共查询到20条相似文献,搜索用时 15 毫秒
1.
Yinghua Chen Yanming Zhao Xiaoning An Jianmin Liu Youzhong Dong Ling Chen 《Electrochimica acta》2009,54(24):5844-5850
Cr-doped Li3V2−xCrx(PO4)3/C (x = 0, 0.05, 0.1, 0.2, 0.5, 1) compounds have been prepared using sol–gel method. The Rietveld refinement results indicate that single-phase Li3V2−xCrx(PO4)3/C with monoclinic structure can be obtained. Although the initial specific capacity decreased with Cr content at a lower current rate, both cycle performance and rate capability have excited improvement with moderate Cr-doping content in Li3V2−xCrx(PO4)3/C. Li3V1.9Cr0.1(PO4)3/C compound presents an initial capacity of 171.4 mAh g−1 and 78.6% capacity retention after 100 cycles at 0.2C rate. At 4C rate, the Li3V1.9Cr0.1(PO4)3/C can give an initial capacity of 130.2 mAh g−1 and 10.8% capacity loss after 100 cycles where the Li3V2(PO4)3/C presents the initial capacity of 127.4 mAh g−1 and capacity loss of 14.9%. Enhanced rate and cyclic capability may be attributed to the optimizing particle size, carbon coating quality, and structural stability during the proper amount of Cr-doping (x = 0.1) in V sites. 相似文献
2.
Electrochemical and thermal properties of Co3(PO4)2- and AlPO4-coated LiNi0.8Co0.2O2 cathode materials were compared. AlPO4-coated LiNi0.8Co0.2O2 cathodes exhibited an original specific capacity of 170.8 mAh g−1 and had a capacity retention (89.1% of its initial capacity) between 4.35 and 3.0 V after 60 cycles at 150 mA g−1. Co3(PO4)2-coated LiNi0.8Co0.2O2 cathodes exhibited an original specific capacity of 177.6 mAh g−1 and excellent capacity retention (91.8% of its initial capacity), which was attributed to a lithium-reactive Co3(PO4)2 coating. The Co3(PO4)2 coating material could react with LiOH and Li2CO3 impurities during annealing to form an olivine LixCoPO4 phase on the bulk surface, which minimized any side reactions with electrolytes and the dissolution of Ni4+ ions compared to the AlPO4-coated cathode. Differential scanning calorimetry results showed Co3(PO4)2-coated LiNi0.8Co0.2O2 cathode material had a much improved onset temperature of the oxygen evolution of about 218 °C, and a much lower amount of exothermic-heat release compared to the AlPO4-coated sample. 相似文献
3.
A spinel LiMn2O4/C composite was synthesized by hydrothermally treating a precursor of manganese oxide/carbon (MO/C) composite in 0.1 M LiOH solution at 180 °C for 24 h, where the precursor was prepared by reducing potassium permanganate with acetylene black (AB). The AB in the precursor serves as the reducing agent to synthesize the LiMn2O4 during the hydrothermal process; the excess of AB remains in the hydrothermal product, forming the LiMn2O4/C composite, where the remaining AB helps to improve the electronic conductivity of the composite. The contact between LiMn2O4 and C in our composite is better than that in the physically mixed LiMn2O4/C material. The electrochemical performance of the LiMn2O4/C composite was investigated; the material delivered a high capacity of 83 mAh g−1 and remained 92% of its initial capacity after 200 cycles at a current density of 2 A g−1, indicating its excellent rate capability as well as good cyclic performance. 相似文献
4.
Li[Li0.2Mn0.54Ni0.13Co0.13]O2 as a cathode material for Li-ion battery has been successfully prepared by co-precipitation (CP), sol–gel (SG) and sucrose combustion (SC) methods. The prepared materials were characterized by XRD, SEM, BET and electrochemical measurements. The XRD result shows that the Li[Li0.2Mn0.54Ni0.13Co0.13]O2 materials prepared by different methods all form a pure phase with good crystallinity. SEM images and BET data present that the SC-material exhibited the smallest particle size (ca. 0.1 μm) and the highest surface area (7.4635 m2 g−1). The tap density of SC-material is lower than that of CP- and SG-materials. The result of rate performance tests indicates that the SC-material showed the best rate capability with the highest discharge capacity of 178 mAh g−1 at 5.0 C, followed by SG-material and then CP-material. However, the cycling stability of SC-material tested at 0.1 and 0.5 C is relatively poor as compared to that of SG-material and CP-material. The result of EIS measurements reveals that large surface area and small particle size of the SC-electrode result in more SEI layer formation because of the increased side reactions with the electrolyte during cycling, which deteriorates the electrode/electrolyte interface and thus leads to the faster capacity fading of the SC-material. 相似文献
5.
Co-doped Li3V2−xCox(PO4)3/C (x = 0.00, 0.03, 0.05, 0.10, 0.13 or 0.15) compounds were prepared via a solid-state reaction. The Rietveld refinement results indicated that single-phase Li3V2−xCox(PO4)3/C (0 ≤ x ≤ 0.15) with a monoclinic structure was obtained. The X-ray photoelectron spectroscopy (XPS) analysis revealed that the cobalt is present in the +2 oxidation state in Li3V2−xCox(PO4)3. XPS studies also revealed that V4+ and V3+ ions were present in the Co2+-doped system. The initial specific capacity decreased as the Co-doping content increased, increasing monotonically with Co content for x > 0.10. Differential capacity curves of Li3V2−xCox(PO4)3/C compounds showed that the voltage peaks associated with the extraction of three Li+ ions shifted to higher voltages with an increase in Co content, and when the Co2+-doping content reached 0.15, the peak positions returned to those of the unsubstituted Li3V2(PO4)3 phase. For the Li3V1.85Co0.15(PO4)3/C compound, the initial capacity was 163.3 mAh/g (109.4% of the initial capacity of the undoped Li3V2(PO4)3) and 73.4% capacity retention was observed after 50 cycles at a 0.1 C charge/discharge rate. The doping of Co2+into V sites should be favorable for the structural stability of Li3V2−xCox(PO4)3/C compounds and so moderate the volume changes (expansion/contraction) seen during the reversible Li+ extraction/insertion, thus resulting in the improvement of cell cycling ability. 相似文献
6.
Al and/or Mg-substituted Li[Ni0.8Co0.1Mn0.1−x−yAlxMgy]O2 were prepared by a co-precipitation method and characterized by X-ray diffraction with Rietveld refinement, thermogravimetric analysis, differential scanning calorimetry (DSC), and electrochemical measurements. The Rietveld refinement results show that cation mixing of Al and/or Mg-substituted Li[Ni0.8Co0.1Mn0.1−x−yAlxMgy]O2 was reduced with increased doping amounts of Al and Mg. The Al and/or Mg substitution in Li[Ni0.8Co0.1Mn0.1]O2 also resulted in improved electrochemical cycling behavior, structural stability, and thermal stability compared to pristine Li[Ni0.8Co0.1Mn0.1]O2. The improvements of electrochemical and thermal properties resulted from the stabilized host structure by Al and/or Mg incorporation into Li[Ni0.8Co0.1Mn0.1]O2. 相似文献
7.
Hydrothermal synthesis and rate capacity studies of Li3V2(PO4)3 nanorods as cathode material for lithium-ion batteries 总被引:1,自引:0,他引:1
It is an effective method by synthesizing one-dimensional nanostructure to improve the rate performances of cathode materials for Li-ion batteries. In this paper, Li3V2(PO4)3 nanorods were successfully prepared by hydrothermal reaction method. The structure, composition and shape of the prepared were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scan electron microscope (SEM) and transmission electron microscope (TEM), respectively. The data indicate the as-synthesis powders are defect-rich nanorods and the sizes are the length of several hundreds of nanometers to 1 μm and the diameter of about 60 nm. The preferential growth direction of the prepared material was the [1 2 0]. The electrodes consisting of the Li3V2(PO4)3 nanorods show the better discharge capacities at high rates over a potential range of 3.0-4.6 V. These results can be attributed to the shorter distance of electron transport and the fact that ion diffusion in the electrode material is limited by the nanorod radius. All these results indicate that the resulting Li3V2(PO4)3 nanorods are promising cathode materials in lithium-ion batteries. 相似文献
8.
Ultrafine powders of LiNi0.9Co0.1O2 were prepared under mild hydrothermal conditions. The product was characterized by XRD, TEM and EDS tests, which indicated that the obtained products were pure and well-crystallized LiNi0.9Co0.1O2. The ICP-AES results indicated the products were lithium-deficient compounds. The addition of KOH hardly effected the crystallinity of the product but gave larger crystals. 相似文献
9.
Microwave-hydrothermal synthesis of Fe-based materials for lithium-ion batteries and supercapacitors
Kunfeng Chen Young Dong Noh Wenyan Huang Jianfeng Ma Sridhar Komarneni Dongfeng Xue 《Ceramics International》2014
Fe-based materials, Fe2O3, Fe3O4, and FeOOH, were synthesized by the microwave–hydrothermal process in the temperature range of 100–200 °C and under very short reaction times of 15 min to 2 h. Under microwave-controlled hydrolysis and redox reactions, cube-like Fe2O3 was crystallized using FeCl3, Fe3O4 particles were crystallized from FeCl2 and FeOOH nanorods were crystallized using FeCl3. The Fe-based materials were fabricated to make anodes and cathodes of lithium-ion battery and supercapacitor electrode materials to study their potential electrochemical applications. The electrochemical results showed that FeOOH had better anode capacity as lithium-ion batteries than those of Fe2O3 and Fe3O4. The present results suggest that the microwave–hydrothermally synthesized Fe-based materials are promising lithium-ion battery anode materials. 相似文献
10.
A positive electrode material for lithium ion battery applications was successfully synthesized using microwave irradiation. This microwave synthesis has several merits such as homogeneity of final product and much shorter reaction time compared to conventional synthetic methods. We synthesized spherical [Ni0.4Co0.2Mn0.4](OH)2 as a precursor by a co-precipitation method. The pelletized mixture of the precursor and lithium hydroxide was calcined under different reaction times and temperatures by applying 1200 W of microwave irradiation at 2.45 GHz. We determined the optimum conditions of microwave synthesis for positive electrode materials. The powders were characterized by X-ray diffraction, scanning electron microscopy, and electrochemical testing. The capacity, its retention, and thermal stability of Li[Ni0.4Co0.2Mn0.4]O2 synthesized by the microwave synthesis were comparable to the Li[Ni0.4Co0.2Mn0.4]O2 prepared by the high temperature calcination method. 相似文献
11.
Peng Yue Wenjie Peng Lingjun Li Wei Chen Huajun Guo Xinhai Li 《Powder Technology》2011,214(3):279-282
Layered LiNi0.6Co0.2Mn0.2O2 materials were synthesized at different sintering temperatures using spray-drying precursor with molar ratio of Li/Me = 1.04 (Me = transition metals). The influences of sintering temperature on crystal structure, morphology and electrochemical performance of LiNi0.6Co0.2Mn0.2O2 materials have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and charge-discharge test. As a result, material synthesized at 850 °C has excellent electrochemical performance, delivering an initial discharge capacity of 173.1 mAh g− 1 between 2.8 and 4.3 V at a current density of 16 mA g− 1 and exhibiting good cycling performance. 相似文献
12.
Li[Ni(1/3−z)Co(1/3−z)Mn(1/3−z)Mgz]O2 (z = 0, 0.04) positive electrode materials were synthesized via a co-precipitation method. These materials have α-NaFeO2 () structure, as confirmed by X-ray diffraction (XRD) studies. Cation mixing in Li layer seemed to be decreased by Mg substitution as examined by Rietveld refinements of XRD data. Spherical morphologies were observed for the as-synthesized final products by scanning electron microscopy. Their electrochemical properties during charge and discharge were discussed. When magnesium ions are substituted, the initial reversible capacity reduced. However, the substitution for Mn sites in Li[Ni1/3Co1/3Mn1/3]O2 did not decrease the capacity because Mn sites substitution did not result in loss of electroactive elements in the compound. Differential scanning calorimetric studies showed the exothermic peaks of the charged electrode Li[Ni(1/3−z)Co(1/3−z)Mn(1/3−z)Mgz]O2 (z = 0.04) were significantly smaller than that of Li[Ni1/3Co1/3Mn1/3]O2, which means that thermal stability was greatly improved by Mg substitution even at highly delithiated state. 相似文献
13.
A novel Li[Ni0.67Co0.15Mn0.18]O2 cathode material encapsulated completely within a concentration-gradient shell was successfully synthesized via co-precipitation. The Li[Ni0.67Co0.15Mn0.18]O2 has a core of Li[Ni0.8Co0.15Mn0.05]O2 that is rich in Ni, a concentration-gradient shell having decreasing Ni concentration and increasing Mn concentration toward the particle surface, and a stable outer-layer of Li[Ni0.57Co0.15Mn0.28]O2. The electrochemical and thermal properties of the material were investigated and compared to those of the core Li[Ni0.8Co0.15Mn0.05]O2 material alone. The discharge capacity of the concentration-gradient Li[Ni0.67Co0.15Mn0.18]O2 electrode increased with increasing upper cutoff voltage to 4.5 V, and cells with this cathode material delivered a very high capacity, 213 mAh/g, with excellent cycling stability even at 55 °C. The enhanced thermal and lithium intercalation stability of the Li[Ni0.67Co0.15Mn0.18]O2 was attributed to the gradual increase in tetravalent Mn concentration and decrease in Ni concentration in the concentration-gradient shell layer. 相似文献
14.
Ismael Saadoune Mohamed Labrini Mustapha Yahya Abdelmajid Almaggoussi 《Electrochimica acta》2010,55(18):5180-4086
We reported here on the synthesis, the crystal structure and the study of the structural changes during the electrochemical cycling of layered LiNi0.1Mn0.1Co0.8O2 positive electrode material. Rietveld refinement analysis shows that this material exhibits almost an ideal α-NaFeO2 structure with practically no lithium-nickel disorder. The SQUID measurements confirm this structural result and evidenced that this material consists of Ni2+, Mn4+ and Co3+ ions.Unlike LiNiO2 and LiCoO2 conventional electrode materials, there was no structural modification upon lithium removal in the whole 0.42 ≤ x ≤1.0 studied composition range. The peaks revealed in the incremental capacity curve were attributed to the successive oxidation of Ni2+ and Co3+ while Mn4+ remains electrochemically inactive. 相似文献
15.
Cr-doped Li9V3−xCrx(P2O7)3(PO4)2 (x = 0.0–0.5) compounds have been prepared using sol–gel method. The Rietveld refinement results indicate that single-phase Li9V3−xCrx(P2O7)3(PO4)2 (x = 0.0–0.5) with trigonal structure can be obtained. Although the initial specific capacity decreased with Cr content at a lower current rate, both cycle performance and rate capability have excited improvement with moderate Cr-doping content. Li9V2.8Cr0.2(P2O7)3(PO4)2 compound presents the good electrochemical rate and cyclic ability. The enhancement of rate and cyclic capability may be attributed to the optimizing particle size, morphologies, and structural stability during the proper amount of Cr-doping (x = 0.2) in V sites. 相似文献
16.
The deposition of Al2O3 on LiCoO2 electrodes using a low-temperature atomic layer deposition has been investigated. Scanning electron microscopy confirms that Al2O3 films can be homogeneously deposited on LiCoO2 particles of porous electrodes at 120 °C. The results of X-ray photoelectron spectroscopy show that the Al2O3 preferentially deposits on the LiCoO2. Furthermore, the results of cycling stability tests show that the cells with Al2O3-coated LiCoO2 electrodes have enhanced performance. 相似文献
17.
This paper describes a novel simple redox process for synthesizing monodispersed MnO2 powders and preparation of spherical LiNi0.5Mn1.5O4 cathode materials by molten salt synthesis (MSS) method. Monodispersed MnO2 powders have been synthesized by using potassium permanganate and manganese sulfate as the starting materials. By using this redox method, it was found that monodispersed MnO2 powders with average particle size ∼5 μm can be easily obtained. Resultant MnO2 and LiOH, Ni(OH)2 was then used to synthesis LiNi0.5Mn1.5O4 cathode materials with retention of spherical particle shape by MSS method. The discharge capacity was 129 mAh g−1 in the first cycle and 127 mAh g−1 after 50 cycles under an optimal synthesis condition for 12 h at 800 °C. 相似文献
18.
Layered Li[Ni0.5−xMn0.5−xZr2x]O2 (x = 0, 0.025) have been prepared by the mixed hydroxide and molten-salt synthesis method. The individual particles of synthesized materials have a sub-microsize range of 200-500 nm, and LiNi0.475Mn0.475Zr0.05O2 has a rougher surface than that of LiNi0.5Mn0.5O2. The Li/Li[Ni0.5−xMn0.5−xZr2x]O2 (x = 0, 0.025) electrodes were cycled between 4.5 and 2.0 V at a current density of 15 mA/g, the discharge capacity of both cells increased during the first ten cycles. The discharge capacity of the Li/LiNi0.475Mn0.475Zr0.05O2 cell increased from 150 to 220 mAh/g, which is 50 mAh/g larger than that of the Li/LiNi0.5Mn0.5O2 cell. We found that the oxidation of oxygen and the Mn3+ ion concerned this phenomenon from the cyclic voltammetry (CV). Thermal stability of the charged Li[Ni0.5−xMn0.5−xZr2x]O2 (x = 0, 0.025) cathode was improved by Zr doping. 相似文献
19.
Spherical (Ni0.5Mn0.5)(OH)2 with different secondary particle size (3 μm, 10 μm in diameter) was synthesized by co-precipitation method. Mixture of the prepared hydroxide and lithium hydroxide was calcined at 950 °C for 20 h in air. X-ray diffraction patterns revealed that the prepared material had a typical layered structure with space group. Spherical morphologies with mono-dispersed powders were observed by scanning electron microscopy. It was found that the layered Li[Ni0.5Mn0.5]O2 delivered an initial discharge capacity of 148 mAh g−1 (3.0-4.3 V) though the particle sizes were different. Li[Ni0.5Mn0.5]O2 having smaller particle size (3 μm) showed improved area specific impedance due to the reduced Li+ diffusion path, compared with that of Li[Ni0.5Mn0.5]O2 possessing larger particle size (10 μm). Although the Li[Ni0.5Mn0.5]O2 (3 μm) was electrochemically delithiated to Li0.39[Ni0.5Mn0.5]O2, the resulting exothermic onset temperature was around 295 °C, of which the value is significantly higher than that of highly delithiated Li1−δCoO2 (∼180 °C). 相似文献
20.
Well-ordered high crystalline LiNi0.5Mn1.5O4 spinel has been readily synthesized by a molten salt method using a mixture of LiCl and LiOH salts. Synthetic variables on the synthesis of LiNi0.5Mn1.5O4, such as synthetic atmosphere, LiCl salt amount, synthetic temperature, and synthetic time, were intensively investigated. X-ray diffraction (XRD) patterns and scanning electron microscopic (SEM) images showed that LiNi0.5Mn1.5O4 synthesized at 900 and 950 °C have cubic spinel structure () with clear octahedral dimension. LiNi0.5Mn1.5O4 spinel phase began to decompose at around 1000 °C accompanied with structural and morphological degradation. LiNi0.5Mn1.5O4 powders synthesized at 900 °C for 3 h delivered an initial discharge capacity of 139 mAh/g with excellent capacity retention rate more than 99% after 50 cycles. 相似文献