Recent Progress on Sb- and Bi-based Chalcogenide Anodes for Potassium-Ion Batteries.

Potassium ion batteries (PIBs) are potential alternative energy storage systems to lithium ion batteries (LIBs), due to elemental abundance of potassium, low cost and similar working principle to LIBs. Recently, metal chalcogenides (MCs) have gained enormous interests, especially antimony (Sb)-, bismuth (Bi)-based chalcogenides because they were able to undergo alloying/conversion dual mechanism, which can provide higher specific capacity and energy density (K3 Sb∼660 mA h g-1 , K3 Bi∼385 mA h g-1 ). However, several challenges hinder the development of Sb-, Bi-based chalcogenide anode materials for PIBs, such as huge volume expansion during potassiation, unstable solid-electrolyte interface (SEI), slow reaction kinetics, and polychalcogenide-induced shuttle effect. In this review, the current state-of-the-art Sb-, Bi-based chalcogenides are comprehensively summarized, including the reaction mechanism, electrochemical performance, ingenious nanostructures, electrolyte systems, and prospects for future development. This review contributes to understanding the K+ storage mechanism and the interaction between active materials and electrolytes, providing guidance and foundation for the design of next-generation high-performance PIBs.

Crystal Facet and Architecture Engineering of Metal Oxide Nanonetwork Anodes for High-Performance Potassium Ion Batteries and Hybrid Capacitors.

Metal oxides are considered as prospective dual-functional anode candidates for potassium ion batteries (PIBs) and hybrid capacitors (PIHCs) because of their abundance and high theoretic gravimetric capacity; however, due to the inherent insulating property of wide band gaps and deficient ion-transport kinetics, metal oxide anodes exhibit poor K+ electrochemical performance. In this work, we report crystal facet and architecture engineering of metal oxides to achieve significantly enhanced K+ storage performance. A bismuth antimonate (BiSbO4) nanonetwork with an architecture of perpendicularly crossed single crystal nanorods of majorly exposed (001) planes are synthesized via CTAB-mediated growth. (001) is found to be the preferential surface diffusion path for superior adsorption and K+ transport, and in addition, the interconnected nanorods gives rise to a robust matrix to enhance electrical conductivity and ion transport, as well as buffering dramatic volume change during insertion/extraction of K+. Thanks to the synergistic effect of facet and structural engineering of BiSbO4 electrodes, a stable dual conversion-alloying mechanism based on reversible six-electron transfer per formula unit of ternary metal oxides is realized, proceeding by reversible coexistence of potassium peroxide conversion reactions (KO2↔K2O) and BixSby alloying reactions (BiSb ↔ KBiSb ↔ K3BiSb). As a result, BiSbO4 nanonetwork anodes show outstanding potassium ion storage in terms of capacity, cycling life, and rate capability. Finally, the implementation of a BiSbO4 nanonetwork anode in the state-of-the-art full cell configuration of both PIBs and PIHCs shows satisfactory performance in a Ragone plot that sheds light on their practical applications for a wide range of K+-based energy storage devices. We believe this study will propose a promising avenue to design advanced hierarchical nanostructures of ternary or binary conversion-type materials for PIBs, PIHCs, or even for extensive energy storage.

Large-scale synthesis of few-layered copper antimony sulfide nanosheets as electrode materials for high-rate potassium-ion storage.

Metal chalcogenides (MCs) have received widespread attentions in potassium ion storage, due to their high theoretical specific capacity and low cost. However, practical applications are still a challenge because of the slow diffusion rate and large ionic radius, leading to dramatic volume expansion and slow rate performance. Herein, we introduce a simple and large scale solvothermal method to synthesize high-quality two-dimensional (2D) layered CuSbS2 nanosheets with a thickness of about 5 nm. The thin 2D layered structure has a weak van der Waals gap and a large exposed surface area to contact the electrolyte and promotes rapid K+ diffusion kinetics. In addition, the in-situ copper exsolution during potassiation process enhances the rate capability of K+ storage. CuSbS2 half cells exhibited excellent rate performance, delivering specific capacities of 573, 505, 476, 230, 177 mAh g-1 at current densities of 0.1, 0.5, 1, 5, 10 A g-1, respectively. The unique K+ electrochemical storage mechanism and resistance change during reaction process was revealed in detail by operando XRD, XPS and TEM. Finally, potassium ion hybrid capacitors (PIHCs) with CuSbS2 nanosheets as anode and AC as cathode demonstrated excellent performances with the maximum energy density of 127 W h kg-1 and the power density of 2415 W kg-1, providing an example of rationally design a high rate battery-type PIHC anode.