Lithium ion battery technology is ubiquitous to our world today, from our cell phones, power tools, and increasingly in our cars. For DoD, lithium ion batteries are essential to many key platforms and applications, and future demand for lithium ion battery technology is expected to continue to grow for the foreseeable future. In this lecture, we will cover the basic fundamentals of how lithium-ion batteries work, how and where they are made, and some specific design and supply chain considerations specific to Defense applications.