Development of Li-Organic Battery Materials with Atomic/Molecular Layer Deposition

Li-ion battery (LIB) is a piece of the puzzle for solving the present climate and energy crisis. Hence, the adaptation of LIBs is rapidly increasing, which has evoked severe concerns about the abundance, sustainability, and recyclability of the electrode raw materials. Cycle life is one of the main parameters regarding the sustainability of the LIBs, and it can be improved by protecting the active materials with suitable coatings. The scope of this thesis was twofold: (i) to challenge new organic electrode (OE) materials as more sustainable alternatives to current electrode materials, and (ii) to develop new Li-organic protective coating materials for the LIB electrodes. The gas-phase atomic/molecular layer deposition (ALD/MLD) thin-film technique provides unique advantages for both applications, and it was comprehensively utilized in this thesis. The focus was on developing new Li-organic ALD/MLD processes, which are still scarce in the literature. The overall goal was to show the applicability, benefits, and uniqueness of ALD/MLD technology to deposit various Li-organic materials for potential battery applications. In addition to five new ALD/MLD processes for OE anode materials, an empirical method for simplifying source temperature's optimization in ALD/MLD based on thermogravimetric analysis was developed. The OE anode materials showed similar intrinsic electrochemical performance metrics as previously measured with conventional electrodes with bulk materials. As the thin-film electrodes deposited from the gas phase do not contain any additives that are usually mixed with the active material, they can be considered a perfect model for studying the electrode materials' intrinsic properties. The post-mortem X-ray analysis of the cycled electrodes showed amorphization of the active material whenever the charge-discharge voltage plateau was lost. The performance decay is proposed to be caused by the excess lithiation of the aromatic core and subsequent side reaction. Pioneering work with three new ALD/MLD processes for possible Li-organic protective coatings was accomplished in this thesis. One of the processes utilized CO2 for the first time in the ALD/MLD process to deposit lithium alkyl carbonates. The lithium alkyl carbonates are an exciting group of materials because they are abundant in the organic part of the solid electrolyte interphase (SEI), forming naturally in the LIBs. This development allows the depositions of artificial SEI coatings. Furthermore, films of dilithium-1,4-benzenedisulfonate were deposited, diffraction patterns reported, and performance evaluated. The performance still needs to be improved, and the Li-organic coatings applied on conventional electrodes, but the groundwork is now laid down.