磷酸铁锂电极的卤水提锂热力学与分离特性

Thermodynamic basis and ions separation characteristics of lithium extraction by LFP electrode from complex brine

为进一步了解磷酸铁锂电极吸附提锂的特性和对复杂卤水中离子的分离特性,利用循环伏安法对氯化锂、氯化钠、氯化钾、氯化镁等二元体系和多组分体系扫描的热力学行为进行了研究,包括:离子嵌脱规律、副反应和伴随反应特征、多元体系的离子分离特性以及盐湖卤水恒电势提锂。研究确定了Li^(+)、Na^(+)、K^(+)、Mg^(2+)在磷酸铁锂电极的嵌入电势分别为-0.072、-0.294、-0.382、-0.738 V;研究表明在-1.2~1.2 V的循环伏安扫描,有水氧化产氧或水的还原产氢发生;对模拟卤水的CV扫描,出现Li^(+)单独嵌入峰和Na^(+)、K^(+)、Mg^(2+)的聚集嵌入峰,峰间波谷明显,具备电化学提锂条件;对一里坪卤水进行恒电势提锂,Mg/Li从原卤的56.84降到脱附溶液的0.19,锂离子嵌入量占阳离子嵌入总量的64%。

In order to further understand the characteristics of lithium extraction by LiFePO_(4)(LFP)electrode and the separation of ions from complex brine,the thermodynamic behaviors of binary and multicomponent systems such as lithium chloride,sodium chloride,potassium chloride and magnesium chloride were investigated by cyclic voltammetry(CV).It includes:the behavior of ions intercalation and desorption,the characteristics of side reactions and concomitant reactions,the ion separation characteristics of multicomponent system and the extraction of lithium from salt lake brine by constant potential.The intercalation potentials of Li^(+),Na^(+),K^(+),Mg^(2+)at LiFePO_(4) electrode were determined to be-0.072,-0.294,-0.382,-0.738 V,respectively.The results show that in the potential range of-1.2-1.2 V,oxygen production by water oxidation or hydrogen production by water reduction occurs.In CV scanning of simulated brine,Li^(+)single embedded peak and Na^(+),K^(+),Mg^(2+)aggregation embedded peak appear,and the wave trough between peaks is obvious,i.e.it is possible to extract lithium by electrochemical methods.The case study of lithium extraction from Yiliping brine,the Mg/Li decreases from 56.84 of the original brine to 0.19 of the desorption solution,and the amount of lithium ion intercalation accounts for 64%of the total amount of cation intercalation.