Ultrafast sodium storage of alkylamine molecule tailored MnPS3 enabled by quasi-topological intercalation mechanism

Abstract

Two-dimensional transition metal trithiophosphates (TMPS₃, TM = Mn, Fe, Co, etc.) are competitive anode materials for sodium-ion batteries (SIBs) due to their high theoretical capacity (>1,300 mAh g⁻¹) but suffer from limited practical capacity (∼300 mAh g⁻¹) and inferior rate capability caused by sluggish Na⁺ intercalation/deintercalation kinetics and severe structural collapse. Herein, alkylamine molecules are first proposed as intercalation guests to significantly boost the electrochemical activity and stability of MnPS₃. Compared to MnPS₃, C₃H₉N-MnPS₃ enlarges the interlayer spacing from 6.48 to 10.23 Å and shows a 10⁵ times higher electrical conductivity, which provides fast ion/electron transport and high strain adaptability, realizing a quasi-topological Na⁺ intercalation mechanism. Consequently, C₃H₉N-MnPS₃ exhibits an ultrahigh reversible capacity of 775 mAh g⁻¹ at 0.5 A g⁻¹ and superior high-rate cycling stability with ∼100% capacity retention after 2,500 cycles at 15 A g⁻¹, ranking it among the top metal trithiophosphate-based anode materials reported. Theoretical calculations indicate that the improved sodium storage performance of C₃H₉N-MnPS₃ results from the reduced bonding energy of P–S bonds and increased adsorption energy of Na⁺. This work is expected to provide an efficient strategy for the design of high-performance layered anode materials for SIBs.