Super Na⁺ Half/Full Batteries and Ultrafast Na⁺ Diffusion Kinetics of <scp>Cobalt‐Nickel</scp> Selenide from Assembling Co_0.<scp>₅Ni₀</scp>_.<scp>₅Se₂</scp>@<scp>NC</scp> Nanosheets into <scp>Cross‐Stacked</scp> Architecture

Abstract

Main observation and conclusion Exploration of advanced anode materials for sodium‐ion batteries (SIBs) is still a big challenge due to the large radius of sodium. In this work, the hierarchical architectures assembled from N‐doped carbon‐coated Co 0.5 Ni 0.5 Se 2 (Co 0.5 Ni 0.5 Se 2 @NC) nanoparticles encapsulated into cross‐stacked nanosheets have been successfully prepared from the cobalt‐nickel binary‐metal organic frameworks (CoNi‐MOF) by two steps of the solid‐state selenization and carbon coating processes. Importantly, the resultant hierarchical Co 0.5 Ni 0.5 Se 2 @NC architecture can achieve a satisfactory electrochemical performance, maintaining a high‐rate capacity of 330 mA·h·g –1 at 3 A·g –1 and a stable cyclability of 100 cycles without obvious capacity decay at 0.2 A·g –1 . The design of distinct superstructure can not only be applied to other electrode materials but also boost the forward development of energy storage systems.