Silicon-carbon composite material and preparation method thereof and application thereof in lithium ion battery

Abstract

The invention relates to the battery field, and in particular relates to a silicon-carbon composite material and a preparation method thereof and application thereof in lithium ion battery. The following problems exist in the application of silicon-based materials in the lithium ion battery: 1. first coulombic efficiency of the lithium ion battery is low; 2, cycle life of the lithium ion battery is short; 3, the rate performance is poor; 4, the materials are low in production efficiency, and not conducive to large-scale industrial production. In order to solve the problems, the silicon-carbon composite material is provided, secondary-particles comprise a plurality of first particles containing core-shell structures, the core-shell structure comprises a carbon shell layer and silicon core particles which are completely wrapped by the carbon shell layer, and a gap is between the carbon shell layer and the silicon core particles. The preparation method of the silicon-carbon composite material and the application of the silicon-carbon composite material in the lithium ion battery are also provided.

Description

technical field

[0001] The invention relates to the field of batteries, in particular to a silicon-carbon composite material, a preparation method thereof and an application in lithium ion batteries. Background technique

[0002] At present, the anode material of commercial lithium-ion batteries is mainly graphite, but due to the low theoretical capacity (372mAh / g), the further improvement of the energy density of lithium-ion batteries is limited.

[0003] Among many new lithium-ion battery anode materials, silicon-based anode materials have the advantage of high capacity that other anode materials cannot match (Li22Si5, theoretical lithium storage capacity 4200mAh / g), which is more than 11 times the theoretical capacity of current commercial carbon anode materials. However, silicon-based materials have poor conductivity, and at the same time, they have a serious volume effect in the process of intercalating and removing lithium, with a volume change rate of about 400%, whic...

Examples

Embodiment 1

[0053] Take 400g of silicon powder with a D50 of 1.5 μm and put it into a rotary tube furnace, and heat it at 1000°C for 3 hours in a pure oxygen atmosphere to obtain particles whose outer layer is silicon dioxide and the inner core is silicon, and the oxygen content is about 42%. Can be labeled as Si@SiO2. During the oxidation process, the oxygen flow rate is kept at 160ml / min, and the furnace tube keeps rotating to ensure that the silicon powder is in full contact with oxygen and oxidized evenly. Dissolve 240g of sucrose in 2360g of water, take 350g of oxidized silicon powder, slowly add it to the sucrose aqueous solution, and disperse with mechanical stirring at a speed of 1300rpm for 1 hour to obtain a uniform slurry with a solid content of about 20%. The obtained Si@SiO2 sucrose slurry was spray-dried with spray drying equipment, the inlet air temperature was 150°C, the outlet temperature was 105°C, the rotary atomizing nozzle speed was 400Hz, and the feed rate was 120g / m...

Embodiment 2

[0058] Take 200 g of spherical silicon powder with a D50 of 0.05 μm and put it into a rotary tube furnace, and heat it in an air atmosphere at 900 ° C for 2 hours to obtain Si@SiO2 powder with an oxygen content of about 39%. Dissolve 180g of glucose in 1600g of water, take 220g of oxidized silicon powder, slowly add it to the aqueous glucose solution, and disperse for 1 hour at a speed of 1300rpm with mechanical stirring to obtain a uniform slurry with a solid content of about 20%. The obtained Si@SiO2 glucose slurry was spray-dried with spray drying equipment, the inlet air temperature was 210°C, the outlet temperature was 110°C, the rotary atomizing nozzle speed was 400Hz, and the feed rate was 70g / min. Spray drying to obtain spherical glucose-encapsulated Si@SiO2 dry powder is aggregated into secondary particles, and the D50 is about 16 μm. The spray-dried dry powder was heated at 900° C. for 3 hours in an argon inert atmosphere to obtain Si@SiO2@C powder. Take 5g of the a...

Embodiment 3

[0061] Take 4kg of silicon powder with a D50 of 2 μm, mix it with deionized water to make a slurry with a solid content of 50%, and perform wet grinding with a sand mill for 5 hours to obtain a submicron silicon slurry with a D50 of about 0.7 μm. Dilute the silicon slurry obtained by sand grinding to a solid content of about 30%, and stir in a reactor at a constant temperature of 80°C for 36 hours to make the silicon particles react with water and form a silicon dioxide layer on the surface. During the constant temperature oxidation process, add water to the reaction kettle properly to prevent the water from evaporating to dryness. Finally, a Si@SiO2 slurry with a solid content of 32.1% was obtained, and the solid Si@SiO2 oxygen content was about 17%. Take 12.7kg of the above slurry, dissolve 350g of sucrose and 200g of glucose in deionized water and mix evenly, then add deionized water so that the solid content of the final slurry is about 25%. The obtained Si@SiO2, glucose,...

technical field

[0001] The invention relates to the field of batteries, in particular to a silicon-carbon composite material, a preparation method thereof and an application in lithium ion batteries. Background technique

[0002] At present, the anode material of commercial lithium-ion batteries is mainly graphite, but due to the low theoretical capacity (372mAh / g), the further improvement of the energy density of lithium-ion batteries is limited.

[0003] Among many new lithium-ion battery anode materials, silicon-based anode materials have the advantage of high capacity that other anode materials cannot match (Li22Si5, theoretical lithium storage capacity 4200mAh / g), which is more than 11 times the theoretical capacity of current commercial carbon anode materials. However, silicon-based materials have poor conductivity, and at the same time, they have a serious volume effect in the process of intercalating and removing lithium, with a volume change rate of about 400%, whic...

Examples

Embodiment 1

[0053] Take 400g of silicon powder with a D50 of 1.5 μm and put it into a rotary tube furnace, and heat it at 1000°C for 3 hours in a pure oxygen atmosphere to obtain particles whose outer layer is silicon dioxide and the inner core is silicon, and the oxygen content is about 42%. Can be labeled as Si@SiO2. During the oxidation process, the oxygen flow rate is kept at 160ml / min, and the furnace tube keeps rotating to ensure that the silicon powder is in full contact with oxygen and oxidized evenly. Dissolve 240g of sucrose in 2360g of water, take 350g of oxidized silicon powder, slowly add it to the sucrose aqueous solution, and disperse with mechanical stirring at a speed of 1300rpm for 1 hour to obtain a uniform slurry with a solid content of about 20%. The obtained Si@SiO2 sucrose slurry was spray-dried with spray drying equipment, the inlet air temperature was 150°C, the outlet temperature was 105°C, the rotary atomizing nozzle speed was 400Hz, and the feed rate was 120g / m...

Embodiment 2

[0058] Take 200 g of spherical silicon powder with a D50 of 0.05 μm and put it into a rotary tube furnace, and heat it in an air atmosphere at 900 ° C for 2 hours to obtain Si@SiO2 powder with an oxygen content of about 39%. Dissolve 180g of glucose in 1600g of water, take 220g of oxidized silicon powder, slowly add it to the aqueous glucose solution, and disperse for 1 hour at a speed of 1300rpm with mechanical stirring to obtain a uniform slurry with a solid content of about 20%. The obtained Si@SiO2 glucose slurry was spray-dried with spray drying equipment, the inlet air temperature was 210°C, the outlet temperature was 110°C, the rotary atomizing nozzle speed was 400Hz, and the feed rate was 70g / min. Spray drying to obtain spherical glucose-encapsulated Si@SiO2 dry powder is aggregated into secondary particles, and the D50 is about 16 μm. The spray-dried dry powder was heated at 900° C. for 3 hours in an argon inert atmosphere to obtain Si@SiO2@C powder. Take 5g of the a...

Embodiment 3

[0061] Take 4kg of silicon powder with a D50 of 2 μm, mix it with deionized water to make a slurry with a solid content of 50%, and perform wet grinding with a sand mill for 5 hours to obtain a submicron silicon slurry with a D50 of about 0.7 μm. Dilute the silicon slurry obtained by sand grinding to a solid content of about 30%, and stir in a reactor at a constant temperature of 80°C for 36 hours to make the silicon particles react with water and form a silicon dioxide layer on the surface. During the constant temperature oxidation process, add water to the reaction kettle properly to prevent the water from evaporating to dryness. Finally, a Si@SiO2 slurry with a solid content of 32.1% was obtained, and the solid Si@SiO2 oxygen content was about 17%. Take 12.7kg of the above slurry, dissolve 350g of sucrose and 200g of glucose in deionized water and mix evenly, then add deionized water so that the solid content of the final slurry is about 25%. The obtained Si@SiO2, glucose,...

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