Batteries are evolving and Li-ion battery is the chosen technology so far. Consequently, we must understand how to improve batteries performance, and the chemical analysis of their components is a necessary step. Materials for anodes, cathodes and electrolytes should be fully characterized. In this eBook, we explain how microwave-assisted digestion has become an essential ally for sample preparation of battery materials before measurements by inductively coupled plasma optical emission spectrometry. After a brief introduction to fundamentals, several procedures are presented for analysis of anode, cathode, and electrolyte materials. We are going to demonstrate how the use of microwave-assisted closed vessel digestions makes feasible the metal analysis of several components used in the Li-ion battery industry. Moreover, this approach led to shorter digestion cycles, using lower volumes of reagents and higher temperatures without compromising safety aspects.