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1.
Synthesis, electrochemical, and structural properties of LiNi0.8Co0.15Al0.05O2 cathodes prepared by TiO2 nanoparticles coating on a Ni0.8Co0.15Al0.05(OH)2 precursor have been investigated by the variation of coating concentration and annealing temperature. TiO2-coated cathodes showed that Ti elements were distributed throughout the particles. Among the coated cathodes, the 0.6 wt% TiO2-coated cathode prepared by annealing at 750 °C for 20 h exhibited the highest reversible capacity of 176 mAh g−1 and capacity retention of 92% after 40 cycles at a rate of 1C (=190 mA g−1). On the other hand, an uncoated cathode showed a reversible first discharge capacity of 186 mAh g−1 and the same capacity retention value to the TiO2-coated sample at a 1C rate. However, under a 1C rate cycling at 60 °C for 30 cycles, the uncoated sample showed a reversible capacity of 40 mAh g−1, while a TiO2-coated one showed 71 mAh g−1. This significant improvement of the coated sample was due to the formation of a possible solid solution between TiO2 and LiNi0.8Co0.15Al0.05O2. This effect was more evident upon annealing the charged sample while increasing the annealing temperature, and at 400 °C, the coated one showed a more suppressed formation of the NiO phase from the spinel LiNi2O4 phase than the uncoated sample. 相似文献
2.
A high-performance LiNi0.8Co0.2O2 cathode was successfully fabricated by a sol-gel coating of CeO2 to the surface of the LiNi0.8Co0.2O2 powder and subsequent heat treatment at 700 °C for 5 h. The surface-modified and pristine LiNi0.8Co0.2O2 powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), slow rate cyclic voltammogram (CV), and differential scanning calorimetry (DSC). Unlike pristine LiNi0.8Co0.2O2, the CeO2-coated LiNi0.8Co0.2O2 cathode exhibits no decrease in its original specific capacity of 182 mAh/g (versus lithium metal) and excellent capacity retention (95% of its initial capacity) between 4.5 and 2.8 V after 55 cycles. The results indicate that the surface treatment should be an effective way to improve the comprehensive properties of the cathode materials for lithium ion batteries. 相似文献
3.
Electrochemical performance of the carbon coated Li3V2(PO4)3 cathode material synthesized by a sol-gel method 总被引:1,自引:0,他引:1
A carbon coated Li3V2(PO4)3 cathode material for lithium ion batteries was synthesized by a sol-gel method using V2O5, H2O2, NH4H2PO4, LiOH and citric acid as starting materials, and its physicochemical properties were investigated using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) spectroscopy, scanning electron microscopy (SEM), energy dispersive analysis of X-ray (EDAX), transmission electron microscope (TEM), and electrochemical methods. The sample prepared displays a monoclinic structure with a space group of P21/n, and its surface is covered with a rough and porous carbon layer. In the voltage range of 3.0-4.3 V, the Li3V2(PO4)3 electrode displays a large reversible capacity, good rate capability and excellent cyclic stability at both 25 and 55 °C. The largest reversible capacity of 130 mAh g−1 was obtained at 0.1C and 55 °C, nearly equivalent to the reversible cycling of two lithium ions per Li3V2(PO4)3 formula unit (133 mAh g−1). It was found that the increase in total carbon content can improve the discharge performance of the Li3V2(PO4)3 electrode. In the voltage range of 3.0-4.8 V, the extraction and reinsertion of the third lithium ion in the carbon coated Li3V2(PO4)3 host are almost reversible, exhibiting a reversible capacity of 177 mAh g−1 and good cyclic performance. The reasons for the excellent electrochemical performance of the carbon coated Li3V2(PO4)3 cathode material were also discussed. 相似文献
4.
Xianfa Zhang Jing Liu Haiying Yu Jiawei Wang Zijia Yu Haiming Xie Rongshun Wang 《Electrochimica acta》2010,55(7):2414-6675
A simple and effective method, ethylene glycol-assisted co-precipitation method, has been employed to synthesize LiNi0.5Mn1.5O4 spinel. As a chelating agent, ethylene glycol can realize the homogenous distributions of metal ions at the atomic scale and prevent the growth of LiNi0.5Mn1.5O4 particles. XRD reveals that the prepared material is a pure-phase cubic spinel structure (Fd3m) without any impurities. SEM images show that it has an agglomerate structure with the primary particle size of less than 100 nm. Electrochemical tests demonstrate that the as-prepared LiNi0.5Mn1.5O4 possesses high capacity and excellent rate capability. At 0.1 C rate, it shows a discharge capacity of 137 mAh g−1 which is about 93.4% of the theoretical capacity (146.7 mAh g−1). At the high rate of 5 C, it can still deliver a discharge capacity of 117 mAh g−1 with excellent capacity retention rate of more than 95% after 50 cycles. These results show that the as-prepared LiNi0.5Mn1.5O4 is a promising cathode material for high power Li-ion batteries. 相似文献
5.
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
6.
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
7.
LiNi1−xCoxO2 (x = 0, 0.1, 0.2) cathode materials were successfully synthesized by a rheological phase reaction method with calcination time of 0.5 h at 800 °C. All obtained powders are pure phase with α-NaFeO2 structure (R-3m space group). The samples deliver an initial discharge capacity of 182, 199 and 189 mAh g−1 (25 mA g−1, 4.35-3.0 V), respectively. The reaction mechanism was also discussed, which consists of a series of defect reactions. As a result of these defect reactions, the reaction of forming LiNi1−xCoxO2 takes place in high speed. 相似文献
8.
Uniform and spherical Li(Ni1/3Co1/3Mn1/3)O(2−δ)Fδ powders were synthesized via NH3 and F− coordination hydroxide co-precipitation. The effect of F− coordination agent on the morphology, structure and electrochemical properties of the Li(Ni1/3Co1/3Mn1/3)O(2−δ)Fδ were studied. The morphology, size, and distribution of (Ni1/3Co1/3Mn1/3)(OH)(2−δ)Fδ particle diameter were improved in a shorter reaction time through the addition of F−. The study suggested that the added F improves the layered characteristics of the lattice and the cyclic performance of Li(Ni1/3Co1/3Mn1/3)O2 in the voltage range of 2.8-4.6 V. The initial capacity of the Li(Ni1/3Co1/3Mn1/3)O1.96F0.04 was 178 mAh g−1, the maximum capacity was 186 mAh g−1 and the capacity after 50 cycles was 179 mAh g−1 in the voltage range of 2.8-4.6 V. 相似文献
9.
Micro-spherical particle of MnCO3 has been successfully synthesized in CTAB-C8H18-C4H9OH-H2O micro-emulsion system. Mn2O3 decomposed from the MnCO3 is mixed with Li2CO3 and sintered at 800 °C for 12 h, and the pure spinel LiMn2O4 in sub-micrometer size is obtained. The LiMn2O4 has initial discharge specific capacity of 124 mAh g−1 at discharge current of 120 mA g−1 between 3 and 4.2 V, and retains 118 mAh g−1 after 110 cycles. High-rate capability test shows that even at a current density of 16 C, capacity about 103 mAh g−1 is delivered, whose power is 57 times of that at 0.2 C. The capacity loss rate at 55 °C is 0.27% per cycle. 相似文献
10.
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
11.
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. 相似文献
12.
Ling-jun Li Zhi-xing Wang Hua-jun Guo Peng Yue Wei Chen Ling Wu 《Powder Technology》2011,206(3):353-357
Nanocrystalline materials of Ni0.8Co0.1Mn0.1(OH)2 are successfully synthesized by fast co-precipitation method. The crystalline structure and morphology of the precursors and LiNi0.8Co0.1Mn0.1O2 materials are characterized by XRD, SEM and Rietveld refinement analyses. It is found that the nanocrystalline phase and low crystallinity of Ni0.8Co0.1Mn0.1(OH)2 could help achieve its uniform mixing with lithium source, and further attribute to highly ordered layered LiNi0.8Co0.1Mn0.1O2 with low cation mixing degree. Electrochemical studies confirm that the LiNi0.8Co0.1Mn0.1O2 exhibits a good electrochemical property with initial discharge specific capacity of 192.4 mAh g− 1 at a current density of 18 mA g− 1, and the capacity retention after 40 cycles is 91.56%. This method is a simple and effective method to synthesize cathode material. 相似文献
13.
Non-spherical Li(Ni1/3Co1/3Mn1/3)O2 powders have been synthesized using a two-step drying method with 5% excess LiOH at 800 °C for 20 h. The tap-density of the powder obtained is 2.95 g cm−3. This value is remarkably higher than that of the Li(Ni1/3Co1/3Mn1/3)O2 powders obtained by other methods, which range from 1.50 g cm−3 to 2.40 g cm−3. The precursor and Li(Ni1/3Co1/3Mn1/3)O2 are characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscope (SEM). XPS studies show that the predominant oxidation states of Ni, Co and Mn in the precursor are 2+, 3+ and 4+, respectively. XRD results show that the Li(Ni1/3Co1/3Mn1/3)O2 material obtained by the two-step drying method has a well-layered structure with a small amount of cation mixing. SEM confirms that the Li(Ni1/3Co1/3Mn1/3)O2 particles obtained by this method are uniform. The initial discharge capacity of 167 mAh g−1 is obtained between 3 V and 4.3 V at a current of 0.2 C rate. The capacity of 159 mAh g−1 is retained at the end of 30 charge-discharge cycle with a capacity retention of 95%. 相似文献
14.
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
15.
Some polyanionic compounds, e.g. TiP2O7 and LiTi2(PO4)3 with 3D framework structure were proposed to be used as anodes of lithium ion battery with aqueous electrolyte. The cyclic voltammetry properties TiP2O7 and LiTi2(PO4)3 suggested that Li-ion de/intercalation reaction can occur without serious hydrogen evolution in 5 M LiNO3 aqueous solution. The TiP2O7 and LiTi2(PO4)3 give capacities of about 80 mAh/g between potentials of −0.50 V and 0 V (versus SHE) and 90 mAh/g between −0.65 V and −0.10 V (versus SHE), respectively. A test cell consisting of TiP2O7/5 M LiNO3/LiMn2O4 delivers approximately 42 mAh/g (weight of cathode and anode) at average voltage of 1.40 V, and LiTi2(PO4)3/5 M LiNO3/LiMn2O4 delivers approximately 45 mAh/g at average voltage of 1.50 V. Both as-assembled cells suffered from short cycle life. The capacity fading may be related to deterioration of anode material. 相似文献
16.
Yogesh Sharma 《Electrochimica acta》2008,53(5):2380-2385
The cubic ZnFe2O4 with the spinel structure is prepared by the urea combustion method. Powder X-ray diffraction and HR-TEM studies confirm the single-phase nature with particle size in the range, 100-300 nm. A stable and reversible capacity, 615(±10) mAh g−1 (5.5 moles of Li per mole of ZnFe2O4) when cycled in the range, 0.005-3.0 V vs. Li at a current of 60 mA g−1(0.1C) has been achieved between 15 and 50 cycles. The underlying reaction mechanism contributing to the observed capacity is the combination of ‘de-alloying-alloying’ and ‘conversion’ reactions of ‘LiZn-Fe-Li2O composite’. Ex situ HR-TEM and SAED data on the charged-electrode confirmed the proposed reaction mechanism. 相似文献
17.
Cathode active materials with a composition of LiNi0.9Co0.1O2 were synthesized by a solid-state reaction method at 850 °C using Li2CO3, NiO or NiCO3, and CoCO3 or Co3O4, as the sources of Li, Ni, and Co, respectively. Electrochemical properties, structure, and microstructure of the synthesized LiNi0.9Co0.1O2 samples were analyzed. The curves of voltage vs. x in LixNi0.9Co0.1O2 for the first charge–discharge and the intercalated and deintercalated Li quantity Δx were studied. The destruction of unstable 3b sites and phase transitions were discussed from the first and second charge–discharge curves of voltage vs. x in LixNi0.9Co0.1O2. The LiNi0.9Co0.1O2 sample synthesized from Li2CO3, NiO, and Co3O4 had the largest first discharge capacity (151 mA h/g), with a discharge capacity deterioration rate of −0.8 mA h/g/cycle (that is, a discharge capacity increasing 0.8 mA h/g per cycle). 相似文献
18.
Li2FeSiO4/carbon/carbon nano-tubes (Li2FeSiO4/C/CNTs) and Li2FeSiO4/carbon (Li2FeSiO4/C) composites were synthesized by a traditional solid-state reaction method and characterized comparatively by X-ray diffraction, scanning electron microscopy, BET surface area measurement, galvanostatic charge-discharge and AC impedance spectroscopy, respectively. The results revealed that the Li2FeSiO4/C/CNT composite exhibited much better rate performance in comparison with the Li2FeSiO4/C composite. At 0.2 C, 5 C and 10 C, the former composite electrode delivered a discharge capacity of 142 mAh g−1, 95 mAh g−1, 80 mAh g−1, respectively, and after 100 cycles at 1 C, the discharge capacity remained 95.1% of its initial value. 相似文献
19.
In order to get homogeneous layered oxide Li[Ni1/3Mn1/3Co1/3]O2 as a lithium insertion positive electrode material, we applied the metal acetates decomposition method. The oxide compounds were calcined at various temperatures, which results in greater difference in morphological (shape, particle size and specific surface area) and the electrochemical (first charge profile, reversible capacity and rate capability) differences. The Li[Ni1/3Mn1/3Co1/3]O2 powders were characterized by means of X-ray diffraction (XRD), charge/discharge cycling, cyclic voltammetry and SEM. XRD experiment revealed that the layered Li[Ni1/3Mn1/3Co1/3]O2 material can be best synthesized at temperature of 800 °C. In that synthesized temperature, the sample showed high discharge capacity of 190 mAh g−1 as well as stable cycling performance at a current density of 0.2 mA cm−2 in the voltage range 2.3-4.6 V. The reversible capacity after 100 cycles is more than 190 mAh g−1 at room temperature. 相似文献
20.
A. Sakunthala M.V. Reddy B.V.R. Chowdari P. Christopher Selvin 《Electrochimica acta》2010,55(15):4441-21480
The compounds, Li(MMn11/6)O4 (M = Mn1/6, Co1/6, (Co1/12Cr1/12), (Co1/12Al1/12), (Cr1/12Al1/12)) are synthesised by the polymer precursor method. The structure and the morphology of the compounds are studied by the Rietveld refined X-ray diffraction (XRD), and transmission electron microscopy (TEM) techniques, respectively. Density and the Brunauer, Emmet and Teller surface area (BET) of the compounds are also studied. The cobalt doped compound, Li(Co1/6Mn11/6)O4 is found to be nanosized particles in the range of 60-100 nm, when compared to the other compounds in our present study. The oxidation state and the local structure of the compounds are analysed by the X-ray absorption spectroscopy (XAS) technique. Cyclic voltammetry (CV) and the galvanostatic charge-discharge cycling (30 mA g−1) studies are made in the voltage range of 3.5-4.3 V at room temperature for all the compounds under study. The bare and (Co1/6), and (Co1/12Cr1/12) substituted spinels are cycled at high current rates of 1, 2 and 5C (assuming 1C∼120 mA g−1). Cycling results of Co-substituted spinels show better and long-term capacity retention at all the current rates. At the end of the second cycle, Li(Co1/6Mn11/6)O4 compound delivers a discharge capacity value of 100 (±3) and 87 (±3) mAh g−1 for the current rate of 2 and 5C, respectively. An excellent capacity retention value of 94% is observed at the end of the 1000 cycles for both 2 and 5C rates. 相似文献