A tellurium iodide perovskite structure enabling eleven-electron transfer in zinc ion batteries

Abstract

The growing potential of low-dimensional metal-halide perovskites as conversion-type cathode materials is limited by electrochemically inert B-site cations, diminishing the battery capacity and energy density. Here, we design a benzyltriethylammonium tellurium iodide perovskite, (BzTEA)₂TeI₆, as the cathode material, enabling X- and B-site elements with highly reversible chalcogen- and halogen-related redox reactions, respectively. The engineered perovskite can confine active elements, alleviate the shuttle effect and promote the transfer of Cl^- on its surface. This allows for the utilization of inert high-valent tellurium cations, eventually realizing a special eleven-electron transfer mode (Te⁶⁺/Te⁴⁺/Te^2-, I⁺/I⁰/I^-, and Cl⁰/Cl^-) in suitable electrolytes. The Zn||(BzTEA)₂TeI₆ battery exhibited a high capacity of up to 473 mAh g^-1_Te/I and a large energy density of 577 Wh kg^-1 _Te/I at 0.5 A g^-1, with capacity retention up to 82% after 500 cycles at 3 A g^-1. The work sheds light on the design of high-energy batteries utilizing chalcogen-halide perovskite cathodes.