J Loss Prev Process Ind

National Institute for Occupational Safety and Health (NIOSH) researchers continue to study the potential for lithium and lithium-ion battery thermal runaway from an internal short circuit in equipment for use in underground coal mines. Researchers conducted cell crush tests using a plastic wedge within a 20-L explosion-containment chamber filled with 6.5% CH4-air to simulate the mining hazard. The present work extends earlier findings to include a study of LiFePO4 cells crushed while under charge, prismatic form factor LiCoO2 cells, primary spiral-wound constructed LiMnO2 cells, and crush speed influence on thermal runaway susceptibility. The plastic wedge crush was a more severe test than the flat plate crush with a prismatic format cell. Test results indicate that prismatic Saft MP 174565 LiCoO2 and primary spiral-wound Saft FRIWO M52EX LiMnO2 cells pose a CH4-air ignition hazard from internal short circuit. Under specified test conditions, A123 systems ANR26650M1A LiFePO4 cylindrical cells produced no chamber ignitions while under a charge of up to 5 A. Common spiral-wound cell separators are too thin to meet intrinsic safety standards provisions for distance through solid insulation, suggesting that a hard internal short circuit within these cells should be considered for intrinsic safety evaluation purposes, even as a non-countable fault. Observed flames from a LiMnO2 spiral-wound cell after a chamber ignition within an inert atmosphere indicate a sustained exothermic reaction within the cell. The influence of crush speed on ignitions under specified test conditions was not statistically significant.CC999999/Intramural CDC HHS/United States2015-06-30T00:00:00Z26139958PMC448598

Acoustic and X-ray Chacterisation of Lithium-Ion Battery Failure

Lithium-ion batteries have become synonymous with modern consumer electronics and potentially, are the cornerstone to development of integrated electrified infrastructure that can support a clean and renewable national energy grid. Despite the widespread applications due to the favourable performance parameters, recent events have elevated the safety concerns associated with lithium-ion batteries. However, there is great difficulty in rapid diagnostic analysis outside specialised laboratories which can hinder the review of functional safety- and novel energy dense- materials for lithium-ion energy storage. The dynamic evolution of internal architectures and novel active materials across multiple length scales are investigated in this thesis; with in-situ and operando acoustic spectroscopy (AS) via ultrasonic time of flight (ToF) probing, high speed synchrotron X-ray imaging, computed tomography and fractional thermal runaway calorimetry. The identification of characteristic precursor events such as gas-induced delamination in degradation mechanisms before eventual failure by AS; is correlated with X-ray imaging and post-mortem computed tomography (CT), highlighting the potential for battery management systems. Mitigation and prevention of failure with plasticized current collectors and thermally stable cellulose separators was also investigated at multiple length scales, with the transient mechanical structure compared with their commercial counterparts in cylindrical cells. Further work investigating the robustness of acoustic spectroscopy and polymer current collectors were applied to pure silicon nanowire negative electrodes. The studies reported in this thesis assess novel materials in lithium-ion batteries, and the potential impact of the work is highlighted. Development of AS via ToF probing offers another unique and field deployable insight allowing more complete and comprehensive understanding of batteries as they continue to evolve in complexity. Lithium-ion failure characterisation techniques and literature have evolved and provided insights into the function of polymer current collectors in different cell formats and chemistries. Findings presented in this thesis are anticipated to augment future inherently safer battery design and characterisation of lithium-ion energy storage thermal runaway

Experimental and Theoretical Analysis of Safety-Degradation Interaction in Lithium-Ion Cells

Lithium ion batteries are quite ubiquitous in terms of their market spread. They represent an extremely compact energy storage device. In addition to making them a lucrative choice for a diverse set of applications, this high energy density and larger terminal voltage also make them quite dangerous if not handled properly. In extreme events, they can also catch fire. To ensure continuous and safe operation, cell manufacturers specify a voltage window of operation. This voltage window describes the lowest discharge voltage and highest charge voltage. Intuitively speaking, the cell stability should not be specified just in terms of one voltage value. Rather, it should be a function of cell temperature as well as charging current. In order to gain insights into the cell operation during and after overcharge, commercial 18650 cells were used for electrochemical cycling. Three major sets of tests were performed on these to answer the following questions: 1) How do Li-ion cells behave if the electrochemical window is manipulated? 2) How does the charging rate affect the overcharge behavior of these cells? 3) Finally, is there a way to track changes occurring during each state of overcharge and perhaps, elucidate the reactions in the cell contributing to overcharge? The results showed that even if the upper voltage limit of Li-ion cells is extended and a higher capacity is gained, the cycle life of the cell diminishes considerably. Secondly, as expected, the charging rate is found to have a significant effect, leading to the hypothesis that overcharge of Li-ion cell is not solely dependent on the upper voltage limit, but also on the charging rate (current). Based on destructive physical analysis (DPA) and electrochemical impedance spectroscopy measurements, the resistance from the cell separator was found to be a leading presence during overcharge of the cell. Finally, based on overcharge tests and the supporting DPA analysis, it was concurred that overcharge is a cathode dependent process as opposed to the popular belief of anodic dependence

Electric Vehicles in New Zealand - Policy, Regulation and Technical Standards for Emerging Vehicle Technology

The need for a technical standard for the conversion of Internal Combustion Engine (ICE) vehicles to electric drive has been identified by government regulators in New Zealand (NZ). The aim of this project was to review the technical and inspection requirements that would allow Electric Vehicle (EV) conversions of passenger vehicles of gross weight < 3500 kg (Class MA), to be safely designed, built, sold, and operated in NZ. A detailed description of the spectrum of EV technology is given. A literature review of NZ and international transport regulations and technical standards has shown many requirements affecting EVs. A risk analysis showed that most EV technological risks related to electrical, battery and braking safety are controlled by implementing a reduction in risk event likelihood, rather than a reduction in risk event severity. This indicates that risk controls need to be reliable in order to be effective. A detailed review of EV electrical systems, Lithium Ion (Li-ion) battery systems and regenerative braking technology is also carried out. With the use of battery chemistries and designs which minimise the risk of failures, coupled with adequate safeguards in the form of redundant protection and well designed component management systems, EV converters can achieve safe and high performance conversions

Phenotypic spectrum of patients with congenital disorders of the hypothalamo-pituitary axis.

Mutations within the cascade of pituitary transcription factors that play a crucial role in its development and differentiation have improved our understanding of variable hypopituitarism in children. The diagnosis of hypopituitarism is problematic as it is dependent on a series of endocrine tests varying in sensitivity and specificity, compounded by evolving hormonal deficiencies. In order to test the hypothesis that human phenotypes are determined by the neuroanatomy which is further influenced by the position of the abnormal gene within the pituitary developmental cascade, clinical, biochemical, magnetic resonance MR imaging and molecular data were retrospectively analysed in subgroups from a cohort of 825 patients with variable hypothalamo-pituitary H-P abnormalities. The major aims were to determine abnormalities on MR imaging that help predict the spectrum of hypopituitarism, to assess if genotype determined phenotype and to ascertain the optimum test for diagnosis of hormone deficiency. Results showed good structure-function relationships within the H-P axis. Anterior pituitary hypoplasia and an undescended posterior pituitary were 6.7 and 33.1 times more prevalent in patients with hypopituitarism as compared with those without. These abnormalities were also significantly associated with endocrinopathies in patients with optic nerve hypoplasia. Within patients with hypopituitarism, midline forebrain defects MFD and pituitary stalk abnormalities were found to be significantly associated with combined pituitary hormone deficiency as opposed to isolated GH deficiency. GH was critical for early postnatal growth, which was also influenced by other pituitary hormones and MFD. Regular evaluation of serum thyroxine concentration best revealed TSH deficiency, as the TRH test was normal in 23% of patients with central hypothyroidism limiting its role as a diagnostic test. A combination of the short Synacthen test and 0800-hour serum Cortisol concentrations represented the optimal method of investigation for ACTH deficiency. The LHRH test in infancy needs careful interpretation, as responses were gender-specific with significantly exaggerated serum FSH concentrations in females. There was a poor genotype-phenotype correlation, particularly in patients with mutations in HESX1, PROP and SOX3, both within and between pedigrees, indicating a role for other genetic or environmental factors on phenotypic expression