Microfluidic Chip for High-Throughput Microstructure Detection of Precursor Particles

The microstructure of ternary precursors significantly influences the electrochemical performance of ternary cathode materials and, consequently, the overall performance of lithium-ion batteries. In industrial production utilizing traditional co-precipitation methods, Scanning Electron Microscopy (SEM) is typically employed for particle detection. However, this approach is limited by offline sampling lag, poor representativeness, cumbersome sample preparation, and low efficiency, failing to achieve real-time quality feedback on production lines. To enable high-throughput particle detection, this study proposes a multi-layer PDMS chip designed for three-dimensional (3D) hydrodynamic focusing. The sheath fluid compressed the sample flow in horizontal and vertical directions, respectively, to form a flat ribbon flow passing through the detection area. High-fidelity raw images are captured for automated particle microstructure analysis. Firstly, a chemical pretreatment protocol was optimized to ensure stable precursor solution transport. Secondly, a three-layer composite microchannel featuring a sequential horizontal and vertical sheath-flow compression mechanism was designed, with its geometry optimized via Computational Fluid Dynamics (CFD) simulations. Subsequently, experimental optimizations of flow rate ratios were performed using sodium fluorescein, followed by validation with ternary precursor solutions. The results indicate that the microchannel achieves flattened monolayer focusing of randomly distributed precursor particles, compressing the sample stream height to approximately 15.44 μm, thereby maintaining the particle stream within the microscope's depth of field and analyzing particle microstructure efficiently based on a microscopic image. Moreover, it is confirmed that the focused stream dimensions are primarily governed by the flow rate ratio, allowing for a flexible increase in detection throughput by adjusting the total flow rate. Different from static offline particle analyzers, this platform captures dynamic particle morphology under continuous flow, providing real-time data to guide co-precipitation reaction adjustment.