Electrolyte modulation of BiPS4 concurrently suppressing the Bi coarsening and polysulfide shuttle effect in K-ion batteries

Abstract

Emerging electrode materials for next generation batteries are consciously designed to contain multi-component active materials that can function synergistically to perform several electrochemical and structural tasks for much improved battery performance. Herein, bismuth phosphorus tetrachalcogenide (BiPS4) is introduced as an excellent anode for potassium-ion batteries. It exhibits a tunnel structure to provide exceptional ion/electron pathways and mechanical integrity against severe volume variations. Abnormal growth and aggregation of Bi nanoparticles and shuttling of the intermediate soluble potassium polysulfides are detected for the first time during the potassiation/depotassiation processes. Rational construction of BiPS4-carbon nanotube hybrid with robust chemical bonds, along with electrolyte modification during the electrochemical tests successfully hinder these two detrimental phenomena. This is revealed by various characterization techniques and theoretical calculations. Consequently, the hybrid delivers a high initial discharge capacity (863 mAh g−1 at 0.05 A g−1) and Coulombic efficiency (81.9%), excellent cycling stability (554 mAh g−1 after 300 cycles at 0.2 A g−1 and 489 mAh g−1 after 600 cycles at 1 A g−1), and superb rate capability (498 mAh g−1 at 2 A g−1) through multiplex reversible conversion and alloying reactions.