| 摘要 |
PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery that is long in life while the low electron conduction of a positive electrode using olivine type lithium iron phosphate (LiFePO) as a positive electrode active material is improved.SOLUTION: In a lithium ion battery incorporating positive/negative electrodes and a separator in a battery container and including an electrolyte in the battery container, olivine type lithium iron phosphate (LiFePO) is contained in a positive electrode active material, a conductive layer having a thickness of 1-5 μm is formed on a positive electrode collector, the density of a positive electrode active material layer is 1.90-2.30 g/cmor the volume porosity in a positive electrode active material layer is 20-50%, the film thickness of the positive electrode active material layer is 40-200 μm, and furthermore a conductive assistant is contained within a range of 2 mass% or more and 10 mass% or less in the positive electrode active material layer. |
