Battery Thermal Performance Research Articles

Battery thermal performance oriented all-electric ship microgrid modeling, operation and energy management scheduling

Energy storage system (ESS) integrated all-electric ship (AES) is gaining popularity as it renders higher efficiency and emission reduction. Being an isolated system, generation and storage capabilities are limited, and hence network losses, mechanical and electrical load estimation must be modeled accurately to establish a reliable operation strategy. Thus, the presented work proposes a modeling and operation strategy based on the propulsion architecture, mission profile, operation modes, and thermal performance of ESS. The following aspects are incorporated to improve the accuracy. (1) Electrical load demand, and loss modeling at the generation and load side; (2) energy management system (EMS) for optimal energy dispatch; (3) and experiment-based ESS electrical characterization and cooling designs for the thermal management system. Firstly, mathematical models of electrical components and mechanical propulsion units are used to establish the net electrical load demand from the propulsion and auxiliary units. The parameters obtained from load models are used in EMS energy dispatch to minimize the fuel and thermal-performance-dependent ESS operation costs. Finally, generation side losses are included in the final dispatch to meet the net electrical load demand of the vessel. Based on electrical parameters from test setup and different cooling designs, a battery management system is modeled to estimate the ESS pouch’s temperature profile that is used as an operational constraint of EMS to discourage ESS from operating at high temperatures. Simulation results indicate the impact of AES propulsion architecture and ESS thermal performance on its operation. The results suggest the strong influences of mission profile and operation modes in designing a realistic operation schedule for the actual implementation.

Optimization of the Cooling System of Electric Vehicle Batteries

The most important components of electrical vehicles are the battery and the related cooling system. These subsystems play a major role in determining the overall electric vehicle performances. In this study, a novel cooling system with fluid in the battery cell is proposed, by which the energy storage system can be optimized through control of the temperature of the batteries. A sensitivity analysis is conducted considering the maximum temperature, the heat rate, the coolant temperature, and the geometry of the cavities. The numerical simulations show that the parameters for the trapezoidal compartment have an impact on the thermal performance of battery. An optimal geometry is proposed accordingly. It is concluded that for high values of Reynolds number for which the flow becomes turbulent, a decrease in the battery temperature can be obtained thereby avoiding thermal stresses.

Investigation of performance parameters of building thermal battery

The concept of a building thermal battery refers to storing the supplied heat and releasing it the another time through radiation and convection. The introduction of building thermal battery performance has created a more convenient solution to the problems of building load estimation, control and optimization, building-grid integration, etc. Some literatures have expanded the original definition of building thermal batteries, including PV RE (photovoltaic renewable energy), HVAC and other units. Starting from the building body, this investigation studies a building energy system. With reference to the performance parameters of traditional rechargeable batteries, the corresponding performance parameters of building thermal batteries are developed. The RC model is further used to model the performance parameters of the building thermal battery respectively. Among them, the corresponding parameter values of the RC model are obtained by parameter identification. Finally, the heat storage and heat release characteristics of the building integrated energy system are obtained. It makes the application of buildings as batteries more flexible in the urban energy network.

Improving thermal performance of battery at high current rate by using embedded heat pipe system

This study establishes a resistance-based thermal model for the battery cooled by the heat pipe. Unlike the traditional thermal model, the proposed battery thermal model includes the influence of the battery temperature, state of charge (SOC) and current on the heat generation in the battery body. Moreover, it also integrates the heat generation inside the tabs to improve its prediction accuracy. The heat pipe model is developed based on the thermal resistance of its components, and this model is integrated with the battery thermal model to form the thermal model of the BTMS based on the embedded heat pipe system. Experiment are carried out to verify the prediction precision. At the level of the battery unit, the prediction error is within 1 °C. Then, the different heat pipe number, fin number and heat transfer coefficient at the condensation section of the heat pipe are used for the embedded heat pipe system in order to improve its cooling performance. According to the research results, increasing the heat pipe number can reduce the battery temperature and its difference. However, when the heat pipe number is over a certain threshold, both the battery temperature and temperature difference change little. Although the heat transfer coefficient has limited influence on the battery thermal behavior, increasing the heat transfer coefficient and fin number at the same time can reduces the battery temperature a lot. In addition, comparative studies show that the embedded heat pipe system significantly outperforms the bar-type heat pipe and flat heat pipe at an extreme high current rate.

Defect Engineering can Enhance the Electrochemical Performance of WS2 for Thermal Batteries

As a cathode material for thermal batteries, WS2 has high thermal decomposition temperature and large specific capacity, but it is an intermittent semiconductor, with relatively low conductivity. This low conductivity can prolong the activation time and reduce the discharge specific capacity of thermal batteries. Here, we prepared WS2 with sulfur vacancies through a simple high-temperature annealing method and used electron paramagnetic resonance spectroscopy and X-ray photoelectron spectroscopy to detect the presence of sulfur vacancies. The result shows that sulfur vacancies were successfully introduced in WS2, and the existence of sulfur vacancies can effectively improve the discharge performance of thermal batteries. While maintaining the nanostructure, the thermal decomposition temperature still exceeds 1000 °C, which is far beyond the traditional FeS2 (550 °C) and CoS2 (650 °C) cathodes. The Li-B/LiF-LiBr-LiCl/WS2 with sulfur vacancies (treated at 500 °C) couple has higher discharge specific capacity (when the cut-off voltage is 0.5 V, it is 380.58 mAh g−1, which is 14.85% higher than the original WS2) and lower total polarization (about 21% lower than original WS2). This work provides a beginning for further study of sulfur vacancies defect materials as the cathode of thermal batteries.

Enhancing Thermal Performance and Lifetime Cycles of Li-ion Battery in Electric Vehicles

Hybrid energy storage system has essential priority in Electric Vehicle applications. Therefore, the design of an appropriate power sharing algorithm among energy storage components is necessary to improve battery thermal performance and provide extra extension of battery lifetime cycles. This paper presents an analytical study on the effect of using wavelet decomposition-based power sharing algorithm to force the high frequency component to be fed by the supercapacitor and accordingly reduces the thermal stress on the battery. The proposed approach was investigated by applying it on electric vehicle model in ADVISOR Tool/MATLAB using different driving profiles such as Urban Dynamometer Driving Schedule profile, Highway Fuel Economy Test, New York City Cycle, Los Angeles 1992 and new European driving cycle. The results declare that by using proposed power sharing algorithm, the working temperature of lithium battery decreases significantly while battery lifetime cycles increase, apparently. For urban dynamometer driving schedule, the operating temperature of lithium battery is improved much at maximum decomposition levels reaching to only 25.6 °C compared to 35 °C. In addition, the battery lifetime cycles increased from 2213 to 2585 cycles. Neural Networks pattern recognition tool is also applied to classify the driving cycle to the nearest reference cycles chosen to represent the different driving conditions which help to detect the appropriate wavelet decomposition level, achieving better battery thermal performance and battery lifetime cycles.

Working temperature maintenance of thermal batteries by using a slow heat supply component with layer structure and its positive effect on the improvement of electrochemical performance

The discharge performance of thermal batteries with long-life is mainly limited by the decrease of working temperature, due to the continuous heat release during the work process. In this contribution, we firstly propose a slow heat-supply component (SHSC) with layer structure, composed of reducers (Li–Si), oxidizers (CuO) and “lithium” permeation membrane (LPM), to compensate the released heat in thermal batteries. The LPM is composed of electronic conductor (CeO2) and high Li+ molten salt conductor (LiCl–LiBr–KBr), which can modify the permeation rate of “lithium” by changing the electric conductivity. The results confirm that thereaction rates between Li–Si and CuO can be adjusted by changing the weights or compositions of LPM, and the heat supply rate of SHSC can be regulated. By using SHSC, the inner temperature of thermal batteries can be maintained properly. Moreover, the discharge capacity of thermal batteries with long working life, can achieve 10% increase at least, with SHSC as the heat supplied component, which are measured and confirmed in the real thermal batteries.

Thermal modelling and characteristic evaluation of electric vehicle battery system

Thermal modelling of Li-ion battery system used in electric/hybrid electric vehicles is carried out. The main highlight of this study is the numerical modelling of Li-ion battery using finite volume method with the adoption of realistic coupled heat and fluid flow process. Thermal characters of the battery system are analyzed with the change in parameters like flow Reynolds number, battery internal heat generation, the length to width ratio, and the conduction-convection related parameter at the interface of battery and air. In detail analysis of maximum temperature, heat flux variations, Nusselt number, friction coefficient, coolant temperature, and velocity distributions are carried out. Finally, the effect of channel width formed between two parallel placed battery cells is also carried. The numerical analysis performed reveals that the length to width ratio of battery does not impact the thermal performance of battery. At lower Reynolds number, the conduction-convection parameter plays a significant role in reduction of battery temperature avoiding thermal stresses developed. Channel spacing has a prominent role in variation of battery and coolant temperature. The battery surface temperature is largely affected by parameters considered. However, it is at higher input of conduction-convection parameter, Reynolds number, and channel spacing the thermal variation remains insignificant.

Porous mullite fiber nonwoven separator materials containing Nano-MgO particles for the design of thermal batteries

Porous ceramic separator materials have been used to enhance the performance of thermal batteries but they are not sufficiently effective. In this study, we developed a porous ceramic fiber separator substrate using Mullite fiber (a kind of ceramic fiber) employing the wet-laid technology. The substrate was modified using magnesium acetate precursors to obtain a porous, flexible, strong ceramic fiber separator (CFS) containing Nano-MgO particles. Although the diameter of CFS exceeded 11.3 cm, it was relatively thin (approximately 0.3 mm). Application of CFS clearly improved the electrochemical performance of the conventional Li-B/LiF-LiCl-LiBr/FeS2 electrochemical system. Li-B/LiF-LiCl-LiBr/FeS2 electrochemical system fitted with CFS increases the specific capacity of the battery by 24% and yields a polarization resistance of 0.011 Ω even with a high current pulse density of 5000 mA·cm−2. The findings of this study demonstrate that CFS can effectively improve performance of current thermal battery electrochemical systems.

Optimization of Thermal and Structural Design in Lithium-Ion Batteries to Obtain Energy Efficient Battery Thermal Management System (BTMS): A Critical Review.

Covid-19 has given one positive perspective to look at our planet earth in terms of reducing the air and noise pollution thus improving the environmental conditions globally. This positive outcome of pandemic has given the indication that the future of energy belong to green energy and one of the emerging source of green energy is Lithium-ion batteries (LIBs). LIBs are the backbone of the electric vehicles but there are some major issues faced by the them like poor thermal performance, thermal runaway, fire hazards and faster rate of discharge under low and high temperature environment,. Therefore to overcome these problems most of the researchers have come up with new methods of controlling and maintaining the overall thermal performance of the LIBs. The present review paper mainly is focused on optimization of thermal and structural design parameters of the LIBs under different BTMSs. The optimized BTMS generally demonstrated in this paper are maximum temperature of battery cell, battery pack or battery module, temperature uniformity, maximum or average temperature difference, inlet temperature of coolant, flow velocity, and pressure drop. Whereas the major structural design optimization parameters highlighted in this paper are type of flow channel, number of channels, length of channel, diameter of channel, cell to cell spacing, inlet and outlet plenum angle and arrangement of channels. These optimized parameters investigated under different BTMS heads such as air, PCM (phase change material), mini-channel, heat pipe, and water cooling are reported profoundly in this review article. The data are categorized and the results of the recent studies are summarized for each method. Critical review on use of various optimization algorithms (like ant colony, genetic, particle swarm, response surface, NSGA-II, etc.) for design parameter optimization are presented and categorized for different BTMS to boost their objectives. The single objective optimization techniques helps in obtaining the optimal value of important design parameters related to the thermal performance of battery cooling systems. Finally, multi-objective optimization technique is also discussed to get an idea of how to get the trade-off between the various conflicting parameters of interest such as energy, cost, pressure drop, size, arrangement, etc. which is related to minimization and thermal efficiency/performance of the battery system related to maximization. This review will be very helpful for researchers working with an objective of improving the thermal performance and life span of the LIBs.

Activation process modeling and performance analysis of thermal batteries considering ignition time interval of heat pellets

The performance of activation stage of thermal batteries is studied numerically and experimentally. a new heat source simulation model considering ignition time interval of heat pellets is first proposed for solving the problem in performance simulation on thermal batteries during activation stage. Secondly, a simulation model for the activation performance of thermal batteries is constructed and well verified by experiment. Finally, the effects of the number of electrical matches, the ambient temperature and the thickness distribution of heat pellets on the activation performance are analyzed in terms of transient temperature fields. It is found that the activation time of thermal batteries is determined by the time when the bottom electrolyte reaches the melting point. Adding an extra electrical match at the bottom of the battery can reduce the activation time by 5.2% compared with that using only one electrical match at the top of the battery. Furthermore, the activation time is decreased by 18.8% when the ambient temperature raises from 233 K to 333 K. When the thickness of bottom pellets is 10.5 mm and that of middle pellets equals 7.5 mm, the activation time of the battery can be reduced by 6.2%.

Multi-Objective Optimization of Activation Time and Discharge Time of Thermal Battery Using a Genetic Algorithm Approach

Activation time and discharge time are important criteria for the performance of thermal batteries. In this work a heat transfer analysis is carried out on the working process of thermal batteries. The effects of the thicknesses of heat pellets which are divided into three groups and that of the thickness of insulation layers on activation time and discharge time of thermal batteries are numerically studied using Fluent 15.0 when the sum of the thickness of heating plates and insulation layers remain unchanged. According to the numerical results, the optimal geometric parameters are obtained by using multi-objective genetic algorithm. The results show that the activation time is mainly determined by the thickness of the bottom heat pellet, while the discharge time is determined by the thickness of the heat pellets and that of the insulation layers. The discharge time of the optimized thermal battery is increased by 4.08%, and the activation time is increased by 1.23%.

Thermal Characteristics of Stagger-Arranged Battery Pack with Holding Plates Cooled by Longitudinal Airflow

The charging/discharging characteristics and life cycle of a lithium-ion battery are significantly dependent on the battery thermal performance. In this study, the three-dimensional numerical model was developed to explore the effects of thermal conductivities of the battery, holding plate, and diameter of venting holes on the thermal behaviors of the stagger-arranged battery pack cooled by longitudinal airflow. The numerical model was validated by our previous experimental results. Numerical results illustrated that the thermal conductivities of the battery and holding plate have nearly no effect on the thermal behaviors of the 18650 lithium-ion battery pack; therefore, the traditional epoxy (khp=0.2 W·m−1·K−1) is an effective material for the holding plate with the advantages of low cost, excellent insulation, and thermal conductivity properties. The heat-transfer coefficient between the air coolant and battery or holding plates does not gradually decrease along the horizontal airflow direction due to the periodic thinning and damaging of the flow boundary layer caused by the venting holes, which indicates that the venting holes can improve the overall heat-transfer performance of the battery pack. At last, comprehensively considering the effects of the diameter of the venting holes on thermal characteristics, cooling efficiency, and structural strength, the appropriate diameter of the venting holes should be 4 mm for the 18650 lithium-ion battery with holding plates.

Effects of Structure Parameters on the Thermal Performance of a Ternary Lithium-Ion Battery under Fast Charging Conditions

The heat generated by a lithium-ion battery (LIB) under fast charging conditions can influence the charging efficiency, lifetime, and security of the battery. Considering the Joule heat generation of the tabs during the fast charging process, the electrochemical–thermal coupling model of a ternary LIB is built. The voltage and temperature of the battery are calculated during the constant current charging processes of 1 C, 3 C, and 6 C. By comparing the calculation results with the experiment results, the effectiveness of the model is verified. The electrochemical performance and thermal performance of the battery under fast charging conditions are obtained and analyzed through the model. The effects of the structure parameters such as the positive electrode thickness, N/P ratio, separator thickness, tab size, and arrangement on the average volume heat generation rate and temperature rise of the battery are investigated at charging rates of 3 C and 6 C. The conclusions obtained can provide references for the battery structure design and battery thermal management system design oriented to fast charging applications.

Effects of different MgO fiber structures on adhesive capacity and ionic migration of Li–Si/LiCl–KCl/FeS2 thermal batteries

In this article, the MgO imporous fibers, MgO porous fibers and hydrofluoric acid (HF) modified MgO porous fibers were researched as the electrolyte binders in Li–Si/LiCl–KCl/FeS2 thermal batteries respectively. The results show that the wettability between the LiCl–KCl molten salt and the MgO fiber binders increases significantly in order of MgO porous fibers and HF modified MgO porous fibers. The separator pellet using the MgO porous fiber modified by 40 mol% (of the MgO fiber) HF solution as the electrolyte binder exhibits an extremely small amount of electrolyte leakages (19.6 mg cm−2) and the highest ionic conductivity (0.66 S cm−1 at 450 °C). Meanwhile, the corresponding thermal battery shows the largest discharge capacity (425 mA h g−1 at 1.0 V voltage plateau). Moreover, the effect of HF modification on the ion migration was analyzed based on the analysis of element diffusion and the formed MgF2 phase. In summary, modification of MgO porous fiber binder by HF solution is a potential way to improve the performance of thermal batteries.

Thermal management of cylindrical lithium-ion battery based on a liquid cooling method with half-helical duct

To maintain the maximum temperature within the optimum range and to improve the temperature uniformity of cylindrical lithium-ion battery, a liquid cooling method based on the half-helical duct was proposed. The effects of inlet mass flow rate, pitch and number of helical duct, fluid flow direction and diameter of helical duct on the thermal performance of battery at 5 C discharge rate were analyzed numerically. The results showed that the maximum temperature and temperature difference decreased with an increase in the inlet mass flow rate. When the pitch and the number of helical duct changed at the optimal inlet mass flow rate of 3 × 10−4 kg/s, there was no obvious improvement in the cooling performance. If the flow direction was varied according to six kinds of cases, the maximum temperature and the temperature difference for the Case4 all displayed the lowest values. If the diameter of half-helical duct varied from 2.0 mm to 3.8 mm, the temperature difference would retain within 4.3 °C, but the maximum temperature would approach to 30.9 °C, slightly higher than 30.5 °C. In comparison to the thermal management with jacket liquid cooling method, the thermal management with half-helical duct liquid cooling method might be better and more effective owing to the low fluid volume and no stagnant zone.

The Cell Cooling Coefficient: A Standard to Define Heat Rejection from Lithium-Ion Batteries

Lithium-ion battery development is conventionally driven by energy and power density targets, yet the performance of a lithium-ion battery pack is often restricted by its heat rejection capabilities. It is therefore common to observe elevated cell temperatures and large internal thermal gradients which, given that impedance is a function of temperature, induce large current inhomogeneities and accelerate cell-level degradation. Battery thermal performance must be better quantified to resolve this limitation, but anisotropic thermal conductivity and uneven internal heat generation rates render conventional heat rejection measures, such as the Biot number, unsuitable. The Cell Cooling Coefficient (CCC) is introduced as a new metric which quantifies the rate of heat rejection. The CCC (units W.K−1) is constant for a given cell and thermal management method and is therefore ideal for comparing the thermal performance of different cell designs and form factors. By enhancing knowledge of pack-wide heat rejection, uptake of the CCC will also reduce the risk of thermal runaway. The CCC is presented as an essential tool to inform the cell down-selection process in the initial design phases, based solely on their thermal bottlenecks. This simple methodology has the potential to revolutionise the lithium-ion battery industry.

Structural optimization of lithium-ion battery for improving thermal performance based on a liquid cooling system

Liquid cooling system is of great significance for guaranteeing the performance of lithium-ion battery because of its good conductivity to keep battery working in a cool environment. In this paper, a liquid cooling system for lithium-ion battery with changing contact surface is designed. Contact surface is determined by the width of cooling plate. Mathematical derivation and numerical analysis are conducted to evaluate cooling performance and the consumption of pump power. The results show that increasing inlet mass flow can effectively limit the maximum temperature, but cannot improve temperature uniformity significantly. The temperature is proportional to the inlet temperature, but inversely proportional to the width of cooling plate. Considering the effect of temperature on thermal properties, the thermal properties will weaken the effect of width of cooling plate, inlet temperature and mass flow rate on temperature performance, specifically the maximum temperature and temperature difference, and cause temperature changes in a nonlinear manner. It is difficult to improve the overall performance of the battery by only optimizing a single factor. Three factors (mass flow rate, inlet temperature, the width of cooling plate) for the thermal performance of battery are optimized by using the single factor analysis and the orthogonal test. The best cooling performance can be obtained when inlet temperature is 18 °C, the width of cooling plate is 70 mm and the mass flow rate is 0.21 kg/s. With the use of the optimization method, the lower bound of temperature and the temperature uniformity of battery are achieved and the pump consumption can be reduced. The strategy adopted in this research can be widely applied to battery thermal management to reduce analysis time.

Microsized Pyrite Used As Cathode Material to Improve the Electrochemical Performance of Thermal Battery

Influences of particle sizes on the discharge performances of microsized pyrite has been investigated, 15µm ~30µm 50µm ~75µm and 100µm ~150µm pyrite samples were manufactured. Single cell thermal batteries were fabricated for microsized pyrite evaluation. The cells were tested at 400 oC and 500 oC under baseline loads of 0.2 A/cm2 and 0.5 A/cm2 respectively, to evaluate the influences of temperature on the electrochemical performance of a thermal battery. Pulse current discharges were also used to test the discharge performance of the single cell thermal battery with different pyrite particle sizes. The results showed that cells with smaller pyrite particles had higher voltage plateau and larger specific capacities, were able to sustain higher current densities than cells with larger pyrite particle sizes. The pulse current test under 400 oC showed that the cell cannot afford the current, and the 15µm ~30µm pyrite thermal battery own the largest discharge current, which may be due to the large contact between the pyrite and the electrolyte. 8-cell thermal batteries were used to conduct the discharging test at 0.2 A/cm2 0.5 A/cm2 and pulse current conditions, which revealed that battery with 15µm ~30µm pyrite cathode had higher votage plateau and larger specific capacity than the 100µm ~150µm ones. At 0.5 A/cm2 discharge conditions, the power densities of the 15µm ~30µm pyrite thermal battery stacks is 12.5% higher than that of the 100µm ~150µm ones. Through the investigation of the electrochemical performance of the 15µm ~30µm pyrite thermal battery, they are suitable for thermal batteries discharging at large current densities. Figure 1

Modeling and optimization of an enhanced battery thermal management system in electric vehicles

This paper models and optimizes an air-based battery thermal management system (BTMS) in a battery module with 36 battery lithium-ion cells. A design of experiments is performed to study the effects of three key parameters (i.e., mass flow rate of cooling air, heat flux from the battery cell to the cooling air, and passage spacing size) on the battery thermal performance. Three metrics are used to evaluate the BTMS thermal performance, including (i) the maximum temperature in the battery module, (ii) the temperature uniformity in the battery module, and (iii) the pressure drop. It is found that (i) increasing the total mass flow rate may result in a more non-uniform distribution of the passage mass flow rate among passages, and (ii) a large passage spacing size may worsen the temperature uniformity on the battery walls. Optimization is also performed to optimize the passage spacing size. Results show that the maximum temperature difference of the cooling air in passages is reduced from 23.9 to 2.1 K by 91.2%, and the maximum temperature difference among the battery cells is reduced from 25.7 to 6.4 K by 75.1%.