Electrolyte Solvation Structure Manipulation and Synthetic Optimization for Enhanced Potassium Storage of Tin Phosphide/Carbon Alloy-Based Electrode

Abstract

Phosphorus-based materials are considered to be reliable anode materials for potassium ion batteries (PIBs) due to their high theoretical capacity but suffer from inferior cycling stability and an unstable Solid Electrolyte Interface (SEI) layer. Herein, optimized ball-milled parameters and concentrated electrolytes are introduced to enhance the electrochemical performance of Sn4P3/C anodes. Consequently, the electrodes synthesized under optimized ball milling parameters could deliver a reversible capacity of 307.8 mA h g−1 in diluted Potassium hexafluorophosphate (KPF6) electrolyte. Moreover, compared with diluted bis(fluorosulfonyl)imide (KFSI) electrolyte, a robust inorganic KF-rich SEI layer can be formed on the electrode’s surface by employing concentrated KFSI electrolyte and provides more rapid K ion conduction rates. Meanwhile, a large proportion of the FSI− anions participated in the K+ solvation shell when the KFSI concentration increased. As a result, high specific capacities (225.1 mA h g−1 at 50 mA g−1 after 200 cycles) and excellent Coulombic efficiency (97.24% at 500 mA g−1 after 200 cycles) can be achieved. This work may deepen our understanding of synthetic optimization in electrode material design and the role of concentrated electrolyte in tunning the solvation structure, and also offer an insightful clue to the design of high-capacity phosphorus-based anodes.