Molecular-Level Anion and Li<sup>+</sup> Co-Regulation by Amphoteric Polymer Separator for High-Rate Stable Lithium Metal Anode
Shizhen Li, Hangqi Yang, Mengzi Geng, Hainam Do, Chuang Peng
Abstract
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 -NH 2 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 .