Role of Sputtering Deposition Pressure on the Electrochemical Performance of Li ₄ Ti ₅ O ₁₂ Anodes

This communication investigates the influence of sputtering plasma density, controlled through the working deposition pressure, on the growth and electrochemical performance of Li 4 Ti 5 O 12 (LTO) anodes for lithium-ion battery applications. A systematic correlation between the deposition pressure and the microstructural, structural, chemical, and electrochemical properties of LTO thin films was established. At low working pressure (5 mTorr), sputtered species exhibit a long mean free path and high kinetic energy, which enhances resputtering phenomena. These conditions promote the formation of nonstoichiometric Li 4 Ti 5 O 12 with a high rutile TiO 2 secondary phase (88 wt %) and a high porosity level (13%), resulting in poor electrochemical performance (11.5 mAh g –1 ). High working pressure (20 mTorr) leads to reduced mean free path and kinetic energy of the sputtered species, suppressing resputtering effects and increasing the formation of stoichiometric Li 4 Ti 5 O 12 with lower porosity (7%). However, the presence of secondary phases under these conditions limits the electrochemical performance to moderate values (35 mAh g –1 ). Notably, an intermediate deposition pressure (15 mTorr) provides an optimal balance among porosity (7%), rutile TiO 2 content (34 wt %), and Li 4 Ti 5 O 12 phase (66 wt %) formation, yielding the highest electrochemical performance (39 mAh g –1 ) across the investigated pressure range.