From 1D to 1D–2D–1D: new insights into Li+ diffusion behavior in optimized MnO2 with the cooperative effect of tunnel and interface

Abstract

In the absence of long-range order, the electrochemical performance of multicomponent γ-MnO₂ is highly dependent on the local structural properties. However, early studies, generally based on traditional bulk phase characterization, tended to reveal average structural information and were less sensitive to the local environment. This thus led to unclear structure–property relationships for γ-MnO₂. Different from traditional one-dimensional tunnel diffusion, in this work, a multidimensional Li⁺ diffusion mechanism is proposed after clarifying the special local structural properties. The individual one-dimensional diffusion channels of the tunnel structure were connected and developed into continuous multidimensional diffusion paths via a unique interface structure at which Li⁺ diffusion was dynamically favorable. From one-dimensional to multidimensional Li-ion diffusion, the optimized MnO₂ exhibited high power and high energy density due to the unconventional diffusion properties. This study provides further understanding of Li⁺ solid-state diffusion and potentially provides a way to improve the electrochemical performance of γ-MnO₂ and other intercalation compound materials.