Experimental and theoretical study on enhanced electrochemical properties of double doped garnet-type solid electrolyte

Garnet-type solid electrolyte (Li7La3Zr2O12, LLZO) is believed as a promising candidate for all-solid-state battery due to its high voltage window and good stability with metallic lithium. However, it exists as tetragonal phase with low ionic conductivity at room temperature, which seriously hinders its practical application. In this paper, the strategy of In/Ga ions was introduced into LLZO, which can be found that double doping can improve the structural stability and the electrochemical properties of the sample compared to single doping. When x = 0.1, the sample Li6.55+xGa0.15La3Zr2-xInxO12 shows the high ionic conductivity of 1.5 x 10-4 S/cm, and activation energy of 0.268 eV. Density functional theory (DFT) calculation show that the introduce of In3+ and Ga3+ can effectively improve the ion transport capacity to reduce the transport energy barrier. In addition, the Li/In/Ga-LLZO/Li cells could cycle stably for 1000 h at 60 degrees C with the current density of 0.1 mA/cm2.