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Antimony-based materials have been considered as highly competitive anodes for sodium-ion batteries (SIBs) because of their high theoretical capacity. However, the poor rate capability and fast capacity fading, originating from sluggish kinetics and volume expansion, greatly restrict their practical application. To address the above issues, an effective spraying method and one-step partial reduction process were utilized to synthesize Sb2O3@Sb nanoparticle impregnated in N-doped carbon microcages (Sb2O3@Sb@NC) offering extraordinary sodium storage capabilities and delivering an ultra-high rate performance of 175.1 mA h g−1 at 20 A g−1 and a superior capacity retention of 245.2 mA h g−1 after 10 000 cycles under 10 A g−1 for SIBs. Such unprecedented electrochemical properties of the Sb2O3@Sb@NC electrode can be ascribed to the comprehensive characteristics derived from multi-scale structural engineering: the fast electrochemical kinetics and tight packing of Sb2O3@Sb nanoparticles with carbon sheets, the strong Na+ adsorption ability of Sb2O3@Sb@NC enhanced by the synergistic effect of heterostructures and N-doping, the structural integrity strengthened by a robust interface bond of Sb–O–C, and the improved pseudocapacitive contribution. These distinct features enable the Sb2O3@Sb@NC anode to be a potential candidate for large-scale sodium ion storage.

Bismuth-antimony alloy is considered as a promising potassium ion battery anode because of its combination of the high theoretical capacity of antimony and the excellent rate capacity of bismuth. However, the large volume change and sluggish reaction kinetic upon cycling have triggered severe capacity fading and poor rate performance. Herein, a nanoconfined BiSb in tremella-like carbon microspheres (BiSb@TCS) are delicately designed to address these issues. As-prepared BiSb@TCS renders an outstanding potassium-storage performance with a reversible capacity of 181 mAh g-1 after ultralong 5700 cycles at a current density of 2 A g-1 , and an excellent rate capacity of 119.3 mAh g-1 at 6 A g-1 . Such a superior performance can be ascribed to the delicate microstructure. The self-assembled carbon microspheres can strengthen integral structure and effectively accommodate the volume expansion of BiSb nanoparticles, and 2D carbon nanowalls in carbon microspheres can provide fast ion/electron diffusion dynamic. Theoretical calculation also suggests a thermodynamic feasibility of alloyed BiSb nanoparticles for storing potassium ion. Such a work shows that BiSb@TCS possesses a great potential to be a high-performance anode of potassium ion batteries. The rational designing of multiscaled structure would be instructive to the exploitation of other energy-storage materials.

Potassium-ion energy-storage devices have established themselves as the most important candidates for next-generation energy-storage devices in the coming future. Recently, inorganic electrode materials have riveted ever-increasing interest due to large theoretical capacity, rich sources, low price and environmental friendly advantages. However, the electrode materials of potassium-containing devices have been suffering low theoretical capacity, poor rate performance and short lifespan due to integration effects of seriously electrochemical pulverization and slow kinetics. In this timely review, we will focus on the latest progress of potassium ion energy storage devices based on beyond-carbon materials, referring to the synthesis of materials and the construction of microstructure, material component-oriented electrochemical performance, energy storage mechanism discussion, newfangled device assembly and key components. The key materials and novel theories are reviewed, and some personal viewpoints have been proposed, targeting providing some inductive opinions.