Graphite-silicon/silicon oxide-carbon composite material and preparation method and application thereof

Abstract

The invention discloses a graphite-silicon / silicon oxide-carbon composite material and a preparation method and application thereof. The preparation method comprises the following steps: carrying out ball milling treatment on graphite powder and nano silicon to obtain graphite-silicon / silicon oxide composite particles; dispersing the graphite-silicon / silicon oxide composite particles into an organic solvent, adding asphalt, heating, stirring and mixing to obtain a graphite-silicon / silicon oxide-asphalt composite material; the graphite-silicon / silicon oxide-asphalt composite material is subjected to pyrolysis treatment to obtain the graphite-silicon / silicon oxide-carbon composite material, the composite material is used as a negative electrode material for lithium ion electrons, and the obtained lithium ion battery has the characteristics of high specific discharge capacity, good charge-discharge performance, relatively high cycle stability and the like; the raw materials adopted in the preparation process of the composite material are cheap, the technological process is simple, implementation is easy, and the composite material is suitable for large-scale production.

Description

technical field [0001] The invention relates to a lithium ion battery negative electrode material, in particular to a graphite-silicon / silicon oxide-carbon composite material, a preparation method thereof and an application as a lithium ion battery negative electrode material; it belongs to the technical field of lithium ion batteries. Background technique [0002] With the continuous update and iteration of electric vehicles, wearable electronic devices, energy storage devices and other products, consumers' enthusiasm for products continues to rise, and the market demand for energy storage devices is also becoming more and more urgent and demanding. Lithium-ion batteries as Now the most widely used secondary battery, but its existing capacity, rate performance, safety, cycle performance and other factors do not all meet the needs of the higher market, to improve these conditions, the development of new lithium-ion battery anode materials is the key. The theoretical capacit...

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Problems solved by technology

[0003] However, Si negative electrode materials still face many problems during the charging and discharging process: 1) The material is pulverized, and the material will have a huge volume expansion during the charging and discharging process, thereby increasing the internal stress of the material. When the internal stress of the material exceeds a certain limit, it will cause the material Detached from the current collector, the Si particles detached from the current collector will lose their electrochemical activity and cannot participate in the alloying reaction of lithium ions in the battery, which will lead to a rapid decline in the cycle performance of the material.

However, when the Si material is in the discharge process, with the alloying of lithium and Si, the volume of the material expands, and the SEI film will form on the surface of the material. When lithium and Si are dealloyed, the volume of the material shrinks, and the SEI film on the surface of the material will Will be destroyed due to volume change

Repeatedly, it will cause the repeated formation of SEI film, which will lead to a large consumption of lithium ions and electrolyte, and reduce the Coulombic efficiency and cycle performance of the material.

3) The electrode design is difficult. Since the Si negative electrode material is accompanied by a huge change in volume during the charge and discharge process, the active material is separated from the current collector, resulting in a large amount of material deactivation during the charge and discharge process, and the negative electrode has a volume change throughout the process. , so the characteristics of these Si negative electrode materials should be considered in the design process of the full battery, which increases the difficulty of battery negative electrode design

[0004] Chinese patent (CN108565451A) discloses a preparation method of a silicon-carbon negative electrode material: silicon particles are coated with amorphous carbon and graphite, which improves the conductivity of the battery material and the cycle performance of the battery, but this method is still not very good Relief of volume expansion of nano-silicon during discharge

[0005] Chinese patent (CN106941164A) discloses a preparation method of a silicon-carbon negative electrode core-shell material: silicon particles are coated with amorphous carbon and graphene, which improves the conductivity of the battery material and the cycle performance of the battery to a certain extent. However, this method still cannot protect the pulverization of nano-silicon particles and the shedding of active materials in the case of high cycle times.

[0006] None of the methods mentioned above can solve the problem of rapid volume expansion of silicon materials during charging and discharging.

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