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

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 LiFePO₄ 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.