| 摘要 |
PROBLEM TO BE SOLVED: To provide a negative electrode for secondary battery having excellent adhesiveness of a collector and the carbon material by forming a coating layer, which contacts with a negative electrode collector, of two layers or more, and coating a lower layer with the carbon material having a small specific surface area. and forming the thickness in a specified range. SOLUTION: As a carbon material to be coated on a surface of a negative electrode collector 20 for lithium ion secondary battery, the carbon material having a low specific surface area at 2 m<2> /g or less, especially the fiber-like carbon having a specific surface area at 1-2 m<2> /g is used for a lower layer, and thickness of the coating layer is set at 20-100 μm. An upper layer is coated with the carbon material having a large specific surface area and a high discharging capacity. In comparison with one-layer coating of a collector surface, besides the binder already exists in the lower layer, since the coating layer of the lower surface has a larger contact area in comparison with the surface area of the collector, quantity of the binder to be required for coating of the upper layer is little, and quantity of the binder for all coating layers can be reduced than that of the one-layer coating, and quantity of the binder can be set at 10 wt.% or less in relation to the total weight of the all coating layer, and in this condition, adhesiveness and discharging capacity are improved. |
