Vacancy Modulating Co₃ Sn₂ S₂ 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 Co₃ Sn₂ S₂ cathode for AZIBs showing a discharge plateau around 1.5 V. By introducing Sn vacancies, extra redox peaks from the Sn⁴⁺ /Sn²⁺ transition appear, which leads to more Zn²⁺ transfer channels and active sites promoting charge-storage kinetics and Zn²⁺ storage capability. Co₃ Sn_1.8 S₂ achieves a specific energy of 305 Wh kg^-1 (0.2 Ag^-1 ) and a specific power of 4900 Wkg^-1 (5 Ag^-1 ). Co₃ Sn_1.8 S₂ and Zn_x Co₃ Sn_1.8 S₂ benefit from better conductivity at lower temperatures; the quasi-solid Co₃ Sn_1.8 S₂ //Zn battery delivers 126 mAh g^-1 (0.6 Ag^-1 ) at -30 °C and a cycling stability over 3000 cycles (2 Ag^-1 ) with 85 % capacity retention at -10 °C.