Lithium-ion batteries have garnered attention due to their high energy density, extended lifespan, and efficiency ¹. However, safety issues associated with their organic liquid electrolyte ², which can react exothermically in accidents or reduce lifespan under extreme conditions, have prompted exploration into alternatives. The substitution of liquid electrolytes with solid-state electrolytes is considered due to their enhanced thermal stability, potentially extending battery life and increasing capacity ^3,4. Despite these advantages, challenges such as interfacial resistance, interface reactions, and low ionic conductivity ^5,6 persist, along with the need for synthesis methods that allow precise control over material morphology, structure, composition, and industrial scalability. In this context, sol-gel processing stands out as a versatile option for such applications.

Among various families of solid electrolytes, perovskite-type ones (ABO₃, where A= Li and La; B= Ti) have gained significance due to their environmental stability and diverse applications. These electrolytes exhibit grain ionic conductivities exceeding 10⁻³ S/cm ^7–9. However, the total conductivity remains in the order of 10⁻³ due to high ionic conductivity at grain boundaries ^10–12.

The study focuses on synthesizing the solid electrolyte Li_0.3La_0.57TiO₃ (LLTO) using the sol-gel method with nitrates, alkoxides, and complexing agents. The research explores the impact of different calcination temperatures on composition, structure, morphology, and ionic conductivity, evaluating their influence on reducing grain boundary resistance.

Results reveal that the sol-gel process produces solid electrolytes with a perovskite structure and phase percentages exceeding 91% in powders calcined at temperatures of 700, 800, and 900 °C, surpassing 99% in pellets sintered at 1300 °C. These exhibit a tetragonal crystalline system with the p4/mmm space group. Powders calcined at various temperatures present spherical particles ranging from 50 to 100 nm, with a uniform composition. After sintering at 1300 °C, pellets achieve a relative density exceeding 95%.

Calcination temperature significantly influences electrochemical properties. At 900 °C, grain boundary ionic conductivity reaches 0.34 mS/cm, with a total ionic conductivity of 0.3 mS/cm at 30 °C. Overall, solid electrolytes calcined at temperatures above 800 °C exhibit grain boundary conductivity exceeding 0.10 mS/cm, attributed to proper crystallization, increased density, reduced porosity, and a higher concentration of vacancies, facilitating rapid ionic diffusion of lithium in the solid electrolyte. Consequently, materials obtained through this sol-gel process demonstrate significant potential for use in fully solid-state lithium-ion batteries.