Initial stage oxidation corrosion of commercial ferritic stainless steels with different Cr contents at 650 °C for solid oxide fuel cells.

Selecting adequate ferritic stainless steel (FSS) with a high corrosion resistance and a low cost is critical for solid oxide fuel cells (SOFCs) operating at intermediate temperature. In this study, the corrosion behaviors of four commercial FSSs involving TS430, TY441, YG442, and TY445 with a Cr content ranging from 16.18 wt.% to 21.73 wt.% are investigated at 650 °C. The oxidation mass gains, microstructures of surface oxide scale, and electrical conductivities are measured. The effects of grain size as well as doped elements are estimated together with the Cr volatilization. Flaky Cr2O3 particles are formed on TS430 and TY441 dominated by the outward migration of Cr3+. In comparison, a thin and dense layer of chromia is observed on YG442 and TY445. A high Cr content and a uniformly distributed grain size are conducive to the formation of a thin and dense chromia scale on the FSS surface during the initial oxidation process. On the other hand, the addition of Nb, Ti, and Mo weakens the outward diffusion of Cr3+ and reduces the particle size of chromia. After oxidation at 650 °C for 120 h, scattered (Mn, Cr)3O4 spinel particles occur on TS430, YG442, and TY445. TY445 and YG442 exhibit a higher conductivity although all the results of area specific resistance (ASR) are less than 6 mΩ·cm2. Meanwhile, the effect of Cr volatilization is enlarged on the estimation of mass gain at 650 °C compared with even higher temperatures.

Fire boundaries of lithium-ion cell eruption gases caused by thermal runaway.

Lithium-ion batteries are applied in electric vehicles to mitigate climate change. However, their practical applications are impeded by poor safety performance owing mainly to the cell eruption gas (CEG) fire triangle. Here, we report quantitatively the three fire boundaries corresponding to the CEG fire triangle of four types of mainstream cells with the state of charge (SOC) values ranging from 0% to 143% based on 29 thermal runaway tests conducted in an inert atmosphere in open literature. Controlling the SOC and/or selecting a reasonable cell type can alter the minimum CEG and oxygen concentrations required for ignition, thereby changing the probability of a battery fire. The ignition temperature varies greatly according to the type of ignition source type. Temperature and ignition source type play a leading role in the ignition mode. Breaking any fire boundary will stop the ignition of CEG, thus significantly improving the battery safety performance.

In situ observation of thermal-driven degradation and safety concerns of lithiated graphite anode.

Graphite, a robust host for reversible lithium storage, enabled the first commercially viable lithium-ion batteries. However, the thermal degradation pathway and the safety hazards of lithiated graphite remain elusive. Here, solid-electrolyte interphase (SEI) decomposition, lithium leaching, and gas release of the lithiated graphite anode during heating were examined by in situ synchrotron X-ray techniques and in situ mass spectroscopy. The source of flammable gas such as H2 was identified and quantitively analyzed. Also, the existence of highly reactive residual lithium on the graphite surface was identified at high temperatures. Our results emphasized the critical role of the SEI in anode thermal stability and uncovered the potential safety hazards of the flammable gases and leached lithium. The anode thermal degradation mechanism revealed in the present work will stimulate more efforts in the rational design of anodes to enable safe energy storage.

[Analysis of PHEV CO2 Emission Based on China's Grid Structure and Travelling Patterns in Mega Cities].

Spatial-domain changes in the proportion of thermal power in the power grids of China and the duality of PHEV-driven energy have increased the complexity of research on the CO2 emissions of plug-in hybrid electric vehicles (PHEVs). 130000 km of driving data from 50 PHEV vehicles operating in Shanghai is studied to derive methods to evaluate the carbon dioxide emission of PHEV vehicles. The electric drive distance ratio of the PHEV and its influencing factors are analyzed. The effects of the electric range, charging frequency, and power grid composition on the carbon emission intensity of PHEV are analyzed, and the effect of the level of progress for PHEV in 2020 on CO2 emission reductions is forecast. The results of the study show that the daily vehicle kilometers travelled by PHEV passenger cars in China's first-tier cities are mainly concentrated within a range of 50 km, accounting for 70% of total trips. Under the national grid structure in 2016, PHEVs with a driving range of more than 50 km emit at least 15% less carbon dioxide than conventional vehicles. In areas with a high proportion of renewable energy grid structure, PHEV carbon dioxide emissions can be reduced to below 100.0 g·km-1, which is more than 28% lower than that achieved using the national grid structure. Based on the national grid structure and technical level in 2016, increasing the all-electric range (50-100 km) and the charging frequency (0.5 times·d-1 to 2 times·d-1) has no obvious effect on reducing CO2 emissions. The PHEV fuel economy and electricity consumption levels in 2020 could reduce carbon dioxide emissions by 32% compared to those in 2016.