Mixed Polyanionic Compounds as Positive Electrodes for Low-Cost Electrochemical Energy Storage

Low-cost electrochemical energy storage systems (EESSs) are urgently needed to promote the application of renewable energy sources such as wind and solar energy. In analogy to lithium-ion batteries, the cost of EESSs depends mainly on charge-carrier ions and redox centers in electrodes, and their performance is limited by positive electrodes. In this context, this Minireview evaluates several EESS candidates and summarizes the known mixed polyanionic compounds (MPCs)-a family with robust frameworks and large channels for ion storage and migration. After comprehensive analysis, it is pointed out that a deeper exploration of MPCs may generate numerous novel crystallographically interesting compounds and excellent cathode materials for low-cost energy storage applications.