Facile synthesis of binder-free CuSe as a long-cycling anode for sodium batteries: Self-healing metal selenide anode for sodium batteries

Owing to their high capacity and electrical conductivity, transition metal selenides have attracted attention as anodes for sodium batteries. In this study, CuSe was synthesised using a simple and scalable process that involved heating Se powder on a Cu current collector at 140 °C for 5 h. Furthermore, CuSe was used as an anode without a binder or conducting agent, exhibiting a stable capacity during long cycles. The initial capacity of the CuSe electrode was 289 mAh g−1 at 15 A g−1, which reduced to 89.2 % of the initial value after 10,000 cycles. During cycling, the CuSe particles were cleaved and pulverised into nanoparticles, which subsequently agglomerated to form a porous structure without capacity loss. This phenomenon is known as self-healing. Because pulverised CuSe exhibits optimal cycling properties, pulverisation does not cause poor cycling and can be overcome through self-healing. This study is the first to investigate the self-healing properties of metal selenides. Additionally, the Na3V2(PO4)3/CuSe full cell exhibited a good cyclability of 151 mAh g−1 after 2000 cycles. The superior properties of CuSe in conjunction with an ether-type electrolyte provide deep insights for the development of long-lasting cycling batteries.