コイン型リチウム一次電池用正極導電材の最適化とその評価

Abstract

In order to satisfy the social demand for miniaturization of electric device, coin type manganese dioxide Lithium primary batteries with small size and low cost are required. In the general manufacturing process, manganese dioxide as an active material is mixed with a conductive carbon black, followed by a wet granulation with a binder such as fluorocarbon polymer. As a common problem, increase in the amount of binder causes degradation of the battery performance, because it prevents conductive passes. On the other hand, reduction in binder decreases adhesive property of each material, leading to generate cracks or chips. So far, adhesive carbon black has been reported as a conductive material. This achieves reduction in the amount of binder, however, it may also cause degradation in battery capacity.In this study, expanded graphite, which shows better compatibility than the carbon black, was used as a conductive material. Effect of the size on the compatibility and the battery performance were evaluated experimentally. A coin type battery was prepared and a constant-resistance discharge and pulse tests were conducted. Based on the results, optimum formulation was determined for the positive electrode.