Reduction of Energy Consumption in Lithium Electrolytic Cell by Improving Design and Operating Conditions

Abstract

Molten salt electrolysis is an efficient process to obtain metallic lithium but requires a considerable amount of energy. The use of a grooved diaphragm and rotating electrodes were studied using an advanced numerical model representing an experimental lithium electrolytic cell with the finality to reduce the required energy. Simulations were conducted using a turbulent (k-ε) model to solve the two-phase flow coupled to the transient mass transport inside a 2D axisymmetric electrolysis cell. The model also considers the recombination of Li with chlorine gas (Cl2), a backreaction that is detrimental to efficiency and energy consumption. The vertical diaphragm with grooves produces a reduction of 26.7% in energy consumption in comparison with the ungrooved design but increases by four times the amount of recombined lithium in the process. To decrease that recombination, the grooved diaphragm was inclined toward the anode. A vertical angle of 85° helps to reduce the energy consumption by 23.5% with approximately the same recombined lithium mass when compared to the vertical ungrooved design. The use of a rotating cathode with at an angular velocity of 0.25 rad s−1 results in a 40% decrease in energy consumption in addition to a decrease of 87.4% in metallic Li reconversion, in comparison with non-porous ungrooved diaphragm design.