Defect-Anchored Carbon Nanotubes With Tailored Electronic Structure as a Single Platform for Thermal Energy Storage, Li-Ion Battery Anodes, and Thermoelectric Conversion

Heteroatom doping offers a unified and energy-efficient strategy to tailor the electronic structure of carbon nanotubes (CNTs) for multifunctional energy applications. In this study, boron-doped CNTs (B-CNTs) synthesized via a single-step arc discharge method are evaluated across four domains: thermal energy storage, photothermal conversion, lithium-ion batteries, and thermoelectric generation. The present study benefits from p-type defect formation in CNT, which includes a work function increase and a shifted Fermi level. In thermal energy storage, a paraffin/B-CNT composite demonstrated superior thermal conductivity (0.303 W/m·K), latent heat capacity (144.7 J/g), and crystallinity (51.9%) due to enhanced dispersion and nanoconfinement. For photothermal conversion, the composite exhibited a broadened absorption spectrum and achieved a high efficiency of 91.0%, nearly three times higher than paraffin/As-synthesized CNT (As-CNT) composite. As an anode in lithium-ion batteries, B-CNTs delivered a reversible capacity of 361.02 mAh/g after 100 cycles, more than double that of pristine CNTs due to improved conductivity and Li⁺ diffusion. Furthermore, in a paraffin/B-CNT-integrated thermoelectric module, enhanced interfacial heat transfer enabled stable heat-source functionality and a conversion efficiency of 0.33%. These findings demonstrate the practical potential of B-CNTs as a multifunctional material for improving performance in diverse energy storage and conversion systems.