A silicon-based negative electrode material and its preparation method and use

Abstract

The invention relates to a silicon-based negative electrode material and its preparation method and application. The silicon-based negative electrode material includes a silicon-based core and a shell covering its surface. The shell includes nitrogen-doped graphene, nitrogen-doped The first coating composed of hydrogen-containing lithium titanium oxide compound and nitrogen-doped hexagonal tungsten oxide compound and the second coating composed of mesoporous carbon layer, the preparation method comprises the following steps: (1) Disperse the silicon-based material and the first cladding in a solvent to obtain a dispersion, and then spray dry to obtain an inner core material; (2) disperse the inner core material in the triblock copolymer, amino alcohol and step (1) in (3) adding dopamine to the dispersion of step (3) to carry out a polymerization reaction, and then carbonizing under an inert atmosphere to obtain the silicon-based negative electrode material; the structure of the silicon-based negative electrode material of the present invention And cycle stability is significantly improved, and the cycle performance of silicon-based negative electrode materials is also significantly improved.

Description

technical field [0001] The invention belongs to the field of lithium ion batteries, and relates to a silicon-based negative electrode material and a preparation method and application thereof. Background technique [0002] Lithium-ion battery has become an ideal portable battery due to its high working voltage, light weight, small self-discharge, long cycle life, no memory effect, no environmental pollution and good safety performance. Si has a high lithium intercalation capacity, up to 4200mAh·g -1 , but in the process of lithium deintercalation of Si, the volume effect is as high as 300%, so that the lattice structure of Si collapses, the Si particles are pulverized, and the active material is separated from the current collector, resulting in a rapid capacity decay during the cycle. This hinders the practical application of Si as the negative electrode of lithium-ion batteries. [0003] CN105118974A discloses a silicon-based negative electrode material, which is a carbo...

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Problems solved by technology

Si has a high lithium intercalation capacity, up to 4200mAh·g -1 , but in the process of lithium deintercalation of Si, the volume effect is as high as 300%, so that the lattice structure of Si collapses, the Si particles are pulverized, and the active material is separated from the current collector, resulting in a rapid capacity decay during the cycle. This prevents Si from being put into practical application as the negative electrode of lithium-ion batteries.

[0003] CN105118974A discloses a silicon-based negative electrode material, which is a carbon-coated silicon / carbon nanofiber, which includes: carbon nanofibers loaded with silicon nanoparticles and silicon nanoparticles exposed on the surface of carbon nanofibers The carbon coating layer with secondary protective effect, its preparation method comprises the following steps: (1) Electrospinning: polyacrylonitrile, silicon nanoparticles are mixed and dissolved in N-N dimethylformamide solvent, after stirring and ultrasonic dispersion Obtain uniformly dispersed electrospinning solution, carry out electrospinning with gained electrospinning solution, obtain silicon / polyacrylonitrile nanofiber; (2) carbonization: the silicon / polyacrylonitrile nanofiber of step (1) gained is in air atmosphere (3) impregnation sucrose coating: impregnate the silicon / carbon nanofibers obtained in step (2) into a sucrose solution, and then take them out in the air Dry to obtain sucrose-coated silicon / carbon nanofibers; (4) secondary carbonization: carbonize the sucrose-coated silicon / carbon nanofibers obtained in step (3) in an argon atmosphere to obtain carbon-coated silicon / carbon nanofibers; The preparation process of the method described in this scheme is complicated, and the performance improvement is insufficient

The disadvantage is that LiH is flammable and explosive in contact with water, which has great safety hazards and is not easy to realize large-scale industrial production.

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