Polymer/Inorganic-Solid Composites for Rechargeable Battery Electrolytes

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1438007 - GoodenoughThe objective of this project is the development of a new strategy for a rechargeable battery that can store energy at a price that is competitive with fossil fuels. The strategy is to develop an inexpensive thin, flexible, mechanically strong electrolyte membrane scalable at low cost to large areas that is chemically stable to temperatures above 100°C on contact with a metallic alkali metal. The PI plans to explore the design of a rechargeable battery using an alkali-metal anode to enhance the energy density and lower the cost of battery manufacture and management. The broad impact of this development would be the enabling of alternative strategy for the development of Li-ion or Na-ion batteries that can power an all-electric highway vehicle or provide storage for the grid of electrical energy generated by solar or wind energy at an affordable cost.Present strategies for Li-ion or Na-ion batteries use an organic liquid electrolyte having a lowest-unoccupied-molecular-orbital (LUMO) energy about 1 eV below the Fermi energy EF of a Li anode, 0.7 eV below the EF of a Na anode. Formation of a passivating solidelectrolyte-interphase (SEI) layer on an alkali-metal anode surface having EF LUMO causes dendrites to form and grow across the electrolyte to the cathode on repeated charge/discharge cycles; with an organic liquid electrolyte, the resulting internal short-circuit has incendiary consequences. As a result, existing Li-ion rechargeable battery cells are fabricated in the discharged state with an anode free of an alkali metal. Nevertheless, on the initial charge, a passivating SEI layer permeable to Li+ or Na+ is formed if the anode has an EF LUMO; the Li+ or Na+ of the SEI layer is supplied by the cathode, which is an insertion compound of limited solid-solution range for Li or Na. These features limit the energy density of existing cells, which makes it difficult to develop a safe battery at an affordable cost for either powering an all-electric highway vehicle or providing storage for the grid of electrical energy generated by solar or wind energy. The PI proposes to develop composite membranes in which a solid-state component is embedded in a polymer having a LUMO EF of Li0 and/or Na0. These membranes may be designed to be either a membrane separator that blocks dendrites from an alkali-metal anode or a solid electrolyte of an all-solid-state battery. The membranes can be made at low cost with easy scale-up in size; they can be thin, flexible, and mechanically robust. The separator membranes contain a main-group oxide that blocks dendrites; the solid state component of the all-solid-state battery acts as a salt releasing the working alkali ion to the polymer component that conducts the ions in its dry state.