Ion Enrichment‐Mediated Charge Transfer in CNTs‐Based Films for Infrared Electrochromism

In response to a rapidly changing background environment, carbon nanotubes (CNTs)‐based infrared electrochromic materials have emerged as a research focus due to their fast response kinetics and high flexibility. Nevertheless, the microscopic mechanism governing the relationship between infrared emissivity and applied bias voltage remains vague. In this work, a defect‐engineering strategy is employed to fabricate sulfur/nitrogen co‐doped CNTs (SNCNT) films as a model system for mechanism investigation. It is revealed that the core process lies in ion enrichment‐mediated charge transfer, regulating macroscopic conductivity. Specifically, accumulated ions can dynamically reconstruct the film architecture, facilitating ion–electron interactions within an electrical double‐layer capacitive framework. This process presents an asymmetric operation mechanism that anions induce hole doping, while cations promote electron doping. First‐principles calculations further correlate ion‐specific modulation with orbital energy depth and π‐conjugation degree. By integrating these insights, a multi‐dimension qualitative model is proposed to correlate infrared emissivity with interfacial contact resistance, charge‐transfer dynamics, and atomic‐scale structure. The optimized SNCNT film system demonstrates an infrared modulation width of Δε = 0.601, accompanied by notable bia‐removal memory behavior (Δε/Δ t = −0.0018 s −1 ), underscoring its potential in infrared camouflage, information encryption, and electromagnetic shielding.