Investigation of electrochemical performance and gas swelling behavior on li4ti5o12/activated carbon lithium‐ion capacitor with acetonitrile‐based and ester‐based electrolytes

Abstract

Lithium‐ion capacitors (LICs) have gained significant attention due to the combination on the advantages of electric double‐layer capacitors (EDLCs) and lithium‐ion batteries (LIBs). Herein, the LIC pouch cell was fabricated by an activated carbon (AC) cathode and a Li4Ti5O12 (LTO) anode. Two organic electrolytes (1 mol L−1 LiBF4/acetonitrile (AN) and 1 mol L−1 LiPF6/ ethylene carbonate (EC) + ethyl methyl carbonate (EMC) + dimethyl carbonate (DMC)) were chosen and the gas swelling behavior was studied. Compared with the ester‐based LIC, the AN‐based LIC displays higher energy density of 13.31 Wh kg−1 at 11.4 W kg−1 and even provides a value of 9.1 Wh kg−1 at 1075 W kg−1. Because of the lower DC Resistance of 0.761 mΩ, the maximum power density of the AN‐based LIC reaches 12.5 kW kg−1. The AN‐based LIC delivers good stability with an energy retention of 88.3% after 900 cycles. It is discovered that the swelling behavior of AN‐based LICs is more serious and the major component is H2. The difference of swelling behavior among the LICs, lithium nickel cobalt manganese oxide (NCM)/LTO LIB and AC/AC EDLC is proposed to be caused by the AC electrode and the interfacial reaction of LTO.