Rational design of a pre-lithiated ionogel membrane with enhanced safety and electrochemical performances

Hard carbon is hard to be commercialized due to its low initial efficiency. The irreversible capacity loss usually consumes numerous lithium ions from the electrolyte, leading to an unexpected energy density attenuation. Therefore, effective pre-lithiation methods are extremely desired. Herein, a striking and simple pre-lithiated method was proposed through introducing lithium metal passivation powder into ionogel electrolyte as lithium source. Safety features and electrochemical performances of as prepared ionogel electrolyte were studied systemically. Notably, our work found that the incorporation of lithium metal powder could effectively improve the ionic conductivity, reduce the reactive activation energy, and supplement the lithium-ion loss of electrolyte. The pre-lithiated electrolyte could stand an ultra-high operating potential window of 4.2 V in lithium-ion capacitors. Moreover, our study reveals that the dissociation of the ionic clusters within the ionogel electrolyte favors the electrochemical performances at high temperature. Our optimized device delivered a maximum energy density of 138 Wh kg −1 and a maximum power density of 19339.4 W kg −1 at 60 °C. This simple pre-lithiation method will significantly benefit the rational fabrication of lithium-ion capacitors with high energy density and reasonable safety. Broader context: A new and simple pre-lithiated strategy was proposed through introducing lithium metal passivation powder into ionogel electrolyte to replenish the consumed lithium ions on hard carbon component. The optimized quasi-solid-state lithium-ion capacitor possessed an ultra-high operating potential window of 4.2 V and exhibited excellent electrochemical performance. This method will significantly benefit the rational fabrication of lithium-ion capacitors with high energy density and reasonable safety. • A new and simple pre-lithiated ionogel electrolyte method was developed. • The operating potential of optimized lithium-ion capacitor was expanded to 4.2 V. • The optimized lithium-ion capacitor exhibited ultra-high energy density and safety.