Stabilizing the Solid Electrolyte in Inert Atmosphere for Solid-State Battery Fabrication Through Co-Sintering Process

Climate change due to excessive emission of greenhouse gases has impacted society and ecological life. Therefore, it is an urgent requirement to find alternative renewable (solar and wind) energy sources to replace conventional fossil fuels. Here, low cost, safe and high energy storage devices are required to ensure a continuous energy supply. However, current Li-ion batteries are facing challenges to fulfil the safety and high energy demands of fast-growing market of electric vehicles (EVs) and hybrid electronic vehicles (HEVs). In particular, liquid organic electrolytes used in conventional LIBs have raised the safety issues due to serious fire risk because of its flammability and volatility [1-3].<br/>Therefore, extensive research is being focused to replace liquid electrolyte with suitable solid electrolyte for next-generation (SSBs) [4]. The inorganic solid electrolytes are well-known for their realistic industrial manufacturing due to higher stability against ambient air and high temperature [5]. The NASICON type Li_1+xAl_xTi_2-x(PO₄)₃ (LATP) has shown very promising properties in terms of chemical/thermal stability and low cost. The ionic conductivity of LATP has been reported upto 10^-4 to 10^-3 S cm^-1 at room temperature [6]. If fabrication of SSB is considered by co-sintering process of LATP solid electrolyte and phosphate based cathode materials such as LiFePO₄, Li₃V₂(PO₄)₃, sintering can only be possible in inert atmosphere (Ar/N₂) because these cathode materials are not stable in air at high temperature.<br/>Therefore, by considering more practical approach for SSB fabrication through co-sintering process, present work focuses on sintering behavior of Li_1.4Al_0.4Ti_1.6(PO₄)₃ (LATP) solid electrolyte in argon atmosphere as a function of particle size and sintering conditions. The structural analysis of LATP was done by XRD, morphological study by SEM, particle size analysis by granulometry and densification of pellets was determined by dilatometry techniques. The conductivity measurement of sintered pellets is carried out by AC impedance spectroscopy techniques. At the end of study, we have not only stabilized the LATP in argon atmosphere but also achieved the high conductivity of 8.77×10^-4 S cm^-1 at 25 °C for pellets sintered at just 800 °C in argon. The electrochemical study of LATP was also conducted in symmetric cell and with Li₃V₂(PO₄)₃cathode.