High‐Entropy Metal Sulfide Nanocrystal Libraries for Highly Reversible Sodium Storage

Abstract Controlled synthesis of high‐entropy materials offers a unique platform to explore unprecedented electrochemical properties. High‐entropy metal sulfides (HEMSs) have recently emerged as promising electrodes in electrochemical energy storage applications. However, synthesizing HEMSs with a tunable number of components and composition is still challenging. Here, a HEMS library is built by using a general synthetic approach, enabling the synthesis of HEMS with arbitrary combinations of 5 to 12 out of 28 elements in the periodic table. The formation of a solid solution of HEMS is attributed to the two‐step method that lowers the energy barrier and facilitates the sulfur diffusion during the synthesis. The hard soft acid base (HSAB) theory is used to precisely describe the conversion rates of the metal precursors during the synthesis. The HEMSs as cathodes in Na‐ion batteries (SIBs) is investigated, where 7‐component HEMS (7‐HEMS) delivers a promising rate capability and an exceptional sodium storage performance with reversible a capacity of 230 mAh g⁻¹ over 3000 cycles. This work paves the way for the multidisciplinary exploration of HEMSs and their potential in electrochemical energy storage.