Phytic acid chelation-assisted deep eutectic solvents for constructing high-cycle-stability SnP2O7/C anode materials in Li-Ion batteries

Tin-based anodes exhibit high capacities, rendering them suitable for lithium-ion batteries (LIBs). However, their practical use is hindered by their extreme swelling and rapid fading. Moreover, traditional synthesis methods for SnP 2 O 7 , which is a promising tin-based system, involve several limitations such as toxic solvents, complex procedure, high energy consumption, and hazardous phosphorus reagents. Herein, we overcame these limitations using a simple method involving a deep eutectic solvent based on polyethylene glycol and SnCl 4 ·5 H 2 O. Phytic acid serves as a benign phosphorus source and a chelating agent that locks Sn 2 + /Sn 4+ into a rigid Sn–O–P scaffold. The special properties of the material mitigate the structural damage caused by lithium-ion deintercalation during charging and discharging. SnP 2 O 7 /C retains 729 mAh g −1 after 300 cycles at 0.2 A g −1 (retention = 99.4 %) and 515 mAh g −1 after 1000 cycles at 1 A g −1 , considerably surpassing those of SnO 2 /C and SSS/C(Sn 3 (PO 4 ) 2 / SnP 2 O 7 / SnO 2 ). The proposed synthesis method is cost-effective, scalable, and green. Moreover, the main mechanism of this route, i.e., phytic acid chelation, offers a long-lasting solution to the long-standing problems of tin-based anode materials for LIBs.