Suppressing lithium dendrite growth on lithium-ion/metal batteries by a tortuously porous γ-alumina separator

The challenges of dendrite propagation limit the operational safety and long-term cycling stability of lithium-ion batteries and development of high energy density lithium-metal batteries. Solid state electrolytes may eliminate the propagation of dendrites, but they fail to achieve high Li-ion conductivity and charge transfer rate at room temperature resulting in undesired cell performance. Here we report the usage of electrode-coated plate-structured γ-alumina separators with liquid electrolyte for high performance, safe lithium-ion batteries. The γ-alumina separators, made of γ-alumina plates of high aspect ratio, are mechanically strong and tortuously porous, and therefore effective in preventing passage of dendrites. Nickel-manganese-cobalt-oxide/lithium cells with a plate-structured γ-alumina separator show stable cycle performance without passage of dendrites up to 3 C-rate of charging and discharging. Same cells with commercial polypropylene (PP-2500) separator or spherical-structured α-alumina separator of similar pore size to γ-alumina separator, could not achieve the above-mentioned dendrite free cycling even at much lower C-rates (0.2 C and 1.0 C respectively). A comparison of the three cells with different separators clearly shows that the hardness and high tortuosity of the separator are effective in preventing dendrite propagation. This work results in the development of a lithium-ion-battery with improved safety and shows a new direction in the design and fabrication of high performance and safe lithium-metal batteries.