3D Carbon Nanotube Network Bridged Hetero‐Structured Ni‐Fe‐S Nanocubes toward High‐Performance Lithium, Sodium, and Potassium Storage

Abstract Lithium‐ion, sodium‐ion, and potassium‐ion batteries have captured tremendous attention in power supplies for various electric vehicles and portable electronic devices. However, their practical applications are severely limited by factors such as poor rate capability, fast capacity decay, sluggish charge storage dynamics, and low reversibility. Herein, hetero‐structured bimetallic sulfide (NiS/FeS) encapsulated in N‐doped porous carbon cubes interconnected with CNTs (Ni‐Fe‐S‐CNT) are prepared through a convenient co‐precipitation and post‐heat treatment sulfurization technique of the corresponding Prussian‐blue analogue nanocage precursor. This special 3D hierarchical structure can offer a stable interconnect and conductive network and shorten the diffusion path of ions, thereby greatly enhancing the mobility efficiency of alkali (Li, Na, K) ions in electrode materials. The Ni‐Fe‐S‐CNT nanocomposite maintains a charge capacity of 1535 mAh g −1 at 0.2 A g −1 for lithium ion batteries, 431 mAh g −1 at 0.1 A g −1 for sodium ion batteries, and 181 mAh g −1 at 0.1 A g −1 for potassium‐ion batteries, respectively. The high performance is mainly attributed to the 3D hierarchically high‐conductivity network architecture, in which the hetero‐structured FeS/NiS nanocubes provide fast Li + /Na + /K + insertion/extraction and reduced ion diffusion paths, and the distinctive 3D networks maintain the electrical contact and guarantee the structural integrity.