Co-reporter:Dashuai Wang, Yu Gao, Yanhui Liu, Di Jin, Yury Gogotsi, Xing Meng, Fei Du, Gang Chen, and Yingjin Wei
The Journal of Physical Chemistry C June 22, 2017 Volume 121(Issue 24) pp:13025-13025
Publication Date(Web):June 5, 2017
DOI:10.1021/acs.jpcc.7b03057
The potential of a Ti2N monolayer and its Ti2NT2 derivatives (T = O, F, and OH) as anode materials for lithium-ion and beyond-lithium-ion batteries has been investigated by the first-principles calculations. The bare and terminated monolayers are metallic compounds with high electronic conductivity. The diffusion barriers on bare Ti2N monolayer are predicted to be 21.5 meV for Li+, 14.0 meV for Na+, 7.0 meV for K+, 75.9 meV for Mg2+, and 38.0 meV for Ca2+, which are the lowest values reported for state-of-the-art two-dimensional energy storage materials. The functional groups on Ti2NT2 increase the diffusion barriers by about 1 order of magnitude. The calculated capacities for the monovalent cations on Ti2N and Ti2NT2 are close to that of the conventional graphite anode in lithium-ion batteries. In comparison, the capacities for Mg2+ on Ti2N and Ti2NT2 are more than 2000 mAh g–1 due to the two-electron reaction and multilayer adsorption of Mg2+. Comparison of the electrochemical performances of Ti2N and Ti2C suggests that Ti2N is a more promising anode material than Ti2C due to its lower diffusion barriers for various cations.
Co-reporter:Zhe Li, Fei Du, Xiaofei Bie, Dong Zhang, Yongmao Cai, Xinran Cui, Chunzhong Wang, Gang Chen, and Yingjin Wei
The Journal of Physical Chemistry C December 30, 2010 Volume 114(Issue 51) pp:22751-22757
Publication Date(Web):December 7, 2010
DOI:10.1021/jp1088788
The Li[Li0.23Co0.3Mn0.47]O2 cathode material was prepared by a sol−gel method. Combinative X-ray diffraction (XRD) and Raman scattering studies showed that the material was a solid solution rather than a composite of nano Li2MnO3 and LiCoO2. The material had a high discharge capacity of 250 mAh g−1 in the voltage window of 2.0−4.8 V. However, the capacity retention was poor. The material showed different electrochemical mechanisms in the first charge and subsequent cycles. Galvanostatic intermittent titration technique (GITT) study showed that the Li+ diffusion coefficients during the first charge were as small as 10−19 cm2 s−1 because of the high kinetic barriers associated with the concurrent Li+ extraction, oxygen loss, and structural rearrangement. The Li+ diffusion coefficients increased to 10−14 cm2 s−1 after the first charge. However, they were still much smaller than those of typical layered materials such as LiCoO2 and Li(Ni1/3Co1/3Mn1/3)O2. Electrochemical impedance spectroscopy (EIS) study showed that the large interface impedance at high potential seriously hindered the electrode performance of the material. A lower charge cutoff voltage of 4.6 V was the most suitable for this material considering that the correponding reversible capacity (∼200 mAh g−1) was attractive for high energy density lithium ion batteries.
Co-reporter:Yuan Meng;Dashuai Wang;Yingying Zhao;Ruqian Lian;Xiaofei Bian;Yu Gao;Fei Du;Bingbing Liu;Gang Chen
Nanoscale (2009-Present) 2017 vol. 9(Issue 35) pp:12934-12940
Publication Date(Web):2017/09/14
DOI:10.1039/C7NR03493H
Ultrathin TiO2-B nanowires with a naked (−110) surface were prepared by a hydrothermal process and used as the anode material for Mg-ion batteries. The material delivered a reversible Mg2+ ion capacity of 110 mA h g−1 at the 0.1C rate. Excellent cycling stability was achieved with a small capacity-fading rate of 0.08% per cycle. In addition, a discharge capacity of 34 mA h g−1 was obtained at the 50C rate, demonstrating the material's excellent high rate capability. First-principles calculations showed that Mg2+ ions hardly penetrated into the TiO2-B lattice because of a very large Mg2+ ion diffusion barrier of 0.63 eV. Instead, the Mg2+ ions were stored at the 4-coordinated vacancies of TiO2-B nanowire (−110) surfaces. The adsorbed Mg2+ ions were bonded with unpaired surface oxygen atoms. Meanwhile, a small amount of electrons were transferred from the O-2p state to the Ti-3d state.
Co-reporter:Xiaofei Bian;Yu Gao;Qiang Fu;Sylvio Indris;Yanming Ju;Yuan Meng;Fei Du;Natalia Bramnik;Helmut Ehrenberg
Journal of Materials Chemistry A 2017 vol. 5(Issue 2) pp:600-608
Publication Date(Web):2017/01/03
DOI:10.1039/C6TA08505A
The practical uses of magnesium-ion batteries are hindered by their poor rate capability and fast capacity decay. Moreover, traditional sodium ion batteries suffer from serious safety problems resulting from the sodium dendrites formed on the anode. In order to circumvent these problems, we designed a highly reversible Na+/Mg2+ hybrid-ion battery composed of a metallic Mg anode, a TiS2 derived titanium sulfide cathode and a 1.0 M NaBH4 + 0.1 M Mg(BH4)2/diglyme hybrid electrolyte. The battery showed remarkable electrochemical performances with a large discharge capacity (200 mA h g−1 at the 1C rate), high rate capability (75 mA h g−1 at the 20C rate) and long cycle life (90% capacity retention after 3000 cycles). Moreover, it exhibited excellent safety properties due to dendrite-free Mg deposition of the anode and the high thermal stability of the cathode. These merits demonstrate the great potential of the reported Na+/Mg2+ hybrid-ion battery for large-scale energy storage.
Co-reporter:Qiang Pang;Yingying Zhao;Xiaofei Bian;Yanming Ju;Xudong Wang;Bingbing Liu;Fei Du;Chunzhong Wang;Gang Chen
Journal of Materials Chemistry A 2017 vol. 5(Issue 7) pp:3667-3674
Publication Date(Web):2017/02/14
DOI:10.1039/C6TA10216F
A graphene@MoS2@TiO2 hybrid material was successfully prepared by a multi-step solution chemistry method. Few-layered MoS2 nanosheets were impregnated into the nanovoids of mesoporous TiO2 microspheres and the composite was further encapsulated by a graphene layer. When used as a negative electrode material for lithium ion batteries, the nanovoids of TiO2 reduced aggregation of MoS2 and suppressed the large volume change of the active material. Moreover, the dissolution and shuttle of polysulfides were effectively suppressed by the hybrid bonding between MoS2 and TiO2. The nano-sized MoS2 and TiO2 particles encapsulated by a high electronic conductive graphene layer improved the charge transfer reaction of the electrode. Due to these merits, the graphene@MoS2@TiO2 showed a large discharge capacity of 980 mA h g−1 at 0.1 A g−1 current density with a capacity retention of 89% after 200 cycles. Moreover, the material delivered 602 mA h g−1 at 2 A g−1 current density, much larger than 91 mA h g−1 for the pristine MoS2. This demonstrated that the hybrid graphene@MoS2@TiO2 microspheres have great potential as a high-performance negative electrode material for lithium ion batteries.
Co-reporter:Yingying Zhao, Zhixuan Wei, Qiang Pang, Yingjin WeiYongmao Cai, Qiang Fu, Fei Du, Angelina SarapulovaHelmut Ehrenberg, Bingbing Liu, Gang Chen
ACS Applied Materials & Interfaces 2017 Volume 9(Issue 5) pp:
Publication Date(Web):January 18, 2017
DOI:10.1021/acsami.6b14196
A carbon-coated Mg0.5Ti2(PO4)3 polyanion material was prepared by the sol–gel method and then studied as the negative electrode materials for lithium-ion and sodium-ion batteries. The material showed a specific capacity of 268.6 mAh g–1 in the voltage window of 0.01–3.0 V vs Na+/Na0. Due to the fast diffusion of Na+ in the NASICON framework, the material exhibited superior rate capability with a specific capacity of 94.4 mAh g–1 at a current density of 5A g–1. Additionally, 99.1% capacity retention was achieved after 300 cycles, demonstrating excellent cycle stability. By comparison, Mg0.5Ti2(PO4)3 delivered 629.2 mAh g–1 in 0.01–3.0 V vs Li+/Li0, much higher than that of the sodium-ion cells. During the first discharge, the material decomposed to Ti/Mg nanoparticles, which were encapsulated in an amorphous SEI and Li3PO4 matrix. Li+ ions were stored in the Li3PO4 matrix and the SEI film formed/decomposed in subsequent cycles, contributing to the large Li+ capacity of Mg0.5Ti2(PO4)3. However, the lithium-ion cells exhibited inferior rate capability and cycle stability compared to the sodium-ion cells due to the sluggish electrochemical kinetics of the electrode.Keywords: anode material; electrochemical properties; lithium ion battery; magnesium titanium phosphate; sodium ion battery;
Co-reporter:Dashuai Wang;Yanhui Liu;Xing Meng;Yingying Zhao;Qiang Pang;Gang Chen
Journal of Materials Chemistry A 2017 vol. 5(Issue 40) pp:21370-21377
Publication Date(Web):2017/10/17
DOI:10.1039/C7TA06944H
First-principles calculations based on density functional theory were carried out to investigate the electrochemical performance of monolayer VS2 for Li-, K-, Mg- and Al-ion batteries. A VS2 monolayer shows differential storage ability for various cations, able to adsorb three layers of Li, two layers of Mg, one layer of K, and 1/9 layer of Al on both sides of the monolayer, producing theoretical capacities of 1397, 1863, 466, and 78 mA h g−1 for Li, Mg, K, and Al, respectively. The average working voltages of VS2 monolayers for Li+, K+ and Mg2+ are close to those of metallic Li, K, and Mg, suggesting that they can be used as anode materials in these rechargeable batteries. The adsorbed cations form a honeycomb-stacking lattice on VS2 monolayers, similar to the plating process of Li, K, and Mg metal anodes. More interestingly, the honeycomb Li lattice is different from the body-centered cubic lattice of a Li metal anode, which provides very small diffusion barriers, resulting in the high rate capability of VS2 monolayer in Li-ion batteries.
Co-reporter:Dashuai Wang;Yu Gao;Yanhui Liu;Yury Gogotsi;Xing Meng;Gang Chen
Journal of Materials Chemistry A 2017 vol. 5(Issue 47) pp:24720-24727
Publication Date(Web):2017/12/05
DOI:10.1039/C7TA09057A
Chloride ion adsorption on Ti2C monolayers was theoretically investigated. Electrochemical parameters, including specific capacity, chloride ion (Cl−) diffusion barrier, and discharge voltage profile, were studied via first-principles calculations. The most favorable Cl− adsorption configuration was identified using a partial particle swarm optimization algorithm and the results showed that Cl− adsorption onto Ti2C monolayers achieved a large theoretical capacity (331 mA h g−1), high working voltage (4.0–3.5 V), and low diffusion barrier (0.22 eV). This resulted in excellent rate capability and a large specific energy of 1269 W h kg−1 at the material level. The effects of terminal O, F, and OH groups on Cl− adsorption onto Ti2C monolayer were also studied, which showed that Cl− could not be adsorbed onto O and F terminated Ti2C monolayers. In comparison, Cl− adsorption onto OH terminated Ti2C was allowed but generated a smaller specific capacity (126 mA h g−1) and lower working voltage (3.5–1.5 V) than a bare Ti2C monolayer.
Co-reporter:Xiaofei Bian, Qiang Fu, Qiang Pang, Yu Gao, Yingjin Wei, Bo Zou, Fei Du, and Gang Chen
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 5) pp:3308
Publication Date(Web):January 22, 2016
DOI:10.1021/acsami.5b11199
The Li(Li0.18Ni0.15Co0.15Mn0.52)O2 cathode material is modified by a Li4M5O12-like heterostructure and a BiOF surface layer. The interfacial heterostructure triggers the layered-to-Li4M5O12 transformation of the material which is different from the layered-to-LiMn2O4 transformation of the pristine Li(Li0.18Ni0.15Co0.15Mn0.52)O2. This Li4M5O12-like transformation helps the material to keep high working voltage, long cycle life and excellent rate capability. Mass spectrometry, in situ X-ray diffraction and transmission electron microscope show that the Li4M5O12-like phase prohibits oxygen release from the material bulk at elevated temperatures. In addition, the BiOF coating layer protects the material from harmful side reactions with the electrolyte. These advantages significantly improve the electrochemical performance of Li(Li0.18Ni0.15Co0.15Mn0.52)O2. The material shows a discharge capacity of 292 mAh g–1 at 0.2 C with capacity retention of 92% after 100 cycles. Moreover, a high discharge capacity of 78 mAh g–1 could be obtained at 25 C. The exothermic temperature of the fully charged electrode is elevated from 203 to 261 °C with 50% reduction of the total thermal release, highlighting excellent thermal safety of the material.Keywords: electrochemical properties; Li-excess layered oxide; lithium ion battery; surface modification; thermal safety
Co-reporter:Yongquan Zhang, Yuan Meng, Kai Zhu, Hailong Qiu, Yanming Ju, Yu Gao, Fei Du, Bo Zou, Gang Chen, and Yingjin Wei
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 12) pp:7957
Publication Date(Web):March 10, 2016
DOI:10.1021/acsami.5b10766
Pristine and Cu-doped TiO2–B nanowires are synthesized by the microwave assisted hydrothermal method. The doped oxide exhibits a highly porous structure with a specific surface area of 160.7 m2 g–1. As evidenced by X-ray photoelectron spectroscopy and X-ray energy dispersive spectroscopy, around 2.0 atom % Cu2+ cations are introduced into TiO2–B, which leads to not only a slightly expanded lattice network but also, more importantly, a modified electronic structure. The band gap of TiO2–B is reduced from 2.94 to 2.55 eV, resulting in enhanced electronic conductivity. Cyclic voltammetry and electrochemical impedance spectroscopy reveal improved electrochemical kinetic properties of TiO2–B due to the Cu doping. The doped nanowires show a specific capacity of 186.8 mAh g–1 at the 10 C rate with a capacity retention of 64.3% after 2000 cycles. Remarkably, our material exhibits a specific capacity of 150 mAh g–1 at the 60 C rate, substantiating its superior high rate capability for rechargeable lithium batteries.Keywords: anode material; copper doping; electrochemical properties; lithium ion batteries; titanium dioxide bronze
Co-reporter:Rongyu Zhang, Xu Yang, Yu Gao, Yanming Ju, Hailong Qiu, Xing Meng, Gang Chen, Yingjin Wei
Electrochimica Acta 2016 Volume 188() pp:254-261
Publication Date(Web):10 January 2016
DOI:10.1016/j.electacta.2015.12.014
Carbon nanofibers are in-situ prepared in carbon coated Li3V2(PO4)3 by the chemical vapor deposition method. The carbon nanofibers connect the isolated Li3V2(PO4)3 regions thus constructing an efficient conductive network for electrons transportation. In addition, incorporation of the surface carbon coating and carbon nanofibers promotes the electrochemical kinetic properties of the material which improves the electrochemical performance of Li3V2(PO4)3. In all materials under investigation, the one containing 6.4 wt% carbon nanofibers shows excellent cycle stability resulting in capacity retention of 90.5% after 300 cycles. Moreover, a large discharge capacity of 94.7 mAh g−1 is obtained at the 20C rate highlighting excellent rate capability of the material.
Co-reporter:Zhendong Guo, Dong Zhang, Hailong Qiu, Yanming Ju, Tong Zhang, Lijie Zhang, Yuan Meng, Yingjin Wei and Gang Chen
RSC Advances 2016 vol. 6(Issue 8) pp:6523-6527
Publication Date(Web):12 Jan 2016
DOI:10.1039/C5RA24488A
Poly-dopamine coated Li1−xFeSO4F is prepared via a self-polymerization process. The material shows larger discharge capacities, better rate capability and longer cycle stability than the pristine LiFeSO4F. The improved electrochemical properties are attributed to the highly hydrophilic and elastic properties of poly-dopamine.
Co-reporter:Xiaofei Bian, Qiang Fu, Hailong Qiu, Fei Du, Yu Gao, Lijie Zhang, Bo Zou, Gang Chen, and Yingjin Wei
Chemistry of Materials 2015 Volume 27(Issue 16) pp:5745
Publication Date(Web):August 3, 2015
DOI:10.1021/acs.chemmater.5b02331
The continuous phase transformation to spinel LiMn2O4 seriously hinders the electrochemical properties of Li-excess layered oxides in lithium ion batteries. Herein, we prepared a heterostructured Li-excess layered cathode material consisting of a Li(Li0.18Ni0.15Co0.15Mn0.52)O2 active material in conjunction with a surface Li4M5O12 spinel and a Li2O-LiBO2–Li3BO3 glass coating layer. The material showed improved electrochemical kinetic properties with respect to its pristine counterpart because the Li2O–LiBO2–Li3BO3 glass layer not only improved the ionic conductivity of the material but also depressed the side reactions of the electrode with the electrolyte. In addition, the surface Li4M5O12 spinel constantly grew inward the bulk of the material during long-term charge–discharge cycling instead of the conventional LiMn2O4 transformation for the pristine Li(Li0.18Ni0.15Co0.15Mn0.52)O2. As a result, the heterostructured cathode material showed overall improved electrochemical performance. An initial discharge capacity of 258.8 mAh g–1 was obtained at the 0.2 C rate with remarkable capacity retention of 92.2% after 100 cycles. Moreover, the material showed excellent rate capacity delivering a high discharge capacity of 130.4 mAh g–1and 100.4 mAh g–1 at the 10 and 20 C rates, respectively. Differential scanning calorimetry showed that the exothermic temperature of the fully charged electrode was elevated to 324.2 °C with little thermal release of 232.5 J g–1, demonstrating good thermal safety of the material.
Co-reporter:Yongquan Zhang, Qiang Fu, Qiaoling Xu, Xiao Yan, Rongyu Zhang, Zhendong Guo, Fei Du, Yingjin Wei, Dong Zhang and Gang Chen
Nanoscale 2015 vol. 7(Issue 28) pp:12215-12224
Publication Date(Web):15 Jun 2015
DOI:10.1039/C5NR02457A
N-doped TiO2-B nanowires are prepared by the solvothermal method using TiN nanoparticles as the starting material. X-ray photoelectron spectroscopy shows that the N dopants preferentially occupy the interstitial sites of TiO2-B up to a content of ∼0.55 at%. Above this critical value, the N dopants will substitute the oxygen atoms which improve the electronic conductivity of TiO2-B. The maximum proportion of substituted-N in the TiO2-B nanowires is ∼1.3 at%. Raman scattering shows that the substituted-N strengthens the Ti(1)–O1–Ti(2) and O1–Ti(1)–O3 bonds of TiO2-B. This improves the stability of the corresponding local structures, thus reducing the distortion of the Li+ diffusion channel along the b-axis of TiO2-B. As a result, the substituted-N has more of an impact on the electrochemical properties of TiO2-B than the interstitial-N does. The TiO2-B nanowires containing substituted-N dopants exhibit a remarkably enhanced electrochemical performance compared to pure TiO2-B. They show a discharge capacity of 153 mA h g−1 at the 20 C rate with a capacity retention of 76% after 1000 cycles. In addition, they can deliver a discharge capacity of 100 mA h g−1 at an ultra-high rate of 100 C, indicating their great potential in high power lithium ion batteries.
Co-reporter:Kai Zhu, Shaohua Guo, Jin Yi, Songyan Bai, Yingjin Wei, Gang Chen and Haoshen Zhou
Journal of Materials Chemistry A 2015 vol. 3(Issue 44) pp:22012-22016
Publication Date(Web):08 Oct 2015
DOI:10.1039/C5TA05444C
A new layered Na0.3MoO2 exhibits a reversible capacity of 146 mA h g−1, remarkable cycling stability and good rate capability for sodium half-cells. And a Na0.3MoO2//Na0.8Ni0.4Ti0.6O2 full intercalation-type sodium-ion cell is fabricated and it displays an excellent cycling stability. These results indicate that molybdenum-based oxide is a promising anode material for sodium-ion batteries.
Co-reporter:Xiao Yan, Yanjuan Li, Malin Li, Yongcheng Jin, Fei Du, Gang Chen and Yingjin Wei
Journal of Materials Chemistry A 2015 vol. 3(Issue 8) pp:4180-4187
Publication Date(Web):14 Jan 2015
DOI:10.1039/C4TA06361A
A TiO2–bronze/N-doped graphene nanocomposite (TiO2–B/NG) is prepared by a facile hydrothermal combined with hydrazine monohydrate vapor reduction method. The material exhibits macro- and meso-porosity with a high specific surface area of 163.4 m2 g−1. X-Ray photoelectron spectroscopy confirms the successful doping of nitrogen in the graphene sheets. In addition, the TiO2–B nanowires are substantially bonded to the NG sheets. Cyclic voltammetry and electrochemical impedance spectroscopy show that the N-doped graphene improves the electron and Li ion transport in the electrode which results in better electrochemical kinetics than that of the pristine TiO2–B nanowires. As a result, the charge transfer resistance of the TiO2–B/NG electrode is significantly reduced. In addition, the lithium diffusion coefficient of TiO2–B/NG increases by about five times with respect to that of pristine TiO2–B. The TiO2–B/NG composite exhibits a remarkably enhanced electrochemical performance compared to that of TiO2–B. It shows a discharge capacity of 220.7 mA h g−1 at the 10C rate with a capacity retention of 96% after 1000 cycles. In addition, it can deliver a discharge capacity of 101.6 mA h g−1 at an ultra high rate of 100C, indicating its great potential for use in high power lithium ion batteries.
Co-reporter:Zhendong Guo, Dong Zhang, Hailong Qiu, Tong Zhang, Qiang Fu, Lijie Zhang, Xiao Yan, Xing Meng, Gang Chen, and Yingjin Wei
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 25) pp:13972
Publication Date(Web):June 11, 2015
DOI:10.1021/acsami.5b02966
Tavorite LiFeSO4F has been regarded as a promising alternative to LiFePO4 due to its high Li ionic conductivity. To overcome the low electronic conductivity of LiFeSO4F, we prepared a graphene oxide (GO)/LiFeSO4F composite material by the solvothermal method. The GO wraps on the surface of LiFeSO4F and links the adjacent particles, thus providing an effective network for electrons transport. As a result, the electronic conductivity of the material is improved from 8.16 × 10–11 S cm–1 to 1.65 × 10–4 S cm–1. In addition, the GO depresses the side reactions of the electrode and electrolyte, promotes the charge transfer reactions at the electrode/electrolyte interface, and facilitates the lithium diffusion in the electrode. The GO-wrapped LiFeSO4F exhibits much better electrochemical performance than the pristine material. It showed a discharge capacity of 113.2 mAh g–1 at the 0.1 C rate with 99% capacity retention after 100 cycles. In addition, the material is able to deliver 85.1, 73.4, and 30.3 mAh g–1 at high current rates of 1 C, 2 C, and 10 C, respectively.Keywords: cathode material; electrochemical performance; graphene oxide; lithium ion batteries; lithium iron sulfate fluoride;
Co-reporter:Rongyu Zhang, Xu Yang, Dong Zhang, Hailong Qiu, Qiang Fu, Hui Na, Zhendong Guo, Fei Du, Gang Chen, Yingjin Wei
Journal of Power Sources 2015 Volume 285() pp:227-234
Publication Date(Web):1 July 2015
DOI:10.1016/j.jpowsour.2015.03.100
•ZnFe2O4 nano particles were prepared by the glycine-nitrate combustion method.•SBR/CMC water soluble binder was used to prepare ZnFe2O4 anode electrode.•Excellent cycle stability and rate capability were obtained using SBR/CMC.•SBR/CMC is more promising than PVDF for the ZnFe2O4 anode electrode.ZnFe2O4 nano particles as an anode material for lithium ion batteries are prepared by the glycine-nitrate combustion method. The mixture of styrene butadiene rubber and sodium carboxyl methyl cellulose (SBR/CMC) with the weight ratio of 1:1 is used as the binder for ZnFe2O4 electrode. Compared with the conventional polyvinylidene-fluoride (PVDF) binder, the SBR/CMC binder is much cheaper and environment benign. More significantly, this water soluble binder significantly improves the rate capability and cycle stability of ZnFe2O4. A discharge capacity of 873.8 mAh g−1 is obtained after 100 cycles at the 0.1C rate, with a very little capacity fading rate of 0.06% per cycle. Studies show that the SBR/CMC binder enhances the adhesion of the electrode film to the current collector, and constructs an effective three-dimensional network for electrons transport. In addition, the SBR/CMC binder helps to form a uniform SEI film thus prohibiting the formation of lithium dendrite. Electrochemical impedance spectroscopy shows that the SBR/CMC binder lowers the ohmic resistance of the electrode, depresses the formation of SEI film and facilitates the charge transfer reactions at the electrode/electrolyte interface. These advantages highlight the potential applications of SBR/CMC binder in lithium ion batteries.
Co-reporter:Qiang Pang, Qiang Fu, Yuhui Wang, Yongquan Zhang, Bo Zou, Fei Du, Gang Chen, Yingjin Wei
Electrochimica Acta 2015 Volume 152() pp:240-248
Publication Date(Web):10 January 2015
DOI:10.1016/j.electacta.2014.11.142
•RuO2 modified LiNi0.5Mn1.5O4 cathode materials are prepared successfully.•RuO2 modification improves the electrochemical kinetics of LiNi0.5Mn1.5O4.•The modified materials showed excellent electrochemical performance.A series of RuO2 modified LiNi0.5Mn1.5O4 materials are successfully prepared by the precipitation method. X-ray photoelectron spectroscopy confirms the presence of Ru4+ in the materials. Scanning electron microscope and high resolution transmission electron microscope show that RuO2 covers the surface of LiNi0.5Mn1.5O4 particles. The amounts of RuO2 in the materials are determined to be 1.6 wt.%, 2.0 wt.% and 3.0 wt.%, respectively. The electrochemical kinetics of the materials is studied by cyclic voltammetry and electrochemical impedance spectroscopy. The results show that RuO2 modification decreases the polarization of the electrode, prevents the side reactions of the electrode and the electrolyte, and improves the charge transfer reactions at the electrode interface, all of which are beneficial for the electrochemical properties of LiNi0.5Mn1.5O4. In all samples tested, the one containing 2.0 wt.% of RuO2 exhibits superior electrochemical performance. It shows discharge capacities of 131.7 mAh g−1 (room temperature) and 129.7 mAh g−1 (60 °C) at the 0.5 C rate with the corresponding capacity retention of 97.7% and 97.2% after 100 cycles. In addition, the material delivers high discharge capacities of 104.5 mAh g−1at the 5 C rate and 66.1 mAh g−1 at the 10 C rate, demonstrating its excellent rate capability.
Co-reporter:Xiaofei Bian, Qiang Fu, Chengguang Qiu, Xiaofei Bie, Fei Du, Yuhui Wang, Yongquan Zhang, Hailong Qiu, Gang Chen, Yingjin Wei
Materials Chemistry and Physics 2015 Volume 156() pp:69-75
Publication Date(Web):15 April 2015
DOI:10.1016/j.matchemphys.2015.02.024
•CB/VGCFs binary conductive additive is used for Li-excess layered cathode electrode.•The binary conductive additive constructs a continuous network for electron transport.•The binary conductive additive improves the electrochemical kinetics of the electrode.•Improved electrochemical performance is gained using the binary conductive additive.Carbon black (CB) and vapor-grown carbon fibers (VGCFs) are used as conductive additives for the Li1.18Co0.15Ni0.15Mn0.52O2 electrodes for Li-ion batteries. The fibrous VGCFs can bridge the isolated Li1.18Ni0.15Co0.15Mn0.52O2 regions, thus construct an effective conductive network for electron transport. In addition, incorporation of CB and VGCFs can improve the electrochemical kinetics of the cathode material by retarding the harmful side reactions, promoting the charge transfer reactions and increasing the apparent lithium diffusion coefficient. In all electrodes under investigation, the one prepared with 3 wt.% of VGCFs and 12 wt.% of CB shows the largest discharge capacity of 252 mAh g−1 at the 0.2C rate with excellent capacity retention and rate capability.
Co-reporter:Kai Zhu;Hailong Qiu;Yongquan Zhang;Dr. Dong Zhang;Dr. Gang Chen;Dr. Yingjin Wei
ChemSusChem 2015 Volume 8( Issue 6) pp:1017-1025
Publication Date(Web):
DOI:10.1002/cssc.201500027
Abstract
A series of V2O5-based cathode materials that include V2O5 and Al0.14V2O5 nanoparticles, V2O5/reduced graphene oxide (RGO), and Al0.16V2O5/RGO nanocomposites are prepared by a simple soft chemical method. XRD and Raman scattering show that the Al ions reside in the interlayer space of the materials. These doping ions strengthen the VO bonds of the [VO5] unit and enhance the linkage of the [VO5] layers, which thus increases the structural stability of V2O5. SEM and TEM images show that the V2O5 nanoparticles construct a hybrid structure with RGO that enables fast electron transport in the electrode matrix. The electrochemical properties of the materials are studied by charge–discharge cycling, cyclic voltammetry, and electrochemical impedance spectroscopy. Of all the materials tested, the one that contained both Al ions and RGO (Al0.16V2O5/RGO) exhibited the highest discharge capacity, the best rate capability, and excellent capacity retention. The superior electrochemical performance is attributed to the synergetic effects of Al3+ doping and RGO modification, which not only increase the structural stability of the V2O5 lattice but also improve the electrochemical kinetics of the material.
Co-reporter:Xiao Yan, Yanjuan Li, Fei Du, Kai Zhu, Yongquan Zhang, Anyu Su, Gang Chen and Yingjin Wei
Nanoscale 2014 vol. 6(Issue 8) pp:4108-4116
Publication Date(Web):29 Jan 2014
DOI:10.1039/C3NR06393C
A facile microwave solvothermal process is developed to prepare an anatase TiO2 anode material that maintains multiple properties including high surface area, high crystallinity, uniform mesoporous, perfect microspheres and uniform particle size. Using this fine anatase TiO2 product, a TiO2/RGO (RGO: reduced graphene oxide) hybrid material is prepared under UV-light irradiation. Incorporation of RGO improves the electrochemical kinetics of the TiO2 microspheres, which results in superior electrochemical performance in terms of specific capacity, rate capability and cycle stability. The material shows a discharge capacity of 155.8 mA h g−1 at the 5 C rate. Even at the 60 C rate, a high discharge capacity of 83.6 mA h g−1 is still obtained which is two times higher than that of pristine mesoporous TiO2.
Co-reporter:Qiang Fu, Fei Du, Xiaofei Bian, Yuhui Wang, Xiao Yan, Yongquan Zhang, Kai Zhu, Gang Chen, Chunzhong Wang and Yingjin Wei
Journal of Materials Chemistry A 2014 vol. 2(Issue 20) pp:7555-7562
Publication Date(Web):25 Feb 2014
DOI:10.1039/C4TA00189C
Li1.18Co0.15Ni0.15Mn0.52O2 cathode material was prepared by the sol–gel method. The material was coated with the ionic conductor Li3VO4via direct reaction with NH4VO3 at 350 °C. The Li3VO4 coated material had a higher ordered hexagonal layered structure, and less Li+/Ni2+ cation mixing. The surface of the coated material was composed of Li3VO4 polycrystals, which were impregnated into the bulk of the active material. The surface coating protected the material from contact with CO2 in the air, thus inhibiting the formation of an Li2CO3 layer. Electrochemical studies showed that the Li3VO4 surface coating improved the activation of Mn4+ ions, resulting in a high discharge capacity. It also prohibited the growth of a solid electrolyte interface film, and facilitated the charge transfer reactions at the electrode/electrolyte interface, thus improving the rate capability and cycle stability of the material. DSC analysis of the fully charged electrode showed that the temperature of the exothermic peak increased from 205.2 °C to 232.8 °C, and that the amount of heat that was released was reduced from 807.5 J g−1 to 551.0 J g−1, highlighting the improved thermal stability of the material after coating with Li3VO4 .
Co-reporter:Yongquan Zhang, Fei Du, Xiao Yan, Yuming Jin, Kai Zhu, Xue Wang, Haoming Li, Gang Chen, Chunzhong Wang, and Yingjin Wei
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 6) pp:4458
Publication Date(Web):March 5, 2014
DOI:10.1021/am5002053
Pure anatase TiO2 and N-doped TiO2 nanoparticles were prepared by a solvothermal method. X-ray photoelectron spectroscopy showed that the surface of the doped material was dominated by interstitial N, while interstitial and substitutional N coexisted in the material bulk. Both materials showed superior cycle stability. In addition, the N-doped material exhibited much better rate capability than pure TiO2. A discharge capacity of 45 mAh g–1 was obtained at the 15 C rate, which was 80% higher than that of pure TiO2. The electrochemical kinetic properties of the materials were studied by a galvanostatic intermittent titration technique and electrochemical impedance spectroscopy. The charge-transfer resistance of TiO2 was decreased by N doping. Meanwhile, the minimum lithium diffusion coefficient was increased to 2.14 × 10–11 cm2 s–1, which is 13 times higher than that of pure TiO2. This indicates that the electrochemical kinetic properties of TiO2 were improved by N doping, which substantially improved the specific capacity and rate capability of TiO2.Keywords: anatase titanium dioxide; electrochemical kinetic properties; lithium-ion battery; N doping; rate capability;
Co-reporter:Rongyu Zhang, Yongquan Zhang, Kai Zhu, Fei Du, Qiang Fu, Xu Yang, Yuhui Wang, Xiaofei Bie, Gang Chen, and Yingjin Wei
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 15) pp:12523
Publication Date(Web):July 10, 2014
DOI:10.1021/am502387z
RuO2 nanocrystals are successfully impregnated into the surface carbon layer of the Li3V2(PO4)3/C cathode material by the precipitation method. Transmission electron microscopy shows that the RuO2 particles uniformly embed in the surface carbon layer. Cyclic voltammetry and electrochemical impedance spectroscopy indicate that the coexistence of carbon and RuO2 enables high conductivity for both Li ions and electrons and thus stabilizes the interfacial properties of the electrode, facilitates the charge transfer reactions, and improves the Li+ diffusion in the electrode. As a result, the Li3V2(PO4)3 cathode coated with the binary surface layer shows improved rate capability and cycle stability. Particularly, the material containing 2.4 wt % Ru exhibits the best electrochemical performance and delivers a discharge capacity of 106 mAh g–1 at the 10 C rate with a capacity retention of 98.4% after 100 cycles.Keywords: charge−discharge cycling; lithium vanadium phosphate; lithium-ion battery; rate performance; ruthenium dioxide; surface coating
Co-reporter:Xiao Yan, Yongquan Zhang, Kai Zhu, Yu Gao, Dong Zhang, Gang Chen, Chunzhong Wang, Yingjin Wei
Journal of Power Sources 2014 Volume 246() pp:95-102
Publication Date(Web):15 January 2014
DOI:10.1016/j.jpowsour.2013.07.072
•TiO2(B) nanoribbons were prepared by freeze-drying assisted hydrothermal process.•SBR/CMC water binder was first used to prepare TiO2(B) anode electrode.•Excellent capacity retention and rate performance were obtained using SBR/CMC.•SBR/CMC is more promising than PVDF for preparation of TiO2(B) anode electrode.TiO2(B) anode for lithium-ion batteries is prepared by the hydrothermal method. The styrene butadiene rubber and sodium carboxyl methyl cellulose (SBR/CMC) and polyvinylidene fluoride (PVDF) binders are used to prepare the TiO2(B) electrodes. Scanning electron microscope and electrochemical impedance spectroscopy show that the electrode prepared with SBR/CMC has better electrode maintainability and electrochemical kinetics which result in better electrochemical performance. The optimized SBR/CMC binder content is proposed to be in the range of 12–15 wt%. In addition, the 1 M LiPF6 electrolyte dissolved in EC:DMC = 3:7 is more suitable for the TiO2(B) electrode. Using this suggested binder content and electrolyte, the TiO2(B) material exhibits superior capacity retention and rate capability. Even at the 10 C rate, the material still shows a discharge capacity of 142.5 mAh g−1 which keeps very well after 800 cycles. Based on this work, it is concluded that SBR/CMC is a promising binder for the TiO2(B) anode which provides not only better electrochemical performance but also more cheaper and environmental friendly than PVDF.
Co-reporter:Yuhui Wang, Xiao Yan, Xiaofei Bie, Qiang Fu, Fei Du, Gang Chen, Chunzhong Wang, Yingjin Wei
Electrochimica Acta 2014 Volume 116() pp:250-257
Publication Date(Web):10 January 2014
DOI:10.1016/j.electacta.2013.10.215
Li-excess Li[Li0.18Ni0.15Co0.15Mn0.52]O2 layered cathode material is prepared by the sol-gel method. The material is aged in a LiPF6 based electrolyte and then is subjected to a series of structural and electrochemical analyses. X-ray diffraction shows that aging in electrolyte does not change the C2/m ordering of the material crystal lattice. But the surface of the material is etched by the electrolyte which is confirmed by transmission electron microscope and Raman scattering. This causes dissolution of some transition metal elements (especially Ni and Co) and formation of a spinel-like surface layer. Also, some by-products resulted from the electrolyte decomposition are detected on the surface of the material. Electrochemical impedance spectroscopy shows that aging in electrolyte severely hinders the electrochemical kinetics of the material. Cyclic voltammetry indicates that the aged sample has large electrode polarization which prevents the oxygen loss process and the activation of Mn4+ ions. As a result, the discharge capacity of the aged sample continuously increases from 134 mAh g−1 to 215 mAh g−1 in the initial several cycles.
Co-reporter:Lina Liu;Xiao Yan;Yuhui Wang;Dong Zhang;Fei Du;Chunzhong Wang;Gang Chen
Ionics 2014 Volume 20( Issue 8) pp:1087-1093
Publication Date(Web):2014 August
DOI:10.1007/s11581-013-1055-2
A series of LiNi1/3Co1/3Mn1/3O2/LiFePO4 composite cathodes with the LiFePO4 mass content ranging from 10 to 30 wt% were prepared by ball milling in order to combine the merits of layered LiNi1/3Co1/3Mn1/3O2 and olivine LiFePO4. The structure and morphology of the samples were characterized by X-ray diffraction and scanning electron microscope. The composite cathodes exhibited improved electrochemical performance compared with pristine LiNi1/3Co1/3Mn1/3O2. Among all the composite cathodes, the one with 20 wt% of LiFePO4 showed the best electrochemical performance in terms of discharge capacity, cycle stability, and rate capability. Electrochemical impedance spectroscopy showed that mixing of LiFePO4 in LiNi1/3Co1/3Mn1/3O2 decreased the internal resistance of the electrode, retarded the formation of SEI film, and facilitated the charge transfer reaction. Differential scanning calorimetry showed that the composite cathode had better thermal stability than pristine LiNi1/3Co1/3Mn1/3O2.
Co-reporter:Kai Zhu;Xiao Yan;Yongquan Zhang;Yuhui Wang;Anyu Su;Dr. Xiaofei Bie;Dr. Dong Zhang;Dr. Fei Du;Dr. Chunzhong Wang;Dr. Gang Chen;Dr. Yingjin Wei
ChemPlusChem 2014 Volume 79( Issue 3) pp:447-453
Publication Date(Web):
DOI:10.1002/cplu.201300331
Abstract
H2V3O8 nanowires wrapped by reduced graphene oxide (RGO) are synthesized successfully through a simple hydrothermal process. The structural properties of the samples are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman scattering, and X-ray photoelectron spectroscopy. The RGO nanosheets modify the surfaces of the H2V3O8 nanowires through VC linkages. The H2V3O8/RGO composite exhibits a remarkably enhanced electrochemical performance in terms of its reversible capacity, cyclic performance, and rate capability. The material shows high discharge capacities of 256 and 117 mA h g−1 at the current densities of 0.1 and 1 A g−1, respectively, with almost no capacity fading after fifty charge/discharge cycles. Cyclic voltammetry and electrochemical impedance spectroscopy show that the superior electrochemical performance of H2V3O8/RGO can be attributed to the cooperation of RGO, which provides better mechanical flexibility, higher electronic conductivity, and smaller charge-transfer resistance.
Co-reporter:Xiaofei Bie, Fei Du, Yuhui Wang, Kai Zhu, Helmut Ehrenberg, Kristian Nikolowski, Chunzhong Wang, Gang Chen, Yingjin Wei
Electrochimica Acta 2013 Volume 97() pp:357-363
Publication Date(Web):1 May 2013
DOI:10.1016/j.electacta.2013.02.131
LiNi0.33Co0.33Mn0.33O2 which was synthesized by co-precipitation method has been used to investigate the relationships between crystal/interfacial structures and electrochemical performance of the material in the voltage range of 2.5–4.6 V. X-ray diffraction showed that the material maintained high structural stability with charge–discharge cycling. Formation of SEI film was observed by transmission electron microscopy. The chemical compositions of the SEI film were analyzed by X-ray photoelectron spectroscopy, which were mainly composed of some organic compounds such as lithium alkyl carbonate RCH2OCO2Li, as well as some inorganic compounds such as LixPFy and LixPOyFz. Transmission electron microscopy showed that the SEI film gradually grew to a thickness of about 40 nm after 30 cycles. This caused larger and larger interfacial resistance with charge–discharge cycling, which has been attributed to the continuous capacity fading of LiNi0.33Co0.33Mn0.33O2 in the voltage window of 2.5–4.6 V.
Co-reporter:Fei Du;Xiao-fei Bie;Xiao-fei Bian;Fang Hu
Chemical Research in Chinese Universities 2013 Volume 29( Issue 2) pp:210-213
Publication Date(Web):2013 April
DOI:10.1007/s40242-013-2159-y
A typical Li+ substituted NiO compound, Li0.29Ni0.71O, was synthesized by molten nitrate method. The effects of Li+ substitution on the structure and magnetic properties of NiO were investigated. X-Ray diffraction(XRD), scanning electron microscope(SEM) and high-resolution transmission electron microscope(HRTEM) analyses confirm the cubic structure of Li0.29Ni0.71O, with a primary particle size of 150 nm. Analysis of the Ni X-ray photoelectron spectroscopy(XPS) shows the transformation from Ni2+ to Ni3+ induced by Li+ substitution. Two magnetic transitions were observed at 225 and 55 K which were assigned to the ferrimagnetic ordering and spin glass transition, respectively. The different magnetic behavior with respect to that of NiO was attributed to the break of superexchange interaction Ni2+-O-Ni2+ and the formation of different spin clusters after non-magnetic Li+ doping.
Co-reporter:Yuhui Wang ; Xiaofei Bie ; Kristian Nikolowski ; Helmut Ehrenberg ; Fei Du ; Manuel Hinterstein ; Chunzhong Wang ; Gang Chen
The Journal of Physical Chemistry C 2013 Volume 117(Issue 7) pp:3279-3286
Publication Date(Web):January 17, 2013
DOI:10.1021/jp311518r
Li-excess cathode material, Li1.13Ni0.3Mn0.57O2, was synthesized by the sol–gel method. The material has a reversible discharge capacity of 200 mAh g–1 at a current density of 40 mA g–1. In situ synchrotron X-ray diffraction, electrochemical impedance spectroscopy (EIS), and the galvanostatic intermittent titration technique (GITT) were applied to study the relationships between structural changes and electrochemical kinetics of Li1.13Ni0.3Mn0.57O2 during the first charge. When the charging potential was below 4.4 V, the c/a structural parameter of the material gradually increased, resulting in a higher layered character. The lithium diffusion coefficients during this process were about 10–14 cm2 s–1. When the charging potential was increased to 4.8 V, the bulk of the material was still maintained in a layered structure with space group symmetry R3̅m. The lithium diffusion coefficient and the charge transfer kinetics rapidly decreased because of the high kinetic barriers associated with concurrent Li+ extraction, oxygen loss, and structural rearrangement. Both the lithium diffusion coefficient and the charge transfer kinetics show further decrease at the end of the first charge, indicating severely sluggish kinetics of the “Li-poor” Li1.13–xNi0.3Mn0.57O2 phase.
Co-reporter:Yongsheng Chen, Dong Zhang, Xiaofei Bian, Xiaofei Bie, Chunzhong Wang, Fei Du, Myongsu Jang, Gang Chen, Yingjin Wei
Electrochimica Acta 2012 Volume 79() pp:95-101
Publication Date(Web):30 September 2012
DOI:10.1016/j.electacta.2012.06.082
Carbon coated monoclinic Li3V2(PO4)3 cathode material was prepared by the carbothermal reduction method. Raman scattering showed the amorphous nature of the residual carbon in the material. HRTEM and XPS showed that a small amount of carbon penetrated into the Li3V2(PO4)3 crystallites to form a surface carbon layer with thickness about 5–10 nm. The material showed a reversible discharge capacity of 120 mAh g−1 (C/4 rate), 115 mAh g−1 (1C rate) and 110 mAh g−1 (2C rate) in the voltage window of 3.0–4.3 V, which kept excellent cycle stability in 300 cycles. The material suffered from capacity loss in the initial ten charge–discharge cycles. The irreversible capacity loss was mainly related to the progressive formation of a solid electrolyte interface (SEI) film which was clearly observed by HRTEM. FTIR analysis showed that the chemical species of the SEI film mainly contained some organic compounds such as ROCO2Li, RCO2Li, and aliphatic, as well as some inorganic compounds such as Li2CO3, LixPFy or LixPOyFz. The SEI film tended to be stabilized in the initial several cycles, which led to excellent electrochemical performance during long term cycling.Graphical abstractThe progressive formation of a solid electrolyte interface (SEI) film on carbon coated Li3V2(PO4)3 was observed by combinative techniques. An appropriate amount of SEI film is helpful for the material to maintain excellent performance during long term cycling.Highlights► Li3V2(PO4)3/C cathode material that prepared by the CTR method shows excellent electrochemical performance over 300 cycles. ► The formation of SEI film is confirmed by HRTEM, FTIR and EIS analysis. ► A proper amount of SEI film is helpful for the electrochemical performance of Li3V2(PO4)3.
Co-reporter:Zhe Li, Yuhui Wang, Xiaofei Bie, Kai Zhu, Chunzhong Wang, Gang Chen, Yingjin Wei
Electrochemistry Communications 2011 Volume 13(Issue 9) pp:1016-1019
Publication Date(Web):September 2011
DOI:10.1016/j.elecom.2011.06.031
The electrochemical properties of Li[Li0.2Co0.4Mn0.4]O2 were studied at room temperature and − 20 °C. EIS study showed that the electrochemical kinetics of the first charge was more sluggish than subsequent cycles, which became even worse at − 20 °C. This made it difficult for the material to achieve a sufficient oxygen loss reaction at low temperature. XPS analysis showed that almost all of the Mn4+ ions in the material were activated at room temperature, whereas only a few of them were activated at − 20 °C. As a result, the material showed a high discharge capacity of 246 mAh g−1 at room temperature, comparing to the 155 mAh g− 1 at − 20 °C. However, the inactive Mn4+ ions in the electrode suppressed the dissolution of manganese and the Jahn–Teller distortion of the material lattice, both of which resulted in excellent cycle life at low temperature.Highlights► Low temperature electrochemical properties of Li-riched layered cathode materials. ► The loss of oxygen and activation of Mn4+ are strongly temperature dependent. ► Li[Li0.2Co0.4Mn0.4]O2 shows a high discharge capacity of 155 mAh g− 1 at − 20 °C ► The excellent cycle life at low temperature is due to the high concentration of Mn4+ in the electrode.
Co-reporter:Yongmao Cai, Gang Chen, Xiaoguang Xu, Fei Du, Zhe Li, Xing Meng, Chunzhong Wang, and Yingjin Wei
The Journal of Physical Chemistry C 2011 Volume 115(Issue 14) pp:7032-7037
Publication Date(Web):March 21, 2011
DOI:10.1021/jp111310g
Systematic first-principles calculations based on the density functional theory are carried out to discuss the crystal and electronic structures of the LiMSO4F/MSO4F (M = Fe, Co, and Ni) systems. It is shown that all of the LiMSO4F compounds are in a high spin antiferromagnetic ground state. However, they transform to different ground states with Li+ extraction. LiFeSO4F is a typical Mott-Hubbard insulator and then transforms to a charge-transfer insulator with Li+ extraction. The theoretical intercalation voltages of LiMSO4F are 3.54 (Fe), 4.73 (Co), and 5.16 V (Ni), respectively, which are close to corresponding LiMPO4 phosphates. First-principles calculations show that a significant amount of electron-charge transfer takes place on the oxygen anions with Li+ extraction, especially for LiCoSO4F and LiNiSO4F. This will lead to significant loss of oxygen from the material lattice which is an intrinsic drawback of LiMSO4F due to the concerns of structural and thermal stabilities.
Co-reporter:Tao Jiang, Wencheng Pan, Jian Wang, Xiaofei Bie, Fei Du, Yingjin Wei, Chunzhong Wang, Gang Chen
Electrochimica Acta 2010 Volume 55(Issue 12) pp:3864-3869
Publication Date(Web):30 April 2010
DOI:10.1016/j.electacta.2010.02.026
Carbon coated Li3V2(PO4)3 cathode material was prepared by a poly(vinyl alcohol) (PVA) assisted sol–gel method. PVA was used both as the gelating agent and the carbon source. XRD analysis showed that the material was well crystallized. The particle size of the material was ranged between 200 and 500 nm. HRTEM revealed that the material was covered by a uniform surface carbon layer with a thickness of 80 Å. The existence of surface carbon layer was further confirmed by Raman scattering. The electrochemical properties of the material were investigated by charge–discharge cycling, CV and EIS techniques. The material showed good cycling performance, which had a reversible discharge capacity of 100 mAh g−1 when cycled at 1 C rate. The apparent Li+ diffusion coefficients of the material ranged between 9.5 × 10−10 and 0.9 × 10−10 cm2 s−1, which were larger than those of olivine LiFePO4. The large lithium diffusion coefficient of Li3V2(PO4)3 has been attributed to its special NASICON-type structure.
Co-reporter:Shiying Zhan, Yingjin Wei, Xiaofei Bie, Chunzhong Wang, Fei Du, Gang Chen, Fang Hu
Journal of Alloys and Compounds 2010 Volume 502(Issue 1) pp:92-96
Publication Date(Web):16 July 2010
DOI:10.1016/j.jallcom.2010.03.133
V2O5 and Al0.2V2O5 nanoparticles were prepared by an oxalic acid assisted soft-chemical method. X-ray photoelectron spectroscopy confirmed the V5+ oxidation state of V2O5, whereas an intermediate state between V5+ and V4+ of Al0.2V2O5. Raman scattering showed that the Al3+ ions existed in an [AlO6] octahedral environment. The doping of Al3+ increased the cohesion between the V2O5 slabs, which enhanced the structural stability of the material. The chemical diffusion coefficients of the Al0.2V2O5 nanoparticles were a little bit smaller than those of V2O5. Charge–discharge cycling showed that the Al0.2V2O5 nanoparticles exhibited much better capacity retention than the un-doped V2O5, which was attributed to the enhanced structural stability of the material.
Co-reporter:Tao Jiang, Fei Du, Kejin Zhang, Yingjin Wei, Zhe Li, Chunzhong Wang, Gang Chen
Solid State Sciences 2010 Volume 12(Issue 9) pp:1672-1676
Publication Date(Web):September 2010
DOI:10.1016/j.solidstatesciences.2010.07.023
Carbon coated and carbon free Li3V2(PO4)3 cathode materials were prepared by carbothermal reduction and H2 reduction methods, respectively. The carbon free material had a grain size about 1 μm whereas the carbon coated material was less than 100 nm. The surface carbon layer enhanced the electronic conductivity of Li3V2(PO4)3 by five orders of magnitude. In addition, the surface carbon layer also prevented the formation of SEI film, decreased the charge transfer resistance and increased the chemical diffusion coefficient of Li+ ions. All of these advantages improved the electrochemical performance of Li3V2(PO4)3. As most of intercalation materials, the low temperature performance of Li3V2(PO4)3 was poorer than that at room temperature. This was attributed to the electrochemical sluggish kinetics which caused higher charge transfer resistance and smaller chemical diffusion coefficient. The carbon coating technique was effective to eliminate these sluggish kinetics, and then improved the low temperature performance of Li3V2(PO4)3.
Co-reporter:Shiying Zhan;Chunzhong Wang;Gang Chen;Fei Du
Ionics 2010 Volume 16( Issue 3) pp:209-213
Publication Date(Web):2010 April
DOI:10.1007/s11581-009-0399-0
Nano-sized Al3+-doped V2O5 cathode materials, Al0.2V2O5.3−δ, were prepared by an oxalic acid assisted sol–gel method at 350 °C (sample A) and 400 °C (sample B). X-ray diffraction confirmed that samples A and B were pure phase Al0.2V2O5.3−δ with an orthorhombic structure close to that of V2O5. Scanning electron microscopy showed that sample A was in nanoscale with a mean particle size about 50 nm. Cyclic voltammetry showed the good electrochemical and structural reversibility of the Al0.2V2O5.3−δ nanoparticles during the Li+ insertion/extraction process. The Al0.2V2O5.3−δ nanoparticles exhibited excellent charge–discharge cycling performance and rate capability compared to that of bulky V2O5 electrodes. For instance, the materials delivered a reversible specific capacity about 180 mAh g−1 (sample A) and 150 mAh g−1 (sample B), in the potential window of 4.0–2.0 V at the current density of 150 mA g−1. The Al0.2V2O5.3−δ nanoparticles in particular showed almost no capacity fading for at least 50 cycles.
Co-reporter:Y.J. Wei, K. Nikolowski, S.Y. Zhan, H. Ehrenberg, S. Oswald, G. Chen, C.Z. Wang, H. Chen
Electrochemistry Communications 2009 Volume 11(Issue 10) pp:2008-2011
Publication Date(Web):October 2009
DOI:10.1016/j.elecom.2009.08.040
Li[Li0.23Co0.3Mn0.47]O2 cathode material was prepared by a sol–gel method. The material had a primary particle size of about 100 nm, covered by a 30 Å of Li2CO3 layer. The material showed promising electrochemical performance when cycled up to 3C rate. The electrochemical kinetics of the first charge was much slower than that of the second charge, due to the complex electrochemical process which involved not only Li+ diffusion but also release of oxygen. By taking account of this, the material was pre-charged very slowly (∼C/50) in the first cycle. This led to excellent electrochemical performance in the following cycles. For instance, the 1C-rate capacity increased to 168 mA h g−1 after 50 cycles, comparing with the 145 mA h g−1 obtained without pre-charging.
Co-reporter:Daliang Liu, Fei Du, Wencheng Pan, Gang Chen, Chunzhong Wang, Yingjin Wei
Materials Letters 2009 Volume 63(3–4) pp:504-506
Publication Date(Web):15 February 2009
DOI:10.1016/j.matlet.2008.11.036
Li2.6Co0.4N anode material was prepared by solid-state reaction. The material was used to prepare Li2.6Co0.4N/natural graphite composite anode materials with the aim to improve the electrochemical performance of natural graphite. Natural graphite showed a low initial columbic efficiency of 69%, which was improved to ~ 100% by adding 20 wt.% of Li2.6Co0.4N into the material. On the other hand, the composite materials showed better capacity retention than both pure Li2.6Co0.4N and natural graphite. The material containing 20 wt.% of Li2.6Co0.4N exhibited a reversible discharge capacity of 243 mAh g− 1 after thirty cycles, as compared to a capacity of 212 mAh g− 1 for natural graphite.
Co-reporter:Tao Jiang, Chunzhong Wang, Gang Chen, Hong Chen, Yingjin Wei, Xu Li
Solid State Ionics 2009 Volume 180(9–10) pp:708-714
Publication Date(Web):29 May 2009
DOI:10.1016/j.ssi.2009.02.027
A series of monoclinic Li3V2(PO4)3 cathode materials were prepared by H2 reduction (LVP-H2) and carbothermal reduction (LVP-CTR) methods. LVP-H2 showed a primary particle size of about 1 μm, which was much larger than the LVP-CTR samples. A uniform surface carbon layer was observed for the LVP-CTR samples by transmission electron microscope. This carbon layer not only limited the particle growth of the materials but also enhanced the material's electronic conductivity by five orders of magnitude. The LVP-CTR samples exhibited much better electrochemical performance than LVP-H2. The good electrochemical performance of LVP-CTR was attributed to its nano particle size, high electronic conductivity, as well as the surface carbon layer which limited the vanadium dissolution in electrolyte.
Co-reporter:S.Y. Zhan, C.Z. Wang, K. Nikolowski, H. Ehrenberg, G. Chen, Y.J. Wei
Solid State Ionics 2009 Volume 180(20–22) pp:1198-1203
Publication Date(Web):17 August 2009
DOI:10.1016/j.ssi.2009.05.020
Cr0.1V2O5.15 was prepared by an oxalic acid assisted sol–gel method. X-ray diffraction showed that Cr doping induced a slight expansion (ΔV/V ≈ 2.3%) in the crystal lattice of V2O5. The electrochemical properties of Cr0.1V2O5.15 in the potential range of 3.8–2.0 V were studied by cyclic voltammetry, galvanostatic charge–discharge cycling and potentiostatic intermittent titration technique. Cyclic voltammetry showed that the irreversible phase transition of V2O5 during the first cycle was effectively prevented by Cr doping. This caused the good charge–discharge cycling performance of the doped material. The discharge capacities were recorded to be 200, 170 and 120 mAhg− 1 after fifty cycles at the C/10, C/2 and 1C rates, respectively. However, ex-situ X-ray diffraction showed that the crystal structure of the material was destroyed after long-term cycling. The lithium diffusion coefficient of Cr0.1V2O5.15 varied between 10− 11 and 10− 12 cm2 s− 1, which was larger than that of crystalline V2O5, and was close to those of metal doped V2O5 in previous reports. The improvement in lithium diffusion kinetics was regarded as an important reason for the good electrochemical performance of Cr0.1V2O5.15.
Co-reporter:Jiajia Ning, Tao Jiang, Kangkang Men, Quanqin Dai, Dongmei Li, Yingjin Wei, Bingbing Liu, Gang Chen, Bo Zou and Guangtian Zou
The Journal of Physical Chemistry C 2009 Volume 113(Issue 32) pp:14140-14144
Publication Date(Web):July 17, 2009
DOI:10.1021/jp905668p
Hierarchical SnO nanocrystals are synthesized by a reproducible and facile way via decomposition of an intermediate product tin oxide hydroxide, Sn6O4(OH)4. By changing the amount of injecting water, layer-plate-like, nest-like, stepwise-bipyramid-like, and defective stepwise-bipyramid-like hierarchical SnO nanocrystals could be obtained. All of these hierarchical SnO nanostructures are constructed by smaller nanosheets. The driving force of aggregation is reducing the surface energy of nanocrystals. Water played a key role in the control morphologies of hierarchical SnO nanostructures. The water control decomposition (WCD) mechanism was proposed to explain the effect of water on the morphologies. On the basis of reaction kinetics, the different superfluous injected water after reaction would restrain the decomposition of Sn6O4(OH)4 to SnO nanosheets; a different amount of superfluous injected water would induce a different reaction rate. At different reaction rates, SnO nanosheets would have different sizes and different approaches to aggregation, and different hierarchical SnO nanocrystals appeared by injecting different amounts of water into the reaction. Typically, hierarchical SnO nanocrystals as an anode material for lithium ion batteries are studied. These SnO nanocrystals show good potential for lithium battery materials. Among these SnO nanostructures, the stepwise-bipyramid-like nanostructure shows the best properties.
Co-reporter:Yingjin Wei, Chang-Wan Ryu, Kwang-Bum Kim
Journal of Alloys and Compounds 2008 Volume 459(1–2) pp:L13-L17
Publication Date(Web):14 July 2008
DOI:10.1016/j.jallcom.2007.04.275
A uniform and high crystalline Cu0.04V2O5 powder was prepared by precipitation method. The effects of Cu doping on the electrochemical properties of crystalline V2O5 were investigated by means of galvanostatic charge–discharge cycling, cyclic voltammetry and electrochemical impedance spectroscopy. The results showed that slight Cu doping significantly improved the electrochemical properties of V2O5. Cu-doped Cu0.04V2O5 exhibited promising electrochemical performance, with a reversible energy density of 450 Wh/kg and a power density of 275 W/kg.
Co-reporter:Daliang Liu, Shiying Zhan, Gang Chen, Wencheng Pan, Chunzhong Wang, Yingjin Wei
Materials Letters 2008 Volume 62(Issue 26) pp:4210-4212
Publication Date(Web):15 October 2008
DOI:10.1016/j.matlet.2008.06.036
Li2.6Co0.4 - xCuxN (x = 0, 0.15) anode materials were prepared by conventional solid state reaction. Between both materials, Li2.6Co0.25Cu0.15N exhibited better capacity retention than that of Li2.6Co0.4N. According to electrochemical impedance spectroscopy, the better cycling behavior of Li2.6Co0.25Cu0.15N has been attributed to the improvement in interfacial compatibility between the electrode and electrolyte interface. A possible explanation to this was given. Li2.6Co0.4 - xCuxN/Cu0.04V2O5 full-cells were assembled to investigate the reliability of Li2.6Co0.4 - xCuxN anode materials in practical applications. The Li2.6Co0.25Cu0.15N/Cu0.04V2O5 cell delivered a specific capacity of 260 mA h g− 1, and a specific energy of 505.7 mW h g− 1, which was much higher than that of C/LiCoO2 lithium ion batteries.
Co-reporter:Yingjin Wei, Chang-Wan Ryu, Kwang-Bum Kim
Journal of Power Sources 2007 Volume 165(Issue 1) pp:386-392
Publication Date(Web):25 February 2007
DOI:10.1016/j.jpowsour.2006.12.016
Cu0.04V2O5 was prepared by a precipitation method followed by heat treatment at 300 and 600 °C. The material prepared at 300 °C showed porous morphology, whereas that prepared at 600 °C was highly crystalline. X-ray diffraction, Raman scattering and Fourier transform infrared spectroscopy showed both materials exhibiting the same structure as that of V2O5, with a slight lattice expansion. X-ray absorption spectroscopy confirmed the presence of V4+ cations in Cu0.04V2O5, which would increase the electronic conductivity of V2O5. Cu0.04V2O5 showed better electrochemical performance than V2O5 because of its high electronic conductivity and good structural stability. The material prepared at 600 °C delivered a reversible discharge capacity over 160 mAh g−1 after 60 cycles at a C rate of C/5.6. The material prepared at 300 °C showed good high-rate performance, which delivered a reversible capacity ∼100 mAh g−1 when cycled at C/1.9. The discrepancy in the rate performance of Cu0.04V2O5 was attributed to the morphology of materials.
Co-reporter:Yuan Meng, Dashuai Wang, Yingjin Wei, Kai Zhu, Yingying Zhao, Xiaofei Bian, Fei Du, Bingbing Liu, Yu Gao, Gang Chen
Journal of Power Sources (1 April 2017) Volume 346() pp:134-142
Publication Date(Web):1 April 2017
DOI:10.1016/j.jpowsour.2017.02.033
•TiO2-B nanowires were prepared by the hydrothermal method.•TiO2-B nanowires showed Mg2+ double-layer capacitive in Mg battery.•TiO2-B nanowires showed Li+ pseudo-capacitive in Li+/Mg2+ hybrid-ion battery.•The hybrid battery showed longer cycle life and larger capacity than Mg battery.Titanium dioxide bronze (TiO2-B) nanowires were prepared by the hydrothermal method and used as the positive electrode for Mg rechargeable batteries and Li+/Mg2+ hybrid-ion batteries. First-principles calculations showed that the diffusion barrier for Mg2+ (0.6 eV) in the TiO2-B lattice was more than twice of that for Li+ (0.3 eV). Electrochemical impedance spectroscopy showed that the charge transfer resistance of TiO2-B in the Mg2+ ion electrolyte was much larger than that in the Li+/Mg2+ hybrid electrolyte. For these reasons, the Mg rechargeable battery showed a small discharge capacity of 35 mAh g−1 resulting from an electrochemical double-layer capacitive process. In comparison, the TiO2-B nanowires exhibited a large capacity (242 mAh g−1 at the 20 mA g−1 current density), high rate capability (114 mAh g−1 at 1 A g−1), and excellent cycle stability in the Li+/Mg2+ hybrid-ion battery. The dominant reaction occurred in the TiO2-B electrode was intercalation of Li+ ions, of which about 74% of the total capacity was attributed to Li+ pseudo-capacitance.
Co-reporter:Qiang Pang, Yingying Zhao, Xiaofei Bian, Yanming Ju, Xudong Wang, Yingjin Wei, Bingbing Liu, Fei Du, Chunzhong Wang and Gang Chen
Journal of Materials Chemistry A 2017 - vol. 5(Issue 7) pp:NaN3674-3674
Publication Date(Web):2017/01/13
DOI:10.1039/C6TA10216F
A graphene@MoS2@TiO2 hybrid material was successfully prepared by a multi-step solution chemistry method. Few-layered MoS2 nanosheets were impregnated into the nanovoids of mesoporous TiO2 microspheres and the composite was further encapsulated by a graphene layer. When used as a negative electrode material for lithium ion batteries, the nanovoids of TiO2 reduced aggregation of MoS2 and suppressed the large volume change of the active material. Moreover, the dissolution and shuttle of polysulfides were effectively suppressed by the hybrid bonding between MoS2 and TiO2. The nano-sized MoS2 and TiO2 particles encapsulated by a high electronic conductive graphene layer improved the charge transfer reaction of the electrode. Due to these merits, the graphene@MoS2@TiO2 showed a large discharge capacity of 980 mA h g−1 at 0.1 A g−1 current density with a capacity retention of 89% after 200 cycles. Moreover, the material delivered 602 mA h g−1 at 2 A g−1 current density, much larger than 91 mA h g−1 for the pristine MoS2. This demonstrated that the hybrid graphene@MoS2@TiO2 microspheres have great potential as a high-performance negative electrode material for lithium ion batteries.
Co-reporter:Xiaofei Bian, Yu Gao, Qiang Fu, Sylvio Indris, Yanming Ju, Yuan Meng, Fei Du, Natalia Bramnik, Helmut Ehrenberg and Yingjin Wei
Journal of Materials Chemistry A 2017 - vol. 5(Issue 2) pp:NaN608-608
Publication Date(Web):2016/11/23
DOI:10.1039/C6TA08505A
The practical uses of magnesium-ion batteries are hindered by their poor rate capability and fast capacity decay. Moreover, traditional sodium ion batteries suffer from serious safety problems resulting from the sodium dendrites formed on the anode. In order to circumvent these problems, we designed a highly reversible Na+/Mg2+ hybrid-ion battery composed of a metallic Mg anode, a TiS2 derived titanium sulfide cathode and a 1.0 M NaBH4 + 0.1 M Mg(BH4)2/diglyme hybrid electrolyte. The battery showed remarkable electrochemical performances with a large discharge capacity (200 mA h g−1 at the 1C rate), high rate capability (75 mA h g−1 at the 20C rate) and long cycle life (90% capacity retention after 3000 cycles). Moreover, it exhibited excellent safety properties due to dendrite-free Mg deposition of the anode and the high thermal stability of the cathode. These merits demonstrate the great potential of the reported Na+/Mg2+ hybrid-ion battery for large-scale energy storage.
Co-reporter:Qiang Fu, Fei Du, Xiaofei Bian, Yuhui Wang, Xiao Yan, Yongquan Zhang, Kai Zhu, Gang Chen, Chunzhong Wang and Yingjin Wei
Journal of Materials Chemistry A 2014 - vol. 2(Issue 20) pp:NaN7562-7562
Publication Date(Web):2014/02/25
DOI:10.1039/C4TA00189C
Li1.18Co0.15Ni0.15Mn0.52O2 cathode material was prepared by the sol–gel method. The material was coated with the ionic conductor Li3VO4via direct reaction with NH4VO3 at 350 °C. The Li3VO4 coated material had a higher ordered hexagonal layered structure, and less Li+/Ni2+ cation mixing. The surface of the coated material was composed of Li3VO4 polycrystals, which were impregnated into the bulk of the active material. The surface coating protected the material from contact with CO2 in the air, thus inhibiting the formation of an Li2CO3 layer. Electrochemical studies showed that the Li3VO4 surface coating improved the activation of Mn4+ ions, resulting in a high discharge capacity. It also prohibited the growth of a solid electrolyte interface film, and facilitated the charge transfer reactions at the electrode/electrolyte interface, thus improving the rate capability and cycle stability of the material. DSC analysis of the fully charged electrode showed that the temperature of the exothermic peak increased from 205.2 °C to 232.8 °C, and that the amount of heat that was released was reduced from 807.5 J g−1 to 551.0 J g−1, highlighting the improved thermal stability of the material after coating with Li3VO4 .
Co-reporter:Xiao Yan, Yanjuan Li, Malin Li, Yongcheng Jin, Fei Du, Gang Chen and Yingjin Wei
Journal of Materials Chemistry A 2015 - vol. 3(Issue 8) pp:NaN4187-4187
Publication Date(Web):2015/01/14
DOI:10.1039/C4TA06361A
A TiO2–bronze/N-doped graphene nanocomposite (TiO2–B/NG) is prepared by a facile hydrothermal combined with hydrazine monohydrate vapor reduction method. The material exhibits macro- and meso-porosity with a high specific surface area of 163.4 m2 g−1. X-Ray photoelectron spectroscopy confirms the successful doping of nitrogen in the graphene sheets. In addition, the TiO2–B nanowires are substantially bonded to the NG sheets. Cyclic voltammetry and electrochemical impedance spectroscopy show that the N-doped graphene improves the electron and Li ion transport in the electrode which results in better electrochemical kinetics than that of the pristine TiO2–B nanowires. As a result, the charge transfer resistance of the TiO2–B/NG electrode is significantly reduced. In addition, the lithium diffusion coefficient of TiO2–B/NG increases by about five times with respect to that of pristine TiO2–B. The TiO2–B/NG composite exhibits a remarkably enhanced electrochemical performance compared to that of TiO2–B. It shows a discharge capacity of 220.7 mA h g−1 at the 10C rate with a capacity retention of 96% after 1000 cycles. In addition, it can deliver a discharge capacity of 101.6 mA h g−1 at an ultra high rate of 100C, indicating its great potential for use in high power lithium ion batteries.
Co-reporter:Zhe Li ; Fei Du ; Xiaofei Bie ; Dong Zhang ; Yongmao Cai ; Xinran Cui ; Chunzhong Wang ; Gang Chen
The Journal of Physical Chemistry C () pp:
Publication Date(Web):December 7, 2010
DOI:10.1021/jp1088788
The Li[Li0.23Co0.3Mn0.47]O2 cathode material was prepared by a sol−gel method. Combinative X-ray diffraction (XRD) and Raman scattering studies showed that the material was a solid solution rather than a composite of nano Li2MnO3 and LiCoO2. The material had a high discharge capacity of 250 mAh g−1 in the voltage window of 2.0−4.8 V. However, the capacity retention was poor. The material showed different electrochemical mechanisms in the first charge and subsequent cycles. Galvanostatic intermittent titration technique (GITT) study showed that the Li+ diffusion coefficients during the first charge were as small as 10−19 cm2 s−1 because of the high kinetic barriers associated with the concurrent Li+ extraction, oxygen loss, and structural rearrangement. The Li+ diffusion coefficients increased to 10−14 cm2 s−1 after the first charge. However, they were still much smaller than those of typical layered materials such as LiCoO2 and Li(Ni1/3Co1/3Mn1/3)O2. Electrochemical impedance spectroscopy (EIS) study showed that the large interface impedance at high potential seriously hindered the electrode performance of the material. A lower charge cutoff voltage of 4.6 V was the most suitable for this material considering that the correponding reversible capacity (∼200 mAh g−1) was attractive for high energy density lithium ion batteries.
Co-reporter:Kai Zhu, Shaohua Guo, Jin Yi, Songyan Bai, Yingjin Wei, Gang Chen and Haoshen Zhou
Journal of Materials Chemistry A 2015 - vol. 3(Issue 44) pp:NaN22016-22016
Publication Date(Web):2015/10/08
DOI:10.1039/C5TA05444C
A new layered Na0.3MoO2 exhibits a reversible capacity of 146 mA h g−1, remarkable cycling stability and good rate capability for sodium half-cells. And a Na0.3MoO2//Na0.8Ni0.4Ti0.6O2 full intercalation-type sodium-ion cell is fabricated and it displays an excellent cycling stability. These results indicate that molybdenum-based oxide is a promising anode material for sodium-ion batteries.
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