This book is a collection of experimental reports that have been presented both in national and international symposia. Mostly papers in Bahasa Indonesia and the author rewrite the paper in English, so it is not exactly the same as the origin. Rewriting of these papers also aims to make this book more systemic and coherent. Most research subjects are mainly LiFePO4 cathode materials. Some chapters contain electrolyte materials, the characterization of these materials that have been sold commercially and a paper on test performance of commercial battery.