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.