Currently, solid-state supercapacitors becoming one of the leading alternative energy storage devices in the wearable technology, healthcare, mobile electronics, and wireless sensor network. Among all supercapacitors, pseudocapacitors are attracting attention due to higher energy density than double layer capacitors. Till now, many metal oxide and some conducting polymer electrodes have been tested to fabricate pseudocapacitive electrode based supercapacitor in the vision of improving energy density and power density. However, present work focused on the chemical synthesis of CoS2, MnS, and MoS2 thin film metal sulfide electrodes, with higher conductivity than their metal oxide counterparts to improve charge-discharge cyclic stability and energy density of supercapacitor. For the researchers working on flexible supercapacitor fabrication using thin film electrodes and polymer gel electrolyte, this book is helpful. This book will be also benefited for the readers working in the field of thin film materials synthesis by an electroless deposition method.