2017 American Chemical Society. Al-doped Li 7-x La 3 Zr 2 O 12 is found to be more ionically conductive following voltammetric treatment in an all-solid-state Li|Li 7-x La 3 Zr 2 O 12 |Li cell configuration. This result is consistent with electrical impedance spectroscopy measurements, which reveal that the activation energy for lithium diffusion is reduced from 0.32 to 0.26 eV following voltammetric treatment. The Li deposition-dissolution signal has been observed in the voltammograms, and neutron powder diffraction shows an increase in the lithium content of the Li 7-x La 3 Zr 2 O 12 . Furthermore, X-ray photoelectron spectroscopy indicates a local rearrangement of O, resulting in a reduction of defects following voltammetric treatment, with the enhanced conductivity attributable to both the reduction of defect oxygen and increased lithium content. This work, therefore, reveals such voltammetric treatment as a simple and inexpensive alternative to existing doping approaches to boost the electrochemical performance of Li 7-x La 3 Zr 2 O 12 . The findings can improve the future development of all-solid-state Li-ion batteries. On the other hand, our approach to understanding the conductivity enhancement via voltammetric treatment may provide a better alteration in the ionic conduction of solid electrolytes during solid-state battery operation. (Graph Presented).