Safe , Inexpensive , Long Life , High Power and Efficiency Batteries For Grid Scale Energy

New types of energy storage are required in conjunction with the deployment of renewable energy sources and their integration with the electrical grid. A new kind of energy storage technology is needed for short-term grid storage applications, as existing technology struggle to meet the needs of these applications at a reasonable price. We previously introduced a new family of cathode materials involving the reversible insertion of cations into materials with the Prussian Blue open-framework (OF) crystal structure. We showed that copper hexacyanoferrate (CuHCF) electrodes are particularly promising because of their ultra-long cycle life, high power, highenergy efficiency, and potentially, a very low-cost. OF structure cathodes are ideally paired with an anode that has comparable cycle life and kinetics to avoid a substantial constraint in the performance of the full battery. In the past year, we have made progress in this area by developing two different classes of anode materials: a novel hybrid activated carbon/polypyrrole anode, which has the high rate capability of an ultracapacitor and the well-defined potential of a battery electrode and a newly developed manganese hexacyanomanganate open-framework anode. By combining these novel anodes with CuHCFe we introduced new types of safe, fast, inexpensive, long-life aqueous electrolyte batteries. These properties make them attractive for grid-related applications. We have also demonstrated divalent ions insertion in OF materials. Searching for battery materials for divalent ion interaction is an exciting direction to enable potentially low-cost battery for grid-scale storage. We have shown that materials like nickel hexacyanoferrate (NiHCF) and CuHCFe, can reversibly intercalate aqueous alkaline earth divalent ions such as: Mg2+, Ca2+, Sr2+, and Ba2+. Our results represent a step forward and pave the way for future development in divalent intercalation batteries. Introduction Renewable energy such as solar and wind will be increasingly used in the future to address the climate change and energy dependence problems. Gridconnected electrical energy storage is important for enabling full utilization of renewable electricity generation from solar and wind energy-harvesting devices connected to grids, largely due to the fluctuations of devices on multiple time scales. Electrochemical energy storage technologies such as batteries and electrochemical capacitors are promising but the cost in terms of $/kWh is too high.