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Green Energy & Environment 2023年第4期8卷 1071-1080页

作者： Chengwei Ma Xinyu Zhang Chengcai liu Yuanxing Zhang Yuanshen Wang ling liu Zhikun Zhao Borong Wu Daobin Mu beijing Key Laboratory of Environmental Science and Engineering School of Materials Science and EngineeringBeijing Institute of TechnologyBeijing100081China collaborative innovation Center of Electric Vehicles in beijing Beijing100081China

lithium metal batteries represent promising candidates for high-energy-density batteries, however, many challenges must still be overcome,e.g., interface instability and dendrite growth. In this work, nano silica aerogel was employed to generate a hybrid film with high lithium ion conductivity(0.6 mS cm^(-1)at room temperature) via an in situ crosslinking reaction. TOF-SIMS profile analysis has revealed conversion mechanism of hybrid film to li–Si alloy/li F biphasic interface layer, suggesting that the li–Si alloy and li F-rich interface layer promoted rapid li+transport and shielded the li anodes from corrosive reactions with electrolyte-derived products. When coupled with nickel-cobalt-manganese-based cathodes, the batteries achieve outstanding capacity retention over 1000 cycles at 1 C. Additionally the developed film coated on li enabled high coulombic efficiency(99.5%) after long-term cycling when coupled with S cathodes. Overall, the results presented herein confirm an effective strategy for the development of high-energy batteries.

关键词： lithium metal batteries Nano silica aerogel In situ crosslinking Biphasic interface layer li–Si alloy

Effects of tooth bending damage on the leakage performance and rotordynamic coefficients of labyrinth seals

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Chinese Journal of Aeronautics 2020年第4期33卷 1206-1217页

作者： Yaoxing CHEN Zhigang li Jun li Xin YAN institute of Turbomachinery Xi’an Jiaotong UniversityXi'an 710049China collaborative innovation Center for Advanced Aero-Engine Beijing 100083China

Tooth bending damage resulting from an intense impact by the rotor sometimes occurs in the transient *** investigate the influence of after-damage clearance and tooth bending length on the leakage performance and rotordynamic coefficients of labyrinth seals,three tooth bending damages were taken into consideration,including the unbent tooth damage(abbreviated as Unbent),the partial tooth bending damage(abbreviated as Pbent)and the complete tooth bending damage(abbreviated as Cbent).The transient CFD solution was utilized to calculate the leakage flow rates and rotordynamic coefficients of labyrinth seals with clearances of 0.3,0.4,0.5,0.6 mm for three tooth bending *** obtained result shows that the Unbent tooth damage leaks least while the Pbent tooth bending damage leaks most,and an increase of 6.1%for Cbent tooth bending damage and an increase of 19.4%for Pbent tooth bending damage are discovered at the tooth clearance of 0.6 mm in comparison with the Unbent tooth *** to the Unbent tooth damage,the effective damping for Pbent tooth bending damage and Cbent tooth bending damage is lower and drops by 9.7%–33.6%and 8.5%–22.6%respectively at the tooth clearance of 0.6 mm,suggesting that Pbent tooth bending damage or Cbent tooth bending damage tends to weaken the seal stability when compared to the Unbent tooth damage.

关键词： Labyrinth seal Leakage Rotor forward whirl Rotordynamic coefficients Tooth bending damage Vena contracta effect

Effect of bristle pack position on the rotordynamic characteristics of brush-labyrinth seals at various operating conditions

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Chinese Journal of Aeronautics 2020年第4期33卷 1192-1205页

作者： Yuanqiao ZHANG Jun li Zhigang li Xin YAN institute of Turbomachinery Xi'an Jiaotong UniversityXi'an 710049China collaborative innovation Center for Advanced Aero-Engine Beijing 100083China

Over the last few decades,the research on the effect of bristle pack position on the rotordynamic characteristics of the brush-labyrinth seals is not *** this end,two kinds of brush-labyrinth seals for the bristle pack element installed upstream of the labyrinth teeth named BSU and installed downstream of the labyrinth teeth called BSD were used to investigate the effect of bristle pack position on the rotordynamic characteristics of the brush-labyrinth *** the numerical model combining the porous medium model and the whirling rotor method,the rotordynamic characteristics of the BSU and BSD at various operating conditions including four kinds of pressure ratios,five kinds of inlet preswirl speeds and four kinds of rotor spinning speeds were *** obtained results show that the effects of operating conditions on rotordynamic coefficients for the different seal configurations are *** direct stiffness,cross-coupled stiffness and direct damping of the BSU are lower than those of the *** rotordynamic coefficients of the BSU are more insensitive to the operating conditions *** the perspective of the seal stability,the BSU is a better brush-labyrinth seal configuration at high pressure ratio,high positive preswirl or high rotor spinning speed *** in the case of low pressure ratio,low positive preswirl or low rotor spinning speed conditions,the BSD is a better choice.

关键词： Bristle pack position Brush-labyrinth seal Porous medium Rotordynamic characteristics Whirling rotor method

Facile synthesis of li3V2（PO4）3/C cathode material for lithium-ion battery via freeze-drying

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Journal of Energy Chemistry 2019年第5期28卷 159-165页

作者： Shuainan Guo Ying Bai Zhenfeng Geng Feng Wu Chuan Wu beijing Key Laboratory of Environmental Science and Engineering School of Materials Science & EngineeringBeijing Institute of TechnologyBeijing 100081China collaborative innovation Center of Electric Vehicles in beijing Beijing 100081China

In this work, we report a facile route for the synthesis of li3V2(PO4)3/C cathode material via freezedrying and then calcination. The effect of calcination temperature on the electrochemical properties of the li3V2(PO4)3/C is also investigated. When used as a lithium-ion battery cathode, the optimized li3V2(PO4)3/C (LVP-800) through calcination at 800 ℃ exhibits a high initial charge and discharge capacity. The excellent electrochemical performance of LVP-800 is attributed to the good crystallinity and uniform morphology of the electrode material. In addition, the residual carbon can also improve the conductivity and buffer the volume expansion during the li-ion extraction/reinsertion. Meanwhile, charge compensation also plays an important role in excellent electrochemical performance.

关键词： li3V2(PO4)3/C Freeze-drying Charge compensation lithium-ion battery

Effects of swirl brake axial arrangement on the leakage performance and rotor stability of labyrinth seals

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Chinese Journal of Aeronautics 2021年第1期34卷 22-31页

作者： Yaoxing CHEN Zhigang li Jun li Xin YAN institute of Turbomachinery Xi'an Jiaotong UniversityXi'an 710049China collaborative innovation Center of Advanced Aero-Engine Beijing 100083China

Swirl brakes are usually introduced at the seal entrance in industry to improve the seal stability,especially for labyrinth seals suffering low seal clearance and high inlet preswirl ***,how to arrange swirl brakes at the seal entrance to obtain better seal stability retains unknown,such as the axial distance between the brake trailing edge and the first *** this end,the effects of the distance between brakes and the first tooth on the leakage flow rate and seal rotordynamic coefficients were numerically investigated at typical inlet preswirl ratios of 0.45 and0.8,and the predicted results were in comparison with the results for no-brake *** obtained results disclose that the brake configuration arranged against the first tooth produces lower circumferential velocity in the downstream of the brakes as a result of the larger counterclockwise vortex moving from the brake trailing edge to the brake leading edge when compared to the brake configuration away from the first ***,the dropped circumferential velocity in the downstream of brakes will cause larger pressure fluctuation in the circumferential direction and thus generates larger tangential force to restrain the rotor forward *** the other hand,the effective damping is further increased when the distance between brakes and the first tooth decreases to zero,that is,the crossover frequency is even disappeared at the inlet preswirl ratio of 0.45 and successfully drops from 69.9 Hz to 32.7 Hz at the preswirl ratio of 0.8.

关键词： Circumferential velocity Labyrinth seal Leakage Numerical analysis Rotor stability Swirl brake

CFD–DEM–CVD multi-physical field coupling model for simulating particle coating process in spout bed

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Particuology 2019年第1期17卷 67-78页

作者： Malin liu Meng Chen Tianjin li Yaping Tang Rongzheng liu Youlin Shao Bing liu Jiaxing Chang institute of Nuclear and New Energy Technology Collaborative Innovation Center of Advanced Nuclear Energy TechnologyTsinghua UniversityBeijing 100084China

Particle coating is a very important step in many industrial production processes as the particle coating layers may fix surfaces with unique advantages. Given the limitation and disadvantages of the existing simulation methods, a coupled CFD–DEM–CVD multi-physical field model for particle-coating simulations has been established taking into account the velocity field, temperature field, concentration field, and deposition model. In this model, gas behavior and chemical reactions are simulated in the CFD frame based on the conservation laws of mass, momentum, and energy. The particle behavior is simulated in the DEM frame based on the gas–solid interphase force model and contact force model. The deposition behavior is simulated in the CVD frame based on the particle movement–adhesion–deposition model. The coupled model can be implemented in Fluent-EDEM software with their user definition function and application programming interface. The particle coating process involving the pyrolysis of acetylene was investigated, and the effect of bed temperature and inlet gas velocity on deposition rate and coating efficiency were investigated based on the proposed model with adjustable deposition coefficients. Both the average deposition layer mass and the average deposition layer thickness were found to be proportional to the elapsed time and increased at the rate of about 1.05 × 10^-2 mg/s and 3.45 × 10^-4 mm/s, respectively, setting the inlet gas velocity to 11 m/s and bed temperature to 1680 K. A higher temperature and larger inlet gas velocity lead to a larger deposition rate, but the coating efficiency decreases because of limits imposed by the chemical reaction. At a bed temperature of 1280 K, the average deposition rate is 7.40 × 10?3 mg/s when the inlet gas velocity is set to 11 m/s, which is about double the deposition rate when the inlet gas velocity is set as 5 m/s. The proposed model can provide some guidance for the operating conditions and parameters design of t

关键词： Particle coating process CFD–DEM–CVD Multi-physical field Chemical vapor deposition model Multiscale simulation

Organosilicon-group-derived silica-ionogel electrolyte for lithium ion batteries

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Rare Metals 2018年第6期37卷 504-509页

作者： YueJiao li Cui Guo LuShan Yue WenJie Qu Nan Chen YuJuan Dai RenJie Chen Feng Wu School of Material Science and Engineering Beijjing Institute of Technology Beijing 100081 China collaborative innovation Center of Electric Vehicles in beijing Beijing 100081 China beijing Jinghua Eduction School Beijing 100081 China

In order to avoid leakage problem caused by liquid electrolyte, a new ionogel electrolyte was developed by in situ immobilizing organosilicon-functionalized ionic liquid within a nanoporous silica matrix. The ionic liquid evenly coats on the surface of porous silica and fills in the silica framework pores with no strong chemical interaction. The ionogel electrolyte has the dual advantages of a silica solid support and a wide electrochemical stability window of ionic liquid （4.87 V vs. li^＋/li）. The half-cells assembled with this electrolyte and liFePO4 electrode have excellent performance at room temperature and 60 ℃. The li/SiO2-IGE/liFePO4 cell displays a discharge capacity of 129.1 mAh·g^-1 after 200 charge/discharge cycles at room temperature.

关键词： Ionogel electrolyte SiO2 Organosilicon group Ionic liquid

Improved Efficiency Test Method for the Motor Controller with SiC MOSFETs

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Journal of beijing institute of Technology 2020年第3期29卷 294-302页

作者： Wei Wang Qiang Song Yiting li Mukhtiar Ahmad School of Mechanical Engineering Beijing Institute of TechnologyBeijing 100081China collaborative innovation Center for Electric Vehicles Beijing 100081China

The traditional measurement method was inaccurate to evaluate the motor controller efficiency,which the measurement efficiency value could be more than 100%in practical testing *** deal with this issue,an improved electrical measurement method for the motor controller efficiency is proposed in this paper,which is established by analyzing the power loss distribution and phase currents of the motor *** is demonstrated that the SiC MOSFET chips are the main power loss devices in the motor controller,accounting for more than 93.1%of the total power *** accuracy of the proposed method is compared with the traditional method in *** shows that the test error of the efficiency obtained by the traditional method fluctuates on a large scale,which varied from 0.094%to 1.911%.Compared with the traditional method,the test error of the proposed method appears to be less than 0.083%,which provides significant guidance for the motor controller efficiency test and design.

关键词： electrical measurement method motor controller efficiency power loss distribution SiC MOSFET

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Tailoring fluorine-rich solid electrolyte interphase to boost high efficiency and long cycling stability of lithium metal batteries

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Science China Chemistry 2023年第7期66卷 2121-2129页

作者： Tianyang Xue Ji Qian Xingming Guo Yi Chen Kaixin Yu Tianyang Yu Yao li li li Feng Wu Renjie Chen beijing Key Laboratory of Environmental Science and Engineering School of Materials Science and EngineeringBeijing Institute of TechnologyBeijing 100081China institute of Advanced Technology Beijing Institute of TechnologyJinan 250300China collaborative innovation Center of Electric Vehicles in beijing Beijing 100081China

lithium metal batteries(LMBs)are regarded as the most promising next-generation battery system due to their high energy ***,li dendrite growth and low Coulombic efficiency(CE)of li metal anodes limit their *** solid electrolyte interphase(SEI)is an extremely effective method to solve these problems and using electrolyte additives to regulate the SEI is one of the most effective ***,we study the feasibility of trans-difluoroethylene carbonate(DFEC)used as the solvent additive in conventional ether electrolyte,which has excellent anti-reduction stability against li *** result shows that a li/Cu half-cell with the modified electrolyte can be steadily cycled for 300 cycles with an average CE of 97.41%at the current density of 0.5 m A cm^(-2)and with 97.1%for 140 cycles at 1 m A cm^(-2).Besides,the li/LFP full cell with the modified electrolyte displays an improved capacity retention of 94.55%after 520 cycles with an average CE of 99.74%at 1 *** contrast,the capacity retention of 56.2%and CE of 99.15%is obtained for the cell with pure ether *** SEM images show that the DFEC enables dense li deposition,and the FTIR and XPS spectra confirm the formation of li Frich SEI with the *** work demonstrates the feasibility of using DFEC as the solvent additive in ether electrolyte to construct li F-rich SEI,and it will provide important insight in developing high-performance electrolytes for LMBs.

关键词： lithium metal batteries ether electrolyte trans-difluoroethylene carbonate liF-rich SEI dense li deposition

A gradient solid electrolyte interphase with high li+conductivity induced by bisfluoroacetamide additive for stable lithium metal batteries

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Nano Research 2023年第6期16卷 8425-8432页

作者： Zhaoyang Sun Ziyue Wen Yi Chen Yue Ma Jinxiang Zhang Yuejiao li li li Renjie Chen beijing Key Laboratory of Environmental Science and Engineering School of Material Science&EngineeringBeijing Institute of TechnologyBeijing 100081China institute of Advanced Technology Beijing Institute of TechnologyJinan 250300China collaborative innovation Center of Electric Vehicles in beijing Beijing 100081China

Stable li metal anodes have become the driving factor for high-energy-density battery ***,uncontrolled growth of li dendrite hinders the application of rechargeable li metal batteries(LMBs).Here,a multifunctional electrolyte additive bisfluoroacetamide(BFA)was proposed to facilitate high-performance *** uniform and dense deposition of li^(+) was achieved due to the reduced nucleation and plateau overpotential by the addition of ***,X-ray photoelectron spectroscopy(XPS)tests reveal a gradient solid electrolyte interface(SEI)structure on the li metal *** voltammetry(CV)curves at different sweep speeds prove the formation of pseudocapacitance at the electrode-electrolyte interface,which accelerates the li+transport rate and protects the electrode *** low activation energy also indicates the ability of rapid li^(+) transportation in electrolyte ***,the li||li symmetric cells with 1.0 wt.%BFA electrolyte exhibit good cycling performance at 0.5 mA·cm^(−2)for over 2000 h,and li||liNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)(NCM622)full cells maintain a high capacity for 200 cycles at 1 C rate.

关键词： electrolytes additives solid electrolyte interphase li dendrites li metal batteries