Effect of Bubbles and Liquid Drops Fluid Dynamics on the Lithium Recombination inside a Lithium Electrolytic Cell with Diaphragm

Abstract

Metallic lithium, which is a critical and strategic metal for the world’s production of energy storage devices, is mainly produced from molten salt electrolysis. To increase the efficiency of the process, it is of utmost importance to prevent lithium recombination during the process to avoid energy waste. This research studies the behavior of the main variables involved in the reaction inside a Li-production experimental cell from the mass transfer, electrochemical and fluid dynamics standpoints. Simulations were done for a total electrolysis time interval of 600 s using a turbulent (k-ε) approach to solve the two-phase flow coupled to the lithium electrolysis process. To analyze the influence of cathode fluid dynamics in relation with the amount of recombined lithium, two configurations of the diaphragm were evaluated including the incorporation of a baffle at the bottom of the cell and the inclination of the diaphragm. The baffle reduced the amount of recombined lithium by 7 %, and the diaphragm with an inclination < 90° reduced the total recombined mass by 77 %, although it increased the energy consumption by 10 % with respect to the base case of a vertical diaphragm.

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

“…20 for the different inclination angles. When compared to Melendez et al (2022), the energy consumption by the grooved diaphragm is reduced by 27.3% for the 87°angled design. When compared to the vertical grooved diaphragm (90°), the energy consumed increased by 4.3 and 2.3% when 85°and 87°angles are respectively used.…”

“…The numerical model integrates the most important transport phenomena occurring in each component of the electrolytic cell. All parameters and properties found in the equations describing the model are taken from Melendez et al (2022). Transient simulations of the lithium electrolysis cell were fixed to 600 s, a period long enough to reach a pseudo steady state regime and were conducted using Comsol ® Multiphysics.…”

“…[8][9][10] They all have taken into account the detrimental effect of chlorine bubble production that brings an additional resistance to the mass and charge transfer taking place in the electrolyte solution and limits the electrochemical reactions on the anode surface. Recently, Melendez et al (2022) studied the effects of chlorine bubbles and liquid lithium fluid dynamics on the recombined lithium mass and the energy consumption. They used an electrolytic cell with a non-porous diaphragm, with the particular interest to develop new designs for efficient production of lithium with industrial applications.…”

“…They used an electrolytic cell with a non-porous diaphragm, with the particular interest to develop new designs for efficient production of lithium with industrial applications. 11 Previous studies have shown that the effect of mass transfer across the anodic boundary layer, where Cl 2 is produced, has to be improved in order to optimize the electrolytic cell. Vogt et al (1983Vogt et al ( -2017 have developed several empirical equations to relate the boundary layer thickness to electrochemical parameters like local current density, while Liu et al (2015) have defined the thickness layer using linear approximations.…”

“…On the other hand, Riegel et al (1998) measured experimentally the boundary thickness inside a water electrolysis cell in steady state for turbulent and laminar regimes. These data were used by Melendez et al (2022) to further study the anodic boundary layer thickness in their steady-state fluid dynamics model.…”