A Stable Copper-Organosulfide Cathode for Rechargeable Lithium Batteries.

Organosulfides have been considered as promising alternative materials for sulfur-based cathodes due to their strong structural tailorability, abundant redox-active sites. However, general organosulfides suffer from low conductivity, high solubility in electrolyte, which leads to low active materials utilization, severe shuttle effects, and short cycling life. Metal-organosulfide complexes, which can be formed by reactions between thiol groups in aromatic organosulfides and transition metal ions, feature π-d conjugated frameworks with improved conductivity and are insoluble in general electrolytes. These features offer a possible strategy to overcome bottlenecks of organosulfides at the molecular level. Herein, a small molecule PhSCu is selected as the cathode material for rechargeable lithium battery and the electrochemical behaviors were explored systematically. X-ray photoelectron spectroscopy (XPS), high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (HPLC-QTof-MS), and Fourier transform infrared spectroscopy (FTIR) analyses reveal the reversible valence transition of Cu/Cu+ accompanied by reversible Cu─S bond cleavage and reformation during charge and discharge processes. The Li||PhSCu cell delivers an initial capacity of 152.6 mAh g-1 and retains a capacity of 117.7 mAh g-1 after 140 cycles. The study aims to provide a guidance for addressing the dissolution issue of organosufide cathodes in alkali metal batteries.