X-ray photoelectron spectroscopic investigation of atomic-layer-deposited spinel Li4Ti5O12: Calcination under reducing atmosphere

Across all material candidates used as anodes in lithium-ion batteries, lithium titanate (Li4Ti5O12) (LTO) is an excellent replacement for conventional electrode materials, such as graphite or silicon. Compares to commercial graphite anodes, LTO offers a higher charging rate and safer operation, and compares to silicon, it undergoes almost no volume expansion during intercalation of lithium ions into the crystal lattice, so-called zero-strain material. However, the LTO performance still suffers from low conductivity due to the oxidation of titanium (Ti) in spinel-LTO and low ionic kinetics diffusion while cycling, which largely limits its application in solid-state batteries. Modifying the LTO lattice or crystal structure is one way to mitigate this problem. This study shows the coexistence of two main components, Ti4+ and Ti3+, in the crystal structure of LTO developed with a modified atomic layer deposition. The X-ray photoelectron spectroscopy analysis shows calcination under reducing gas, introduces Ti3+ and oxygen vacancies into the Li4Ti5O12 crystal, which can affect the electronic conductivity of LTO. Furthermore, we show how different substrates acting as diffusion barriers affect the film properties.

Automated summary

Lithium titanate (LTO) is a promising anode material for lithium-ion batteries, offering higher charging rate and safety compared to graphite and silicon. However, its limited conductivity and ionic kinetics diffusion hinder its application in solid-state batteries. This study demonstrates a modified atomic layer deposition approach to introduce Ti3+ and oxygen vacancies into the crystal lattice of LTO, improving its electronic conductivity. Moreover, the influence of different substrates as diffusion barriers on the film properties is investigated.