Strong coordination interaction in amorphous Sn-Ti-ethylene glycol compound for stable Li-ion storage
Yuqing Cai, Haigang Liu, Haoran Li, Qianzi Sun, Xiang Wang, Fangyuan Zhu, Ziquan Li, Jang‐Kyo Kim, Zhen‐Dong Huang
Abstract
Sn has been considered among the most promising metallic anode materials for lithium-ion batteries (LIBs) thanks to its high specific capacity. Herein, we report a novel amorphous tin-titanium-ethylene glycol (Sn-Ti-EG) bimetal organic compound as anode for LIBs. The Sn-Ti-EG electrode exhibits exceptional cyclic stability with high Li-ion storage capacities. Even after 700 cycles at a current density of 1.0 A g<sup>-1</sup>, the anode maintains a capacity of 345 mAh g<sup>-1</sup>. 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. Further, the Sn M-edge of X-ray absorption near edge structure spectra obtained from the soft X-ray absorption spectroscopy signifies the conversion of Sn<sup>2+</sup> ions to Sn<sup>0</sup> during the initial lithiation process, which is reversible to Sn<sup>2+</sup> upon de-lithiation. These findings manifest Sn being among the most active components that account for the excellent electrochemical performance of the Sn-Ti-EG electrode, while Ti has no practical contribution to the electrode’s capacity. The reversible formation of organic functional groups on the solid electrolyte interphase is also partly responsible for its cyclic stability.