Hybrid Effect of Micropatterned Lithium Metal and Three Dimensionally Ordered Macroporous Polyimide Separator on the Cycle Performance of Lithium Metal Batteries

Short cycle life of the lithium metal secondary battery (LMSB) is largely ascribed to the dendritic growth of lithium metal during the charging process followed by continuous electrolyte decomposition. To make up for this intrinsic drawback of lithium metal, two pioneering techniques, micropatterning on lithium metal and three dimensionally ordered microporous polyimide (3DOM PI) separator, are combined to ascertain their hybrid effect on the cycle performance of LMSB. When a unit cell consisting of LiNi_0.6Mn_0.2Co_0.2O₂/3DOM PI separator/patterned lithium metal is cycled at the charging and discharging c-rates of 0.3C and 1C (1C = 2.5 mA), respectively, above 80% of the initial discharge capacity is maintained even after 400 cycles, while a control cell with polyethylene separator survives only for 130 cycles. This tremendous improvement is ascribed to the combination effect of inducing preferential lithium electrodeposition reaction into the micropattern and the uniform distribution of lithium ions on the nonpatterned lithium surface region by the 3DOM PI separator. Thus, combining these two technologies is very promising for LMSB commercialization in the future.