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

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 at a high current density of 50 A g and 533 mAh g after 2800 cycles at 10 A g 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.