| abstract |
The present invention provides a lithium ion secondary battery containing a positive electrode, a negative electrode, and a nonaqueous electrolyte, wherein: the negative electrode contains, as a negative electrode active material, a graphite material having rhombohedral crystals at an abundance ratio of 5% or less; and the nonaqueous electrolyte contains an ionic liquid. This lithium ion secondary battery has excellent ultra-long-term cycle properties and high-current load properties (direct-current resistance properties) and is useful in the automobile field etc. as a large battery for a battery electric vehicle (BEV) or hybrid electric vehicle (HEV), for example. |