Better solid electrolytes need to be developed in order to achieve the long envisioned all-solid-state lithium batteries. This new generation of batteries is expected to improve the safety of Li-ion batteries while achieving both high power and high energy density. Among solid electrolytes, Li9.6Si1.74P1.44S11.7Cl0.3 is particularly promising. In order to enhance its transport properties, we have doped the solid electrolyte with CuO nanoparticles. XRD crystallography studies provided evidence of the structural changes undergone by the material. The doped and undoped solid electrolytes were tested in coin cell batteries with Li and Graphite electrodes. Cyclic voltammograms and charge-discharge data were obtained. The results indicate that CuO doping caused an improvement in the transport properties of the solid electrolyte. More cycling is underway in order to study the stability of the solid electrolyte and the structural changes undergone during cycling.