Li₂RuO₃ as an Additive for High-Energy Lithium-Ion Capacitors

A high-energy lithium ion capacitor that has Li₂MoO₃ as an alternative lithium source instead of metallic lithium has been proposed. For further improvement, we suggest Li₂RuO₃ as a new additive to improve the energy density in the positive electrode. The choice of Li₂RuO₃ is made based on its highly reversible characteristics for Li⁺ insertion and extraction and its structural stability in the operating voltage window of advanced lithium ion capacitors. The electrochemical and structural properties of Li₂RuO₃ have been thoroughly investigated to demonstrate its potential use in lithium ion capacitors. The high reversibility of Li₂RuO₃ and the metallic feature of Li_2–xRuO₃ may be responsible for improvements in the volumetric energy density and safety. This versatile approach may yield higher energy density without significant power loss in lithium ion capacitors.