Negative active material and preparation method thereof and secondary battery
The present application discloses a negative active material and a preparation method thereof and a secondary battery. The negative active material comprises: lithium pre-intercalated silicon-containing materials; and a polymer coating layer coated on an outer surface of each particle of the lithium pre-intercalated silicon-containing materials. The negative active material can improve the first coulombic efficiency of the secondary battery, inhibit the volume expansion of the secondary battery and improve the cycle performance of the secondary battery. The preparation method of the negative electrode plate is simple, environment-friendly, and suitable for mass production.
1. A secondary battery comprising a negative electrode plate, the negative electrode plate comprising a negative active material and a binder, the negative active material comprising:
lithium pre-intercalated silicon-containing materials; and
a polymer coating layer fully coated on an entire outer surface of each particle of the lithium pre-intercalated silicon-containing materials, a polymer in the polymer coating layer being one or more selected from a group consisting of polyamide and polyamide-imide;
a thickness of the polymer coating layer being 20 nm˜500 nm;
a material of the binder being different from the polymer in the polymer coating layer;
wherein,
a silicon-containing material of the lithium pre-intercalated silicon-containing materials is oxide of silicon;
a lithium intercalation amount of the silicon-containing material makes a theoretical charge capacity of the lithium pre-intercalated silicon-containing materials be no more than 60% of a theoretical charge capacity of the silicon-containing materials; and
a thickness expansion rate of the negative electrode plate of the secondary battery after 100 cycles is less than or equal to 45%.
2. The secondary battery according to claim 1 , wherein the lithium pre-intercalated silicon-containing materials are obtained by mixing silicon-containing materials and lithium powders.