Synthesis, Processing and Modification of NMC811 Cathodes for High-Performance and More Sustainable Lithium-Ion Batteries

This thesis addresses the critical sustainability and performance challenges inherent in the manufacturing of high-performance lithium-ion batteries, with a specific focus on the synthesis, processing, and modification of Nickel-rich NMC811 cathodes. As the global energy landscape shifts towards electrification, particularly in the transport sector, the demand for high-energy-density storage solutions has intensified. However, conventional battery manufacturing methods have significant obstacles, including dependence on critical raw materials and the use of hazardous chemicals. The research is therefore structured around two primary objectives: first, to optimize a scalable and robust synthesis route for the NMC811 active material, and second, to develop an environmentally benign, water-based electrode fabrication process to replace the industry-standard method that relies on the toxic N-Methyl-2-pyrrolidone (NMP) solvent and polyvinylidene fluoride (PVdF) binder. The first part of the investigation conducts a comparative analysis of co-precipitation and self-combustion synthesis methods, while also systematically evaluating the profound influence of different calcination atmospheres (oxygen, air, and nitrogen) on the final material properties. The results conclusively demonstrate that a co-precipitation method followed by calcination in a pure oxygen atmosphere is the superior pathway. This process yields NMC811 particles with a well-defined layered crystal structure, minimal cation mixing between Li⁺ and Ni²⁺ sites and a uniform spherical morphology. In contrast, calcination under a non-oxidizing nitrogen atmosphere was found to be detrimental, resulting in the formation of separate, electrochemically inactive transition metal oxides. This optimized synthesis route consistently produced the material with the most promising electrochemical performance, establishing a clear and effective protocol. The second part of the thesis focuses on replacing the hazardous and costly NMP/PVdF system. A sustainable, water-based slurry was successfully developed by screening various aqueous binders. It was determined that a synergistic blend of sodium alginate (ALG) and carboxymethyl cellulose (CMC) provides superior performance compared to single-binder systems, effectively balancing the required adhesion, cohesion and long-term electrochemical stability. To mitigate the inherent challenges of aqueous processing—namely, lithium leaching from the cathode material and the subsequent corrosion of the aluminum current collector—a surface modification strategy was implemented. NMC811 particles were coated with various passivating metal oxides (Al₂O₃, TiO₂, ZrO₂, and ZnO). Electrochemical testing revealed that cathodes fabricated with NMC811 coated with titanium dioxide and zinc oxide exhibited significantly enhanced specific capacity and rate capability, demonstrating the coatings' role as a protective barrier. In conclusion, this work establishes an optimized synthesis protocol for high-quality active material and validates a viable and sustainable water-based manufacturing process. Together, these findings offer a clear and integrated pathway toward more environmentally responsible production of next-generation lithium-ion batteries