High performance stoichiometric Cu2S cathode on carbon fiber current collector for lithium batteries

In this study, stoichiometric Cu2S with monoclinic crystal structure with space group P21/c was prepared via spray pyrolysis with followed heat treatment. Its electrochemical properties were investigated after coating on a carbon fiber paper (CFP) current collector and cycling at various cut-off voltages. The reversible stable capacity of about 330 mAh g−1 (98% of its theoretical capacity) exhibited by the cell for 20 cycles at 0.1C and slightly dropped to 311 mAh g−1 after 50 cycles. At higher 1C rate, a discharge capacity of 280 mAh g−1 was retained for 100 cycles with approximately 100% Coulombic efficiency between 1.0-3.0 V. While the gradual capacity decrease is observed with the increase of the discharge cut-off voltage to avoid solid electrolyte interface (SEI) formation during the 1st discharge. The cells showed capacities of 307 and 280 mAh g−1 after the 5th cycle at 0.1C when cycled between 1.1-3.0 V and 1.2-3.0 V, respectively, due to the lowered lithium ion diffusion. Ex situ XRD analysis of the recovered electrodes after cycling with near theoretical capacity allowed discussing the actual reaction mechanism of stoichiometric Cu2S with Li+.