Stress‐Matching Molecular Bridge and 3D Micro‐Nano Array for High‐Performance, Lightweight Composite Copper Current Collectors

Abstract

ABSTRACT Compared to dense copper foil current collectors, polymer‐based composite copper foils (CCFs) significantly enhance the energy density of lithium batteries. However, conventionally fabricated CCFs via a two‐step process suffer from poor interfacial adhesion due to stress mismatch between the sputtered and electroplated copper layers, along with incomplete coverage of the polymer substrate. Herein, we propose a synergistic strategy combining molecular self‐assembly and micro‐nano electroplating to fabricate a lightweight three‐dimensional CCF. Theoretically screened trithiocyanuric acid serves as a dual‐functional “molecular bridge”: its thiol groups form strong Cu‐S bonds with copper, while its triazine core anchors to the exposed polyethylene terephthalate substrate via π–π stacking and hydrogen bonding, creating a robust and strain‐relieved interface. Integrated with a low‐temperature electrodeposited 3D micro‐nano conical array, the molecularly engineered CCFs exhibit an eightfold higher specific surface area, which effectively suppresses dendrite growth. When paired with an LiFePO 4 cathode (N:P = 3), the full cell demonstrates exceptional cycling stability (398 cycles at 1C) and rate capability. Notably, as a lithium‐free anode coupled with a high‐voltage NCM811 cathode, the cell maintains stable operation for over 100 cycles (the control cells fail within 60 cycles). This work provides a general molecular‐interface strategy for developing high‐performance, lightweight current collectors.