Ultralight Polymer‐Based Current Collectors With Enhanced Transverse Conductivity via 3D Conductive Interlayers for Safe and High‐Energy Lithium‐Ion Batteries

Abstract Compared to commercial current collectors (CCs), polymer‐based current collectors (PBCCs) significantly enhance the energy and safety of lithium‐ion batteries. However, the inherent transverse non‐conductivity of traditional PBCCs necessitates the use of complex welding processes during cell assembly thus sacrificing the energy density, stemming from the insulating nature of the intermediate polymer layer in PBCCs. Here, newly designed PI‐CNTs‐Al and PI‐CNTs‐Cu PBCCs are developed by integrating highly conductive carbon nanotubes (CNTs) into the polymer interlayer, which is coated with two metal layers to facilitate longitudinal conductivity. The incorporation of CNTs forms a 3D conductive network within the interlayer, substantially improving the transverse conductivity of PI‐CNTs‐Al and PI‐CNTs‐Cu from 2.19×10 −9 and 1.89×10 −9 S m −1 to 1.02 and 1.15 S m −1 . Furthermore, the addition of CNTs enhances the bonding strength at the metal‐polymer interface, effectively mitigating separation defects commonly observed in traditional PI‐Al and PI‐Cu CCs. The engineered PBCCs can be utilized directly as CCs for cell assembly without complex conductive components. Importantly, the fully charged 1.5 Ah cell, achieving an energy density of 235.8 Wh kg −1 with a 9.0% improvement, successfully endures rigorous needling tests, which can be attributed to the enhanced tensile strength and reduced fracture strain ratio of the PBCCs.