Ex-situ X-ray diffraction analysis of electrode strain at TiO2 atomic layer deposition/α-MoO3 interface in a novel aqueous potassium ion battery

•Ex-situ investigation of strain in a α-MoO3 anode with TiO2 ALD thin film.•Study of the material strain developed at the thin film/electrode interface.•Aqueous potassium ion battery.•10 nm TiO2 coated electrode experiences strain reduction of 68.2%.•10 nm TiO2 coated electrode retains 66.2% of its initial capacity.

The effect of thin film TiO2 atomic layer deposition (ALD) coating on induced material strain is investigated utilizing ex-situ XRD analysis of a layered-structured α-MoO3 anode. Electrode material lattice expansion is quantified by the examination of ex-situ XRD peak shift, and is performed on both potassiated and potassium-deficient electrodes. Observations of TiO2 ALD coated electrodes reveal significant strain reduction of the electrode material resulting in an increase in the life-cycle of the aqueous cells. The presence of the 10 nm thick amorphous TiO2 ALD layer is found to withhold considerable lattice strain at the thin-film/electrode interface, reducing lattice deformation by 68.2% and exhibits a capacity retention 2.5 times greater than that of the pristine electrode after 20 cycles of operation. The influence of the ALD coating on charge/discharge kinetics and cell capacity is also examined.