Electronic Conductivity of Lithium Solid Electrolytes

Abstract While significant efforts are being devoted to improving the ionic conductivity of lithium solid electrolytes (SEs), electronic transport, which has an important role in the calendar life, energy density, and cycling stability of solid‐state batteries (SSBs), is rarely studied. Here, the electronic conductivities of three representative SEs, including Li3PS4, Li7La3Zr2O12, and Li3YCl6, are reported. It is reported that the electronic conductivities of SEs are overestimated from the conventional measurements. By revisiting direct current polarizations using two‐blocking‐electrode cells and the Hebb‐Wagner approach, their sources of inaccuracy are provided and the anodic decomposition of SE is highlighted as the key source for the overestimated result. Modifications in the electrode selection and data interpretation are also proposed to approach the intrinsic electronic conductivity of SEs. A two‐step polarization method is also proposed to estimate the electronic conductivity of sulfides that decompose during measurement. Measured by the modified approach, the electronic conductivities of all SEs are one or two orders of magnitude lower than the reported value. Despite that, the electronic conductivity of sulfides seems to be still quite high to enable SSBs with a long calendar life of >10 years, highlighting the critical need for a more careful study of electronic transport in lithium SEs.