Interface regulation of Cu-2 Se via Cu-Se-C bonding for superior lithium-ion batteries

Transition metal selenides have aroused great attention in recent years due to their high theoretical capacity. However, the huge volume fluctuation generated by conversion reaction during the charge/discharge process results in the significant electrochemical performance reduction. Herein, the carbon-regulated copper(I) selenide (Cu2Se@C) is designed to significantly promote the interface stability and ion diffusion for selenide electrodes. The systematic X-ray spectroscopies characterizations and density functional theory (DFT) simulations reveal that the Cu-Se-C bonding forming on the surface of Cu2Se not only improves the electronic conductivity of Cu2Se@C but also retards the volume change during electrochemical cycling, playing a pivotal role in interface regulation. Consequently, the storage kinetics of Cu2Se@C is mainly controlled by the capacitance process diverting from the ion diffusion-controlled process of Cu2Se. When employed this distinctive Cu2Se@C as anode active material in Li coin cell configuration, the ultrahigh specific capacity of 810.3 mA.h.g(-1) at 0.1 kg(-1) and the capacity retention of 83% after 1,500 cycles at 5 A.g(-1) is achieved, implying the best Cu-based Li+-storage capacity reported so far. This strategy of heterojunction combined with chemical bonding regulation opens up a potential way for the development of advanced electrodes for battery storage systems.

Automated summary

Transition metal selenides have received great attention due to their high theoretical capacity, but the fluctuation in volume during charge/discharge process leads to significant reduction in electrochemical performance. In this study, carbon-regulated copper(I) selenide (Cu2Se@C) is designed to enhance the stability and ion diffusion in selenide electrodes, resulting in improved storage kinetics. The experimental results show that the capacitance process plays a crucial role in the Cu2Se@C material.