La-Al-O functional nanocoating to increase Li1+xAlxGe2-x(PO4)3/Li metal interface stability in solid-state battery

Solid-state battery with lithium anode and NASICON-type electrolyte, particularly.Li1+xAlxGe2-x(PO4)3 (LAGP), is promising safety rechargeable energy source. However, the Li|LAGP system exhibits a rapid decline in performance and a limited operational lifespan. One potential avenue for enhancing operational lifespan is the introduction of functional nanocoating at the anode/electrolyte interface. The present study considers the La-Al-O at varying Al:La ratios obtained by atomic layer deposition (ALD) as the functional coating, where Al-O was used to increase the interface stability and La-O to vary conductivity and electrochemical stability of the coating. It was shown that mixed oxide LaAlO3–Al2O3 (LaxAl2-xO3, x < 1) is formed at low La contents, which lead to stable operation without increasing overvoltage for more than 1000 h. Moreover, the introduction of 1 at% La results in an interface resistance decrease compared to Al2O3 coating and uncoated LAGP. It was also shown that high La content decreases the initial interface resistance, but affects the composition uniformity due to the lanthanum carbonate appearance, which leads to LAGP degradation at currents greater than 0.2 mA/cm2. Therefore, it is possible to extend the cycling life and stability of the LAGP solid electrolyte in contact with lithium by introducing a LaAlO3–Al2O3 functional coating.