Purification of industrial grade lithium chloride for the recovery of high purity battery grade lithium carbonate

摘要

Due to lithium's high energy along with other exceptional characteristics, lithium demand across many industries is rising, specifically for Li-batteries. Therefore, a sufficient supply of high purity lithium is vital in order for these significant technologies to develop. In the current work, industrial grade lithium chloride has been successfully treated with four simple precipitation steps to obtain a high purity battery grade lithium carbonate of 99.95%. The LiCl starting solutions contained K, Na, Mg, Ca, Cu, Ni, and Fe chloride contaminants and solutions of 2.5 to 10 M were simulated. The heavier metals and the majority of Mg were removed in a single step with an increase in pH. The removal of Ca and remaining Mg was executed by sodium oxalate addition where the calcium levels of the 10 M were able to be reduced to 5-6 ppm in solution. It appeared that the higher molarity and ionic strength of the LiCl solution aided in obtained higher degrees of impurity removal. Finally, high purity Li2CO3 was obtained by first precipitating from brine solution, followed by a second purification step with pressurized CO2. The second step allowed for the removal of entrapped Na and K after the first precipitation, resulting in 99.95 wt% purity Li2CO3.