A polymeric separator membrane with chemoresistance and high Li-ion flux for high-energy-density lithium metal batteries

Lithium (Li) metal batteries are limited by the unstable deposition structure of Li metal, triggering aggressive electrolyte consumption and presenting safety concerns. A fundamental solution regulating the Li metal deposition structure is contingent on the homogeneity of Li-ion flux at the Li-electrolyte interface and electrolyte-infiltrated separator matrix. Here, we report a rational design for a separator coupling with two functional polymers, i.e., ferroelectric terpolymer-polydopamine in a core-shell structure. A conformal polydopamine layer prevents electrolyte dissolution of the terpolymer, improves electrolyte affinity, and suppresses detrimental chemical crossover. Incorporating the high ferroelectricity of the terpolymer increases the Li-ion transference number and ionic conductivity, ensuring the homogeneity of Li-ion transport through the separator's pore network. With this bicomponent separator, stable cycling of a pouch-type full cell is achieved, comprising a thin Li metal (20 µm) anode and a layered oxide cathode under the limited electrolyte condition.