Ultralight Ionic and Electronic Conducting Current Collector with Durable Interface for High‐Performance Thick Gradient Electrodes

Abstract The advancement of lithium‐ion batteries (LIBs) is constrained by limitations in energy density and cycling stability, highlighting the need for innovations in current collectors and electrode architectures. Traditional metal current collectors (TMCCs), such as copper and aluminum foils, contribute significantly to battery weight, block lithium‐ion transport, and ultimately reduce energy density. To overcome these challenges, an ultralight, ultrathin, and porous carbon nanotube yarn film is introduced as a porous current collector (CNT‐PCC). The CNT‐PCC enables efficient electrolyte infiltration and facilitates both ionic and electronic transport, resulting in substantial improvements in energy density and rate capability. Its rough surface, enriched with functional groups, enhances interfacial adhesion, lowers resistance, and significantly boosts long‐term cycling stability—with a 78.2% increase in capacity retention after 1000 cycles compared to TMCC‐based systems. Moreover, CNT‐PCC supports the construction of gradient‐structured thick electrodes by stacking layers with tailored ratios of active materials and porosity. This gradient design, which increases porosity away from the separator, reduces polarization and enables more uniform Li ⁺ distribution, leading to a 26.5% capacity improvement at 2C. CNT‐PCC is compatible with a range of cathode and anode materials, offering a scalable and promising strategy for next‐generation high‐performance LIBs.