| 摘要 |
PROBLEM TO BE SOLVED: To provide a high capacity lithium secondary battery exhibiting excellent safety under extremely high temperatures, and having excellent storage characteristics.SOLUTION: The lithium secondary battery includes a positive electrode having a positive electrode mixture layer, containing a lithium-containing composite oxide containing lithium and a transition metal as a positive electrode active material, on one or both surfaces of a collector; a negative electrode having a negative electrode mixture layer, containing a composite of a material that contains Si and O as constituent elements (atomic ratio x of O to Si is 0.5≤x≤1.5) and a carbon material, and a graphite carbon material as a negative electrode active material, where the percentage content of the composite in the negative electrode active material is 1-20 mass%, on one or both surfaces of the collector; and a nonaqueous electrolyte containing 0.5-5 mass% of halogen-substituted cyclic carbonate. In a side surface of a battery case, a cleavage groove which cleaves when the pressure in the battery case exceeds a threshold is provided to intersect a diagonal in the side view from a wide surface. |
