Surface‐Stabilized and Lightweight Metallic PET Fabrics for Flexible and Energy‐Dense Li‐Ion Batteries

Current collectors are indispensable components in flexible lithium batteries. However, commercially used current collectors are heavy and rigid, severely limiting the energy density and flexibility of the batteries. Metallic polyethylene terephthalate fabrics (MPETs) have emerged as promising alternatives due to their lightweight nature, low cost, and excellent flexibility. Despite these advantages, the chemical and electrochemical stability of MPETs under battery operating conditions remains largely unexplored. Herein, the rapid degradation mechanism of MPETs in working batteries and propose effective surface-stabilization strategies to enhance their long-term stability is systematically investigated. An electroplating-repair method is developed to fabricate etching-proof MPETs for anodes, and a phosphorus-incorporated nickel coating on PET to achieve high-voltage-stable MPETs for cathodes. Compared to commercial metal-foil current collectors, the surface-stabilized MPETs are significantly lighter -by 72.0% for the cathode current collector and 35.7% for the anode current collector, resulting in a 20% increase in battery energy density. FLBs assembled with these advanced MPETs exhibit outstanding cycling stability and maintain consistent voltage output even after thousands of bending cycles at radii as small as 1 mm. These results highlight the potential of surface-stabilized MPETs to enable the next generation of energy-dense and mechanically robust flexible lithium batteries.