An energy-efficient tellurium electrode enabled by a CsTeI perovskite structure for durable aqueous Zn-Te batteries

Tellurium (Te) is a promising high-capacity electrode material for aqueous zinc-ion batteries, capable of multi-electron redox reactions. However, the inherent hydrolysis of oxidized Te 4+ exhibits significant polarization during redox, rendering it highly coupled with water in the electrolyte. This study presents a comprehensive investigation into regulating the multi-electron transfer redox chemistry of Te by incorporating cesium iodide (0.3 M CsI) into a low-concentration aqueous electrolyte (2 M ZnSO 4 ), facilitating the formation of a stable Cs 2 TeI 6 double perovskite during oxidation. This phase formation effectively suppresses the hydrolysis and dissolution of Te 4+ species and decouples the redox reactions from water participation, leading to significantly reduced polarization. The CsI regulated Zn-Te battery delivers a high energy efficiency of 92% for the 4-electron process (Te Te 4+ ) and high discharge capacity of 1248 mA h g −1 for the 6-electron process (Te 2− Te Te 4+ ). Furthermore, the 4-electron cell exhibits exceptional cycling stability, retaining 80% capacity after 1500 cycles. This study provides valuable insights into tailoring the redox chemistry of high-capacity electrode materials, paving the way for the development of high-performance aqueous battery systems. CsI in 2 M ZnSO 4 aqueous electrolyte facilitates the formation of Cs 2 TeI 6 perovskite phase for Te electrode, effectively suppressing Te 4+ hydrolysis and sustaining fast redox kinetics in multi-electron transfer Zn-Te aqueous batteries.