Conductive polymer armor strategy enables metal sulfides with super long-life sodium storage

Metal sulfide anode for sodium-ion batteries (SIBs) have attracted widespread attention for the merits of abundant resources, low cost and high capacity. Unfortunately, its practical application still subjects to the low electron conductivity, severe micro-volume deformation, and grievous polysulfide shuttle during cycling process, leading to rapid capacity attenuation and poor cyclic behavior. To address these issues, the designed Cu_yS/C microsphere anode is armored with polypyrrole (PPy) layer, which intrinsically holds high sodiophilicity and strong chemisorption capability for polysulfides. As the protective shell layer of Cu_yS/C anode, both the volume change and polysulfide shuttle effect are greatly suppressed, achieving excellent sodium storage performance. Briefly, Cu_xS/C@PPy anode delivers high reversible capacity of 300 mAh g^-1 after 3000 cycles at 5 A g^-1, and 257 mAh g^-1 after 30000 cycles at 20 A g^-1. When matched with the commercial AC cathode, the optimized dual-ion battery also exhibits stable sodium storage capacity of 274 mAh g⁻¹ after 4000 cycles at 5 A g^-1. This work demonstrates the positive effect of conductive polymer armor strategy on the performance improvement of metal sulfide anode, and provides new strategy for the design of organic-inorganic hybrid electrodes.