3D Porous Silver Nonwoven Mat Prepared with Cellulosic Templates and Spray Equipment for Supercapacitor Current Collectors

Abstract

Supercapacitors are energy conversion devices with higher power density compared to batteries and higher energy density compared to common capacitors.[1] These particular properties have attracted considerable attention with regard to numerous applications in such diverse fields as power electronics, military equipment, and hybrid electric vehicles (i.e. HEVs, in order to help the stop and go function and to provide peak power for improved acceleration).[2] In addition, supercapacitors can play an important role in complementing the energy storage functions of batteries and fuel cells by providing back-up power supplies to protect against power disruptions.[3,4]Supercapacitors have four major components, namely, current collectors, electrodes, electrolytes and separators.[3] However, although electrodes have been actively studied, there are far fewer studies of current collectors than the other there components. Typical current collectors are nickel (Ni), platinum (Pt), gold (Au), aluminum (Al), silver (Ag) and copper (Cu). Although Ag compared with the other materials offers many advantages including high current-carrying capability (i.e., lowest resistivity at 1.63 x 10-8 Ωm)[5] and good chemical and thermal stability,[6] Ag current collectors are rarely used in supercapacitors. In our previous study, which demonstrated the usefulness of a solution processed Ag current collector in supercapacitors, we used a 2-dimensional (2D) Ag plated polymer film as the current collectors.[7] In this study, we propose a method of enhancing the usefulness of a solution processed Ag current collector by making a 3-dimensional (3D) porous Ag nonwoven mat current collector from the cellulosic template in order to maximize the efficiency of the Ag current collector. This may have the result of maximizing the contact area between the electrode and the electrolyte, such as Ni foam.[8] This 3D porous Ag nonwoven mat would be also useful in such applications as the cathodes of alkaline fuel cells owing to its good chemical and thermal stability,[9] and might also be used in a variety of filtration applications where the antimicrobial and antibacterial properties of silver make silver membranes a very efficient filtration system.[10]In this study, we propose a simple method of making a 3D porous silver nonwoven mat as the current collector of supercapacitors, and investigate their super-capacitive properties using cyclic voltammetry in 1 M Na2SO4. For the purpose of comparison, the electrochemical properties of the 2D Ag plated current collector were also investigated. Cellulosic templates were used to make a 3D porous Ag nonwoven mat as the current collector of a supercapacitor with an Ag nanoparticle dispersed solution and simple spray equipment.