Bioinspired Separator with Ion-Selective Nanochannels for Lithium Metal Batteries

The free transport of anions through commercial polyolefin separators used in lithium metal batteries (LMBs) gives rise to concentration polarization and rapid growth of lithium dendrites, leading to poor performance and short circuits. Here, a new poly(ethylene-co-acrylic acid) (EAA) separator with functional active sites (i.e., carboxyl groups) distributing along the pore surface was fabricated, forming bioinspired ion-conducting nanochannels within the separator. As the carboxyl groups effectively desolvated Li+ and immobilized anion, the as-prepared EAA separator selectively accelerated the transport of Li+ with transference number of Li+ (tLi+) up to 0.67, which was further confirmed by molecular dynamics simulations. The battery with the EAA separator can be stably cycled over 500 h at 5 mA cm-2. The LMBs with the EAA separator have exceptional electrochemical performance of 107 mAh g-1 at 5 C and a capacity retention of 69% after 200 cycles. This work provides new commercializable separators toward dendrite-free LMBs.