For decades, improvements in electrolytes and electrodes have driven the development of electrochemical energy storage devices. Generally, electrodes and electrolytes should not be developed separately due to the importance of the interaction at their interface. The energy storage ability and safety of energy storage devices are in fact determined by the arrangement of ions and electrons between the electrode and the electrolyte. In this paper, the physicochemical and electrochemical properties of lithium-ion batteries and supercapacitors using ionic liquids (ILs) as an electrolyte are reviewed. Additionally, the energy storage device ILs developed over the last decade are introduced.

In this study, a novel inorganic separator, porous anodic aluminum oxide (AAO), is introduced for a rechargeable lithium ion battery system. The highly ordered AAO gives rise to an ideal structure for battery separators with appropriate porosity (67.4 %), extremely low tortuosity, and thermal durability. The prepared AAO separator has average pore sizes of 75 nm and thickness of 54 μm, which leads to enhanced ionic conductivity (2.196 mS cm⁻¹), discharging capacity at high current rates (20.13 mA h g⁻¹ at 10 C), and capacity retention (82.9%). Moreover, a computer simulation (COMSOL) model shows that the ideal AAO separator structure induces stable lithium ion battery operation in wide ranges of current rate, due to effective suppression of Li dendrite formation. The AAO separator has a strong potential in massive energy storage systems and electric vehicles.

A novel lightweight three-dimensional (3D) composite anode for a fast-charging/discharging Li-ion battery (LIB) was fabricated entirely using one-dimensional (1D) nanomaterials, i.e., Cu nanowires (CuNWs) and multi-walled C nanotubes (MWCNTs). Because of the excellent electrical conductivity, high-aspect ratio structures, and large surface areas of these nanomaterials, the CuNW-MWCNT composite (CNMC) with 3D structure provides significant advantages regarding the transport pathways for both electrons and ions. As an advanced binder-free anode, a CuNW-MWCNT composite film with a controllable thickness (~600 μm) exhibited a considerably low sheet resistance, and internal cell resistance. Furthermore, the random CuNW network with 3D structure acting as a rigid framework not only prevented MWCNT shrinkage and expansion due to aggregation and swelling but also minimized the effect of the volume change during the charge/discharge process. Both a half cell and a full cell of LIBs with the CNMC anode exhibited high specific capacities and Coulombic efficiencies, even at a high current. More importantly, we for the first time overcame the limitation of MWCNTs as anode materials for fast-charging/discharging LIBs (both half cells and full cells) by employing CuNWs, and the resulting anode can be applied to flexible LIBs. This innovative anode structure can lead to the development of ultrafast chargeable LIBs for electric vehicles.

4 V-operated all solid symmetrical supercapacitors that employ mixtures of various weight compositions with c-P₄VPh and EMITFSI electrolytes have been demonstrated and characterized.