APPLIED SURFACE SCIENCE
·
2017
·
IF 3.387
Hong-Mei Cheng,Shi-Xi Zhao,Xia Wu,Jian-Wei Zhao,Lei Wei,Ce-Wen Nan
The crystal structure of the Li 2 MnSiO 4 cathode material would collapse during the charge and discharge process because of that the Mn-O coordination polyhedron changed from [MnO 4 ] into [MnO 6 ] in the process of Mn +2 to Mn +4 , but the Cr element could remain [CrO 4 ] crystal ligand from Cr +2 to Cr +4 , so Cr element substitution was used to improve the structural stability of the Li 2 MnSiO 4 cathode material. In this work, Li 2 Mn 1-x Cr x SiO 4 /C nanocomposites were synthesized by solid-state method. XRD, SEM and TEM observations show that the as-prepared Li 2 Mn 1-x Cr x SiO 4 /C materials presents an orthorhombic crystal structure (S.G. Pmn2 1 ), the particle size of Li 2 Mn 1-x Cr x SiO 4 /C powder ranges from 50 to 100 nm. The XRD and XPS results indicate that Cr +2 is successfully doped into Li 2 MnSiO 4 lattice and has well compatibility with Li 2 MnSiO 4 . The electrochemical results display that Li 2 Mn 92.5% Cr 7.5% SiO 4 /C exhibits significantly enhanced cycle stability and discharge capability. The initial discharge capacity of the Li 2 Mn 92.5% Cr 7.5% SiO 4 /C sample is 255 mAh g −1 , and the discharge capacity was still about 60 mAh g −1 after 50 cycles. Furthermore, the XRD patterns, TEM images and Raman analysis reveal that the Cr doping enhances the structural stability of Li 2 Mn 1-x Cr x SiO 4 /C and improves the electrochemical activity of the cathode. Thus, the Li 2 Mn 92.5% Cr 7.5% SiO 4 /C have shown potential applications for lithium ion batteries.
研究领域:
材料科学
·
电化学
✓ 已验证
DOI
高影响因子
DALTON TRANSACTIONS
·
2018
·Vol. 47
·期 35
·12337-12344
·
IF 4.099
Xia Wu,Shi-Xi Zhao,Lü-Qiang Yu,Jin-Lin Yang,Ce-Wen Nan
Based on the existing calculation reports, sulfur doping is an effective approach to alleviate the structure collapse of Li2MnSiO4 during cycling. Herein, we investigate the feasibility and limitations of S doping in Li2MnSiO4 by experiment. In our work, the solid solubility of S is confirmed and exceeding the threshold results in MnS impurity. The existence state and site of the S element in a Li2MnSiO4 crystal structure is also confirmed. It is found that S doping significantly improves the structural reversibility and cycling stability. Compared with a pristine sample, a 1mol% S doped sample exhibits a much higher initial coulombic efficiency (88.3%), excellent capacity retention (98% at 10th cycles for instance) and enhanced rate performance. Moreover, the 1mol% S doped sample can retain a discharge capacity of 137 mA h g−1 after 30 cycles while the pristine sample only has 61.6 mA h g−1. This study confirms the effectivity of S doping in suppressing the structural distortion in Li2MnSiO4.
研究领域:
材料科学
·
电化学
✓ 已验证
DOI
PubMed
高影响因子
RSC Advances
·
2016
·Vol. 6
·期 112
·111539-111548
·
IF 3.289
Hui Deng,Shi-Xi Zhao,Xia Wu,Lei Wei,Yu-Feng Deng,Ce-Wen Nan
The chief drawback of Li2MnSiO4 cathode materials is structural instability deriving from the transformation of [MnO4] tetrahedra to [MnO6] octahedra during oxidation from Mn(II) to Mn(III) and the Jahn–Teller effect especially from Mn(III) to Mn(IV). Based on the theory that Ni2+ could keep the [NiO4] ligand unchanged and stable during oxidation/reduction, [NiO4] tetrahedra may behave as a regional structural framework to support the total crystal lattice and alleviate structural distortion partially. In this paper we synthesize nano-Li2Mn1−xNixSiO4/C samples with a small amount of Ni as the dopant via a hydrothermal route. Firstly, we discuss the existential state of Ni through XPS spectra, and demonstrate that both Ni2+ and metallic Ni coexist, especially Ni2+ could improve structural stability. The influence of Ni doping on morphology, structural stability, and electrochemical performance is discussed through Raman spectroscopy and electrochemical tests below. It is confirmed that there exists an optimal Ni content under which the optimal performance is displayed. In our work, the optimum Ni content is 5.0%, and the maximal discharge capacity achieved is 235 mA h g−1 for the 5.0% Ni doped sample in the first cycle.
研究领域:
材料科学
·
电化学
✓ 已验证
DOI
高影响因子
JOURNAL OF POWER SOURCES
·
2018
·
IF 6.945
Chao Wang,Youlong Xu,Xiaofei Sun,Baofeng Zhang,Yanjun Chen,Shengnan He
The Li 2 MnSiO 4 as a novel cathode material for lithium ion batteries, performs high specific capacity, high thermal stability, low cost and etc. However, it suffers from relatively low electronic conductivity and lithium ion diffusion rate. Herein, we successfully introduce fluorine to Li 2 MnSiO 4 (Li 2 MnSiO 4-x F x , x = 0.00, 0.01, 0.03 and 0.05) to overcome these obstacles. The results show that F doping not only enlarges the lattice parameters but also decreases the particle size, synergistically improving the lithium ion diffusion of Li 2 MnSiO 4 . Moreover, F doping increase electronic conductivity of Li 2 MnSiO 4 /C by inhibiting the formation of C-O bonds in the carbon layers . Meanwhile, F doping improves the crystallinity and stabilizes the crystal structure of Li 2 MnSiO 4 . Finally, the Li 2 MnSiO 3.97 F 0.03 /C with the best electrochemical performances delivers the initial specific discharge capacity of 279 mA h g −1 at 25mA g −1 current density from 1.5 V to 4.8 V. Also, it maintains a higher capacity (201 mA h g −1 ) than F-free Li 2 MnSiO 4 (145 mA h g −1 ) after 50 cycles.
研究领域:
材料科学
·
电化学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
·
2014
·
IF 2.726
Yan-Chao Wang,Shi-Xi Zhao,Peng-Yuan Zhai,Fang Li,Ce-Wen Nan
Orthorhombic structure Li 2 MnSiO 4 /C with Pmn2 1 space group is synthesized by the solvothermal method. Carbon coating and Ni 2+ doping are used to improve the electronic conductivity and the cycling performance of Li 2 MnSiO 4 cathode material, respectively. The particles of Li 2 MnSiO 4 /C are much smaller and more uniform than those of Li 2 MnSiO 4 due to the carbon coating. It is shown that Ni 2+ has been reduced into metal Ni during the synthesis process. The synthesized Ni-modified Li 2 MnSiO 4 /C (denoted as (LMS@Ni)/C) cathode material exhibits better electrochemical performance in comparison with Li 2 MnSiO 4 /C, attributing to higher lithium ion diffusion coefficient as well as electronic conductivity. The initial discharge capacity of (LMS@Ni)/C is 274.5 mA h g −1 and the reversible capacity after 20 cycles is 119.8 mA h g −1 at 25 °C.
✓ 已验证
DOI
高影响因子
ELECTROCHIMICA ACTA
·
2015
·
IF 4.504
Yue Dong,Wen-Long Zhang,Chun-Mei Wang,Ting Shi,Li Chen
Li 2 Mn 1 La x SiO 4 /C (x = 0, 0.01 and 0.04) composites are prepared via a polyol-assisted hydrothermal method followed by carbon coating. X-ray diffraction patterns confirm that the unit cell volume of Li 2 MnSiO 4 has been enlarged by doping a small amount of La 3+ . The scanning electron micrographs and elemental maps indicate that the sizes of the Li 2 MnSiO 4 particles can be reduced by homogeneously doping La 3+ . The transmission electron microscopy shows the well crystallized Li 2 MnSiO 4 nanoparticles. The electrochemical performances of all samples are evaluated by galvanostatic charge/discharge tests and electrochemical impedance spectroscopy. 1 at.% La 3+ doped Li 2 MnSiO 4 (AL1) delivers the highest initial discharge capacity of about 257 mAh g −1 , corresponding to the intercalation of about 1.55 lithium ions per formula unit. AL1 also exhibits improved capacity retentions of about 51.1%. The above improvements of electrochemical properties are related to the decreased charge transfer resistance and enhanced lithium ion diffusion for La-doped samples, whose crystal structure is maintained and lattice has been slightly enlarged.
✓ 已验证
DOI
高影响因子
MATERIALS LETTERS
·
2013
·
IF 2.224
Xiaolei Jiang,Huayun Xu,Jing Liu,Yitai Qian
The Li 2 MnSiO 4 /C nanocomposite is successfully synthesized by hydrothermal reaction at 150 °C for 48 h and then annealed at 650 °C in the presence of citric acid. Interestingly, the hydrothermal synthesized Li 2 MnSiO 4 shows a shuttle-like shape, which is composed of primary particles with average size of 50–100 nm. After carbon coating, these nanoparticles are separated from the secondary particles, and the thickness of carbon layer is about 2–4 nm. The Li 2 MnSiO 4 /C nanocomposite delivers an improved high electronic conductivity and an enhanced electrochemical behavior.
✓ 已验证
DOI
高影响因子
JOURNAL OF POWER SOURCES
·
2012
·
IF 4.951
Jing Liu,Huayun Xu,Xiaolei Jiang,Jian Yang,Yitai Qian
The Li 2 MnSiO 4 /C nanocomposite has been successfully synthesized at a relatively low temperature of 650 °C by a facile solid-state reaction using citric acid as the carbon source. The highly crystalline Li 2 MnSiO 4 nanoparticles in the size of 20–50 nm are coated by a uniform carbon layer in a thickness of 2–5 nm. At a rate of 0.05 C, the Li 2 MnSiO 4 /C nanocomposite exhibits a discharge specific capacity as high as 268 mAh g −1 for the first cycle and a reversible capacity of about 136 mAh g −1 after 140 cycles at room temperature. Meanwhile, an improved rate performance is achieved by the Li 2 MnSiO 4 /C nanocomposite. These superior electrochemical properties could be attributed to the nanoscale particle size and the enhanced electronic conductivity .
研究领域:
材料科学
·
电化学
·
储能
·
纳米材料
✓ 已验证
DOI
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
·
2017
·
IF 3.133
Xia Wu,Shi-Xi Zhao,Lei Wei,Hui Deng,Ce-Wen Nan
Li 2 MnSiO 4 cathode material suffers from structure collapse and thus rapid capacity fading during cycling. Here, we employed the stable [TiO 6 ] ligands as a local pillaring framework to improve the structural stability. Porous Li 2 MnSi 1- x Ti x O 4 /C nanoparticles were successfully synthesized by employing SBA-15 as Si source. Rietveld refinement revealed Ti substitution caused the phase composition transition (partial Pmnb to Pmn 2 1 phase), which contributed to higher charge/discharge capacity. XPS confirmed the positions of Ti 4+ and the formation of [TiO 6 ] octahedrons. 15 mol% Ti doped sample (S-LMST) showed a highest specific surface area of 114.25 m 2 g −1 and delivered a highest initial discharge capacity of 182.7 mAh g −1 under 1.5–4.8 V. Interestingly, S-LMST electrode presented excellent cycling stability, especially retaining ∼94% of initial discharge capacity after 8th cycles, while pristine Li 2 MnSiO 4 only retained ∼55%. Additionally, S-LMST electrode exhibited higher discharge capacity under lower cut-off voltage. The maximal initial discharge capacity can reach to 259.7 mAh g −1 in 1.5–4.6 V. The enhanced cycling stability can be mainly ascribed to the pillaring effect of [TiO 6 ] octahedrons and the decreased charge transfer resistance, as well as the improved Li + diffusion coefficient due to porous structure.
研究领域:
材料科学
·
电化学
✓ 已验证
DOI
高影响因子
INTERNATIONAL JOURNAL OF ENERGY RESEARCH
·
2021
·Vol. 45
·期 10
·14720-14731
·
IF 5.164
Yang Zhan,Qing Wang,Shao-Hua Luo,Si Li,Luo-Xuan Wang,Xin Liu,Ya-Hui Zhang,Long-Jiao Chang
Summary The lithium transition metal orthosilicates (Li 2 MnSiO 4 ) compounds are considered key materials for the next-generation lithium-ion batteries (LIBs). However, they exhibit poor electronic conductivity and structural stability. Herein, the dual-phase ( Pmn2 1 , and Pn ) coexisting Li 2 Mn 1− x Ni x SiO 4 @C is prepared successfully via a two-step calcination process to address the aforementioned problems. The orthorhombic Pmn2 1 and Pn phase are expected to bring well solid-state Li diffusion properties (D Li + ) and structural stability for electrode material, respectively. Also, the Ni doping and carbon coating are expected to raise electronic conductivity. Then, the electrochemical performance of LIBs utilizing LiMn 0.995 Ni 0.005 SiO 4 @C, LiMn 0.985 Ni 0.015 SiO 4 @C, and LiMn 0.92 Ni 0.08 SiO 4 @C (ZNi-02 to ZNi-04) as cathode materials are investigated and compared with that of the LiB using Li 2 MnSiO 4 @C (ZNi-01). The ZNi-04 sample-based LiB shows well D Li + and a peak discharge capacity as high as 188.4 mAh g −1 . In addition, the ZNi-04 sample can still maintain a capacity of about 80 mAh g −1 at rate of 8 C. Such excellent electrochemical performance is ascribed to the synergistic effect of the dual-phase coexistence, the proper amount of Ni doping, and surface coating of carbon, which enhances the electrical conductivity and structural stability. Thus, Li 2 Mn 1− x Ni x SiO 4 @C has broad application chances as a high-performance LIBs electrode material.
研究领域:
材料科学
·
电化学
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）