scholarly journals Synthesis of One-Dimensional Mesoporous Ag Nanoparticles-Modified TiO2 Nanofibers by Electrospinning for Lithium Ion Batteries

Materials ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 2630 ◽  
Author(s):  
Yuyao Zhang ◽  
Jun Li ◽  
Wenyao Li ◽  
Danning Kang

TiO2 is regarded as a prospective electrode material owing to its excellent electrochemical properties such as the excellent cycling stability and the high safety. However, its low capacity and low electronic conductivity greatly restrict the further improvement in electrochemical performance. A new strategy was put forward to solve the above defects involved in TiO2 in which the low capacity was enhanced by nanomerization and porosity of TiO2, and the low electronic conductivity was improved by introducing Ag with a high conductivity. One-dimensional mesoporous Ag nanoparticles-embedded TiO2 nanofibers (Ag@TiO2 nanofibers) were successfully synthesized via a one-step electrospinning process combined with subsequent annealing treatment in this study. The microstructure and morphology of mesoporous TiO2@Ag nanofibers were confirmed by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption–desorption. TiO2 nanofibers mainly consisted of a large amount of anatase TiO2, accompanied with traces of rutile TiO2. Ag nanoparticles were uniformly distributed throughout TiO2 nanofibers and promoted the transformation of TiO2 from the anatase to the rutile. The corresponding electrochemical performances are measured by galvanostatic charge-discharge, cycle stability, rate performance, cycle voltammetry, and electrochemical impedance spectroscopy measurements in this research, with pristine TiO2 nanofibers as the reference. The results indicated that the introduction of Ag nanoparticles into TiO2 nanofibers significantly improved the diffusion coefficient of Li ions (5.42 × 10−9 cm2⋅s−1 for pristine TiO2, 1.96 × 10−8 cm2⋅s−1 for Ag@TiO2), and the electronic conductivity of TiO2 (1.69 × 10−5 S⋅cm−1 for pristine TiO2, and 1.99 × 10−5 S⋅cm−1 for Ag@TiO2), based on which the comprehensive electrochemical performance were greatly enhanced. The coulombic efficiency of the Ag@TiO2 nanofibers electrode at the first three cycles was about 56%, 93%, and 96%, which was higher than that without Ag (48%, 66%, and 79%). The Ag@TiO2 nanofibers electrode exhibited a higher specific discharge capacity of about 128.23 mAh⋅g−1 when compared with that without Ag (72.76 mAh·g−1) after 100 cycles at 100 mA·g−1. With the current density sharply increased from 40 mA·g−1 to 1000 mA·g−1, the higher average discharge capacity of 56.35 mAh·g−1 was remained in the electrode with Ag, when compared with the electrode without Ag (average discharge capacity of about 12.14 mAh·g−1). When the current density was returned to 40 mA·g−1, 80.36% of the initial value was returned (about 162.25 mAh·g−1) in the electrode with Ag, which was evidently superior to that without Ag (about 86.50 mAh·g−1, only 55.42% of the initial value). One-dimensional mesoporous Ag@TiO2 nanofibers can be regarded as a potential and promising candidate as anode materials for lithium ion batteries.

NANO ◽  
2021 ◽  
pp. 2150119
Author(s):  
M. M. Xia ◽  
J. Li ◽  
Y. Y. Zhang ◽  
D. N. Kang ◽  
Y. L. Zhang

Nanosized TiO2 has been actively developed as a low-cost and environment-friendly anode material for lithium-ion batteries (LIBs), but its poor electronic conductivity seriously restricts its practical applications. This drawback is addressed in this work by the fabrication of one-dimensional mesoporous graphene@Ag@TiO2 composite nanofibers as anode materials for high-performance LIBs. The materials were prepared via electrospinning combined with annealing treatment, and the effects of graphene addition on the microstructure and electrochemical performance of the resulting mesoporous graphene@Ag@TiO2 nanofibers were investigated in detail. Ag@TiO2 nanofibers with the optimal amount of graphene displayed a maximum initial discharge capacity of [Formula: see text] at [Formula: see text] and retained a discharge capacity of [Formula: see text] at [Formula: see text] after 100 cycles. These results reflect the excellent cycling stability of the material. The average specific discharge capacity of the nanofibers ([Formula: see text] at [Formula: see text] was two-fold higher than that of samples without graphene, and their discharge capacity returned to [Formula: see text] (approximately [Formula: see text] for other nanofibers) when the current density was recovered to the initial value ([Formula: see text]. Electrochemical impedance spectroscopic measurements confirmed that the conductivity of the electrode was [Formula: see text], which is higher than that of bare mesoporous Ag@TiO2 ([Formula: see text]). Thus, one-dimensional mesoporous graphene@Ag@TiO2 nanofibers can be regarded as a promising anode material for LIBs.


2013 ◽  
Vol 01 (04) ◽  
pp. 1340017
Author(s):  
ZAILEI ZHANG ◽  
YANHONG WANG ◽  
MEIJU ZHANG ◽  
QIANGQIANG TAN ◽  
FABING SU

We report a facile chemical vapor deposition (CVD) method to grow silicon/carbon ( Si / C ) microspheres on commercial graphite microsphere (GMs) surface to prepare Si / C / GMs composite anode materials for Li -ion batteries. The CVD synthesis is conducted at 900°C using methyltrichlorosilane ( CH 3 SiCl 3) as both the Si and C precursor, which is a cheap byproduct in organosilane industry. The samples are characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis, Raman spectroscopy and X-ray photoelectron spectroscopy. It is found that the obtained Si / C / GMs composites are composed of Si nanocrystals, amorphous carbon and GMs. The CVD time significantly influences the morphology and electrochemical performance of the Si / C / GMs composite materials. The Si / C / GMs composite materials prepared at CVD condition of 900°C for 4 h possess improved electrochemical properties, showing a discharge capacity of 821.4 mAh g−1 at a rate of 50 mA g−1, and a good cycling performance (i.e., a reversible capacity of 565.2 mAh g−1 is retained after 50 cycles). The enhanced electrochemical performance is attributed to the formation of Si / C microsphere network among GMs, which increases the electronic conductivity and is able to buffer the large volume changes of Si during lithium ion insertion/extraction.


Author(s):  
Yaohua Feng ◽  
Hui Xu ◽  
Bo Wang ◽  
Shimin Wang ◽  
Ling Ai ◽  
...  

Abstract The Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) is considered as a promising high capacity (more than 160 mAh/g) cathode for lithium-ion batteries. However, NCM811 suffers the rapid capacity fading and potential safety hazard during cycling, which hinders further commercial application. Herein, a homogeneous Al2O3 film is successfully coated on the NCM811 surface by the liquid phase deposition. The Al2O3 coating layer is evidenced by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. The results clearly demonstrate that the Al2O3 film is uniformly covered on the NCM811. In particular, the 2 wt% Al2O3-coated materials delivers a high discharge capacity of 162.2 mAh/g and with retention of 82.67% after 100 cycles at 0.5 C than that of the pristine NCM811 electrode with retention of 64.90% and discharge capacity of 111.50 mAh/g. The improved electrochemical performance can be ascribed to the thin and dense coating layer not only effectively inhibits the direct contact between the material and the electrolyte but also promotes the transfer of Li+ in the layered structure material.


Energies ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 5124
Author(s):  
Eun Hyuk Chung ◽  
Jong Pil Kim ◽  
Hyun Gyu Kim ◽  
Jae-Min Chung ◽  
Sei-Jin Lee ◽  
...  

It has been reported that improving electrical conductivity and maintaining stable structure during discharge/charge process are challenge for Si to be used as an anode for lithium ion batteries (LIB). To address this problem, milkweed (MW) was carbonized to prepare hollow carbon microtubes (HCMT) derived from biomass as an anode template for LIB. In order to improve electrical conductivity, various materials such as chitosan (CTS), agarose, and polyvinylidene fluoride (PVDF) are used as carbon source (C1, C2, and C3) by carbonization. Carbon coated HCMT@Si composits, HCMT@Si@C1, HCMT@Si@C1@C2, and HCMT@Si@C1@C3, have been successfully synthesized. Changes in structure and crystallinity of HCMT@Si composites were characterized by using X-ray diffraction (XRD). Specific surface area for samples was calculated by using BET (Brunauer–Emmett–Teller). Also, pore size and particle size were obtained by particle and pore size analysis system. The surface morphology was evaluated using high resolution scanning electron microscopy (HR-SEM), Field Emission transmission electron microscopy (TEM). The thermal properties of HCMT@Si composites were analyzed by thermogravimetric analysis (TGA). Our research was performed to study the synthesis and electrochemical performance of Si composite with HCMT by the carbonization of natural micro hollow milkweed to form an inner space. After carbonization at 900 °C for 2 h in N2 flow, inner diameter of HCMT obtained was about 10 μm. The electrochemical tests indicate that HCMT@Si@C1@C3 exhibits discharge capacity of 932.18 mAh/g at 0.5 A/g after 100 cycles.


2021 ◽  
Author(s):  
Wencai Zhao ◽  
Y.F. Yuan ◽  
S.M. Yin ◽  
Gaoshen Cai ◽  
S.Y. Guo

Abstract Hollow mesoporous nanospheres MoO2/C are successfully constructed through metal chelating reaction between molybdenum acetylacetone and glycerol as well as the Kirkendall effect induced by diammonium hydrogen phosphate. MoO2 nanoparticles coupled by amorphous carbon are assembled to unique zigzag-like hollow mesoporous nanosphere with large specific surface area of 147.7 m2 g-1 and main pore size of 8.7 nm. The content of carbon is 9.1%. As anode material for lithium-ion batteries, the composite shows high specific capacity and excellent cycling performance. At 0.2 A g-1, average discharge capacity stabilizes at 1092 mAh g-1. At 1 A g-1 after 700 cycles, the discharge capacity still reaches 512 mAh g-1. Impressively, the composite preserves intact after 700 cycles. Even at 5 A g-1, the discharge capacity can reach 321 mAh g-1, exhibiting superior rate capability. Various kinetics analyses demonstrate that in electrochemical reaction, the proportion of the surface capacitive effect is higher, and the composite has relatively high diffusion coefficient of Li ions and fast faradic reaction kinetics. Excellent lithium storge performance is attributed to the synergistic effect of zigzag-like hollow mesoporous nanosphere and amorphous carbon, which improves reaction kinetics, structure stability and electronic conductivity of MoO2. The present work provides a new useful structure design strategy for advanced energy storage application of MoO2.


2018 ◽  
Vol 8 (11) ◽  
pp. 2140 ◽  
Author(s):  
Reddyprakash Maddipatla ◽  
Chadrasekhar Loka ◽  
Woo Choi ◽  
Kee-Sun Lee

Si/C nanocomposite was successfully prepared by a scalable approach through high-energy mechanical milling and carbonization process. The crystalline structure of the milled powders was studied using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Morphology of the milled powders was investigated by Field-emission scanning electron microscopy (FE-SEM). The effects of milling time on crystalline size, crystal structure and microstructure, and the electrochemical properties of the nanocomposite powders were studied. The nanocomposite showed high reversible capacity of ~1658 mAh/g with an initial cycle coulombic efficiency of ~77.5%. The significant improvement in cyclability and the discharge capacity was mainly ascribed to the silicon particle size reduction and carbon layer formation over silicon for good electronic conductivity. As the prepared nanocomposite Si/C electrode exhibits remarkable electrochemical performance, it is potentially applied as a high capacity anode material in the lithium-ion secondary batteries.


2014 ◽  
Vol 875-877 ◽  
pp. 183-186 ◽  
Author(s):  
Yi Ping Tang ◽  
Shi Ming Wang ◽  
Jia Feng Ding ◽  
Guang Ya Hou ◽  
Guo Qu Zheng

In this work, TiO2(B) nanotubes with uniform diameter were prepared by the simple route of hydrothermal synthesis, and graphene nanosheets were added to form TiO2(B)/graphene nanocomposites, the two kinds of materials were comparatively studied as anode materials. The morphology and crystal structure were studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The electrochemical performance was evaluated by galvanostatic chargedischarge tests. The results show that the nanocomposite electrode material has good electrochemical performance due to the contributions of graphene. At the current density of 50mA/g, the capacity of TiO2(B)/graphene is 135.8 mAh/g, and the coulombic efficiency is 61.8%, after 10 charge-discharge cycles it still retains 113.2mAh/g . However, TiO2(B) anode reduces rapidly to 65.6 mAh/g.


2019 ◽  
Vol 9 (19) ◽  
pp. 4032 ◽  
Author(s):  
Luis Zuniga ◽  
Gabriel Gonzalez ◽  
Roberto Orrostieta Chavez ◽  
Jason C. Myers ◽  
Timothy P. Lodge ◽  
...  

We report results on the electrochemical performance of flexible and binder-free α-Fe2O3/TiO2/carbon composite fiber anodes for lithium-ion batteries (LIBs). The composite fibers were produced via centrifugal spinning and subsequent thermal processing. The fibers were prepared from a precursor solution containing PVP/iron (III) acetylacetonate/titanium (IV) butoxide/ethanol/acetic acid followed by oxidation at 200 °C in air and then carbonization at 550 °C under flowing argon. The morphology and structure of the composite fibers were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). These ternary composite fiber anodes showed an improved electrochemical performance compared to the pristine TiO2/C and α-Fe2O3/C composite fiber electrodes. The α-Fe2O3/TiO2/C composite fibers also showed a superior cycling performance with a specific capacity of 340 mAh g−1 after 100 cycles at a current density of 100 mA g−1, compared to 61 mAh g−1 and 121 mAh g−1 for TiO2/C and α-Fe2O3/C composite electrodes, respectively. The improved electrochemical performance and the simple processing of these metal oxide/carbon composite fibers make them promising candidates for the next generation and cost-effective flexible binder-free anodes for LIBs.


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