This chapter will discuss the technical requirements and status of applying lithium-ion batteries to electrified vehicles. It will begin by introducing the principles of vehicle propulsion, electrified features, powertrain design, and the resulting battery chemistry applicability. An understanding of vehicle needs will enable a discussion on lithium-ion battery pack design. Once the basic layout of pack design is understood, it is necessary to appropriately size a pack to meet its intended vehicle function relative to various drive cycles and other requirements. A review of current lithium-ion technology and applicability for automotive applications will then follow. This chapter will describe existing cell energy and power performance in the context of international performance targets. The various features of cell design for automotive will also be discussed along with a review of current safety testing standards and regulations. Finally, an examination of existing commercialized products will show how the vehicle, pack and cell design principles described are implemented in actual production vehicles.