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Batteries will undoubtedly play critical roles in modernizing energy grids, allowing greater penetration of renewable generation and providing services that help grids function. Applying storage technology to grid applications is a business decision that requires potential revenues to be accurately measured to determine economic viability. Using models of storage connected to the California energy grid, we simulate grid-scale applications to estimate such revenues under current market conditions. All calculations are undertaken over two full years of operation of the storage device where a simulation of the grid-connected battery is undertaken so that control and decision are made in real time. Control and decision are made with data available at the time and mimics actual use as it might have happened. The use of a long period of data provides precise estimates as to the values of different applications of the battery. Each simulation results in duty cycles (power profiles) on which the cell-level batteries are tested. We examine the effects of these differing duty cycles on the efficiencies of batteries with various chemsitries. For the first time, we reveal critical tradeoffs between the battery chemistries and the applicability of their energy content, and show that accurate revenue measurement can only be achieved if realistic battery operation in each application is taken into account. The findings in this work could call for a paradigm shift on how the true economic values of energy storage devices could be assessed.

Lithium-rich layered cathode materials, where excess lithium occupies transition metal (TM) sites in the TM layer, have shown capacities well beyond commercially available traditional layered cathodes. This is largely attributed to redox behavior of oxygen within the cathode, and has recently been examined computationally1. However this increased capacity is accompanied by a high degree of irreversible capacity loss in first cycling, voltage decay, and low rate capability. This is partially attributed to an oxygen release mechanism, where oxygen vacancy formation accompanies delithiation, rather than the redox of TM ions2. Numerous methods have been attempted to prevent the release of oxygen from the lattice, including TM substitution, morphology control, and surface coating. In this work, we employ density functional theory to calculate the oxygen vacancy formation energy in layered lithium-rich nickel manganese oxide with a variety of cation dopants. Computational results elucidate the impact of doping on the system, and provide rationale for these behaviors. These calculations further describe the impact of local TM bonding environment on specific oxygen sites, rationalizing their relative vacancy formation energies. Driven by these computational results, we experimentally introduce relevant dopants into our cathode materials and observe electrochemical cycling changes commensurate with the predicted changes. Characterization methods verify the predicted oxidation states and incorporation of the relevant dopants. 1. Seo, D. et al. "The structural and chemical origin of the oxygen redox activity in layered and cation-disordered Li-excess cathode materials." Nat. Chem.8, 1–6 (2016). 2. Hy, S. et al. "Performance and Design Considerations For The lithium Excess Layered Oxide Positive Electrode Materials For Lithium Ion Batteries." Energy Environ. Sci. 9, 1931–1954 (2016).