Enhancing Li4Ti5O12 Anodes for High-Performance Batteries: Ti3+ Induction via Plasma-Enhanced Chemical Vapor Deposition and Dual Carbon/LLZO Coatings

Lithium titanium oxide (LTO) is a promising anode material due to its ability to store lithium through intercalation reactions. However, its electrochemical performance is limited by poor electron conductivity and side reactions with the electrolyte. In this study, plasma-enhanced chemical vapor deposition (PECVD) is employed to introduce oxygen vacancies and self-doped Ti³⁺ into LTO to improve the internal conductivity. Subsequent carbon coating and aluminum-doped lithium lanthanum zirconate garnet (LLZO) layers resulted in a multi-layered composite denoted as LTO−L-x. Morphological analyses using SEM and TEM demonstrated the successful growth of Al-doped LLZO on carbon-coated LTO. Aluminum ions in LLZO cubic structure are crucial for stabilizing the high ionic conductive phase during cooling, as confirmed by X-ray diffraction. The dual coating layers have a significant impact on the rate capability, reducing polarization gaps and enabling higher capacities at various current rates. Long-term cycling tests reveal the robustness of the composite, with LTO−L-1.0 retaining 90.8 % capacity after 4000 cycles at 1.0 A g⁻¹. This underscores the sustained high electronic and ionic conductivity facilitated by the dual coating layers. The study contributes to the design of advanced anode materials for lithium-ion batteries, emphasizing the importance of tailored coating strategies to address conductivity and stability challenges.