Novel Low Voltage, High Areal Capacity Lithium-Magnesium-Silver Film Alloys for Lithium Ion Batteries of Wide Solid Solution Range

Next generation negative electrode materials have received increased attention as performance demands of Li-ion battery technology continue to rise. Commonly used graphite anodes fall short in meeting rising energy demands. The use of Li alloying materials as negative electrodes may help to meet these demands given large increases in theoretical capacities, especially through the incorporation of Si, Mg, Ag, and Ge components. However, despite the advantages in energy density, these materials suffer from significant mechanical stresses during Li alloying reactions. Thus, practical use of these materials may require the incorporation of composites or other highly engineered voluminous morphologies, limiting their usefulness in practical settings. Herein, we’ve demonstrated the first utilization of Li:Mg:Ag based thin film compositions without requiring additional processing, binders, additives or excess porosity, which are deleterious to volumetric energy. These optimized compositions have been shown to achieve high cyclability, improved transport, and high-capacity retention vs lithium containing and non-containing LCO (LiCoO 2 ) and NTPO (Nb x Ta x PO 5 ) cathode materials. More specifically, a “Li 2 AgMg” Heusler related compound of significant solid solution has been identified and positively correlated to improved performance. Fabrication, electrochemical results, and initial insights into the lithiation reaction mechanism of these ternary “Li 2 AgMg” related phases in lithium-ion batteries are discussed.