Tantalum oxide nanosheets/polypropylene composite separator constructing lithium-ion channels for stable lithium metal batteries

Developing next-generation high-energy-density rechargeable batteries is pivotal to solve the growing demand for sustainable energy. Lithium metal battery (LMB) is the representative in post-lithium-ion battery era. However, uncontrollable growth of Li dendrites and low Coulombic efficiency (CE) prevent it from practical applications in LMBs. Here, a multifunctional tantalum oxide nanosheets/polypropylene (TaO3@PP) composite separator is developed to regulating ion transport in atomic scale. The TaO3 coating can improve the wettability and thermal stability of the PP separator. The openings of the nanomesh structure provide Li+ channels to allow efficient lithium-ion transport. The electrostatic attraction force between TaO3 nanosheets and Li+ and the electrostatic repulsion force between TaO3 nanosheets and anions ensuring the fast Li+ diffusion and low concentration polarization. The TaO3@PP separator can regulate Li+ distribution and promote uniform lithium deposition, inhibiting the Li dendrite growth. Thus, the composite separator achieves a high Li-ion transference number of 0.72. The LiFePO4||Li cell with the composite separator delivers high discharge capacity of 145 mAh g(-1) over 500 cycles at 0.5 C.