Nitrogen and phosphorous co-doped hierarchical meso-microporous carbon nanospheres with extraordinary lithium storage for high-performance lithium-ion capacitors

Lithium-ion capacitors (LICs), consisting of a battery-like negative electrode and a capacitive porous-carbon positive electrode, deliver more than twice the energy density of electric double-layer capacitors. However, their wide application suffers from low energy density and reduced cycle life at high rates. Herein, hierarchical meso-microporous carbon nanospheres with a highly disordered structure and nitrogen/phosphorous co-doped properties were synthesized through a facile template method. Such hierarchical porous structure facilitates rapid ion transport, and the highly disordered structure and high heteroatom content provide abundant active sites for Li+ charge storage. Electrochemical experiments demonstrated that the carbon nanosphere anode delivers large reversible capability, greatly improves rate capability and exhibits excellent cycle stability. An LIC fabricated with the carbon nanosphere anode and an activated carbon cathode yields a high energy density of 103 W h kg(-1), an extremely high power density of 44,630 W kg(-1), and long-term cyclability of over 10,000 cycles. This work presents how structural control of carbon materials at the nano/atomic scale can significantly enhance electrochemical performance, enabling new opportunities for the design of high-performance energy-storage devices.