| 1. |
- Chen, Wenju, et al.
(author)
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Porous cellulose diacetate-SiO2 composite coating on polyethylene separator for high-performance lithium-ion battery
- 2016
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In: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 147, s. 517-524
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Journal article (peer-reviewed)abstract
- The developments of high-performance lithium ion battery are eager to the separators with high ionic conductivity and thermal stability. In this work, a new way to adjust the comprehensive properties of inorganic-organic composite separator was investigated. The cellulose diacetate (CDA)-SiO2 composite coating is beneficial for improving the electrolyte wettability and the thermal stability of separators. Interestingly, the pore structure of composite coating can be regulated by the weight ratio of SiO2 precursor tetraethoxysilane (TEOS) in the coating solution. The electronic performance of lithium ion batteries assembled with modified separators are improved compared with the pristine PE separator. When weight ratio of TEOS in the coating solution was 9.4%, the composite separator shows the best comprehensive performance. Compared with the pristine PE separator, its meltdown temperature and the break-elongation at elevated temperature increased. More importantly, the discharge capacity and the capacity retention improved significantly.
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| 2. |
- Chen, Wenju, et al.
(author)
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Water-Based Organic-Inorganic Hybrid Coating for a High-Performance Separator
- 2016
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In: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 4:7, s. 3794-3802
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Journal article (peer-reviewed)abstract
- With the development of electric vehicles, the traditional polyolefin separators can not meet the increasing requirements of lithium ion batteries with high power density, high energy density, and high safety performance. Herein, a novel water-based binder is synthesized by grafting carboxyl groups onto cellulose diacetate. When the polyethylene (PE) separator is coated by this binder and SiO2 nanoparticles, the thermal shrinkage of the modified separator is observed to be almost 0% after exposure at 200 degrees C for 30 min. The puncture strength significantly increase from 5.10 MPa (PE separator) to 7.64 MPa. More importantly, the capacity retention of the cells assembled with modified separators after 100 cycles at 0.5 C increase from 73.3% (cells assembled with PE separator) to 81.6%, owing to the excellent electrolyte uptake and the good compatibility with lithium electrode. Besides, the modified separator shows excellent surface stability after 100 cycles. Considering the above excellent properties, this composite separator shows high potential to be used in lithium ion batteries with high power density and safety.
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| 3. |
- Chi, Mingming, et al.
(author)
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Excellent rate capability and cycle life of Li metal batteries with ZrO2/POSS multilayer-assembled PE separators
- 2016
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In: NANO ENERGY. - : Elsevier BV. - 2211-2855. ; 28, s. 1-11
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Journal article (peer-reviewed)abstract
- Today there are new interests in using metallic lithium as anode materials in lithium batteries because of its extremely large theoretical specific capacity. However, the low cycle efficiency and the lithium dendrite formation during repeated charge/discharge cycles hinder the practical application of metallic lithium anodes. Herein, we report a distinctive ZrO2/POSS multilayer deposited on PE separators by a simple layer-by-layer (LbL) self-assembly process to enable excellent rate capability and cycle life of lithium metal batteries. The ZrO2/POSS multilayer on PE separators weakens the solvation effect of lithium ions and significantly enhances the electrolyte uptake of separators, which is responsible for the enhanced ionic conductivity and Li+ transference number, as well as the improved Li/electrolyte interfacial stability. These advantageous characteristics of the resulting PE separators effectively decrease the electrode polarization and protect lithium metal anodes against lithium dendrites formation during repeated charge/discharge cycles, endowing LiCoO2/Li unit cells with both excellent electrochemical performance and high safety. The fundamental understanding on the effects of the micro/nano structures and properties of separators on the important electrochemistry processes at electrode/electrolyte interface of battery systems may lead to new approaches to tackle the intrinsic problems of Li metal anodes for energy storage applications.
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| 4. |
- Gu, Xiuquan, et al.
(author)
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ZnO nanomaterials : Strategies for improvement of photocatalytic and photoelectrochemical activities
- 2019. - 1
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In: Current Developments in Photocatalysis and Photocatalytic Materials. - Amsterdam : Elsevier. - 0128190000 - 9780128190005 ; , s. 231-244
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Book chapter (peer-reviewed)abstract
- ZnO is a promising material for photoanodes and applications within photocatalysis, due to its controllable morphology, excellent stability, and high velocity (>100 cm2 V−1·s−1) for charge carrier migration. In addition, the deep lying valence band edge provides a high driving force for many oxidation reactions, including water oxidation. For a tailored artificial light such as UV light–emitting diodes, ZnO photocatalysis can be very effective while the relatively wide bandgap of ∼3.3 eV yields a limitation in utilizing the full potential of the solar spectrum for photocatalysis. A lot of effort has been made to enhance the photocatalytic (PC) activity of ZnO, either by extending the absorption into the visible range by doping or by more efficient use of the absorbed photons in the UV range. In our previous studies, we have demonstrated that the PC activity of ZnO nanocrystals could be enhanced via morphology tuning, the formation of a Schottky junction with Au or Ag nanoparticles, and the combination with narrow-bandgap semiconductors. We have also shown the photoelectrochemical activity of ZnO nanorod arrays can be improved through thermal treatment or being modified with a ZnS thin layer. Another strategy is to control the electronic properties in ZnO by quantum confinement, which provides tunability of the electronic levels and introduces the ability to target specific reactions at the expense of widening the bandgap. In this chapter, we succinctly present the current progress in ZnO photocatalysis, strategies to improve and control the PC activity, and bring up the present and future prospect of ZnO as a photocatalyst.
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| 5. |
- Liu, Chenjuan, et al.
(author)
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3-D binder-free graphene foam as a cathode for high capacity Li-O-2 batteries
- 2016
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In: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 4:25, s. 9767-9773
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Journal article (peer-reviewed)abstract
- To provide energy densities higher than those of conventional Li-ion batteries, a Li-O-2 battery requires a cathode with high surface area to host large amounts of discharge product Li2O2. Therefore, reversible formation of discharge products needs to be investigated in Li-O-2 cells containing high surface area cathodes. In this study, a binder-free oxygen electrode consisting of a 3-D graphene structure on aluminum foam, with a high defect level (I-D/I-G = 1.38), was directly used as the oxygen electrode in LiO2 batteries, delivering a high capacity of about 9 x 10(4) mA h g(-1) (based on the weight of graphene) at the first full discharge using a current density of 100 mA g(graphene)(-1). This performance is attributed to the 3-D porous structure of graphene foam providing both an abundance of available space for the deposition of discharge products and a high density of reactive sites for Li-O-2 reactions. Furthermore, the formation of discharge products with different morphologies and their decomposition upon charge were observed by SEM. Some nanoscaled LiOH particles embedded in the toroidal Li2O2 were detected by XRD and visualized by TEM. The amount of Li2O2 formed at the end of discharge was revealed by a titration method combined with UV-Vis spectroscopy analysis.
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| 6. |
- Liu, Chenjuan, 1988-, et al.
(author)
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3-D binder-free graphene foam as cathode for high capacity Li-O2 batteries
- 2016
-
In: Journal of Materials Chemistry A. - 2050-7488. ; 4:25, s. 9767-9773
-
Journal article (pop. science, debate, etc.)abstract
- To provide energy densities higher than those of conventional Li-ion batteries, a Li–O2 battery requires a cathode with high surface area to host large amounts of discharge product Li2O2. Therefore, reversible formation of discharge products needs to be investigated in Li–O2 cells containing high surface area cathodes. In this study, a binder-free oxygen electrode consisting of a 3-D graphene structure on aluminum foam, with a high defect level (ID/IG = 1.38), was directly used as the oxygen electrode in Li– O2 batteries, delivering a high capacity of about 9 *104 mA h g-1 (based on the weight of graphene) at the first full discharge using a current density of 100 mA ggraphene-1 . This performance is attributed to the 3-D porous structure of graphene foam providing both an abundance of available space for the deposition of discharge products and a high density of reactive sites for Li–O2 reactions. Furthermore, the formation of discharge products with different morphologies and their decomposition upon charge were observed by SEM. Some nanoscaled LiOH particles embedded in the toroidal Li2O2 were detected by XRD and visualized by TEM. The amount of Li2O2 formed at the end of discharge was revealed by a titration method combined with UV-Vis spectroscopy analysis.
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| 7. |
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| 8. |
- Liu, Chenjuan, 1988-, et al.
(author)
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Growth of NaO2 in Highly Efficient Na–O2 Batteries Revealed by Synchrotron In Operando X-ray Diffraction
- 2017
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In: ACS Energy Letters. - : American Chemical Society (ACS). - 2380-8195. ; 2, s. 2440-2444
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Journal article (other academic/artistic)abstract
- The development of Na–O2 batteries requires understanding the formation of reaction products, as different groups reported compounds such as sodium peroxide, sodium superoxide, and hydrated sodium peroxide as the main discharge products. In this study, we used in operando synchrotron radiation powder X-ray diffraction (SR-PXD) to (i) quantitatively track the formation of NaO2 in Na–O2 cells and (ii) measure how the growth of crystalline NaO2 is influenced by the choice of electrolyte salt. The results reveal that the discharge could be divided into two time regions and that the formation of NaO2 during the major part of the discharge reaction is highly efficient. The findings indicate that the cell with NaOTf salt exhibited higher capacity than the cell with NaPF6 salt, whereas the average domain size of NaO2 particles decreases during the discharge. This fundamental insight brings new information on the working mechanism of Na–O2 batteries.
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| 9. |
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| 10. |
- Liu, Chenjuan, 1988-, et al.
(author)
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On the Stability of NaO2 in Na–O2 Batteries
- 2018
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In: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 10:16, s. 13534-13541
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Journal article (peer-reviewed)abstract
- Na–O2 batteries are regarded as promising candidates for energy storage. They have higher energy efficiency, rate capability, and chemical reversibility than Li–O2 batteries; in addition, sodium is cheaper and more abundant compared to lithium. However, inconsistent observations and instability of discharge products have inhibited the understanding of the working mechanism of this technology. In this work, we have investigated a number of factors that influence the stability of the discharge products. By means of in operando powder X-ray diffraction study, the influence of oxygen, sodium anode, salt, solvent, and carbon cathode were investigated. The Na metal anode and an ether-based solvent are the main factors that lead to the instability and decomposition of NaO2 in the cell environment. This fundamental insight brings new information on the working mechanism of Na–O2 batteries.
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