Strong coordination interaction in amorphous Sn-Ti-ethylene glycol compound for stable Li-ion storage

Sn has been considered one of the most promising metallic anode materials for lithium-ion batteries (LIBs) because of its high specific capacity. Herein, we report a novel amorphous tin-titanium-ethylene glycol (Sn-Ti-EG) bimetal organic compound as an anode for LIBs. The Sn-Ti-EG electrode exhibits exceptional cyclic stability with high Li-ion storage capacity. Even after 700 cycles at a current density of 1.0 A g⁻¹, the anode maintains a capacity of 345 mAh g⁻¹. The unique bimetal organic structure of the Sn-Ti-EG anode and the strong coordination interaction between Sn/Ti and O within the framework effectively suppress the aggregation of Sn atoms, eliminating the usual pulverization of bulk Sn through volume expansion. Furthermore, the Sn M-edge of the X-ray absorption near-edge structure spectra obtained using soft X-ray absorption spectroscopy signifies the conversion of Sn²⁺ ions into Sn⁰ during the initial lithiation process, which is reversible upon delithiation. These findings reveal that Sn is one of the most active components that account for the excellent electrochemical performance of the Sn-Ti-EG electrode, whereas Ti has no practical contribution to the capacity of the electrode. The reversible formation of organic functional groups on the solid electrolyte interphase is also partly responsible for its cyclic stability.