LITHIUM ION SECONDARY BATTERY

摘要

Provided is a lithium ion secondary battery which has excellent heat resistance, while being suppressed in the formation of lithium dendrite. The present invention relates to a secondary battery which comprises an electrode element containing a positive electrode, a negative electrode and a separator, and which is characterized in that: the negative electrode contains (a) a carbon material that is capable of absorbing and desorbing lithium ions and (b) a negative electrode active material containing an oxide that is capable of absorbing and desorbing lithium ions; and the separator contains 50% by mass or more of a nonwoven fabric that has a thermal melting or thermal decomposition temperature of 160°C or more.