Preparation method of lithium battery anode material

Abstract

The invention discloses a preparation method of a lithium battery negative electrode material, and belongs to the technical field of new energy. The lithium battery negative electrode material prepared by the invention is prepared by compounding a liquid lithium alloy and a silicon-carbon composite material according to a mass ratio of 1: 3-1: 20. The pores of the silicon-carbon composite materialare dispersedly filled with the liquid lithium alloy, and the liquid lithium alloy is adopted to replace a lithium source embedded in a conventional negative electrode, so the formation of lithium dendrites and the existence of the liquid lithium alloy in the long-term charge-discharge cycle process of the battery can be effectively avoided, and the expansion of the silicon-carbon negative electrode in the charge-discharge cycle process can be effectively buffered. By controlling the types of elements in the lithium alloy and controlling the preparation process of the silicon-carbon compositematerial, the silicon-carbon composite material can be effectively filled with the liquid lithium alloy to form a gel-like structure.

Description

technical field [0001] The invention discloses a preparation method of a negative electrode material of a lithium battery, belonging to the technical field of new energy sources. Background technique [0002] Among the many optional negative electrode materials for lithium-ion batteries, silicon is one of the most likely materials to replace commercial graphite negative electrodes. The reasons are as follows: (1) Silicon has the highest theoretical mass specific capacity among many optional negative electrodes ( 4200mAh / g); (2) The discharge platform of the silicon negative electrode is around 0.4V, which has found a balance in maintaining a normal open circuit voltage and avoiding bad lithium plating; (3) The reserves of silicon are sufficient (the crustal content ranks second) , low economic cost, environmentally friendly and non-toxic. [0003] However, there are still big problems with silicon as the negative electrode of lithium-ion batteries. In the alloy phase Li4.4...

AI Technical Summary

Problems solved by technology

[0003] However, there are still big problems with silicon as the negative electrode of lithium-ion batteries.

In the alloy phase Li4.4Si and other alloy chimeras will produce extremely obvious volume expansion (more than 360%) during the formation process, and form huge stress when lithium is intercalated / extracted, which will cause the following consequences: (1) In the cycle of delithiation / intercalation of lithium, the electrode structure will gradually shatter under the action of stress, which is also a problem in alloyed negative electrodes; (2) Under the action of interfacial stress, the active material splits from the current collector and is no longer effective ; (3) Due to volume expansion and internal stress, the structure of the motor is constantly being destroyed, and new interfaces are constantly exposed to the electrolyte, which will cause the solid electrolyte membrane (SEI) to repeat the cycle of generation-destruction-reformation. of lithium ions are continuously consumed

The above process will cause the collapse of the motor structure and the attenuation of the battery capacity.

In addition to the huge volume expansion, due to the poor conductivity of silicon, it not only affects the transmission efficiency of electron ions, but also causes a large interface impedance.