Electrode-supported thin α-alumina separators for lithium-ion batteries

Lithium ion batteries with an inorganic separator offer improved safety and enhanced reliability. The free-standing inorganic separators recently studied for lithium ion batteries are brittle and expensive. To address these issues, this paper reports the synthesis of a new and stable electrode-supported separator using a low-cost ceramic powder. Thin and porous α-Al₂O₃ separator films of thicknesses down to 40 μm were coated on Li₄Ti₅O₁₂ (LTO) electrode by blade-coating a slurry of α-Al₂O₃, water and a small amount of polyvinyl alcohol (PVA). The performance of the LTO/Li cells with coated α-Al₂O₃ separator improves with decreasing PVA content. Cells with coated α-Al₂O₃ separator containing 0.4wt% PVA exhibit similar discharge capacity but better rate capability than those with commercial polypropylene (PP) or thick sintered α-Al₂O₃ separator. The coated α-Al₂O₃ separator does not react with LTO even after many charge/discharge cycles. Fabrication of the electrode-supported α-Al₂O₃ separator is scalable and cost-effective, offering high potential for practical application in industrial lithium ion battery manufacturing.