Browsing by Author "Gao, Xiang"
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Item Carbon Binder Domain Inhomogeneity in Silicon-Monoxide/Graphite Composite Anode by 2D Multiphysics Modeling(Advanced Science, 2024-05-22) Gao, Xiang; Xu, JunThe Carbon-binder domain (CBD) plays a pivotal role in the performance of lithium-ion battery electrodes. The heterogeneous distribution of CBD across the electrode has garnered significant attention. However, a thorough understanding of how this CBD inhomogeneity affects anode performance remains a crucial pursuit, especially when considering the inherent material variations present in the SiO/Graphite (SiO/Gr) composite anode. In this study, an electro-chemo-mechanical model is established that provides a detailed geometric description of the particles. This model allows to quantitatively uncover the effects of CBD inhomogeneity on the fundamental behaviors of the SiO/Gr composite anode. The findings indicate that reducing the proportion of CBD in the upper domain (near the anode surface) compared to the lower domain (near the current collector) positively influences electrochemical performance, particularly in terms of capacity and Li plating. However, such an arrangement introduces potential risks of mechanical failures, and it is recommended to incorporate a higher proportion of CBD alongside the SiO particles. Finally, an anode design with a lower CBD proportion in the upper domain exhibits superior rate performance. This study represents a pioneering modeling exploration of CBD inhomogeneity, offering a promising multiphysics model with significant potential for informing advanced battery design considerations.Item Sea-ice loss accelerates carbon cycling and enhances seasonal extremes of acidification in the Arctic Chukchi Sea(Limnology and Oceanography Letters, 2024-02-05) Zhang, Yixing; Wu, Yingxu; Cai, Wei-Jun; Yi, Xiangqi; Gao, Xiang; Bi, Haibo; Zhuang, Yanpei; Chen, Liqi; Qi, DiThe Chukchi Sea shelf (CSS) is a highly productive region in the Arctic Ocean and it is highly efficient for absorbing atmospheric carbon dioxide and exporting and retaining carbon in the deep sea. However, with global warming, the carbon retention time in CSS may decrease, leading to less efficient carbon export. Here, we investigate the seasonal variability of carbonate chemistry in CSS using three sets of late- vs. early-summer reoccupations of the same transect. Our findings demonstrate substantially increased and rapid degradation of biologically produced organic matter and therefore acidification over time in the southern CSS due to earlier sea-ice retreat, resulting in significantly shorter carbon retention time. In sharp contrast, no increased degradation has been observed in the northern CSS where photosynthesis has just commenced. In the future, climate change would further diminish the carbon export capacity and exacerbate seasonal acidification not only within CSS but also across other polar coastal oceans. Scientific Significance Statement The Arctic Chukchi Sea shelf (CSS) is a prominent site for the biological drawdown of atmospheric carbon dioxide, which can subsequently be transported to the deep sea in the Arctic Ocean. The efficiency of carbon export is influenced by seasonal sea-ice formation and retreat: longer period of sea-ice opening results in shorter carbon retention time and reduced carbon export due to rapid recycling of organic matter. However, this process is poorly understood due to lack of observations. Here, we present three sets of late- vs. early-summer reoccupations along the same transect in the CSS. We unveil distinct spatial patterns of carbonate chemistry and subsurface acidification between the southern CSS and northern CSS. In the sCSS, degradation of biologically produced organic matter has occurred rapidly and caused subsurface acidification since early summer due to earlier sea-ice retreat; however, no such phenomenon is observed in the northern region. As Arctic warming continues in the future, these conditions are expected to persist, further diminishing carbon export capacity and exacerbating seasonal acidification.Item The impact of sea ice melt on the evolution of surface pCO2 in a polar ocean basin(Frontiers in Marine Science, 2024-02-07) Yang, Wei; Zhao, Yu; Wu, Yingxu; Chen, Zijie; Gao, Xiang; Lin, Hongmei; Ouyang, Zhangxian; Cai, Weijun; Chen, Liqi; Qi, DiThe strong CO2 sink in Arctic Ocean plays a significant role in the global carbon budget. As a high-latitude oceanic ecosystem, the features of sea surface pCO2 and air-sea CO2 flux are significantly influenced by sea ice melt; however, our understanding of pCO2 evolution during sea ice melt remains limited. In this study, we investigate the dynamics of pCO2 during the progression of sea ice melt in the western Arctic Ocean based on data from two cruises conducted in 2010 and 2012. Our findings reveal substantial spatiotemporal variability in surface pCO2 on the Chukchi Sea shelf and Canada Basin, with a boundary along the shelf breaks at depths of 250-500 m isobaths. On the Chukchi Sea shelf, strong biological consumption dominates pCO2 variability. Moreover, in Canada Basin, the pCO2 dynamics are modulated by various processes. During the active sea ice melt stage before sea ice concentration decreases to 15%, biological production through photosynthetic processes and dilution of ice melt water lead to a reduction in DIC concentration and subsequent decline in pCO2. Further, these effects are counteracted by the air-sea CO2 exchange at the sea surface which tends to increase seawater DIC and subsequently elevate surface pCO2. Compared to the pCO2 reduction resulting from biological production and dilution effects, the contribution of air-sea CO2 exchange is significantly lower. The combined effects of these factors have a significant impact on reducing pCO2 during this stage. Conversely, during the post sea ice melt stage, an increase in pCO2 resulting from high temperatures and air-sea CO2 exchange outweighs its decrease caused by biological production. Their combined effects result in a prevailing increase in sea surface pCO2. We argue that enhanced air-sea CO2 uptake under high wind speeds also contributes to the high sea surface pCO2 observed in 2012, during both active sea ice melt stage and post sea ice melt stage. The present study reports, for the first time, the carbonate dynamics and pCO2 controlling processes during the active sea ice melt stage. These findings have implications for accurate estimation of air-sea CO2 fluxes and improved modeling simulations within the Arctic Ocean. Highlights ● The decrease in DIC resulting from biological production and dilution of ice melt water tends to reduce pCO2 during the active sea ice melt stage in Canada Basin, although it is counteracted by CO2 uptake at the air-sea interface. ● The increase in pCO2 resulting from high temperatures and air-sea CO2 exchange outweighs its decrease caused by biological production, leading to elevated sea surface pCO2 during the post sea ice melt stage in Canada Basin. ● The enhanced air-sea CO2 uptake under high wind speeds also contributes to the high sea surface pCO2 observed in 2012, during both active sea ice melt stage and post sea ice melt stage.