Multinary alloy electrodes for solid state batteries II. A new LiSiMg alloy negative electrode material for use in high energy density rechargeable lithium cells

Electrochemical coulometric titration has been used to explore the electrode properties of a ternary LiSiMg alloy composition. The measured electrode potential and lithium capacity for this system are comparable to those estimated from consideration of the isothermal Gibbs triangle for the ternary system. These measured values are far higher than those of the state-of-the-art binary systems currently employed in thermal batteries. For example, measured electrode potentials for the ternary alloy at 440 °C were about 90 mV more negative than those for the conventional 44 wt.% LiSi binary alloy, translating to a loss of only about 70 mV compared to pure lithium. Consequently, the maximum specific energy (considering active materials only) of a cell employing this material as the negative electrode component with a hypothetical cathode (say, one lithium in 60 g of active material) which is 2.0 V positive of pure lithium should be about 35% higher than that of a comparable cell using the 44 wt.% LiSi binary alloy.