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Bifunctional Li6CoO4 serving as prelithiation reagent and pseudocapacitive electrode for lithium ion capacitors

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Journal of Energy Chemistry 2020年第8期29卷 38-45,I0002页

作者： Yuntao Guo Xinhai Li zhixing wang Huajun Guo Jiexi wang School of Metallurgy and Environment Central South UniversityChangsha 410083HunanChina

Lithium ion capacitors(LICs)have been widely used as energy storage devices due to their high energy density and high power *** LICs,pre-lithiation of negative electrode is *** this work,we employ a bifunctional Li6CoO4(LCO)as cathodic pre-lithiation reagent to improve the electrochemical performance of *** synthesized LCO exhibited high first charge specific capacity of 721 mAh g-1and extremely low initial coulombic efficiency of 3.19%,providing sufficient Li+ for the pre-lithiation of negative electrode in the first ***,Li6–xCoOy is generated from LCO during the first charge process,which exhibits pseudocapacitive property and contributes to capacity in form of surface capacitance during subsequent cycles,increasing the capacity of capacitive positive *** the appropriate amounts of addition to the positive side in LICs,this bifunctional prelithiation reagent LCO shows significantly improved the electrochemical performance with the energy density of 78.5 Wh kg-1after 300 cycles between 2.0 and 4.2 V at 250 mA g-1.

关键词： Lithium ion capacitor Prelithiation reagent Pseudocapacitive electrode Li6CoO4

Improving the electrochemical performance of LiMn_2O_4/graphite batteries using LiF additive during fabrication

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Rare Metals 2011年第2期30卷 120-125页

作者： LIU Yunjian GUO Huajun LI Xinhai wang zhixing School of Material Science and Engineering Jiangsu University Zhenjiang 212013 China School of Metallurgical Science and Engineering Central South University Changsha 410083 China

LiMn2O4/graphite batteries using LiF additive were fabricated and their electrochemical performance including discharge, cycling and storage performances were tested and compared with LiF-free LiMnEO4/graphite batteries. The LiMnEO4/graphite battery with LiF added shows better capacity （107.5 mAh/g）, cycling performance （capacity retention ratio of 93% after 100 cycles）, and capacity recovery ratio （98.1%） than the LiF-free battery. The improvement in electrochemical performance of the LiF-added LiMnEO4/graphite battery was due to the fact that LiF can restrain the dissolution of Mn from the spinel LiMn2O4 cathode into the electrolyte, leading to a smaller resistance and polariza- tion.

关键词： lithium batteries lithium fluoride additives electrochemical properties

Synthesis and electrochemical properties of Al-doped LiVPO_4F cathode materials for lithium-ion batteries

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Rare Metals 2007年第5期26卷 445-449页

作者： ZHONG Shengkui YIN Zhoulan wang zhixing CHEN Qiyuan College of Chemistry and Chemical Engineering Central South University Changsha 410083 China Department of Materials and Chemistry Guilin University of Technology Guilin 541004 China School of Metallurgical Science and Engineering Central South University Changsha 410083 China

Al-doped LiVPO4F cathode materials LiAlxV1-xPO4F were prepared by two-step reactions based on a car-bothermal reduction （CTR） process. The properties of the Al-doped LiVPO4F were investigated by X-ray diffraction （XRD）,scanning electron microscopy （SEM）,and electrochemical measurements. XRD studies show that the Al-doped LiVPO4F has the same triclinic structure （space group p-↑1 ） as the undoped LiVPO4F. The SEM images exhibit that the particle size of Al-doped LiVPO4F is smaller than that of the undoped LiVPO4F and that the smallest particle size is only about 1 μm. The Al-doped LiVPO4F was evaluated as a cathode material for secondary lithium batteries,and exhibited an improved reversibility and cycleability,which may be attributed to the addition of Al^3＋ ion by stabilizing the triclinic structure.

关键词： lithium-ion batteries cathode material LiVPO4F Al-doping carbothermal reduction method cyclic voltammetry (CV)

Spray pyrolysis synthesis of nickel-rich layered cathodes LiNi_(1-2x)Co_xMn_xO_2(x = 0.075, 0.05, 0.025) for lithium-ion batteries

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Journal of Energy Chemistry 2018年第2期27卷 447-450页

作者： Yan Li Xinhai Li zhixing wang Huajun Guo Jiexi wang School of Metallurgy and Environment Central South University

In this study we report a series of nickel-rich layered cathodes LiNi1-2xCoxMnxO2（x = 0.075, 0.05,0.025） prepared from chlorides solution via ultrasonic spray pyrolysis. SEM images illustrate that the samples are submicron-sized particles and the particle sizes increase with the increase of Ni ***0.85Co0.075Mn0.075O2 delivers a discharge capacity of 174.9 mAh g-1 with holding 93% reversible capacity at 1 C after 80 cycles, and can maintain a discharge capacity of 175.3 mAh g-1 at 5 C rate. With increasing Ni content, the initial specific capacity increases while the cycling and rate performance degrades in some extent. These satisfying results demonstrate that spray pyrolysis is a powerful and efficient synthesis technology for producing Ni-rich layered cathode（Ni content 〉 80%）.

关键词： Lithium-ion batteries Nickel-rich layered cathode Ultrasonic spray pyrolysis Powder technology Composite materials

Electrospinning-Enabled Si/C Nanofibers with Dual Modification as Anode Materials for High-Performance Lithium-Ion Batteries

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Acta Metallurgica Sinica(English Letters) 2021年第3期34卷 329-336页

作者： Yi Yan Huajun Guo zhixing wang Xinhai Li Guochun Yan Jiexi wang School of Metallurgy and Environment Central South UniversityChangsha 410083China Engineering Research Center of the Ministry of Education for Advanced Battery Materials Central South UniversityChangsha 410083China

In this work,silicon@reduced graphene oxide/pyrolytic carbon nanofibers(Si@RGO/C NFs)composite with double modified layer is prepared through electrospinning,stabilization and *** this composite,polyethylene oxide-polypropylene oxide-polyethylene oxide(P123,a non-ionic surfactant)is introduced as the dispersant,which can make silicon nanoparticles evenly dispersed in electrospinning solution to prevent it from *** modified layer can buffer the volumetric expansion of silicon nanoparticles,prevent direct contact between silicon and electrolyte as well as enhance the electrical ***,carbon fibers synthesized by electrospinning can encapsulate silicon@graphene composite internally to form a double modified *** composite with double modified layer can further alleviate the volume change of silicon nanoparticles and avoid direct contact between silicon and electrolyte to form a stable *** to the above-mentioned merits,the Si@RGO/C NFs composite exhibits excellent cyclic stability and superior rate ***,it maintains a specific capacity of 929 mA h g^(-1)with the retention ratio of 83.1%after 100 cycles at 0.5 A g^(-1)and delivers an outstanding rate capability of 1003 mA h g^(-1)at 2 A g^(-1).

关键词： Lithium-ion batteries Silicon/carbon composite Surface modification Graphene Electrospinning

Numerical Simulation of Droplets Interacting with a Microcolumnar Solid Structure

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Fluid Dynamics & Materials Processing 2023年第6期19卷 1585-1608页

作者： Liang Yang Tianle Xi zhixing wang College of Mechanical Engineering Dalian Jiaotong UniversityDalian116028China

The VOF method is used to simulate the dynamics of a droplet interacting with a structure consisting of an array of microcolumns mounted on a flat *** a specific configuration is intended to mimic the typical properties of lotus leaves,which typically display regularly arranged micron-scale papillary *** setting the initial velocity of the simulated droplet on the basis of practical considerations,an analysis is conducted about the effect of the characteristic size of the microstructure on the apparent contact *** pressure variation in the microstructure caves is also *** simulation results show that the change of the contact angle of the droplet in the quasi-static state is consistent with theoretical calculations and the contact angle in the dynamic state is smaller than that in the quasi-static ***,under dynamic conditions,the pressure fluctuation in the microstructure cave depends essentially on the characteristic size of the microstructure.

关键词： Dynamic behavior mastoid microcolumn contact angle cavitation pressure

The Impact of Key Factors on Flow Characteristics of 14 MW Reverse-Swirl Pulverized Coal Burner

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Journal of Thermal Science 2021年第6期30卷 2214-2222页

作者： JIA Nan NIU Fang LIU Pengzhong wang zhixing wang Naiji ZHOU Jianming China Coal Research Institute Company of Energy Conservation Beijing 100013China State Key Laboratory of High Efficient Mining and Clean Utilization of Coal Resources Beijing 100013China National Energy Technology&Equipment Laboratory of Coal Utilization and Emission Control Beijing 100013China

Reverse-swirl(RS)burner which has been industrialized couples reverses jet and swirl flow for the stabilization of *** Dantec multichannel constant-temperature anemometer,experiments on airflow characteristics were implemented on a 1:2 scaled burner model with different values in terms of reverse primary air(RPA)ratio and swirl inner secondary air(SISA)*** was found that the shape of annular coupled recirculation zone(ACRZ)had stayed symmetrical all the *** RPA ratio was the main factor that had an impact on the values of axial and RMS velocity as well as the radial velocity direction of *** RPA ratio and SISA ratio had a great impact on the area of ACRZ,relative reverse flow rate,mixing between SISA and outer secondary air(OSA)as well as swirling ability of the *** area of ACRZ reached its peak when the RPA ratio was 11.92%or SISA ratio was 17.03%;however,when the RPA ratio and SISA ratio reached 14.86%and 28.41%respectively,the combination of RPA and SISA became relatively favorable;besides,ACRZ area,relative reverse flow and swirling ability became suitable and the mixing between SISA and OSA was relatively *** research was of great practical and theoretical importance to the design and operation of RS burner.

关键词： reverse-swirl burner reverse primary air swirl inner secondary air annular coupled recirculation zone flow characteristics

Free-standing ultrathick LiMn_(2)O_(4)@single-wall carbon nanotubes electrode with high areal capacity

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Journal of Energy Chemistry 2022年第10期31卷 452-459,I0012页

作者： Yuntao Guo Xinhai Li zhixing wang Jiexi wang Huajun Guo Guochun Yan School of Metallurgy and Environment Central South UniversityChangsha 410083HunanChina Engineering Research Center of the Ministry of Education for Advanced Battery Materials Central South UniversityChangsha 410083HunanChina Hunan Provincial Key Laboratory of Nonferrous Value-added Metallurgy Central South UniversityChangsha 410083HunanChina

The ever-increasing demands for advanced lithium-ion batteries with high energy density have greatly stimulated the pursuit of thick electrodes with high active material ***,it is not feasible to prepare thick electrodes with traditional coating methods due to mechanical ***,using single-wall carbon nanotubes(SWCNT)as conductive carbon and binder,free-standing LiMn_(2)O_(4) thick electrodes(F-LMO)with ultrahigh-mass loading up to~190 mg cm^(-2)were prepared by vacuum filtration combined with *** thick electrodes with~30 mg cm^(-2)mass loading achieved a high specific capacity of 106.7 mAh g^(-1)with a good capacity retention of 94%over 50 cycles at 0.5 C,which was superior to the traditional coating electrodes(~20 mg cm^(-2))of 99.3 mAh g^(-1)with 95%because of the enhanced electronic conductivity originated from *** addition,the high active material ratio of 97.5 wt%,near-theoretical reversible capacity,and high mass loading gave ultrathick F-LMO electrodes(600μm)of~190 mg cm^(-2)with a remarkable areal capacity of 20 mAh cm^(-2).Moreover,the concentration polarization that occurred in the thick F-LMO electrodes under high current density was discussed via electrochemical stimulation.

关键词： Thick electrodes Free-standing High areal capacity Concentration polarization

Evolution of the morphology,structural and thermal stability of LiCoO_(2) during overcharge

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Journal of Energy Chemistry 2021年第4期30卷 524-532页

作者： Zhitao E Huajun Guo Guochun Yan Jiexi wang Rukun Feng zhixing wang Xinhai Li School of Metallurgy and Environment Central South UniversityChangsha 410083HunanChina

The overcharge behaviors of 1000 m Ah LiCoO_(2)/graphite pouch cells are systematically investigated through the analysis of morphology,structural and thermal stability of LiCoO_(2) under different state of charge(SOC)of 120%,150%,174%,190%and 220%.The LiCoO_(2) experiences the phase transition from O3 to H1-3 and then O1 together with the grain breakage and boundary slip as evidenced by XRD and SEM analysis respectively,which results in the pronounced Co dissolution after the SOC of 174%.The impedance analysis of the pouch cells and coin cells demonstrates that the main contribution of impedance increase originates from the LiCoO_(2) *** the combined effect of structural collapse,Co dissolution,and electrolyte oxidization,the thermal stability of Li CoO_(2) cathode materials reduces with the progressing of overcharge as revealed by differential scanning calorimetry(DSC)*** hope that this comprehensive understanding can provide meaningful guidance for advancing the overcharge performance of LiCoO_(2)/graphite pouch cells.

关键词： Li-ion batteries Overcharge Stability LiCoO_(2)