Researchers at Arizona State University have developed the use of transition metal hydroxyl anion materials (such as hydroxysulfates and hydroxyphosphates) as cathode materials for Lithium ion batteries. These materials fall into a class of materials know as polyanions. Polyanion materials have shown promising electrochemical performance as cathodes in lithium ion batteries in terms of their capacity (100-170 mAh/g), reaction potential, cyclability, and safety. However, these materials still suffer from low intrinsic charge storage capacities and poor electronic conductivity due to their intrinsic bonding and structure. A family of materials based on transition metal hydroxysulfate or hydroxyphosphate naturally occurring minerals offers the possibility for improved performance as cathode materials due to the following characteristics: (1) open framework or layered structures that can facilitate fast Li+ insertion, (2) beneficial bonding characteristics such as edge sharing MO6 octahedra for good electronic conductivity and improved rate performance, (3) flexibility in alkali and transition metal cation incorporation as observed in nature, which can allow for the design of solidsolutions to enhance structural stability, capacity, and reaction potentials, and (4) possibility for multielectron redox reactions due to the incorporation of greater than 1 transition metal per formula unit, which can result in capacities greater than 200 mAh/g.
Potential ApplicationsLithium Ion Batteries Hybrid Electric Vehicles Electric Vehicles Portable Electric Devices Renewable Energy Storage
Benefits and AdvantagesImproved charge capacity at the cathode Tailorability of designs through chemistry to optimize performance Open framework design to facilitate Lithium ion insertions