Electric-field Self-Regulating 3D Composite Current Collectors for Stable Flexible Lithium Metal Batteries Over...

High volumetric energy, flexible, and stable lithium (Li) metal batteries have received unprecedented attention in recent years because of their high demand in future robotics, wearable electronics, and electric vehicles. However, their development has been largely hindered by the use of thick Li metal anode and copper (Cu) current collector (CC), which inevitably trigger dendrite formation, massive volume expansion, and mechanical failure under deformation. To address these challenges, we report here a porous, electric-field self-regulating composite CC that facilitates the formation of an exceptionally dense, dendrite-free, yet mechanically flexible Li metal anode. Structured with a three-dimensional (3D) metal/ferroelectric polymer/metal sandwich architecture, the composite CC generates localized reverse electric fields to counteract the tip effect of dendrite formation. This self-regulation mechanism confines dense deposition of Li metal within the middle ferroelectric polymer framework, thereby eliminating dendritic morphology while imparting remarkable mechanical flexibility. When paired with a commercial NCM₈₁₁ cathode, the resulting full cells demonstrate an ultrahigh volumetric energy density (1183 Wh L^-1) and outstanding capacity retention (99.94 % per cycle). The battery also sustains 24 000 bending cycles without obvious capacity decay. This work demonstrates a versatile CC design strategy, paving the way toward ultrahigh-energy and flexible energy storage devices.