The cathode is the positive electrode in a battery. During the discharge process of the battery, reduction occurs at the cathode. The expression discharge is used for the process in which the battery provides electric energy to an external load.
The selection of cathode materials used in commercial lithium-ion batteries is typically based on Li+ ion de-insertion/insertion reactions. Conversion reaction materials, mainly binary metal fluorides e.g. CoF2, are still in the early stage of development. Within the group of de-insertion/insertion materials, the conventional cathode materials include layered compounds LiMO2 (M = Mn, Co, Ni, etc.), spinel compounds LiM2O4 (M = Mn, etc.), olivine compounds LiMPO4 (M = Fe, Mn, Co, Ni, etc.) and their derivatives.