Large Format Lithium Ion Battery Research Articles

Emerging electrochemical energy conversion and storage technologies.

Electrochemical cells and systems play a key role in a wide range of industry sectors. These devices are critical enabling technologies for renewable energy; energy management, conservation, and storage; pollution control/monitoring; and greenhouse gas reduction. A large number of electrochemical energy technologies have been developed in the past. These systems continue to be optimized in terms of cost, life time, and performance, leading to their continued expansion into existing and emerging market sectors. The more established technologies such as deep-cycle batteries and sensors are being joined by emerging technologies such as fuel cells, large format lithium-ion batteries, electrochemical reactors; ion transport membranes and supercapacitors. This growing demand (multi billion dollars) for electrochemical energy systems along with the increasing maturity of a number of technologies is having a significant effect on the global research and development effort which is increasing in both in size and depth. A number of new technologies, which will have substantial impact on the environment and the way we produce and utilize energy, are under development. This paper presents an overview of several emerging electrochemical energy technologies along with a discussion some of the key technical challenges.

Characterization of large format lithium ion battery exposed to extremely high temperature

This paper provides a study on the characterizations of large format lithium ion battery cells exposed to extreme high temperature but without thermal runaway. A unique test is set up: an extended volume-accelerating rate calorimetry (EV-ARC) test is terminated at a specific temperature before thermal runaway happens in the battery. The battery was cooled down after an EV-ARC test with early termination. The performances of the battery before and after the EV-ARC test are investigated in detail. The results show that (a) the melting point of the separator dictates the reusability of the 25 Ah NCM battery after a near-runaway event. The battery cannot be reused after being heated to 140 °C or higher because of the exponential rise in ohmic resistance; (b) a battery can lose up to 20% of its capacity after being heated to 120 °C just one time; (c) if a battery is cycled after a thermal event, its lost capacity may be recovered partially. Furthermore, the fading and recovery mechanisms are analyzed by incremental capacity analysis (ICA) and a prognostic/mechanistic model. Model analysis confirms that the capacity loss at extremely high temperature is caused by the increase of the resistance, the loss of lithium ion (LLI) at the anode and the loss of active material (LAM) at the cathode.

Effect of Al2O3 Coatings Prepared By RF Sputtering on Polyethylene Separators for High Power Lithium-Ion Batteries

Most of the separators currently used in lithium-ion batteries (LIBs) are based on microporous polyolefin membranes such as polyethylene (PE) and polypropylene (PP). Such separators have excellent mechanical strength and chemical stability, but their thermal properties should be further improved to meet required level of safety for large-format LIBs. In order to achieve this goal, highly heat-resistive components including ceramic coated layers [1] and thermal resistive polymeric layers [2, 3] are introduced onto separator surfaces via dip-coating method, atomic layer deposition, and chemical vapor deposition method.In order to develop a novel and economical process with continuous processing, in this study, we introduced Radio Frequency (RF) sputtering method for fabricating aluminum oxide (Al2O3) ceramic coating layers onto PE separators. Coating thickness of Al2O3 layers was controlled as a function of RF sputtering power and coating time. We also evaluated morphological changes of PE separators in regard to sputtering time by measuring Gurley number, wettability, and ionic conductivity. The unit cells employing coated PE separators revealed similar level of cell performance compared to those of the unit cells employing bare PE separators. We believe that the improved wetting ability of ceramic coating layers successfully compensates pore-blocking effect. On the other hand, we verified that heat resistance of Al2O3 coated PE separators was remarkably improved out of a short sputtering time.

Enhancing the estimation accuracy in low state-of-charge area: A novel onboard battery model through surface state of charge determination

In order to predict the battery remaining discharge energy in electric vehicles, an accurate onboard battery model is needed for the terminal voltage and state of charge (SOC) estimation in the whole SOC range. However, the commonly-used equivalent circuit model (ECM) provides limited accuracy in low-SOC area, which hinders the full use of battery remaining energy. To improve the low-SOC-area performance, this paper presents an extended equivalent circuit model (EECM) based on single-particle electrochemical model. In EECM, the solid-phase diffusion process is represented by the SOC difference within the electrode particle, and the terminal voltage is determined by the surface SOC (SOCsurf) representing the lithium concentration at the particle surface. Based on a large-format lithium-ion battery, the voltage estimation performance of ECM and EECM is compared in the entire SOC range (0–100%) under different load profiles, and the genetic algorithm is implemented in model parameterization. Results imply that the EECM could reduce the voltage error by more than 50% in low-SOC area. The SOC estimation accuracy is then discussed employing the extended Kalman filter, and the EECM also exhibits significant advantage. As a result, the EECM is very potential for real-time applications to enhance the voltage and SOC estimation precision especially for low-SOC cases.

Application of a New Co-Polyimide Binder Material to Improved High-Temperature Performance for Lithium-Ion Batteries

Lithium-ion batteries (LIBs) have been widely used for mobile IT devices and various electric vehicles (xEVs). Especially, since large-format LIBs are operated in the severe environments like -30 or 60 oC, their electrochemical performances and safety should be secured for at least 10 years. Recently, Yoon et al. reported that the degradation was closely related to the contact loss at the electrode/current collector interface and between active material particles1. Thus, the dimensional stability of electrode should be maintained even at high temperatures.In this study, the effects of a thermally stable co-polyimide-based polymeric binder on the performance of a cathode electrode are investigated. The introduction of co-polyimide (P84) into a conventional polymeric binder system based on polyvinylidene fluoride (PVdF) enhances the cycle performance under high temperature conditions (60 oC). Because of the inherent mechanical and thermal stabilities of the co polyimide, P84 retains outstanding adhesive/cohesive strength within the electrode composite, as well as between the electrode composite and the aluminium current collector. These findings are further supported by electrochemical impedance spectroscopic analysis, scanning electron microscope, and studies using a Surface and Interfacial Cutting Analysis System (SAICAS®) 2.

Effect of thermal contact resistances on fast charging of large format lithium ion batteries

A two dimensional electrochemical thermal model is developed on the cross-plane of a laminate stack plate pouch lithium ion battery to study the thermal performance of large format batteries. The effect of thermal contact resistance is taken into consideration, and is found to greatly increase the maximum temperature and temperature gradient of the battery. The resulting large temperature gradient would induce in-cell non-uniformity of charging-discharging current and state of health. Simply increasing the cooling intensity is inadequate to reduce the maximum temperature and narrow down the temperature difference due to the poor cross-plane thermal conductivity. Pulse charging protocol does not help to mitigate the temperature difference on the bias of same total charging time, because of larger time-averaged heat generation rate than constant current charging. Suggestions on battery geometry optimizations for both prismatic/pouch battery and cylindrical battery are proposed to reduce the maximum temperature and mitigate the temperature gradient within the lithium ion battery.

Comparison and validation of methods for estimating heat generation rate of large-format lithium-ion batteries

The heat generation rate of a large-format 25 Ah lithium-ion battery is studied through estimating each term of the Bernardi model. The term for the reversible heat is estimated from the entropy coefficient and compared with the result from the calorimetric method. The term for the irreversible heat is estimated from the intermittent current method, the V–I characteristics method and a newly developed energy method. Using the obtained heat generation rates, the average cell temperature rise under 1C charge/discharge is calculated and validated against the results measured in an accelerating rate calorimeter (ARC). It is found that the intermittent current method with an appropriate interval and the V–I characteristics method using a pouch cell yield close agreement, while the energy method is less accurate. A number of techniques are found to be effective in circumventing the difficulties encountered in estimating the heat generation rate for large-format lithium-ion batteries. A pouch cell, using the same electrode as the 25 Ah cell but with much reduced capacity (288 mAh), is employed to avoid the significant temperature rise in the V–I characteristics method. The first-order inertial system is utilized to correct the delay in the surface temperature rise relative to the internal heat generation. Twelve thermocouples are used to account for the temperature distribution.

Three dimensional thermal-, electrical-, and electrochemical-coupled model for cylindrical wound large format lithium-ion batteries

A numerical model for cylindrical wound lithium-ion cells, which resolves thermal, electrical and electrochemical coupled physics, is presented in this paper. Using the Multi-Scale Multi-Domain (MSMD) model framework, the wound potential-pair continuum (WPPC) model is developed as a cell domain submodel to solve heat and electron transfer across the length scale of cell dimension. By defining the cell composite as a wound continuum, the WPPC model can evaluate layer-to-layer differences in electrical potential along current collectors, and electric current in the winding direction to investigate the effects of thermal and electrical configurations of a cell design, such as number and location of tabs, on performance and life of a cylindrical cell. In this study, 20-Ah large-format cylindrical cell simulations are conducted using the WPPC model with the number of electrical tabs as a control parameter to investigate how macroscopic design for electrical current transport affects microscopic electrochemical processes and apparent electrical and thermal output.

Batteries Rockwood expands production of lithium carbonate in Chile

Rockwood Holdings will spend $140 million to build a lithium carbonate plant in Chile to meet rising demand for lithium compounds used in lithium-ion batteries. The 20,000-metric-ton-per-year facility will be built at Rockwood’s site at La Negra, near the port of Antofagasta in northern Chile. Along with an expansion program in the U.S., the new plant will bring Rockwood’s lithium carbonate capacity to 50,000 metric tons by the end of 2013. “The accelerating increase in the demand for lithium—especially high-purity lithium compounds required for the production of large-format lithium-ion batteries for electric vehicles of the future—is making it necessary for us to substantially increase production capacity,” says Rockwood CEO Seifi Ghasemi. Rockwood obtains lithium carbonate from underground brine pools in a desert region in northern Chile called the Salar de Atacama. The carbonate is converted into lithium hydroxide and derivative compounds for use in batteries and other applications. In addition ...

전 전기자동차용 리튬이온 이차전지 기술동향

온실가스배출억제와 수입원유저감을 위하여 전 전기자동차의 도입이 활발하게 추진되고 있다. 이의 항속거리 연장을 위한 리튬이온 이차전지 소재와 공정개발 등의 연구개발 동향, 그리고 양산체제 구축 중에 있는 리튬이온 이차전지 메이커의 계획도 조사하였다. 완성차메이커와는 수평분업적인 협력관계가 형성되고 있음을 볼 수 있었다. The production capacity of EV models should be sufficient to achieve the goal of one million EVs by 2015. Large-Format lithium-ion battery are expected to find a prominent role as ideal electrochemical storage systems in traction power train for sustainable vehicles such as all-electric vehicles. This review focuses first on the present status of production lithium-ion battery technology and cooperative relations of between battery and EV makers, then on its near future development.

Large-format lithium-ion batteries for electric power storage

We have been developing lithium-ion batteries for electric power storage and have chosen cell chemistries having a high energy density and long life. The cell chemistry consisted of a positive electrode containing a lithium–manganese spinel or a mixture of it with a layered-manganese-based material, and a negative electrode containing a hard carbon. The 8 Ah-class cells consisting of these cell chemistries showed that their extrapolated lives were long enough to withstand a cycling load for 10 years of use. A comparison of the cycle life data with the storage life data suggested the possibility to separate the capacity fading caused only by the storage and that only by the cycling, which is expected to be the basis of a prediction method for the calendar life. However, much work still needs to be done to achieve it. We also manufactured two types of 100 Ah-class cells as an experiment based on the results for the 8 Ah-class cells. They showed specific energies of 100 Wh kg −1 and 106 Wh kg −1.

Three Dimensional Thermal and Electrochemical Model for Spirally Wound Large Format Lithium-Ion Batteries

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