Research progress in the consistency screening of Li-ion batteries

锂离子电池因综合性能优良,近年来在移动储能和固定储能领域的应用发展迅速。当多个单体电池通过串并联组成电池模组时,不仅电池组的能量低于电池单体能量的加和,电池组的寿命也明显低于单体电池的水平。除了电池运行环境不均匀（如温度场）外,电池组内部电池单体之间微小的不一致性也是造成电池组性能快速衰减的主要原因。依据电池组的结构建立电池一致性的筛选方法和标准,是目前锂离子电池模组研究中亟待解决的关键技术。本文回顾了近年来国内外锂离子电池一致性筛选方法研究领域的进展,对锂离子电池一致性的内涵进行了剖析,并重点对串联筛选方法进行了评述。     

Development of lithium batteries for energy storage and EV applications

The results of the Japanese national project of R&D on large-size lithium rechargeable batteries by Lithium Battery Energy Storage Technology Research Association (LIBES), as of fiscal year (FY) 2000 are reviewed. Based on the results of 10 Wh-class cell development in Phase I, the program of Phase II aims at further improvement of the performance of large-size cells and battery modules, and the formulation of roadmaps toward worldwide dissemination of large-size lithium secondary batteries. In addition to the above R&D programs, a new target was presented particularly for the near-term practical application of several kWh-class battery modules in FY 1998.

For the large-size battery modules, two types of 2 and 3 kWh-class battery modules have been developed for stationary device and electric vehicle applications, respectively. The battery modules for both types have achieved most of the targets other than cycle life. Currently, further improvements in the cycle life of the cells themselves are being pursued. For this purpose, the materials for cathodes and anodes, the shapes and structures for batteries and the methods for cell connection are being re-investigated.

The development of middle-size battery systems for mini-size electric vehicles (EVs), as well as for demand-side stationary device applications is under way. These battery systems have been fabricated and their fundamental performance confirmed. They are now being subjected to field tests.     

Thermal behavior of lithium batteries used in electric vehicles using phase change materials

Electric vehicles equipped with lithium-ion batteries face a huge challenge, and the fact that battery life is very much affected by the temperature conditions of their operating environment, the heat reduces battery life cycle and time and increases the likelihood of thermal degradation and explosion. This problem has forced engineers to cool the battery. The methods used to cool the battery includes a cool water method (passing water or a dielectric fluid from the battery pack), cooling air (blowing air into the battery compartment by the fan), using a refrigeration system (such as cooling screens), and the use of phase-change material (PCM). In this research after reviewing and referring to valid authorities, it was found that PCMs are superior to all three other cooling systems because the air-conditioning system is not very desirable due to the high-temperature gradient between the battery cells. Also, cooling and refrigeration systems with refrigerant gases will also cost a very high cost on the electric car. The results of the studies showed that the cooling the battery using the PCM creates a similar temperature profile between the batteries in the battery pack, the temperature gradient is much smaller than the air cooler and cool water, and the final cost will be much lower. Also, it performs more efficiently in high-speed road dynamics and increases the battery life of an electric car or electric hybrid.     

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.     

Brief analysis the safety of solid-state lithium ion batteries

锂二次电池因其具有能量密度高、循环寿命长、无记忆效应、无污染等优点,使得其在便携式消费电子产品、电动汽车、能量储存等领域具有广泛的应用前景。目前,锂二次电池的能量密度和安全性是当今世界的研究热点。但对于传统液态电解质的锂离子电池而言,尽管从材料、模组、电源管理、热管理、系统设计等各个层面均采取了多种改进措施,然而高能量密度电芯的安全性问题依然突出,热失控问题难以彻底避免。因此,为了提高锂电池的安全性,发展理论上不易燃的固态锂电池是解决锂电池安全问题的必由途径。本工作比较了传统液态锂离子电池与固态锂电池结构特征,总结了其各自优缺点,进一步深入剖析了传统液态锂离子电池安全问题产生的根本原因,提出了解决锂离子电池安全性问题的最佳方案,并通过对自主研发的系列容量固态锂（离子）电池的安全性能进行测试,证实了固态锂电池的高安全特性。     

Research progress on thermogenic characteristics of lithium ion batteries

锂离子电池产热特性直接影响着其实际应用中的性能（如容量、内阻和功率等）和热安全问题,一直是消费者最关心的方面。为了更好地指导锂离子电池的设计和使用策略的制定,使其能够安全和高效地应用于生产和生活,深入研究锂离子电池在各种工况条件下的产热特性是十分重要和必须的。主要从实验手段和模型仿真方法两个方面来分别对锂离子电池热问题研究进展进行全面详细地总结和分析,并指出两种不同研究方法的优缺点。因此,在以后的研究中,科研工作者应该将实验手段和模型仿真方法结合起来研究锂离子电池的热问题。     

Graft copolymer separators — development and use

Graft copolymer membranes have been used for a number of years as interelectrode separators in alkaline batteries either singly, laminated to cellophane, or in conjunction with other materials such as felts.The preparation details of some of the Royal Military College of Science's copolymers are summarised with emphasis on the production of commercial quantities having a high degree of uniformity and reproducibility. Important properties in a battery environment are discussed and, where possible, compared with other separator materials; notably cellophane.The use of graft copolymers in a number of primary and secondary alkaline battery systems is reported and test data given. Conclusions are drawn relating the properties of these separators to their performance in cells.     

Polymer Electrolyte Membranes for Vanadium Redox Flow Batteries: Fundamentals and Applications

Electrochemical energy storage systems are considered as one of the most viable solutions to realize large-scale utilization of renewable energy. Among the various electrochemical energy storage systems, flow batteries have increasingly attracted global attention due to their flexible structural design, high efficiencies, long operating life cycle, and independently tunable power and energy storage capacity. Although promising, a number of challenges including the high cost of flow battery materials hinder the broad market penetration of flow battery technology. Polymer electrolyte membrane, as a key component in flow batteries providing pathways for charge carriers transport and preventing electrolytes crossover, takes over 25% of the entire cost of the battery system. Apparently, the membrane not only plays pivotal roles in the operation characteristics of a flow battery, but also largely influences the financial cost of the battery system. To provide insights and better understanding of membranes towards enhancing their performance and cost-effectiveness, we therefore present recent advances and research outcomes on the development of polymer electrolyte membranes as well as their applications in flow batteries, particularly all-vanadium redox flow batteries. Various aspects of polymer electrolyte membranes including functional requirements, characterization methods, materials screening and preparation strategies, transport mechanisms, and commercialization progress are presented. Finally, perspectives for future trends on research and development of polymer electrolyte membranes with relevance to flow batteries are highlighted.     

A review on lithium iron phosphate cathode materials

目前全球高动力锂离子电池系统的发展主要集中在锂锰电池,锂钴镍锰电池以及锂铁电池,其中磷酸亚铁锂材料具有高电容量,高放电功率,极佳的长循环寿命以及良好的热稳定性与高温性能等优点,已成为动力锂离子电池首选的高安全性正极材料.然而,磷酸亚铁锂材料在工业化量产时,必须解决电池芯加工性差及材料一致性不佳等问题,作者曾结合多项新颖观念与技术于磷酸亚铁锂材料制做过程,在粉体表面涂布碳层,在晶体内部掺杂金属,分别改善材料电导率与锂离子扩散速度以及有效地控制碳含量,粉体比表面积,碳层均匀性,粒径大小与分布,制备出高质量磷酸亚铁锂产品.该文将回顾并探讨上述研发工作的一些重要结果.     

Performance assessment of thermal management systems for electric and hybrid electric vehicles

Thermal management systems (TMS) are one of the key components of electric and hybrid electric vehicles to achieve high vehicle efficiency and performance under all operating conditions. Current improvements in electric battery technology allow vehicles to have relatively long ranges, fast acceleration, and long life while keeping low‐maintenance costs and considerably lower emissions. However, the vehicle performance is significantly affected by the battery operating conditions. Moreover, the cell life cycle, safety, and possibility of thermal runaway significantly depend on peak temperature rise and temperature uniformity of the battery. Therefore, various TMSs are created to keep batteries within ideal operating ranges. In this article, three different TMS systems—passive cabin cooling (via air), active moderate liquid circulation (via refrigerant), and active liquid circulation (via refrigerant and coolant)—are analyzed and compared with electric and hybrid electric vehicles. A second law analysis is used to examine the areas of low exergy efficiency in each system and minimize the entropy generation based on the system configuration. Moreover, TMS systems are compared on the basis of battery temperature increase and temperature uniformity. Various parametric studies are conducted to compare the TMS in different ambient and operating conditions. On the basis of the analysis, the active liquid circulation (via refrigerant and coolant) is determined to have the lowest battery temperature increase (3.9 °C in 30 min) and most cell temperature uniformity (2.5 °C median) as well as the lowest entropy generation rate (0.0121 W/K) among the compared systems. Copyright © 2012 John Wiley & Sons, Ltd.     

Development and field experience of monitoring system for valve-regulated lead–acid batteries in stationary applications

With ever-evolving information technology, it is becoming increasingly important to secure reliable back-up power supplies in telecommunications networks, data-processing facilities, utilities, etc. While valve-regulated lead–acid (VRLA) batteries are predominantly used nowadays, their diagnosis technology is not fully developed. As partial-discharge techniques require temporarily shutting-down of the system and also degrade battery life, manual testers based on an ohmic techniques have become popular. Accordingly, the Battery Condition Watcher (BCW) has been developed and commercialized. This is an automatic monitoring system with remote communication capabilities. It measures the internal impedance, voltage and temperature of individual cells or batteries with high accuracy. These parameters are subjected to data processing to enable diagnosis of battery conditions and life. Some aspects of field usage of the BCW are reported.     

Review of lithium-ion battery state of charge estimation

The technology deployed for lithium-ion battery state of charge (SOC) estimation is an important part of the design of electric vehicle battery management systems. Accurate SOC estimation can forestall excessive charging and discharging of lithium-ion batteries, thereby improving discharge efficiency and extending cycle life. In this study, the key lithium-ion battery SOC estimation technologies are summarized. First, the research status of lithium-ion battery modeling is introduced. Second, the main technologies and difficulties in model parameter identification for lithium-ion batteries are discussed. Third, the development status and advantages and disadvantages of SOC estimation methods are summarized. Finally, the current research problems and prospects for development trends are summarized.     

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.     

Charge regimes for valve-regulated lead-acid batteries: Performance overview inclusive of temperature compensation

The main battery type employed in standby applications is the valve-regulated lead-acid (VRLA) battery. Float charging is normally used to maintain the battery in its fully charged state, however, float charging has limitations that can damage the battery and shorten its life. New charge regimes have evolved in recent years to tackle the intrinsic problems of float charging. The intermittent charge (IC) regime and the interrupted charge control (ICC) regime have been developed to prolong the service life of the battery in standby applications. The battery is normally maintained in the standby mode for a long period of time and there are infrequent discharge tests to verify the efficacy of the battery. Hence, the service life of the battery is highly correlated to its charge regime. This paper reviews the charge regimes for VRLA batteries, and assesses their charging performance and their impact on the service life of the battery. Recognising that temperature plays a significant role in battery operation, temperature compensation schemes are described for different charge regimes.     

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.     

Improved oxides for production of lead/acid battery plates

For many years, the plates of lead/acid batteries have been produced from leady oxide, a mixture of finely divided lead (`free-lead') and lead monoxide. Although this material is generally satisfactory, it suffers from the disadvantages that it is variable in composition and requires complicated and lengthy processing after pasting to remove the residual free-lead. Plates made from leady oxide also require cycling before they achieve their full performance, and this can result in either depressed initial capacity or additional processing cost. There is a growing trend towards the use of pure lead monoxide (β-PbO) for the production of positive plates. This material is particularly valuable in valve-regulated batteries where cell-to-cell uniformity is essential for proper control of battery performance. It also reduces processing cost since it does not require time-consuming curing to remove free-lead. Red lead (Pb₃O₄) is also being more widely used in industrial batteries since it reduces formation time, and improves initial and high-rate performance. The methods of production of leady oxide, β-PbO and red lead are briefly reviewed and the characteristics of battery-grade materials are described. Particular emphasis is placed on optimum particle-size distribution, and how this can affect the battery performance. The benefits in processing and performance are described together with information on how pure litharge and red lead are used in battery plates.     

Review of research on heat generation characteristics during charging and discharging of lithium ion batteries

电动车辆的性能和成本很大程度上取决于动力电池组的性能和使用寿命,而电池组的性能和使用寿命又受到电池单体产热的影响。研究锂离子电池充放电过程中的产热特性及影响因素,对锂电池的开发及使用具有指导意义。本文从环境温度、充放电倍率、电池材料、荷电状态和老化程度五个方面入手,综述了各因素对锂离子电池产热的影响。     

The corresponding relationship of cycle life for LIB from three-dimensional

动力电池寿命极大程度上影响电动汽车使用寿命,是决定车辆经济效益的重要因素。除已有研究的单体寿命外,模组和电池系统寿命接近整车使用状态,更具有研究意义。在电池单体基础上,增加模组和电池系统,率先构建单体-模组-电池系统三维层级。以锰酸锂软包单体电池为最小电池单元,研究以此构成的两个型号、三维层级间电池循环老化过程中电化学特性、容量衰减和循环温度变化情况。结果表明,特定冷却环境下,在循环容量衰减方面,三个层级间关系为电池系统衰减 > 模组衰减 > 单体衰减;在循环温度方面,模组温度 > 单体温度 > 系统温度。电池三维层级关系构建的结果,说明了循环容量衰减和循环温度两方面的层级间构效关系,为锰酸锂动力电池体系循环老化过程研究提供参考。     

Directly connected series coupled HTPEM fuel cell stacks to a Li-ion battery DC bus for a fuel cell electrical vehicle

The work presented in this paper examines the use of pure hydrogen fuelled high temperature polymer electrolyte membrane (HTPEM) fuel cell stacks in an electrical car, charging a Li-ion battery pack. The car is equipped with two branches of two series coupled 1 kW fuel cell stacks which are connected directly parallel to the battery pack during operation. This enables efficient charging of the batteries for increased driving range. With no power electronics used, the fuel cell stacks follow the battery pack voltage, and charge the batteries passively. This saves the electrical and economical losses related to these components and their added system complexity. The new car battery pack consists of 23 Li-ion battery cells and the charging and discharging are monitored by a battery management system (BMS) which ensures safe operating conditions for the batteries. The direct connection of the fuel cell stacks to the batteries can only be made if the stacks are carefully dimensioned to the battery voltage. The experimental results of stationary fuel cell charging are presented, showing stable and efficient operation.