Electrochemical characterization of non-stoichiometric Cu2Sx cathode for lithium batteries

Electrochemical performances of non-stoichiometric Cu2Sx (1.25 ≤ x ≤ 0.625) cathodes prepared by spray pyrolysis and followed annealing were investigated after coating on carbon fiber paper (CFP) and Cu foil current collectors. The chemical composition influence on the electrochemical properties of Cu2Sx was noticeably observed on a Cu foil current collector, especially at higher charge-discharge rates. Electrochemical impedance spectroscopy revealed that Cu/S ≈ 3.2 M ratio electrode shows lower interfacial charge transfer resistance (Rct) after 5 cycles at 0.1 C compared with Cu/S ≈ 1.6 M ratio electrode on both current collectors. Accordingly, the electrode with Cu/S ≈ 3.2 M ratio showed the highest discharge capacity of 350 mAh g−1 at 5 C on a Cu foil current collector. The excess of Cu in Cu2Sx enhanced electrode utilization with the cycle number and facilitated fast charge transfer.