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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

High-performance spherical LiVPO4F/C cathode enabled by facile spray pyrolysis

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Science China(Technological Sciences) 2020年第12期63卷 2729-2734页

作者： DING XiaoBo ZHOU YongMao YAN GuoChun LI JiaYi wang jiexi School of Metallurgy and Environment Central South UniversityChangsha 410083China Middle School Attached to Central South University Changsha 410083China State Key Laboratory for Powder Metallurgy Central South UniversityChangsha 410083China

LiVPO4F suffers problems of difficulty in synthesis and poor conductivity. To solve these,herein sub-micro spherical LiVPO4F/C is synthesized from a highly-reactive hollow VPO4/C sphere that is derived from a facile and fast spray pyrolysis for the first time. Uniform carbon coating layer with a thickness of 5–8 nm is observed on the surface of the particles,helping to improve the electronic conductivity,suppress the particle growth and protect the particles from corrosion by the electrolyte. The particles are shaped as fine sub-micro spheres,which are beneficial for shortening the distance for Li+ transport. Rietveld refinement for the X-ray diffraction pattern of as-prepared sample shows high-purity triclinic LiVPO4F with an enlarged lattice volume,enabling faster Li+ transport in the prepared material. Accordingly,the resulted LiVPO4F/C demonstrates superior electrochemical properties,delivering 135.4,91.1 mA hg-1 at 1,40 C respectively,and remaining the capacity of 93.3 mA hg-1 after 500 cycles at 20 C with the retention of 95.0%. The method introduced here provides an efficient way to address the serious problems of preparing high-purity Li VPO4F with good conductivity.

关键词： lithium ion battery cathode material spray pyrolysis LiVPO4F carbon coating

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

Grain size regulation for balancing cycle performance and rate capability of LiNi_(0.9)Co_(0.055)Mn_(0.045)O_(2) single crystal nickel-rich cathode materials

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Journal of Energy Chemistry 2022年第2期31卷 681-687页

作者： Jiapei wang Xibin Lu Yingchao Zhang Jiahui Zhou jiexi wang Shengming Xu Institute of Nuclear and New Energy Technology Tsinghua UniversityBeijing 100084China Hunan ShanShanEnergy Technology Co. LTDChangsha 410006HunanChina State Key Laboratory for Powder Metallurgy&School of Metallurgy and Environment Central South UniversityChangsha 410083HunanChina Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education Tsinghua UniversityBeijing 100084China Beijing Key Lab of Fine Ceramics Tsinghua UniversityBeijing 100084China

It is challenging to balance the cyclability and rate capability of single crystal nickel-rich cathode materials(Ni>0.8).Multicomponent oxides by spray pyrolysis shows potential as highly-reactive precursors to synthesize single crystal nickel-rich cathode at lower temperature,yet Ni^(2+)will severely inhibit particle growth when Ni content exceeds ***,lithium nitrate(LiNO_(3))with low melting point and strong oxidation is introduced as collaborate lithium salts for fabrication of well-dispersed submicron and micron single crystal LiNi_(0.9)Co_(0.055)Mn_(0.045)O_(2)(NCM90)cathode without extra unit *** changing amount of LiNO_(3),particle size regulation is realized and cation disorder can be *** as-prepared material with optimal content of 4 wt%LiNO_(3)(NCM90-4 LN)displays the most appropriate particle size(1μm)with approximately stoichiometric structure,and presents better kinetics characterization of lithium-ion diffusion(15%higher than NCM90)and good electrochemical performance with specific discharge capacity of 220.6 and 173.8 mAh g^(-1) at 0.1 C and 10 C at room temperature,*** work broadens the conventional research methodology of size regulation for single crystal Ni-rich cathode materials and is indispensable for the development of designing principal of nickel-rich cathode materials for lithium-ion batteries.

关键词： Single crystal LiNi_(0.9)Co_(0.055)Mn_(0.045)O_(2) Spray pyrolysis Lithium nitrate Lithium-ion batteries

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

Immobilizing polysulfide jointly via chemical absorbing and physical blocking in polytungstates-embedded carbon nanofibers

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Journal of Energy Chemistry 2021年第6期30卷 206-211,I0006页

作者： Yanmei Nie Lei Tan Guangchao Li Sanghao Li Jun Yan jiexi wang College of Chemistry and Chemical Engineering&School of Metallurgy and Environment Central South UniversityChangsha 410083HunanChina Hunan Provincial Key Laboratory of Chemical Power Sources Central South UniversityChangsha 410083HunanChina Engineering Research Center of the Ministry of Education for Advanced Battery Materials Central South UniversityChangsha 410083HunanChina

Lithium-sulfur(Li-S) battery is regarded as one of the most fascinating candidates for energy storage due to its dominant advantage of high energy ***,the shuttling effect of soluble polysulfides and low electrical conductivity of sulfur and Li_(2)S still hinder its *** this work,high electrical-conductive carbon nanofibers(CNFs) with uniformly embedded polytungstates(HPW@CNFs) are proposed for advanced Li-S batteries.H_(3)PW_(12)O_(40)(HPW) is a kind of molecular nano-sized metal cluster which contains rich Lewis acid/base sites that can stabilize polysulfide effectively through chemical bonding,while CNFs play the role of physical barriers for polysulfides and transmission channel for *** HPW@CNFs/S cathode shows an ultra-stable cycling performance with extremely small decay rate of 0.015% per cycle over 400 cycles at 0.5 C.

关键词： Lithium-sulfur batteries Polysulfides Polyoxometalates Carbon nanofibers

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)

A Lithium-free Anode Toward Stable All-solid-state Lithium Metal Batteries

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材料导报 2020年第13期34卷 13001-13002页

作者：谭磊王接喜 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

Lithium(Li)metal has the lowest standard electrochemical redox potential and very high theoretical specific capacity,making it the most potential anode material for rechargeable batteries[1].The use of Li metal in organic liquid electrolyte faces many issues in terms of battery performance and safety[2].Solid-electrolyte in-terphase(SEI)formation during the uneven Li deposition will continuously consume Li and dry up the ***-state electrolytes are superior to liquid counterparts in terms of battery safety due to their nonflammable nature[3].

关键词： battery electrolyte state

Facile and scalable fabrication of lithiophilic Cu_(x)O enables stable lithium metal anode

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Journal of Energy Chemistry 2022年第12期75卷 285-292,I0007页

作者： Yanmei Nie Xiangyu Dai jiexi wang Zhengfang Qian Zhixing wang Huajun Guo Guochun Yan Dongting Jiang Renheng wang Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province College of Physics and Optoelectronic EngineeringShenzhen UniversityShenzhen 518060GuangdongChina School of Metallurgy and Environment Central South UniversityChangsha 410083HunanChina

Equipped with highest-energy density anode,lithium metal batteries are of great interests for the nextgeneration energy storage ***,the existing problems like uneven Li deposition,large volume expansion and short cycling lifespan severely retard the implementation of Li metal ***,we report an in-situ formed Cu_(x)O nanofiber network synthesized by facile and scalable calcination process and employ as stable lithium metal *** CuO/Cu_(2)O ratio in the lithiophilic Cu_(x)O network can be adjusted through an optimal annealing time,thus guiding the homogeneous distribution of Li atoms and regulating the repeated plating/stripping *** a result,Li@Cu_(x)O 3D scaffold displays an ultralow overpotential of 7.7 mV,long cycling life for more than 1000 h in symmetric cell,and exceptional stability for LiFePO_(4)//Li full *** work provides guidelines for the design and fabrication of lithiophilic 3D matrixes and advances the practical use of lithium metal batteries.

关键词： Lithium metal batteries 3D collectors Lithiophilic modification