Patent ID: 9525171
Filing Date: 2016-12-20
CPC Classification: H01M,Y02E,Y02P,Y02T

Claim Text:
1. A lithium ion secondary battery comprising a positive electrode, a negative electrode and a nonaqueous electrolyte solution, wherein the positive electrode comprises, as a positive electrode active material, a lithium-transition metal composite oxide having a layered structure, the lithium-transition metal composite oxide is represented by general formula (I): where M′ is at least one selected from among zirconium and aluminum; x satisfies the condition 1.0≦x≦1.25; a, b, c, d and e satisfy conditions a+b+c+d+e=1 and 0.001≦(d+e)≦0.02; at least one of a, b and c is larger than 0; d>0; and e>0, the lithium-transition metal composite oxide comprises tungsten in an amount of 0.50 to 1.00 mol % and zirconium in an amount of 0.20 to 0.50 mol %, and the positive electrode active material exhibits a tungsten elution of 0.020 mmol per gram or less, the tungsten elution being the amount of tungsten eluted into a filtrate in which a suspension of the positive electrode active material in water is filtered, as measured by inductively coupled plasma mass spectrometry (ICP-MS).