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8. Cathode materials for high performance lithium-sulfur batteries

Author

Pan, Zhiyong

Abstract

Since the late 20th century, energy crises have acquired worldwide attention. In the last two decades a lot of renewable energy sources have been fully developed and used, including solar energy, wind energy, tide energy and so on. However, the application of these energy sources are hindered by time and space restrictions. For example, solar energy can only be used at day time with relatively clear whether. To make full use of these energy resources, a variety of energy storage devices have been developed. Among them, lithium-ion batteries (LIBs) are the most successful commercialized energy storage devices and are widely used in our daily life, including phones, computers, electric vehicles and so on. However, the energy density of LIBs is hindered by the theoretical specific capacity of the lithium transition metal oxide cathode. Lithium-sulfur batteries (LSBs) with a theoretical specific capacity of 1675 mA h g-1 are regarded as the most promising next generation energy storage devices. But several obstacles, including the low conductivity of S and Li2S, the big volume change of S during charge and discharge and the notorious shuttle effect, stand in the road of commercialization of LSBs. In the thesis, two different strategies have been applied to solve these problems. First, ZIF-67, one kind of metal-organic framework (MOF), was used as a template to synthesis porous carbon frameworks. The carbon frameworks were used as a S host to accommodate the volume change of S and improve the conductivity of the electrode. What's more, the Co centers in ZIF- 67 transferred into cobalt phosphide and cobalt sulphides, based on the detailed experiment condition. Cobalt phosphide and cobalt sulphides with high catalyst activity accelerate the reactions in the electrodes and alleviated the shuttle effect and thus improved the electrochemical performance. Second, sulfurized poly acrylonitrile (SPAN) was used as a source of S for LSBs. The covalent C-S bonds in SPAN alleviated the shuttle effect through reducing the formation of lithium polysulfides. Carbon nanotubes (CNTs) and Se-doping further improved the electrochemical performance of SPAN through improving the conductivity and accelerating the reactions. Samples with different levels of Se-doping were synthesized and characterized to find the best conditions. Meanwhile, the structure of the as-synthesized SPAN samples was characterized by a variety of methods to gain some insight about structure of SPAN, which is a subject of debate among researchers. Through these two strategies, the shuttle effect in LSBs was reduced and the performance of LSBs were improved. A higher specific capacity and a better cyclic stability were achieved. At the same time, a better understanding of the mechanism of LSBs was gained.

Published
2022

22. Completely Independent Spanning Trees in the Line Graphs of Torus Networks

Author

Bian, Qingrong, Cheng, Baolei, Fan, Jianxi, Pan, Zhiyong, Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Woeginger, Gerhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Lai, Yongxuan, editor, Wang, Tian, editor, Jiang, Min, editor, Xu, Guangquan, editor, Liang, Wei, editor, and Castiglione, Aniello, editor

Published
2022
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37. Origin of Reliable High-Power Performances of PbZr0.5Ti0.5O3–Pb(Mn1/3Nb2/3)O3-Based Piezoelectric Ceramics

Author

Tang, Wenbin, Zhao, Xuefeng, Pan, Zhiyong, Zeng, Zhiqin, Wu, Hongdi, Wang, Yiping, Yang, Ying, Wang, Yuequn, Xiang, Guanglei, Wang, Yaojin, Zhang, Shan-Tao, and Yuan, Guoliang

Abstract

High-power piezoelectric ceramics typically operate under severe conditions. This makes the accurate evaluation of their high-power performances through pure quasi-static parameters challenging. The 0.94PbZr0.5Ti0.5O3– 0.06Pb(Mn1/3Nb2/3)O3+ 0.005Fe2O3+ 0.002Sc2O3(PZT-1) ceramic exhibits exceptional and reliable high-power performances at elevated temperatures and under loading conditions. While numerous PZT-based ceramics demonstrate excellent quasi-static parameters, only the PZT-1 ceramic displays superior high-field parameters, such as a low tan δ of 0.97% at 566 V/mm (1 kHz) and a large Qmof 1164 at 50 V/mm (100 kHz). Therefore, the PZT-1 ceramic demonstrates remarkably slow heat generation and the highest surface temperatures are only 41.8 °C at 50 V/mm (100 kHz). Moreover, the PZT-1 ceramic shows a minimal resonance frequency variation of −0.04% in the temperature range of 25–120 °C at 50 V/mm. Consequently, the PZT-1 ceramic maintains a high and reliable vibration velocity of 0.90 m/s at 120 °C for 30 min, and the ceramic cantilever sustains a high amplitude of 7 μm, significantly outperforming other ceramics. This study conclusively demonstrates that high-field parameters, rather than quasi-static parameters, are more effective in accurately estimating the high-power performances of ceramics.

Published
2024
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40. Single Trench Fiber-Enabled High-Power Fiber Laser.

Author

An, Yi, Li, Fengchang, Yang, Huan, Chen, Xiao, Huang, Liangjin, Yan, Zhiping, Jiang, Min, Yang, Baolai, Wang, Peng, Pan, Zhiyong, Jiang, Zongfu, and Zhou, Pu

Subjects
TRENCHES, FIBERS
Abstract

As a novel design of large-mode-area fiber, the single trench fiber (STF) providing high higher-order-mode suppression with a large mode area for the fundamental mode shows potential for high-power and high-brightness applications. However, the output power of STFs has remained relatively low over the past decade. In this paper, we first conducted a design process for STFs and determined the optimal ratio of the fiber structural parameters. Following this ratio, we fabricated an ytterbium-doped STF and demonstrated an all-fiberized fiber amplifier. The system achieved an output power of 2.5 kW with an M2 factor of 1.396. To the best of our knowledge, the power of the STF in this study is approximately three times higher than the previous single-mode power record. [ABSTRACT FROM AUTHOR]

Published
2024
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45. 千瓦级单模激光传输超越百米

Author

Chen Xiao, 陈潇, primary, Huang Shanmin, 黄善旻, additional, Huang Liangjin, 黄良金, additional, Cao Jianing, 曹家宁, additional, Yan Zhiping, 闫志平, additional, Pan Zhiyong, 潘志勇, additional, Zhou Pu, 周朴, additional, and Jiang Zongfu, 姜宗福, additional

Published
2024
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