Browsing by Author "Li, Jiani"
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Item Economic and labor market responses to demographic changes(University of Delaware, 2022) Li, JianiChina is turning into an aging society and there is a growing percentage of older people in this country. Currently, the country has the world’s largest older population (persons who are over or equal to the age of 65) and the United Nations also projects that there will be 366 million older population by the year 2050. It seems that the country is experiencing population aging on an unprecedented scale. ☐ Generally speaking, population aging is assumed to have an adverse impact on economic growth since it will reduce the proportion of the population that is economically active. In addition, given the fact that institutional care and community-based care are far from satisfying the needs of older people, families have been the primary sources of care for the older population. The working-age labor force need to provide caregiving to their older parents and may choose to live near them, and thus it may affect the labor market outcomes of their working-age children. ☐ For China, there is little empirical evidence exploring the magnitude of the population aging effect on economic growth or the labor market. In this study, I construct a city panel dataset where the data was observed every 5 years in 2000 to 2015. Specifically, I use the predicted variation in the rate of population aging across Chinese cities to estimate the impact of population aging on city level GDP per capita and labor market outcomes. I find that a 10% increase in the extent of population aging (extent is measured by the fraction of the population aged over or equal to 65 years) would decrease GDP per capita by 2.42 %. On the other hand, a 10% increase in the extent of population aging would increase the average wage by 1.67%. There is heterogeneity in the effect across different periods and across different regions — with the effect more significant in less-developed cities. When decomposing the effect of population aging on economic growth into labor participation and labor productivity, I find that the effect of age composition mainly operates through the decrease in the labor-to-population ratio. When decomposing the effect by sector, I find there is a significant adverse effect on the secondary sector output, but there is no clear trend of how population aging would affect the development path of a city.Item Electrochemical Modeling of Fast Charging in Batteries(Advanced Energy Materials, 2024-04-18) Duan, Xudong; Hu, Dayong; Chen, Weiheng; Li, Jiani; Wang, Lubing; Sun, Shuguo; Xu, JunThe acceleration of fast charging capabilities has emerged as a pivotal objective within the realms of the battery, electric vehicle, and energy storage sectors. However, the classical electrochemical models are not able to describe voltages of the cell (Ucell), anode (Ua), and cathode (Uc) at high C-rates. Herein, Ucell, Ua,, and Uc are experimentally obtained under various C-rates (0.1–2C) and identified the charge transfer resistance of the cathode (RCT,c) as the primary rate-limiting factor. Thus, the anode is established as a multi-scale coupling model with Fick's law and phase separation model applied, to discuss their effect on Ua and Li-ion concentration prediction. 2D reconstruction structures for the cathode is established with RCT,c effect considered. Finally, the Ua, Uc, and Ucell are successfully predicted at different C-rates. Results propose an accurate and versatile electrochemical model and highlight the importance of considering limiting factors in electrochemical modeling for fast charging.Item Investigation of the lithium plating triggering criterion in graphite electrodes(Journal of Materials Chemistry A: materials for energy and sustainability, 2024-04-16) Li, Jiani; Wang, Lubing; Xu, JunLithium plating is considered an undesirable side reaction because it can induce capacity fading and pose safety concerns in Li-ion batteries. The timely detection of lithium plating onset is crucial for both mechanistic investigations and ensuring the safe and durable operation of batteries. In this study, discharging tests were conducted by varying the set capacity in graphite/Li cells to induce lithium plating on the graphite electrode. Based on a comprehensive analysis of the voltage curves and the morphological characterization of disassembled cells, the inflection point on the differential voltage curve during the discharging process was identified as the precise onset time of lithium plating. Electrochemical models were developed to further elucidate the mechanisms governing the onset of lithium plating. Compared with the model based on the potential criterion, the model employing the concentration criterion demonstrated enhanced precision in predicting lithium plating, particularly under high C rates. Based on the model with the concentration criterion, the discharging protocol was optimized parametrically to achieve high discharging efficiency and restrain lithium plating. This nuanced understanding contributes to determining the onset of lithium plating more accurately, thereby facilitating a more robust battery design and durable yet fast charging protocols.