Vacancy Modulating Co₃Sn₂S₂ 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 Co₃Sn₂S₂ 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. Co₃Sn_1.8S₂ achieves a specific energy of 305 Wh kg⁻¹ (0.2 Ag⁻¹) and a specific power of 4900 Wkg⁻¹ (5 Ag⁻¹). Co₃Sn_1.8S₂ and ZnxCo₃Sn_1.8S₂ benefit from better conductivity at lower temperatures; the quasi-solid Co₃Sn_1.8S₂//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.