<p>Solid state lithum ion batteries(SSB) are widely seen a huge prospect for energy storage. LiFePO₄ (LFP) is gaining wide recognition in being considered as cathode for lithium ion batteries (LIBs). Despite all these advantages, the gravimetric and volumetric energy density of LFP is lower than other cathode materials. High temperature operation results in better performance of LFP based LIBs due to its thermal stability. However, the columbic efficiency of LIB in the first discharge cycle is reported to be as low as 63% in literature. The ionic conductivity plays a vital role in maximising the performance of solid state lithium ion batteries (SSB). Cell temperature and lithium ion concentration play a major role in affecting the ionic conductivity. In this research, we study the effect of lithium ion concentration and temperature on overpotentials, output current and diffusion induced stress for LFP-Li₇La₃Zr₂O₁₂ (LLZO)-Li metal system. Anode overpotential is found to increase with increase in time, lithium ion concentration and seen to reduce with increase in temperature. Diffusion induced stress reduces with increase in temperature and increases with increase in lithium concentration. The output current of SSB decreases over time due to the limitations at the electrode–electrolyte interface. Modeling results are compared with experimental data and found to compare well.</p>