Lithium-ion batteries (LIBs) technology have drawn a lot of attention as a feasible solution for versatile energy storage devices with wide range of applications including consumer electronics, transportation and power generation where they are often combined with renewable energy generation systems. While exploring new anode and cathode materials, transition metal oxides (TMOs) nanomaterials with a spinel structure have been seriously considered due to their several advantages: relatively high theoretical capacity, low cost, safety, environmental friendliness, and natural abundance. Particularly, lithium manganese oxide (LiMn₂O₄) with its high capacity (148 mA h g^-1) and well-defined redox potentials, is one of the preferred cathode materials for LIBs. Similarly, lithium-titanium oxide (Li₄Ti₅O₁₂) is a very attractive material to replace graphitic anodes in LIBs offering an excellent cyclability due to negligible volume change and a high operating potential of 1.55 V vs. Li/Li⁺, which prevents metallic lithium plating.

The Raman analysis of electrochemically tested electrodes containing LiMn₂O₄ or Li₄Ti₅O₁₂ nanomaterials was performed. Electrodes were cycled versus lithium in the Swagelok-type cells and either fully charged and discharged or kept on partially lithiated states in order to study intermediate structures. Next, cells were disassembled and electrodes were washed in dimethyl carbonate and let dry in the argon atmosphere before performing further measurements. The Raman mapping was applied to this study to increase the measurement statics. The results show very clear structural changes over lithiation in both studied materials. We observed the evidence of phase transitions and complemented their mechanisms over electrochemical processes as well as made assignments of each detected phase. Additionally it was possible to detected small traces of impurity phases, which are normally below detection limit of X-ray diffraction. Moreover, their presence was confirmed by the electron spin resonance (ESR) spectroscopy. The ESR signal detected for LiMn₂O₄ with g-factor about 2 is due to Mn⁴⁺-Mn³⁺ exchange coupled. The changes in the linewidth for cycled samples shows a clear dependence in the Mn³⁺/Mn⁴⁺ ratio. The results for Li₄Ti₅O₁₂ will be also discussed.

The Raman mapping of electrodes can help in compositional analysis and hence it can indicate the heterogeneity and approximate the concentration of impurity phases. Raman spectroscopy is a fast and non-destructive tool to study electrode surfaces with wide probing range. The comparison of Raman and electrochemical results helps to understand possible capacity fade reasons such as blockage of diffusion channels or impurities formation.