Electrochemical-thermal Coupling Model Research Articles

Thermal Performance of a Cylindrical Li[Ni0.6Co0.2Mn0.2]O2/Graphite Battery based on the Electrochemical-Thermal Coupling Model

The thermal safety of lithium-ion batteries has garnered significant attention due to its pivotal role in the field of new energy. In this work, a three-dimensional electrochemical-thermal coupling model based on the P2D model was established for predicting the thermal performance. The charge-discharge and temperature rise experiments via 18650 cylindrical Li[Ni0.6Co0.2Mn0.2]O2 / graphite batteries are designed to confirm the rationality of the model. The simulation results show that the highest temperature of the battery surface during discharging at 1 C and 4 C are 42.85 °C and 61.25 °C, and the experimental results are 42.50 °C and 62.85 °C, respectively. The electrode heat generation mainly comes from the reaction heat of cathode and anode during 1 C charge process, the maximum power is 1.2 W and 0.6 W, respectively. In the discharge process, the cathode dominates the reaction contribution of 1.02 W and the reaction heat power from the anode is only 0.016 W. The capacity of heat dissipation can be increased by enhancing the convective heat transfer coefficient and air velocity within a reasonable range. The proposed electrochemical-thermal coupling model is valuable to evaluate the heat behavior and promote the battery development.

Editor's Note for article entitled “An electrochemical-thermal coupling model for heat generation analysis of prismatic lithium battery”

Editor's Note for article entitled “An electrochemical-thermal coupling model for heat generation analysis of prismatic lithium battery”

Investigation on heat generation in fast charging of lithium-ion batteries: Effect of charging rate and battery component thickness

Understanding heat generation mechanisms during fast charging is essential for designing and optimizing lithium-ion batteries. In this study, we have formulated a three-dimensional electrochemical-thermal coupling model for pouch lithium-ion batteries. The model is validated by the experimental results based on the distribution of temperature, current, and voltage. We investigate the effects of charging rate, active material coating thickness, and current collector thickness (each at three levels) on heat generation and temperature distribution. The electrodes account for most of the total heat generation (87.5% with a 2.5C charging rate), and the percentage decreases as the charging rate increases. The heat generated at the negative electrode is slightly higher than that at the positive electrode. Reversible heat is the main heat source at a low charging rate, and it decreases as the charging rate rises. The effects of battery component thicknesses on thermal behaviors under fast charging are significant. The overall battery temperature increases by 11.5 K as the positive electrode thickness increases from 40 to 70 µm due to the rise in ohmic resistance and polarization resistance within the electrode. The increased ohmic resistance in the separator and the current collector raises the temperature. Reducing the thickness of the current collector by 33% resulted in a doubling of heat generation from the current collectors. Yet, it had minimal impact on the overall temperature of the battery.

Direct reconstruction of the temperature field of lithium-ion battery based on mapping characteristics

Lithium-ion (Li-ion) batteries are susceptible to the working temperature so that the monitoring is essential to the battery internal temperature. The electrochemical-thermal coupling model completely reflects the battery internal behavior. However, the high complexity and multi-field coupling make it difficult to be applied to reconstruct the battery temperature field based on state observer. Based on mapping characteristics, this work proposes a temperature field direct reconstruction scheme. And the electrochemical-thermal coupling model plays a large role in this scheme. Mapping characteristic vectors of the transient temperature field are obtained from the step response model of the Li-ion battery temperature field to charge and discharge current. Furthermore, the quantitative connection of the mapping characteristic vectors between the surface points of and the internal nodes of the battery is characterized by a relevance degree matrix. And a direct reconstruction model of the internal transient temperature field is established. The internal temperature field is reconstructed directly online and in real time via exploiting the temperature measurements on battery surface. In numerical experiments, the three-dimensional temperature field of the Li-ion battery charge and discharge processes is reconstructed. The effects of charge and discharge rates, model mismatch, and measurement errors on the reconstruction results are investigated. During the charge and discharge processes, the maximum values of the transient average error of the reconstructed temperature field are about 0.4 K and 0.3 K, respectively. And the transient average error is generally below 0.8 K when the standard deviation of measurement errors is 0.5 K.

The exploration of the internal homogeneities for a LiFePO4 pouch lithium-ion battery with a 3D electrochemical-thermal coupled model

Along with the battery charge/discharge processes, the migration of the Li ions inevitably leads to an inhomogeneous distribution of the battery internal electrochemical and thermal characteristics, deteriorating the battery capacity and safety. In this work, the internal characteristics of a 20 Ah pouch LiFePO4 lithium-ion battery have been investigated based on a 3D electrochemical-thermal coupled model. It is found that the reduction of the particle size for either the cathode or anode would increase the battery capacity. Moreover, with the modulation of the thickness of cathode (Lpos) and convective heat transfer coefficient (h), the homogeneity of solid lithium concentration and temperature has been optimized. A relatively smaller Lpos and an h higher than the critical value should be adopted. From the aspect of thermal distribution, as the discharge rate increases, the irreversible reaction heat always dominates, while the proportion of ohmic heat among the total heat increases, and the high temperature region always locates on the inner sides of the tabs. The methodology proposed in this work could be applied to pouch batteries with more repeated cell units and larger sizes.

An Electrochemical-Thermal Coupling Model Based on Two-Factor Parameter Modification for Lithium-Ion Battery

Abstract The accurate establishment of battery model can improve the design reliability and reduce the design risk, which provides an important basis for the research of battery. First, the key parameters of the Li-ion battery model are identified by the least square method based on the full-battery equivalent circuit model of the single-particle impedance spectrum, and the diffusion coefficient and exchange current density under different temperatures and SOC conditions are calculated. At the same time, the one-dimensional thermal rate model is used as the heat source of the three-dimensional model, and the mean temperature T of the three-dimensional model is calculated by using Fourier's law, and T is fed back to the one-dimensional model as the key parameter to modify the conductivity, diffusion coefficient, and exchange current density, and a semi-empirical electrochemical-thermal coupling model with two-factor parameter modification is established. Finally, the model is verified by the temperature field distribution and discharge voltage curve at different discharge rates. The maximum temperature difference is less than 3.1 °C, and the maximum voltage difference error is less than 0.131 V. The results show that the improved model can accurately reflect the influence of temperature on the model parameters, and has high accuracy in the estimation of battery terminal voltage and SOC.

An electrochemical-thermal coupling model for lithium-ion battery state-of-charge estimation with improve dual particle filter framework

Lithium-ion battery state-of-charge (SOC) estimation plays an indispensable role in the battery management system functionalities. To achieve SOC estimation with high accuracy, a precise battery model is required. Among various battery models, electrochemical model (EM) stands out for its ability to provide insights into the electrochemical mechanisms of the battery. However, the model parameters will vary with the battery running and aging, besides, the model-based methods cannot well handle the model errors. Therefore, to ensure estimation accuracy, selecting a more insightful battery model and a more effective estimation algorithm becomes crucial. This paper proposes an electrochemical model-based SOC estimation method with online parameter adjustment and an optimized algorithm. Firstly, a single particle model (SPM) with electrolyte and thermal dynamics is introduced and simplified by an approximate solution. Secondly, the particle swarm optimization (PSO) method is used to solve the problem of the particle filter (PF) algorithm, such as particle degradation and particle diversity decrease. Finally, during SOC estimating, a double-scale dual particle filter (D-PF) is utilized to adjust parameters as battery aging and temperature changes. The battery tests are applied under different working conditions and temperatures. Experimental results show that the error of SOC estimation reduces significantly compared to the previous electrochemical model-based method, and the proposed method has a higher accuracy and effectiveness.

Research on the heating effect evaluation of the electromagnetic induction heating system at low temperature based on the electrochemical-thermal coupling model

The extremely fast electromagnetic induction heating system (EIHS) was recently introduced to improve the poor charge and discharge performance of lithium-ion batteries (LiBs) at low temperature. In this work, aimed to investigate the heating effect of EIHS, the accurate electrochemical-thermal coupling model, validated against the charging capacity calibration with various C-rates and HPPC tests at different environments, was developed in depth to reflect the electrochemical and heat transfer behaviors of the LiB exposed to external cool air during the electromagnetic induction heating process. When the copper coil was subjected to a sinusoidal alternating current (SAC) excitation at 10 A, 3 kHz, the LiB can be warmed up to 293.15 K from 243.15 K within 742 s with an even heat generation inside the LiB. The impact of the SAC parameters on the needed heating time was illustrated with time maps, a series of contours suggested that the heating velocity increase with the increase of both the amplitude and frequency. As compared with the low-temperature state, the internal resistance had a more than 3-fold decrease, which can improve the discharging voltage platform and terminal voltage output, thus increasing the pulse power and usable capacity. Neither noticeable capacity retention difference before and after the heating cycles nor obvious capacity loss discrepancy between the normal charge-discharge and heating cycle tests was found at the end of the 200 heating cycles, so the EIHS can achieve a good tradeoff among temperature rising effect, working behaviors and LiB cycle lifespan, which had a considerable potential to enhance the applicability of EVs (electric vehicles) in frigid weather. Moreover, a better heat transfer condition, higher material thermal conductivity and lower specific heat capacity play an important positive role on the improvement of temperature rising performance.

High-Frequency AC Heating Strategy of Electric Vehicle Power Battery Pack in Low-Temperature Environment.

In this paper, a heating strategy using high-frequency alternating current (AC) is proposed to internally heat lithium-ion batteries (LIB) at low temperatures. The strategy aims to strike a good balance between rapid heating of the battery at low temperatures and minimizing damage to the battery's lifespan without the need for an additional power source. The strategy presents an electrochemical-thermal coupling model to simulate and predict the temperature rise and temperature distribution of a 50 A h LiFePO4 square battery at different C-rates, the effect of high-frequency AC on battery life, and the validity of the model as verified by experiments. The experimental and simulation results show that this strategy can achieve faster heating speeds and better temperature consistency without affecting battery life. The best heating effect can be achieved at a frequency of 500 Hz (4.2C), and the temperature of the battery rises from 253.15 to 278.15 K within 365 s, for an average heating rate of 3.29 K/min. Researching low-temperature AC heating methods has important value for energy conservation because it can improve heating efficiency, expand application areas, promote technological innovation, and enhance product quality.

Numerical investigation and parameter optimization on a rib-grooved liquid-cooled plate for lithium battery thermal management system

To increase the effectiveness of liquid-cooled battery thermal management systems (BTMS) in electric vehicles, a unique liquid-cooled plate with a discrete, inclined, and alternating arrangement of ribs and grooves inside the plate was invented during this study. A numerical study was carried on to analyze the thermal performance between this rib-grooved liquid-cooled plate and a conventional straight-channel one. Firstly, a battery module's 1D/3D electrochemical-thermal coupled model was constructed to analyze the thermal performance in the case of actual electrochemical heat production. Then numerical results were obtained by solving this coupled model with different plates. The results indicated that ribs effectively equalize the flows between different channels and multiple longitudinal swirl flows are formed due to grooves, which improves the liquid-cooled system's temperature control performance with a small increase in pressure drop. The maximum battery temperature is 0.74 °C lower, the temperature standard deviation of the contact surface is 0.18 °C lower, and the pressure drop is 55.37 Pa higher in the BTMS with the rib-grooved liquid-cooled plate than it is in the conventional one. After that, an orthogonal design of experiments was used to investigate the effect of four features, including rib-groove tilt angle, column spacing, row spacing, and rib-groove length, on the thermal performance and energy consumption of the battery module. The optimum structure of the rib-grooved liquid-cooled plate is obtained through range analysis: the rib-groove inclination angle is 45°, the row spacing is 13.5 mm, the column spacing is 11.5 mm, and the rib-groove length is 9 mm. This research on the rib-grooved liquid-cooled plate offers a fresh concept that considerably enhances its capacity to regulate the temperature of the liquid-cooled BTMS.

Heat dissipation performance research of battery modules based on composite phase change materials cooling and electrochemical thermal coupling model

In order to improve electric vehicle lithium-ion batteries (LIBs) performance and increase cycle life, it is crucial to design a reliable and efficient battery thermal management system (BTMS). Compared with other active battery cooling methods, passive phase change material (PCM) cooling has the advantages of simple structure, good temperature control uniformity, strong reliability, and no additional energy consumption. This article uses a series of experimental procedures to add expanded graphite to traditional paraffin wax PCM and obtain composite phase change materials (CPCM) with different mixing ratios. A control experiment is created to compare the cooling performance of the CPCM cooling with natural convection cooling, research shows that the cooling performance of CPCM can well meet the cooling demand which maximum temperature and maximum temperature difference of battery modules. In addition, to study the performance of thermal properties parameters related to CPCM, a COMSOL numerical calculation model of battery module based on CPCM cooling and electrochemical thermal coupling model is established. The effectiveness and accuracy of the model are verified through heat generation experiments at different rates (0.5 C, 1 C, 1.5 C), with a maximum temperature error of 1.6 K and an error accuracy of less than 0.6%. Subsequently, the performance of phase change temperature, thermal conductivity and phase change latent heat is studied and reasonable value ranges are obtained, which are 312 K∼318 K, 2.5 W /(m·K), and 175 J/g∼200 J/g, respectively.

A novel order-reduced thermal-coupling electrochemical model for lithium-ion batteries

Although the single-particle model enhanced with electrolyte dynamics (SPMe) is simplified from the pseudo-two-dimensional (P2D) electrochemical model for lithium-ion batteries, it is difficult to solve the partial differential equations of solid–liquid phases in real-time applications. Moreover, working temperatures have a heavy impact on the battery behavior. Hence, a thermal-coupling SPMe is constructed. Herein, a lumped thermal model is established to estimate battery temperatures. The order of the SPMe model is reduced by using both transfer functions and truncation techniques and merged with Arrhenius equations for thermal effects. The polarization voltage drop is then modified through the use of test data because its original model is unreliable theoretically. Finally, the coupling-model parameters are extracted using genetic algorithms. Experimental results demonstrate that the proposed model produces average errors of about 42 mV under 15 constant current conditions and 15 mV under nine dynamic conditions, respectively. This new electrochemical-thermal coupling model is reliable and expected to be used for onboard applications.

A comparative investigation of two-phase immersion thermal management system for lithium-ion battery pack

The applications of lithium-ion batteries (LIBs) still suffer from thermal sensitivity and safety issues, especially given the rigorous requirements of fast charging and discharging. When choosing a proper battery thermal management system (BTMS), a comprehensive investigation should be made in terms of design complexity, system cost, and cooling efficiency, which usually forms a trade-off. In this study, four types of BTMS including air cooling, single phase immersion, indirect cooling, and two phase immersion are first evaluated on pouch battery pack. To describe the uniform heat generation, batteries are simulated by a three-dimensional electrochemical-thermal coupled model. Results show that air cooling and immersion cooling exhibits less extra weight, while two phase immersion delivers better in suppressing temperature rise and maintaining temperature uniformity. Then, the simulations involving different coolants are conducted for two phase immersion-based BTMS. The thermal behaviors of battery pack are examined at 5, 7, and 9 C discharge rates. The R1336mzz(Z) coolant with high boiling heat transfer coefficient is suitable for thermal management at high discharge rates. Besides, analysis reveals that increasing the immersion level of battery pack can improve battery temperature behaviors. This work is expected to provide preliminary proof of BTMS design for fast discharging.

Numerical Study on Heat Generation Characteristics of Charge and Discharge Cycle of the Lithium-Ion Battery

Lithium-ion batteries are the backbone of novel energy vehicles and ultimately contribute to a more sustainable and environmentally friendly transportation system. Taking a 5 Ah ternary lithium-ion battery as an example, a two-dimensional axisymmetric electrochemical–thermal coupling model is developed via COMSOL Multiphysics 6.0 in this study and then is validated with the experimental data. The proportion of different types of heat generation in a 26,650 ternary lithium-ion battery during the charge/discharge cycle is investigated numerically. Moreover, the impact of essential factors such as charge/discharge multiplier and ambient temperature on the reaction heat, ohmic heat, and polarization heat are analyzed separately. The numerical results indicate that the total heat generated by the constant discharge process is the highest in the charging and discharging cycle of a single battery. The maximum heat production per unit volume is 67,446.99 W/m3 at 2 C multiplier discharge. Furthermore, the polarization heat presents the highest percentage in the charge/discharge cycle, reaching up to 58.18% at 0 C and 1 C multiplier discharge. In a high-rate discharge, the proportion of the reaction heat decreases from 34.31% to 12.39% as the discharge rate increases from 0.5 C to 2 C. As the discharge rate rises and the ambient temperature falls, the maximum temperature increase of the single-cell battery also rises, with a more pronounced impact compared to increasing the discharge rate.

Investigation of novel pulse preheating strategies for lithium-ion batteries at subzero temperature based on a multi-level CFD platform

Warming up lithium-ion batteries from cold environments to room temperature rapidly and safely is the key to popularizing battery electric vehicles in cold regions. Pulse preheating technology is an effective internal heating method while facing challenges such as low heating rate, high energy consumption, and risk of over-charging or discharging. Here, for the first time, a multi-level electrochemical-thermal coupling model is developed on an open-source CFD platform. Based on this model, we perform comprehensive simulations for the pulse heating process with various parameters and strategies from plate level to cell level to module level. In addition, two innovative heating strategies, namely varied rate pulse and hybrid pulse, are proposed, where the latter integrates the pulse heating and electric heating. Our main results show that the proposed hybrid pulse strategy can provide cells with an over 2.5 times faster heating rate from −20 °C to 0 °C and save nearly 60 % energy consumption compared to the single pulse heating at 6 C-rate, exhibiting a great prospect in circumventing the low-temperature effect. Besides, the internal temperature difference can be controlled. A high pulse frequency is suggested to achieve better temperature consistency within cells and avoid noticeable changes in the cell internal physical fields.

Research on the Improvement of Lithium-Ion Battery Performance at Low Temperatures Based on Electromagnetic Induction Heating Technology

As the major power source for electric vehicles (EVs), lithium-ion batteries (LiBs) suffer from the degradation of technical performance and safety at low temperatures, which restricts the popularization of EVs in frigid regions. Thus, this study developed an extremely fast electromagnetic induction heating system in order to improve the poor performance of LiBs in cold weather. An electrochemical–thermal coupling model (ETCM), validated against the experimental results of charge and discharge, which successfully predicted LiB voltage, temperature, and other physical characteristics at various ambient temperatures, was established in COMSOL Multiphysics 6.0 as a development tool for evaluating the heating effect of the system. When the copper coil is subjected to a SAC (sinusoidal alternating current) of 8 A and 50 Hz, the LiB can be heated from 243.15 to 293.15 K within 6 min with an instantaneous temperature increase rate of 0.263 K/s and a homogeneous temperature distribution. The results of the capacity calibration, cyclable lithium detection, and HPPC simulation show that the heating method can visibly increase the Li+ concentration inside the active particle, and there was only a tiny concentration gradient on the surface of the particle. In addition, the internal resistance was approximately a quarter of that without heating; therefore, both the discharge energy and specific power boost were two times higher than the original level. Compared to the normal charge–discharge cycles at 293.15 K, the capacity retention of the LiB only decreased by 0.23% after 60 consecutive heating cycles, so the heating method can balance the temperature rise, work capacity, and LiB health. Furthermore, the improvements in the thermal insulation condition and material thermal conductivity are two feasible ways to optimize the temperature-increase effect.

Experimental and Simulation Studies on the Thermal Characteristics of Large‐Capacity Square Lithium‐Ion Batteries with Low‐Temperature Discharge

As the capacity of lithium‐ion batteries decays severely at low temperatures, it is important to study the electrochemical and thermal properties of lithium‐ion batteries at low temperatures. Herein, a large‐capacity prismatic lithium‐ion battery is selected to carry out experiments to study the electrothermal characteristics of the battery in different temperatures (25, 0, −10, and −20 °C). Second, a pseudo‐3D electrochemical–thermal coupling model is established and the validity of the model is verified. Finally, this article analyzes the influence of ambient temperature on the thermal characteristics of the battery during discharge. The results show that the battery discharge capacity gradually decreases with the decrease in the ambient temperature. At −20 °C, the discharged electricity is 66.51% of that at room temperature. At the same time, as the ambient temperature drops, the temperature rise on the surface of the battery increases during the discharge process, and at −20 °C, the temperature rise can reach 3.86 times than that at normal temperature. In addition, the change in reversible heat percentage is negatively correlated with the discharge rate and positively correlated with the battery temperature, while the effect of the discharge rate on irreversible heat is greater than that of ambient temperature.

Thermal and stoichiometry inhomogeneity investigation of large-format lithium-ion batteries via a three-dimensional electrochemical-thermal coupling model

Large-format lithium-ion batteries (LIBs) have attracted extensive concern due to the advantages of increasing energy density and reducing manufacturing costs. However, inhomogeneity is widely present in large-format LIBs, which may lead to local degradation or edge lithium plating, thereby reducing the battery durability and safety. In this study, an electrochemical-thermal (ECT) coupling model for large-format LIBs is developed to quantitatively investigate the battery inhomogeneity during charging and discharging. First, two different sizes of batteries with the same electrode material are disassembled and tested to obtain the battery model parameters. Second, a novel method for determining the parameters of the ECT coupling model for large-format LIBs is proposed to solve the technical challenge of difficult model parameter calibration. Specifically, the ECT coupling model parameters of large-format batteries are determined using those of small-format batteries. The experimental results show that the three-dimensional ECT coupling model exhibits high accuracy, with the root mean square error of voltage and temperature within 17.8 mV and 1.27 ˚C, respectively, at 1C discharge rate and SOC greater than 2.5 %. Finally, the temperature and stoichiometry coefficient inhomogeneity of large-format LIBs during charging and discharging under different conditions are analyzed quantitatively. The results show that the inhomogeneity of large-format LIBs increases significantly with increasing discharge rate and battery length. A large-format battery with a length of 900 mm achieves a balance between inhomogeneity and length. This study contributes to a quantitative understanding of the inhomogeneity of large-format LIBs and provides a model-based perspective for designing and optimizing large-format LIBs.

Photothermal-Conversion-Enhanced LiMn2O4 Pouch Cell Performance for Low-Temperature Resistance: A Theoretical Study

Lithium-ion batteries (LIBs) suffer from charging difficulties, capacity decay, and severe ageing in a low-temperature environment. In this work, we suggest a theoretical study and strategy for improving the low-temperature resistance of LiMn2O4(LMO) pouch cells, by introducing a photothermal conversion layer composed of copper and single-walled carbon nanotubes. A three-dimensional electrochemical–thermal coupling model for a lithium manganate battery is established, in which the photothermal conversion layer is attached on the surface of the cathode collector, and the effect of lug design is also discussed. The changes in the battery temperature field, and improvements in electrochemical performance before and after light preheating, are analyzed. The results show that, when the photothermal conversion film is applied, the LMO pouch cell’s temperature rises 2.7 °C/min in a −5 °C environment, and the surface-temperature averaging is improved. The concentration of lithium embedded in the anode is significantly increased, and the charging speed is enhanced by 20%. The batteries with a single-sided lug design exhibit better performance compared with those with a two-sided lug design. Validation of the presented model is performed, by comparing it with the experimental Panasonic UF653445ST commercial battery datasheet. This work provides theoretical guidance on improving the low-temperature performance of pouch cells, based on the photothermal conversion method.

Non-uniform thermal characteristics investigation of three-dimensional electrochemical-thermal coupled model for pouch lithium-ion battery

Recently, lithium-ion batteries have been preferred as an approach for energy infrastructures. However, its uneven performance directly affects battery modeling, parameter estimation and thermal management. To understand the non-uniform thermal characteristics of pouch battery, a three-dimensional multiphysics model that combines an electrochemical model and a thermal model is developed in this study. Here, three models with lumped and non-uniform heat source as well as temperature are comprehensively compared and evaluated under different discharge rates. Results indicate that the dimensionality and lumped-source of model have negligible effects on predicting heat generation and maximum temperature, but the temperature gradient distribution shows deviation of 64.0/62.1% at 5 C discharge. Due to the uneven heat generation, an overheating region appears along the battery center to positive tab, especially at high discharge rates. What's more, it is found that more heat is generated at a high discharge rate and low-temperature, which leads to higher temperature rise and temperature gradient. In addition, the critical heat transfer coefficient that represents the critical heat dissipation capacity of thermal management system is estimated. These findings can provide insights into the selection of battery models and the design of thermal management systems in accordance with different scenarios.