Nowadays, lithium-ion batteries (LIBs) are one of the most convenient, reliable, and promising power sources for portable electronics, power tools, hybrid and electric vehicles. The characteristics of the positive electrode (cathode active material, CAM) significantly contribute to the battery’s functional properties. Applying various functional coatings is one of the productive ways to improve the work characteristics of lithium-ion batteries. Nowadays, there are many methods for depositing thin films on a material’s surface; among them, one of the most promising is atomic layer deposition (ALD). ALD allows for the formation of thin and uniform coatings on surfaces with complex geometric forms, including porous structures. This review is devoted to applying the ALD method in obtaining thin functional coatings for cathode materials and includes an overview of more than 100 publications. The most thoroughly investigated surface modifications are lithium cobalt oxide (LCO), lithium manganese spinel (LMO), lithium nickel-cobalt-manganese oxides (NCM), lithium-nickel-manganese spinel (LNMO), and lithium-manganese rich (LMR) cathode materials. The most studied processes of deposition are aluminum oxide (Al₂O₃), titanium dioxide (TiO₂) and zirconium dioxide (ZrO₂) films. The primary purposes of such studies are to find the synthesis parameters of films, to find the optimal coating thickness (e.g., ~1–2 nm for Al₂O₃, ~1 nm for ZrO₂, <1 nm for TiO₂, etc.), and to reveal the effect of the coating on the electrochemical parameters of batteries. The review summarizes synthesis conditions, investigation results of deposited films on CAMs and positive electrodes and some functional effects observed due to films obtained by ALD on cathodes.

Today, lithium-ion batteries (LIBs) are the most widespread technology for electric energy storage. However, the technology requires further improvement, and one of the directions is atomic layer deposition protective coating creation on LIBs electrodes. The titanium oxide thin films influence on the NCM111 cathode electrochemical characteristics as a function of coating synthesis temperature and thickness was studied in this work. Separately, the Solef5130 binder heat treatment effect was studied using thermogravimetry with differential scanning calorimetry. The presence of titanium and its crystallinity degree on the cathode surface were confirmed by X-ray photoelectron spectroscopy, scanning electron microscopy with energy dispersive spectroscopy and Raman spectroscopy. Cathode’s C-rates were studied depending on discharge current, voltage and the number of charge-discharge cycles. Cyclic voltammetry and impedance spectroscopy were used to analyze the possible additional electrochemical reactions and coating influence on the resistance. As a result, cathodes with atomic layer deposition titanium oxide layers demonstrate cyclic stability and increased capacity retention (up to about 20%) with increasing discharge current (1C), and the coating synthesis temperature on the cathode surface plays a significant role in the final batteries capacity performance.

This study investigated the problem of lanthanum oxide uniform growth by atomic layer deposition (ALD) using water as the oxygen reagent. Although water is the classic reagent for ALD, it can be the reason for some problems (e.g., nonuniformity) with hygroscopic oxides (such as lanthanum oxide). There are some ways to improve coating quality: increase the purge duration after the water pulse, increase the synthesis temperature with the water process, and replace the oxygen reagent (e.g., for ozone). In this work, ways to improve were studied in the processes of coating growth using La(iPrCp)3. Spectral ellipsometry was used to study the thickness of the coatings. X-ray photoelectron spectroscopy with argon ion etching was used to investigate the chemical composition. X-ray diffraction and x-ray reflectometry were used to define structural properties. The influence of the purge duration after water and the reactor temperature was defined. The ALD parameters of La(iPrCp)3 and ozone were investigated. The dependence of coating characterization on oxygen reagent was researched. No improvements in uniformity were found in the synthesis using water; at the same time, the positive effect of ozone on the coating uniformity was confirmed. Ozone as a replacement for water helps to increase the uniformity of the coating by about 10 times. Coatings obtained with ozone are more similar to lanthanum oxide, and those obtained with water are more similar to lanthanum hydroxide.