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 SnP₂O₇, 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 SnCl₄·5H₂O. Phytic acid serves as a benign phosphorus source and a chelating agent that locks Sn²⁺/Sn⁴⁺ 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. SnP₂O₇/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 SnO₂/C and SSS/C(Sn₃(PO₄)₂/ SnP₂O₇/ SnO₂). 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.