Synergistic cation/anion modulation of metal phosphorus trichalcogenides for enhanced potassium-ion storage performance†

Abstract

Metal phosphorus trichalcogenides (MPX₃) are promising anode materials for rechargeable batteries due to their high theoretical capacity and layered structure, yet their utilization in potassium-ion batteries is in its nascent stages. Notably, tunable cations and anions give them abundant structural characteristics. Herein, the synergistic modulation of cations and anions in MPX₃ anodes for potassium storage is meticulously dissected through comprehensive theoretical computations and experimental analyses. Through a medium-entropy cation and alloy anion co-tuning strategy, a new Mg_0.4Fe_0.2Co_0.15Ni_0.15Zn_0.1PS_1.4Se_1.6 (ME-SSe) material can be obtained. Theoretically, ME-SSe possesses better K-ion adsorption/diffusion ability than its counterparts without anion–cation engineering. In a pioneering approach, an ME-SSe@C/CNT composite is fabricated via encapsulating ME-SSe nanoparticles within a dual carbon framework (porous carbon and carbon nanotube network), which not only augments the electrical conductivity but also mitigates the volumetric fluctuations of the ME-SSe anode during cycling. Consequently, the ME-SSe@C/CNT exhibits much improved potassium-ion storage capacity, cycling stability, and rate capability than the counterpart electrodes. At 0.1 A g⁻¹, the ME-SSe@C/CNT electrode sustains a remarkable reversible capacity of 232 mA h g⁻¹ over 100 cycles and superior cycling stability over 1000 cycles at 1.0 A g⁻¹. The cation/anion co-tuning strategy delineated herein offers a paradigm-shifting blueprint for enhancing the battery performance of MPX₃-based anodes.