Suppressing Jahn–Teller distortion and locking lattice water with doped Fe(iii) in birnessite toward fast and stable zinc-ion batteries

Abstract

Birnessite has been regarded as a promising cathode material for aqueous zinc-ion batteries (ZIBs), but severe Jahn–Teller distortion and abrupt lattice collapse at deep charged states lead to serious problems such as poor capacity retention and short cycle life, which severely impede its practical applications. We herein report the construction of an advanced layered Fe-doped Na_0.55Mn₂O₄·xH₂O (Fe–NMO·xH₂O) cathode to promote zinc-ion storage performance and electrochemical stability. An outstanding capacity of 102 mA h g⁻¹ at a high current density of 20 A g⁻¹ and a long cycle life of 6000 cycles have been achieved, comparable to the state-of-the-art manganese oxide-based cathodes. Both experimental measurements and theoretical calculations reveal that Fe³⁺ substitution and lattice water cooperatively stabilize the interlayer structure, accelerate zinc-ion diffusion, and improve electronic conductivity. Notably, Fe doping is conducive to alleviating the Jahn–Teller effect and locking lattice water, which effectively prevents phase transformation and lattice collapse during the (de)intercalation process. This work sheds light on the synergistic interplay between dopants and structural water in zinc-ion storage and demonstrates instructive strategies to regulate layered structures for ZIBs.