Solid electrolyte based on succinonitrile and LiBOB

This paper reports physical and electrochemical properties of a solid electrolyte for lithium batteries formed by doping a plastic crystal solvent, succinonitrile, with lithium bioxalato borate (LiBOB). Thermal properties, solubility limits, conductivity, compatibility with lithium, and range of electrochemical stability have been studied. Succinonitrile doped with 4 mol % LiBOB is a solid at room temperature and melts near 50°C. Electrochemical cells employing either LiFePO4 or Li1.2 Mn0.4 Ni0.3 Co0.1 O2 as the active cathode material and lithium metal as the anode were evaluated. This solid electrolyte showed excellent performance when combined with a LiFePO4 cathode, delivering a reversible discharge capacity of ∼142 mAh g-1 with very good capacity retention. However, with the Li1.2 Mn0.4 Ni0.3 Co0.1 O2 cathode, the cell's capacity retention was not as good exhibiting a discharge capacity that decreased from 194 mAh g-1 in the first cycle to 149 mAh g-1 at 20th cycle.