A brief discussion on five hot research tools for lithium-ion batteries -Lithium - Ion Battery Equipment
In the field of lithium-ion batteries, due to the uncertainty of the impact of various parameters on battery performance, experimental design has a certain degree of blindness. The traditional exhaustive method to determine parameters has the disadvantages of heavy tasks, low efficiency, and is difficult to solve theoretical problems.
With the development of simulation technology, simulation technology has been applied to the research and development of more and more scientific research fields. As a complementary tool for experiments, COMSOL Multiphysics can:
(1) Before the experiment, simulate each experimental method through battery modeling, predict the experimental results, narrow the parameter range, and improve work efficiency.
(2) Simulating the internal electrochemical processes during battery operation helps researchers study the internal processes of the battery. Through the simplification, simulation and analysis of the battery model, the battery working status can be managed more effectively.
(3) Combined with experimental data, the content of the article is persuasive, predictable, and novel, and can be published in high-end journals in the field.
Currently, the five research hotspots of lithium-ion batteries, including thermal management, polarization phenomena, SEI film stability, and electrode/electrolyte interface issues, can all be simulated through COMSOL Multiphysics.
1. Application of COMSOLMultiphysics in battery thermal management
With the continuous upgrading of power equipment, batteries have begun to gradually develop in the direction of large size and modularization. The problem of battery heat generation has become increasingly prominent. Battery thermal management has also become one of the focuses of current research in the battery field. During the charging and discharging process, heat occurs inside the battery. If it is not dissipated in time, the temperature will rise and exceed the normal operating range of lithium-ion batteries: (safe temperature range), which will affect the battery's working conditions, cycle efficiency, capacity, Performance such as power will in turn affect the reliability, safety and life of the equipment. Establishing a thermal model of lithium-ion batteries is a basic method to study the temperature distribution and changes of lithium-ion batteries. By studying the thermal effects of the battery, the battery structure can be optimized and the safety characteristics of the battery can be improved.(Lithium - Ion Battery Equipment)
COMSOL Multiphysics provides sufficient physics interfaces, which can help users study the thermal effects of lithium-ion batteries by coupling the lithium-ion battery interface and the heat transfer interface. The software has a simple and clear interface for setting boundary conditions, making it easy for users to get started. At the same time, it also has a clear visual interface, which can intuitively observe the temperature distribution within the lithium-ion battery.
Under the same discharge rate condition, during convection heat dissipation, the higher the external heat transfer coefficient, the lower the battery temperature. This can help us design the size and shape of the radiator based on the heat transfer coefficient when designing the external radiator. It also shows that the greater the discharge rate, the higher the battery temperature. The important reason is that when discharging at a high rate, there are more side reactions, the internal resistance of the battery increases, and the ohmic heat and side reaction heat increase at the same time, resulting in an obvious thermal effect of the battery. This requires Continuously optimize battery structure and process battery materials to reduce battery side reactions. It also shows that the electrolyte concentration distribution is flatter under adiabatic conditions than isothermal conditions, indicating that the diffusion performance of the electrolyte under adiabatic conditions is better than that under isothermal conditions, providing new ideas and insights for the study of lithium-ion batteries. direction.
2. Application of COMSOLMultiphysics in battery capacity fading
In lithium-ion batteries, in addition to the redox reactions that occur when lithium ions are deintercalated, there are also a large number of side reactions, such as electrolyte decomposition, active material dissolution, and metallic lithium deposition. Side reactions and degradation processes can lead to various adverse effects that are irreversible and can cause a loss of battery capacity. Typically, batteries age due to multiple complex phenomena and reactions occurring simultaneously at different locations. During the load cycle, the battery is at different stages and its degree of degradation is different, depending on potential, local concentration, temperature, and current flow. direction. Different battery materials have different aging levels, and the combination of different materials (such as the cross-effect of electrode materials) may further accelerate aging. COMSOLM Multiphysics can help researchers establish battery aging models and conduct quantitative analysis of various factors leading to battery aging. It can clearly understand the causes of battery aging, establish research goals, and focus on overcoming important issues to improve scientific research efficiency and accelerate lithium-ion The development process of batteries.
It can be seen from the model in the figure above that as the number of cycles of lithium-ion batteries increases and the discharge rate increases, the battery capacity gradually decreases. Especially when the discharge rate exceeds 1C, the discharge capacity decays significantly. At 4C, before the battery voltage reaches 3V, the battery only has about 50% of its theoretical capacity. A large number of studies have proven that the gradual thickening of the SEI film caused by battery side reactions is an important reason for the attenuation of battery capacity. Therefore, we can also use COMSOL Multiphysic to study the relationship between SEI film changes with time, study the SEI film formation mechanism, and enhance the stability of the SEI film. Reduce negative electrode/electrolyte interface impedance.
3. Application of COMSOLMultiphysics in analyzing battery short circuit
During the charging process, the battery forms lithium dendrites and pierces the battery separator, causing an internal short circuit of the battery, or is punctured by external machinery, causing a short circuit of the battery. Prolonged internal short circuits can cause battery self-discharge and local temperature rise. If the temperature exceeds a certain value, the electrolyte may begin to decompose due to thermal reactions, leading to thermal runaway, which not only reduces battery cycle performance but also poses safety risks to the battery. COMSOL Multiphysics can be used to model and analyze the thermal runaway problem caused by battery short circuit.
4. Application of COMSOLMultiphysics in analyzing battery electrochemical impedance spectroscopy
Electrochemical impedance spectroscopy (EIS) is one of the most powerful tools for studying the electrochemical processes occurring at the electrode/electrolyte interface, and is widely used to study the intercalation and extraction processes of lithium ions in active materials of lithium-ion battery chimeric electrodes. Applying a frequency-varying potential perturbation to a battery electrode, the impedance response can provide insight into multiple battery properties and processes: At high frequencies, shorter time scale processes such as capacitance, electrochemical reactions, and local resistance affect impedance. On the other hand, at low frequencies, the diffusion of electrolytes and active materials also affects the impedance. COMSOLM Multiphysics can be used to analyze the EIS characteristics of the chimeric electrode, and discuss the attribution of the time constant in the EIS spectrum, focusing on the relevant kinetic parameters during the insertion and extraction process of lithium ions in the positive and negative active materials, such as charge transfer resistance, active materials The electronic resistance, diffusion, and resistance of lithium ion diffusion and migration through the SEI film depend on the electrode polarization potential and temperature.
5. Application of COMSOLMultiphysics in analyzing the ratio of battery electrode materials
In order to improve the stability of battery electrode materials, the positive and negative electrodes usually contain a variety of intercalation materials, especially the positive electrode material, which is usually a mixture of multiple materials, such as transition metal oxides, multilayer oxides, and olivine. These materials can have different design properties (such as volume fraction and particle size), thermodynamic properties (such as equilibrium site and maximum lithium ion concentration), transport properties (such as solid diffusion coefficient), and kinetic properties (such as intercalation reaction rate constants). ). Different material ratios will have a great impact on the overall performance of the battery. If experiments are used to continuously find the optimal ratio, the workload will be large and the efficiency will not be high. Using COMSOL Multiphysics to analyze different material ratios through battery modeling can reduce the workload, thereby reducing the research scope of experimental parameters and saving manpower and material resources.
Summarize
With the rapid development of science and technology, lithium-ion battery research no longer blindly relies on experimental research. Instead, it first uses software to model the battery, predicts various aspects of battery performance through electrochemical simulation, and then formulates detailed experimental methods. , carry out experimental verification. At present, the latest version of COMSOL Multiphysics 5.4 has added a battery equivalent circuit module and a lumped battery module, which allows users to build their own models more conveniently according to their work needs. At the same time, it also has a mathematical module, so that when the existing physical interface cannot meet the modeling needs, users can flexibly use the mathematical interface according to the modeling needs to build a more accurate model. We believe that with the gradual optimization of simulation software, more and more researchers will use finite element simulation software such as COMSOL Multiphysics to study battery mechanisms in the future. When publishing an article, users can use software analysis data to enrich the content of the article, making the overall content of the article rich and beautiful, and the framework logic clear, helping researchers publish the article to high-level journals in the field, and at the same time improving the impact factor of the article.
With the development of simulation technology, simulation technology has been applied to the research and development of more and more scientific research fields. As a complementary tool for experiments, COMSOL Multiphysics can:
(1) Before the experiment, simulate each experimental method through battery modeling, predict the experimental results, narrow the parameter range, and improve work efficiency.
(2) Simulating the internal electrochemical processes during battery operation helps researchers study the internal processes of the battery. Through the simplification, simulation and analysis of the battery model, the battery working status can be managed more effectively.
(3) Combined with experimental data, the content of the article is persuasive, predictable, and novel, and can be published in high-end journals in the field.
Currently, the five research hotspots of lithium-ion batteries, including thermal management, polarization phenomena, SEI film stability, and electrode/electrolyte interface issues, can all be simulated through COMSOL Multiphysics.
1. Application of COMSOLMultiphysics in battery thermal management
With the continuous upgrading of power equipment, batteries have begun to gradually develop in the direction of large size and modularization. The problem of battery heat generation has become increasingly prominent. Battery thermal management has also become one of the focuses of current research in the battery field. During the charging and discharging process, heat occurs inside the battery. If it is not dissipated in time, the temperature will rise and exceed the normal operating range of lithium-ion batteries: (safe temperature range), which will affect the battery's working conditions, cycle efficiency, capacity, Performance such as power will in turn affect the reliability, safety and life of the equipment. Establishing a thermal model of lithium-ion batteries is a basic method to study the temperature distribution and changes of lithium-ion batteries. By studying the thermal effects of the battery, the battery structure can be optimized and the safety characteristics of the battery can be improved.(Lithium - Ion Battery Equipment)
COMSOL Multiphysics provides sufficient physics interfaces, which can help users study the thermal effects of lithium-ion batteries by coupling the lithium-ion battery interface and the heat transfer interface. The software has a simple and clear interface for setting boundary conditions, making it easy for users to get started. At the same time, it also has a clear visual interface, which can intuitively observe the temperature distribution within the lithium-ion battery.
Under the same discharge rate condition, during convection heat dissipation, the higher the external heat transfer coefficient, the lower the battery temperature. This can help us design the size and shape of the radiator based on the heat transfer coefficient when designing the external radiator. It also shows that the greater the discharge rate, the higher the battery temperature. The important reason is that when discharging at a high rate, there are more side reactions, the internal resistance of the battery increases, and the ohmic heat and side reaction heat increase at the same time, resulting in an obvious thermal effect of the battery. This requires Continuously optimize battery structure and process battery materials to reduce battery side reactions. It also shows that the electrolyte concentration distribution is flatter under adiabatic conditions than isothermal conditions, indicating that the diffusion performance of the electrolyte under adiabatic conditions is better than that under isothermal conditions, providing new ideas and insights for the study of lithium-ion batteries. direction.
2. Application of COMSOLMultiphysics in battery capacity fading
In lithium-ion batteries, in addition to the redox reactions that occur when lithium ions are deintercalated, there are also a large number of side reactions, such as electrolyte decomposition, active material dissolution, and metallic lithium deposition. Side reactions and degradation processes can lead to various adverse effects that are irreversible and can cause a loss of battery capacity. Typically, batteries age due to multiple complex phenomena and reactions occurring simultaneously at different locations. During the load cycle, the battery is at different stages and its degree of degradation is different, depending on potential, local concentration, temperature, and current flow. direction. Different battery materials have different aging levels, and the combination of different materials (such as the cross-effect of electrode materials) may further accelerate aging. COMSOLM Multiphysics can help researchers establish battery aging models and conduct quantitative analysis of various factors leading to battery aging. It can clearly understand the causes of battery aging, establish research goals, and focus on overcoming important issues to improve scientific research efficiency and accelerate lithium-ion The development process of batteries.
It can be seen from the model in the figure above that as the number of cycles of lithium-ion batteries increases and the discharge rate increases, the battery capacity gradually decreases. Especially when the discharge rate exceeds 1C, the discharge capacity decays significantly. At 4C, before the battery voltage reaches 3V, the battery only has about 50% of its theoretical capacity. A large number of studies have proven that the gradual thickening of the SEI film caused by battery side reactions is an important reason for the attenuation of battery capacity. Therefore, we can also use COMSOL Multiphysic to study the relationship between SEI film changes with time, study the SEI film formation mechanism, and enhance the stability of the SEI film. Reduce negative electrode/electrolyte interface impedance.
3. Application of COMSOLMultiphysics in analyzing battery short circuit
During the charging process, the battery forms lithium dendrites and pierces the battery separator, causing an internal short circuit of the battery, or is punctured by external machinery, causing a short circuit of the battery. Prolonged internal short circuits can cause battery self-discharge and local temperature rise. If the temperature exceeds a certain value, the electrolyte may begin to decompose due to thermal reactions, leading to thermal runaway, which not only reduces battery cycle performance but also poses safety risks to the battery. COMSOL Multiphysics can be used to model and analyze the thermal runaway problem caused by battery short circuit.
4. Application of COMSOLMultiphysics in analyzing battery electrochemical impedance spectroscopy
Electrochemical impedance spectroscopy (EIS) is one of the most powerful tools for studying the electrochemical processes occurring at the electrode/electrolyte interface, and is widely used to study the intercalation and extraction processes of lithium ions in active materials of lithium-ion battery chimeric electrodes. Applying a frequency-varying potential perturbation to a battery electrode, the impedance response can provide insight into multiple battery properties and processes: At high frequencies, shorter time scale processes such as capacitance, electrochemical reactions, and local resistance affect impedance. On the other hand, at low frequencies, the diffusion of electrolytes and active materials also affects the impedance. COMSOLM Multiphysics can be used to analyze the EIS characteristics of the chimeric electrode, and discuss the attribution of the time constant in the EIS spectrum, focusing on the relevant kinetic parameters during the insertion and extraction process of lithium ions in the positive and negative active materials, such as charge transfer resistance, active materials The electronic resistance, diffusion, and resistance of lithium ion diffusion and migration through the SEI film depend on the electrode polarization potential and temperature.
5. Application of COMSOLMultiphysics in analyzing the ratio of battery electrode materials
In order to improve the stability of battery electrode materials, the positive and negative electrodes usually contain a variety of intercalation materials, especially the positive electrode material, which is usually a mixture of multiple materials, such as transition metal oxides, multilayer oxides, and olivine. These materials can have different design properties (such as volume fraction and particle size), thermodynamic properties (such as equilibrium site and maximum lithium ion concentration), transport properties (such as solid diffusion coefficient), and kinetic properties (such as intercalation reaction rate constants). ). Different material ratios will have a great impact on the overall performance of the battery. If experiments are used to continuously find the optimal ratio, the workload will be large and the efficiency will not be high. Using COMSOL Multiphysics to analyze different material ratios through battery modeling can reduce the workload, thereby reducing the research scope of experimental parameters and saving manpower and material resources.
Summarize
With the rapid development of science and technology, lithium-ion battery research no longer blindly relies on experimental research. Instead, it first uses software to model the battery, predicts various aspects of battery performance through electrochemical simulation, and then formulates detailed experimental methods. , carry out experimental verification. At present, the latest version of COMSOL Multiphysics 5.4 has added a battery equivalent circuit module and a lumped battery module, which allows users to build their own models more conveniently according to their work needs. At the same time, it also has a mathematical module, so that when the existing physical interface cannot meet the modeling needs, users can flexibly use the mathematical interface according to the modeling needs to build a more accurate model. We believe that with the gradual optimization of simulation software, more and more researchers will use finite element simulation software such as COMSOL Multiphysics to study battery mechanisms in the future. When publishing an article, users can use software analysis data to enrich the content of the article, making the overall content of the article rich and beautiful, and the framework logic clear, helping researchers publish the article to high-level journals in the field, and at the same time improving the impact factor of the article.
