A secondary battery negative electrode material, a preparation method and application thereof

Abstract

This invention discloses a secondary battery anode material, its preparation method, and its application. The anode material includes a core and one or more of a main silicon-phosphorus-carbon layer, a main silicon-phosphorus layer, and a main phosphorus-carbon layer, wrapped around the surface of the core. The anode material of this invention, through structural and compositional design, can fully utilize the theoretical capacity advantage of silicon-based materials while overcoming the fatal defect of low cycle life caused by excessive expansion rate in silicon-based materials.

Description

Technical Field

[0001] This invention belongs to the field of secondary battery technology, specifically relating to a negative electrode material, its manufacturing method, and its application. Background Technology

[0002] Currently, carbon anodes are widely used in secondary batteries. Carbon anodes are the most commercially mature anodes, possessing excellent conductivity and good cycle stability, but their specific capacity is relatively low. Silicon, with its high theoretical capacity, abundant resources, and low price, holds the promise of replacing current carbon anodes for large-scale commercialization. However, before commercialization, the problem of large volume changes (~300%) of silicon materials during charge and discharge must be overcome. To address the issues surrounding silicon anodes, researchers have explored several directions: first, nanostructuring silicon-based materials to mitigate the impact of volume expansion on battery performance; second, combining silicon with other materials. However, the effects of these modification approaches have been limited, and the cycle stability of the resulting silicon-based anodes still needs improvement. Summary of the Invention

[0003] The present invention aims to solve the key problems existing in the prior art. To this end, the present invention proposes an anode material that, through structural and compositional design, can significantly increase the cycle life of silicon-based or silicon-carbon anodes while ensuring high capacity.

[0004] The first feature of this invention is that it directly mixes the core with a solid phosphorus source and reacts at 560-660 degrees Celsius, without the need for a special equipment to convert the phosphorus source into a gaseous state, making it simple and efficient.

[0005] The second feature of this invention is that it combines the silicon-phosphorus layer and the phosphorus-carbon layer together, that is, the effect of the double-layer composite layer is significantly higher than that of a single silicon-phosphorus layer or phosphorus-carbon layer.

[0006] This invention selects an optimal temperature at which silicon and carbon source gases can be decomposed to generate atomic hydrogen.

[0007] At this temperature, hydrogen reacts with the phosphorus source to generate phosphorus atoms, which then permeate and dope with silicon and carbon.

[0008] At this temperature, other impurities evaporate and are eliminated.

[0009] The advantage of this invention is that the conductivity of the material is enhanced by phosphorus doping and utilizing the semiconductor effect.

[0010] Simultaneously, due to doping, the electrostatic field of the material is distorted. This effect comes from the doping of phosphorus in silicon, but more importantly from the doping of phosphorus in the carbon layer. The combined effect of the silicon-phosphorus layer and the phosphorus-carbon layer is significantly greater than that of the single silicon-phosphorus layer. According to the latest news, the silicon-carbon anode produced according to the principle of this patent has a cycle capacity of more than 2300 mAh / g and a cycle count of more than 1500 times, making the silicon-carbon anode 100% able to replace the graphite anode for the first time and enter industrial application. The invention of this patent has started the process of the transformation of lithium battery anodes from graphite anodes to silicon-carbon anodes. Since the publication of this patent on August 8, 2025, at the end of 2025 and from January to March 2026, China and other countries have launched a large-scale investment and construction boom in CVD silicon-carbon anodes.

[0011] A negative electrode material, characterized in that it comprises a core and at least one of a main silicon-phosphorus carbon layer A, a main silicon-phosphorus layer B, and a main phosphorus carbon layer C wrapped around the surface of the core.

[0012] The core can be made of any material of suitable particle size and material.

[0013] The core can be made of porous carbon, carbon fiber, pure silicon particles, etc., with appropriate particle size and specific surface area.

[0014] The main silicon-phosphorus carbon layer A, main silicon-phosphorus layer B, and main phosphorus-carbon layer C can be prepared by a method including the following steps.

[0015] The S1 main silicon-phosphorus-carbon layer A is produced in any suitable equipment (such as a fluidized bed, rotary kiln, or tunnel kiln) by mixing a material that can act as a core with a phosphorus source X, and introducing a scientifically calculated flow rate of silicon source gas, carbon source gas, and inert gas. The process involves heating, holding, and cooling. Due to process requirements or imprecise calculations, there may be transition layers and pure carbon coating layers of varying thicknesses on the inner and outer surfaces of this layer. The desired composition and structure can be achieved by selecting phosphorus source X of appropriate particle size and weight, and by repeatedly adding phosphorus source X.

[0016] The S2 main silicon-phosphorus layer B is produced in any suitable equipment (such as a fluidized bed, rotary kiln, or tunnel kiln) by mixing a material that can act as a core with a phosphorus source X, introducing a scientifically calculated flow rate of silicon source gas and an inert gas, and then proceeding with a heating, holding, and cooling process. Due to process requirements or imprecise calculations, a transition layer of varying thickness may exist between the inner and outer surfaces of this layer. The desired composition and structure can be achieved by selecting an appropriate particle size and weight of phosphorus source X, and by repeatedly adding phosphorus source X.

[0017] The S3 main phosphorus-carbon layer C is produced in any suitable equipment (such as a fluidized bed, rotary kiln, or tunnel kiln) by mixing a material of suitable particle size that can serve as the core with a phosphorus source X, introducing a scientifically calculated flow rate of carbon source gas and an inert gas, and then proceeding with a heating, holding, and cooling process. Due to process requirements or imprecise calculations, there may be transition layers and pure carbon coating layers of different thicknesses on the inner and outer surfaces of this layer. The desired composition and structure can be achieved by selecting an appropriate particle size and weight of phosphorus source X, and by repeatedly adding phosphorus source X.

[0018] The negative electrode material is characterized in that the phosphorus source X comprises one or more of sodium hexametaphosphate, potassium hexametaphosphate, calcium hexametaphosphate, sodium tripolyphosphate, potassium tripolyphosphate, calcium tripolyphosphate, sodium pyrophosphate, potassium pyrophosphate, and calcium pyrophosphate.

[0019] The negative electrode material is characterized in that the silicon source gas includes one or more of silane, methane, and ethyl silane.

[0020] The negative electrode material is characterized in that the carbon source gas includes one or more of acetylene, ethylene, methane, and ethane.

[0021] The negative electrode material is characterized in that the heat preservation reaction temperature of S1, S2, and S3 is 560-660 degrees.

[0022] The aforementioned negative electrode material is characterized in that the main silicon-phosphorus-carbon layer A has the following weight composition: silicon 0.001-99.998 parts, phosphorus 0.001-60 parts, and carbon 0.001-99.998 parts. Particularly preferred is a main silicon-phosphorus-carbon layer A weight composition that can be determined by calculation or measurement methods: silicon 30-100 parts, phosphorus 0.01-50 parts, and carbon 1-60 parts.

[0023] The negative electrode material is characterized in that the main silicon-phosphorus layer B has the following weight composition: 1-100 parts silicon and 0.01-50 parts phosphorus.

[0024] The negative electrode material is characterized in that the main phosphorus-carbon layer C has a weight composition of 0.01-60 parts phosphorus and 1-100 parts carbon.

[0025] Inert gases refer to nitrogen and argon.

[0026] (a) The negative electrode structure is: kernel + main body A layer or kernel + main body A layer + main body C layer.

[0027] Select a material with a suitable particle size and weight (e.g., 1000 grams) as the core, and its composition is at least but not limited to one of the following materials: porous carbon, carbon fiber, graphite.

[0028] The material is mixed with a phosphorus source X of suitable particle size and appropriate weight (e.g., 60 grams), and placed in a fluidized bed, rotary kiln, or tunnel kiln. The temperature is increased to 560-660 degrees Celsius at a rate of 5-10 degrees Celsius per minute, while simultaneously introducing an inert gas at a certain flow rate (e.g., 0.5-15 L / min). Within the temperature range of 560-660 degrees Celsius, an inert gas is introduced at a certain flow rate (e.g., 0.5-30 L / min); silane gas is introduced at a certain flow rate (e.g., 1-20 L / min); and acetylene gas is introduced at a certain flow rate (e.g., 0.5-20 L / min). The reaction time is 100-800 minutes.

[0029] Then, close the silane valve to stop the silane supply, and continue to supply acetylene for another 0-400 minutes to react.

[0030] Depending on the amount of X, the flow rate of silane and acetylene, and the duration of the inlet flow, negative electrode materials with different layered structures, such as core + main body A layer or core + main body A layer + main body C layer, can be produced.

[0031] (ii) The negative electrode structure is: kernel + main body B layer or kernel + main body B layer + main body C layer.

[0032] Select a material of suitable particle size and weight (e.g., 1000 grams) as the core, whose composition is at least but not limited to one of the following materials: porous carbon, carbon fiber, graphite.

[0033] Mix the material with a phosphorus source X of suitable particle size and appropriate weight (e.g., 60 grams), and place it in a fluidized bed, rotary kiln, or tunnel kiln. Inert gas is introduced at a certain flow rate (e.g., 0.5-20 L / min). The temperature is increased to 560-660 degrees Celsius at a rate of 2-20 degrees Celsius per minute. Within the temperature range of 560-660 degrees Celsius, inert gas is introduced at a certain flow rate (e.g., 0.5-20 L / min), and silane gas is introduced at a certain flow rate (e.g., 1-20 L / min). The reaction time is 100-400 minutes.

[0034] Then, stop the silane supply, continue heating to 560-660 degrees Celsius, open the acetylene valve, and introduce acetylene at a certain flow rate (e.g., 0.5-20 liters / minute) for a reaction time of 0-400 minutes.

[0035] Depending on the amount of X, the flow rate of silane and acetylene, and the duration of the inlet flow, negative electrode materials with different layered structures, such as core + main body B layer or core + main body B layer + main body C layer, can be produced.

[0036] (III) The negative electrode structure is: the method of making the kernel + the main body C layer.

[0037] Select a material with a suitable particle size and weight (e.g., 1000 grams) as the core, and its composition is at least but not limited to one of the following materials: porous carbon, carbon fiber, graphite.

[0038] Mix the above materials with a phosphorus source X of suitable particle size and appropriate weight (e.g., 60 grams), and place the mixture in a fluidized bed, rotary kiln, or tunnel kiln. Inert gas is introduced at a certain flow rate (e.g., 0.5-20 L / min). The temperature is increased to 560-660 degrees Celsius at a rate of 2-20 degrees Celsius per minute. Within the temperature range of 560-660 degrees Celsius, inert gas is introduced at a certain flow rate (e.g., 0.5-20 L / min), and simultaneously, acetylene gas is introduced at a certain flow rate (e.g., 0.5-20 L / min). The reaction time is 100-400 minutes.

[0039] Depending on the amount of X, the flow rate of acetylene, and the duration of its introduction, a negative electrode material with a core + main body C-layer structure can be produced.

[0040] Example 1: Kernel + Main B Layer + Main C Layer.

[0041] Select 1000 grams of porous carbon of suitable particle size and mix it with 100 grams of phosphorus source X of suitable particle size. Place the mixture in a rotary kiln and heat it to 620 degrees Celsius at a rate of 10 degrees Celsius per minute. At 620 degrees Celsius, introduce 3 liters of silane per minute for 200 minutes.

[0042] Stop the silane flow and instead introduce acetylene at a flow rate of 1.0 liter per minute for 300 minutes, then allow it to cool naturally.

[0043] Nitrogen gas is introduced during the heating, holding, and cooling processes at a flow rate of 1 liter per minute.

[0044] The specific surface area of ​​porous carbon can be 100-1900 m2 / g.

[0045] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

[0046] Example 1 Cyclic capacity (mAh / g) Number of cycles 1680 500.

Claims

1. A negative electrode material, characterized in that, The material comprises a core and one or more of the following layers encapsulating the core surface: a main silicon-phosphorus-carbon layer A, a main silicon-phosphorus layer B, and a main phosphorus-carbon layer C. The main silicon-phosphorus-carbon layer A, B, and C can be prepared by a method including the following steps: S1. Main silicon-phosphorus-carbon layer A is prepared in any suitable equipment, such as a fluidized bed, rotary kiln, or tunnel kiln, by mixing a material that can serve as the core with a phosphorus source X, introducing a scientifically calculated flow rate of silicon source gas, carbon source gas, and inert gas, and then proceeding with a heating, holding, and cooling process. Due to process requirements or insufficient calculation precision, there may be transition layers and pure carbon coating layers of different thicknesses on the inner and outer surfaces of this layer. The desired composition and structure can be achieved by selecting phosphorus source X with appropriate particle size and weight, and by repeatedly adding phosphorus source X several times. S2, the main silicon-phosphorus layer B, is produced in any suitable equipment, such as a fluidized bed, rotary kiln, or tunnel kiln, by mixing a material that can act as a core with phosphorus source X, introducing a scientifically calculated flow rate of silicon source gas and inert gas, and then proceeding through a heating, holding, and cooling process. Due to process requirements or imprecise calculations, there may be transition layers of different thicknesses on the inner and outer surfaces of this layer. The desired composition and structure can be achieved by selecting phosphorus source X of appropriate particle size and weight, and by repeatedly adding phosphorus source X. S3, the main phosphorus-carbon layer C, is produced in any suitable equipment, such as a fluidized bed, rotary kiln, or tunnel kiln, by mixing a material of suitable particle size that can act as a core with phosphorus source X, introducing a scientifically calculated flow rate of carbon source gas and inert gas, and then proceeding through a heating, holding, and cooling process. Due to process requirements or imprecise calculations, there may be transition layers and pure carbon coating layers of different thicknesses on the inner and outer surfaces of this layer. By selecting phosphorus source X with appropriate particle size and weight, and by repeatedly adding phosphorus source X, a composition and structure that conforms to the design can be formed. The S1 / S2 / S3 heat preservation reaction temperature is 560-660 degrees. The silicon source gas includes one or more of silane, methane, and ethyl silane. The carbon source gas includes one or more of acetylene, ethylene, methane, and ethane. Inert gases include nitrogen, argon, or one or more of them.

2. The negative electrode material according to claim 1, characterized in that, Phosphorus source X includes one or more of sodium hexametaphosphate, potassium hexametaphosphate, calcium hexametaphosphate, sodium tripolyphosphate, potassium tripolyphosphate, calcium tripolyphosphate, sodium pyrophosphate, potassium pyrophosphate, and calcium pyrophosphate.

3. The negative electrode material according to claim 1, characterized in that, The weight composition of the main silicon-phosphorus-carbon layer A can be determined by calculation or measurement methods, with silicon ranging from 0.001 to 99.998 parts, phosphorus from 0.001 to 60 parts, and carbon from 0.001 to 99.998 parts.

4. The negative electrode material according to claim 1, characterized in that, The preferred composition can be determined by calculation or measurement methods, which shows that the weight composition of the main silicon-phosphorus-carbon layer A is 30-100 parts silicon, 0.01-50 parts phosphorus, and 1-60 parts carbon.

5. The negative electrode material according to claim 1, characterized in that, The weight composition of the main silicon-phosphorus layer B can be determined by calculation or measurement methods, with silicon at 1-100 parts and phosphorus at 0.01-50 parts.

6. The negative electrode material according to claim 1, characterized in that, The weight composition of the main phosphorus-carbon layer C can be determined by calculation or measurement methods, with phosphorus 0.01-60 parts and carbon 1-100 parts.