Orchestrating lithiophilic surface chemistry of carbon cathodes for high-power Li-ion capacitors

Activated carbon (AC) is widely used as the cathode in Li-ion capacitors (LICs), yet its low affinity for Li + ions limits high-rate performance and cycling stability. In this study, lithiophilic AC cathodes are engineered by controlling the chemical state and surface distribution of Li-containing species via lithium formate treatment followed by temperature- and concentration-controlled heat processing. Distinct surface species, including Li-COO − , Li 2 CO 3 , and Li 2 O, are selectively formed as a function of heat-treatment temperature while preserving the intrinsic microporous carbon framework. Among these species, Li 2 CO 3 formed at 500 °C provides the most favorable balance between Li + adsorption capability and interfacial stability, enabling pronounced capacitor-like behavior and reduced resistance under high-rate operation. Further optimization of the Li precursor concentration shows that a medium surface loading of Li 2 CO 3 achieves uniform surface coverage while maintaining micropore accessibility, leading to improved rate capability and long-term stability in half-cell configurations. The optimized cathode is further validated in a pouch-type LIC full cell employing a pre-lithiated graphite anode, delivering markedly enhanced high-rate performance and cycling stability compared with pristine AC. This work establishes a structure–chemistry–performance relationship for Li-modified AC cathodes and highlights interfacial control of Li species as an effective strategy for high-performance LICs.