An energy-efficient tellurium electrode enabled by a Cs2TeI6 perovskite structure for durable aqueous Zn–Te batteries

Abstract

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 Te⁴⁺ 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 ZnSO₄), facilitating the formation of a stable Cs₂TeI₆ double perovskite during oxidation. This phase formation effectively suppresses the hydrolysis and dissolution of Te⁴⁺ 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 ⇌ Te⁴⁺) and high discharge capacity of 1248 mA h g⁻¹ for the 6-electron process (Te²⁻ ⇌ Te ⇌ Te⁴⁺). 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.