Construction of Se-doped carbon encapsulated Cu₂Se yolk-shell structure for long-life rechargeable aluminum batteries

Rechargeable aluminum batteries (RABs) are promising alternatives to lithium-ion batteries in large-scale energy storage applications owing to the abundance of their raw materials and high safety. However, achieving high energy density and long cycling life simultaneously holds great challenges for RABs, especially for high capacity transition metal selenide (TMS)-based positive materials suffering from structural collapse and dissolution in acidic ionic liquid electrolyte. Herein, Se-doped carbon encapsulated Cu₂Se with yolk-shell structure (YS/Se-C@Cu₂Se) is rationally constructed to address such issues. Electrochemical and spectroscopic analyses as well as density functional theory calculations show that the highly conductive Se-C shell enhances the electrochemical reaction kinetics of the electrode and provides strong adsorption for the soluble Cu and Se species. Benefiting from these merits, the optimal YS/Se-C@Cu₂Se cathode manifests a high specific capacity of 1024.2 mAh/g at 0.2 A/g, a superior rate capability of 240.5 mAh/g at 3.2 A/g, and a long-term cycling stability over 2500 cycles. This work offers a feasible approach to the design and construction of low-cost and efficient TMS-based positive materials for realizing practically usable RABs.