cobalt to the non aqueous electrolyte and the decomposition of the non aqueous electrolyte can be prevented in addition to this the lithium phosphate contained in the positive electrode serves to inhibit the reaction between the different elements mg al zr containing lithium cobalt oxide and the non aqueous electrolyte and thereby inhibit the elution of the positive electrode active material cobalt to the non aqueous electrolyte and the decomposition of the non aqueous electrolyte is inhibited as a result of this the lithium phosphate and the different elements operate synergistically so that the elution of the cobalt and the decomposition of the non aqueous electrolyte are inhibited effectively on the other hand when either or both of the features described above is lacked the elution of the cobalt and the decomposition of the non aqueous electrolyte cannot be inhibited sufficiently also it can be seen from examples 1 7 that when the amount of the lithium phosphate added to the positive electrode was less than 0 01 mass the elution of the cobalt and the generation of gas caused by the decomposition of the non aqueous electrolyte cannot be inhibited sufficiently cf example 2 while on the other hand when the amount of the lithium phosphate added to the positive electrode was more than 5 mass reduction in discharge capacity is incurred cf example 7 this is probably due to the following operations.