All-solid-state Li-ion batteries in thin-film format are currently the most promising concept for the energy storage needs of miniature electronic devices. Their applicability is however restricted by their inherently poor energy and power densities. By using 3D substrates, the effective surface area and thus the energy density could be markedly increased. Atomic layer deposition (ALD) is one of the few methods capable in producing conformal layers on such complex structures. As the basic research on new ALD processes for Li-containing thin films is only in early stage, the true impact of the ALD technique in the Li-ion battery field is yet to be demonstrated. The aim of this theses was to advance the field with the introduction of novel deposition processes for each of the active components of a thin-film Li-ion battery. An ultimate goal was to manufacture a fully functional all-solid-state thin-film battery. For each material, the process design needs to take into account the fundamental difficulties related to lithium-based ALD chemistries. Additionally, by avoiding the use of metal components other than Li in the materials, the environmental impact of the newly designed and fabricated thin-film battery could potentially be reduced. For the solid electrolyte, a novel thermal-ALD process was developed for one of the most promising thin-film battery electrolyte material, i.e. lithium phosphorus oxynitride (LiPON). Due to its complex composition, it had been considered highly challenging compound for the ALD synthesis. In this thesis, the key innovation was the use of a novel ALD precursor, diethyl phosphoramidate. In combination with lithium bis(trimethylsilyl)amide, the quaternary target material could be deposited with a simple binary ALD process. The conformality on high-aspect-ratio substrates was confirmed and the measured ionic conductivity value is among the highest reported for ALD-grown solid electrolytes. For the electrode materials, a completely new approach was demonstrated. By utilizing combined atomic/molecular layer deposition (ALD/MLD) technique the range of available electrode materials was broadened to those based on conjugated carbonyl systems. Based on their fully organic backbones, such lithium organic electrode materials should be less harmful than their inorganic counterparts. The negative electrode material, lithium terephthalate, was known as one of the top performing organic electrode materials, whereas a completely novel material, dilithium-1,4-benezenediolate (Li2Q), was developed to function as the positive electrode. Excellent rate performance was demonstrated for both materials; in particular, charge/discharge times as low as 0.25 s were observed for Li2Q. Moreover, these materials were combined into an all-solid-state thin-film battery that was able to undergo extended charge/discharge cycling.
|Translated title of the contribution||Orgaanisiin elektrodimateriaaleihin pohjautuvan ohutkalvo-litiumioniakun valmistus atomi/molekyylikerroskasvatusmenetelmällä|
|Publication status||Published - 2018|
|MoE publication type||G5 Doctoral dissertation (article)|
- atomic layer deposition
- molecular layer deposition
- lithium-ion battery
- thin film battery