Synthesis of any material means that the obtained product contains some volume of other phases. These impurities sometime are neutral, sometimes worsen the functional properties of the target material, and sometime can cause unwanted side reactions. In production of electrode materials for markets of electric vehicles and renewable/grid energy storages, such material heterogeneity is turned up due to drastically increasing demands in not expensive large-scale production and required decreasing of grains sizes. Wherein, despite the modern level of nanotechnology, the structural characterization is still mainly made by avaraging methods. For the first time we demonstrate that structural heterogeneity in commercial negative electrode material Li₄Ti₅O₁₂ with sub-micron grain size synthesized using standard solid-state method can be described locally in terms of structural characterization of single particles. Combination of micro-Raman Spectroscopy and Scanning Electron Microscopy has allowed to consider phase transitions during solid-state synthesis from principally new angle. Proposed local approach can be used as an addition to integral techniques not only for Li₄Ti₅O₁₂, but also to a wide range of commercial products.

Solid state synthesis of Li₄Ti₅O₁₂ was made using chemically pure titanium dioxide TiO₂ and chemically pure lithium carbonate Li₂CO₃by the following reaction:

2Li₂CO₃ + 5TiO₂ = Li₄Ti₅O₁₂ + 2CO₂↑                                                                      (1)

Our modification of usual solid-state method, based both on analysis of intermediate reactions and review of the published data, uses three consequent synthesis stages with intermediate grinding which increased influence surface layers on material physical properties. In order to simplify other phases observation we knowingly increased the content of phase diagram nearest compositions TiO₂ и Li₂TO₃by using partial (incomplete) synthesis with skipped third stage.

Raman spectra of single particle (Figure 1) clearly demonstrate heterogeneity of phase transformations during reaction (1) and allow making us some conclusions about the processes peculiarities which can’t be made otherwise.

Figure 1: SEM images and corresponding Raman spectra of single particles of final phase Li₄Ti₅O₁₂ and two nearest phases Li₂TiO₃ and TiO₂ rutile. SEM images sizes are 0.8×1.0 µm.