General Motors Company, commonly known as GM, is an American multinational corporation headquartered in Detroit, Michigan, that designs, manufactures, markets and distributes vehicles and vehicle parts and sells financial services. General Motors produces vehicles in 37 countries under thirteen brands: Alpheon, Chevrolet, Buick, GMC, Cadillac, Holden, HSV, Opel, Vauxhall, Wuling, Baojun, Jie Fang, UzDaewoo. General Motors holds a 20% stake in IMM, and a 77% stake in GM Korea. It also has a number of joint-ventures, including Shanghai GM, SAIC-GM-Wuling and FAW-GM in China, GM-AvtoVAZ in Russia, Ghandhara Industries in Pakistan, GM Uzbekistan, General Motors India, General Motors Egypt, and Isuzu Truck South Africa. General Motors employs 212,000 people and does business in more than 120 countries. General Motors is divided into five business segments: GM North America , Opel Group, GM International Operations , GM South America , and GM Financial.General Motors led global vehicle sales for 77 consecutive years from 1931 through 2007, longer than any other automaker, and is currently among the world's largest automakers by vehicle unit sales.General Motors acts in most countries outside the U.S. via wholly owned subsidiaries, but operates in China through 10 joint ventures. GM's OnStar subsidiary provides vehicle safety, security and information services.In 2009, General Motors shed several brands, closing Saturn, Pontiac and Hummer, and emerged from a government-backed Chapter 11 reorganization. In 2010, the reorganized GM made an initial public offering that was one of the world's top 5 largest IPOs to date and returned to profitability later that year. Wikipedia.
Huang X.,General Motors
Journal of Solid State Electrochemistry | Year: 2011
Although separators do not participate in the electrochemical reactions in a lithium-ion (Li-ion) battery, they perform the critical functions of physically separating the positive and negative electrodes while permitting the free flow of lithium ions through the liquid electrolyte that fill in their open porous structure. Separators for liquid electrolyte Li-ion batteries can be classified into porous polymeric membranes, nonwoven mats, and composite separators. Porous membranes are most commonly used due to their relatively low processing cost and good mechanical properties. Although not widely used in Li-ion batteries, nonwoven mats have the potential for low cost and thermally stable separators. Recent composite separators have attracted much attention, however, as they offer excellent thermal stability and wettability by the nonaqueous electrolyte. The present paper (1) presents an overview of separator characterization techniques, (2) reviews existing technologies for producing different types of separators, and (3) discusses directions for future investigation. Research into separator fabrication techniques and chemical modifications, coupled with the numerical modeling, should lead to further improvements in the performance and abuse tolerance as well as cost reduction of Li-ion batteries. © 2010 Springer-Verlag.
Kongkanand A.,General Motors
Journal of Physical Chemistry C | Year: 2011
Understanding the transport of water in a polymer electrolyte membrane, for example, Nafion, is important for optimizing and predicting fuel cell performance. It had been shown that the interfacial resistance could be responsible for a significant portion of the net water transport. In this study, water vapor sorption experiments were done on thin ionomer films (0.03-3 μm thick) by supporting them on a quartz-crystal microbalance (QCM). The high mass resolution of the QCM enables determination of the membrane water content (λ) of the thin films. A slight depression of the water content was observed in very thin films. Meanwhile, study on thin ionomer films minimizes the contribution of internal water diffusion in the film and allows for simplification of the analyses. Interfacial mass-transfer and mechanical relaxation coefficients were determined as a function of water content and temperature. Empirical equations for the mass-transfer coefficient governing absorption and desorption, each as a function of temperature and ionomer water content, were proposed. © 2011 American Chemical Society.
Jorgensen S.W.,General Motors
Current Opinion in Solid State and Materials Science | Year: 2011
Hydrogen storage is an important enabler for fuel cell vehicles. This brief summary provides an overview of the state of the art in the engineering of hydrogen storage tanks over a wide range of technologies as reported in the open literature. Significant progress has been made in hydrogen storage. In many of the alternate storage techniques full scale experimental systems have been built and tested. In some cases these systems can supply hydrogen at required rates under most conditions, but further refinement is needed. At present, compressed gas cylinders and, to a lesser extent, cryogenic tanks remain the storage systems closest to commercialization in vehicles. © 2010 Elsevier Ltd. All rights reserved.
Xie T.,General Motors
Polymer | Year: 2011
Traditional shape memory polymers (SMPs) are those capable of memorizing a temporary shape and recovering to the permanent shape upon heating. Although such a basic concept has been known for half a century, recent progresses have challenged the conventional understanding of the polymer shape memory effect and significantly expanded the practical potential of SMPs. In this article, notable recent advances in the field of SMPs are highlighted. Particular emphasis is placed on how the new developments have changed the conventional view of SMPs, what they mean for practical applications, and where the future opportunities are. © 2011 Elsevier Ltd. All rights reserved.
Huang X.,General Motors
Journal of Power Sources | Year: 2011
A battery separator is placed between the positive and negative electrodes to prevent electric contact of the electrodes while maintaining good ionic flow. The most commonly used separators for lithium-ion batteries are porous polyolefin membranes. However, they generally do not have good dimentional stability at elevated temperatures. In this study, a bilayer separator has been formed directly on an anode. This bilayer separator comprised a ceramic layer and a porous polyvinylidene fluoride (PVDF) layer. Coin cells with this type of separators showed stable cycling performance at room temperature. They also showed significantly improved rate capabilities compared to the reference cell with a conventional polyolefin separator. An oven test has been used to characterize the cells thermal stability. Charged cells were kept in an oven at 150 °C and their voltage drop was recorded. The reference cell with a conventioal separator failed within about 50 min, while no noticeable voltage drop was observed for the cells with the new bilayer separator within the measured 2 h. © 2011 Elsevier B.V.