Vacancy Modulating Co Sn S Topological Semimetal for Aqueous Zinc-Ion Batteries.

Weyl semimetals (WSMs) with high electrical conductivity and suitable carrier density near the Fermi level are enticing candidates for aqueous Zn-ion batteries (AZIBs), meriting from topological surface states (TSSs). We propose a WSM Co Sn S cathode for AZIBs showing a discharge plateau around 1.5 V. By introducing Sn vacancies, extra redox peaks from the Sn /Sn transition appear, which leads to more Zn transfer channels and active sites promoting charge-storage kinetics and Zn storage capability. Co Sn S achieves a specific energy of 305 Wh kg (0.2 Ag ) and a specific power of 4900 Wkg (5 Ag ). Co Sn S and Zn Co Sn S benefit from better conductivity at lower temperatures; the quasi-solid Co Sn S //Zn battery delivers 126 mAh g (0.6 Ag ) at -30 °C and a cycling stability over 3000 cycles (2 Ag ) with 85 % capacity retention at -10 °C.