Numerical simulation method for electric de-intercalation lithium extraction

Abstract

The invention provides a numerical simulation method for electric de-intercalation and lithium extraction, which comprises the following steps: constructing a physical geometric model according to a flow field area and an electrode coating area of an electric de-intercalation and lithium extraction device, and dividing model areas according to the physical geometric model; constructing a hydrodynamic model and an electrochemical model by combining the hydrodynamic and electrochemical principles of the electric de-intercalation lithium extraction process; determining initial operation parameters of the fluid dynamic model and the electrochemical model and model boundary conditions of the physical geometric model according to the actual operation condition of the electric de-intercalation lithium extraction device; grid division is carried out on the physical geometric model, and grid encryption processing is carried out on the boundary of a model area; performing coupling processing on the fluid dynamic model and the electrochemical model, performing numerical solution on the obtained coupling model by adopting a finite element analysis method, and extracting a calculation result to finish numerical simulation. According to the invention, numerical simulation is carried out on the electric de-intercalation lithium extraction process, pre-calculation of various data in the lithium extraction process is realized, and the change rule of key indexes is revealed.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium extraction from salt lakes, and relates to a method for lithium extraction by electrointercalation and deintercalation, and particularly to a numerical simulation method for lithium extraction by electrointercalation and deintercalation. Background Art

[0002] At present, lithium extraction by electrointercalation and deintercalation from salt lakes belongs to an emerging technical field, and usually mainly uses a fixed-bed electrointercalation and deintercalation device in the form of electrode coating. Lithium-deficient lithium iron phosphate is coated on the surface of the cathode plate, and lithium-rich lithium iron phosphate is coated on the surface of the anode plate. Under the driving action of an externally applied current, the lithium-deficient lithium iron phosphate on the cathode side undergoes a reduction reaction to obtain an electron and simultaneously adsorbs lithium ions from the salt lake; the lithium-rich lithium iron phosphate on the anode side undergoes an oxidation reaction to lose an electron and simultaneously releases lithium ions into the lithium-rich solution. After several such cycles, the lithium concentration in the lithium-rich solution becomes higher and higher, thereby achieving the purpose of lithium extraction from salt lake brine.

[0003] The whole process of lithium extraction by electrointercalation and deintercalation from salt lakes includes various complex phenomena such as fluid flow, polarization phenomenon, mass transfer, etc., and various factors affect each other and are intertwined and complex. Current technicians can hardly truly master its internal laws only by analyzing on-site experimental data, and thus cannot determine the key factors for improving the lithium extraction efficiency, which hinders the industrial development of the lithium extraction technology by electrointercalation and deintercalation from salt lakes in the actual application process.

[0004] Therefore, it has become an urgent problem for technicians in the current field to provide a technical means to solve the above-mentioned problems in the process of lithium extraction by electrointercalation and deintercalation from salt lakes, improve the lithium extraction efficiency and stability, and promote the industrial application of this technology. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a numerical simulation method for lithium extraction by electrointercalation and deintercalation. By establishing mathematical models for processes such as flow, polarization, and mass transfer, and combining fluid dynamics and electrochemical principles, numerical simulation of the lithium extraction process by electrointercalation and deintercalation is carried out, and multiple mathematical models are coupled and solved to realize the pre-calculation of various data in the lithium extraction process by electrointercalation and deintercalation, thereby revealing the variation laws of the key indicators of lithium extraction by electrointercalation and deintercalation.

[0006] To achieve the purpose of this invention, the following technical solutions are adopted by the present invention:

[0007] The present invention provides a numerical simulation method for lithium extraction by electrointercalation and deintercalation, and the numerical simulation method includes the following steps:

[0008] S1. According to the flow field region and the electrode coating region of the lithium extraction device by electrointercalation and deintercalation, construct a physical geometric model, and divide the model region for the physical geometric model;

[0009] S2. Combine the hydrodynamic and electrochemical principles of the electro-deintercalation and lithium extraction process to construct a hydrodynamic model and an electrochemical model respectively;

[0010] S3. According to the actual operating conditions of the electro-deintercalation and lithium extraction device, determine the initial operating parameters of the hydrodynamic model and the electrochemical model and the model boundary conditions of the physical geometry model respectively;

[0011] S4. Perform mesh division on the physical geometry model, and encrypt the mesh at the boundaries of the model area during the mesh division process;

[0012] S5. Couple the hydrodynamic model and the electrochemical model, and use the finite element analysis method to numerically solve the obtained coupled model, and complete the numerical simulation after extracting the calculation results.

[0013] In step S2, the finite element volume method is used to construct the hydrodynamic model; the electrochemical model includes a charge transfer kinetics model and / or an ion migration kinetics model, and the Butler–Volmer equation is used to construct the charge transfer kinetics model, and the Nernst–Planck equation is used to construct the ion migration kinetics model.

[0014] The method provided by the present invention can accurately describe the electro-deintercalation and lithium extraction process by numerical simulation and calculation, establish mathematical models for processes such as flow, polarization, and mass transfer, combine hydrodynamic and electrochemical principles, and couple and solve multiple mathematical models, pre-calculate various data in the process of extracting lithium from salt lakes, and reveal the variation laws of key indicators of electro-deintercalation and lithium extraction, which is helpful to improve the lithium extraction efficiency and the stability of the lithium extraction process.

[0015] Preferably, the physical geometry model in step S1 includes a two-dimensional geometry model or a three-dimensional geometry model.

[0016] Among them, the model area obtained by dividing the two-dimensional geometry model includes: an anode coating boundary, an anode chamber, an anion membrane, a cathode coating boundary, and a cathode chamber; the model area obtained by dividing the three-dimensional geometry model includes: an anode coating area, an anode chamber, an anion membrane, a cathode coating area, and a cathode chamber.

[0017] Preferably, during the construction of the hydrodynamic model in step S2, the fluid states in the anode chamber and the cathode chamber are both set to laminar flow.

[0018] Preferably, the construction of the hydrodynamic model in step S2 is based on the mass conservation equation and the momentum conservation equation.

[0019] Preferably, after the construction of the hydrodynamic model and the electrochemical model in step S2, a mathematical model of the anion membrane and / or a mathematical model of the storage tank are also constructed.

[0020] When the physical and geometric model described in step S1 is a two-dimensional geometric model, the initial operating parameters described in step S3 include: standard exchange current density, fixed charge concentration of the anion exchange membrane, porosity of the anion exchange membrane, diffusion coefficient of lithium ions, diffusion coefficient of chloride ions, standard equilibrium electrode potential of the anode, standard equilibrium electrode potential of the cathode, mass transfer coefficient, and initial concentration of the solution in the chamber.

[0021] When the physical and geometric model described in step S1 is a three-dimensional geometric model, the initial operating parameters described in step S3 include: standard exchange current density, fixed charge concentration of the anion exchange membrane, porosity of the anion exchange membrane, conductivity of the electrode coating area, diffusion coefficient of lithium ions, diffusion coefficient of chloride ions, standard equilibrium electrode potential of the anode, standard equilibrium electrode potential of the cathode, mass transfer coefficient, and initial concentration of the solution in the chamber.

[0022] Preferably, the standard exchange current density is 10 A / m 2 to 30 A / m 2 .

[0023] Preferably, the fixed charge concentration of the anion exchange membrane is 1×10 6 C / m 3 to 1×10 10 C / m 3 .

[0024] Preferably, the porosity of the anion exchange membrane is 40% to 60%.

[0025] Preferably, the conductivity of the electrode coating area includes the conductivity of the anode coating area and the conductivity of the cathode coating area, which are independently 1×10 4 S / m to 5×10 4 S / m.

[0026] Preferably, the diffusion coefficient of lithium ions includes the diffusion coefficient D1 of lithium ions in the solution and the diffusion coefficient D2 of lithium ions in the anion exchange membrane, and D1 is 2×10 -8 m 2 / s to 3×10 -8 m 2 / s, D2 is 1×10 -10 m 2 / s to 3×10 -10 m 2 / s.

[0027] Preferably, the diffusion coefficient of chloride ions includes the diffusion coefficient d1 of chloride ions in the solution and the diffusion coefficient d2 of chloride ions in the anion exchange membrane, and d1 is 1×10 -8 m 2 / s to 3×10 -8 m2 / s, d2 is 1×10 -9 m 2 / s to 5×10 -6 m 2 / s.

[0028] Preferably, the standard equilibrium electrode potential of the anode is -0.6V to -1.0V.

[0029] Preferably, the standard equilibrium electrode potential of the cathode is 0.8V to 1.2V.

[0030] Preferably, the mass transfer coefficient is 0.4 to 0.6.

[0031] Preferably, the initial concentration of the solution in the chamber includes the initial lithium ion concentration and the initial chloride ion concentration of the solution in the anode chamber and the cathode chamber, and are independently 0 - 20 mol / m 3 , but not including 0.

[0032] When the physical geometry model in step S1 is a two-dimensional geometry model, the model boundary conditions in step S3 include the electrode coating boundary, the chamber inlet, the chamber outlet, the inlet solution flow rate, the inlet lithium ion concentration, and the external electric potential.

[0033] When the physical geometry model in step S1 is a three-dimensional geometry model, the model boundary conditions in step S3 include the electrode coating area, the chamber inlet, the chamber outlet, the inlet solution flow rate, the inlet lithium ion concentration, and the external electric potential.

[0034] Preferably, the electrode coating boundary includes the anode coating boundary and the cathode coating boundary.

[0035] Preferably, the electrode coating area includes the anode coating area and the cathode coating area.

[0036] Preferably, the chamber inlet includes the anode chamber inlet and the cathode chamber inlet.

[0037] Preferably, the chamber outlet includes the anode chamber outlet and the cathode chamber outlet.

[0038] Preferably, the inlet solution flow rate includes the anode chamber inlet flow rate and the cathode chamber inlet flow rate, and are independently 6 cm / s to 10 cm / s.

[0039] Preferably, the inlet lithium ion concentration includes the anode chamber inlet lithium ion concentration and the cathode chamber inlet lithium ion concentration, and the anode chamber inlet lithium ion concentration is 15 mol / m 3 to 25 mol / m 3 , and the cathode chamber inlet lithium ion concentration is 100 mol / m 3 to 200 mol / m3 .

[0040] Preferably, the external potential includes an anode external potential and a cathode external potential, the anode external potential is 0.3V to 0.4V, and the cathode external potential is -0.5V to 0V.

[0041] Preferably, the mesh generation in step S4 includes surface mesh generation or volume mesh generation. The surface mesh generation is for two-dimensional geometric models, and the volume mesh generation is for three-dimensional geometric models.

[0042] Preferably, the volume mesh generation includes tetrahedral mesh generation and / or hexahedral mesh generation.

[0043] Preferably, the mesh refinement process in step S4 includes: uniformly dividing the mesh in the direction parallel to the current, with the cell division ratio being 1:a; for the anion membrane and the main solution part in the direction perpendicular to the current, the cell division ratio is 1:b; and for the cells near the boundary of the anion membrane and the electrolyte, the cell division ratio is 1:c, controlling a < b ≤ c, thereby achieving the mesh refinement process.

[0044] Preferably, the calculation equations involved in the coupling process in step S5 include the mass conservation equation, the momentum conservation equation, the Butler–Volmer equation, and the Nernst–Planck equation.

[0045] Preferably, the numerical solution includes transient solution or steady-state solution.

[0046] Preferably, the calculation results include the internal potential distribution of the cavity, the current density, or the ion concentration distribution.

[0047] Preferably, the extraction timing of the calculation results is: when the numerical solution reaches the convergence condition.

[0048] Among them, the determination criteria for the convergence condition include residual monitoring, physical quantity stability, satisfaction of conservation laws, or continuity of the contour plot.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] The method provided by the present invention uses numerical simulation and calculation to establish mathematical models for processes such as flow, polarization, and mass transfer. Combining fluid dynamics and electrochemical principles, it couples and solves multiple mathematical models, can accurately describe the process of electro-deintercalation lithium extraction, pre-calculate various data in the process of extracting lithium from salt lakes, reveal the variation laws of key indicators of electro-deintercalation lithium extraction, and help improve the efficiency and stability of lithium extraction. Description of the Drawings

[0051] Figure 1It is the flowchart of the numerical simulation method for electrochemically deintercalating and extracting lithium provided by the present invention;

[0052] Figure 2 It is the two-dimensional geometric model constructed in Example 1;

[0053] Figure 3 It is the schematic diagram of setting the boundary conditions of the electrochemically deintercalating and extracting lithium model in Example 1;

[0054] Figure 4 It is the schematic diagram of the mesh division of the electrochemically deintercalating and extracting lithium model in Example 1;

[0055] Figure 5 It is the curve graph of the change in the lithium ion concentration of the anode and cathode in Example 1;

[0056] Figure 6 It is the contour map of the lithium ion concentration distribution when the reaction reaches 2 h in Example 1;

[0057] Figure 7 It is the curve graph of the change in the lithium ion concentration at the boundary of the anion membrane when the reaction reaches 2 h in Example 1;

[0058] Figure 8 It is the three-dimensional geometric model constructed in Example 2;

[0059] Figure 9 It is the schematic diagram of the mesh division of the electrochemically deintercalating and extracting lithium model in Example 2;

[0060] Figure 10 It is the contour map of the internal lithium ion concentration distribution of the electrochemically deintercalating and extracting lithium model in Example 2;

[0061] Figure 11 It is the curve graph of the change in the lithium ion concentration at the junction of the lithium-rich liquid chamber / brine chamber and the anion membrane on the anode / cathode ear side in Example 2.

[0062] Wherein: 1 - Anode coating boundary; 1a - Anode coating area; 2 - Anode chamber; 3 - Anion membrane; 4 - Cathode chamber; 5 - Cathode coating boundary; 5a - Cathode coating area; 6 - Anode chamber inlet; 7 - Cathode chamber inlet; 8 - Anode chamber outlet; 9 - Cathode chamber outlet. Detailed implementation manners

[0063] The technical solution of the present invention will be further described below through specific implementation manners. Those skilled in the art should understand that the described embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0064] A certain embodiment of the present invention provides a numerical simulation method for electrochemically deintercalating and extracting lithium, as Figure 1 shown, the numerical simulation method includes the following steps:

[0065] S1. Construct a physical geometry model according to the flow field region and electrode coating region of the electro - deintercalation lithium extraction device, and divide the model region for the physical geometry model;

[0066] S2. Combine the hydrodynamic and electrochemical principles of the electro - deintercalation lithium extraction process to construct a hydrodynamic model and an electrochemical model respectively;

[0067] S3. According to the actual operating conditions of the electro - deintercalation lithium extraction device, determine the initial operating parameters of the hydrodynamic model and the electrochemical model and the model boundary conditions of the physical geometry model respectively;

[0068] S4. Conduct mesh generation for the physical geometry model, and perform mesh encryption on the boundaries of the model region during the mesh generation process;

[0069] S5. Couple the hydrodynamic model and the electrochemical model, and perform numerical solution on the obtained coupled model using the finite element analysis method. After extracting the calculation results, complete the numerical simulation.

[0070] In step S2, the finite element volume method is used to construct the hydrodynamic model; the electrochemical model includes a charge transfer kinetics model and / or an ion migration kinetics model, and the Butler–Volmer equation is used to construct the charge transfer kinetics model, and the Nernst–Planck equation is used to construct the ion migration kinetics model.

[0071] Specifically, based on the conservation law, the finite element volume method divides the calculation region into a series of control volumes, and then applies the integral - form conservation equations to each control volume, thereby ensuring the conservation of physical quantities (such as mass, momentum, etc.) and improving the accuracy of the hydrodynamic model.

[0072] The method provided by the present invention can establish mathematical models for processes such as flow, polarization, and mass transfer through numerical simulation and calculation. By combining hydrodynamic and electrochemical principles and coupling and solving multiple mathematical models, it can accurately describe the electro - deintercalation lithium extraction process, pre - calculate various data in the process of extracting lithium from salt lakes, and reveal the variation laws of key indicators of electro - deintercalation lithium extraction, which is helpful to improve the lithium extraction efficiency and the stability of the lithium extraction process.

[0073] In some embodiments, the physical geometry model described in step S1 includes a two - dimensional geometry model or a three - dimensional geometry model.

[0074] In the present invention, a uniform voltage is applied to the boundary electrodes of the chamber for the two - dimensional geometry model, and the three - dimensional geometry model can be provided with pole ears and a coating material layer and exists in the form of a current - conducting flat - plate electrode.

[0075] In the present invention, when it is only necessary to reveal the laws reflecting the lithium extraction efficiency, such as the internal lithium ion concentration and the intensity of the reaction in the electro - deintercalation and lithium extraction device under influencing factors such as the current formulation and the applied voltage, through numerical simulation methods, the physical and geometric model constructed in step S1 is a two - dimensional geometric model; when it is necessary to explore in detail the influence of factors such as the position of the tab and the internal flow channels of the chamber on the uniformity of the lithium extraction reaction inside the electro - deintercalation and lithium extraction device, the physical and geometric model constructed in step S1 is a three - dimensional geometric model.

[0076] The main difference between the above - mentioned two - dimensional geometric model and three - dimensional geometric model lies in the different amounts of calculation for numerical simulation, and the three - dimensional geometric model requires a larger amount of calculation. In addition, the two - dimensional geometric model focuses on the overall electro - deintercalation and lithium extraction effect of the reaction and the intensity of the reaction inside the device; the three - dimensional geometric model focuses on exploring the influence of the internal structural details of the electro - deintercalation and lithium extraction device on the lithium extraction effect.

[0077] Among them, the model regions obtained by dividing the two - dimensional geometric model include: the anode coating boundary, the anode chamber, the anion exchange membrane, the cathode coating boundary, and the cathode chamber; the model regions obtained by dividing the three - dimensional geometric model include: the anode coating region, the anode chamber, the anion exchange membrane, the cathode coating region, and the cathode chamber.

[0078] In some embodiments, during the construction of the hydrodynamic model in step S2, it is set that the fluid states in the anode chamber and the cathode chamber are both laminar flows.

[0079] In the present invention, the fluid state in the chamber is set as a laminar flow, that is, the fluid flows in the form of parallel layers, and there is no turbulence and mixing between the layers, and the velocity gradient between the layers is very small. This is because in the laminar flow state, the velocity distribution of the fluid is uniform, without vortices and disturbances in the turbulence, thereby reducing the complexity of the calculation, and finally making the prediction of the flow easier and more accurate.

[0080] In some embodiments, the construction of the hydrodynamic model in step S2 is based on the mass conservation equation (see Equation 1) and the momentum conservation equation (see Equation 2), and the specific equations are as follows:

[0081]

[0082] In the above formula: ρ is the density of water; t is time; is the divergence operator; is the velocity vector.

[0083]

[0084] In the above formula: p is the surface tension; is the shear force; g is the acceleration due to gravity.

[0085] Among them, the stress tensor The calculation method is as follows:

[0086]

[0087] In the above formula: μ is the hydrodynamic viscosity; is the velocity of the transposed vector; I is the unit tensor. In addition, the electrode reaction equation involving charge migration in the electrochemically deintercalating and extracting lithium process is as follows:

[0088] Anode LiFePO 4 -e - →Li + +FePO 4

[0089] Cathode FePO 4 +Li + +e - →LiFePO 4

[0090] In the present invention, the charge transfer kinetic model is used to characterize the rate of the electrochemical reaction and analyze the polarization current density. The Butler–Volmer equation is as follows:

[0091]

[0092] In the above formula: i 0 is the exchange current density; α a and α c are both mass transfer coefficients, usually taking a value of 0.5; i loc,expr is the polarization current density; F is the Faraday constant; R is the molar gas constant; T is the solution temperature.

[0093] Among them, η is the overpotential potential, and the relationship between the overpotential potential and the applied potential and the electrolyte potential is as follows:

[0094] η = φ s -φ l -E eq Equation 5

[0095] In the above formula: φ s is the applied potential, taking a value of 0.35 V in the electrochemically deintercalating and extracting lithium device; φ l is the electrolyte potential; E eq is the electrode equilibrium potential.

[0096] Among them, E eq can be obtained from the Nernst equation, specifically as follows:

[0097]

[0098] In the above formula: Eeq,ref (T) is the standard equilibrium potential, which can be obtained from experiments; T is the temperature; v is the stoichiometric coefficient; c ref is the reference concentration of the electrolyte; c is the concentration of the electrolyte; n is the number of electron transfers.

[0099] In the present invention, the Butler–Volmer equation is one of the most fundamental charge transfer kinetic relationships in the field of electrochemistry, which describes how the current on the electrode changes with the electrode potential. Although this equation is essentially an empirical relationship, its constitutive coefficients can only be determined through electrochemical experiments rather than independent prediction, thus making the equation have a solid theoretical basis and experimental data support, increasing the reliability and practicality of the model.

[0100] In the present invention, the ion migration kinetic model is used to characterize the ion migration processes such as mass transfer, diffusion, and convection in the process of electro-extraction and intercalation of lithium. The Nernst–Planck equation is as follows:

[0101]

[0102] In the above formula: N is the lithium ion flux; D is the diffusion coefficient of the ion, which can be obtained from experiments; z is the charge number of the lithium ion; u m is the migration coefficient of the lithium ion; F is the Faraday constant; φ l is the electrolyte potential; u is the electrolyte flow rate; this equation respectively represents the effects of diffusion, electro-migration, and convection on the migration of lithium ions.

[0103] In the present invention, the Nernst–Planck equation is an important tool for describing the migration and diffusion kinetics of ions under the influence of an electric field and a concentration gradient. It not only describes the ion diffusion caused by the concentration gradient but also describes the ion migration caused by the potential gradient. This comprehensive description enables the model to more accurately capture the behavior of ions in the electrolyte, improving the reliability of model prediction.

[0104] In the present invention, according to Faraday's law and the principle of electrolyte electroneutrality, the expression of the electrolyte current density i l is as follows:

[0105]

[0106] In addition, according to the charge conservation, the electrolyte potential can be calculated as:

[0107]

[0108] In the above formula: R is the internal resistance of the electrolyte.

[0109] In some embodiments, after the hydrodynamic model and the electrochemical model described in step S2 are constructed, a mathematical model of the anion exchange membrane and / or a mathematical model of the storage tank are further constructed.

[0110] By constructing a mathematical model of the anion exchange membrane and / or a mathematical model of the storage tank, and combining the original hydrodynamic model and electrochemical model, the present invention can more comprehensively describe the multi-physical field coupling phenomena of the entire electroextraction and deintercalation lithium device, such as mass transfer, charge transfer, and electrochemical reactions, further improving the accuracy and applicability of the entire system model.

[0111] In the present invention, the anion exchange membrane is composed of a polymer electrolyte, and additional positive charges are fixed in the polymer matrix, enabling anions to pass through the membrane body. In the ion exchange membrane domain, when calculating the total charge under the condition of electrical neutrality, a fixed space charge ρ is added fix , and the process of anions passing through the ion membrane can be modeled as follows:

[0112]

[0113] In the above formula: F is the Faraday constant; z is the ionic charge value; c is the ionic concentration.

[0114] In the present invention, if a transient electroextraction and deintercalation lithium process is simulated, a mathematical model of the storage tank for brine and / or lithium-rich liquid needs to be established.

[0115] Specifically, assuming that the brine or lithium-rich liquid flowing out of the outlet of the brine or lithium-rich liquid chamber in the electroextraction and deintercalation lithium device flows back into their respective storage tanks, and after mixing, is introduced again into the electroextraction and deintercalation lithium device at the electroextraction inlet for electroextraction reaction, then the instantaneous inflow lithium ion concentration in the brine or lithium-rich liquid chamber can be modeled in the form of a differential equation, specifically as follows:

[0116]

[0117] In the above formula: V is the volume of the storage tank; L is the thickness of the electroextraction membrane stack; is the Li + concentration in the storage tank; is the flux of Li + in the electrolyte in the direction of the boundary normal; n is the direction of the boundary outer normal; dS is the boundary curve of Li + inflow or outlet.

[0118] In addition, by integrating the flux of Li + in the direction of the boundary outer normal of the inflow or outlet boundary to obtain the difference in the flux of Li + at the inlet and outlet, the product of it and L can represent the change in the Li + content in the storage tank, that is

[0119] In some embodiments, if the physical geometry model in step S1 is a two-dimensional geometry model, the initial operating parameters in step S3 include: standard exchange current density, fixed charge concentration of the anion exchange membrane, porosity of the anion exchange membrane, diffusion coefficient of lithium ions, diffusion coefficient of chloride ions, standard equilibrium electrode potential of the anode, standard equilibrium electrode potential of the cathode, mass transfer coefficient, and initial concentration of the solution in the chamber.

[0120] In some embodiments, if the physical geometry model in step S1 is a three-dimensional geometry model, the initial operating parameters in step S3 include: standard exchange current density, fixed charge concentration of the anion exchange membrane, porosity of the anion exchange membrane, conductivity of the electrode coating area, diffusion coefficient of lithium ions, diffusion coefficient of chloride ions, standard equilibrium electrode potential of the anode, standard equilibrium electrode potential of the cathode, mass transfer coefficient, and initial concentration of the solution in the chamber.

[0121] In the present invention, the determination of the initial operating parameters provides a starting point for numerical simulation and affects the accuracy and reliability of the simulation results. The above parameters not only describe the physical properties of the electro-extraction and insertion lithium device and the internal fluid, but also describe the chemical properties related to the electrochemical reaction, which are crucial for the accuracy and effectiveness of the simulation process.

[0122] In some embodiments, the standard exchange current density is 10 A / m 2 to 30 A / m 2 , for example, it can be 10 A / m 2 , 12 A / m 2 , 14 A / m 2 , 16 A / m 2 , 18 A / m 2 , 20 A / m 2 , 22 A / m 2 , 24 A / m 2 , 26 A / m 2 , 28 A / m 2 or 30 A / m 2 , but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0123] In some embodiments, the fixed charge concentration of the anion exchange membrane is 1×10 6 C / m 3 to 1×10 10 C / m 3 , for example, it can be 1×10 6 C / m 3 , 5×10 6 C / m 3 , 1×10 7 C / m 3 , 5×107 C / m 3 , 1×10 8 C / m 3 , 5×10 8 C / m 3 , 1×10 9 C / m 3 , 5×10 9 C / m 3 or 1×10 10 C / m 3 , but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0124] In some embodiments, the porosity of the anion membrane is 40% to 60%, for example, it can be 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58% or 60%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0125] In some embodiments, the conductivity of the electrode coating region includes the conductivity of the anode coating region and the conductivity of the cathode coating region, which are independently 1×10 4 S / m to 5×10 4 S / m, for example, can be 1×10 4 S / m, 1.5×10 4 S / m, 2×10 4 S / m, 2.5×10 4 S / m, 3×10 4 S / m, 3.5×10 4 S / m, 4×10 4 S / m, 4.5×10 4 S / m or 5×10 4 S / m, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0126] In some embodiments, the diffusion coefficient of lithium ions includes the diffusion coefficient D1 of lithium ions in the solution and the diffusion coefficient D2 of lithium ions in the anion membrane, and D1 is 2×10 -8 m 2 / s to 3×10 -8 m 2 / s, for example, it can be 2×10 -8 m 2 / s, 2.2×10 -8 m 2 / s, 2.4×10 -8 m 2 / s, 2.6×10 -8 m2 / s, 2.8×10 -8 m 2 / s or 3×10 -8 m 2 / s, D2 is 1×10 - 10 m 2 / s to 3×10 -10 m 2 / s, for example, it can be 1×10 -10 m 2 / s, 1.2×10 -10 m 2 / s, 1.4×10 -10 m 2 / s, 1.6×10 - 10 m 2 / s, 1.8×10 -10 m 2 / s, 2×10 -10 m 2 / s, 2.2×10 -10 m 2 / s, 2.4×10 -10 m 2 / s, 2.6×10 -10 m 2 / s, 2.8×10 -10 m 2 / s or 3×10 -10 m 2 / s, but not limited to the listed values, and other unlisted values within this range are also applicable.

[0127] In some embodiments, the diffusion coefficient of the chloride ions includes the diffusion coefficient d1 of the chloride ions in the solution and the diffusion coefficient d2 of the chloride ions in the anion membrane, and d1 is 1×10 -8 m 2 / s to 3×10 -8 m 2 / s, for example, it can be 1×10 -8 m 2 / s, 1.2×10 -8 m 2 / s, 1.4×10 -8 m 2 / s, 1.6×10 -8 m 2 / s, 1.8×10 -8 m 2 / s, 2×10 -8 m 2 / s, 2.2×10 -8 m2 / s, 2.4×10 -8 m 2 / s, 2.6×10 -8 m 2 / s, 2.8×10 -8 m 2 / s or 3×10 -8 m 2 / s, d2 is 1×10 -9 m 2 / s to 5×10 -6 m 2 / s, for example, it can be 1×10 -9 m 2 / s, 5×10 -9 m 2 / s, 1×10 -8 m 2 / s, 5×10 -8 m 2 / s, 1×10 -7 m 2 / s, 5×10 -7 m 2 / s, 1×10 -6 m 2 / s or 5×10 -6 m 2 / s, but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0128] In some embodiments, the standard equilibrium electrode potential of the anode is -0.6V to -1.0V, for example, it can be -0.6V, -0.7V, -0.8V, -0.9V or -1.0V, but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0129] In some embodiments, the standard equilibrium electrode potential of the cathode is 0.8V to 1.2V, for example, it can be 0.8V, 0.9V, 1.0V, 1.1V or 1.2V, but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0130] In some embodiments, the mass transfer coefficient is 0.4 to 0.6, for example, it can be 0.4, 0.42, 0.44, 0.46, 0.48, 0.5, 0.52, 0.54, 0.56, 0.58 or 0.6, but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0131] In some embodiments, the initial concentration of the solution in the chamber includes the initial lithium ion concentration and the initial chloride ion concentration of the solutions in the anode chamber and the cathode chamber, which are independently 0 - 20 mol / m 3 , but not including 0, for example, it can be 2 mol / m 3 , 4 mol / m 3 , 6 mol / m 3 , 8 mol / m 3 , 10 mol / m 3 , 12 mol / m 3 , 14 mol / m 3 , 16 mol / m 3 , 18 mol / m 3 or 20 mol / m 3 , but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0132] In some embodiments, if the physical geometry model in step S1 is a two-dimensional geometry model, then the model boundary conditions in step S3 include the electrode coating boundary, the chamber inlet, the chamber outlet, the inlet solution flow rate, the inlet lithium ion concentration, and the external electric potential.

[0133] In some embodiments, if the physical geometry model in step S1 is a three-dimensional geometry model, then the model boundary conditions in step S3 include the electrode coating area, the chamber inlet, the chamber outlet, the inlet solution flow rate, the inlet lithium ion concentration, and the external electric potential.

[0134] In numerical simulation calculations, the setting of the model boundary conditions directly affects the accuracy and reliability of the simulation results. The boundary conditions are the conditions used to describe the behavior or state of physical quantities on the model boundary in numerical simulations. The model boundary conditions and the initial operating parameters jointly act on the dynamic evolution process of the model, and the initial operating parameters determine the state at which the model starts to evolve, while the model boundary conditions continuously affect and adjust the behavior of the model during the evolution process.

[0135] In some embodiments, the electrode coating boundary includes the anode coating boundary and the cathode coating boundary.

[0136] In some embodiments, the electrode coating area includes the anode coating area and the cathode coating area.

[0137] In some embodiments, the chamber inlet includes the anode chamber inlet and the cathode chamber inlet.

[0138] In some embodiments, the chamber outlet includes the anode chamber outlet and the cathode chamber outlet.

[0139] In some embodiments, the inlet solution flow rate includes the anode chamber inlet flow rate and the cathode chamber inlet flow rate, which are independently 6 cm / s to 10 cm / s respectively. For example, it can be 6 cm / s, 6.5 cm / s, 7 cm / s, 7.5 cm / s, 8 cm / s, 8.5 cm / s, 9 cm / s, 9.5 cm / s or 10 cm / s, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0140] In some embodiments, the inlet lithium ion concentration includes the anode chamber inlet lithium ion concentration and the cathode chamber inlet lithium ion concentration, and the anode chamber inlet lithium ion concentration is 15 mol / m 3 to 25 mol / m 3 , for example, it can be 15 mol / m 3 , 16 mol / m 3 , 17 mol / m 3 , 18 mol / m 3 , 19 mol / m 3 , 20 mol / m 3 , 21 mol / m 3 , 22 mol / m 3 , 23 mol / m 3 , 24 mol / m 3 or 25 mol / m 3 , and the cathode chamber inlet lithium ion concentration is 100 mol / m 3 to 200 mol / m 3 , for example, it can be 100 mol / m 3 , 110 mol / m 3 , 120 mol / m 3 , 130 mol / m 3 , 140 mol / m 3 , 150 mol / m 3 , 160 mol / m 3 , 170 mol / m 3 , 180 mol / m 3 , 190 mol / m 3 or 200 mol / m 3 , but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0141] In some embodiments, the external electric potential includes an anode external electric potential and a cathode external electric potential, and the anode external electric potential is from 0.3V to 0.4V. For example, it can be 0.3V, 0.31V, 0.32V, 0.33V, 0.34V, 0.35V, 0.36V, 0.37V, 0.38V, 0.39V or 0.4V. The cathode external electric potential is from -0.5V to 0V. For example, it can be -0.5V, -0.4V, -0.3V, -0.2V, -0.1V or 0V, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0142] In some embodiments, the mesh generation in step S4 includes surface mesh generation or volume mesh generation. The surface mesh generation is for two-dimensional geometric models, and the volume mesh generation is for three-dimensional geometric models.

[0143] In some embodiments, the volume mesh generation includes tetrahedral mesh generation and / or hexahedral mesh generation.

[0144] In some embodiments, the mesh refinement process in step S4 includes: uniformly dividing the mesh in the direction parallel to the current, and the cell division ratio is 1:a; the cell division ratio of the anion membrane and the main solution part in the direction perpendicular to the current is 1:b; the cell division ratio near the boundary of the anion membrane and the electrolyte is 1:c. By controlling a < b ≤ c, the mesh refinement process is achieved. This is because the reaction concentration changes violently and the concentration gradient is large in the very thin electrolyte chamber region, and precise calculation requires a high-density mesh.

[0145] In some embodiments, the computational equations involved in the coupling process in step S5 include the mass conservation equation, the momentum conservation equation, the Butler–Volmer equation, and the Nernst–Planck equation.

[0146] Specifically, the coupling process is a mathematical model that comprehensively considers two physical fields of hydrodynamics and electrochemistry. The hydrodynamic model and the electrochemical model are not independent of each other, but interact and influence each other through various physical and chemical processes.

[0147] Among them, the hydrodynamic model focuses on the motion laws of fluids, including the velocity field, pressure field, temperature field, etc. of the fluid. The changes of the above physical quantities follow basic principles such as mass conservation, momentum conservation, and energy conservation; the electrochemical model focuses on the electrochemical reaction process, including charge transfer, oxidation-reduction reactions of substances, current density distribution, etc., and mainly involves charge transfer kinetics, ion transport in electrolytes and other phenomena.

[0148] In the coupled model of hydrodynamics and electrochemistry, the interaction between hydrodynamics and electrochemistry can be achieved in various ways. For example, in the electro-extraction and intercalation lithium system, the flow of fluid can affect the ion transport process of the electrochemical reaction, while the electrochemical reaction will affect the concentration distribution of substances in the fluid and the dynamic characteristics of the fluid.

[0149] In some embodiments, the numerical solution includes transient solution or steady-state solution.

[0150] In the present invention, the numerical solution needs to rely on professional calculation software. As long as it can handle the multi-physical field coupling problem and provide the corresponding solver, the specific name of the calculation software is not particularly limited herein.

[0151] In addition, the transient solution and the steady-state solution are respectively two main analysis types used to describe the behavior of the model over time in numerical simulation. Among them, the transient solution obtains the process of physical quantities changing over time, focusing on the entire change process of the model from the initial state to the stable state; the steady-state solution focuses on the stable state reached by the model after long-term operation, and at this time the physical quantities no longer change with time.

[0152] In some embodiments, the calculation results include the internal potential distribution of the cavity, current density or ion concentration distribution.

[0153] In some embodiments, the extraction timing of the calculation results is: the numerical solution reaches the convergence condition, that is, the numerical calculation results gradually stabilize during the iterative process, indicating that the calculation results are close enough to the true solution.

[0154] Among them, the determination criteria for the convergence condition include residual monitoring, physical quantity stability, satisfaction of conservation laws or continuity of contour plots.

[0155] Specifically, the residual monitoring refers to monitoring the difference between the numerical calculation results and the true values in real time. During the iterative calculation process, the residuals of each physical quantity will be calculated and output. When the absolute value change of the residuals is less than the preset convergence threshold, it is considered that the calculation results have converged. The physical quantity stability refers to monitoring some representative flow variables or physical quantities, such as temperature, velocity, flow rate, force or torque, etc. When these physical quantities are basically unchanged during the iterative process, it indicates that convergence has been achieved. The satisfaction of the conservation laws includes flux conservation. In the absence of mass source terms and energy source terms, the net value of the mass flow rate at the inlet and outlet should be very small, close to 0; the total heat transfer rate of each wall surface should also be close to 0, which indicates that the flow is conserved and can be used as a basis for judging convergence. The continuity of the contour plot refers to checking whether the contour plot is continuous. A contour plot with spots and jagged edges is a sign that the calculation has not converged or the mesh is too rough.

[0156] Example 1

[0157] This embodiment provides a numerical simulation method for electro - deintercalation lithium extraction, specifically including the following steps:

[0158] S1. According to the flow field region and electrode coating region of the electro - deintercalation lithium extraction device, use three - dimensional modeling and simulation software to construct a two - dimensional geometric model, and divide the model region for the two - dimensional geometric model.

[0159] As Figure 2 shown, the model regions included in the two - dimensional geometric model are, from left to right: anode coating boundary 1, anode chamber (lithium - rich liquid chamber) 2, anion membrane 3, cathode chamber (brine chamber) 4, and cathode coating boundary 5.

[0160] Among them, the heights of both the anode chamber (lithium - rich liquid chamber) 2 and the cathode chamber (brine chamber) 4 are 200 mm, and the widths are both 1 mm. This embodiment uses a minimum membrane stack unit in the flow field region of the electro - deintercalation lithium extraction device, and the actual device is composed of several pairs of similar small units.

[0161] S2. Combine the hydrodynamic and electrochemical principles of the electro - deintercalation lithium extraction process to construct a hydrodynamic model and an electrochemical model respectively.

[0162] Among them, the finite - element volume method is used to construct the hydrodynamic model, and the fluid states in the anode chamber and the cathode chamber are set to laminar flow. At the same time, based on the mass conservation equation (see Equation 1) and the momentum conservation equation (see Equation 2); the electrochemical model includes a charge transfer kinetics model and an ion migration kinetics model. The Butler–Volmer equation (see Equation 4) is used to construct the charge transfer kinetics model, and the Nernst–Planck equation (see Equation 7) is used to construct the ion migration kinetics model.

[0163] S3. According to the actual operating conditions of the electro - deintercalation lithium extraction device, determine the initial operating parameters of the hydrodynamic model and the electrochemical model, as well as the model boundary conditions of the two - dimensional geometric model respectively.

[0164] Specifically, the initial operating parameters include: the standard exchange current density is 20 A / m 2 , the fixed charge concentration of the anion membrane is 1×10 8 C / m 3 , the porosity of the anion membrane is 50%, the diffusion coefficient of lithium ions in the solution is 2.5×10 -8 m 2 / s, the diffusion coefficient of lithium ions in the anion membrane is 2×10 -10 m 2 / s, the diffusion coefficient of chloride ions in the solution is 2×10 -8 m 2 / s, the diffusion coefficient of chloride ions in the anion membrane is 1×10 -6 m 2 / s, the standard equilibrium electrode potential of the anode is -0.8V, the standard equilibrium electrode potential of the cathode is 1V, the mass transfer coefficient is 0.5, and the initial lithium ion concentration and the initial chloride ion concentration in the solutions in the anode chamber and the cathode chamber are both 15mol / m 3 .

[0165] In addition, the settings of the model boundary conditions are as Figure 3 shown. In the clockwise direction, they are: anode coating boundary 1, anode chamber outlet 8, cathode chamber outlet 9, cathode coating boundary 5, cathode chamber inlet 7, and anode chamber inlet 6; the flow rates at the anode chamber inlet and the cathode chamber inlet are both set to 8cm / s, the lithium ion concentration at the anode chamber inlet is 20mol / m 3 , the lithium ion concentration at the cathode chamber inlet is 150mol / m 3 , the external potential of the anode is 0.35V, and the external potential of the cathode is 0V.

[0166] S4. Perform surface mesh generation for the two-dimensional geometric model, and during the surface mesh generation process, perform mesh encryption on the boundaries of the anion membrane.

[0167] Specifically, the meshes are evenly divided in the direction parallel to the current direction, and the cell division ratio is 1:1. In the direction perpendicular to the current direction, the cell division ratio of the anion membrane and the main solution part is 1:5, and the cell division ratio near the boundary of the anion membrane and the electrolyte is 1:5, so as to achieve mesh encryption (see Figure 4 ).

[0168] S5. Couple the hydrodynamic model and the electrochemical model. The calculation equations involved include the mass conservation equation, the momentum conservation equation, the Butler–Volmer equation, and the Nernst–Planck equation. Then, use the finite element analysis method to perform transient solution on the obtained coupled model. Set the solution time step to 0.1h, the initial time to 0h, and the stop time to 10h. If the error decreases with the increase of the iteration times during the calculation process and finally tends to be stable, and its time step increases and the reciprocal of the step size decreases, showing a downward trend, it indicates that the calculation process reaches the convergence condition.

[0169] Obtain data such as the internal potential distribution and lithium / chloride ion concentration distribution in the cavity of the electro-extraction and de-insertion lithium device. In this embodiment, after 10h of transient simulation, the changes in the lithium ion concentrations in the cathode chamber (brine chamber) and the anode chamber (lithium-rich liquid chamber) are as Figure 5 shown.

[0170] From Figure 5It can be seen that within 10 h, the process of lithium deintercalation and intercalation through electrochemical reaction continues. On the anode side (lithium-rich solution), the lithium ions increase from 20 mol / m 3 to 160 mol / m 3 , while on the cathode side (brine), the lithium ions decrease from 150 mol / m 3 to 10 mol / m 3 .

[0171] Figure 6 Figure 5 is the distribution contour map of lithium ions at 2 h of the reaction, Figure 7 and Figure 6 is the lithium ion concentration distribution at the boundary of the anion exchange membrane at 2 h of the reaction.

[0172] From Figure 6 and Figure 7 , it can be seen that the process of electro-extraction of lithium by deintercalation and intercalation occurs more violently closer to the outlet of the chamber. Moreover, as the reaction progresses, the lithium extraction reaction occurs more towards the side away from the membrane, ultimately achieving a high lithium enrichment in the anode chamber.

[0173] Thus, it can be seen that in this embodiment, through numerical simulation and calculation, a mathematical model is established for processes such as flow, polarization, and mass transfer. Combining the principles of fluid dynamics and electrochemistry, multiple mathematical models are coupled and solved, which can accurately describe the process of electro-extraction of lithium by deintercalation and intercalation, pre-calculate various data in the process of extracting lithium from salt lakes, reveal the variation laws of the key indicators of electro-extraction of lithium by deintercalation and intercalation, and help improve the efficiency and stability of the lithium extraction process.

[0174] Embodiment 2

[0175] This embodiment provides a numerical simulation method for electro-extraction of lithium by deintercalation and intercalation, which specifically includes the following steps:

[0176] S1. According to the flow field region and the electrode coating region of the electro-extraction device for lithium by deintercalation and intercalation, a three-dimensional geometric model is constructed on the basis of the two-dimensional geometric model obtained in Embodiment 1 by using three-dimensional modeling and simulation software, and the model region is divided for the three-dimensional geometric model.

[0177] As Figure 8 shown, the model regions included in the three-dimensional geometric model are, from left to right: anode coating region 1a, anode chamber (lithium-rich solution chamber) 2, anion exchange membrane 3, cathode chamber (brine chamber) 4, and cathode coating region 5a.

[0178] Among them, the anode chamber (lithium-rich solution chamber) 2 and the cathode chamber (brine chamber) 4 both have a height of 200 mm, a width of 100 mm, and a depth of 1 mm.

[0179] S2. Combining the principles of fluid dynamics and electrochemistry in the process of electro-extraction of lithium by deintercalation and intercalation, a fluid dynamics model and an electrochemistry model are respectively constructed.

[0180] Among them, the finite element volume method is used to construct the hydrodynamic model, and the fluid states in the anode chamber and the cathode chamber are set to laminar flow. At the same time, based on the mass conservation equation (see Equation 1) and the momentum conservation equation (see Equation 2); the electrochemical model includes a charge transfer kinetics model and an ion migration kinetics model. The charge transfer kinetics model is constructed using the Butler–Volmer equation (see Equation 4), and the ion migration kinetics model is constructed using the Nernst–Planck equation (see Equation 7).

[0181] S3. According to the actual operating conditions of the electro-extraction and lithium intercalation device, determine the initial operating parameters of the hydrodynamic model and the electrochemical model, as well as the model boundary conditions of the three-dimensional geometric model, respectively.

[0182] Specifically, the initial operating parameters include: the standard exchange current density is 20 A / m 2 , the fixed charge concentration of the anion exchange membrane is 1×10 8 C / m 3 , the porosity of the anion exchange membrane is 50%, the conductivity of the anode coating area and the conductivity of the cathode coating area are both 5×10 4 S / m, the diffusion coefficient of lithium ions in the solution is 2.5×10 -8 m 2 / s, the diffusion coefficient of lithium ions in the anion exchange membrane is 2×10 -10 m 2 / s, the diffusion coefficient of chloride ions in the solution is 2×10 -8 m 2 / s, the diffusion coefficient of chloride ions in the anion exchange membrane is 1×10 -6 m 2 / s, the standard equilibrium electrode potential of the anode is -0.8 V, the standard equilibrium electrode potential of the cathode is 1 V, the mass transfer coefficient is 0.5, and the initial lithium ion concentration and the initial chloride ion concentration in the solutions in the anode chamber and the cathode chamber are both 15 mol / m 3 .

[0183] In addition, the setting of the model boundary conditions includes: setting the electrode coating area as a current conductance area and adding conductivity. Both the anode chamber and the cathode chamber adopt the form of bottom-in and top-out, and the inlet flow rate and the lithium ion concentration in the solution are set in sequence. Among them, the inlet flow rate of the anode chamber and the inlet flow rate of the cathode chamber are both set to 8 cm / s, the inlet lithium ion concentration of the anode chamber is 20 mol / m 3 , the inlet lithium ion concentration of the cathode chamber is 150 mol / m 3 , the external potential of the anode is 0.35 V, and the external potential of the cathode is 0 V.

[0184] S4. Perform hexahedral mesh generation on the three-dimensional geometric model, and during the hexahedral mesh generation process, perform mesh encryption on the boundaries of the anion exchange membrane.

[0185] Specifically, the meshes are evenly divided in the direction parallel to the current, and the cell division ratio is 1:1. In the direction perpendicular to the current, the cell division ratio of the anion exchange membrane and the main solution part is 1:5, and the cell division ratio near the boundary between the anion exchange membrane and the electrolyte is 1:5, thereby achieving mesh encryption (see Figure 9 ).

[0186] S5. Couple the hydrodynamic model and the electrochemical model. The computational equations involved include the mass conservation equation, the momentum conservation equation, the Butler–Volmer equation, and the Nernst–Planck equation. Then, use the finite element analysis method to perform a steady-state solution on the obtained coupled model. Set the solution time step to 0.1 h, the initial time to 0 h, and the stop time to 10 h. If the error decreases with the increase in the number of iterations during the calculation process until it reaches 10 -5 , and finally tends to be stable, it indicates that the calculation process reaches the convergence condition.

[0187] Figure 10 This is the contour map of the lithium ion concentration distribution inside the electroextraction / insertion model. It can be seen that the lithium extraction reaction occurs more violently in the chambers near both sides of the membrane, and due to the influence of the electrolyte flow, the lithium extraction reaction becomes more violent at the boundary.

[0188] Figure 11 This is the change in the lithium ion concentration at the junction of the lithium-rich liquid chamber / brine chamber on the anode / cathode tab side and the anion exchange membrane. As the solution flows into the inside of the membrane stack, the lithium ion concentration in the lithium-rich liquid at the boundary increases due to lithium extraction, and the lithium ion concentration on the brine side decreases due to intensified lithium insertion.

[0189] In addition, the lithium ion concentration increases at 0.02 m (anode tab position) of the membrane stack in the lithium-rich liquid chamber on the anode tab side, while the lithium ion concentration decreases at 0.18 m (cathode tab position) of the membrane stack in the brine chamber on the cathode tab side. This is because the potential distribution in the chamber is uneven, the potential is weak at the cathode tab, and the potential is high at the anode tab. Eventually, a phenomenon of locally high current density at the tab occurs, which accelerates and promotes the lithium extraction effect.

[0190] It can be seen that in this embodiment, through numerical simulation and calculation, a mathematical model is established for processes such as flow, polarization, and mass transfer. Combining the principles of hydrodynamics and electrochemistry, multiple mathematical models are coupled and solved, which can accurately describe the electroextraction / insertion lithium extraction process, pre-calculate various data during the salt lake lithium extraction process, reveal the variation laws of the key indicators of electroextraction / insertion lithium extraction, and contribute to improving the lithium extraction efficiency and the stability of the lithium extraction process.

[0191] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A numerical simulation method for lithium electrolysis, characterized in that: The numerical simulation method comprises the following steps: S1. constructing a physical geometric model according to the flow field area and the electrode coating area of ​​the lithium electro-deintercalation device, and dividing the model area according to the physical geometric model; S2. Combining the fluid dynamics and electrochemical principles of the lithium electroextraction process, a fluid dynamics model and an electrochemical model are constructed respectively; S3. According to the actual operating conditions of the electric deintercalation and lithium extraction device, the initial operating parameters of the fluid dynamics model and the electrochemical model and the model boundary conditions of the physical geometry model are determined respectively; S4, meshing the physical geometric model, and performing mesh encryption on the boundary of the model area during the meshing process; S5, coupling the fluid dynamics model and the electrochemical model, numerically solving the obtained coupling model using the finite element analysis method, and completing the numerical simulation after extracting the calculation results; In step S2, the fluid dynamics model is constructed using the finite element volume method; the electrochemical model includes a charge transfer kinetics model and / or an ion migration kinetics model, and the charge transfer kinetics model is constructed using the Butler–Volmer equation, and the ion migration kinetics model is constructed using the Nernst–Planck equation.

2. The numerical simulation method according to claim 1, characterized in that: The physical geometric model in step S1 includes a two-dimensional geometric model or a three-dimensional geometric model; The model regions obtained by dividing the two-dimensional geometric model include: an anode coating boundary, an anode chamber, an anion membrane, a cathode coating boundary and a cathode chamber; The model regions obtained by dividing the three-dimensional geometric model include: an anode coating region, an anode chamber, an anion membrane, a cathode coating region and a cathode chamber.

3. The numerical simulation method according to claim 2, characterized in that: In the process of constructing the fluid dynamics model in step S2, the fluid states in the anode chamber and the cathode chamber are set to be laminar flow; And / or, the construction of the fluid dynamics model in step S2 is based on the mass conservation equation and the momentum conservation equation.

4. The numerical simulation method according to claim 3, characterized in that: After the fluid dynamics model and the electrochemical model are constructed in step S2, a mathematical model of the anion membrane and / or a mathematical model of the storage tank are also constructed.

5. The numerical simulation method according to claim 3 or 4, characterized in that: When the physical geometric model in step S1 is a two-dimensional geometric model, the initial operating parameters in step S3 include: standard exchange current density, fixed charge concentration of the anion membrane, porosity of the anion membrane, diffusion coefficient of lithium ions, diffusion coefficient of chloride ions, standard equilibrium electrode potential of the anode, standard equilibrium electrode potential of the cathode, mass transfer coefficient and initial concentration of the solution in the chamber; When the physical geometric model described in step S1 is a three-dimensional geometric model, the initial operating parameters described in step S3 include: standard exchange current density, fixed charge concentration of the anion membrane, porosity of the anion membrane, conductivity of the electrode coating area, diffusion coefficient of lithium ions, diffusion coefficient of chloride ions, standard equilibrium electrode potential of the anode, standard equilibrium electrode potential of the cathode, mass transfer coefficient and initial concentration of the solution in the chamber.

6. The numerical simulation method according to claim 5, characterized in that: The standard exchange current density is 10A / m 2 Up to 30A / m 2 ; And / or, the fixed charge concentration of the anion membrane is 1×10 6 C / m 3 Up to 1×10 10 C / m 3 ; and / or, the porosity of the anion membrane is 40% to 60%; And / or, the conductivity of the electrode coating region includes the conductivity of the anode coating region and the conductivity of the cathode coating region, which are independently 1×10 4 S / m to 5×10 4 S / m; And / or, the diffusion coefficient of lithium ions includes the diffusion coefficient D1 of lithium ions in the solution and the diffusion coefficient D2 of lithium ions in the anion membrane, and D1 is 2×10 -8 m 2 / s to 3×10 -8 m 2 / s, D2 is 1×10 -10 m 2 / s to 3×10 -10 m 2 / s; And / or, the diffusion coefficient of chloride ions includes the diffusion coefficient d1 of chloride ions in the solution and the diffusion coefficient d2 of chloride ions in the anion membrane, and d1 is 1×10 -8 m 2 / s to 3×10 -8 m 2 / s, d2 is 1×10 -9 m 2 / s to 5×10 -6 m 2 / s; And / or, the anode standard equilibrium electrode potential is -0.6V to -1.0V; And / or, the cathode standard equilibrium electrode potential is 0.8V to 1.2V; And / or, the mass transfer coefficient is 0.4 to 0.6; And / or, the initial concentration of the solution in the chamber includes the initial lithium ion concentration and the initial chloride ion concentration of the solution in the anode chamber and the cathode chamber, which are independently 0-20 mol / m 3 , but not including 0.

7. The numerical simulation method according to claim 5, characterized in that: When the physical geometric model in step S1 is a two-dimensional geometric model, the model boundary conditions in step S3 include electrode coating boundary, chamber inlet, chamber outlet, inlet solution flow rate, inlet lithium ion concentration and external potential; When the physical geometric model in step S1 is a three-dimensional geometric model, the model boundary conditions in step S3 include the electrode coating area, the chamber inlet, the chamber outlet, the inlet solution flow rate, the inlet lithium ion concentration and the external potential.

8. The numerical simulation method according to claim 7, characterized in that: The electrode coating boundary includes an anode coating boundary and a cathode coating boundary; And / or, the electrode coating region includes an anode coating region and a cathode coating region; And / or, the chamber inlet includes an anode chamber inlet and a cathode chamber inlet; And / or, the chamber outlet includes an anode chamber outlet and a cathode chamber outlet; And / or, the inlet solution flow rate includes the anode chamber inlet flow rate and the cathode chamber inlet flow rate, which are independently 6 cm / s to 10 cm / s; And / or, the inlet lithium ion concentration includes the inlet lithium ion concentration of the anode chamber and the inlet lithium ion concentration of the cathode chamber, and the inlet lithium ion concentration of the anode chamber is 15 mol / m 3 To 25 mol / m 3 The lithium ion concentration at the cathode chamber inlet is 100 mol / m 3 Up to 200 mol / m 3 ; And / or, the external potential includes an anode external potential and a cathode external potential, and the anode external potential is 0.3V to 0.4V, and the cathode external potential is -0.5V to 0V.

9. The numerical simulation method according to claim 7, characterized in that: The meshing in step S4 includes surface meshing or volume meshing, and the surface meshing is for a two-dimensional geometric model, and the volume meshing is for a three-dimensional geometric model; And / or, the volume meshing includes tetrahedral meshing and / or hexahedral meshing; And / or, the grid encryption processing described in step S4 includes: uniformly dividing the grid in the direction parallel to the current, and the cell division ratio is 1:a, the cell division ratio of the anion membrane and the main solution part perpendicular to the current direction is 1:b, and the cell division ratio near the anion membrane and the electrolyte boundary is 1:c, controlling a<b≤c, thereby realizing grid encryption processing.

10. The numerical simulation method according to claim 9, characterized in that: The calculation equations involved in the coupling process in step S5 include the mass conservation equation, the momentum conservation equation, the Butler–Volmer equation and the Nernst–Planck equation; And / or, the numerical solution includes a transient solution or a steady-state solution; And / or, the calculation results include potential distribution, current density or ion concentration distribution inside the cavity; And / or, the timing of extracting the calculation result is: the numerical solution reaches a convergence condition; The convergence condition determination criteria include residual monitoring, physical quantity stability, satisfaction of conservation laws or continuity of cloud diagrams.

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