This program establishes fundamental science for the synthesis of battery materials from natural resources, enabling a new ‘separation-by-synthesis’ paradigm for energy storage manufacturing. It addresses outstanding knowledge gaps related to synthesis in multicomponent systems with a minimum of seven or more elements, for which manifold component interactions control driving forces and transformation pathways in complex ways, and governing relationships are impossible to visualize or intuit in their entirety. The scientific basis for ‘separation-by-synthesis’ is demonstrated by synthesizing a new class of impurity-tolerant high entropy disordered rocksalt (DRX) lithium cathode materials directly from lithium ores. This novel approach to battery material synthesis reactions will bypass nearly all the purification steps that contribute to the current carbon footprint of conventional battery cathode manufacturing. Molten fluoride salts are selected among many potential synthesis media, both because they enable excess lithium and fluorine chemistry that can improve the performance of cathodes and because they offer many orthogonal degrees of freedom to control synthesis via temperature, composition, kinetics, and electrification.