Preparation and application of in-situ polymerization coated modified silicon-based negative electrode material

Abstract

The invention discloses preparation and application of an in-situ polymerization coating modified silicon-based negative electrode material, the surface of a silicon-based material is coated with a composite coating layer of an inorganic matter and a polymer, and through the effect of a deep eutectic solvent, the silicon-based negative electrode material enables monomers of the polymer to be subjected to in-situ polymerization reaction on the surface of the silicon-based material to obtain a composite coating layer in which inorganic matters are uniformly distributed in the polymer; the inorganic matter is lithium salt, and the thickness of the composite coating layer is 5-15 nm. According to the composite coating layer, an organic-inorganic composite coating layer is constructed on the surface of the material in an in-situ polymerization manner of a polymeric monomer doped with an inorganic substance. According to the negative electrode material, in the initial lithiation / delithiation process, a layer of organic-inorganic composite artificial solid electrolyte interface (SEI) is formed in situ, the structural integrity in the lithium intercalation / delithiation process is maintained, the irreversible consumption of lithium ions is reduced due to the addition of the lithium-rich inorganic matter, and the first coulombic efficiency and the cycle stability of the negative electrode material are improved.

Description

technical field [0001] The invention relates to the field of electrochemical energy storage, in particular to the preparation and application of a silicon-based negative electrode material modified by in-situ polymerization and coating. Background technique [0002] With the rapid development of electric vehicles, energy storage power stations and portable electronic devices, the demand for energy density of power sources is increasing day by day, and high specific energy lithium-ion batteries have received more and more attention. The existing commercial lithium-ion battery system is difficult to meet the demand, the theoretical specific capacity of graphite negative electrode is low (372 mAh / g), and the specific capacity improvement space of positive electrode material is small. Therefore, it is urgent to find a new type of high specific capacity negative electrode material. The theoretical specific capacity of silicon is as high as 4200 mAh / g, and due to the advantages of...

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Problems solved by technology

Although many structural designs and optimizations have been carried out on silicon-based materials, they still face many problems in practical applications, such as poor electrical conductivity, poor cycle stability, and low first-time Coulombic efficiency.

[0003] In the existing technology, there are related studies on the coating of silicon materials with organic polymers, and on the improvement of the electrical properties of negative electrode materials by coating with inorganic compounds. However, due to the different coating methods and modification principles of the two, it is currently impossible to synthesize the two. The advantage of modification is to form a uniform and effective inorganic-organic composite coating layer on the surface of the silicon negative electrode material. The bulk phase of the silicon negative electrode material is not uniform, and the distribution of inorganic substances and organic polymers in the coating layer is uneven, which still cannot solve the problem of the negative electrode. The increase of inactive substances in materials and the volume expansion of negative electrode materials in the process of intercalation and extraction of lithium

[0004] In order to solve the above problems, researchers have provided a variety of ways, such as improving conductivity through carbon coating and metal doping on the surface of silicon-based materials; optimizing electrode structure design: nanoparticles, nanowires, porous materials, composite materials and surface coatings. In addition, the cycle stability is improved by optimizing the electrolyte formula, adding electrolyte additives, and optimizing the binder; the front-end pre-lithiation strategy is used to improve the first Coulombic efficiency of the silicon-based negative electrode material, but the above The methods all stay in the scope of single modification, the effect is limited, and the process is complicated

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