Na and K Ion Capacitors

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 “Potassium Ion Storage: Direct Structure–Performance Comparison of All‐Carbon Potassium and Sodium Ion Capacitors“, a direct performance comparison of potassium ion capacitors versus the better‐known sodium ion capacitors has been provided