Optimization of mass matching and organic electrolytes for Li-ion hybrid supercapacitors based on LiMn₂O₄ cathode and AC anode with commercial-level mass loading

Lithium-ion hybrid supercapacitor, composed of a capacitor-type electrode and a battery-type electrode, has the potential to deliver high energy density and high power density simultaneously. In addition to electrode materials, mass matching and electrolyte are also critical to the design of a practical lithium-ion capacitor (LIC). Here, we designed commercially available pouch-type lithium-ion hybrid supercapacitors based on lithium manganate oxide (LMO) cathode and activated carbon (AC) anode with commercial-level mass loading. To optimize the performance of the LIC, meticulous mass match and electrolyte study have been performed not only in terms of energy and power densities, but also from the perspective of low-temperature performance, cycle stability, and operating voltage. Optimized LIC, using a cathode/anode mass ratio of 1/1 and an acetonitrile-based electrolyte, shows a good rate capability with 65.3% of the capacity retained even at a high C-rate of 50 C and an outstanding low-temperature performance with 46.3% of the capacity remained at −40 °C. This LIC cell delivers a maximum energy density of 9.7 W h kg⁻¹ and a maximum power density of 8198 W kg⁻¹ within an upper limit voltage of 2.3 V, and retains 82.8% of the initial energy at 1.0~2.3 V after 12,000 charge-discharge cycles. Moreover, enhancing the operating voltage to 3.1 V, the LIC cell displays a higher energy density of 13.9 Wh kg⁻¹ with 59.3 Wh kg⁻¹ of the energy density based on active materials. And the LIC cell still holds 79.1% of its initial energy at a wide working voltage of 0.5~2.5 V after 5000 cycles.