motor-driven rotary blades. As the amount of linseed oil absorbed by the sample increased, the mixture changed from a free-flowing state to a semi-plastic agglomerate. During this process, the viscosity of the mixture gradually increased and reached a peak. The measurement endpoint was the amount of linseed oil added when the torque generated by the change in viscosity characteristics reached the set value or a constant percentage of the maximum torque obtained from the torque curve. The oil absorption value (mL / 100g) of the sample was calculated. The equipment was ASAHISOUKEN, Japan, model ASAHI S-500.

[0172] (7) Isothermal adsorption-desorption curve: The determination was performed according to GB / T 19587-2017 "Determination of Specific Surface Area of ​​Solid Substances by Gas Adsorption-BET Method". A certain amount of sample was weighed and placed into a special bubble tube for specific surface area. The sample was purged with nitrogen at 300℃ for a certain period of time in the degassing station. After degassing was completed, the sample was cooled to room temperature. The actual mass of the sample was weighed, and the special bubble tube containing the sample was installed into the specific surface area and pore size analyzer. After inputting the sample mass, the specific surface area and pore size of the sample were determined. Below 0.01, quantitative gas injection was used at 20 mL / g; above 0.01, fixed-point gas injection was used at intervals of 0.01–0.10, 0.01; 0.01–0.20, 0.02; 0.20–1.0, 0.05; degassing was performed from 1.00–0.15, 0.05. The equipment was a McMurray Tech ASAP2460 from the United States. Obtain the N2 isotherm linear plot from the test report, and calculate the hysteresis area by hyperbolic integration of adsorption and desorption.

[0173] The performance of the anode materials prepared in the examples and comparative examples was tested, and the results of the performance tests are shown in Table 2:

[0174] Table 1

[0175] Table 2

[0176] Table 3

[0177] In Examples 1-10, the BET method was used to test the negative electrode material. Pore distribution was observed in both the 2nm-20nm and 20nm-80nm ranges. The pore volume in the 2nm-20nm range was V1, and the pore volume in the 20nm-80nm range was V2. The specific surface area of ​​the negative electrode material was S, and both satisfied the following: 0.1μm ≥ (V1 + V2) / S ≥ 0.01μm, 0.8 ≥ V1 / V2 ≥ 0.01, and 10.0m. 2 / g≥S≥0.1m 2 / g. However, the (V1+V2) / S and V1 / V2 ratios of Comparative Examples 1-4 were not fully satisfied, indicating that the pore structure distribution in Comparative Examples 1-4 was unreasonable. Satisfying the above distribution and specific surface area contribution in the pore volume distribution of the anode material can effectively regulate the interfacial reaction; a reasonable combination of the first and second pore structures in the anode material can effectively adjust the wetting rate of the electrolyte and slurry, thereby improving the stability of the anode material and the lithium-ion transport efficiency.

[0178] 2. Lithium-ion batteries were prepared using the negative electrode materials of Examples 1-10 and Comparative Examples 1-4, and the electrochemical performance of the lithium-ion batteries was tested. The results of the electrochemical performance tests are shown in Table 4.

[0179] The specific capacity and initial charge-discharge coulombic efficiency of the negative electrode material were determined according to the equipment and methods outlined in BTRTC / ZY / 01-020 "Button Battery Method Operation Manual" issued by BTR. The batteries were assembled into button cells. The counter electrode used a lithium metal sheet, and the separator was a PP-PE-PP composite membrane with a diameter of 19.2 mm. The electrolyte composition ratio was ethylene glycol carbonate (EC): propylene glycol carbonate (EMC): dimethyl carbonate (DMC) = 1:1:1, and the lithium salt (LiPF6) concentration was 1.05 mol / L.

[0180] (1) Material specific capacity test: Using a button cell battery charging and discharging device, charge at 0.1C constant current to 10mV, then switch to 0.02C constant current charging to 5mV, and discharge at 0.1C constant current to 1.5V cutoff.

[0181] (2) 50-cycle half-cell test: Using a button cell charge / discharge device, in week 1, the cell was discharged at 0.1C to 0.01V, then discharged at 0.01C with decreasing rates to 0.01V, then discharged at 0.01C to 0.005V, and charged at 0.1C to 1.5V; in week 2, the cell was discharged at 0.2C to 0.01V, then discharged at 0.02C with decreasing rates to 0.01V, then discharged at 0.02C to 0.005V, and charged at 0.2C to 1.5V; in week 3, the cell was discharged at 0.5C to 0.01V. Discharge at 0.01V, 0.05C, and 0.05C to 0.005V, then charge at 0.5C to 1.5V; from week 4 to week 50, discharge at 1C to 0.01V, discharge at 0.1C, and 0.1C to 0.005V, then charge at 1C to 1.5V; in week 51, discharge at 0.1C to 0.01V, discharge at 0.01C, and 0.01C to 0.005V.

[0182] (3) Full battery performance test: The negative electrode material is mixed with graphite to achieve a standard capacity of 450mAh / g. The positive electrode material can be ternary materials such as NCM and NCA, or lithium iron phosphate. The lithium battery is assembled using coin cells. The electrolyte can be a silicon-based electrolyte (EC / EMC / DMC FEC 10%). The capacity retention rate is tested at high temperature (60℃) and low temperature (-25℃). Specifically, charge and discharge tests are conducted at a current density of 0.2C (2.75~4.2V); rate performance tests are conducted at three different current densities: 1C / 0.5C, 2C / 0.5C, and 3C / 0.5C.

[0183] Table 4

[0184] The batteries prepared using the negative electrode materials of Examples 1-10 of this application show significant improvements in specific capacity and initial coulombic efficiency compared to Comparative Examples 1-4 with similar cores, while maintaining good cycle performance and high / low temperature performance. This is because the negative electrode materials in Examples 1-10 possess suitable nanoscale pore structures and uniform carbon coating layers, effectively reducing surface side reactions in battery preparation, decreasing electrolyte consumption, and reducing the loss of active silicon and active lithium, thus improving the battery's specific capacity and initial coulombic efficiency. Secondly, during the preparation of the negative electrode materials, the alkaline treatment of the negative electrode material matrix dissolves some oxides on the surface of the negative electrode material, reducing the content of active oxygen and inactive components, reducing the initial coulombic efficiency loss, and achieving improved battery electrochemical performance.

[0185] Among them, the capacity and first-efficiency of the batteries prepared using the anode materials of Example 1 (compared with undoped anode materials such as Examples 5, 8-10, Comparative Examples 1, 3 and 4) and Example 2 (compared with Comparative Example 2, which uses doped anode materials of the same type) were significantly improved. This is because the doping elements of the anode materials in Examples 1 and 2 improved the electrochemical performance of the anode materials, including increasing the lithium-ion storage capacity, increasing the conductivity, improving the structural stability and reducing the electrode polarization, thereby improving the battery capacity and first-efficiency performance.

[0186] Furthermore, the porous structure of the negative electrode material optimizes the ion diffusion environment at the reaction interface. In the battery prepared using the negative electrode material of Comparative Example 2, gas generation occurs after 24 hours of storage during processing. This is because during the aqueous (polar solvent) slurry preparation process of the negative electrode material in Comparative Example 2, the polar solvent rapidly infiltrates and penetrates the interior of the negative electrode material. The active material and the polar solvent rapidly undergo a redox reaction, disrupting the slurry stability and causing gas generation. Simultaneously, the redox reaction alters the acid-base environment of the slurry, impairing the solubility of the dispersant and leading to agglomeration of the negative electrode material. In contrast, the battery prepared using the negative electrode material of Example 2 exhibits good slurry stability, indicating that optimizing the pore structure can effectively improve the degree of interfacial reaction, suppress side reactions, and thus enhance the stability of the negative electrode material.

[0187] Finally, the high and low temperature capacity performance and rate performance test results show that the batteries prepared with the negative electrode materials in Examples 1-10 have significantly improved high and low temperature performance and rate performance. For Comparative Example 2, which has a smaller (V1+V2) / S value, i.e., a lower pore structure depth, the electrolyte wetting rate is too fast, and the electrolyte quickly enters the interior of the negative electrode material, causing excessive oxidation of the active material and excessive gas production. Therefore, its rate performance and high and low temperature performance are weaker than those of the batteries prepared with the negative electrode materials in Examples 1-10 of this application. For Comparative Example 1, which has a larger (V1+V2) / S value, i.e., a larger pore structure depth, the core diffusion path is too long, the electrolyte wetting rate decreases, resulting in low lithium-ion transfer efficiency, which also leads to poor battery rate and low temperature performance. In Comparative Example 3, the excessively large specific surface area S of the negative electrode material leads to increased battery impedance and significantly decreased thermal stability. In Comparative Example 4, the excessively large V1 / V2 ratio of the negative electrode material, i.e., the excessively high proportion of the first pore structure, leads to a reduced lithium-ion diffusion rate, affecting the performance of the prepared battery. The negative electrode materials in Examples 1-10 have a reasonable pore structure and specific surface area, thus having a suitable pore depth value, thereby improving the battery rate and high and low temperature performance.

[0188] Therefore, it can be seen that the pore structure of the negative electrode material in the embodiments of this application can control the surface reaction efficiency of the negative electrode material, affect the interface reaction process and reaction details, including the appropriate diffusion efficiency of reaction ions at the interface, ion diffusion flux and diffusion depth, thereby improving the rate performance and high and low temperature performance of the negative electrode material.

[0189] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of this application, and this application is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this application, and these modifications and improvements are also considered to be within the scope of protection of this application.

Claims

1. A negative electrode material, characterized in that, The anode material includes silicon-containing materials and carbon-containing materials, and the anode material has a porous structure with the following distribution characteristics: The negative electrode material was tested using the BET method. The results showed that the negative electrode material has a first pore structure with a pore size of 2nm to 20nm and a second pore structure with a pore size of 20nm to 80nm. The pore volume of the first pore structure is V1, and the pore volume of the second pore structure is V2. The specific surface area of ​​the negative electrode material is S, where 0.1μm ≥ (V1 + V2) / S ≥ 0.01μm, 0.8 ≥ V1 / V2 ≥ 0.01, and 10.0m... 2 / g≥S≥0.1m 2 / g.

2. The negative electrode material according to claim 1, characterized in that, The negative electrode material satisfies at least one of the following characteristics: (1) (V1+V2) / S is 0.01μm, 0.02μm, 0.03μm, 0.04μm, 0.05μm, 0.06μm, 0.07μm, 0.08μm, 0.09μm, 0.1μm or within the range of any two of the above values; (2) V1 / V2 is 0.01, 0.03, 0.05, 0.08, 0.1, 0.2, 0.3, 0.5, 0.6, 0.7, 0.8 or within the range of any two of the above values; (3) S is 0.1m 2 / g, 0.5m 2 / g、1m 2 / g、2m 2 / g、3m 2 / g、4m 2 / g、5m 2 / g、6m 2 / g、7m 2 / g、8m 2 / g、9m 2 / g, 10m 2 / g or within the range of any two of the above values.

3. The negative electrode material according to claim 1, characterized in that, The pore volumes of the first pore structure and the second pore structure in the pore structure satisfy at least one of the following conditions: (1) The pore volume V1 satisfies 0.5 cm³. 3 / g≥V1≥0.001cm 3 / g; (2) The pore volume V2 satisfies 5.0 cm². 3 / g≥V2≥0.01cm 3 / g.

4. The negative electrode material according to any one of claims 1 to 3, characterized in that, The negative electrode material satisfies at least one of the following characteristics: (1) The silicon-containing material includes at least one of elemental silicon, silicon oxide and silicate; (2) The silicon-containing material includes silicon oxide, and the general chemical formula of the silicon oxide is SiO. x , 0 < x ≤ 2.

5. The negative electrode material according to any one of claims 1 to 3, characterized in that, The negative electrode material satisfies at least one of the following characteristics: (1) The isothermal adsorption hysteresis integral area of ​​the negative electrode material is 1.0 × 10⁻⁶. -4 ~5.0×10 -2 ; (2) The pore size range of the negative electrode material is 0.5nm to 300nm.

6. The negative electrode material according to any one of claims 1 to 3, characterized in that, The oil absorption value of the negative electrode material is 25mL / 100g to 85mL / 100g.

7. The negative electrode material according to any one of claims 1 to 3, characterized in that, The negative electrode material satisfies at least one of the following characteristics: (1) The volume distribution particle size D50 of the negative electrode material ranges from 2.0 μm to 15.0 μm; (2) The pH value of the negative electrode material is 7.5 to 12.

0.

8. The negative electrode material according to any one of claims 1 to 3, characterized in that, The negative electrode material satisfies at least one of the following characteristics: (1) The total mass of the silicon-containing material and the carbon-containing material accounts for 40% to 97.5% of the total mass of the negative electrode material; (2) The mass of the carbon-containing material accounts for 1.5% to 45.5% of the total mass of the negative electrode material.

9. The negative electrode material according to any one of claims 1 to 3, characterized in that, The negative electrode material also includes doping elements, which include at least one of hydrogen, oxygen, lithium, magnesium, aluminum, nitrogen, phosphorus, sulfur, boron, fluorine, molybdenum, sodium, potassium, calcium, titanium, niobium, lanthanum, tin, selenium, and cerium.

10. The negative electrode material according to claim 9, characterized in that, The dopant element has a content of 25 ppm to 120,000 ppm in the negative electrode material.

11. The negative electrode material according to claim 1, characterized in that, The silicon-containing material forms the core, and the carbon-containing material forms a carbon coating layer on the surface of the core.

12. An electrochemical device, characterized in that, The electrochemical device includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the negative electrode includes a negative electrode active material, and the negative electrode active material includes the negative electrode material as described in any one of claims 1 to 11.

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