Self-Healing, Ga-Sb Alloy Confined Sn Anode for Stable Na-Ion Storage in Glyme Based Electrolytes

Abstract

In this contribution, the development of a self-healable GaSb alloy featuring a confined Sn (core-shell) structure is reported for stable Na⁺ storage in an ether-based electrolyte. The core-shell architecture of GaSb@Sn has been validated through high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) paired with electron energy loss spectroscopy (EELS) analysis. The GaSb@Sn support on carbon electrode has delivered specific capacity of 560 mAh g_electrode⁻¹ at 50 mA g⁻¹ with 89% retention capacity after 1200 cycles and specific capacity of 449 mAh g_electrode⁻¹ at 2 Ag⁻¹ with 82% retention capacity after 2000 cycles. The GaSb@Sn/C electrode stores Na⁺ by forming Na-Sn, Na-Sb-O, and Na-Ga-O intermetallic compounds, as confirmed by operando XRD studies. Operando electrochemical dilatometry studies reveal that the self-healable electrode expands by 33% at the electrode level during Na⁺ insertion, significantly lower than the theoretically predicted expansion of Sn, which is 420%. DFT calculations show that the adsorption of diglyme on GaSb@Sn (−0.4 eV) is weaker than that on bulk Sn (−5.1 eV). The weaker interaction between diglyme and GaSb@Sn could be responsible for the thinner SEI formation on the edges of GaSb@Sn, thereby resulting in the high initial coulombic efficiency (GaSb@Sn- 81%, Bulk Sn-62%) and stable cycle life.