Antimony nanobelt asymmetric membranes for sodium ion battery

In this study, composite asymmetric membranes containing antimony (Sb) nanobelts are prepared via a straightforward phase inversion method in combination with post-pyrolysis treatment. Sb nanobelt asymmetric membranes demonstrate improved cyclability and specific capacity as the alloy anode of sodium ion battery compared to Sb nanobelt thin films without asymmetric porous structure. The unique structure can effectively accommodate the large volume expansion of Sb-based alloy anodes, prohibit the loss of fractured active materials, and aid in the formation of stable artificial solid electrolyte interphases as evidenced by an outstanding capacity retention of ∼98% in 130 cycles at 60 mA g⁻¹. A specific capacity of ∼600 mAh g⁻¹ is obtained at 15 mA g⁻¹ (1/40C). When the current density is increased to 240 mA g⁻¹, ∼80% capacity can be maintained (∼480 mAh g⁻¹). The relations among phase inversion conditions, structures, compositions, and resultant electrochemical properties are revealed through comprehensive characterization.