Efficient asymmetric diffusion channel in MnCo2O4 spinel for ammonium-ion batteries.

Transition metal oxides ion diffusion channels have been developed for ammonium-ion batteries (AIBs). However, the influence of microstructural features of diffusion channels on the storage and diffusion behavior of NH₄⁺ is not fully unveiled. In this study, by using MnCo₂O₄ spinel as a model electrode, the asymmetric ion diffusion channels of MnCo₂O₄ have been regulated through bond length optimization strategy and investigate the effect of channel size on the diffusion process of NH₄⁺. In addition, the reducing channel size significantly decreases NH₄⁺ adsorption energy, thereby accelerating hydrogen bond formation/fracture kinetics and NH₄⁺ reversible diffusion within 3D asymmetric channels. The optimized MnCo₂O₄ with oxygen vacancies/carbon nanotubes composite exhibits impressive specific capacity (219.2 mAh g^-1 at 0.1 A g^-1) and long-cycle stability. The full cell with 3,4,9,10-perylenetetracarboxylic diimide anode demonstrates a remarkable energy density of 52.3 Wh kg^-1 and maintains 91.9% capacity after 500 cycles. This finding provides a unique approach for the development of cathode materials in AIBs.