MOF-Derived Hierarchically Porous Carbon with Orthogonal Channels for Advanced Na–Se Batteries

Abstract

Na–Se batteries with high theoretical capacity and rich natural abundance are regarded as desirable substitutes for lithium-ion batteries in the predicament of scarce lithium resources. However, the huge volume expansion of Se and the shuttling effect of polyselenides hinder the development of Na–Se batteries. Herein, the hierarchically porous carbon encapsulated Se (Se/HPC) is successfully prepared by molten Se diffusing into the multi-scaled orthogonal channels of In-MOF derived carbon matrix. The Se/HPC realizes effective nano-confinement of Se phase and accelerates charge transfer during cycling to efficiently buffer the volume expansion of Se, which avoids the shuttling effect and promote electrochemical performance. The Se/HPC achieves admirable electrochemical performance for delivering high capacity of 465 mAh g⁻¹ at a high current density of 50 A g⁻¹ and 533 mAh g⁻¹ after 2800 cycles at 10 A g⁻¹ with 0.003% capacity decay per cycle. Density functional theory calculations demonstrate that the Se─C bond is thermodynamically and kinetically beneficial for the adsorption/diffusion of Na⁺. This work can inspire the further exploration of utilizing the intrinsic crystal structure of MOF to construct a hierarchically porous carbon matrix in situ as carrier for the active Se component, and provide inspiration for future construction of higher-performance electrode materials.