Carbon-Supply-Programmed CNT Growth for Ultrathin Microwave Absorbers from Waste Batteries and Plastics

The rapid expansion of 5G/6G communication networks has intensified the demand for lightweight, efficient, and broadband microwave absorbing materials (MAMs) to mitigate electromagnetic pollution. Co-upcycling spent lithium-ion batteries and plastic waste into high-value functional materials represents a sustainable pathway but requires precise control over carbon nanostructure formation. Here, we introduce a carbon-supply-driven kinetic regulation strategy to program carbon nanotube (CNT) growth during the one-step co-pyrolysis of waste nickel cobalt manganese oxide (NCM) cathodes and low-density polyethylene (LDPE). We demonstrate that the NCM/LDPE mass ratio serves as a key parameter to regulate local carbon flux, thereby continuously tuning CNT elongation while inducing a volcano-type evolution of the defect-related Raman intensity ratio (I D /I G ). This non-monotonic behavior reveals an intrinsic competition between graphitization and defect generation, whose optimal balance is crucial for microwave absorption. The optimized sea urchin-like architecture (NCC-6.7) integrates an interconnected conductive network for conduction loss with abundant structural defects and heterogeneous interfaces for dipolar polarization, achieving a remarkable minimum reflection loss of − 63.45 dB at an ultrathin thickness of 1.63 mm and an effective absorption bandwidth of 4.25 GHz at 1.46 mm. Moreover, the NCC-6.7-derived textile exhibits enhanced corrosion resistance, reduced electromagnetic scattering, and excellent mechanical flexibility. This work establishes a kinetics-structure–property paradigm for designing advanced composite absorbers, and the resulting textile demonstrates great potential for flexible electromagnetic protection and marine applications. This work not only provides a practical route for valorizing mixed solid wastes but also offers new opportunities for sustainable electromagnetic pollution mitigation.