Modelling of turbulent shear controllable co-precipitation synthesis of lithium ion battery cathode precursor micro-particles in a Taylor-Couette flow reactor with variable configurations of inner cylinder

Turbulent shear controllable co-precipitation synthesis of lithium ion battery cathode precursor micro-particles, Ni_0.6Co_0.2Mn_0.2(OH)₂ (NCM622), in a Taylor-Couette flow (TC) reactor has been investigated using both CFD simulation and experimental validation. The experimental co-precipitation in TC reactor was conducted using two types of inner cylinder, circular and lobed cross-sections (referred to as CTC and LTC), focusing on the effects of processing time and local turbulent shear rate. CFD simulation was employed to reveal the difference of flow field at various operating conditions. Both CFD simulation and experimental results show that the increased shear rate can lead to the decrease of the final synthesised micro-particle size due to the suppression of particle growth by turbulence eddy induced shear. Taylor-Couette flow by using the lobed inner cylinder can achieve an enhanced shear rate in the impinging jet regions formed in the vicinity of the inner cylinder surface due to the occurrence of a large radial velocity gradient. Consequently, the synthesised micro-particle properties such as morphology and specific surface area in the LTC are much more improved than those in the CTC. The mixing was also assessed and characterised by two variables, mean mixture fraction and its variance, predicted by CFD modelling with user-defined scalar (UDS), and correlating with the effect of shear rate for both the CTC and LTC. CFD simulation reveals that effective mixing at both the macro-scale and micro-scale can be quickly achieved in the LTC.