Deep Multiphase Conversion Derived from NiTe₂ Nanosheets with Preferred Kinetics for Highly Reversible Mild Aqueous Zinc-Tellurium Batteries

Conversion-type tellurium-based cathodes have attracted great attention in aqueous zinc-ion batteries (AZIBs) due to potentially high capacity with impressive Te4+/Te-0/Te2- conversion. However, impeded by the low-conductivity Te4+ species and unpreferred kinetics, realizing deep zinc-tellurium redox remains a major challenge. Herein, energetic NiTe2 nanosheets are first proposed and implemented as preprepared tellurium-based deep redox cathodes in AZIBs with accelerated electron transport and favorable kinetics. Operando synchrotron X-ray diffraction and comprehensive ex situ characterizations demonstrate that Te4+ species from direct oxidation of NiTe2 in dilute mild-aqueous electrolyte undergo a thermodynamic two-step TeO2 -> Te -> ZnTe discharge process, while the intertwined tellurium oxides and high-conductivity nickel monomers derived in situ from NiTe2 nanosheets promote a kinetics-preferred one-step ZnTe -> TeO2 charging conversion with significantly boosted reversibility. Therefore, a high capacity of 510 mAh g(-1) at 50 mA g(-1) and 93% capacity retention over 400 cycles at 2000 mA g(-1) are established. Operando pH tracking and electrode-electrolyte engineering analyses define that the mild electrolyte environment rich in moisture and electrode conductivity optimization are both critical for achieving reversible tellurium deep redox conversion.