Potassium Ion Storage: Direct Structure–Performance Comparison of All‐Carbon Potassium and Sodium Ion Capacitors (Adv. Sci. 12/2019)

A hard carbon ion insertion anode gives much higher overpotential with K+ vs Na+. This significantly lowers the energy–power of symmetric hybrid potassium ion capacitors (KICs) vs sodium ion capacitors (NICs). However, high surface area, ion adsorption carbon works well with both K and Na, opening the possibility for high performance symmetric KICs. In article number 1802272, Mengqiang Wu, David Mitlin, and co-workers provide a direct performance comparison of potassium ion capacitors versus the better-known sodium ion capacitors.