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. Co3Sn1.8S2 achieves a specific energy of 305 Wh kg−1 (0.2 Ag−1) and a specific power of 4900 Wkg−1 (5 Ag−1). Co3Sn1.8S2 and ZnxCo3Sn1.8S2 benefit from better conductivity at lower temperatures; the quasi-solid Co3Sn1.8S2//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.