Polar Molecule Intercalation to Weaken P₂─S Bonding in MnPS₃ Toward Ultrahigh-Capacity Sodium Storage

Layered transition metal trithiophosphates (TMPS₃, TM = Mn, Fe, Co, etc.) with high theoretical capacity (>1 300 mAh g^-1) are potential anode materials for sodium-ion batteries (SIBs). However, the strong bonding between P₂ dimers and S atoms in TMPS₃ hinders the efficient alloying reaction between P₂ dimers and Na⁺, resulting in practical capacities much lower than theoretical values. Herein, a polar molecule diisopropylamine (DIPA) is intercalated into MnPS₃ for the first time to improve the sodium storage performance effectively. Theoretical calculations show that the electron transfer between DIPA and MnPS₃ induces more delocalized S p states and weaker P─S bonds, significantly enhancing the electrochemical activity and sodiation/desodiation reaction kinetics. Moreover, the expanded interlayer spacing from 6.48 to 10.75 Å enables faster Na⁺ diffusion and more active sites for Na⁺ adsorption. As expected, the DIPA-MnPS₃ exhibits an ultrahigh capacity of 1,023 mAh g^-1 at 0.2 A g^-1 and excellent cycling performance (≈100% capacity retention after 4 200 cycles at 10 A g^-1), far outperforming those metal thiophosphates anodes reported for SIBs. Interestingly, in situ and ex situ characterizations reveal a quasi-topological intercalation mechanism of DIPA-MnPS₃. This work provides a novel strategy for the design of high-performance anode materials for SIBs.