Dual-doped silicon-based lithium ion negative electrode material, preparation method and application thereof

Abstract

The application relates to a double-doped silicon-based lithium ion negative electrode material and a preparation method and application thereof. The method comprises the following steps: taking a nitrogen-containing gas source or a high-boiling-point nitrogen-containing compound as a first doping material, taking a metal or a metal composite phase material as a second doping material, mixing the second doping material with silicon and / or silicon dioxide in a certain proportion, processing the second doping material into a gas, mixing the gas with a vapor of the first doping material, and then depositing the mixture on a substrate to obtain a silicon-oxygen composite material; cooling the silicon-oxygen composite material to room temperature, discharging, crushing and screening; and coating the crushed and screened material with carbon to obtain the double-doped silicon-based lithium ion negative electrode material.

Description

Technical Field

[0001] This invention relates to the field of materials preparation technology, and in particular to a double-doped silicon-based lithium-ion anode material, its preparation method, and its application. Background Technology

[0002] With the rapid development of new energy vehicles, the industry has placed higher demands on the performance of power batteries. Anode materials are one of the most critical materials in lithium-ion battery technology. Currently, commercially available graphite anodes have reached their technological bottleneck due to their low specific capacity. Silicon-based materials are among the most promising lithium-ion anode materials to replace them. Silicon-based anode materials, boasting a specific capacity as high as 4200 mAh / g and possessing three-dimensional diffusion channels, are gradually demonstrating their advantage in high energy density.

[0003] Amorphous silicon suboxide (SiO2) is composed of silicon clusters smaller than 5 nm uniformly dispersed within a silica matrix. Its good cycle stability and high specific capacity (1200-1900 mAh / g) make it a suitable anode material. Strong silicon-oxygen bonds and the formation of lithium silicates and lithium oxide during cycling provide excellent cycle performance by buffering volume expansion. However, the formation of lithium silicates and lithium oxide also results in a high irreversible capacity in the first cycle, leading to a relatively low energy density in lithium-ion batteries. Coating the surface of SiO2 with carbon materials, metal oxides, or composite materials can improve conductivity and first-cycle coulombic efficiency.

[0004] In patent CN109286012A, researchers prepared electrochemically active silicon suboxide-carbon / graphene materials using a sol-gel method and a carbothermal reduction method. Then, through spin coating and heat treatment, they prepared dispersed fast-ion conductor lithium silicate on the surface of the silicon suboxide-carbon material, ultimately obtaining a silicon suboxide-carbon@lithium silicate / graphene material. Although this work simultaneously increased ionic and electronic conductivity, the specific capacity of the lithium-ion battery was low, less than 800 mAh / g, indicating poor quality of the prepared silicon suboxide composite material. In patent CN 107946568A, a hard carbon / graphite / silicon suboxide composite material was obtained by combining hard carbon slurry / graphite and silicon suboxide particles and then carbonizing at high temperature. This silicon suboxide composite material combined the advantages of hard carbon and silicon suboxide, but did not exhibit excellent rate performance. Summary of the Invention

[0005] This invention provides a dual-doped silicon-based lithium-ion anode material, its preparation method, and its application. By introducing the vapor of each dopant material and mixing it with the matrix material in the gas phase, a uniformly doped silicon-oxygen composite material is obtained. This not only improves the rate performance of the material but also mitigates the volume expansion effect and increases the first-cycle efficiency.

[0006] In a first aspect, embodiments of the present invention provide a method for preparing a dual-doped silicon-based lithium-ion anode material, comprising:

[0007] Using a nitrogen-containing gas source or a high-boiling-point nitrogen-containing compound as the first doping material, and a metal or metal composite phase material as the second doping material, the second doping material is mixed with silicon and / or silicon dioxide in a certain proportion and then treated into a gas, which is then mixed with the vapor of the first doping material and deposited on a substrate to obtain a silicon-oxygen composite material.

[0008] The silicon-oxygen composite material is cooled to room temperature and then discharged, crushed, and screened.

[0009] The crushed and screened material is then coated with carbon to obtain a double-doped silicon-based lithium-ion anode material.

[0010] Preferably, the nitrogen-containing gas source specifically includes one or more of nitrogen, ammonia, nitrous oxide, or dimethylamine;

[0011] The high-boiling-point nitrogen-containing compounds specifically include: carbamide or melamine;

[0012] The metal or metal composite phase material specifically includes one or more of the following elements: B, Al, Na, Mg, Ca, Ba, Ti, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, Ge, and Sn, either as a single element, alloy, or composite oxide.

[0013] Preferably, the vapor of the first doped material is obtained by heating the first doped material to 25°C-800°C.

[0014] Preferably, the mass of the first doped material accounts for 0.01%-3% of the total mass of the silicon-oxygen composite material; and the mass of the second doped material accounts for 2%-40% of the total mass of silicon and silicon dioxide.

[0015] Preferably, the molar ratio of silicon to silicon dioxide is silicon:silicon dioxide = 1:1.

[0016] Preferably, the temperature of the substrate is 50-800°C.

[0017] Preferably, the carbon coating specifically involves: placing the crushed and screened material in a rotary kiln, heating it to 800℃-1000℃ under a protective atmosphere, introducing an organic gas source for chemical vapor deposition, holding it at that temperature for 2-4 hours, and then turning off the organic gas source to cool it down; wherein, the organic gas source specifically includes one or more of methane, acetylene, propylene, or propane; the mass of the carbon film formed by the carbon coating accounts for 1%-10% of the mass of the silicon-oxygen composite material.

[0018] Secondly, embodiments of the present invention provide a lithium-ion battery anode material, including a double-doped silicon-based lithium-ion anode material prepared by the preparation method described in the first aspect.

[0019] Thirdly, embodiments of the present invention provide a lithium battery electrode sheet, wherein the lithium battery electrode sheet comprises the lithium-ion battery negative electrode material described in the second aspect above.

[0020] Fourthly, embodiments of the present invention provide a lithium battery, the lithium battery comprising the lithium battery electrode described in the third aspect above.

[0021] The method for preparing dual-doped silicon-based lithium-ion anode materials provided by this invention introduces a first dopant that can undergo internal diffusion at high temperatures, significantly improving the rate performance of the material. The second dopant can form a silicon-oxygen complex with silicon suboxide, consuming inert silicon dioxide and creating a buffer region, thus mitigating the volume expansion effect and improving first-cycle efficiency, while also increasing cycle stability. Carbon coating further enhances coating integrity and the material's conductivity. Attached Figure Description

[0022] The technical solutions of the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples.

[0023] Figure 1 This is a flowchart illustrating the preparation method of the dual-doped silicon-based lithium-ion anode material according to an embodiment of the present invention.

[0024] Figure 2 This is a scanning electron microscope image of the silicon-doped lithium-ion battery anode material provided in Embodiment 1 of the present invention. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, it should be understood that these embodiments are only for more detailed description and should not be construed as limiting the present invention in any way, that is, not intended to limit the scope of protection of the present invention.

[0026] The preparation method of the dual-doped silicon-based lithium-ion anode material of the present invention comprises the following steps: Figure 1 As shown, it includes:

[0027] Step 110: Using a nitrogen-containing gas source or a high-boiling-point nitrogen-containing compound as the first doping material, and a metal or metal composite phase material as the second doping material, the second doping material is mixed with silicon and / or silicon dioxide in a certain proportion and then treated into a gas, which is then mixed with the vapor of the first doping material and deposited on the substrate to obtain a silicon-oxygen composite material.

[0028] The vapor of the first doped material is obtained by heating the first doped material to 25°C-800°C.

[0029] In the first doped material, the nitrogen source is a nitrogen-containing compound that is gaseous at room temperature, specifically including one or more of nitrogen, ammonia, nitrous oxide, or dimethylamine; the high-boiling-point nitrogen-containing compound is a nitrogen-containing compound that is liquid or solid at room temperature, specifically including one or more of carbamide or melamine.

[0030] The first dopant accounts for 0.01%-3% of the total mass of the silicon-oxygen composite material; the second dopant accounts for 2%-40% of the total mass of silicon and silicon dioxide. The preferred molar ratio of silicon to silicon dioxide is silicon:silicon dioxide = 1:1.

[0031] Metallic or metallic composite phase materials specifically include one or more of the following elements: B, Al, Na, Mg, Ca, Ba, Ti, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, Ge, and Sn, either as a single element, alloy, or composite oxide.

[0032] The substrate is a carrier for vapor deposition, such as stainless steel, graphite, or alumina, and the temperature of the substrate is 50-800℃.

[0033] Step 120: Cool the silicon-oxygen composite material to room temperature and discharge it for crushing and screening;

[0034] Step 130: Carbon coating is applied to the crushed and screened material to obtain a double-doped silicon-based lithium-ion anode material.

[0035] The carbon coating process involves placing the crushed and screened material in a rotary kiln, heating it to 800℃-1000℃ under a protective atmosphere, introducing an organic gas source for chemical vapor deposition, holding it at that temperature for 2-4 hours, and then turning off the organic gas source to cool it down.

[0036] The organic gas source specifically includes one or more of methane, acetylene, propylene, or propane; the carbon coating formed by carbon coating accounts for 1%-10% of the mass of the silicon-oxygen composite material.

[0037] The above preparation method introduces a first dopant material that can undergo internal diffusion at high temperatures, significantly improving the rate performance of the material. The second dopant material forms a silicon-oxygen complex with silicon suboxide, consuming inert silicon dioxide and creating a buffer region, thus mitigating volume expansion and improving first-cycle efficiency, while also increasing cycle stability. Carbon coating further enhances coating integrity and the material's conductivity.

[0038] The double-doped silicon-based lithium-ion anode material prepared by the method in this embodiment can be used as a lithium-ion battery anode material and applied in lithium battery electrodes and lithium batteries.

[0039] To better understand the technical solution provided by the present invention, the following uses several specific examples to illustrate the specific process of preparing lithium battery anode materials using the methods provided in the above embodiments of the present invention, as well as the method of applying them to lithium batteries and the battery characteristics.

[0040] Example 1

[0041] 1.4 kg of silicon powder, 3 kg of silicon dioxide, and 220 g of metallic magnesium were mixed evenly and heated to produce steam. Simultaneously, 60 g of melamine was heated to 320°C and produced steam. After being evenly mixed, the mixture was deposited onto a substrate at a temperature of 500°C. The material was then discharged, crushed, and screened.

[0042] Two kg of the sieved material was placed in a rotary kiln and heated to 1000°C under a protective argon atmosphere. Argon and propane were introduced at a volume ratio of 1:1 for chemical vapor deposition. After holding at this temperature for 2 hours, the organic gas source was turned off and the material was cooled to obtain the doped silicon-based lithium-ion battery anode material. The resulting material contained 4.7% magnesium, 0.87% nitrogen, and 3% carbon. Scanning electron microscope image of the dual-doped silicon-based lithium-ion battery anode material.

[0043] The obtained silicon-doped lithium-ion battery anode material, conductive additive carbon black, binder sodium cellulate (1:1 ratio), and styrene-butadiene rubber were weighed in a mass ratio of 95%:2%:3%. At room temperature, the mixture was placed in a pulping machine to prepare a slurry. The prepared slurry was then uniformly coated onto copper foil. After drying in a forced-air drying oven at 50°C for 2 hours, the foil was cut into 8×8mm electrode sheets and vacuum-dried in a vacuum drying oven at 100°C for 10 hours. The dried electrode sheets were then immediately transferred to a glove box for use in battery assembly.

[0044] The simulated battery assembly was performed in a glove box containing a high-purity Ar atmosphere. Lithium metal was used as the counter electrode, and a 1-molar LiPF6 solution in ethylene carbonate (EC) / dimethyl carbonate (DMC) was used as the electrolyte. Constant current charge-discharge mode tests were conducted using a charge-discharge apparatus. The discharge cutoff voltage was 0.005V, and the charge cutoff voltage was 1.5V. The first week of charge-discharge testing was performed at a current density of C / 10, and the second week of discharge testing was performed at a current density of C / 10. The test data are shown in Table 1.

[0045] Example 2

[0046] 2.8 kg of silicon powder, 6 kg of silicon dioxide, and 5 kg of magnesium silicate were mixed evenly and heated to produce steam. Simultaneously, 20 g of nitrogen gas was introduced. The mixed steam was then deposited onto a substrate at a temperature of 400°C. The material was then discharged, crushed, and screened.

[0047] 2 kg of the sieved material was placed in a rotary kiln and heated to 950°C under a protective argon atmosphere. Argon and propylene were introduced in a volume ratio of 1:1 for chemical vapor deposition. After holding at this temperature for 4 hours, the organic gas source was turned off and the material was allowed to cool naturally to obtain the dual-doped silicon-based lithium-ion battery anode material.

[0048] The resulting anode material contains 8.7% magnesium, 0.145% nitrogen, and 6% carbon.

[0049] The preparation process of the negative electrode sheet, the battery assembly, and the battery testing methods are the same as in Example 1.

[0050] Example 3

[0051] 2.8 kg of silicon powder, 6 kg of silicon dioxide, and 704 g of metallic magnesium were mixed evenly and heated to produce steam. Simultaneously, 225 g of carbamide was heated to 400°C and produced steam. The steam mixture was then deposited onto a substrate at a temperature of 500°C. The resulting material was then discharged, crushed, and screened.

[0052] 2 kg of the sieved material was placed in a rotary kiln and heated to 800°C under a protective argon atmosphere. Argon and acetylene were introduced at a volume ratio of 1:2 for chemical vapor deposition. After holding at this temperature for 1 hour, the organic gas source was turned off and the material was allowed to cool naturally to obtain the double-doped silicon-based lithium-ion battery anode material.

[0053] The resulting anode material contains 7.4% magnesium, 1.2% nitrogen, and 3% carbon.

[0054] The preparation process of the negative electrode sheet, the battery assembly, and the battery testing methods are the same as in Example 1.

[0055] Example 4

[0056] 1.4 kg of silicon powder, 3 kg of silicon dioxide, and 1.02 kg of alumina were mixed evenly and heated to produce steam. Simultaneously, 17 g of ammonia gas was introduced. The mixed steam was deposited onto a substrate at a temperature of 600°C. The material was then discharged, crushed, and screened.

[0057] 2 kg of the sieved material was placed in a rotary kiln and heated to 950°C under a protective argon atmosphere. Argon and a mixed gas were introduced at a volume ratio of 1:2 for chemical vapor deposition. The mixed gas consisted of acetylene and propane at a volume ratio of 1:1. After holding at this temperature for 1 hour, the organic gas source was turned off and the material was allowed to cool naturally to obtain the double-doped silicon-based lithium-ion battery anode material.

[0058] The resulting negative electrode material contains 10% aluminum, 0.25% nitrogen, and 3.5% carbon.

[0059] The preparation process of the negative electrode sheet, the battery assembly, and the battery testing methods are the same as in Example 1.

[0060] Example 5

[0061] 1.4 kg of silicon powder, 3 kg of silicon dioxide, and 700 g of boron oxide were mixed evenly and heated to produce steam. Simultaneously, 126 g of melamine was heated to 600°C and produced steam. The steam mixture was then deposited onto a substrate at 300°C. The material was then discharged, crushed, and screened.

[0062] 2 kg of the sieved material was placed in a rotary kiln and heated to 1000°C under a protective argon atmosphere. Argon and a mixed gas were introduced at a volume ratio of 2:3 for chemical vapor deposition. The mixed gas consisted of methane and propane at a volume ratio of 2:1. After holding at this temperature for 2 hours, the organic gas source was turned off and the material was allowed to cool naturally to obtain the double-doped silicon-based lithium-ion battery anode material.

[0063] The resulting anode material contains 4.5% boron, 1.65% nitrogen, and 8% carbon.

[0064] The preparation process of the negative electrode sheet, the battery assembly, and the battery testing methods are the same as in Example 1.

[0065] Example 6

[0066] 1.4 kg of silicon powder, 3 kg of silicon dioxide, and 500 g of tin were mixed evenly and heated to produce steam. Simultaneously, 20 g of nitrogen gas was introduced. The mixed steam was then deposited onto a substrate at a temperature of 400°C. The material was then discharged, crushed, and screened.

[0067] 2 kg of the sieved material was placed in a rotary kiln and heated to 1000°C under a protective argon atmosphere. Argon and a mixed gas were introduced at a volume ratio of 1:2 for chemical vapor deposition. The mixed gas consisted of methane and propylene at a volume ratio of 1:1. After holding at this temperature for 1 hour, the organic gas source was turned off and the material was allowed to cool naturally to obtain the dual-doped silicon-based lithium-ion battery anode material.

[0068] The resulting anode material contains 10.2% tin, 0.41% nitrogen, and 3% carbon.

[0069] The preparation process of the negative electrode sheet, the battery assembly, and the battery testing methods are the same as in Example 1.

[0070] Example 7

[0071] 1.4 kg of silicon powder, 3 kg of silicon dioxide, and 400 g of copper were mixed evenly and heated to produce steam. Simultaneously, 20 g of nitrogen gas was introduced. The mixed steam was then deposited onto a substrate at a temperature of 400°C. The material was then discharged, crushed, and screened.

[0072] 2 kg of the sieved material was placed in a rotary kiln and heated to 950°C under a protective argon atmosphere. Argon and a mixed gas were introduced at a volume ratio of 1:2 for chemical vapor deposition. The mixed gas consisted of acetylene and propane at a volume ratio of 1:1. After holding at this temperature for 2 hours, the organic gas source was turned off and the material was allowed to cool naturally to obtain the dual-doped silicon-based lithium-ion battery anode material.

[0073] The resulting anode material contains 8.3% copper, 0.41% nitrogen, and 4% carbon.

[0074] The preparation process of the negative electrode sheet, the battery assembly, and the battery testing methods are the same as in Example 1.

[0075] Comparative Example 1

[0076] This comparative example provides a lithium-ion battery anode material compared to Example 1.

[0077] 1.4 kg of silicon powder and 3 kg of silicon dioxide were placed in a high-temperature reactor and heated to turn into steam. At the same time, 60 g of melamine was heated to 320°C and turned into steam. The steam was mixed and deposited onto a substrate at a temperature of 500°C. The material was then discharged, crushed, and screened.

[0078] 2 kg of the sieved material was placed in a rotary kiln and heated to 1000°C under a protective argon atmosphere. Argon and propane were introduced in a volume ratio of 1:1 for chemical vapor deposition. After holding at this temperature for 2 hours, the organic gas source was turned off and the material was allowed to cool naturally to obtain the double-doped silicon-based lithium-ion battery anode material.

[0079] The resulting anode material contains 0.9% nitrogen and 3% carbon.

[0080] The preparation process of the negative electrode sheet, the battery assembly, and the battery testing methods are the same as in Example 1.

[0081] Comparative Example 2

[0082] Comparative Example 2 provides a lithium-ion battery anode material compared to Example 1.

[0083] 1.4 kg of silicon powder, 3 kg of silicon dioxide, and 220 g of metallic magnesium are mixed evenly and heated to turn into steam. The steam mixture is then deposited onto a substrate at a temperature of 500°C. The material is then discharged, crushed, and screened.

[0084] 2 kg of the sieved material was placed in a rotary kiln and heated to 1000°C under a protective argon atmosphere. Argon and propane were introduced in a volume ratio of 1:1 for chemical vapor deposition. After holding at this temperature for 2 hours, the organic gas source was turned off and the material was allowed to cool naturally to obtain the double-doped silicon-based lithium-ion battery anode material.

[0085] The resulting anode material contains 5% magnesium and 3% carbon.

[0086] The preparation process of the negative electrode sheet, the battery assembly, and the battery testing methods are the same as in Example 1.

[0087] The initial efficiency, 0.1C reversible capacity, and full-cell cycle retention (when used with graphite to form a 450mAh / g) of the anode materials in Examples 1-7 and Comparative Examples 1-2 were tested, and the results are listed in Table 1.

[0088]

[0089] Table 1

[0090] As can be seen from the data in Table 1, under the same conditions, Examples 1-7 all employed a dual-doped system, resulting in a significant improvement in the first-cycle cycling efficiency. Comparative Example 1, lacking a metal composite phase, exhibited low first-cycle efficiency. Although it had a high capacity, its cycling stability was poor after 100 and 500 cycles, indicating that the material had low long-term cycle retention due to the absence of a buffer region generated by the alloy phase. Comparative Example 2, lacking nitrogen doping, showed poor rate performance at high rates.

[0091] The method for preparing dual-doped silicon-based lithium-ion anode materials provided by this invention results in materials with higher first-cycle efficiency and better cycle stability.

[0092] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a dual-doped silicon-based lithium-ion anode material, characterized in that, The preparation method includes: Using a nitrogen-containing gas source as the first doping material and a metal as the second doping material, the second doping material, silicon, and silicon dioxide are mixed in a certain proportion and then processed into a gas. The gas is then mixed with the first doping material and deposited on a substrate to obtain a silicon-oxygen composite material. The silicon-oxygen composite material is cooled to room temperature and then discharged, crushed, and screened. The crushed and screened material is carbon-coated to obtain a dual-doped silicon-based lithium-ion anode material. The nitrogen-containing gas source includes one or more of nitrogen, ammonia, nitrous oxide, or dimethylamine; The metal is one or more of the following elements: Al, Na, Mg, Ca, Ba, Ti, Mn, Fe, Co, Ni, Cu, Zn, Zr, Ge, and Sn.

2. The preparation method according to claim 1, characterized in that, The mass of the second doped material accounts for 2%-40% of the total mass of silicon and silicon dioxide.

3. The preparation method according to claim 1, characterized in that, The molar ratio of silicon to silicon dioxide is 1:

1.

4. The preparation method according to claim 1, characterized in that, The temperature of the substrate is 400℃-800℃.

5. The preparation method according to claim 1, characterized in that, The carbon coating process specifically involves placing the crushed and screened material in a rotary kiln, heating it to 800℃-1000℃ under a protective atmosphere, introducing an organic gas source for chemical vapor deposition, maintaining the temperature for 2-4 hours, and then turning off the organic gas source to cool down. The organic gas source specifically includes one or more of methane, acetylene, propylene, or propane. The mass of the carbon film formed by the carbon coating accounts for 1%-10% of the mass of the silicon-oxygen composite material.

6. A lithium-ion anode material, characterized in that, The negative electrode material is a double-doped silicon-based lithium-ion negative electrode material prepared by any of the preparation methods described in claims 1-5.

7. A lithium-ion battery electrode, characterized in that, The lithium-ion battery electrode includes the lithium-ion negative electrode material described in claim 6.

8. A lithium-ion battery, characterized in that, The lithium-ion battery includes the lithium-ion battery electrode as described in claim 7.

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