Ga-doping in Li0.33La0.56TiO3: a promising approach to boost ionic conductivity in solid electrolytes for high-performance all-solid-state lithium-ion batteries

Abstract

All-solid-state lithium-ion batteries (ASSLBs) are the next advancement in battery technology which is expected to power the next generation of electronics, particularly electric vehicles due to their high energy density and superior safety. ASSLBs require solid electrolytes with high ionic conductivity to serve as a Li-ion battery, driving extensive research efforts to enhance the ionic conductivity of the existing solid electrolytes. Keeping this in view, the B-site of Li_0.33La_0.56TiO₃ (LLTO) solid electrolyte has been partially substituted with Ga and novel Ga-doped LLTO (Li_0.33+xLa_0.56Ti_1−xGa_xO₃) solid-electrolytes are fabricated using the solid-state reaction method, followed by sintering at 1100 °C for 2 h. The effects of Ga substitution on the structural changes, chemical states, ionic conductivity, and electrochemical stability of LLTO are systematically analyzed. The XRD analysis of the LLTO samples confirms the formation of a tetragonal perovskite structure and increasing bottleneck size up to 3% Ga-doped samples. XPS results have further confirmed the successful substitution of Ti⁴⁺ by Ga³⁺. The Ga³⁺ substitution has successfully enhanced the conductivity of LLTO solid electrolytes and the highest conductivity of 4.15 × 10⁻³ S cm⁻¹ is found in Li_0.36La_0.56Ti_0.97Ga_0.03O₃ (x = 0.03), which is an order of magnitude higher than that of pristine LLTO. This increase in ionic conductivity is a synergistic effect of B–O bond stretching resulting from the size difference between Ga³⁺ and Ti⁴⁺ and the increase in grain size. Moreover, the synthesized solid electrolytes are stable within the range of 2.28 to 3.78 V against Li/Li⁺, making them potential candidates for all-solid-state lithium-ion batteries.