Lithium Ion Capacitor with Identical Carbon Electrodes Yields 6 s Charging and 100 000 Cycles Stability with 1% Capacity Fade

Abstract

Hybrid ion capacitors are held back by the discrepancy of the fast kinetics in “capacitor-like” ion adsorption cathodes versus the sluggish kinetics of “battery-like” ion insertion anodes. We demonstrate a novel lithium ion capacitor (LIC) architecture that circumvents this problem. This is achieved by employing an identical porous carbon for both positive and negative electrodes with structure and chemistry optimized for power and cyclability. In fact, the architecture does not require a separate source of Li ions apart from the electrolyte salt, reducing the danger of large-scale Li plating and dendrite growth. An optimized device yields excellent Ragone characteristics: 127 Wh kg–1 at 332 W kg–1 (74 W h L–1 at 193 W L–1) while at the very high power of 33,573 W kg–1 the energy remains solid at 40 Wh kg–1 (23 W h L–1 at 19 472 W L–1) (based on total active material). The latter is equivalent to a 6 s full charge or discharge on par or superior in rate to classical supercapacitors. The LICs are uniquely stable, retaining 99% capacity and 100% cycling Coulombic efficiency after 100 000 cycles at 0–3.5 V. Such extended cycling lifetime has not been reported prior for any hybrid ion capacitor architecture. The biomass waste (gulfweed) derived carbon possesses porosity and pore size distribution necessary for facile ion transfer kinetics and is heteroatom doped (1% N, 8% O) to provide the needed ion adsorption capacity.