Modification method for coating silicon-carbon composite negative electrode material interface with modified asphalt

Abstract

The invention relates to the technical field of lithium battery materials, and in particular relates to a modification method for coating a silicon-carbon composite negative electrode material interface with modified asphalt. The asphalt-coated silicon-carbon composite negative electrode material is subjected to interface modification by utilizing specially selected phenolic resin, so that the silicon-carbon composite negative electrode material with high rate performance and high first rate is prepared. And a compact nano carbon coating layer with low pore defect degree is formed, so that the defects such as cracks and holes on the surfaces of nano silicon and graphite can be effectively repaired, irreversible consumption of a large number of active lithium ions in the charging and discharging process of a battery is avoided, and irreversible reduction of the battery capacity is remarkably reduced. Therefore, the asphalt-coated silicon-carbon composite negative electrode material is subjected to interface modification by utilizing the mutual synergistic effect of the phenolic resin and the asphalt, the capacity diving condition during high-current charging and discharging of the battery is obviously delayed, and the rate capability and coulombic efficiency of the material are improved.

Description

technical field [0001] The invention relates to the technical field of lithium battery materials, in particular to a method for modifying the interface of a silicon-carbon composite negative electrode material coated with modified asphalt. Background technique [0002] With the rapid development of new energy vehicles and portable electronic digital products, the market demand for lithium-ion batteries with high energy density and high rate performance is increasingly urgent. The theoretical capacity of graphite, a traditional negative electrode material, is only 372mAh / g, which cannot meet the needs of lithium-ion batteries with high energy density and high rate performance. In order to further meet the needs of high-performance lithium-ion batteries, it is necessary to develop new anode materials with high rate performance and high first-time Coulombic efficiency. The theoretical capacity of silicon is as high as 4200mAh / g, which is more than ten times the theoretical cap...

AI Technical Summary

Problems solved by technology

[0003] Although the silicon-based negative electrode material has a high theoretical capacity, there are still technical barriers that need to be overcome in the actual use process. The main problems are: 1) The volume expansion after lithium intercalation reaches 400%, resulting in the structure of the silicon-based material being broken, pulverized, As a result, the electrode is deactivated; 2) The electronic conductivity is poor, resulting in serious polarization of silicon-based materials during high-current charging and discharging

However, due to the existence of a large number of micropores in amorphous carbon, its specific surface area increases significantly with the increase of the coating amount, resulting in the consumption of a large amount of lithium ions when forming a complete and dense SEI film on the surface of the material during the first charge and discharge process, resulting in lithium batteries. The irreversible capacity increases during the first charge and discharge, and the first Coulombic efficiency decreases significantly

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