Review on use of phase change materials in battery thermal management for electric and hybrid electric vehicles

The battery electric vehicle is evolving and has the potential to replace conventional internal combustion‐based vehicles in the future. Batteries are the major power source of these vehicles. A thermal management system is required for a battery to attain effective operation and long life in all environmental conditions. Although several types of thermal management system are available, there remains a need to address various issues like high power consumption, narrow optimum temperature range and operation in varying climates. Phase change materials can assist in resolving these issues. In this paper, battery thermal management systems for electric and hybrid electric vehicles are reviewed, and challenges and opportunities for battery electric vehicles are discussed. Cooling strategies used in various thermal management systems are explained. Applications of and issues regarding the use of phase change materials in thermal management systems are also reviewed. Potential bottlenecks that need to be addressed in electric vehicle technology are explained, as are important achievement milestones and trends regarding the growth of the electric vehicle industry. It is shown that using graphite can increase thermal conductivity of PCMs by up to 70 W m^{‐ 1}K^{‐ 1}. Some commercially available passive thermal management systems for batteries use wax and graphite, which can increase the driving range of an electric scooter from 30 km to 55 km. Copyright © 2016 John Wiley & Sons, Ltd.     

The ability of battery second use strategies to impact plug-in electric vehicle prices and serve utility energy storage applications

The high cost of lithium ion batteries is a major impediment to the increased market share of plug-in hybrid electric vehicles (PHEVs) and full electric vehicles (EVs). The reuse of PHEV/EV propulsion batteries in second use applications following the end of their automotive service life may have the potential to offset the high initial cost of these batteries today. Accurately assessing the value of such a strategy is exceedingly complex and entails many uncertainties. This paper takes a first step toward such an assessment by estimating the impact of battery second use on the initial cost of PHEV/EV batteries to automotive consumers and exploring the potential for grid-based energy storage applications to serve as a market for used PHEV/EV batteries. It is found that although battery second use is not expected to significantly affect today's PHEV/EV prices, it has the potential to become a common component of future automotive battery life cycles and potentially to transform markets in need of cost-effective energy storage. Based on these findings, the authors advise further investigation focused on forecasting long-term battery degradation and analyzing second-use applications in more detail.     

Does energy storage provide a profitable second life for electric vehicle batteries?

Electric vehicles (EVs) are increasingly being seen as part of the solution to address environmental issues related to fossil fuel use. At the forefront of the EV revolution is China where EV sales have witnessed a dramatic increase. A direct consequence of a larger number of EVs on the roads is the growth in retired batteries once they have reached the end of their useful life inside an EV. This increasing stockpile of retired batteries raises the question of whether and how they can be disposed of, reused, repurposed or recycled. In this paper we investigate under which circumstances the use of second life batteries in stationary energy storage systems in China can be profitable using an operational optimization model. Our results show that an EV battery could achieve a second life value of 785 CNY/kWh (116 USD/kWh) if it is purchased with a remaining capacity of 80% and being abandoned when the capacity reaches 50%. Profit margins for energy storage firms are reduced if the acquisition costs of second life batteries are considered. The price range for second life batteries is assumed to range between a lower limit of the ‘Willing to sell’ price from the perspective of EV owners and an upper limit being the ‘Market evaluation’ price based on battery condition and the market price for a new EV battery. It's found that when the remaining capacity in retirement is below 87%, the application of retired battery energy storage can achieve pareto improvement from the perspective of social welfare. In addition, it's estimated that the optimal remaining capacity in retirement would be 77%. Our results suggest that EV adoption rates can be improved if a second life market can be successfully established.     

Use of lithium-ion batteries in electric vehicles

An account is given of the lithium-ion (Li-ion) battery pack used in the Northern Territory University's solar car, Fuji Xerox Desert Rose, which competed in the 1999 World Solar Challenge (WSC). The reasons for the choice of Li-ion batteries over silver–zinc batteries are outlined, and the construction techniques used, the management of the batteries, and the battery protection boards are described. Data from both pre-race trialling and race telemetry, and an analysis of both the coulombic and the energy efficiencies of the battery are presented. It is concluded that Li-ion batteries show a real advantage over other commercially available batteries for traction applications of this kind.     

Investigating electrical contact resistance losses in lithium-ion battery assemblies for hybrid and electric vehicles

Lithium-ion (Li-ion) batteries are favored in hybrid-electric vehicles and electric vehicles for their outstanding power characteristics. In this paper the energy loss due to electrical contact resistance (ECR) at the interface of electrodes and current-collector bars in Li-ion battery assemblies is investigated for the first time. ECR is a direct result of contact surface imperfections, i.e., roughness and out-of-flatness, and acts as an ohmic resistance at the electrode-collector joints. A custom-designed testbed is developed to conduct a systematic experimental study. ECR is measured at separable bolted electrode connections of a sample Li-ion battery, and a straightforward analysis to evaluate the relevant energy loss is presented. Through the experiments, it is observed that ECR is an important issue in energy management of Li-ion batteries. Effects of surface imperfection, contact pressure, joint type, collector bar material, and interfacial materials on ECR are highlighted. The obtained data show that in the considered Li-ion battery, the energy loss due to ECR can be as high as 20% of the total energy flow in and out of the battery under normal operating conditions. However, ECR loss can be reduced to 6% when proper joint pressure and/or surface treatment are used. A poor connection at the electrode-collector interface can lead to a significant battery energy loss as heat generated at the interface. Consequently, a heat flow can be initiated from the electrodes towards the internal battery structure, which results in a considerable temperature increase and onset of thermal runaway. At sever conditions, heat generation due to ECR might cause serious safety issues, sparks, and even melting of the electrodes.     

Thermal Management in Hybrid Power Systems Using Cylindrical and Prismatic Battery Cells

Lithium ion (Li-ion) batteries are promising as both alternative and auxiliary power sources in hybrid and electric vehicles. However, the reliable and efficient operation of the Li-ion batteries depends critically on effective thermal management, due to both the high operational thermal loads and the possible range operational conditions. This work therefore studied the issue of thermal management of battery systems under extreme hot conditions. This study combined both experimental testing and high-fidelity computer fluid dynamics (CFD). Due to the difficulty of conducting experiments under extreme conditions, controlled experiments were first conducted so that CFD models could be validated. The validated CFD models were then applied to study various aspects of thermal management issues in battery systems, with an emphasis on comparing the operation of prismatic and cylindrical batteries under extremely hot environments. The results presented include temperature distribution among cells, pump power required, and different geometrical layouts of the cells. These results are expected to provide insights into the design and optimization of battery systems.     

电动汽车电池的充电状态和健康状况评估：关键问题和挑战

使用电动汽车（EV）进行运输被视为实现可持续发展和解决环境问题的必要组成部分。当前对环境的关注,例如化石燃料的快速消耗,空气污染的增加,能源需求的加速增长,全球变暖和气候变化,为交通运输部门的电气化铺平了道路。电动汽车可以解决上述问题。电源已成为电动汽车发展的关键,尤其是锂离子（Li-ion）电池。由于其能量密度、功率...     

A new battery capacity indicator for lithium-ion battery powered electric vehicles using adaptive neuro-fuzzy inference system

This paper describes a new adaptive neuro-fuzzy inference system (ANFIS) model to estimate accurately the battery residual capacity (BRC) of the lithium-ion (Li-ion) battery for modern electric vehicles (EVs). The key to this model is to adopt newly both the discharged/regenerative capacity distributions and the temperature distributions as the inputs and the state of available capacity (SOAC) as the output, which represents the BRC. Moreover, realistic EV discharge current profiles are newly used to formulate the proposed model. The accuracy of the estimated SOAC obtained from the model is verified by experiments under various EV discharge current profiles.     

Realistic electric vehicle battery evaluation

The STM-5-140 nickel cadmium electric vehicle battery was tested under actual operating conditions using the UMASS Lowell battery evaluation laboratory. The battery evaluation system uses battery current data taken from an EV using its on board data acquisition system. The car is driven on a typical commute while battery current as well as other data are taken at one second intervals. In the battery evaluation lab, individual batteries are subjected to the same operating conditions as those in the car. This procedure uses fewer batteries and allows the same commute to be repeated exactly. Three test procedures using 0, 20, and 40 degree centigrade controlled environment temperatures were implemented. Measured data consisted of voltage, current, and temperature. Test cycle, capacity and round trip efficiency data are presented     

Multi-step constant-current charging method for electric vehicle,valve-regulated,lead/acid batteries during night time for load-levelling

For the popularization of electric vehicles (EVs), the conditions for charging EV batteries with available current patterns should allow complete charging in a short time, i.e., less than 5 to 8 h. Therefore, in this study, a new charging condition is investigated for the EV valve-regulated lead/acid battery system, which should allow complete charging of EV battery systems with multi-step constant currents in a much shorter time with longer cycle life and higher energy efficiency compared with two-step constant-current charging. Although a high magnitude of the first current in the two-step constant-current method prolongs cycle life by suppressing the softening of positive active material, too large a charging current magnitude degrades cells due to excess internal evolution of heat. A charging current magnitude of approximately 0.5 C is expected to prolong cycle life further. Three-step charging could also increase the magnitude of charging current in the first step without shortening cycle life. Four-or six-step constant-current methods could shorten the charging time to less than 5 h, as well as yield higher energy efficiency and enhanced cycle life of over 400 cycles compared with two-step charging with the first step current of 0.5 C. Investigation of the degradation mechanism of the batteries revealed that the conditions of multi-step constant-current charging suppressed softening of positive active material and sulfation of negative active material, but, unfortunately, advanced the corrosion of the grids in the positive plates. By adopting improved grids and cooling of the battery system, the multistep constant-current method may enhance the cycle life.     

Hybrid electric vehicles and electrochemical storage systems — a technology push–pull couple

In the advance of fuel cell electric vehicles (EV), hybrid electric vehicles (HEV) can contribute to reduced emissions and energy consumption of personal cars as a short term solution. Trade-offs reveal better emission control for series hybrid vehicles, while parallel hybrid vehicles with different drive trains may significantly reduce fuel consumption as well. At present, costs and marketing considerations favor parallel hybrid vehicles making use of small, high power batteries. With ultra high power density cells in development, exceeding 1 kW/kg, high power batteries can be provided by adapting a technology closely related to consumer cell production. Energy consumption and emissions may benefit from regenerative braking and smoothing of the internal combustion engine (ICE) response as well, with limited additional battery weight. High power supercapacitors may assist the achievement of this goal. Problems to be solved in practice comprise battery management to assure equilibration of individual cell state-of-charge for long battery life without maintenance, and efficient strategies for low energy consumption.     

Extended-range electric vehicles and their lithium-ion batteries

增程式电动汽车(E-REV,extended-range electric vehicle),是指在纯电动汽车基础上,增加一个内燃发电机增程器(RE),给电池充电或直接驱动电机以增加续航里程,从而克服纯电动汽车续驶里程短的瓶颈的新型电动汽车.是介于传统混合动力汽车与纯电动汽车之间的车辆类型,在排放,噪音,系统复杂性等方面优于传统混合动力汽车,但又比纯电动汽车在续驶里程和成本方面更具优势,因此,E-REV更具大规模商业化应用推广价值.E-REV所携带的动力电池本身的续驶里程并不大,但它要求具备更高的效率,同时具备高能量密度与高功率密度,这势必给锂离子电池的发展带来新的挑战与机遇.本文简要介绍E-REV及其发展以及对我国新能源汽车发展的重要意义,在此基础上,重点对适合于E-REV的动力电池进行分析.     

Experimental validation for Li-ion battery modeling using Extended Kalman Filters

The battery management systems (BMS) is an essential emerging component of both electric and hybrid electric vehicles (HEV) alongside with modern power systems. With the BMS integration, safe and reliable battery operation can be guaranteed through the accurate determination of the battery state of charge (SOC), its state of health (SOH) and the instantaneous available power. Therefore, undesired power fade and capacity loss problems can be avoided. Because of the electrochemical actions inside the battery, such emerging storage energy technology acts differently with operating and environment condition variations. Consequently, the SOC estimation mechanism should cope with the probable changes and uncertainties in the battery characteristics to ensure a permanent precise SOC determination over the battery lifetime.This paper aims to study and design the BMS for the Li-ion batteries. For this purpose, the system mathematical equations are presented. Then, the battery electrical model is developed. By imposing known charge/discharge current signals, all the parameters of such electrical model are identified using voltage drop measurements. Then, the extended kalman filter (EKF) methodology is employed to this nonlinear system to determine the most convenient battery SOC. This methodology is experimentally implemented using C language through micro-controller. The proposed BMS technique based on EKF is experimentally validated to determine the battery SOC values correlated to those reached by the Coulomb counting method with acceptable small errors.     

On the synergy between large electric vehicle fleet and high wind penetration – An analysis of the Danish case

Increasing the level of wind power penetration beyond the present level in the Danish power system implies large challenges when it comes to energy management and system stability. Plug-in electric vehicles promise to contribute to the flexibility of the energy system by creating a link between the power system and the transportation sector and provide the possibility to make use of the inherent energy storage of a large electric vehicle (EV) fleet. The present work investigates the effects of different EV charging strategies on the balance between wind power production and consumption in a future Danish power system. The results show that an electrification of the transport sector will indeed reduce the excess of wind power, but additional mechanisms are needed if the full wind power potential in Denmark is utilized. Further it is foreseen that the vehicle-to-grid option (where the vehicle batteries are used as backup at times with little wind power production) will have very limited effects on the overall energy management and is more likely to be used only for regulation and reserve services, also in the longer perspective.     

The future of electric two-wheelers and electric vehicles in China

The method of force field analysis is used to examine the future technological and market evolution of electric two-wheelers (E2W) in China. The authors identify key forces driving and resisting future E2W market growth, root causes behind these forces, and important insights about the likelihood of a wide shift to larger three- and four-wheel electric vehicles (EV). The authors conclude that the key forces driving E2W market growth are: improvements in E2W and battery technology due to product modularity and modular industry structure, strong local regulatory support in the form of gasoline-powered motorcycle bans and loose enforcement of E2W standards, and deteriorating bus public transit service. The largest forces resisting E2W market growth are strong demand for gasoline-powered motorcycles, bans on E2Ws due to safety concerns in urban areas, and growing support for public transit. The balance of these forces appears to favor E2W market growth. This growth will likely drive vehicle electrification through continued innovation in batteries and motors, the switch from lead-acid to Li-ion batteries in E2Ws, and the development of larger E2Ws and EVs. There are however strong forces resisting vehicle electrification, including battery cost, charging infrastructure, and inherent complications with large battery systems.     

The use of computer simulation in the evaluation of electric vehicle batteries

An integrated simulation and testing approach is presented to evaluate batteries for electric vehicle (EV) applications. This new approach combines traditional experimental testing with computer simulations to create a cost-effective means to evaluate EV batteries and provide important information that is difficult or impossible to obtain from purely experimental measurements. The present simulators for the lead–acid and nickel–metal hydride (Ni–MH) batteries are developed based on the fundamental principles governing their electrochemical behaviors and are created using an advanced computational fluid dynamics (CFD) technique. Computer simulations are validated by experimental data under the dynamic stress test (DST) procedure for a lead–acid battery module and a Ni–MH cell with good agreement. Moreover, computer simulations reveal that the studied lead–acid battery underutilizes the active material by as much as 70% and the MH electrode of the Ni–MH cell is overdesigned by about 30% under the simulated EV duty. Therefore, there is good potential of increasing the specific energy and reducing the cost if batteries are optimized for EVs using a simulation-based design approach.     

Recent progress in lithium-ion battery thermal management for a wide range of temperature and abuse conditions

Lithium-ion batteries are important power sources for electric vehicles and energy storage devices in recent decades. Operating temperature, reliability, safety, and life cycle of batteries are key issues in battery thermal management, and therefore, there is a need for an effective thermal-management system. This review summarises the latest research progress on lithium-ion battery thermal management under high temperature, sub-zero temperature, and abuse conditions. Heat generation mechanisms are characterised under both normal and abuse conditions. Different cooling methods, which include air cooling, liquid cooling, phase change cooling, heat pipe cooling, and their combinations are reviewed and discussed. Thereafter, features of different battery heating methods such as air/liquid heating, alternate current heating, and internal self-heating are discussed. An improvement in battery safety under abuse conditions is discussed from the perspective of battery material modification and thermal management design. The research progress in recent investigations is summarised, and the prospects are proposed.     

Thermal analysis and management of lithium-titanate batteries

Battery electric vehicles and hybrid electric vehicles demand batteries that can store large amounts of energy in addition to accommodating large charge and discharge currents without compromising battery life. Lithium-titanate batteries have recently become an attractive option for this application. High current thresholds allow these cells to be charged quickly as well as supply the power needed to drive such vehicles. These large currents generate substantial amounts of waste heat due to loss mechanisms arising from the cell's internal chemistry and ohmic resistance. During normal vehicle operation, an active cooling system must be implemented to maintain a safe cell temperature and improve battery performance and life. This paper outlines a method to conduct thermal analysis of lithium-titanate cells under laboratory conditions. Thermochromic liquid crystals were implemented to instantaneously measure the entire surface temperature field of the cell. The resulting temperature measurements were used to evaluate the effectiveness of an active cooling system developed and tested in our laboratory for the thermal management of lithium-titanate cells.     

Progress on high energy density lithium batteries by CAS battery research group

提高动力电池的能量密度将显著延长续航里程,对发展电动汽车具有重要的意义.中国科学院在2013年底部署了中国科学院战略性先导科技专项,通过合作研究,积极探索了第三代锂离子电池,固态锂电池,锂-硫电池和锂-空气电池等电池体系.其中,采用纳米硅碳负极,富锂正极的24 A·h的锂离子电池单体,质量能量密度达到374 W·h/kg,体积能量密度达到577 W·h/L.8 A·h固态聚合物锂电池60 ℃下能量密度达到240 W·h/kg,基于无机陶瓷固态电解质的固态锂电池室温下能量密度达到240 W·h/kg.37 A·h的锂硫电池单体室温能量密度达到566 W·h/kg,50 ℃达到616 W·h/kg.5 A·h锂空气电池单体能量密度达到526 W·h/kg.目前这些样品电池在综合技术指标方面离实际应用还有较大的距离,需要进一步深入细致的进行基础科学与关键技术方面的研究.从长远考虑,电池能量密度的提高必然进一步增加电池安全性风险,因此不同形式的固态锂电池将是未来长续航动力锂电池的发展方向.     

A review on lithium-ion power battery thermal management technologies and thermal safety

Lithium-ion power battery has become one of the main power sources for electric vehicles and hybrid electric vehicles because of superior performance compared with other power sources.In order to ensure the safety and improve the performance,the maximum operating temperature and local temperature difference of batteries must be maintained in an appropriate range.The effect of temperature on the capacity fade and aging are simply investigated.The electrode structure,including electrode thickness,particle size and porosity,are analyzed.It is found that all of them have significant influences on the heat generation of battery.Details of various thermal management technologies,namely air based,phase change material based,heat pipe based and liquid based,are discussed and compared from the perspective of improving the external heat dissipation.The selection of different battery thermal management (BTM) technologies should be based on the cooling demand and applications,and liquid cooling is suggested being the most suitable method for large-scale battery pack charged/discharged at higher C-rate and in high-temperature environment.The thermal safety in the respect of propagation and suppression of thermal runaway is analyzed.