Nanocomposite Oxides from silicon-based MAX-phase as Negative Electrode for Lithium-Ion Batteries

In recent years, lithium-ion batteries (LIBs) have become essential for energy storage due to their high electrochemical capacity. However, the commonly used negative electrode material, graphite, has limitations, including safety concerns and aging, especially under high current densities. For this reason, alternative materials such as lithium-alloy systems (Li-Sn and Li-Si) are explored, as they offer higher theoretical capacities than graphite (783 mAh/g for Sn and 4212 mAh/g for Si, compared to 370 mAh/g for graphite). Despite their advantages, their practical use is limited by significant volume changes during charge and discharge cycles, which affect electrode stability and battery lifespan. One possible approach to address this issue is the use of conversion oxides such as SnO₂ and SiO₂, which react with lithium through a conversion mechanism, forming metal nanoparticles embedded in a Li₂O matrix. However, controlling volume changes remains a challenge. Another strategy is to combine conversion oxides with intercalation oxides, such as TiO₂, to create a more stable structure. In this study, MAX phases were investigated as precursors for synthesizing nanostructured oxide materials. MAX phases belong to a class of ternary carbides with the general formula Mn+1AXn and have a layered structure, giving them unique properties. MAX phases containing silicon, Ti₃Al₁₋ₓSiₓC₂ and Ti₃AlₓSiᵧSnzC₂ (with x+y+z=1), were synthesized and oxidized to obtain a composite material containing SiO₂ (with SnO₂) and TiO₂. The physical and chemical properties of the obtained materials were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD) to study their morphology and crystal structure. Their electrochemical performance was also evaluated as potential negative electrodes for LIBs, focusing on how the initial MAX phase composition and thermal treatment conditions influence capacity and cycling stability.