Long-Cycling-Life Sodium-Ion Battery Using Binary Metal Sulfide Hybrid Nanocages as Anode

Due to the relatively high capacity and lower cost, transition metal sulfides (TMS) as anode show promising potential in sodium-ion batteries (SIBs). Herein, a binary metal sulfide hybrid consisting of carbon encapsulated CoS/Cu₂ S nanocages (CoS/Cu₂ S@C-NC) is constructed. The interlocked hetero-architecture filled with conductive carbon accelerates the Na⁺ /e^- transfer, thus leading to improved electrochemical kinetics. Also the protective carbon layer can provide better volume accommondation upon charging/discharging. As a result, the battery with CoS/Cu₂ S@C-NC as anode displays a high capacity of 435.3 mAh g^-1 after 1000 cycles at 2.0 A g^-1 (≈3.4 C). Under a higher rate of 10.0 A g^-1 (≈17 C), a capacity of as high as 347.2 mAh g^-1 is still remained after long 2300 cycles. The capacity decay per cycle is only 0.017%. The battery also exhibits a better temperature tolerance at 50 and -5 °C. A low internal impedance analyzed by X-ray diffraction patterns and galvanostatic intermittent titration technique, narrow band gap, and high density of states obtained by first-principle calculations of the binary sulfides, ensure the rapid Na⁺ /e^- transport. The long-cycling-life SIB using binary metal sulfide hybrid nanocages as anode shows promising applications in versatile electronic devices.