Battery Heat Generation Research Articles

Cover Picture: New Insights into Self‐Discharge and Heat Generation in Magnesium Batteries (Batteries & Supercaps 7/2023)

The Front Cover shows the total heat generation of magnesium batteries containing the Mo6S8 (CP) and organic 14PAQ for different electrolyte solvents using sophisticated calorimetry and the dissolution of interphases. The heat generated during the battery operation is important for the battery thermal management system (BTMS) where battery packs or cells during operation are at different states of charge and generate heat accordingly. More information can be found in the Research Article by I. Ul Mohsin and co-workers.

New Insights into Self‐Discharge and Heat Generation in Magnesium Batteries

AbstractInvited for this month's cover is the group of Dr. Ijaz Ul Mohsin. For the first time, the total heat generation and self‐discharging phenomena of magnesium batteries containing the Chevrel Phase Mo6S8 and organic 14PAQ are compared for different electrolyte solvents using sophisticated calorimetry. Noticeable differences are observed and in tetraglyme solvent stable cycling and fewer self‐discharge phenomena are detected. However, the activation process needs more cycles to achieve the required capacity in the case of the Chevrel Phase. Read the full text of the Research Article at 10.1002/batt.202300137.

Online prediction for heat generation rate and temperature of lithium-ion battery using multi-step-ahead extended Kalman filtering

It is well known that the performance, reliability, and safety of lithium-ion batteries (LIBs) are strongly influenced by temperature. Owing to the hysteresis of temperature regulation, multi-step-ahead online temperature prediction is needed for model prediction control of battery thermal behaviors, and for improving the safety and service life of battery. According to the energy conservation equation, temperature is determined on the account of heat dissipation and generation. In that, when facts pertaining to heat dissipation are understood and known to a certain extent, battery heat generation ought to be the key to battery temperature prediction. Nonetheless, measurement of heat generation rate based on calorimetry is unfit for online applications, and calculation of heat generation rate based on the Bernardi equation also has limitations, such as error escalation with large-size LIBs or sensitivity to the battery’s entropy coefficient. To circumvent these issues, this paper considers a prediction method for battery heat generation rate and temperature based on the multi-step-ahead extended Kalman filter, which is profoundly useful for nonlinear state estimation. The filtering process takes two iterative steps, in that, the Bernardi equation is used as the state equation, and the battery energy conservation equation is taken as the observation equation. The proposed method is able to reduce the mean absolute error (MAE) of heat generation rate prediction by about 40% as compared to the benchmark that uses Bernardi equation alone, and the MAE of temperature is less than 0.1 K under the Urban Driving Cycle working condition, over different prediction horizons. Moreover, when the entropy coefficient fluctuates within the range of 0.7 to 1.3 times of the original value, the MAE variation of heat generation rate is less than 0.04 W while that of the aforementioned benchmark is 0.13 W. In short, the proposed method can improve both the accuracy and robustness of prediction of heat generation rate, while satisfying online applications.

Research on Heat Generation Measurement for Lithium-Ion Battery Using Isothermal Calorimeter

Isothermal calorimeter is one of the most applicable instruments to measure the heat generation of batteries. In most commercial isothermal calorimeters, battery temperature or its surface temperature is usually controlled. However, such control leads to the calibration factor of isothermal calorimeter varying with batteries and installation methods. This study proposes an improved thermal model to analyze the theory of battery isothermal calorimeter with power compensation method. The innovative finding reveals that when the adapters temperature is controlled, the calibration factor of isothermal calorimeter approaches one and is independent of heat transfer resistances. In contrast, when the battery temperature is controlled, the calibration factor is less than one and is directly related to the heat transfer resistances. As heat transfer resistances in the calibration process differ from those in the actual battery measurement process, more accurate results can be achieved if the adapters temperature is controlled. This study also presents the measurement results of a commercial LiNi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/3</sub> Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/3</sub> Mn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /Graphite battery under the two different conditions of temperature control. Based on the differential equation when the adapters temperature is controlled, the real heat flux of the battery is calculated, and the dynamic response characteristic of heat flux is greatly improved.

New Insights into Self‐Discharge and Heat Generation in Magnesium Batteries

AbstractMo6S8 in the Chevrel Phase (CP) and 14‐polyanthraquinone (14PAQ) cathode materials‐based coin cells were assembled against Mg‐foil as an anode by using 0.3 M magnesium tetrakis (hexafluoroisopropyloxy) borate Mg[B(hfip)4]2/dimethoxyethane (DME), 0.5 M Mg[B(hfip)4]2/DME and 0.5 M Mg[B(hfip)4]2/tetraglyme (G4) electrolytes. The heat generation of those three variants was compared using a sensitive MS80 Tian‐Calvet calorimeter. The Chevrel Phase Mo6S8 was found to generate less heat than the organic 14PAQ. However, its specific capacity was also comparatively lower than for the organic cathode material. It is equally important for battery kinetics to have a well‐designed electrolyte, therefore different solvents with the same electrolyte salt were utilized. Noticeable differences were observed and in tetraglyme solvent stable cycling and fewer self‐discharge phenomena were detected. However, the activation process needs more cycles to achieve the required capacity in the case of the Chevrel Phase. The generated heat during cycling indicated the high resistances, swelling/contraction in organic cathodes leading to higher heat generation, and poor capacity retention. To overcome self‐discharging in Mg batteries, side reactions/dissolution of cathode materials, electrolyte saturation and the formed interfaces on the anode side must be considered.

Non-invasive accurate time resolved inverse battery calorimetry

Precise knowledge of the battery heat generation rate and the internal temperature rise allows accurate thermal regulation required for enabling fast charging while minimizing side reactions and avoiding thermal runaway. With the necessity of high energy density, the size of batteries is constantly increasing. Because of poor thermal conduction, the thermal lag in large batteries is significant resulting in a considerable temperature gradient within the cell. Existing calorimetry methods only account for the external heat flow measurement and the external temperature rise and therefore cannot account for the thermal lag inside the cell. Additionally, with these methods, the temporal (time-resolved) information of the heat generation rate is compromised, which makes observation and attribution of electrochemical- thermal signatures impossible. As a potential solution, various intrusive techniques such as embedded thermal sensors have been proposed in the literature. However, these techniques are limited in scope. To enable accurate measurement of time-resolved heat flux measurement in commercial batteries, we instead propose a new battery calorimetry approach by combining state-of-the-art commercial calorimetry with an inverse heat transfer algorithm. This inverse calorimetry is completely non-intrusive with no change to commercial calorimeters. The inverse calorimetry reduces the error in heat generation rate to within 10% of the actual heat generation rate compared to 50% from the lumped capacitance method (best existing method). This method enables time resolved observation of electrochemical-thermal signatures such as a negative heat generation rate due to entropy change, which could not be observed from existing calorimetry methods.

Algorithm-driven optimization of lithium-ion battery thermal modeling

Detailed modeling of battery thermal behaviour has high computational demand due to the presence of multi-scale and multi-physics phenomena. For battery module/pack level simulation, a simple and accurate battery heat generation estimation is urgently required. This paper investigates the optimization of thermal numerical modeling for cylindrical 21,700 lithium-ion batteries with a nominal capacity of 5 Ah. A 3-dimensional battery model was built in the Multiphysics simulation software, COMSOL. The heat source of the model adopts a commonly used heat generation model incorporating irreversible and reversible heat. Correction factors, as a function of the state of charge, were introduced to the calculation of irreversible heat item. The Particle Swarm Optimization (PSO) algorithm, written in MATLAB, was coupled with the COMSOL numerical model to minimize the prediction error by varying correction factors. Battery surface temperature data under the continuous discharge tests (0.5C–3.5C) and dynamic loads were experimentally obtained and used to validate the model. The simulation results of the unoptimized model showed a discrepancy of up to 5 °C with the experimental data. After optimization, the prediction error was reduced to less than 0.5 °C on average. The optimized model was applied to predict the thermal behaviour of a battery module (16 aged cells) using oil-based immersion cooling. The pristine battery module with coolant flow velocities of 0.01 m/s was chosen as the baseline. The results indicate that the aged battery modules with internal resistance of 50 mΩ and 75 mΩ require coolant flow velocities of 0.05 m/s and 0.12 m/s, respectively, to achieve the baseline temperature. The study highlights a high-precision and low-computational cost approach for heat generation calculation of lithium-ion batteries is provided, which contributes to the development of battery thermal management systems.

Experimental and numerical studies on lithium-ion battery heat generation behaviors

Current predictions of battery HGR (heat generation rate) mainly rely on Bernardi’s empirical equations, which suffer from limitations of adaptability for thermal use. A novel scheme based on experiments and BPNN (BP (back propagation) neural network is a multilayer feedforward neural network trained according to the error back propagation algorithm) is proposed in this paper. In the experiments, the thermal generation behavior of 18650 batteries under 108 different operating conditions was investigated, and the Ta (ambient temperature) as well as ID (discharge current) were extracted as inputs to the BPNN model. The experimental results show that the heat generation performance of the battery is strongly influenced by Ta and ID. The higher Ta and ID, the more obvious this effect is. The maximum error of the battery HGR obtained by using Bernardi’s empirical equations can reach 45.2 %. The predicted battery HGR using BPNN has good accuracy with error control within 5%. Accordingly, this paper provides the technical basis for proposing a promising thermal management solution.

An integrated thermal management strategy for cabin and battery heating in range-extended electric vehicles under low-temperature conditions

The integrated thermal management strategy under low-temperature conditions can effectively alleviate mileage anxiety associated with electric vehicles and improve the thermal comfort of the cabin. In this study, an integrated thermal management topology for range-extended electric vehicles is proposed, which recovers the waste heat from the range extender and the electric drive system for the heating of the battery and the cabin to improve energy utilization. Considering the driving modes and heating demands, the working modes and switching rules are designed. Especially, a control-oriented coupling system model is established for pure-electric mode. Taking cabin heat load demand, battery heat generation, and electric drive system heat generation as disturbances, a model predictive controller is designed for the heating power of the heater. An integrated thermal management system model verified by experiments is established in AMEsim. The initial temperature of the environment and vehicle is −20 °C, and the target temperatures of the cabin and the battery are set at 20 °C and 25 °C respectively. The feasibility of the strategy is verified by the co-simulation of Simulink and AMEsim under 4 WLTC cycles. The results show that in the range-extended mode, the integrated system shortens the battery heating time and reduces fuel consumption by more than 10.2 % compared with the independent system. In pure-electric mode, the heating speed of the proposed model predictive control strategy is slightly faster than that of the on–off strategy, the heating energy consumption is reduced by 20.95 %, and the total energy consumption for propulsion and thermal management decreased by 2.84 %.

Measurement of thermophysical parameters and thermal modeling of 21,700 cylindrical battery

There is temperature unevenness inside the operating battery, and the internal temperature distribution of the battery has gradually attracted attention. To establish a thermal model of the 21,700 cylindrical battery that can reflect the internal temperature distribution, thermophysical parameters including anisotropic thermal conductivity and specific heat capacity are tested through experiments. The thermal model includes the heat generation part and heat transfer part. Thermophysical parameters are essential for the heat transfer part. Hybrid pulse power characterization (HPPC) tests are carried out to obtain battery internal resistance, and the entropy coefficient of the battery is also obtained by tests. Internal resistance and entropy coefficient data are used as inputs for the battery heat generation part. The core temperature and surface temperature of the operating battery are measured by the thermocouple embedded inside the battery and the thermocouple pasted on the battery surface. The calculated core and surface temperatures from the battery thermal model are both in good agreement with the measured temperature results. The maximum core temperature of 2C discharging battery is about 60 °C and the maximum temperature difference inside the 21,700 battery reaches 3 °C. The established simulation model can be used for extended research work. When heat dissipation is enhanced by increasing the convection heat transfer coefficient, the overall temperature of the battery decreases but the temperature non-uniformity inside the battery is aggravated.

Analysis and Research of Compound Refrigeration based on Logic Control Battery

In order to ensure the safety and stability of the power battery, the design of refrigeration system is very important. Firstly, a battery model based on logic control and lumped heat parameters was established to determine the real-time and accurate state of battery heat generation, heat transfer, radiation heat dissipation and battery temperature. The feasibility of the simulation model is verified by the experimental results. Secondly, the refrigeration system of battery air cooling and liquid cooling is established, and a new composite cooling system is proposed and built. By changing the wind speed and flow rate, the variation of the cooling effect of air cooling and liquid cooling with the medium flow rate was analyzed. The results show that, in a certain range, the larger the flow rate, the more obvious the cooling effect of the cooling method, and the flow rate is positively correlated with the cooling effect. In order to compare the cooling effect of the new composite cooling system, the temperature rise curves, temperature difference curves and energy consumption of different cooling methods were analyzed under the discharge rates of 4C and 8C.he results show that when the system tends to be stable, the total energy consumption of liquid cooling and mixed cooling is almost the same, and the energy consumption of air cooling is the largest. According to the analysis of the maximum equilibrium temperature difference inside the battery unit when the temperature is stable, the temperature difference of the composite cooling method is the smallest, about 1℃. Moreover, by analyzing the fluctuation range of battery pack temperature when it is stable, the fluctuation of composite refrigeration is the smallest, only 2℃. In conclusion, the hybrid refrigeration system based on logic control has good cooling performance.

Phase-change cooling of lithium-ion battery using parallel mini-channels cold plate with varying flow rate

In this study, a liquid phase-change cooling module with mini-channels cold plate was designed. The temperature properties of a battery monomer with different cooling conditions and varying discharge rates were investigated. The heat dissipation contribution of latent heat transfer to the overall cooling performance of the mini-channels cold plate was analyzed based on the outlet vapor quality. Particularly, a cooling strategy with varying coolant flow rates was proposed and examined at 3C discharge rate. The results illustrated that the designed battery cooling module had an ideal effect on lowering the battery's surface temperature and increasing the battery's temperature uniformity. Compared to the cooling strategy with constant coolant flow rate, the proposed variable flow cooling strategy better matched the dynamic law of battery heat generation and increased the contribution of the latent heat transfer to the battery cooling, thereby efficiently reducing the coolant consumption and the pump power consumption of the BTMS (battery thermal management system) while providing the same or even superior cooling performance. The findings could assist the optimization of the BTMS and be the reference for the application of the varying flow rate cooling strategy in actual engineering.

Evaluating the heat generation characteristics of cylindrical lithium-ion battery considering the discharge rates and N/P ratio

Although lithium-ion batteries (LIBs) have received more attentions as the increasing number of new energy vehicles, in-depth exploration for the heat generation characteristics of LIBs during operation remains challenging. This paper establishes an electrochemical-thermal model (ETM) to evaluate the heat generation characteristics of cylindrical LIBs considering the discharge rates and the ratio of negative to positive electrode capacity (N/P ratio). To ensure a wider range of research on thermal characteristics of LIBs, the proposed ETM is validated based on the experimental data under the ambient temperature of 25 °C and 35 °C. Subsequently, the distribution profiles of heat generation characteristics of LIBs under different conditions are numerically investigated. More innovatively, the effects of different discharge rates and N/P ratios on battery heat generation are comprehensively analyzed. The results show that the heat generation in the negative electrode occupies a major part and the influences of reversible term on the total heat generation of LIB cell cannot be ignored, especially at low discharge rates. Additionally, it is found that the proper selection of N/P ratio can improve the total heat generation of LIBs, which is helpful for optimizing performance in the early stages of battery design and thermal management.

Simulation Study on Heat Generation Characteristics of Lithium-Ion Battery Aging Process

Lithium-ion battery heat generation characteristics during aging are crucial for the creation of thermal management solutions. The heat generation characteristics of 21700 (NCA) cylindrical lithium-ion batteries during aging were investigated using the mathematical model that was created in this study to couple electrochemical mechanisms, heat transfer, and aging loss. These findings indicate that, at the same operating current, the heat generation power of the cell increased significantly with battery aging. This increase was primarily due to the energy loss caused by the growth of the solid–electrolyte interface (SEI) and a reduction in the negative porosity and other physical characteristics of the SEI, such as its ionic conductivity and molar volume, which also had an impact on the heat generation power. By investigating the variations in battery heat generation in different aging modes, the electrochemical mechanisms underlying the effects of aging on battery heat generation can be comprehended in depth.

Development of a coupled model of heat generation and jet flow of lithium-ion batteries during thermal runaway

A large amount of heat will be generated during battery thermal runaway. However, the current models for the battery thermal runaway mainly consider the heat generated inside the battery cell and rarely consider the effects of the jet fire. Therefore, it cannot provide an effective way to evaluate the thermal runaway propagation in a battery pack. This study develops a coupled model considering the heat generation inside the battery and the jet fire outside the battery during thermal runaway, which can better evaluate the thermal hazard. Experimental and simulation activities are carried out based on 18,650 cylindrical NCM lithium-ion batteries. First, a test bench is built to trigger and record the thermal runaway. High-speed camera and thermocouples are applied to record the fire shape and temperature. Totally 15 cells with 100 % SOC are abused and six samples experienced intense combustion. The jet fires last for at least 20 s and the maximum combustion temperature was 1075.4 °C, at the location 80 mm above the cell. Then a coupled model consisting of 0D heat generation, gas generation and injection sub-models and 2D CFD sub-model is established based on ANSYS Fluent. The heat and gas generation rates inside the battery are calculated based on chemical reaction mechanisms. The flow, combustion and heat transfer in the open space are solved in a 2D axisymmetric domain. The proposed model can reasonably capture the main characteristic of the jet fire and temperature rise during thermal runaway. The maximum deviation of peak temperature between the experiment and simulation is 8.56 %.

Passive battery thermal management system for an unmanned aerial vehicle using a tetrahedral lattice porous plate

Lithium-ion batteries (LIB) are the main energy source for unmanned aircraft vehicles (UAVs) and drones. A drone operates at various ambient temperatures, depending on its flight characteristics. For optimal performance, this requires the application of a passive battery thermal management system (BTMS) that does not require additional equipment due to drone weight limitations. This study proposes applying a multifunctional tetrahedral lattice porous plate (TLPP) to analyze the performance of a passive BTMS using aspirated airflow through a drone flight mode. A battery cell constant-current discharge experiment is conducted to derive the equivalent internal resistance of the battery cells for the numerical simulation of battery heat generation. The performance of a passive BTMS with a TLPP channel, including part of the freestream through a series of drone modes, is analyzed using experiments and numerical simulations at the battery cell and module levels. The main conclusion of this study was that in a numerical simulation of takeoff and landing in drone operation mode, the maximum temperature, and deviation reduction rates were 22 % and 4 9%, respectively. Additionally, the maximum temperature and deviation from the TLPP application under conditions in which some freestreams were aspirated during the drone's forward flight were reduced by 35 % and 76 %, respectively. It is confirmed that the maximum temperature and deviation on the battery surface are significantly reduced due to the application of TLPP on a bare battery. Therefore, passive BTMS with TLPP can provide effective multifunctionality for the thermal management of drone batteries.

Investigation on Battery Thermal Management Based on Enhanced Heat Transfer Disturbance Structure within Mini-Channel Liquid Cooling Plate

The battery thermal management system plays an important role in the safe operation of a lithium-ion battery system. In this paper, a novel liquid cooling plate with mini-channels is proposed and is improved with disturbance structures. First, an accurate battery heat generation model is established and verified by experiments. The error is less than 4%, indicating the heat generation power is reliable. Then, five designs are proposed first to determine the suitable number of disturbance structures, and plan 3 with five disturbance structures shows a satisfying performance in heat dissipation and flow field. Moreover, four layout plans are proposed, namely uniform, interlaced, thinning, and gradually denser distribution. Results show that plan 5 (uniform) achieves the best performance: the maximum average temperature is 36.33 °C and the maximum average temperature difference is 0.16 °C. At last, the orthogonal experiment and range analysis are adopted to optimize the structure parameters. Results show that the best combination is space between adjacent disturbance structures d1 = 20 mm, length d2 = 5 mm, width d3 = 1.5 mm, and tilt angle β = 60°.

Effect of Heat Pipe’s Configuration in Managing the Temperature of EV Battery

Because of their high energy density and long cycle life, lithium-ion batteries are commonly employed in electric cars. As battery performance and life are highly dependent on temperature, it is critical to maintain the optimum temperature range. A battery thermal management system (BTMS) is critical for controlling the thermal behaviour of the battery. Air cooling, liquid cooling, direct refrigerant cooling, phase change material (PCM) cooling, and heat pipe cooling are all BTMS strategies. Heat pipes come in a variety of sizes and configurations that can be employed in the BTMS and many studies have proven the feasibility of using heat pipe as the electric vehicles’ BTMS. However, there are many aspects of the design and configuration of the heat pipe that could affect the overall thermal performance of the heat pipe BTMS such as its length, diameter, evaporator and condenser lengths, tilt angle, types of heat pipes and working fluids. In this work, a numerical study was conducted to investigate the effect of heat pipe’s diameter, number of heat pipes and the types of heat pipes on the thermal performance of the heat pipe BTMS. The diameter of the heat pipe varies between 6 – 12 mm, the number of heat pipes varies from 2 – 10 and the type of heat pipe considered in this work is straight heat pipe. The thermal performance of the heat pipe is measured by the maximum battery temperature and the thermal resistance at different battery heat generation rate in the range of 10 - 30W. The simulation model was validated against experimental data and results indicate excellent agreement between simulation and experimental data. Simulation results shows that the greater the diameter, the lower is the battery temperature. By increasing the heat pipe’s diameter, the battery temperature can be reduced by at least 10% or 3.4°C. Temperature reduction of at least 12.7% was observed when the number of heat pipes used in the BTMS increases.

Analysis of Capacity Decay, Impedance, and Heat Generation of Lithium-ion Batteries Experiencing Multiple Simultaneous Abuse Conditions

Analysis of Capacity Decay, Impedance, and Heat Generation of Lithium-ion Batteries Experiencing Multiple Simultaneous Abuse Conditions

Experimental and Numerical Studies on the Effect of Lithium-Ion Batteries’ Shape and Chemistry on Heat Generation

Data sets of internal resistances and open-circuit voltage of a particular battery are needed in ANSYS Fluent program to predict the heat generation accurately. However, one set of available data, called Chen’s original, does not cover all types and shapes of batteries. Therefore, this research was intended to study the effects of shapes and polarization chemistries on heat generation in Li-ion batteries. Two kinds of material chemistries (nickel manganese cobalt oxide, NMC, and lithium iron phosphate, LFP) and three forms (cylindrical, pouch, and prismatic) were studied and validated with the experiment. Internal resistance was unique to each cell battery. Differences in shapes affected the magnitude of internal resistance, affecting the amount of heat generation. Pouch and prismatic cells had lower internal resistance than cylindrical cells. This may be the result of the forming pattern, in which the anode, cathode, and separator are rolled up, making electrons difficult to move. In contrast, the pouch and prismatic cells are formed as sandwich layers, resulting in electrons moving easily and lowering the internal resistance. The shapes and chemistries did not impact the entropy change. All batteries displayed exothermic behavior during a lower SOC that gradually became endothermic behavior at around 0.4 SOC onwards.