Hollow SnO2 nanosphere-coated separators for dendrite-free lithium metal batteries†

Abstract

Serious dendrite formation remains a significant challenge for the practical application of high-energy lithium metal batteries (LMBs). Fabricating separators with a high lithium ion transference number (t_Li⁺) and uniform pore structure is an effective strategy to homogenize Li⁺ flux and suppress dendrite growth. Here, hollow SnO₂ nanospheres with high structural stability were synthesized through a solvothermal method for surface coating of a poly(ethylene-co-acrylic acid) (EAA) separator (EAA@SnO₂). The EAA matrix enhances the t_Li⁺ through the interaction of carboxyl groups with ions in the electrolyte, while hollow SnO₂ nanospheres convert to Li_xSn during cycling, regulating Li⁺ flux and promoting uniform solid electrolyte interphase formation. The as-prepared separator-based Li symmetric cells demonstrate stable cycling for over 1000 h with a low overpotential of 17 mV. Additionally, the LiFePO₄||Li cells with the EAA@SnO₂ separator deliver an initial capacity of 116.6 mA h g⁻¹ and a capacity retention of over 80.96% after 200 cycles at 5C. The utilization of metallic hollow SnO₂ nanospheres for separator coating proves to be a promising strategy for high-performance LMBs.