Engineering Electronic Pathways Within Cathode Microstructures Through Carbon-Coated NMC via Mechanofusion

Achieving high energy and power density in lithium-ion batteries requires precise control of conductive additive distribution within the electrode microstructure. Despite its critical role, the understanding of electronic pathways within electrodes remains limited. Moreover, existing manufacturing practices rely heavily on empirical knowledge and lack a mechanistic understanding. This thesis introduces a novel approach to optimise conductive additive utilisation through particle and electrode engineering. For the first time, a high-shear dry mixing technique, mechanofusion, was employed to create carbon-coated NMC particles and engineer electronic pathways within electrodes. The impact of processing parameters on coating characteristics, carbon black deagglomeration, and particle-level properties was investigated. The correlation between coating properties, slurry mixing and drying behaviour, and the slurry and electrode microstructure and electronic conductivity was explored. Conductive pathway design within electrodes was explored by systematically varying carbon content and mixing methods. The mechanofusion process effectively facilitated carbon black deagglomeration and coating formation on NMC particles. Coating characteristics were controlled through process parameters, with free carbon content decreasing with prolonged dry mixing. A novel powder resistivity measurement technique revealed that a short dry mixing time is sufficient to achieve minimal deagglomeration for low powder resistivity. Carbon black properties (i.e. structure level, particle size and graphitic character) impacted deagglomeration and the final resistivity. Coated NMC surfaces influenced PVDF adsorption and drying behaviour, which in turn affected slurry and electrode properties and their microstructure. High free carbon content during wet mixing was crucial for forming CB-PVDF clusters, facilitating bridge structure formation for long-range conduction in electrodes. While designed conductive pathways were achieved, the initial electronic conductivity did not surpass conventional methods. This research demonstrates the potential of mechanofusion for tailoring electrode microstructures. While further optimisation is necessary, the findings provide valuable insights into the complex relationship between particle-level properties, mixing and drying behaviour and slurry and electrode properties. This work lays the groundwork for developing engineered electrode architectures in next-generation lithium-ion batteries.