Cu2S is considered as one of the potential anode paradigms for advanced rechargeable batteries because of its high theoretical capacity (∼335 mAh·g-1), high and flat charge/discharge voltage plateaus (∼1.7 V vs Li+/Li), stable cycling performance, and its elemental abundance. However, many studies have shown that Cu2S exhibits a dramatic capacity fade in carbonate-based electrolytes, which has precluded its commercialization when paired with high voltage cathodes in state-of-the-art lithium ion batteries. Here, we report on a fundamental mechanistic study of the electrochemical processes of Cu2S in both ether- and carbonate-based electrolytes employing operando synchrotron X-ray methods. Based on our findings, we developed a Cu2S/C composite material that suppresses its failure mechanism in carbonate-based electrolytes and further demonstrated its feasibility in lithium ion full cells for the first time. Our experiment provides the basis for the utilization of Cu2S in industrial-scale applications for large-scale electrical energy storage.
Keywords: Cu2S; X-ray absorption spectroscopy; anode; electrolytes; lithium ion battery; synchrotron X-ray.