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

Abstract Conversion‐type tellurium‐based cathodes have attracted great attention in aqueous zinc‐ion batteries (AZIBs) due to potentially high capacity with impressive Te 4+ /Te 0 /Te 2− conversion. However, impeded by the low‐conductivity Te 4+ species and unpreferred kinetics, realizing deep zinc‐tellurium redox remains a major challenge. Herein, energetic NiTe 2 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 Te 4+ species from direct oxidation of NiTe 2 in dilute mild‐aqueous electrolyte undergo a thermodynamic two‐step TeO 2 →Te→ZnTe discharge process, while the intertwined tellurium oxides and high‐conductivity nickel monomers derived in situ from NiTe 2 nanosheets promote a kinetics‐preferred one‐step ZnTe→TeO 2 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.