Study of the high-voltage spike in lithium/polymer electrolyte/pyrite rechargeable batteries

The natural mineral pyrite is a very promising cathode material for lithium batteries as a result of its abundance, low cost and the high theoretical specific energy of the Li/FeS₂ couple (1273 Wh/kg based on 4e/FeS₂). However, it was found that the first discharge of the Li/composite polymer or gel electrolyte/pyrite battery is accompanied by a high-voltage spike, which may cause instability of the cell. With the use of XPS, TGA and electrochemical analysis (dQ/dV curves), it was established that the capacity of the high-voltage dQ/dV peak depends strongly on impurities in the pyrite, on the surface area of the cathode material, alumina content of the cathode and on cell preheating time in the equilibrium state. The problem of high-voltage spike was solved by cathode modification.