Silicon-based negative electrode material and preparation method

Abstract

The present invention discloses a method for preparing silicon-based anode materials, specifically comprising: S1 placing a flexible substrate in the feeding chamber of a multi-target magnetron sputtering system; S2 simultaneously activating silicon and graphite targets to co-sputter nano-silicon and graphite carbon onto the flexible substrate to form a film layer; S3 after the co-sputtered film layer reaches a thickness of 1–20 μm, placing the coated sample containing the flexible substrate in an inert atmosphere calcination furnace for calcination; S4 pulverizing the calcined material to a D50 of 1–15 μm; S5 mixing the pulverized material with pitch for calcination, or placing the pulverized material in a CVD furnace and coating it with a mixture of acetylene and nitrogen; S6 sieving and demagnetizing the calcined and coated or CVD coated material to obtain the silicon-based anode material. This achieves uniform composite of carbon and nano- or even sub-nanometer-scale silicon. The silicon-based anode material prepared by the above method is also disclosed.

Description

Technical Field

[0001] This invention relates to the field of lithium battery anode material technology, specifically to silicon-based anode materials, and also to a method for preparing the silicon-based anode material. Background Technology

[0002] With the advancement of new energy lithium battery technology, batteries are increasingly developing towards lighter weight, miniaturization, and longer range, thus placing extremely high demands on battery energy density. As one of the five main materials of lithium batteries, the anode material plays a crucial role in improving battery energy density. Traditional graphite anode materials are approaching their theoretical capacity of 372 mAh / g, while silicon-based anode materials have a higher capacity than traditional graphite anode materials and are currently the core material for high-energy-density batteries.

[0003] Currently, the main technology for preparing silicon-carbon anode materials involves combining nano-silicon materials with carbon materials. Typically, nano-silicon materials are prepared first, and then combined with carbon materials to create a silicon-carbon composite material. To alleviate the significant volume changes and cycle degradation issues during lithium insertion / extraction of silicon, it is necessary to nanoscale the silicon material. Theoretically, the smaller the size of the nano-silicon, the better its expansion performance, but the worse its oxidation resistance and dispersibility. Currently, the main methods for silicon nanoscale preparation are sand milling and gas-phase pyrolysis. Nano-silicon prepared by these methods alone either has a large particle size or severe agglomeration, resulting in poor composite effects with carbon, thus posing significant challenges to the preparation of silicon-carbon anode materials. Currently, conventional silicon-carbon materials are basically prepared by combining nano-silicon larger than 100 nm with carbon materials. While this can meet commercial applications to some extent, it still faces problems such as significant expansion, low doping levels, low capacity matching, and limited improvement in battery energy density during actual use. Summary of the Invention

[0004] The first objective of this invention is to provide a method for preparing silicon-based anode materials, which achieves uniform composite of carbon with nano- or even sub-nano-scale silicon and complete and uniform coating of nano-silicon through subsequent solid-phase or gas-phase carbon coating, thereby improving the performance of silicon-based anode materials.

[0005] The second objective of this invention is to provide a silicon-based anode material.

[0006] The first technical solution adopted in this invention is a method for preparing silicon-based anode materials, comprising the following steps:

[0007] S1. Place the flexible substrate in the discharge chamber of the multi-target magnetron sputtering system;

[0008] S2. Simultaneously turn on the silicon target and the graphite target to co-sputter nano-silicon and graphite carbon on a flexible substrate and form a film of a certain thickness.

[0009] S3. After the co-sputtered film thickness reaches 1-20 μm, the coated sample containing the flexible substrate is placed in an inert atmosphere calcination furnace for calcination.

[0010] S4. Crush the calcined material to a density of D50 = 1-15 μm;

[0011] S5. Mix the pulverized material with asphalt, and then place it in a calcining furnace for calcination. The calcination temperature is 500-1000℃ and the calcination time is 1-3h; or place it in a CVD furnace, introduce a mixture of organic gas and nitrogen, and keep it at 700-1000℃ for 1-5h.

[0012] S6. The novel nano-silicon-based anode material is obtained by sieving and demagnetizing the material after solid-phase or gas-phase CVD coating.

[0013] The invention is further characterized in that,

[0014] In step S1, the flexible substrate material is one of PET, PI, PP, PE, PC, and PMMA;

[0015] In step S2, the silicon target is one of intrinsic silicon, P-type silicon target, N-type silicon target, and silicon suboxide target. The carbon mass content in the film formed by nano-silicon and graphite carbon is controlled at 10-50%, and the silicon mass content is controlled at 50-90%.

[0016] In step S3, the calcination temperature is controlled at 500–900℃, and the calcination time is 1–5 hours.

[0017] In step S5, the ratio of the crushed material to asphalt is 1:0.05 to 1:0.20; the volume ratio of the mixed gas is: organic gas: nitrogen = 0.2 to 1, and the organic gas is one of acetylene, methane, and propylene.

[0018] In step S6, a 300-400 mesh sieve is used for sieving.

[0019] The second technical solution adopted in this invention is a silicon-based anode material, which is prepared by the above-mentioned preparation method.

[0020] The beneficial effects of this invention are:

[0021] The gas-phase homogeneous composite technology proposed in this invention achieves uniform composite of carbon with nano- or even sub-nanometer-sized silicon. Furthermore, through subsequent solid-phase or gas-phase carbon coating, complete and uniform coating of the nano-silicon is achieved, thereby improving the performance of silicon-based anode materials. Since the composite of nano-silicon and carbon occurs simultaneously under vacuum conditions, both the uniformity of the composite and the good safety characteristics of nano-scale silicon-carbon composites are ensured. Attached Figure Description

[0022] Figure 1 The process flow for preparing the silicon-carbon composite anode of this invention is as follows;

[0023] Figure 2 A comparison diagram of silicon-carbon recycling in this invention and commercial silicon-carbon recycling. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0025] This invention provides a method for preparing a silicon-based anode material, such as... Figure 1 As shown, it includes the following steps:

[0026] S1. Place the flexible substrate in the discharge chamber of the multi-target magnetron sputtering system;

[0027] In step S1, the flexible substrate is made of one of the following materials: PET, PI, PP, PE, PC, and PMMA.

[0028] S2. Simultaneously turn on the silicon target and the graphite target to co-sputter nano-silicon and graphite carbon on the flexible substrate to form a film of a certain thickness. The growth rate of nano-silicon and graphite carbon is controlled by controlling the sputtering power of the two targets, wherein the growth rate of the film is 0.25~4nm / s.

[0029] In step S2, the carbon content in the film formed by nano-silicon and graphite carbon is controlled at 10-50%, and the silicon content is controlled at 50-90%.

[0030] In step S2, the silicon target is one of intrinsic silicon, P-type silicon target, N-type silicon target, and silicon suboxide, preferably an N-type heavily doped silicon target;

[0031] S3. After the co-sputtered film thickness reaches 1-20 μm, the coated sample containing the flexible substrate is placed in an inert atmosphere calcination furnace for calcination.

[0032] In step S3, the calcination temperature is controlled at 500–900℃, and the calcination time is 1–5 hours.

[0033] S4. Pulverize the calcined material to a D50 of 1-15 μm. The pulverization can be mechanical or air jet milling.

[0034] S5. Mix the pulverized material with asphalt, and then place it in a calcining furnace for calcination. The calcination temperature is 500-1000℃ and the calcination time is 1-3h; or place it in a CVD furnace, introduce a mixture of organic gas and nitrogen, and keep it at 700-1000℃ for 1-5h.

[0035] In step S5, the ratio of the crushed material to asphalt is 1:0.05 to 1:0.20; the volume ratio of the mixed gas is: organic gas: nitrogen = 0.2 to 1, and the organic gas is one of acetylene, methane, and propylene.

[0036] S6. The novel nano-silicon-based anode material is obtained by sieving and demagnetizing the material after solid-phase or gas-phase CVD coating.

[0037] In step S6, a 300-400 mesh sieve is used for sieving.

[0038] The present invention also provides a silicon-based anode material, which is prepared by the above-described preparation method.

[0039] Example 1

[0040] The preparation method of silicon-based anode materials includes the following steps:

[0041] S1. Place the flexible substrate in the discharge chamber of the multi-target magnetron sputtering system;

[0042] In step S1, the flexible substrate is made of PET.

[0043] S2. Simultaneously turn on the silicon target and the graphite target to co-sputter nano-silicon and graphite carbon on the flexible substrate to form a film. The growth rate of nano-silicon and graphite carbon is controlled by controlling the sputtering power of the two targets. The growth rate is 0.25nm / s.

[0044] In step S2, the carbon content in the film formed by nano-silicon and graphite carbon is controlled at 10%, and the silicon content is controlled at 90%; an N-type heavily doped silicon target is used.

[0045] S3. After the co-sputtered film thickness reaches 10μm, the coated sample containing the flexible substrate is placed in an inert atmosphere calcination furnace for calcination.

[0046] In step S3, the calcination temperature is controlled at 900℃ and the calcination time is 3 hours.

[0047] S4. Crush the calcined material to a size of D50 = 10 μm using air jet milling.

[0048] S5. Place the pulverized material in a CVD furnace, introduce a mixture of acetylene and nitrogen, and keep it at 900℃ for 4 hours.

[0049] In step S5, the volume ratio of the mixed gas is: acetylene: nitrogen = 0.2.

[0050] S6. The CVD-coated material is sieved and demagnetized to obtain the silicon-based anode material.

[0051] In step S6, a 300-mesh sieve is used for sieving.

[0052] Example 2

[0053] The preparation method of silicon-based anode materials includes the following steps:

[0054] S1. Place the flexible substrate in the discharge chamber of the multi-target magnetron sputtering system;

[0055] In step S1, the flexible substrate is made of PI.

[0056] S2. Simultaneously turn on the silicon target and the graphite target to co-sputter nano-silicon and graphite carbon on the flexible substrate to form a film. The growth rate of nano-silicon and graphite carbon is controlled by controlling the sputtering power of the two targets. The growth rate is 4nm / s.

[0057] In step S2, the carbon content and silicon content in the film formed by nano-silicon and graphite carbon are controlled at 50% by mass and 50% by mass; an N-type heavily doped silicon target is used.

[0058] S3. After the co-sputtered film thickness reaches 20μm, the coated sample containing the flexible substrate is placed in an inert atmosphere calcination furnace for calcination.

[0059] In step S3, the calcination temperature is controlled at 800℃ and the calcination time is 4 hours.

[0060] S4. Crush the calcined material to a size of D50 = 8μm using air jet milling.

[0061] S5. Place the pulverized material in a CVD furnace, introduce a mixture of formaldehyde and nitrogen, and keep it at 1000℃ for 3 hours.

[0062] In step S5, the volume ratio of the mixed gas is: formaldehyde: nitrogen = 1.

[0063] S6. The CVD-coated material is sieved and demagnetized to obtain the silicon-based anode material.

[0064] In step S6, a 400-mesh sieve is used for sieving.

[0065] Example 3

[0066] The preparation method of silicon-based anode materials includes the following steps:

[0067] S1. Place the flexible substrate in the discharge chamber of the multi-target magnetron sputtering system;

[0068] In step S1, the flexible substrate is made of PP.

[0069] S2. Simultaneously turn on the silicon target and the graphite target to co-sputter nano-silicon and graphite carbon on the flexible substrate to form a film. The growth rate of nano-silicon and graphite carbon is controlled by controlling the sputtering power of the two targets. The growth rate is 3nm / s.

[0070] In step S2, the carbon content in the film formed by nano-silicon and graphite carbon is controlled at 10%, and the silicon content is controlled at 90%; a p-type heavily doped silicon target is used.

[0071] S3. After the co-sputtered film thickness reaches 5μm, the coated sample containing the flexible substrate is placed in an inert atmosphere calcination furnace for calcination.

[0072] In step S3, the calcination temperature is controlled at 500℃ and the calcination time is 2 hours.

[0073] S4. Crush the calcined material to a density of D50 = 3μm using air jet milling.

[0074] S5. Place the pulverized material in a CVD furnace, introduce a mixture of propylene and nitrogen, and keep it at 700℃ for 5 hours.

[0075] In step S5, the volume ratio of the mixed gas is: propylene: nitrogen = 1.

[0076] S6. The CVD-coated material is sieved and demagnetized to obtain the silicon-based anode material.

[0077] In step S6, a 300-mesh sieve is used for sieving.

[0078] Example 4

[0079] The preparation method of silicon-based anode materials includes the following steps:

[0080] S1. Place the flexible substrate in the discharge chamber of the multi-target magnetron sputtering system;

[0081] In step S1, the flexible substrate is made of PE.

[0082] S2. Simultaneously turn on the silicon target and the graphite target to co-sputter nano-silicon and graphite carbon on the flexible substrate to form a film. The growth rate of nano-silicon and graphite carbon is controlled by controlling the sputtering power of the two targets. The growth rate is 2nm / s.

[0083] In step S2, the carbon content in the film formed by nano-silicon and graphite carbon is controlled at 20% and the silicon content is controlled at 80%; an intrinsic silicon target material is used.

[0084] S3. After the co-sputtered film thickness reaches 20μm, the coated sample containing the flexible substrate is placed in an inert atmosphere calcination furnace for calcination.

[0085] In step S3, the calcination temperature is controlled at 900℃ and the calcination time is 1 hour.

[0086] S4. Crush the calcined material to a density of D50 = 15μm using mechanical crushing.

[0087] S5. Place the pulverized material in a box furnace and keep it at 1000℃ for 1 hour;

[0088] In step S5, the ratio of crushed material to asphalt is 1:0.06.

[0089] S6. The CVD-coated material is sieved and demagnetized to obtain the silicon-based anode material.

[0090] In step S6, a 400-mesh sieve is used for sieving.

[0091] Example 5

[0092] The preparation method of silicon-based anode materials includes the following steps:

[0093] S1. Place the flexible substrate in the discharge chamber of the multi-target magnetron sputtering system;

[0094] In step S1, the flexible substrate is made of PMMA.

[0095] S2. Simultaneously turn on the silicon target and the graphite target to co-sputter nano-silicon and graphite carbon on the flexible substrate to form a film. The growth rate of nano-silicon and graphite carbon is controlled by controlling the sputtering power of the two targets. The growth rate is 4nm / s.

[0096] In step S2, the carbon content in the film formed by nano-silicon and graphite carbon is controlled at 30% and the silicon content is controlled at 70%; an intrinsic silicon target material is used.

[0097] S3. After the co-sputtered film thickness reaches 20μm, the coated sample containing the flexible substrate is placed in an inert atmosphere calcination furnace for calcination.

[0098] In step S3, the calcination temperature is controlled at 750℃ and the calcination time is 3 hours.

[0099] S4. Crush the calcined material to a density of D50 = 10 μm using mechanical crushing.

[0100] S5. Place the pulverized material in a CVD furnace, introduce a mixture of acetylene and nitrogen, and keep it at 800℃ for 4 hours.

[0101] In step S5, the volume ratio of the mixed gas is: acetylene: nitrogen = 0.6.

[0102] S6. The CVD-coated material is sieved and demagnetized to obtain the silicon-based anode material.

[0103] In step S6, a 400-mesh sieve is used for sieving.

[0104] Example capacity First effect Example 1 2500mAh / g 85％ Example 2 1750mAh / g 89％ Example 3 2400mAh / g 86％ Example 4 2100mAh / g 87.5％ Example 5 1850mAh / g 88.5％

[0105] In existing literature, Si / / C composite anode films were prepared using magnetron co-sputtering technology, achieving a capacity of 2000 mAh / g and an initial efficiency of 87%. These films were directly applied to lithium-ion battery anode sheets, exhibiting good cycle performance during actual cycling. However, film cracking occurred in the later stages of cycling. The method of this invention involves calcining the silicon-carbon co-sputtered film and then further coating it with a solid-phase or CVD vapor phase to obtain a powder material. This allows for uniform and complete coating of nano-silicon, avoiding the cycle deterioration problem caused by material cracking and exhibiting good cycle stability. The cycling bundle of the material prepared using the process in Example 2 is as follows... Figure 2 As shown.

[0106] This invention employs magnetron co-sputtering technology to achieve uniform composite formation of nano-silicon and carbon under vacuum conditions, followed by a solid-phase or gas-phase CVD coating process to completely coat the exposed nano-silicon. This method yields silicon-based anode materials with uniform nano-silicon and carbon composites, effectively controls the particle size of the nano-silicon, enhances process safety, and avoids the cracking problem that easily occurs when directly using silicon thin films as anodes.

Claims

1. A method for preparing silicon-based anode materials, characterized in that, Includes the following steps: S1. Place the flexible substrate in the discharge chamber of the multi-target magnetron sputtering system; S2. Simultaneously turn on the silicon target and the graphite target to co-sputter nano-silicon and graphite carbon on a flexible substrate and form a film of a certain thickness. S3. After the co-sputtered film thickness reaches 1-20 μm, the coated sample containing the flexible substrate is placed in an inert atmosphere calcination furnace for calcination. S4. Crush the calcined material to a density of D50 = 1-15 μm; S5. Mix the pulverized material with asphalt, and then place it in a calcining furnace for calcination. The calcination temperature is 500-1000℃ and the calcination time is 1-3h; or place it in a CVD furnace, introduce a mixture of organic gas and nitrogen, and keep it at 700-1000℃ for 1-5h. S6. The novel nano-silicon-based anode material is obtained by sieving and demagnetizing the material after solid-phase or gas-phase CVD coating.

2. The method for preparing the silicon-based anode material according to claim 1, characterized in that, In step S1, the flexible substrate material is one of PET, PI, PP, PE, PC, and PMMA.

3. The method for preparing the silicon-based anode material according to claim 1, characterized in that, In step S2, the silicon target is one of intrinsic silicon, P-type silicon target, N-type silicon target, or silicon suboxide target. The carbon content in the film formed by nano-silicon and graphite carbon is controlled at 10-50%, and the silicon content is controlled at 50-90%.

4. The method for preparing the silicon-based anode material according to claim 1, characterized in that, In step S3, the calcination temperature is controlled at 500–900℃, and the calcination time is 1–5 hours.

5. The method for preparing the silicon-based anode material according to claim 1, characterized in that, In step S5, the ratio of the crushed material to asphalt is 1:0.05 to 1:0.20; the volume ratio of the mixed gas is: acetylene: nitrogen = 0.2 to 1, and the organic gas is one of acetylene, methane, and propylene.

6. The method for preparing the silicon-based anode material according to claim 1, characterized in that, In step S6, a 300-400 mesh sieve is used for sieving.

7. A silicon-based anode material, characterized in that, It is prepared by any one of the preparation methods of claims 1-6.

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