Mesoporous Thin-Wall Molybdenum Nitride for Fast and Stable Na/Li Storage

Abstract

Sluggish reaction kinetics induced by the poor solid-state ion diffusion and low electrical conductivity of electrode materials are currently in conflict with increasing fast-charge needs for sodium-ion batteries (SIBs) based on conversion mechanism. Herein, mesoporous, conductive, thin-wall three-dimensional (3D) skeletons of molybdenum nitride (meso-Mo₂N) were established and employed as anodes to facilitate the rate performance of SIBs. Mesoporous channels (∼9.3 nm) with very thin walls (<8 nm) and conductive networks in meso-Mo₂N enable the rapid Na⁺ infiltrability/diffusion and fast electron migration, respectively. The facilitated ion diffusion/transfer ability is corroborated by cyclic voltammetry tests and galvanostatic intermittent titration technique with a higher Na⁺ diffusion coefficient and a larger Na⁺ diffusion-dominated capacity. Consequently, meso-Mo₂N exhibits a superior rate capability and a steady specific capacity of 158 mAh g^-1 at 1 A g^-1 after 1000 cycles for SIBs, surpassing the nonporous Mo₂N and even the previously reported Mo₂N. Furthermore, the proof of concept can be also extended to enhanced Li storage. Such a mesostructured design with 3D mesoporous, conductive thin walls of electrodes is a promising strategy for achieving fast-charging and high-performance Na/Li storage.