Transition metal sulfides (TMSs) have been demonstrated as attractive anodes for potassium-ion batteries (KIBs) due to the high capacity, abundant resource, and excellent redox reversibility. Unfortunately, practical implementation of TMSs to KIBs is still hindered by the unsatisfactory cyclability and rate performance which result from the vast volume variation during charge/discharge processes. Herein, a uniform nitrogen-doped carbon coated Cu2S hollow nanocube (Cu2S@NC) is designed as an anode material for the KIB, which displays an outstanding cycle performance (317 mAh g–1 after 1200 cycles at 1 A g–1) and excellent rate capacity (257 mAh g–1 at 6 A g–1) in a half-cell. The hollow nanosized structure can both shorten the diffusion length of potassium ions/electrons and buffer the volume expansion upon cycling. Besides, the high concentration electrolyte is beneficial to form the stable solid electrolyte interphase (SEI) film, reducing the interface impedance and enhancing the cycling stability. Ex situ transmission electron microscopy (TEM) and ex situ X-ray diffraction (XRD) reveal the reaction mechanism of Cu2S@NC.

The potassium ion batteries (KIBs) based on conversion/alloying reaction mechanisms show high theoretical capacity. However, their applications are hampered by the poor cyclability resulting from the inherent large volume variations and the sluggish kinetics during K+ repeated insertion/extraction process. Herein, taken Sb2Se3 as a model material, by rational design, nickel doped‐carbon coated Sb2Se3 nanorods (denoted as (Sb0.99Ni0.01)2Se3@C) are prepared through combined strategies of the conductive encapsulation and crystal structure modification. The carbon coating acts as an efficient buffer layer that maintains superior structural stability upon cycling. The introduction of Ni atoms can enhance electrical conductivity, leading to outstanding rate performance, which are confirmed by density functional theory calculation. The (Sb0.99Ni0.01)2Se3@C displays excellent reversible capacity (410 mAh g−1 at 0.1 A g−1 after 100 cycles) and unprecedented rate capability (140 mAh g−1 at 10 A g−1). Furthermore, KFeHCF//(Sb0.99Ni0.01)2Se3@C full cell exhibits a high specific capacity (408 mAh g−1 at 0.1 A g−1), superior rate capability (260 mAh g−1 at 2 A g−1). This work can open up a new avenue for the design of stable conversion/alloying‐based anodes for high energy density KIBs.