Silicon monoxide composite material as well as preparation method and application thereof

Abstract

The invention discloses a silicon monoxide composite material as well as a preparation method and application thereof. The preparation method comprises the following steps: 1) carrying out ball-milling mixing on a doped element material and a silicon monoxide material by adopting a solid phase method to obtain a mixture; 2) adding an organic nitrogen source into the mixture, and carrying out secondary ball-milling mixing; and (3) calcining the mixed material in the step (2) in an inert atmosphere, and crushing and screening after calcining to obtain the double-doped silicon monoxide negative electrode material. And 4) mixing the double-doped silicon monoxide negative electrode material with carbon element-containing gas and nitrogen element-containing gas, and reacting to generate the silicon monoxide composite material. In order to improve the initial coulombic efficiency and cycle performance of the silicon monoxide material, the silicon monoxide material is subjected to surface coating, and the problem of volume expansion of the silicon monoxide material in the charging and discharging process can be effectively inhibited.

Description

Technical Field

[0001] The present invention belongs to the field of silicon oxide materials and relates to a silicon oxide composite material and a preparation method and application thereof. Background Art

[0002] The cruising range of electric vehicles is related to changes in people's needs and the future development of the automotive industry. In order to achieve an energy density of 300wh / kg for power batteries, it is inevitable to replace the commercialized lithium iron phosphate and lithium cobalt oxide with ternary materials as the positive electrode material of lithium-ion batteries; and replacing the graphite negative electrode with silicon-carbon materials to exponentially increase the energy density of the battery is also an inevitable trend in the development of the new energy vehicle industry.

[0003] Due to the low platform potential of silicon, the ultra-high theoretical capacity (3800mAh / g, Li 15 Si4; 4200mAh / g, Li 15 Si4 (nearly 10 times the capacity of commercially available graphite), with advantages such as high surface area, high tap density, and simple preparation, holds great promise for application. However, silicon, as a negative electrode material, undergoes significant volume changes during charge and discharge, leading to a sharp decline in battery performance. While silicon oxide, with its high theoretical capacity and low volume expansion, is gaining attention, its initial coulombic efficiency and cycling performance need to be improved, and the volume expansion during charge and discharge still needs to be addressed. Summary of the Invention

[0004] The purpose of the present invention is to provide a silicon oxide composite material and a preparation method and application thereof.

[0005] The present invention provides a method for preparing a silicon oxide composite material, comprising the following steps: 1) ball milling a doping element material and a silicon oxide material using a solid phase method to obtain a mixture; 2) adding an organic nitrogen source to the mixture and performing a second ball milling; 3) calcining the mixed materials in step 2) under an inert atmosphere, crushing and sieving after calcination to obtain a dual-doped silicon oxide negative electrode material; 4) Mixing the dual-doped silicon oxide negative electrode material with carbon-containing gas and nitrogen-containing gas to react and generate a silicon oxide composite material. In order to improve the initial coulombic efficiency and cycle performance of silicon monoxide materials, the present invention coats the surface of silicon monoxide materials, which can effectively suppress the volume expansion problem of silicon monoxide materials during charging and discharging.

[0006] In the above method, in step 1), the ball milling speed is 600-1000 rpm, specifically 800 rpm, and the time is 1-10 h, specifically 10 h.

[0007] In the above method, in step 1), the doping element in the doping element material is selected from at least one of Al, Na, Li, Mg, Ca, Ti, Mn, Fe, Co, Ni, Zr, Mo and Ge; The doping element material is selected from at least one of gallium oxide, gallium chloride and gallium nitride; The percentage of the doping element in the mass of the silicon oxide may be 0.01% to 8%.

[0008] In the above method, in step 2), the ball milling speed can be 500-1000 rpm, specifically 500 rpm, 500-700 rpm or 500-900 rpm, and the time can be 1-10 h, specifically 2 h, 1-2 h or 2-10 h.

[0009] In the above method, in step 2), the organic nitrogen source is selected from at least one of melamine, formamide, acetamide and urea; The mass ratio of the silicon monoxide to the organic nitrogen source may be 1:1-3, specifically 1:3.

[0010] In the above method, in step 3), the inert atmosphere includes argon or nitrogen; The calcination process is as follows: heating from room temperature to 350°C at a rate of 2°C / min~10°C / min, and calcining at 350°C for 1h~3h; then heating from 350°C to 650°C~800°C at a rate of 2°C / min~10°C / min, and calcining at 650°C~800°C for 2h~6h; then heating from 650°C~800°C to 900°C at a rate of 2°C / min~10°C / min, and calcining at 900°C for 2h~6h.

[0011] In the present invention, the room temperature is common knowledge in the art, specifically 10-30°C.

[0012] In the above method, in step 4), the mixing is carried out in a plasma emitter and the reaction is carried out in a vacuum furnace; The temperature of the plasma emitter is set to 900-1100°C; The vacuum furnace is a closed furnace with a vacuum plasma emitter, and the vacuum is evacuated to 1-0.1 Pa.

[0013] In the above method, in step 4), the carbon-containing gas is selected from at least one of methane, ethane, ethylene, propylene, acetylene and propyne; The nitrogen-containing gas is ammonia and / or nitrogen; The volume ratio of the carbon-containing gas to the nitrogen-containing gas is 1:0.25-4. The present invention also provides a silicon monoxide composite material obtained by the above preparation method.

[0014] The present invention further provides a lithium ion battery comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the negative electrode is made of an active material, a conductive agent and a binder; The active material is the above-mentioned silicon monoxide composite material.

[0015] The present invention has the following beneficial effects: 1. The doping element (such as gallium) in the dual-doped carbon-coated silicon oxide composite material of the present invention has the function of stabilizing the structure of graphite and silicon oxide. The crystal form and grain boundary formation of the generated dual-doped silicon oxide negative electrode material can be adjusted and controlled by sintering the mixed powder in different temperature zones for a certain length of time.

[0016] 2. A high-conductivity transition layer of silicon nitride is formed on the surface and interface of the nitrogen-doped silicon oxide negative electrode material, which not only stabilizes the lattice structure of the electrode material and blocks the irreversible reaction caused by direct contact between the electrolyte and the silicon oxide material, but also realizes the rapid conduction of lithium ions and electrons, thereby improving the overall performance of the nitrogen-doped silicon oxide negative electrode material.

[0017] 3. By coating silicon oxide material with carbon nitride, a silicon oxide material coated with a conductive coating layer with a strong structure is prepared, which inhibits the volume expansion of the silicon oxide material during charging and discharging, avoids direct contact between the silicon oxide material and the electrolyte, and thus improves the cyclic stability of the material.

[0018] 4. The materials prepared by the present invention have properties such as high energy density and low volume expansion, and have broad application prospects in the fields of high-energy-density batteries, back-end electric vehicles, and energy storage base stations. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 These are SEM images of the doped and coated silicon monoxide materials in Example 1 of the present invention and Comparative Example 1.

[0020] Figure 2 1 is a cycle diagram of the doped and coated silicon monoxide material in Example 1 of the present invention and Comparative Example 1.

[0021] Figure 3 This is an SEM image of the doped and coated silicon monoxide material in Example 2 of the present invention.

[0022] Figure 4 This is a cycle diagram of the doped and coated silicon monoxide material in Example 2 of the present invention. DETAILED DESCRIPTION

[0023] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0024] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0025] The technical solution of the present invention is described in detail below through specific embodiments.

[0026] Example 1 S1: 1 kg of porous gallium nitride and 4 kg of silicon dioxide were mixed evenly, placed in a ball mill, and milled for 10 h in an argon atmosphere at a speed of 800 rpm, with both forward and reverse rotations, to fully mix the silicon dioxide and gallium nitride to obtain mixed material A; S2: adding melamine to mixture A at a mass ratio of 1:3 between the silicon oxide mixture and melamine, and ball milling the mixture in a polytetrafluoroethylene ball mill at 500 rpm for 2 h to obtain mixture B; S3: Transfer mixture B to a crucible, place it in a glass rotary kiln in a nitrogen atmosphere, heat it to 350°C at a speed of 2 rpm and a rate of 5°C / min and keep it for 2 hours, then heat it to 700°C at a rate of 3°C / min and keep it for 2 hours, and then heat it to 900°C and keep it for 5 hours; cool it to room temperature to obtain an in-situ gallium and nitrogen co-doped silicon dioxide material; S4: In situ gallium and nitrogen co-doped silicon oxide material is injected into a plasma emitter together with carbon-containing methane and nitrogen-containing ammonia gas in a volume ratio of 3:4. The temperature of the plasma emitter is controlled at 950°C, and a dual-doped carbon nitride-coated silicon oxide composite material is generated in a vacuum furnace (a closed furnace with a plasma emitter that is evacuated to 0.1 Pa).

[0027] Example 2 Steps S1-S3 are the same as those in Example 1 of the present invention.

[0028] S4: Silicon oxide is injected into a plasma emitter together with acetylene, a carbon-containing gas, and ammonia, a nitrogen-containing gas, in a volume ratio of 1:4. The temperature of the plasma emitter is controlled at 1000°C, and a double-doped carbon nitride-coated silicon oxide composite material is generated in a vacuum furnace (a closed furnace with a plasma emitter that is evacuated to 0.2 Pa).

[0029] Comparative Example 1 S1: 1 kg of porous gallium nitride and 4 kg of silicon dioxide were mixed evenly, placed in a ball mill, and milled in an argon atmosphere at 800 rpm, with both forward and reverse rotations, for 10 hours to fully mix the silicon dioxide and gallium nitride to obtain mixed material A.

[0030] S2: adding melamine to mixture A at a mass ratio of 1:3 between the silicon oxide mixture and melamine, and ball milling the mixture in a polytetrafluoroethylene ball mill at 500 rpm for 2 h to obtain mixture B; S3: Transfer mixture B into a crucible, place it in a glass rotary kiln in a nitrogen atmosphere, heat it to 350°C at a speed of 5°C / min at a rotation speed of 2 rpm and keep it warm for 2 hours, then heat it to 700°C at a speed of 3°C / min and keep it warm for 2 hours, and then heat it to 900°C and keep it warm for 5 hours; cool it to room temperature to obtain an in-situ gallium and nitrogen co-doped silicon monoxide material.

[0031] Comparative Example 2 S1: Place 4 kg of silicon dioxide in a ball mill, set the speed to 800 rpm, rotate forward and reverse, and ball mill for 10 hours in an argon atmosphere to obtain material A; S2: Add melamine to material A at a mass ratio of 1:3 between silicon dioxide and melamine, and ball mill the mixture in a polytetrafluoroethylene ball mill at 500 rpm for 2 h to obtain mixture B; S3: Transfer mixture B into a crucible, place it in a glass rotary kiln in a nitrogen atmosphere, and heat it from room temperature (25°C) to 350°C at a speed of 2 rpm and a rate of 5°C / min, and keep it for 2 hours. Then heat it to 700°C at a rate of 3°C / min and keep it for 2 hours, and then heat it to 900°C and keep it for 5 hours. Cool it to room temperature (25°C) to obtain an in-situ nitrogen-doped silicon dioxide material. S4: The doped silicon oxide material is injected into a plasma emitter together with carbon-containing methane and nitrogen-containing ammonia gas in a volume ratio of 3:4. The temperature of the plasma emitter is controlled at 950°C, and a silicon oxide composite material is generated in a vacuum furnace (a closed furnace with a plasma emitter that is evacuated to 0.1 Pa).

[0032] Comparative Example 3 S1: 1 kg of porous gallium nitride and 4 kg of silicon dioxide were mixed evenly, placed in a ball mill, and milled for 10 hours in an argon atmosphere at a speed of 800 rpm, with both forward and reverse rotations, to fully mix the silicon dioxide and gallium nitride to obtain mixed material A; S2: The mixed material A was further ball-milled in a polytetrafluoroethylene ball mill at a speed of 500 rpm for 2 h; S3: The mixture was transferred to a crucible, placed in a glass rotary kiln in a nitrogen atmosphere, and heated to 350°C at a speed of 5°C / min at a rotation speed of 2 rpm and kept warm for 2 h, then heated to 700°C at a speed of 3°C / min and kept warm for 2 h, and then heated to 900°C and kept warm for 5 h; cooled to room temperature (25°C) to obtain in-situ gallium-doped silicon dioxide material.

[0033] S4: The doped silicon oxide material is injected into a plasma emitter together with carbon-containing methane and nitrogen-containing ammonia gas in a volume ratio of 3:4. The temperature of the plasma emitter is controlled at 950°C, and a silicon oxide composite material is generated in a vacuum furnace (a closed furnace with a plasma emitter that is evacuated to 0.1 Pa).

[0034] The dual-doped carbon nitride-coated silicon oxide composites prepared in the above examples and comparative examples were used as active materials, respectively, mixed with super-P (superconducting carbon black) conductive agent and PVDF (polyvinylidene fluoride) binder in a mass ratio of 85:5:10. The mixture was then coated onto an 8μm copper foil to form the negative electrode. A lithium sheet was used as the positive electrode to assemble a CR2016 button-type battery. The electrolyte used was a 1 mol / L LiPF6 solution in EC (ethylene carbonate) and DMC (dimethyl carbonate) (EC:DMC = 1:1), and the separator was a PP (polypropylene) membrane. Electrochemical performance testing was conducted. The first week of charge and discharge testing was conducted at 0.05C, with a charge and discharge range of 0.05-1.5V. The measured data are shown in Table 1.

[0035] The steps for determining the full-charge expansion rate are as follows: The electrode pieces prepared in the above different embodiments and comparative examples were tested for thickness after rolling. After being assembled into button batteries, they were fully charged at 0.05C and disassembled to test the thickness of the electrode pieces in the fully charged state. The full charge rebound rate of the different experimental electrode pieces was calculated.

[0036] As can be seen from the data in Table 1, compared with button cells prepared with partially doped coating or only doped materials as active materials, the button cells prepared with the silicon oxide composite materials of Examples 1 and 2 as active materials have significantly improved initial discharge capacity and initial efficiency. Under the conditions of a 0.05C rate and a charge and discharge range of 0.05-1.5V, the electrode prepared with the composite material of Example 2 has an initial discharge capacity of 2234.5mAh / g, and the full-charge expansion is significantly reduced, indicating that the dual-doping coating of the present invention can significantly improve the initial efficiency of the silicon oxide composite material and reduce the expansion of the silicon oxide material.

[0037] Table 1 Button battery test results

[0038] The morphology of the silicon oxide material obtained in Example 1 was detected by SEM using methane and ammonia gas at a vacuum of 0.1 Pa and a plasma emitter temperature of 950°C. Figure 1 shown.

[0039] Depend on Figure 1 It can be seen that in the doped and coated silicon nitride composite material obtained in Example 1, carbon nitride is uniformly coated on the surface of silicon nitride.

[0040] Depend on Figure 2 It can be seen that compared with the uncoated material in Comparative Example 1 and the material in Example 1, the button battery made of the doped and coated silicon iodine composite material prepared in Example 1 of the present invention significantly improves the cycle performance of the silicon iodine composite material.

[0041] The morphology of the silicon oxide composite material obtained in Example 2 was examined by SEM using acetylene and ammonia gas under the conditions of vacuum of 0.2 Pa and plasma emitter temperature of 1000°C. Figure 3 shown.

[0042] Depend on Figure 3 It can be seen that in the doped and coated silicon oxide composite material obtained in Example 2 of the present invention, carbon nitride is uniformly coated on the surface of silicon oxide. Figure 4 It can be seen that the first coulombic efficiency of the silicon 2 oxide composite material obtained in Example 2 of the present invention is higher than that of the uncoated silicon 2 oxide material in Comparative Example 1 and the single doped and coated silicon 2 oxide material in Comparative Examples 2-3.

[0043] Depend on Figure 4 It can be seen that compared with the carbon coating method in Comparative Example 2, the button battery made of the silicon oxide composite material prepared in Example 2 has significantly improved its cycle performance.

[0044] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a silicon oxide composite material, comprising the following steps: 1) ball milling a doping element material and a silicon oxide material using a solid phase method to obtain a mixture; 2) adding an organic nitrogen source to the mixture and performing a second ball milling; 3) calcining the mixed materials in step 2) under an inert atmosphere, crushing and sieving after calcination to obtain a dual-doped silicon oxide negative electrode material; 4) Mixing the dual-doped silicon oxide negative electrode material with carbon-containing gas and nitrogen-containing gas to react and generate a silicon oxide composite material.

2. The method according to claim 1, characterized in that In step 1), the ball milling speed is 600-1000 rpm and the time is 1-10 h.

3. The method according to claim 1 or 2, characterized in that In step 1), the doping element in the doping element material is selected from at least one of Al, Na, Li, Mg, Ca, Ti, Mn, Fe, Co, Ni, Zr, Mo and Ge; The doping element material is selected from at least one of gallium oxide, gallium chloride and gallium nitride; The percentage of the doping element in the mass of the silicon oxide may be 0.01% to 8%.

4. The method according to claim 1 or 2, characterized in that In step 2), the ball milling speed is 500-1000 rpm and the time is 1-10 h.

5. The method according to claim 1 or 2, characterized in that In step 2), the organic nitrogen source is selected from at least one of melamine, formamide, acetamide and urea; The mass ratio of the silicon monoxide to the organic nitrogen source is 1:1-3.

6. The method according to claim 1 or 2, characterized in that In step 3), the inert atmosphere includes argon or nitrogen; The calcination process is as follows: heating from room temperature to 350°C at a rate of 2°C / min~10°C / min, and calcining at 350°C for 1h~3h; then heating from 350°C to 650°C~800°C at a rate of 2°C / min~10°C / min, and calcining at 650°C~800°C for 2h~6h; then heating from 650°C~800°C to 900°C at a rate of 2°C / min~10°C / min, and calcining at 900°C for 2h~6h.

7. The method according to claim 1 or 2, characterized in that In step 4), the mixing is carried out in a plasma emitter and the reaction is carried out in a vacuum furnace; The temperature of the plasma emitter is set to 900-1100°C; The vacuum furnace is a closed furnace with a vacuum plasma emitter, and the vacuum is evacuated to 1-0.1 Pa.

8. The method according to claim 1 or 2, characterized in that In step 4), the carbon-containing gas is selected from at least one of methane, ethane, ethylene, propylene, acetylene and propyne; The nitrogen-containing gas is ammonia and / or nitrogen; The volume ratio of the carbon-containing gas to the nitrogen-containing gas is 1:0.25-4.

9. The silicon monoxide composite material obtained by the preparation method according to any one of claims 1 to 8.

10. A lithium-ion battery comprising a positive electrode, a negative electrode, a separator and an electrolyte, characterized in that: The negative electrode is made of active material, conductive agent and binder; The active material is the silicon monoxide composite material according to claim 9.

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