Functional materials with high-efficiency energy storage and conversion for batteries and fuel cells

Electrochemical energy storage and conversion with high efficiency and cleanliness is unquestionably one challenge for the sustainable development of the society of human beings. The functional materials can be applied in the systems of electrochemical energy storage and conversion such as in the fields of batteries and fuel cells. For the aspect of energy storage, high efficiency is closely connected with lightweight and high energy density materials, such as hydrogen, lithium, and magnesium. While for energy conversion, two major problems exist namely the diffusion/migration of ions and the transportation of electrons. The properties of the corresponding materials directly affect the solution of these challenges. Thus, in this review we concentrate on the crystal structures and the properties of functional materials applied in electrochemical energy storage and conversion systems with selected primary and secondary batteries and hydrogen fuel cells. In particular, the design, synthesis, structure and property of the materials, containing (1) cathode, anode and electrolyte for non-aqueous Li/Li+; (2) various Mg, MgxMo6S8 (0 < x < 2) Chevrel phase cathode and electrolyte solutions for primary and secondary Mg batteries; (3) proton exchange membranes, electrode catalysts, hydrogen production and storage for aqueous H2(H)/H+ fuel cells. The advantages and disadvantages involved in the batteries and fuel cells using functional materials are also discussed.