Synergetic effect of secondary nucleation and growth on the lithium carbonate particle size in the gas-liquid reactive crystallization of LiCl-NH3·H2O-CO2

In this study,the gas-liquid reactive crystallization of LiCl-NH3·H2O-CO2 was adopted to produce Li2CO3.The weakly alkaline nature of NH3·H2O in the absence of any recarbonation process resulted in a unimodal and easily controllable particle size distribution(PSD)of the obtained Li2CO3.The reaction temperature significantly influenced both the Li2CO3 particle size and PSD.By increasing the temperature from 25 to 60℃,the volume weighted mean particle size increased from 50.5 to 100.5μm,respectively.The Li2CO3 secondary nucleation rate and growth rate were obtained by focused beam reflectance measurements and a laser particle size analyzer,respectively.The secondary nucleation rate of Li2CO3 reduced as a function of temperature,whereas the growth rate increased.In addition to improving the surface energy of the crystals to enhance the growth process,higher temperatures also reduced the supersolubility of Li2CO3,which also plays a role to decrease the secondary nucleation rate.At a constant temperature,supersaturation affects the Li2CO3 particle size through the synergistic effect of secondary nucleation and growth.Hence,with improved supersaturation,the mean particle size of Li2CO3 decreased.The results provide a meaningful way to evaluate the crystallization process and to regulate the particle size.

Advances in reactive co-precipitation technology for preparing high-performance cathodes

Reactive crystallization plays an essential role in the synthesis of high-quality precursors with a narrow particle size distribution,dense packing,and high sphericity.These features are beneficial in the fabrication of high-specific-capacity and long-cycle-life cathodes for lithium-ion and sodium-ion batteries.However,in industrial production,designing and scaling-up crystallizers involves the use of semi-empirical approaches,making it challenging to satisfactorily meet techno-economic requirements.Furthermore,there is still a lack of in-depth knowledge on the theoretical models and technical calculations of the current co-precipitation process.This review elaborates on critical advances in the theoretical guidelines and process regulation strategies using a reactive crystallizer for the preparation of precursors by co-precipitation.The research progress on the kinetic models of co-precipitation reactive crystallization is presented.In addition,the regulation strategies for the reactive crystallization process of lithium-ion ternary cathodes are described in detail.These include the influence of different reactive crystallizer structures on the precursor's morphology and performance,the intelligent online measurement of efficient reactive crystallizers to ensure favorable conditions of co-precipitation,and preparing the precursor with a high tap density by increasing its solid holdup.A controllable reactive crystallization process is described in terms of the structural design with concentration gradient materials and bulk gradient doping of advantageous elements(such as magnesium ion)in lithium-ion cathodes and the fabrication of sodium-ion cathodes with three typical materials-Prussian blue analogues,transition metal oxides,and polyanionic phosphate compounds being involved.