Multifunctional Utilization of Pitch‐Coated Carbon Fibers in Lithium‐Based Rechargeable Batteries

This work reports carbon fibers as an electrode material and current collector for dual-carbon and lithium-ion batteries. Fully graphitic and semigraphitic carbon fibers undergo anion intercalation beyond 4.5 V versus Li/Li+. Symmetric dual-carbon full cells using a pitch-coated fully graphitic carbon fiber mat as both cathode and anode delivers an energy-density of 276 and 322 Wh kg(-1) at 342 W kg(-1) power density in the voltage range of 3.0-5.0 and 3.0-5.2 V, respectively. On the other hand, nongraphitic carbon fibers do not exhibit anion intercalation up to 5.2 V and can be used as a current collector. They also possess a larger number of Li+ storage sites in their randomly oriented microstructure when used as an anode. A lithium-ion full cell with double carbon-coated C-LiFePO4 loaded on nongraphitic carbon fiber as a cathode and pitch-coated nongraphitic carbon fiber as an anode exhibits 202.6 and 75.2 Wh kg(-1) energy density at power densities of 46.75 W kg(-1) and 11.7 kW kg(-1), respectively in 2.0-3.5 V range. This pitch-coated carbon fiber-based battery configuration eliminates the need for metal foils and costly fluorinated binders, lowers overall weight of the cell, and is capable of sustaining mechanical stress and thermal shock.