EIS diagnostics of aged Li-ion batteries

High-power batteries with long cycling life and adequate storage behaviour are needed as energy sources devices for (hybrid) electric vehicles and lithium-ion rechargeable cells are the most promising candidates. In this work, Li-ion cells with a nominal capacity of 10 Ah were studied. Electrochemical impedance spectroscopy (EIS) was used for studying the cycling ageing effect on discharge capacity fade. EIS measurements were conducted in a galvanostatic mode, by means of a Solartron Electrochemical Interface 1286 and a Solartron FRA 1250 controlled by Zplot from Scribner Associates. Scanning frequency ranged from 600 Hz to 0.005 Hz and the ac amplitude was set to 100 mA. An equivalent circuit complex non-linear least squares fitting procedure was used for spectra analyses. Cell charge transfer and film resistances were estimated at several cycle life stages and its evolution on cycle number was analysed. Capacity losses were estimated after 300, 600 and 1200 cycles at C/1 discharge rate and were found to be 5.8, 7.5 and 16.8% of the initial capacity, respectively. EIS data revealed that the major factor responsible for the observed capacity fade was the cell’s charge transfer resistance (Rct) increase following the opposite tendency of the discharge capacity values with cycle number. Very little change can be attributed to film resistances as a result of ageing by cycling. The SEI layer thickness appeared to increase from 0 to 300 cycles remaining almost constant up to 1200 cycles. The effect of a high storage temperature on the performance of the sealed commercial batteries was evaluated by means of discharge capacity measurements and impedance behaviour. The thermal ageing conditions were applied over time and the results were interpreted taking into account the cell’s state of charge (SOC). Before storage at 45 oC, in an open circuit state, cells were fully charged (100% SOC). At defined intervals, cells were cooled to ambient temperature and capacities were determined by a discharge step. As the cells aged up to 25 weeks at 45 oC, the C/1 capacity slowly fades, at first, with a capacity retention of about 95% after 16 weeks of storage. However, the value of discharge capacity loss reached 10.9%, after 25 weeks (Fig. 1). Impedance data were fit to an equivalent circuit with a high frequency arc associated to the SEI film resistance (R sei) and a second arc at medium frequencies to Rct

Penetration of hydrogen technologies: study on the environmental impact of road transport in Portugal

Road traffic is one of the transportation sectors with faster growth and also one of the most important emitters of greenhouse gases (GHGs). In this work, an analysis of the environmental benefits resulting from the introduction of hydrogen on road transport in Portugal is made. Impact is analyzed mainly looking at the pollutant emissions provided by road transport at the point of use. Emissions associated to road transport have been estimated using the software COPERT (version 4), since it provides a detailed methodology for each specific pollutant related to the vehicle fleet of a region or country, as well as the driving conditions and fuel consumption. Passenger cars, light duty vehicles and public transport buses are the vehicles categories in which the hydrogen technology is foreseen. The hydrogen penetration rates (moderate and high) are extracted from the European Project HYWAYS. Two trends are then considered, which give penetration rates of 40.0 % and 74.5 % in 2050 for the moderate and high scenarios respectively

Fuel cell and hydrogen storage development for a wheel chair

In this paper are presented, the recent advances of a demonstration project that focuses on the implementation of a hybrid system for a wheel chair incorporating a fuel cell and a metal hydride hydrogen storage system. Advantages regarding weight reduction and greater autonomy are emphasized, apart from the use of clean energy and the drastic reduction in charging time, when compared with the system before conversion

How to map potential mesovoid shallow substratum (MSS) habitats? A case study in colluvial MSS

Understanding habitat extension that limits species distribution is a crucial tool for management and conservation, in which habitat mapping plays a pivotal role. The mesovoid shallow substratum (MSS) is a type of shallow subterranean habitat with an important conservation value for invertebrate communities, functioning as climatic/reproductive refuge, biogeographic corridor and/or permanent habitat. Methodologies to map the mesovoid shallow substratum (MSS) are currently lacking. We propose a novel method for colluvial MSS habitat mapping, combining geographic information systems, geological maps, and geological knowledge on the habitat genesis. We tested and validated the efficiency of the method using the Arrábida karst area (Portugal) as a model. The method allowed the remote detection of MSS habitats suitable for invertebrate communities ex situ within the study area, and enabled the estimation of habitat extent. The faunal communities sampled in the selected location were dominated by arthropods, especially insects, showcasing the efficacy of this mapping method to detect suitable MSS habitats. The use of this method considerably reduces the in situ scouting area, providing a more efficient way of locating these habitats. The MSS is protected under EU legislation concerning floral communities and geological features, completely neglecting its faunal communities. This method also allows to estimate potential MSS habitat extension in several lithologies, facilitating the implementation of invertebrate prospections, and the establishment of more effective conservation measures.info:eu-repo/semantics/publishedVersio

Intensity modulated radiotherapy for localized prostate cancer: rigid compliance to dose-volume constraints as a warranty of acceptable toxicity?

BACKGROUND: To report the toxicity after intensity modulated radiotherapy (IMRT) for patients with localized prostate cancer, as a sole treatment or after radical prostatectomy. METHODS: Between August 2001 and December 2003, 132 patients with prostate cancer were treated with IMRT and 125 were evaluable to acute and late toxicity analysis, after a minimum follow-up time of one year. Clinical and treatment data, including normal tissue dose-volume histogram (DVH) constraints, were reviewed. Gastro-intestinal (GI) and genito-urinary (GU) signs and symptoms were evaluated according to the Radiation Therapy Oncology Group (RTOG) toxicity scales. Median prescribed dose was 76 Gy. Median follow-up time was of 26.1 months. RESULTS: From the 125 patients, 73 (58.4%) presented acute Grade 1 or Grade 2 GI and 97 (77.2%) presented acute Grade 1 or Grade 2 GU toxicity. Grade 3 GI acute toxicity occurred in only 2 patients (1.6%) and Grade 3 GU acute toxicity in only 3 patients (2.4%). Regarding Grade 1 and 2 late toxicity, 26 patients (20.8%) and 21 patients (16.8%) presented GI and GU toxicity, respectively. Grade 2 GI late toxicity occurred in 6 patients (4.8%) and Grade 2 GU late toxicity in 4 patients (3.2%). None patient presented any Grade 3 or higher late toxicity. Non-conformity to DVH constraints occurred in only 11.2% of treatment plans. On univariate analysis, no significant risk factor was identified for Grade 2 GI late toxicity, but mean dose delivered to the PTV was associated to higher Grade 2 GU late toxicity (p = 0.042). CONCLUSION: IMRT is a well tolerable technique for routine treatment of localized prostate cancer, with short and medium-term acceptable toxicity profiles. According to the data presented here, rigid compliance to DHV constraints might prevent higher incidences of normal tissue complication