Sodium-ion capacitors with superior energy-power performance by using carbon-based materials in both electrodes.

Na-ion capacitors (NICs) are promising energy storage devices in virtue of their merits in combining the high energy densities of secondary batteries and the high power densities of supercapacitors. However, it is still very challenging to achieve a balanced energy-power performance in NIC device due to the kinetic imbalance between the battery-type anode and the capacitive-type cathode. In this work, an NIC device based on carbon materials for both anode and cathode has been reported. As-prepared (polyimide/graphene oxide)-derived carbon (PIGC) anode material shows excellent rate capability, which can deliver a specific capacity of 110 mAh g−1 at high current densities of 5 A g−1. In addition, the N, B co-doped expanded reduced graphite oxide (NBEG) cathode demonstrates a high specific capacitance of 328 F g−1. Due to the improved rate capability of PIGC anode and specific capacitance of NBEG cathode, the imbalance on the energy and power densities between anode and cathode is well addressed. As-assembled PIGC//NBEG device can deliver an energy density of 55 W h kg−1 even at a high power density of 9500 W kg−1. The energy-power properties of PIGC//NBEG are superior to many state-of-the-art NIC devices that using carbon or non-carbon based electrodes. This work offers not only a promising device configuration with superior energy-power properties, but also a guidance for the design strategies on electrode materials for high-throughput energy storage systems. Image 1 • Carbon-based materials were used in both electrodes for sodium ion capacitors. • The imbalance on the energy/power densities of anode and cathode is well addressed. • PIGC//NBEG delivered an energy density of 55 W h kg−1 at a power density of 9500 W kg−1. [ABSTRACT FROM AUTHOR]