Process-dependent phase evolution in thermally sprayed Li4Ti5O12 thin-film anodes revealed by synchrotron and surface analysis

Understanding process-induced phase evolution in thermally sprayed Li 4 Ti 5 O 12 (LTO) thin-films is critical for developing scalable battery electrodes with stable electrochemical performance. This study comparatively investigates Atmospheric Plasma Spraying (APS), Suspension Plasma Spraying (SPS), and High-Velocity Oxy-Fuel (HVOF) processing of LTO thin-film anodes using SEM/EDS, laboratory XRD, synchrotron µXRD/µXRF mapping, XPS, and electrochemical characterization. Synchrotron µXRD revealed distinct process-dependent phase evolution governed by thermal exposure and quenching behavior. HVOF retained the highest spinel LTO fraction (66.8 %), APS retained 65.1 %, while SPS showed the strongest decomposition with only 53.5 % LTO together with increased Li 2 TiO 3 (43.5 %) and TiO 2 formation (3.0 %). XPS analysis identified Li 2 CO 3 surface formation in APS and HVOF coatings, whereas SPS exhibited strong surface lithium depletion. Electrochemical measurements showed that APS-LTO exhibited the most favorable electrochemical response, with a working voltage of ∼1.56 V vs. Li/Li + and lower polarization resistance (∼18.7 kΩ) compared with SPS and HVOF coatings. The results establish process–structure–property relationships linking thermal spray conditions with lithium retention, phase stability, and electrochemical behavior in thermally sprayed LTO thin-films.