Optimizing Ion Desolvation Process in Carbonate-Based Electrolytes for Enhanced Performance of Lithium-Ion Capacitors

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Next-generation supercapacitors, lithium-ion capacitors (LICs), are generally limited by the much lower specific capacity of capacitive cathodes than that of the Li-insertion type anode due to the low capacitance contribution of solvated ions stored in large pores and the sluggish transfer of desolvated ions stored in small pores. Hence, a model system of porous carbons with a willfully tailored pore structure for the systematic study of capacitive cathodes is the key to further developing LICs. Herein, a series of porous carbons with tailored pore size distributions in 0.5–4 nm are synthesized through the dynamic template effect and molten salt etching of CuCl using l -glutamic acid as the carbon precursor. The electrochemical tests indicate the accessibility of desolvated ions (Li + and PF 6 – ) in 0.56 nm sized ultramicropores to contribute a high surface-area-normalized capacitance. Furthermore, the transfer kinetics of desolvated ions can be effectively accelerated by combining the utilization of 1–1.5 nm micropores without filling massive electrolytes in the pores. Finally, after matching the porous carbon cathodes with a hard carbon anode, the optimization of pore size distribution is proved to significantly boost the energy density of the device.