Atomic Layer Deposition of Textured Li₄ Ti₅ O₁₂ : A High-Power and Long-Cycle Life Anode for Lithium-Ion Thin-Film...

The "zero-strain" Li₄ Ti₅ O₁₂ is an attractive anode material for 3D solid-state thin-film batteries (TFB) to power upcoming autonomous sensor systems. Herein, Li₄ Ti₅ O₁₂ thin films fabricated by atomic layer deposition (ALD) are electrochemically evaluated for the first time. The developed ALD process with a growth per cycle of 0.6 Å cycle^-1 at 300 °C enables high-quality and dense spinel films with superior adhesion after annealing. The short lithium-ion diffusion pathways of the nanostructured 30 nm films result in excellent electrochemical properties. Planar films reveal 98% of the theoretical capacity with 588 mAh cm^-3 at 1 C. Substrate-dependent film texture is identified as a key tuning parameter for exceptional C-rate performance. The highly parallel grains of a strong out-of-plane (111)-texture allow capacities of 278 mAh cm^-3 at extreme rates of 200 C. Outstanding cycle performance is demonstrated, resulting in 97.9% capacity retention of the initial 366 mAh cm^-3 after 1000 cycles at 100 C. Compared to other deposition techniques, the superior performance of ALD Li₄ Ti₅ O₁₂ is a breakthrough towards scalable high-power 3D TFBs.