si/siox/c composite negative electrode material, its preparation method and lithium ion battery

Abstract

The invention provides a Si / SiOx / C composite negative material. The Si / SiOx / C composite negative material comprises a porous silicon particle matrix loaded with SiOx particles and conductive carbon particles and amorphous carbon attached to an outer surface and an inner porous wall surface of the porous silicon particle matrix. The porous structure of the porous silicon particle matrix and the carbon structure of the amorphous carbon provide a space to the volume expansion of the silicon particles, so that a contact surface between a negative material and electrolyte is increased, lithium ionscan be rapidly exchanged on the contact surface, and the circulating stability of the lithium ion battery can be promoted. Meanwhile, the porous silicon particle substrate and the amorphous carbon are used as a supporting skeleton of the composite porous material, so that while the circulating stability of the composite negative material is maintained, the completeness of a electrode conductive network can be maintained, the advantages of the high lithium storage capacity of a silicon material can be sufficiently played, and the volume expansion effect of the composite negative material can be reduced; and therefore, the porous Si / SiOx / C composite negative material is high in reversible capacity and excellent in circulating performance.

Description

technical field [0001] The invention relates to the technical field of lithium ion batteries, in particular to a Si / SiOx / C composite negative electrode material, a preparation method thereof and a lithium ion battery. Background technique [0002] Among various lithium-ion battery anode materials, the theoretical specific capacity of graphite is only 372mAh / g, which cannot meet the requirement of high energy density. Silicon material has a high theoretical specific capacity (4200mAh / g), but it has a huge volume effect (>300%) during the charge-discharge cycle, which leads to the failure of active material particles and rapid capacity decay, making silicon negative electrodes practicality has been hindered. Although the theoretical specific capacity of SiOx material is smaller than that of pure silicon material, its volume effect is relatively small (about 150%) during the charging and discharging process of the battery. Studies have shown that if the silicon particles a...

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Problems solved by technology

[0003] At present, research in this area is mostly based on special structures such as silicon nanowires and hollow nano-silicon spheres. Although they all have excellent lithium intercalation properties, the preparation process is very complicated and difficult to scale production.

Porous silicon is also commonly prepared by electrochemical etching (for example: Chinese patent CN102134737) and metal-assisted chemical etching. The former needs to use a single crystal silicon wafer, and only a very thin layer of porous silicon can be prepared on the surface, which has high cost and low yield; The latter uses crystalline silicon powder, the yield is very low, and it also needs a long time chemical reaction, which consumes a lot of energy and is difficult to mass produce.

At the same time, the porous silicon material has a high expansion coefficient during the charge and discharge process, and the particle structure is easily destroyed, resulting in the detachment of the active material from the current collector and the decline in cycle performance.

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