Model system based interface design for enhancement of the electrochemical performance of Ni-rich NMC for Li-ion batteries

The proposed project’s research embraces a persuasion given by a Vice President of EU Maroš Šefčovič in a recent statement: “Batteries are at the heart of the industrial revolution and I am convinced that Europe has what it takes to become the world’s leader in innovation, decarbonization, and digitization”, and goes along with the strategies for Europe to become a carbon-neutral region. Batteries are recognized as one of the Key Enabling Technologies, which will empower decarbonization of the transport sector in short term, and promote the use of renewable energy sources in the long term perspective. The ambitious goal of the proposed project is to achieve improved capacity stability of Ni-rich LiNixMnyCozO2 (NR-NMC, x+y+z=1, x>0.6) cathode-based Li-ion battery cells via the application of carefully designed protective interface coatings at the NR-NMC/electrolyte interface. This material's system has been already actively researched, and some NR-NMC formulations had been industrially produced for electric vehicle battery cells, including the latest TESLA models. However, the development of novel NR-NMC formulations has been hindered by a fact that increased Ni content contributes not only to the higher energy density of the cathode but also to the shorter cycle life of the battery. Some of the possible reasons for such behavior are currently assumed to be the formation of unstable Ni–O bonds, Ni2+/Li+ cation intermixing, cathode/electrolyte interface reactions, and related phase transformations of surfaces, exposed to the electrolyte. Different remedying strategies have been proposed, including doping the NR-NMC material with transition metals and protecting the cathode’s surface via the application of various coating materials. While literature reports proved the benefits of doping strategy, coating of NR-NMC materials up to now have delivered many contradictory results, pointing out the lack of a systematic approach. To accomplish the proposed project’s goal, the design, deposition, and characterization of known and newly developed interfacial coatings will be approached systematically via the establishment of a comprehensive research platform for interfacial coating design and characterization. Within this platform, an NR-NMC811 thin-film model system with well-defined composition and surface crystallography will be designed and produced by pulsed laser deposition (PLD). This downscaling of the battery system will enable (I) the insight into the NR-NMC811 surface orientation-dependent electrochemical performance, and (II) a controlled study of coating’s composition, thickness, and deposition method’s impact on the battery’s capacity behavior. Both inorganic and polymer coatings will be considered, the most suitable formulations will be chosen or designed, and the deposition methods will be tested. Produced battery model system will be chemically and electrochemically aged to study the correlation of the interface structure with the electrochemical properties. The outcomes of this comprehensive approach will provide us with a knowledge matrix for interface coatings’ impact on the NR-NMC/electrolyte system’s electrochemistry. The knowledge matrix will serve then as a strong basis for the controlled transfer of the successful model system strategy on commercial NR-NMC powder material. The proposed work will combine the profound expertise of two groups from leading Slovenian research institutes and will be enriched by a collaboration with European research groups working in the materials’ design and batteries research fields.