Renewable energy sources such as solar, wind, and hydro hold the promise to meet the huge energy demands of the future at no environmental cost. Harvesting and utilization of these energies require efficient and low cost energy conversion and storage devices, whose performance essentially depends on the properties of the electrode materials. The properties of materials are greatly affected by synthesis methods and can be tuned by chemical modifications. Many approaches have therefore been developed toward this end. Among them, plasma has attracted increasing attention because of its great efficacy in producing and modifying materials under mild conditions. Herein, recent developments in plasma-assisted synthesis (e.g., plasma conversion, milling, deposition, and exfoliation) and plasma-assisted modification (e.g., plasma etching, doping, and other surface treatments) of energy conversion and storage materials are highlighted. Challenges and future opportunities in this field are also discussed. This review aims to provide a better understanding of how plasma can be utilized to synthesize and modify a variety of materials including transition metal phosphides, nitrides, chalcogenides, oxides as well as carbon materials, and to promote their additional applications in energy conversion and storage.