Lithium ion battery pre-lithiated silicon-carbon multilayer composite negative electrode material and preparation method thereof

Abstract

The invention discloses a lithium ion battery pre-lithiated silicon-carbon multilayer composite negative electrode material and a preparation method thereof. The composite negative electrode materialcomprises an amorphous carbon matrix, pre-lithiated silicon monoxide particles and a graphene material, wherein the graphene material is uniformly coated on an outer surface of the pre-lithiated silicon monoxide to form composite particles, and the composite particles are uniformly dispersed in the amorphous carbon matrix. After the silicon monoxide is pre-lithiated, the first effect of the silicon-based negative electrode material is greatly improved, the graphene material is light in weight, high in strength and excellent in conductivity, so mechanical property and conductivity of the composite material are greatly improved, the amorphous carbon matrix plays a role in isolating electrolyte and preventing silicon from being in contact with the electrolyte to generate a large number of unstable SEI films, and experiments show that the composite negative electrode material prepared has characteristics of good mechanical property, high conductivity, high initial coulombic efficiency andstable cycle performance.

Description

technical field [0001] The invention relates to the technology in the field of electrochemistry, in particular to a lithium-ion battery pre-lithiated silicon-carbon multilayer composite negative electrode material and a preparation method thereof. Background technique [0002] Lithium-ion battery has many advantages such as high volume and mass energy density, high power density, long cycle life, high discharge voltage, low self-discharge rate, no memory effect, low environmental pollution, low cost, and wide operating temperature range. The most promising secondary energy storage battery. Lithium-ion batteries have shown broad application prospects in the fields of portable consumer electronics, new energy vehicles, aerospace and large-scale energy storage in daily life. With the development of lightweight and highly integrated equipment, the energy density, cycle life and safety performance of lithium-ion batteries need to be improved urgently, and one of the important st...

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Problems solved by technology

However, there are two key problems in the development of silicon anode materials: the volume change during the cycle is as high as 300% to 400%, causing the electrode to pulverize and fall off, and at the same time, a fresh surface is produced, which leads to the continuous growth of the SEI film, resulting in the continuous consumption of the electrolyte.

[0006] According to reports, there are five common silicon-carbon composite methods in the industry: 1. Carbon-coated nano-silicon (nano-Si@C): low cost, high initial Coulombic efficiency, but large volume expansion, long-term The cycle stability is poor, and the monomer capacity is generally 400-2000mAh / g

2. Carbon-coated silicon oxide (SiO@C): high cost, low volume expansion, very good long-term cycle stability, and generally low initial Coulombic efficiency

3. Carbon-coated silicon nanowire (Si nanowire / SS): the specific capacity and the first coulombic efficiency are both high, but it needs to cooperate with mature preconditioning technology to ensure long-term cycle stability, and there are certain difficulties in the process

The first Coulombic efficiency is generally high, but there are certain difficulties in the process, the preparation cost is high, and crystalline silicon is easy to precipitate during the carbonization process, so it is not suitable for large-scale production at present

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