Effects of a dual doping strategy on the structure and ionic conductivity of garnet-type electrolyte

Garnet solid electrolyte is the most promising candidate among inorganic solid electrolytes due to its wide potential window, good compatibility and high safety. In this work, a dual doping strategy is offered for the development of garnet-type electrolytes with high ionic conductivity . Te 6+ is introduced into the Zr sites to stabilize the high-ionic conductivity cubic phase. Simultaneously, Sr 2+ enter the La sites to achieve a fine-tuning of the Li + concentration by charge compensation, acting as a sintering agent of Te 6+ /Sr 2+ doped electrolytes. The structure, chemical composition and ionic conductivity of Li 7 − 2 y + x La 3 − x Sr x Zr 2 − y Te y O 12 ( x  = 0–0.25, and y  = 0.35) electrolytes are systematically investigated by X-ray diffraction, Raman spectroscopy , scanning electron microscope , Energy Dispersive X-ray Spectroscopy, Inductively Coupled Plasma-Optical Emission Spectrometry and Alternating Current impedance. The results show that the optimal amount of Sr 2+ substitution helps to reduce the total resistance by promoting the growth of grains and ceramic densification . Among the investigated compositions, the composition with Li 6.425 La 2.875 Sr 0.125 Zr 1.65 Te 0.35 O 12 exhibits excellent performance with relative density of 97.95%, conductivity of 4.27 × 10 −4  S cm −1 at 25 °C and activation energy of 0.30 eV. The assembled Li/Li 6.425 La 2.875 Sr 0.125 Zr 1.65 Te 0.35 O 12 /Li symmetrical batteries are cycled galvanostatically under different current densities. The results show that the symmetrical battery can achieve good cyclic stability, good Li + stripping and plating process and low overpotential.