Composite anode material for lithium ion battery and preparation method thereof

Abstract

The invention belongs to the technical field of lithium ion batteries, in particular relates to a composite anode material for the lithium ion battery. The composite anode material comprises an anode active substance and a coating layer coated on the surface of the anode active substance, wherein the anode active substance can be Si, SiOx or silicon alloy, the coating layer is polymer which is of a reticular structure, and the mass percent of the coating layer accounts for 1-20% of the anode material. Compared with the prior art, the composite anode material has the advantages that the polymer which is of the reticular structure and used as the coating layer is coated on the surface of the active substance in a cross-linking manner, the coating layer has the electron conduction property and the ion conduction property, so that the situation that the lithium ions can be inserted into and separated from the anode active substance particles smoothly is ensured; furthermore, the coating layer is of the reticular structure and has good mechanical strength, and therefore, the integrality of the anode active substance particles can be kept in the electrochemical cycle process, the deformation of an anode strip is relieved, the electrochemical cycle performance of the lithium ion battery is improved and the service life of the lithium ion battery is prolonged.

Description

technical field [0001] The invention belongs to the technical field of lithium ion batteries, and more specifically, the invention relates to a composite anode material for lithium ion batteries and a preparation method thereof. Background technique [0002] At present, graphite is the main anode active material for commercial lithium-ion batteries. However, graphite has limited mass specific capacity and very little room for volume specific capacity improvement, which cannot meet the needs of future high-capacity and small-volume electronic devices. [0003] So far, through a lot of research on metal anodes, it has been found that the most promising materials for lithium-ion battery anodes are silicon and tin, which allow a maximum lithium intercalation of about 4 times that of graphite, Therefore, it has a high volume specific capacity. For example, Li 4.4 Si and Li 4.4 Sn, its theoretical gram capacity can be as high as 4200mA.h / g and 996mA.h / g respectively, and the th...

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Problems solved by technology

For example, the electrical contact between particles can be enhanced by nanosizing particles such as silicon and tin, thereby improving the cycle performance of the battery, but when the particles reach the nanometer level, they are particularly prone to agglomeration; The surface of the particles is coated with carbon (CN 1428880A) to improve the cycle performance of the battery, but this process has the disadvantages of long operating time, uneven mixing, high follow-up heat treatment temperature and high energy consumption; Coating the surface of particles such as tin and tin (CN 101740748 B, CN 103078094 A and CN 102723491 A), although these polymers ensure the conductivity of the material, they cannot guarantee the ion conductivity of the material, so during the electric cycle There is a huge polarization problem, and at the same time they do not take into account the mechanical strength of the polymer (mainly creep resistance and toughness), so they cannot withstand the shrinkage and expansion of the active material during the electrochemical cycle, resulting in the coating layer failure, and then expose the active material to the electrolyte and react with it, resulting in the loss of battery capacity and deterioration of cycle performance

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