25 results on '"Jiexi Wang"'
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2. Lithium difluorophosphate–modified PEO-based solid-state electrolyte for high-voltage lithium batteries
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Jiaxu Tan, Xinhai Li, Qihou Li, Zhixing Wang, Huajun Guo, Guochun Yan, Jiexi Wang, and Guangchao Li
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General Chemical Engineering ,General Engineering ,General Physics and Astronomy ,General Materials Science - Published
- 2022
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Catalog
3. A scalable dry chemical method for lithium borate coating to improve the performance of LiNi0.90Co0.06Mn0.04O2 cathode material
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Xinxin Tan, Wenjie Peng, Hui Duan, Zhixing Wang, Huajun Guo, Gui Luo, Rongzhong Yuan, Xinhai Li, and Jiexi Wang
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General Chemical Engineering ,General Engineering ,General Physics and Astronomy ,General Materials Science - Published
- 2022
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4. Lowering the operating temperature of PEO-based solid-state lithium batteries via inorganic hybridization
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Zhixing Wang, Huajun Guo, Peng Wenjie, Yuqi Wu, Jiexi Wang, Zhihao Guo, Xinhai Li, Xianwen Wu, Guochun Yan, and Hu Qiyang
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chemistry.chemical_classification ,Materials science ,General Chemical Engineering ,General Engineering ,General Physics and Astronomy ,chemistry.chemical_element ,Electrolyte ,Polymer ,Electrochemistry ,Dissociation (chemistry) ,Crystallinity ,Chemical engineering ,chemistry ,Ionic conductivity ,General Materials Science ,Lithium ,Nanorod - Abstract
Employing the solid polymer electrolyte (SPE) instead of traditional liquid electrolyte is an effective way to develop high safety and high-energy density solid-state lithium batteries. Herein, for the first time, the Ni3B2O3 (NBO) nanorods are incorporated into polyethylene oxide (PEO)-based SPE. Particularly, the optimized NBO-embedded SPE shows a high ionic conductivity of 8.5 × 10−5 S cm−1 at 30 °C, lowering the operating temperature of PEO-based SPE substantially. The corresponding LiFePO4/Li battery demonstrates a high discharge capacity of 154 mAh g−1 after 80 cycles at 0.2 C under 30 °C, with favorable capacity retention of 97.5%. The remarkable properties are attributed to the high ionic conductivity of modified SPE at ambient temperature, which is resulted from the decreased crystallinity and melting transition point, increased movement of PEO chain, and promotion of lithium salt dissociation, as well as the formation of the lithium ion migrating pathway on the interface between PEO and NBO nanorods. more...
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- 2021
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5. Review of silicon-based alloys for lithium-ion battery anodes
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Zhi-yuan Feng, Guochun Yan, Xinhai Li, Zhixing Wang, Peng Wenjie, Jiexi Wang, and Huajun Guo
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Materials science ,Silicon ,Mechanical Engineering ,Alloy ,Metals and Alloys ,chemistry.chemical_element ,engineering.material ,Electrochemistry ,Engineering physics ,Lithium-ion battery ,Anode ,chemistry ,Geochemistry and Petrology ,Mechanics of Materials ,Materials Chemistry ,engineering ,Gravimetric analysis ,Lithium ,Voltage - Abstract
Silicon (Si) is widely considered to be the most attractive candidate anode material for use in next-generation high-energy-density lithium (Li)-ion batteries (LIBs) because it has a high theoretical gravimetric Li storage capacity, relatively low lithiation voltage, and abundant resources. Consequently, massive efforts have been exerted to improve its electrochemical performance. While some progress in this field has been achieved, a number of severe challenges, such as the element’s large volume change during cycling, low intrinsic electronic conductivity, and poor rate capacity, have yet to be solved. Methods to solve these problems have been attempted via the development of nanosized Si materials. Unfortunately, reviews summarizing the work on Si-based alloys are scarce. Herein, the recent progress related to Si-based alloy anode materials is reviewed. The problems associated with Si anodes and the corresponding strategies used to address these problems are first described. Then, the available Si-based alloys are divided into Si/Li-active and inactive systems, and the characteristics of these systems are discussed. Other special systems are also introduced. Finally, perspectives and future outlooks are provided to enable the wider application of Si-alloy anodes to commercial LIBs. more...
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- 2021
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6. Unraveling the role of LiODFB salt as a SEI-forming additive for sodium-ion battery
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Guochun Yan, Zhixing Wang, Jiexi Wang, Qimeng Zhang, Xinhai Li, and Huajun Guo
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Battery (electricity) ,Materials science ,General Chemical Engineering ,General Engineering ,General Physics and Astronomy ,Sodium-ion battery ,chemistry.chemical_element ,02 engineering and technology ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,0104 chemical sciences ,Anode ,Dielectric spectroscopy ,chemistry ,Chemical engineering ,General Materials Science ,Lithium ,Cyclic voltammetry ,0210 nano-technology - Abstract
The sodium-ion battery is a strong candidate for the large-scale energy storage device due to its low cost and abundant resources. However, the severe self-discharge issue, which is rooted in the dissolution of the solid-electrolyte interphase (SEI) film in the sodium-ion battery, impedes its practical application. Thus, the central question is how to build a stable SEI film onto the electrode surface. Here, we propose and experimentally demonstrate a LiF-rich SEI film at the surface of hard carbon (HC) anode in sodium-ion battery, which is generated by adding lithium difluoro(oxalate)borate (LiODFB) additive into the electrolyte of 1 M NaPF6 in EC:DMC (1:1 in volume ratio). The X-ray photoelectron spectroscopy (XPS) and electron microscopy (SEM and TEM) results confirm that we obtain the LiF-rich SEI film at the HC electrode surface, which grows up with the increasing of the concentration of added LiODFB additive. But it blocks the transmission of Na ions into HC as evidenced by the initial galvanostatic charge/discharge, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) results. Although this work shows a negative result, it denies the possibility of using the lithium compounds with lower solubility as SEI components for Na-ion battery since it allows to transfer the lithium ions rather than the Na ions. more...
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- 2020
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7. Ultrathin porous graphitic carbon nanosheets activated by alkali metal salts for high power density lithium-ion capacitors
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Zhixing Wang, Jiexi Wang, Huajun Guo, Guochun Yan, Guangchao Li, Xinhai Li, and Dai Yuqing
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Materials science ,Metals and Alloys ,Sintering ,Condensed Matter Physics ,Alkali metal ,Electrochemistry ,Catalysis ,Chemical engineering ,Specific surface area ,Electrode ,Materials Chemistry ,Physical and Theoretical Chemistry ,Porosity ,Power density - Abstract
Graphitic carbons with reasonable pore volume and appropriate graphitization degree can provide efficient Li+/electrolyte-transfer channels and ameliorate the sluggish dynamic behavior of battery-type carbon negative electrode in lithium-ion capacitors (LICs). In this work, onion-like graphitic carbon materials are obtained by using carbon quantum dots as precursors after sintering, and the effects of alkali metal salts on the structure, morphology and performance of the samples are focused. The results show that alkali metal salts as activator can etch graphitic carbons, and the specific surface area and pore size distribution are intimately related to the description of the alkali metal salt. Moreover, it also affects the graphitization degree of the materials. The porous graphitic carbons (S-GCs) obtained by NaCl activation exhibit high specific surface area (77.14 m2·g−1) and appropriate graphitization degree. It is expectable that the electrochemical performance for lithium-ions storage can be largely promoted by the smart combination of catalytic graphitization and pores-creating strategy. High-performance LICs (S-GCs//AC LICs) are achieved with high energy density of 92 Wh·kg−1 and superior rate capability (66.3 Wh·kg−1 at 10 A·g−1) together with the power density as high as 10020.2 W·kg−1. more...
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- 2020
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8. Al4B2O9 nanorods-modified solid polymer electrolytes with decent integrated performance
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Xinhai Li, Yong Ke, Huajun Guo, Yuqi Wu, Xiqiang Guo, Zhixing Wang, Peng Wenjie, Fu Haikuo, Jiexi Wang, and Wu Lijue
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chemistry.chemical_classification ,Materials science ,Ethylene oxide ,02 engineering and technology ,Electrolyte ,Polymer ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,Energy storage ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Ionic conductivity ,General Materials Science ,Nanorod ,0210 nano-technology ,Electrochemical window - Abstract
With the proliferation of energy storage and power applications, electric vehicles particularly, solid-state batteries are considered as one of the most promising strategies to address the ever-increasing safety concern and high energy demand of power devices. Here, we demonstrate the Al4B2O9 nanorods-modified poly(ethylene oxide) (PEO)-based solid polymer electrolyte (ASPE) with high ionic conductivity, wide electrochemical window, decent mechanical property and nonflammable performance. Specifically, because of the longer-range ordered Li+ transfer channels conducted by the interaction between Al4B2O9 nanorods and PEO, the optimal ASPE (ASPE-1) shows excellent ionic conductivity of 4.35×10−1 and 3.1×10−1 S cm−1 at 30 and 60°C, respectively. It also has good electrochemical stability at 60°C with a decomposition voltage of 5.1 V. Besides, the assembled LiFePO4//Li cells show good cycling performance, delivering 155 mA h g−1 after 300 cycles at 1 C under 60°C, and present excellent low temperature adaptability, retaining over 125 mA h g−1 after 90 cycles at 0.2 C under 30°C. These results verify that the addition of Al4B2O9 nanorods can effectively promote the integrated performance of solid polymer electrolyte. more...
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- 2020
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9. High-performance spherical LiVPO4F/C cathode enabled by facile spray pyrolysis
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Guochun Yan, Zhou Yongmao, Jiexi Wang, JiaYi Li, and Ding Xiaobo
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Diffraction ,Materials science ,Rietveld refinement ,General Engineering ,02 engineering and technology ,Electrolyte ,Triclinic crystal system ,Conductivity ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,Cathode ,0104 chemical sciences ,Corrosion ,law.invention ,Chemical engineering ,law ,General Materials Science ,0210 nano-technology - Abstract
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 h g–1 at 1, 40 C respectively, and remaining the capacity of 93.3 mA h g–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 LiVPO4F with good conductivity. more...
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- 2020
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10. Graphitic nanorings for super-long lifespan lithium-ion capacitors
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Bianzheng You, Zhixing Wang, Guochun Yan, Jiexi Wang, Huajun Guo, Yong Liu, Zhoulan Yin, Guangchao Li, and Dai Yuqing
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Materials science ,Graphene ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Energy storage ,0104 chemical sciences ,law.invention ,Chemical engineering ,Amorphous carbon ,chemistry ,Quantum dot ,law ,Phase (matter) ,General Materials Science ,Electrical and Electronic Engineering ,0210 nano-technology ,Mesoporous material ,Carbon - Abstract
Porous graphitic carbon nanorings (PGCNs) are proposed by smart catalytic graphitization of nano-sized graphene quantum dots (GQDs). The as-prepared PGCNs show unique ring-like morphology with diameter around 10 nm, and demonstrate extraordinary mesoporous structure, controllable graphitization degree and highly defective nature. The mechanism from GQDs to PGCNs is proven to be a dissolution-precipitation process, undergoing the procedure of amorphous carbon, intermediate phase, graphitic carbon nanorings and graphitic carbon nanosheets. Further, the relationship between particles size of GQDs precursor and graphitization degree of PGCNs products is revealed. The unique microstructure implies PGCNs a broad prospect for energy storage application. When applied as negative electrode materials in dual-carbon lithium-ion capacitors, high energy density (77.6 Wh·kg−1) and super long lifespan (89.5% retention after 40,000 cycles at 5.0 A·g−1) are obtained. The energy density still maintains at 24.5 Wh·kg−1 even at the power density of 14.1 kW·kg−1, demonstrating excellent rate capability. The distinct microstructure of PGCNs together with the strategy for catalytic conversion from nanocarbon precursors to carbon nanorings opens a new window for carbon materials in electrochemical energy storage. more...
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- 2020
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11. Al-doped NaNi1/3Mn1/3Fe1/3O2 for high performance of sodium ion batteries
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Guochun Yan, Anxia Ma, Huajun Guo, Zhixing Wang, Jiexi Wang, and Zhoulan Yin
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Battery (electricity) ,Materials science ,General Chemical Engineering ,Sodium ,Doping ,General Engineering ,Analytical chemistry ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,Cathode ,Energy storage ,0104 chemical sciences ,law.invention ,X-ray photoelectron spectroscopy ,chemistry ,law ,Structural stability ,General Materials Science ,0210 nano-technology - Abstract
Herein, we report a series of O3-type Na(Ni1/3Mn1/3Fe1/3)1-xAlxO2 (x = 0, 0.03, 0.05, 0.07) oxides as sodium-ion battery cathode materials synthesized via spray pyrolysis method. The structure, morphology, and electrochemical performance of Na(Ni1/3Mn1/3Fe1/3)1-xAlxO2 (x = 0, 0.03, 0.05, 0.07) are characterized by XRD, SEM, CV, and galvanostatic charge and discharge tests, respectively. Na(Ni1/3Mn1/3Fe1/3)0.95Al0.05O2 delivers an initial discharge capacity of 145.4 mAh g−1 at 0.1 C and exhibits a favorable reversible capacity about 128.4 mAh g−1 after 80 cycles at 0.2 C, with the capacity retention of 77.5% at the voltage range of 2.0 to 4.2 V. XPS analysis reveals that Al-doping could alleviate the Jahn-Teller effect caused by Mn3+ and enhance the structural stability of layered oxides. The results confirm that a small quantity of (5 at. %) Al-doping improves the structural stability of the material, therefore leading to the excellent electrochemical performance. more...
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- 2020
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12. The influences of SO42− from electrolytic manganese dioxide precursor on the electrochemical properties of Li-rich Mn-based material for Li-ion batteries
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Zhixing Wang, Jiexi Wang, Fanbo Meng, Guochun Yan, Xianwen Wu, Huajun Guo, Xinhai Li, and Lijiao Zhou
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Materials science ,General Chemical Engineering ,General Engineering ,General Physics and Astronomy ,chemistry.chemical_element ,Sintering ,02 engineering and technology ,Electrolyte ,Manganese ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,Cathode ,0104 chemical sciences ,Corrosion ,law.invention ,chemistry ,Chemical engineering ,law ,Electrode ,General Materials Science ,0210 nano-technology ,Ball mill - Abstract
A series of layered Li[Li0.2Mn0.54Ni0.13Co0.13]O2 cathode materials, of which manganese source was electrolytic manganese dioxide, with different contents of SO42− were successfully synthesized via ball-milling process and solid-state sintering method. The obtained materials were characterized by XRD, XPS, SEM-EDS, C-S, ICP, and HR-TEM. All the obtained materials presented well-ordered layered structure. When the content of SO42− was below 1.30 wt%, the electrochemical properties and structural stabilities at low rate for the layered materials with SO42− were not changed dramatically, while when the content of SO42− increased to 5.85 wt%, the initial discharge capacities decreased dramatically from 248.24 to 209.23 mAh g−1 at 10 mA g−1. And the pristine sample shows excellent cyclic property and rate capability. It delivered the discharge capacity of 175.25 mAh g−1 after 100 cycles with the highest capacity retention of 90.67% at 200 mA g−1. Particularly, the treated Li-rich Mn-based materials with the highest amount of SO42− exhibited the best cyclic stability and it delivers the highest capacity retention of 95.17% after 100 cycles at 200 mA g−1. However, its discharge capacities were much lower than the pristine material. As a result, the addition of SO42− could promote side reactions between electrode and electrolyte and deep-degree corrosion of electrode materials to affect the electrochemical properties and structural stabilities of the Li-rich Mn-based materials. more...
- Published
- 2018
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13. Magnesium-doped Li[Li0.2Mn0.54Ni0.13Co0.13]O2 cathode with high rate capability and improved cyclic stability
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Huimian Li, Huajun Guo, Fanbo Meng, Zhixing Wang, Xianwen Wu, Jiexi Wang, and Xinhai Li
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Diffraction ,Materials science ,Scanning electron microscope ,Magnesium ,General Chemical Engineering ,Doping ,General Engineering ,Analytical chemistry ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,Cathode ,0104 chemical sciences ,law.invention ,chemistry ,Structural stability ,law ,Phase (matter) ,General Materials Science ,0210 nano-technology - Abstract
Mg-doped Li[Li0.2Mn0.54 − x/3Ni0.13 − x/3Co0.13 − x/3Mgx]O2 (x = 0, 0.005, 0.007, 0.01, and 0.02) cathode materials have been synthesized by mixing Mn0.54Ni0.13Co0.13(CO3)0.8 precursor, Li2CO3, and MgO, followed by high-temperature solid-state method. X-ray diffraction (XRD) results show that Mg-doped samples have enlarged interlayer distance and orderly layered structure. Scanning electron microscope (SEM) results indicate that all the samples have similar morphologies. Electrochemical tests indicate that Mg doping facilitates the activation of Li2MnO3 phase and suppresses the transformation from layered to spinel-like phase. Mg-doped samples possess improved cyclic and rate performance. The Li[Li0.2Mn0.54 − x/3Ni0.13 − x/3Co0.13 − x/3Mgx]O2 (x = 0.01) sample delivers a capacity retention of 92.07% compared with 75.25% of the undoped one after 200 cycles at 250 mA g−1 and exhibits the discharge capacity of 198.56 mAh g−1 at 500 mA g−1. The reasons for the improved electrochemical performance are the enlarged interslab spacing and the enhanced structural stability. more...
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- 2018
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14. Improving the Desulfurization Degree of High-Grade Nickel Matte via a Two-Step Oxidation Roasting Process
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Zhixing Wang, Huajun Guo, Guochun Yan, Jiexi Wang, Xinhai Li, and Xi Zhao
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Materials science ,Nickel sulfide ,Metallurgy ,Metals and Alloys ,chemistry.chemical_element ,02 engineering and technology ,Heazlewoodite ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Sulfur ,020501 mining & metallurgy ,Flue-gas desulfurization ,Nickel ,chemistry.chemical_compound ,0205 materials engineering ,chemistry ,Transition metal ,Mechanics of Materials ,Materials Chemistry ,Melting point ,0210 nano-technology ,Roasting - Abstract
Generally, sulfur elimination from nickel matte was incomplete in the one-step oxidation roasting process. In this work, X-ray diffraction, scanning electron microscopy/energy-dispersive X-ray spectroscopy, and chemical analysis of the roasted products were carried out to explain this phenomenon. The results indicated that the melting of heazlewoodite was the main limiting factor. Thereafter, the oxidation mechanism of high-grade nickel matte from room temperature to 1000 °C was studied. It was found that the transformation from heazlewoodite (Ni3S2) to nickel sulfide (NiS) took place from 400 °C to 520 °C. Considering that the melting temperature of NiS was much higher than that of Ni3S2, a low-temperature roasting step was suggested to suppress the melting of heazlewoodite. Under the optimum conditions (520 °C for 120 minutes followed by 800 °C for 80 minutes), the degree of desulfurization reached 99.52 pct. These results indicated that the two-step oxidation roasting method could be a promising process for producing low-sulfur calcine from high-grade nickel matte. more...
- Published
- 2018
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15. Compact structured silicon/carbon composites as high-performance anodes for lithium ion batteries
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Zhixing Wang, Jiexi Wang, Huajun Guo, Yu Zhou, Xinhai Li, Yang Yang, and Zhewei Yang
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Materials science ,Softening point ,Silicon ,General Chemical Engineering ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,engineering.material ,010402 general chemistry ,01 natural sciences ,Coating ,medicine ,General Materials Science ,Graphite ,Coal tar ,Composite material ,General Engineering ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,chemistry ,engineering ,Lithium ,0210 nano-technology ,Carbon ,Pyrolysis ,medicine.drug - Abstract
Compact-structured silicon/carbon composites consisting of silicon, graphite, and coal tar pitch pyrolysis carbon are prepared via two heating procedures after liquid solidification. The first heating procedure plays a key role in the formation of compact-structured silicon/carbon composites, in which the coal tar pitch has a good fluidity at 180 °C above the softening temperature, and it is easy to form a uniform coating on the surface of materials. At the same time, the fluidic coal tar pitch could also fill the voids between particles to form compact-structured silicon/carbon composites. As-prepared silicon/carbon composites exhibit moderate reversible capacity of 602.4 mAh g−1, high initial charge-discharge efficiency of 82.3%, and good cycling stability with the capacity retention of 93.4% at 0.1 A g−1 after 50 cycles. It is noteworthy that the synthetic method is scalable which is suitable for mass production. more...
- Published
- 2018
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16. An Ostwald ripening route towards Ni-rich layered cathode material with cobalt-rich surface for lithium ion battery
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Huajun Guo, Zhixing Wang, Jiexi Wang, Yan Li, and Xinhai Li
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Ostwald ripening ,Phase transition ,Materials science ,chemistry.chemical_element ,02 engineering and technology ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Lithium-ion battery ,Cathode ,0104 chemical sciences ,law.invention ,symbols.namesake ,chemistry ,Chemical engineering ,law ,symbols ,General Materials Science ,SPHERES ,0210 nano-technology ,Porosity ,Cobalt - Abstract
An Ostwald ripening-based route is proposed to prepare Ni-rich layered cathodes with Co-rich surface for lithium-ion batteries (LIBs). Commercially available Ni0.8Co0.1Mn0.1(OH)2 and spray pyrolysis derived porous Co3O4 are used as mixed precursors. During the lithiation reaction process under high-temperature, the porous Co3O4 microspheres scatter primary particles and spontaneously redeposit on the surface of Ni-rich spheres according to Ostwald ripening mechanism, forming the Ni-rich materials with Co-rich outer layers. When evaluated as cathode for LIBs, the resultant material shows ability to inhibit the cation disorder, relieves the phase transition from H2 to H3 and diminishes side reactions between the electrolyte and Ni-rich cathode material. As a result, the obtained material with Co-rich outer layers exhibits much more improved cycle and rate performance than the material without Co-rich outer layers. Particularly, NCM-Co-1 (molar ratio of Ni0.8Co0.1Mn0.1(OH)2/Co3O4 is 60:1) delivers a reversible capacity of 159.2 mA h g−1 with 90.5% capacity retention after 200 cycles at 1 C. This strategy provides a general and efficient way to produce gradient substances and to address the surface problems of Ni-rich cathode materials. more...
- Published
- 2017
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17. Fluorinated solvents for high-voltage electrolyte in lithium-ion battery
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Hu Qiyang, Zhixing Wang, Xinhai Li, Peng Wenjie, Jiexi Wang, Huajun Guo, and Guochun Yan
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Chemistry ,Inorganic chemistry ,02 engineering and technology ,Electrolyte ,Conductivity ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Cathode ,Lithium-ion battery ,0104 chemical sciences ,law.invention ,Anode ,chemistry.chemical_compound ,X-ray photoelectron spectroscopy ,law ,Electrochemistry ,Carbonate ,General Materials Science ,Electrical and Electronic Engineering ,0210 nano-technology ,Ethylene carbonate - Abstract
The major obstacle for the application of high-voltage cathode materials is the anodic instability of the electrolyte. On the guidance of density functional theory calculation, we develop a new high-voltage electrolyte comprising 1 mol L−1 LiPF6 dissolved in fluoroethylene carbonate (FEC) and ethyl difluoroacetate (DFEAc) (FEC/DFEAc = 3:7 in wt.% ratio). It shows a high conductivity (9.48 mS cm−1) and high anodic stability compared with the conventional electrolyte of 1 mol L−1 LiPF6 dissolved in ethylene carbonate (EC) and ethyl-methyl carbonate (EMC) (EC/EMC = 3:7 in wt.% ratio). In addition, Li/LiNi0.5Co0.2Mn0.3O2 half-cells with the new electrolyte display an excellent cycling ability with capacity retention of 89.23% after 100 cycles at 4.6 V (vs. Li/Li+). Although the electrolyte still will be oxidized at the cathode surface, the Li2CO3 and carbon-fluoride species originated from DFEAc and FEC are beneficial to building a stable cathode/electrolyte interface as revealed by the TEM and XPS results. more...
- Published
- 2017
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18. Nondestructive Measurement of Hemoglobin in Blood Bags Based on Multi-Pathlength VIS-NIR Spectroscopy
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Gang Li, Hui Cao, Donggen Wang, Ling Lin, Jiexi Wang, Shengzhao Zhang, and Ying Han
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Materials science ,Nondestructive measurement ,Analytical chemistry ,lcsh:Medicine ,02 engineering and technology ,Hemoglobin levels ,01 natural sciences ,Article ,Hemoglobins ,Blood product ,medicine ,lcsh:Science ,Spectroscopy ,Spectroscopy, Near-Infrared ,Multidisciplinary ,lcsh:R ,010401 analytical chemistry ,Vis nir spectroscopy ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Red blood cell ,medicine.anatomical_structure ,Curve fitting ,Blood Banks ,lcsh:Q ,Hemoglobin ,0210 nano-technology ,Blood Chemical Analysis - Abstract
Hemoglobin concentration is an indicator for assessing blood product quality. To measure hemoglobin concentration in blood products without damaging blood bags, we proposed a method based on visible-near infrared transmission spectroscopy. Complex optical properties of blood bag walls result in measurement irregularities. Analyses showed that the slope of the light intensity-pathlength curve was more robust to the influence of the blood bag wall. In this study, the transmission spectra of red blood cell suspensions at multiple optical pathlengths were obtained, and the slopes of logarithmic light intensity-pathlength curves were calculated through curve fitting. A nondestructive measurement of hemoglobin content was achieved by using a regression model correlating slope spectra and hemoglobin concentration. Sixty samples with hemoglobin concentrations ranging from 72 to 161 g/L were prepared. Among them, 40 samples were used as a calibration set, and the remaining 20 samples were used as a prediction set. The determination coefficient of the prediction set was 0.97, with a mean square error of 2.78 g/L. This result demonstrates that a non-destructive measurement of hemoglobin levels in blood bags can be achieved by multiple-pathlength transmission spectroscopy. more...
- Published
- 2018
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19. Sustainable synthesis of Penicillium-derived highly conductive carbon film as superior binder-free electrode of lithium ion batteries
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Liyuan Zhang, Jiexi Wang, Wanting Yu, Zhihui Yang, Haiying Wang, Yangyang Wang, Bing Peng, and Liyuan Chai
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Materials science ,Carbonization ,Scanning electron microscope ,Inorganic chemistry ,Infrared spectroscopy ,chemistry.chemical_element ,Condensed Matter Physics ,Carbon film ,chemistry ,Electrochemistry ,General Materials Science ,Lithium ,Electrical and Electronic Engineering ,Fourier transform infrared spectroscopy ,Pyrolysis ,Carbon - Abstract
Fungi (Penicillium chrysogenum) were used as green and sustainable sources to fabricate free-standing binder-free carbon film through pyrolysis in inert atmosphere. The fungi before and after carbonization were characterized with scanning electron microscope (SEM), Fourier transformed infrared spectroscopy (FTIR), electron microprobe (EM), and Raman spectrum. The results showed that the fungi were composed of ultra-long microfibers around 3 μm in diameter, which can be readily transformed into membrane precursor. Abundant functional groups were detected on fungi. The carbon membrane from the pyrolysis of membrane precursor was constructed by the uniformly interconnected fibers. After carbonization, the functional groups disappeared, while the product was doped by O and N atoms. The conductivity of carbon film was as high as 29.4 S cm−1. Moreover, the carbon film was successfully applied as low-cost electrode in lithium ion batteries (LIBs). The capacity of the LIBs maintained 207 mA h g−1 with 89.6 % capacity retention after 80 cycles. more...
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- 2014
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20. Systematic investigation on determining chemical diffusion coefficients of lithium ion in Li1 + x VPO4F (0 ≤ x ≤ 2)
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Xinhai Li, Bin Huang, Huajun Guo, Zhixing Wang, Jiexi Wang, Guochun Yan, and Zhiguo Wang
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Chemistry ,Diffusion ,Electrochemistry ,Analytical chemistry ,chemistry.chemical_element ,General Materials Science ,Lithium ,Electrical and Electronic Engineering ,Cyclic voltammetry ,Condensed Matter Physics ,Ion ,Dielectric spectroscopy - Abstract
The chemical diffusion coefficients of lithium ion ( $$ {D}_{{\mathrm{Li}}^{+}} $$ ) in Li1 + x VPO4F (0 ≤ x ≤ 2) between 3.0 and 0.01 V are systematically analyzed by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic intermittent titration technique (GITT). The results indicate that the $$ {D}_{{\mathrm{Li}}^{+}} $$ values depend heavily on the voltage state. Based on the results from EIS and GITT, the diffusion coefficients ( $$ {D}_{{\mathrm{Li}}^{+}} $$ ) measured in a single-phase region below 1.7 V have relatively steady values of about 10−9 (EIS) and 10−10 (GITT) cm2 s−1, respectively, while the $$ {D}_{{\mathrm{Li}}^{+}} $$ values in the single-phase region above 1.9 V decrease rapidly from 10−9 to 10−11 cm2 s−1 due to concentration of lithium ions in the bulk LiVPO4F. The Li+ chemical diffusion coefficients measured in the two-phase region by GITT range a lot from 10−9 to 10−14 cm2 s−1, while the $$ {D}_{{\mathrm{Li}}^{+}} $$ values in the two-phase region determined by CV are around 10−10 cm2 s−1. By the GITT, the $$ {D}_{{\mathrm{Li}}^{+}} $$ values in the two-phase region vary in non-linear shape with the charge–discharge voltage, which is ascribed to strong interactions of Li+ with other ions. more...
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- 2014
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21. Structure and electrochemical performance of LiCoO2 cathode material in different voltage ranges
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Zhixing Wang, Huajun Guo, Jiexi Wang, Ai Qi, Xinhai Li, Peng Wenjie, and Zhiguo Wang
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Materials science ,General Chemical Engineering ,General Engineering ,Analytical chemistry ,General Physics and Astronomy ,High voltage ,Electrolyte ,Electrochemistry ,Cathode ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Phase (matter) ,General Materials Science ,Lithium cobalt oxide ,Faraday efficiency ,Voltage - Abstract
LiCoO2 sample prepared by high-temperature solid state calcination shows a typical hexagonal structure with a single phase and fine particle size distribution. The high-voltage electrolyte with additive fluoroethylene carbonate (FEC) has been used. Electrochemical results show that the initial discharge capacities of the prepared LiCoO2 cathode are 157.7, 169.5, 191.0, and 217.5 mAh g−1 in the voltage ranges of 3.0–4.3, 3.0–4.4, 3.0–4.5, and 3.0–4.6 V, respectively. The capacity increases, while the initial coulombic efficiency and capacity retention decrease with increasing the charge cutoff voltage. The capacity retention is only 10.4 % after 200 cycles at 1C rate in the voltage range of 3.0–4.6 V. X-ray diffraction measurements confirm structural changes of the layered material in the different voltage ranges. A phase transition from the O3 to the H1-3 phase can be observed when LiCoO2 is charged above 4.5 V. The AC impedance analysis indicates that the resistances (R (sf+b), R ct) of the prepared LiCoO2 rapidly increase when the cell is charged to higher voltage. The amount of dissolved Co into the electrolyte also greatly increases with increasing the charge cutoff voltage. more...
- Published
- 2014
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22. Correction to: The influences of SO42− from electrolytic manganese dioxide precursor on the electrochemical properties of Li-rich Mn-based material for Li-ion batteries
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Fanbo Meng, Huajun Guo, Zhixing Wang, Jiexi Wang, Guochun Yan, Xianwen Wu, Xinhai Li, and Lijiao Zhou
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General Chemical Engineering ,General Engineering ,General Physics and Astronomy ,General Materials Science - Published
- 2019
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23. Carbonization and graphitization of pitch applied for anode materials of high power lithium ion batteries
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Huajun Guo, Zhixing Wang, Silin Huang, Lei Gan, Jiexi Wang, Wei Xiao, and Xinhai Li
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Polarized light microscopy ,Materials science ,Carbonization ,Graphene ,Scanning electron microscope ,Condensed Matter Physics ,Dielectric spectroscopy ,law.invention ,Chemical engineering ,law ,Transmission electron microscopy ,Electrochemistry ,General Materials Science ,Crystallite ,Graphite ,Electrical and Electronic Engineering - Abstract
The artificial graphite materials were prepared by carbonizing coal tar pitch using two methods, namely, one- and two-step processes, and all sintered samples were graphitized at 2800 °C. Effects of different heat treatments on the performance of the samples were characterized by scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction, Brunauer–Emmett–Teller, electrochemical impedance spectroscopy (EIS), particle size analysis, polarized light microscopy, and charge–discharge measurements. All samples show a typical graphite crystalline structure; moreover, the degree of graphitization (g factor) and crystallite size along the c-axis (L c ) were calculated from (002) peak. The polarized light microscopy indicates that the coke with carbonization at 700 °C has an obvious wide domain (D) optical structure, while that with two-step sintering at 400 and 700 °C has a mixed optical structures of wide D, flow domains, and mosaics. TEM analysis revealed a number of irregular graphene layer images which are caused by the defects of graphite. EIS shows that the sample carbonized by two-step has a larger diffusion coefficient than the sample carbonized at 700 °C by one step. Higher carbonization temperature leads to better cycle performance as the temperature increasing from 500 to 700 °C in the one-step route. Specifically, the charge (Li+ extraction) capacity at the 50th cycle increases from 318 mA h g−1 to 357 mA h g−1. The results show that the rate performance of the artificial graphite is improved with the addition of the presintering at 400 °C. more...
- Published
- 2013
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24. Comprehensive reinvestigation on the initial coulombic efficiency and capacity fading mechanism of LiNi0.5Mn1.5O4 at low rate and elevated temperature
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Huajun Guo, Zhixing Wang, Jiexi Wang, Peng Yue, Xinhai Li, and Xianwen Wu
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Chromatography ,Chemistry ,Thermal decomposition ,Electrolyte ,Condensed Matter Physics ,Decomposition ,Energy storage ,Chemical engineering ,Phase (matter) ,Electrochemistry ,General Materials Science ,Thermal stability ,Electrical and Electronic Engineering ,Capacity loss ,Faraday efficiency - Abstract
The effect of different membranes and aluminum current collectors on the initial coulombic efficiency of LiNi0.5Mn1.5O4/Li was investigated, and the cycling performance at different rates and temperatures and the storage performance at 60 °C for a week are discussed for LiNi0.5Mn1.5O4/Li. The results show that the lower initial coulombic efficiency is associated with the lower decomposition voltage of the commercial membrane and electrolyte, and the instability of aluminum current collector under the higher voltage. In addition, both versions of LiNi0.5Mn1.5O4 can deliver about 115 mA h g−1 of initial discharge capacity at 1 C at 25 °C and 60 °C; however, it retains only 61.57 % of its initial capacity after the 130th cycles at 60 °C, which is much lower than the 94.46 % rate observed for LiNi0.5Mn1.5O4 at 25 °C, and the cycling performance of the material at 1 C is better than that at 0.5 C. Meanwhile, the initial discharge capacity at 0.1 C after storing at 60 °C is 119.3 mA h g−1, which is only a little lower than 121.5 mA h g−1 recorded before storing; moreover, the spinel structure and surface state of LiNi0.5Mn1.5O4 after storing at 60 °C has not been changed basically. These results indicate that the electrochemical stability of electrolyte is also related to the temperature. The serious capacity fading of LiNi0.5Mn1.5O4 at 60 °C is attributed to the severe oxidation decomposition and the thermal decomposition in the range of cut-off voltage of the materials, and then the decomposition products interact with active materials to form a solid interface phase, leading to the larger electrode polarization and irreversible capacity loss. Meanwhile, the worse cycling performance at 0.5 C than that at 1 C is attributed to the longer interaction time between the electrolyte and the active materials. However, the storage performance of LiNi0.5Mn1.5O4 corresponds to the thermal stability of electrolyte to a certain extent. more...
- Published
- 2012
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25. Comparative investigations of LiVPO4F/C and Li3V2(PO4)3/C synthesized in similar soft chemical route
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Huajun Guo, Wei Xiao, Xinhai Li, Zhenjiang He, Zhixing Wang, Silin Huang, and Jiexi Wang
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Materials science ,Reducing agent ,Annealing (metallurgy) ,Analytical chemistry ,Triclinic crystal system ,Condensed Matter Physics ,Electrochemistry ,Ascorbic acid ,X-ray photoelectron spectroscopy ,Amorphous carbon ,General Materials Science ,Electrical and Electronic Engineering ,Monoclinic crystal system - Abstract
Triclinic LiVPO4F and monoclinic Li3V2(PO4)3 are synthesized through a soft chemical process with mechanical activation assist, followed by annealing. In this process, ascorbic acid is used as reducing agent as well as carbon source. The as-prepared samples are coated with amorphous carbon. XPS analysis results show the expected valency states of ions in LiVPO4F and Li3V2(PO4)3. The electrochemical properties of the prepared LiVPO4F/C and Li3V2(PO4)3/C cathodes are evaluated. The as-prepared LiVPO4F/C cathode shows an initial discharge specific capacity of 140 ± 3 mAh g−1 at 30 mA g−1 in the voltage range of 3.0~4.4 V, compared with that of 138 ± 3 mAh g−1 possessed by Li3V2(PO4)3/C. Both samples exhibit good cycle performance at different current densities. The capacity delivered by LiVPO4F remains 95.5 and 91.7 % of its initial discharge capacity after 50 cycles at 150 and 750 mA g−1, respectively, while 97.4 and 90.6 % for Li3V2(PO4)3/C. But the rate capability of LiVPO4F/C is not so good compared with as-prepared Li3V2(PO4)3/C. more...
- Published
- 2012
- Full Text
- View/download PDF
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