Phosphorus‐Functionalized Graphene for Lithium‐Ion Capacitors with Improved Power and Cyclability

Herein, we report an easy approach for the preparation of graphene‐based materials suitable as electrodes for lithium‐ion capacitors (LICs). To the best of our knowledge, this is the first time that phosphorus‐functionalized graphene oxide (rGO800‐P) is used as negative (battery‐type) electrode in LICs technology. An activated carbon derived from the pyrolysis of graphene‐carbon composite served as positive (capacitor‐type) electrode. While phosphorus functionalization on the negative electrode enables fast Li+ kinetics during insertion/extraction processes, the flat‐shaped morphology, large surface area and proper pore size distribution of the positive electrode enhance the double‐layer formation. Full LICs optimization, oversizing the negative electrode allows operating in the extended voltage window of 1.5–4.5 V delivering high energy and power values (91 Wh kg−1AM at 145 W kg−1AM and 33 Wh kg−1AM at 26,000 W kg−1AM) without compromising the cycling performance (76 % capacitance retention after 10,000 cycles). Power boost: Phosphorus functionalization greatly improves the anode performance accelerating Li+ kinetics in Li‐ion capacitors. The flat‐shape morphology and large surface area enable double‐layer formation in the cathode. An anode‐to‐cathode mass ratio of 3 : 1 allows high voltage operation of the cell in the 1.5–4.5 V voltage range, preventing lithium plating and delivering high gravimetric energy and power densities.