Negative electrode active material for lithium ion secondary battery, method for producing the same, negative electrode, and battery

摘要

In the case where a silicon substance having a high theoretical capacity as a negative electrode active material for a lithium ion secondary battery is used as a negative electrode active material, such a negative electrode active material is provided that has a high initial battery capacity and suffers less deterioration in performance even when many cycles of charge and discharge are repeated. A lithium ion secondary battery using the negative electrode active material is provided. Silicon and copper (II) oxide, or silicon, metallic copper and water are pulverized and simultaneously mixed in a pulverization device, thereby providing a negative electrode active material that has good cycle characteristics and a large battery capacity.

主权项

1. A negative electrode active material for a lithium ion secondary battery, comprising silicon, copper and oxygen as major constitutional elements, the negative electrode active material for a lithium ion secondary battery, containing fine particles of silicon having an average crystallite diameter (Dx) measured by an X-ray diffractometry using a half width of the (111) plane of the silicon phase of 50 nm or less, the negative electrode active material having average elemental ratios measured by an enemy dispersive X-ray analysis in a measurement field of 200 μm×200 μm, expressed by molar ratios, Cu/(Si+Cu+O) of from 0.02 to 0.30 and O/(Si+Cu+O) of from 0.02 to 0.30.