Preparation method of micron silicon-carbon composite negative electrode material with long cycle life

Abstract

The invention belongs to the technical field of battery materials, and particularly relates to a preparation method of a micron silicon-carbon composite negative electrode material with long cycle life, the composite negative electrode material prepared by the method has a tough multistage buffer structure, micron silicon particles crushed in a cycle process can be stabilized internally, and a fresh surface exposed by cracking is protected; and the graphene compact network with high strength and high modulus on the outer layer can maintain the structural integrity of the internal silicon-carbon active particles in the compaction process to the greatest extent. Meanwhile, internal silicon-carbon active particles (SiMP(at)C) are tightly connected into a mechanical and electrical whole through a graphene network with a compactly contracted outer layer, so that the electrode structure is reinforced and toughened, and effective mechanical buffering and continuous and rapid electron transferare realized in the lithium de-intercalation and intercalation process.

Description

technical field [0001] The invention belongs to the technical field of battery materials, and in particular relates to a preparation method of a micron silicon-carbon composite negative electrode material with long cycle life. Background technique [0002] As a new generation of lithium-ion battery anode material, silicon has abundant reserves, and its theoretical lithium storage specific capacity is the highest among all alloyed lithium storage elements, so it has great potential to replace graphite as the anode material of commercial lithium-ion batteries. At this stage, relevant research on silicon anodes has achieved remarkable results. However, a large number of applications of nanotechnology, including the use of nano-silicon as the active material to construct electrode materials and nano-design of carbon structures, etc., reduce the tap density and electrode density of materials, thus restricting the improvement of the volume performance of silicon anodes. Micro-sil...

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Problems solved by technology

However, the ability of active particles to effectively buffer internal stress decreases rapidly as the size increases

Studies have shown that when the size of silicon active particles exceeds 150 nm, they will inevitably break into smaller nanoparticles during the charging and discharging process, which not only causes some active materials to lose electrical contact, but also increases the specific surface area of ​​the material. Exposing the fresh silicon surface makes the SEI film continue to grow repeatedly on the surface of the particle, seriously restricting its cycle stability

[0003] For high-content silicon anodes, especially micro-silicon anodes, the traditional single-stage buffer structure with surface coating combined with reserved space cannot effectively guarantee its cycle stability. This is because, on the one hand, the expansion of silicon is anisotropic, and for Micron-sized silicon particles with different sizes, it is difficult to precisely design the reserved space for each particle to buffer the expansion; on the other hand, the hollow structure with the reserved space is difficult to maintain its integrity during the compaction process of the pole piece

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