Metal ion capacitors (MICs) are foreseen to be a complementary alternative of vital importance to current energy storage issues, coupling high energy density delivered by batteries with high power/long cycle life offered by supercapacitors. The prime issues in realising this technology are pre-metallation and replacement of graphite electrodes that bring about an energy gain at the expense of power. Herein we present an easy-to-scale-up approach, combining activated carbon with a highly efficient and industrially compatible low-cost sacrificial salt (dimetal squarates) that can be used as a metal source for pre-metallation. Paired with a hard carbon electrode tailored to perform at high rates, lithium, sodium and potassium MICs are demonstrated. Furthermore, the successful fabrication of a lithium ion capacitor (LIC) pouch cell prototype with high energy at high power densities showing capacitance retention over 84% after 48000 cycles validates the strategy. This breakthrough may trigger the easy and low-cost fabrication of LICs and significantly reduce technological barriers to market growth and consolidation.
