Molecular-Level Anion and Li⁺ Co-Regulation by Amphoteric Polymer Separator for High-Rate Stable Lithium Metal Anode

Regulating ion transport is a prevailing strategy to suppress lithium dendrite growth, in which the distribution of ion regulatory sites plays an important role. Here a hyperbranched polyamidoamine (HBPA) grafted polyethylene (PE) composite separator (HBPA-g-PE) is reported. The densely and uniformly distributed positive -NH₂ and negative -CHNO- groups efficiently restrict the anion migration and promote Li⁺ transport at the surface of the lithium metal anode. The obtained Li foil symmetric cell delivers a stable cycle performance with a low-voltage hysteresis of 130 mV for over 1500 h (3000 cycles) at an ultrahigh current density of 20 mA cm^-2 and a practical areal capacity of 5 mAh cm^-2. Moreover, HBPA-g-PE separator enables a practical lithium-sulfur battery to achieve over 200-cycle stable performance with initial and retained capacity of 700 and 455 mAh g^-1, at a high sulfur loading of 4 mg cm^-2 and a low electrolyte content/sulfur loading ratio of 8 μL mg^-1.