500 Wh/kg Class High-Areal-Capacity Lithium Metal Pouch Cell Enabled by Practical Polymer Protective Layer

Abstract Stable high-areal-capacity lithium metal under practical conditions is decisive to reach 500 Wh/kg, which is plagued by undesirable lithium-electrolyte interface. Herein, we design and synthesize poly(2-hydroxyethyl acrylate-co-sodium benzenesulfonate) (PHS) as lithium-electrolyte interfacial protective layer, containing soft poly (2-hydroxyethyl acrylate) (PHEA) with hydroxyl to provide strong interaction with Cu substrate by hydrogen-bond and improve the flexibility, and ion-conductive poly(sodium p-styrene sulfonate) (PS) with large Li chemisorption energy to anchor and disperse Li+. Cryo-TEM images revel that multifunctional PHS induces the formation of rigid and crystalline fluorinated SEI inner layers. The theoretical calculations confirm that -SO3− in PS promotes Li+ towards interchain migration through cation-dipole interaction, enabling uniform Li+ diffusion, achieving average Coulombic efficiency of 99.46% under 6 mAh/cm2 for Li|PHS-Cu cell. When paired with high-areal-capacity NCM83 (6.0 mAh/cm2), the assembled NCM83|PHS-Li pouch cell with the capacity of 6.87 Ah can reach 490.4 Wh/kg and exhibits 92.9% capacity retention after 150 cycles.