Vacancy Modulating Co3Sn2S2 Topological Semimetal for Aqueous Zinc-Ion Batteries

Abstract

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<inf>3</inf>Sn<inf>2</inf>S<inf>2</inf> 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. Co<inf>3</inf>Sn<inf>1.8</inf>S<inf>2</inf> achieves a specific energy of 305 Wh kg⁻¹ (0.2 Ag⁻¹) and a specific power of 4900 Wkg⁻¹ (5 Ag⁻¹). Co<inf>3</inf>Sn<inf>1.8</inf>S<inf>2</inf> and Zn<inf>x</inf>Co<inf>3</inf>Sn<inf>1.8</inf>S<inf>2</inf> benefit from better conductivity at lower temperatures; the quasi-solid Co<inf>3</inf>Sn<inf>1.8</inf>S<inf>2</inf>//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.