A review on potential biopolymer nanocomposites in energy storage devices

Abstract

The requirements for energy storage devices (ESD) are extended cycle life, high energy density, and improved performance. The working pattern of batteries suffers from corrosion and dendrite formation, on the other hand, the advancements of supercapacitors lag a high energy density. Both batteries and supercapacitors should be packed well to avoid the leakages of toxic materials. A high porosity in biopolymers supports efficient transport of ions in the device. Polymer electrolytes using biopolymer are attracted more because it is abundant and more economical. They have positive features of higher electrical conductivity, mechanical strength, and biodegradable. The functional groups in biopolymers are, carboxyl, hydroxyl, and amine help to achieve a high energy density. The challenge with scavenging the synthetic polymer wastes from ESD that can overcome by utilizing biopolymers. Biopolymers derived carbon materials produce higher surface area and can be easily doped with hetero atoms, which helps to produce an ESD with higher capacitance. Among biopolymers, cellulose, chitosan, starch and their nanocomposites attracted the scientific community for the preparation of electrodes, separators, electrolytes and binders for energy storage. Since the surface area and porosity are the most important parameters that affect the electrochemical performance, they can be harvested from natural polymers. Biopolymers are easy to process due to their solubility in water which can avoid the usage of more organic solvents. They can be produced from agricultural or biological wastes and can be decomposed in a safe manner. Biopolymers are generally non-conducting and need conductive materials, such as metal salts, carbon materials and metal oxides as fillers. It is also a challenge to achieve homogeneous dispersion of nanoparticles over the polymer matrix and maximum electrical conductivity. They exhibit limited electrochemical window and degrade when used for a greater number of cycles. There is an urgent need to improve the compatibility between the matrix and the filler. Biopolymers used for the fabrication of flexible or wearable devices still need improvements in their mechanical and electrochemical properties. More standardized fabrication processes are to be introduced to turn laboratory/batch scale into pilot-scale production with more reproducibility.