Multifunctional flexible carbon fiber felt@nickel composite films with core–shell heterostructure: Exceptional Joule heating capability, thermal management, and electromagnetic interference shielding

[Display omitted] •A novel, flexible core–shell heterostructure has been created.•Impressive electrothermal capability is achieved at ultra-low voltages (≤1.5 V).•Robust electrothermal stability and reliability are demonstrated.•A linear model for precise thermal control is established.•Superior EMI shielding capability and high LOI manifest its versatility. Flexible electrothermal materials with multifunctionality have gained paramount importance in both industrial and everyday settings. Nevertheless, achieving exceptional electrothermal performance at ultra-low actuation voltages remains an imposing challenge. This research addresses this challenge by introducing a novel core–shell heterostructure. The unique design incorporates carbon fiber felt (CFF) as the core and envelops it with nickel (Ni) particles through electroplating. The giant core–shell heterostructure endows CFF@Ni to achieve impressive heating temperatures of up to 146.7 °C at only 1.5 V. A proposed linear model offers precise thermal control by correlating saturation temperature with the square of applied voltages. CFF@Ni exhibits rapid heating rates up to 35.8 °C/s, surpassing previous reports, and also possesses robust bending durability and reliable electrothermal characteristics. The electrothermal mechanism analysis manifests that the synergy of enhanced electrical conductivity and the unique heterostructure enables efficient electricity-to-heat conversion. Versatility is demonstrated in diverse applications, from rapid liquid heating to de-icing and thermal therapy. Notably, CFF@Ni excels in microwave shielding and flame retardancy, marking it as an excellent multifunctional material. This research significantly advances the landscape of electrothermal materials, offering a promising avenue for practical, efficient, and durable electric heating solutions that can be applied across various fields.