abstract |
In a lithium ion battery having a cleavage valve for releasing gas in response to an increase in internal pressure and having a discharge capacity X of 30 Ah or more and less than 100 Ah, the positive electrode mixture is composed of layered lithium / nickel / manganese / cobalt composite oxide (NMC). It contains a mixed active material with spinel type lithium manganese oxide (sp-Mn). The density of the positive electrode mixture is 2.4 to 2.7 g / cm 3 , the coating amount of the positive electrode mixture is 175 to 250 g / m 2 , and the weight ratio (NMC / sp-Mn) is Y , Y <−0.0062X + 1.05 is satisfied. The operating pressure of the cleavage valve is 1.0 to 5.0 MPa when the discharge capacity X is 30 Ah or more and 40 Ah or less, and 1.0 to 5.0 MPa when the discharge capacity X exceeds 40 Ah and 80 Ah or less. When it is 4.0 MPa and the discharge capacity X exceeds 80 Ah and less than 100 Ah, it is 1.0 to 3.0 MPa. |