An order magnitude increase in energy of Li-ion capacitors by adopting combined insertion-conversion process with long durability and water soluble binder

Abstract

Lithium-ion capacitors (LICs) are one of the most promising energy storage devices with both high-energy density and high-power characteristics. Our work reports the demonstration of high energy and high power LIC assembly by introducing the combination of insertion-conversion mechanisms as a battery-type electrode with commercial activated carbon (AC) as the capacitor-type electrode. Accordingly, the conversion type copper oxide (CuO) and insertion host, graphite (RG) are formulated as composite via mechanical milling and employed as active material. Both RG and CuO have been recovered/regenerated from the anodic active material, and the Cu-foil current collector of spent Li-ion batteries is worth mentioning. The electrochemical performance of different RG:CuO composites are analyzed using two binders (PVdF, Polyvinylidene fluoride & CMC, Carboxymethylcellulose), and the CMC is found to be dominant in comparison with PVdF in the half-cell assembly. An in-situ impedance is performed to understand the interfacial properties. Prior to the fabrication of LIC, the battery-type electrode is electrochemically pre-lithiated (LiC6 + Cu0+ Li2O) and paired with the AC electrode under the balanced mass loading. The LIC with RG(50):CuO(50) anode and AC cathode rendered a maximum energy density of ∼198.7 Wh kg−1 with superior cyclic stability for 10,000 cycles. Also, the LIC is subjected to various temperature conditions (−10, 0, 10, 25, and 50 °C) to explore the feasibility of using such environments.