CN-119152955-B - Simulation method for SOC variation of electrolyte of iron-chromium flow battery based on molecular dynamics

CN119152955BCN 119152955 BCN119152955 BCN 119152955BCN-119152955-B

Abstract

The invention discloses a simulation method for the SOC change of an electrolyte of an iron-chromium flow battery based on molecular dynamics, which constructs a molecular dynamics model of the electrolyte of the iron-chromium flow battery of different SOCs at specific temperature by establishing the electrolyte model of the iron-chromium flow battery of different SOCs, demonstrates the reliability of the model in terms of diffusion coefficient, coordination number, viscosity, density and the like, can effectively obtain the constitution relation between molecules and ions in the electrolyte, predicts the electrochemical property of the electrolyte, further optimizes the composition of the electrolyte, is beneficial to improving the power, capacity and stability of the iron-chromium flow battery, and accurately explores the influence of the SOCs on the physicochemical properties of the electrolyte by calculating and analyzing the change of the physical property and the chemical property of the electrolyte along with the change of the SOCs based on the molecular dynamics simulation, thereby having guiding significance for the subsequent optimization of the electrolyte of the iron-chromium flow battery and the improvement of the performance of the iron-chromium flow battery.

Inventors

NIU YINGCHUN
TAN DONGMEI
XU QUAN
WANG SHEN
ZENG JIANHUA
LIU WANLI

Assignees

中海储能科技(北京)有限公司

Dates

Publication Date: 20260512
Application Date: 20240724

Claims (10)

1. The simulation method for the SOC variation of the electrolyte of the iron-chromium flow battery based on the molecular dynamics is characterized by comprising the following steps of: Step S1, establishing a molecular dynamics model of an electrolyte of the iron-chromium flow battery based on molecular dynamics, wherein the electrolyte comprises ferrous ions Fe 2+ , ferric ions Fe 3+ , bivalent chromium ions Cr 2+ , trivalent chromium ions Cr 3+ , chloride ions Cl - and hydrogen ions H + , and the solvent is water H 2 O; s2, selecting a proper model potential energy parameter to be distributed in system particles based on the researched electrolyte of the iron-chromium flow battery, wherein the model potential energy parameter is one or more selected from REBO, reaxFF, AMBER IOD, TIP4P and TIP4P-EW potential functions; S3, constructing an electrolyte molecular simulation system containing Fe 2+ , fe 3+ 、Cr 3+ , cr 2+ , HCl hydrochloride and water, wherein the quantity of Fe 2 + 、Fe 3+ and Cr 3+ 、Cr 2+ is respectively set according to different SOCs; s4, setting an ensemble and boundary conditions for molecular dynamics simulation; s5, carrying out isovolumetric ensemble NVT balance simulation on the molecular dynamics simulation system of the electrolyte of the iron-chromium flow battery at high temperature and outputting a result file, setting temperature under the isothermal and isobaric ensemble NPT, and carrying out simulation with energy and density balance as targets to output the result file; S6, calculating the self-diffusion coefficient of each system under the isothermal and isobaric ensemble NPT according to the result file, and calculating the viscosity of the electrolyte system in the micro regular ensemble NVE; and S7, processing the atom running track by adopting Visual Molecular Dynamics visual software VMD, and calculating the radial distribution and coordination condition of the ions and the water atoms.
2. The method for simulating the change of the SOC of the electrolyte of the iron-chromium flow battery based on molecular dynamics according to claim 1, wherein in the step S1, a molecular dynamics model of the electrolyte of the iron-chromium flow battery is built by using PACKMOL and MOLTEMPLATE software, and the data file contains information of the side length of a simulated cube box, the initial coordinates of atoms, and the bond angles and dihedral angles between the atoms.
3. The simulation method of the SOC variation of the electrolyte of the iron-chromium flow battery based on molecular dynamics according to claim 1, wherein in the step S3, the SOC is selected to be 0%, 25%, 50%, 75% and 100%, and the SOC is set to be 0% when the number ratio of Fe 2+ to Fe 3+ is set to be 100:0.
4. The simulation method for the change of the electrolyte SOC of the iron-chromium flow battery based on molecular dynamics is characterized in that in the step S4, molecular dynamics simulation calculation is performed by using LAMMPS software, in the step S5, equal volume ensemble NVT balance simulation is performed on an electrolyte molecular dynamics simulation system of the iron-chromium flow battery at high temperature by using a three-dimensional periodic boundary condition, the time step is 0.1 fs, water molecules are a TIP4P-EW force field model, bond angles and bond lengths of the water molecules are fixed by using a fix shake command, long-range acting force in the equal volume ensemble NVT balance simulation is solved by using a PPPM method, the balance temperature is 1000K, and the balance time is 10ps.
5. The molecular dynamics-based fe—cr flow battery electrolyte SOC variation simulation method as set forth in claim 1, wherein the medium Wen Dengya ensemble NPT in step S5 is set to 330K using a Noose-Hoover thermostat and isopiester annealed system target temperature and 200ps equilibrium is performed, the temperature damping parameter is 100 fs, the pressure damping parameter is 100 fs, and the density of the system is output.
6. The method for simulating the change of the SOC of the electrolyte of the iron-chromium flow battery based on molecular dynamics as claimed in claim 1, wherein the self-diffusion coefficient of each system is calculated under Wen Dengya ensemble NPT in the step S5, the equilibrium temperature is 330K, the equilibrium time is 40ps by using Eistein method, the time step is 0.01 and fs by using three-dimensional periodic boundary conditions, the water molecules adopt TIP4P-EW force field model, and the bond angles and bond lengths of the water molecules are fixed by using fix shake command.
7. The simulation method of the change of the electrolyte SOC of the iron-chromium flow battery based on molecular dynamics according to claim 1, wherein in the step S6, the viscosity of an electrolyte system is calculated in a micro regular ensemble NVE, a Green-Kubo method is adopted, the equilibrium temperature is 330K, the equilibrium time is 1000ps, a three-dimensional periodic boundary condition is adopted, the time step is 0.1 fs, a TIP4P-EW force field model is adopted for water molecules, and a fix key angle and a key length of the water molecules are instructed by using a fix wave.
8. The simulation method of the SOC variation of the electrolyte of the iron-chromium flow battery based on molecular dynamics according to claim 1, wherein the self-diffusion coefficient calculation formula in the step S6 is as follows: ; Wherein, the The position vector of the particle at time t is shown, D is the self-diffusion coefficient of the particle, and t is the simulation time.
9. The simulation method of the SOC variation of the electrolyte of the iron-chromium flow battery based on molecular dynamics according to claim 1, wherein the viscosity calculation formula of the electrolyte system in the step S6 is as follows: ; Wherein, the Is a boltzmann constant, In order to simulate the volume of the model, As an off-diagonal component of the stress tensor, The viscosity of the electrolyte system is represented by T, the simulated temperature of the electrolyte, T 0 , the starting time of simulation and the total time of simulation.
10. The simulation method of the SOC variation of the electrolyte of the iron-chromium flow battery based on molecular dynamics according to claim 1, wherein the coordination condition in the step S7 is calculated as follows: ; wherein n is the coordination number, For the number density of the particles, Is the radius of the center particle, and the radius of the center particle, For a given radial particle-to-center particle distribution function, the calculation formula is as follows: ; Wherein, the As the total number of molecules, For the total time of the simulation, In order to set the difference in distance, Is that Number of molecules between; is the radius of the center particle, and the radius of the center particle, Is the number density of particles.

Description

Simulation method for SOC variation of electrolyte of iron-chromium flow battery based on molecular dynamics Technical Field The invention relates to the field of flow battery simulation, in particular to a simulation method for SOC variation of an electrolyte of an iron-chromium flow battery based on molecular dynamics. Background The flow battery has the outstanding advantages of high safety, long cycle life, flexible design and the like, is an energy storage component which is most suitable for building a large-scale energy storage system and has great progress in commercial application. The iron-chromium flow battery is an earliest flow battery technology, adopts low-cost metal iron and chromium as active substances, and is hopeful to become energy storage equipment with high cost performance. The electrolyte is the core material of the iron-chromium flow battery for storing energy, and the reaction characteristic of the electrode/electrolyte interface directly influences and determines the performance of the battery. SOC is a key index for measuring the capacity of a battery, is greatly influenced by the physical property and chemical property change of electrolyte, can effectively obtain the constitution relation between molecules and ions in the electrolyte by establishing an electrolyte simulation model of the iron-chromium flow battery, predicts the electrochemical property of the electrolyte, and further optimizes the composition of the electrolyte, thereby being beneficial to improving the power, the capacity and the stability of the iron-chromium flow battery. The molecular dynamics method is based on classical Newton's equation of motion and interaction potential between atoms, carries out Newton's equation of motion numerical integration to speed and atress of each particle, and has more accurate approximate expression to force and thermal properties and dynamics rule of a microscopic system. The molecular dynamics simulation has the characteristics of low experiment cost, high safety and capability of realizing experiments which are difficult or impossible to perform under normal conditions, and can effectively explore the complex relationship between molecules and ions in the electrolyte of the iron-chromium flow battery and accurately calculate various properties and parameters of the electrolyte under different SOCs. In addition, the simulation of the electrolyte of the iron-chromium flow battery is less at present, and a corresponding molecular dynamics simulation model is not established. Accordingly, researchers in the field have been working to develop a method for simulating and analyzing the SOC variation properties of an electrolyte of an iron-chromium flow battery based on molecular dynamics. Disclosure of Invention In view of the fact that the existing iron-chromium flow battery electrolyte has less research on molecular dynamics simulation, the invention aims to overcome the defects of the prior art, and provides an iron-chromium flow battery electrolyte SOC variation simulation method based on molecular dynamics, which constructs a molecular dynamics model of iron-chromium flow battery electrolyte with different SOCs at a specific temperature by establishing iron-chromium flow battery electrolyte models with different SOCs, demonstrates the reliability of the model in terms of diffusion coefficient, coordination number, viscosity, density and the like, the method can effectively obtain the composition relation between molecules and ions in the electrolyte, predicts the electrochemical property of the electrolyte, further optimizes the composition of the electrolyte, is favorable for improving the power, capacity and stability of the iron-chromium flow battery, accurately explores the influence of the SOC on various physical and chemical properties of the electrolyte by calculating and analyzing the change of the physical property and the chemical property of the electrolyte along with the change of the SOC based on molecular dynamics simulation, and has guiding significance for optimizing the electrolyte of the iron-chromium flow battery and improving the performance of the iron-chromium flow battery. In order to achieve the technical effects, the following technical scheme is adopted: the simulation method for the SOC variation of the electrolyte of the iron-chromium flow battery based on molecular dynamics comprises the following steps: Step S1, establishing a molecular dynamics model of an electrolyte of the iron-chromium flow battery based on molecular dynamics, wherein the electrolyte comprises ferrous ions Fe 2+, ferric ions Fe 3+, bivalent chromium ions Cr 2+, trivalent chromium ions Cr 3+, chloride ions Cl - and hydrogen ions H +, and the solvent is water H 2 O; Using Packmol software to build ferrous ion (Fe 2+), ferric ion (Fe 3+), chromium (Cr 2+), chromium (Cr 3+), water molecule (H 2 O), hydrogen ion (H +), chloride ion (Cl -) models; The distance constraint toleran