Highly Conductive, Light Weight, Robust, Corrosion‐Resistant, Scalable, All‐Fiber Based Current Collectors for Aqueous Acidic Batteries

Abstract Lithium‐ion batteries (LIBs) are integral parts of modern technology, but can raise safety concerns because of their flammable organic electrolytes with low flash points. Aqueous electrolytes can be used in LIBs to overcome the safety issues that come with organic electrolytes while avoiding poor kinetics associated with solid state electrolytes. Despite advances in aqueous electrolytes, current collectors for aqueous battery systems have been neglected. Current collectors used in today's aqueous battery systems are usually metal‐based materials, which are heavy, expensive, bulky, and prone to corrosion after prolonged use. Here, a carbon nanotube (CNT)–cellulose nanofiber (CNF) all‐fiber composite is developed that takes advantage of the high conductivity of CNT while achieving high mechanical strength through the interaction between CNT and CNF. By optimizing the CNT/CNF weight ratio, this all‐fiber current collector can be made very thin while maintaining high conductivity (≈700 S cm −1 ) and strength (>60 MPa), making it an ideal replacement for heavy metal current collectors in aqueous battery systems.