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Engineering topics

Xu, Ying

Publications and source records attributed to Xu, Ying.

Liquid electrolytes for low-temperature lithium batteries: main limitations, current advances, and future perspectives

Lithium-ion batteries (LIBs) can now be used in almost all modern electronic devices and electric vehicles. However, as the range of applications increases, the challenges increase as well, especially at very low temperatures. Many individual processes could result in capacity loss of LIBs at low temperatures; however, most of them are associated with the liquid electrolyte inside the battery. In this review, we first discuss the main limitations in developing liquid electrolytes used in low-temperature LIBs, and then we summarize the current advances in low-temperature electrolytes, including lithium salts, solvents, additives, and new strategies. Finally, we present some perspectives on the current state of low-temperature electrolytes for LIBs, outlining the most promising research areas in this field. In conclusion, this review will provide useful insights into the design of cryogenic electrolytes and the path forward to the widespread use of LIBs in cryogenic environments.

25 ENERGY STORAGE↗

Distributed Secondary Control of Grid-Forming Inverters and AC Microgrids: Impacts of Voltage Feedback Choices

In this paper, the operational choices in distributed secondary control are examined, and their impacts on grid-forming (GFM) inverters and grid operation are investigated. In particular, the effects of feedback voltage choices, either average voltage feedback (AVF) or terminal voltage feedback (TVF), are studied with respect to reactive power sharing, voltage regulation, and grid-forming operation during black start. The secondary control used is a subgradient-based distributed cooperative control, and it provides the voltage, angle, and frequency references to the GFM inverters and their primary tracking controls. The overall control architecture employs multi-rate sampling such that the secondary control is slower than the primary control. The operational choices and their control performance are illustrated using a four-GFM-inverter microgrid in MATLAB/SIMULINK. Furthermore, the results show the effectiveness of the secondary controller, and several conclusions are drawn on the voltage feedback signals as the design choices.

24 POWER TRANSMISSION AND DISTRIBUTION↗

Enhancing thermal conductivity and toughness of cellulose nanofibril/boron nitride nanosheet composites

Generally, the thermal conductivity (TC) of composite based on cellulose nanofibrils (CNF) is improved by adding thermal conductive filler, which inevitably leads to the loss of its mechanical properties. Here, in this work, it is the first to simultaneously improve the toughness and TC of CNF/boron nitride nanosheets (BNNS) composite from the perspective of thermal conductive filler addition and CNF crystal change. The hydrophilic-modified BNNSs were successfully prepared by xylose-assisted ball-milling prior to adding into CNF. Compared with that of CNF film (1.34 W/(m·K)), the in-plane TC of CNF/BNNS composite (12.68 W/(m·K)) increased significantly by 846 % with loading 30 % BNNS. Afterwards, both toughness (8.0 MJ·m -3 , increased ~250 %) and TC (14.7 W/(m·K), increased ~16 %) of CNF/BNNS composite were further enhanced significantly by mercerization with 12.5 % NaOH solution. The simultaneously improvement of toughness and TC is unprecedented in related studies, which contributes to the effective preparation of thermal management materials.

36 MATERIALS SCIENCE↗

Preparation, Properties, and Application of Lignocellulosic-Based Fluorescent Carbon Dots

We report that carbon dots (CDs) are a relatively new type of fluorescent carbon material with excellent performance and widespread application. As the most readily available and widely distributed biomass resource, lignocellulosics are a renewable bioresource with great potential. Research into the preparation of CDs with lignocellulose (LC-CDs) has become the focus of numerous researchers. Compared with other carbon sources, lignocellulose is low cost, rich in structural variety, exhibits excellent biocompatibility, and the structures of CDs prepared by lignin, cellulose, and hemicellulose are similar. This Review summarized research progress in the preparation of CDs from lignocellulosics in recent years and reviewed traditional and new preparation methods, physical and chemical properties, optical properties, and applications of LC-CDs, providing guidance for the formation and improvement of LC-CDs. In addition, the challenges of synthesizing LC-CDs were also highlighted, including the interaction of different lignocellulose components on the formation of LC-CDs and the nucleation and growth mechanism of LC-CDs; from this, current trends and opportunities of LC-CDs were examined, and some research methods for future research were put forward.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Assessment of the driving factors of CO 2 mitigation costs of household biogas systems in China: A LMDI decomposition with cost analysis model

China has been placing a substantial focus on biogas for reducing energy consumption and carbon dioxide (CO 2 ) emissions. The operation mode of biogas systems may make the CO 2 reduction target over-optimistic. There is limited research to investigate the influential factors that may be causing the gap between the actual and theoretical CO 2 reduction costs of biogas systems in China. In this research, by using field survey data of 209 biogas users and 489 non-biogas users from 19 villages in 2015, the gap between actual and theoretical unit CO 2 reduction cost is quantified at approximately 156 USD/t CO 2 . By employing the Logarithmic Mean Divisia Index I (LMDI) model, it is found that both the cost effect (48%) and the reduction effect (52%) contribute to the unit CO 2 reduction cost gap. Furthermore, four influential factors–household labor, accessibility to the energy resource, acceptance of biogas technology, and subsidy–significantly narrow the gap between actual and theoretical CO 2 reduction costs, while the levelized subsidy contributes to widening the gap. On average, biogas systems should be operated for at least four years and the substitution rate should be more than 67% in order to keep the gap between actual and theoretical CO 2 reduction costs under 50%.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗