In Situ Nanolization Confers Ball-Milling-Prepared Sb₄O₅Cl₂ Microtri-Prisms an Exceptional Potassium-Ion Storage Performance

Potassium ion batteries (PIBs) are potentially low-cost and high-voltage alternative energy storage systems to lithium-ion batteries. Anode materials with high density and high specific capacity, such as antimony-based materials, are the most sought-after objects. Herein, microtri-prism Sb4O5Cl2 with a uniform size and high compact density of 3.5 g cm–3 is controllably synthesized by the ball-milling-assisted hydrolysis method. Distilled water and absolute ethanol in an optimized volumetric ratio of 2/1 are introduced as reaction solvents to modify the reaction rate and, in turn, control the products’ morphology. The ex situ investigation results indicate that the in situ nanolization conversion from microtri-prisms to nanoparticles of Sb4O5Cl2 during the initial discharge process confers Sb4O5Cl2 an exceptional potassium-ion storage performance. The electrochemical measurement results further manifest that potassium-ion storage performance achieved by the Sb4O5Cl2 microtri-prisms is superior to other reported Sb4O5Cl2. At 0.1, 0.2, 0.5, 1.0, and 2.0 A g–1, K//Sb4O5Cl2 microtri-prisms half PIBs could deliver 501.9, 456.6, 401.1, 325.0, and 249.2 mA h g–1, and retain 193.2 mA h g–1 with a Coulombic efficiency of 99.7% and a capacity retention ratio of 95.1% after 500 cycles at 2.0 mA g–1.