TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Battery: In the battery, each of the sandwiching members of the positive electrode insulating cover (25) and the negative electrode insulating cover (26) comprises a rectangular thick portion provided on each of the first and second sidewalls facing each other. The battery further comprises a rectangular protruding portion provided on the back surface member, where the protruding portion is located between the thick portions, and a length from the back surface member to a surface opposite is less than a width of the sidewall of the U-shaped member. The protruding portion comprises a penetrating hole. The first and second sidewalls, which face each other, of the U-shaped member of each of the positive electrode insulating cover (25) and the negative electrode insulating cover (26) are bent outwardly, each of the sandwiching members of the positive electrode insulating cover (25) and the negative electrode insulating cover (26) comprises bent sidewalls. Each of the sandwiching members of the positive electrode insulating cover (25) and the negative electrode insulating cover (26) comprises bent sidewalls and a rectangular protruding portion provided on the back surface member, and the protruding portion is located between the bent sidewalls, and a length from the back surface member to a surface opposite is less than a width of the sidewall of the U-shaped member. The U-shaped member of each of the positive electrode insulating cover (25) and the negative electrode insulating cover (26) comprises an extending portion that extends from a bent portion in a direction opposite to the back surface member. Extending portion comprises a channel groove that extends in parallel with the extending portion. Each of the sandwiching members of the positive electrode insulating cover (32) and the negative electrode insulating cover (33) comprises: a rectangular thick portion provided on each of the first and second sidewalls facing each other. The U-shaped member of each of the positive electrode insulating cover (32) and the negative electrode insulating cover (33) comprises an extending portion that extends from a bent portion in a direction opposite to the back surface member.