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1.
The electrochemical lithiation-delithiation reaction was examined for LiMnPO4 in which different cations were substituted for part of Mn. The X-ray diffraction analysis indicated that LiMnPO4 is tolerant, to some extent, to substitution of Mg2+, Ca2+ and Zr4+. The substitution of Mg2+ and/or Zr4+ led to an increased reversible capacity and a reduced polarization, whereas Ca2+ substitution had a detrimental effect on the electrochemical properties. The potential transient analysis showed that LiMn0.88Mg0.1Zr0.02PO4 has higher lithium diffusivities than pure LiMnPO4, indicating facilitated diffusion kinetics in the substituted material. Upon the first charge-discharge cycle, LiMn0.88Mg0.1Zr0.02PO4 suffered less irreversible capacity loss when compared with LiMnPO4, and smaller amounts of electrolyte salt-based species were detected on the electrode surface of LiMn0.88Mg0.1Zr0.02PO4. 相似文献
2.
LiCoxMn1−xPO4/C nanocomposites (0 ≤ x ≤ 1.0) were prepared by a combination of spray pyrolysis at 300 °C and wet ball-milling followed by heat treatment at 500 °C for 4 h in 3% H2 + N2 atmosphere. X-ray diffraction analysis indicated that all samples had the single phase olivine structures indexed by orthorhombic Pmna. The lattice parameters linearly decreased with increasing cobalt content, which confirmed the existence of solid solutions. It was clearly seen from the scanning electron microscopy observation that the LiCoxMn1−xPO4/C samples were agglomerates with approximately 100 nm primary particles. The LiCoxMn1−xPO4/C nanocomposites were used as cathode materials for lithium batteries, and electrochemical performance was comparatively investigated with cyclic voltammetry and galvanostatic charge–discharge test using the Li?1 M LiPF6 in EC:DMC = 1:1?LiCoxMn1−xPO4/C cells at room temperature. The cells at 0.05 C charge–discharge rate delivered first discharge capacities of 165 mAh g−1 (96% of theoretical capacity) at x = 0, 136 mAh g−1 at x = 0.2, 132 mAh g−1 at x = 0.5, 125 mAh g−1 at x = 0.8 and 132 mAh g−1 (79% of theoretical capacity) at x = 1.0, respectively. While the first discharge capacity increased with the cobalt content at high charge–discharge rates more than 0.5 C due to higher electronic conductivity of LiCoPO4 in comparison with LiMnPO4, the cycleability of cell became worse with increasing the amount of cobalt. The existence of Mn2+ seemed to enhance the cycleability of LiCoxMn1−xPO4/C nanocomposite cathode. 相似文献
3.
To improve the cathodic performance of olivine-type LiMnPO4, we investigated the optimal annealing conditions for a composite of carbon with cation doping. Nanocrystalline and the cation-doped LiMn1−xMxPO4 (M = Ti, Mg, Zr and x = 0, 0.01, 0.05 and 0.10) was synthesized in aqueous solution using a planetary ball mill. The synthesis was performed at the fairly low temperature of 350 °C to limit particle size. The obtained samples except for the Zr doped one consisted of uniform and nano-sized particles. The performance of LiMnPO4 was much improved by an annealing treatment between 500 and 550 °C with carbon in an inert atmosphere. A small amount of metal-rich phosphide (Mn2P) was detected in the sample annealed at 900 °C. In addition, 1 at.% Mg doping for Fe enhanced the rate capability in our doped samples. The discharge capacity of LiMn0.99Mg0.01PO4/C was 146 mAh/g at 0.1 mA/cm2 and 125 mAh/g even at 2.0 mA/cm2. 相似文献
4.
LiAlxMn2−xO4 samples (x = 0, 0.02, 0.05, 0.08) were synthesized by a polymer-pyrolysis method. The structure and morphology of the LiAlxMn2−xO4 samples calcined at 800 °C for 6 h were investigated by powder X-ray diffraction and scanning electron microscopy. The results show that all samples have high crystallinity, regular octahedral morphology and uniform particle size of 100-300 nm. The electrochemical performances were tested by galvanostatic charge-discharge and cyclic voltammetry. The results demonstrate that the Al-doped LiMn2O4 can be very well cycled at an elevated temperature of 55 °C without severe capacity degradation. In particular, the LiAl0.08Mn1.92O4 sample demonstrates excellent capacity retention of 99.3% after 50 cycles at 55 °C, confirming the greatly enhanced electrochemical stability of LiMn2O4 by a small quantity of Al-doping. 相似文献
5.
Haiyan Gao Lifang Jiao Wenxiu Peng Guang Liu Jiaqin Yang Qianqian Zhao Zhan Qi Yuchang Si Yijing Wang Huatang Yuan 《Electrochimica acta》2011,(27):9961
A series of Mo-doped LiFe1−3xMoxPO4/C (x = 0.000, 0.025, 0.050, 0.100, 0.150) cathode materials are synthesized by sol–gel method. XRD, ICP and Rietveld refinement results reveal that Mo doped in the crystal lattice and probably occupied Fe site. The structure benefits the transportation of Li+ and the diffusion of Li+ in the doped materials are enhanced remarkably than that of the undoped one, which leads to excellent electrochemical performance. The doped sample with x = 0.025 exhibits the best electrochemical performance, with the initial discharge capacity of 162.3 mAh g−1 at 0.1 C rate. 相似文献
6.
Monoclinic Li3V2−xAlx(PO4)3 with different Al3+ doping contents (x = 0, 0.05, 0.08, 0.10 and 0.12) have been prepared by a facile aluminothermal reaction. Aluminum nanoparticles have been used as source for Al3+ and nucleus for Li3V2−xAlx(PO4)3 nucleation as well as reducing agent in the aluminothermal strategy. The products were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and electrochemical methods. The XRD results show that the as-obtained Li3V2−xAlx(PO4)3 has a phase-pure monoclinic structure, irrespective of the Al3+ doping concentration. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) results reveal that the charge-transfer resistance of the Li3V2(PO4)3 is reduced and the reversibility is enhanced after V3+ substituted by Al3+. In addition, The Li3V2−xAlx(PO4)3 phases exhibit better cycling stability than the pristine Li3V2(PO4)3. 相似文献
7.
Huajun Guo Xuan Cao Xiangqun Li Liming Li Xinhai Li Zhixing Wang Wenjie Peng Qihou Li 《Electrochimica acta》2010,55(27):8036-106
Li2Fe1−xMnxSi04/C cathode materials were synthesized by mechanical activation-solid-state reaction. The effects of Mn-doping content, roasting temperature, soaking time and Li/Si molar ratio on the physical properties and electrochemical performance of the Li2Fe1−xMnxSi04/C composites were investigated. The materials were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM), charge-discharge tests and AC impedance measurements. SEM images suggest that the morphology of the Li2Fe1−xMnxSi04/C composite is sensitive to the reaction temperature. Samples synthesized at different temperatures have different extent of agglomeration. Being charged-discharged at C/32 between 1.5 and 4.8 V, the Li2Fe0.9Mn0.1Si04/C synthesized at the optimum conditions shows good electrochemical performances with an initial discharge capacity of 158.1 mAh g−1 and a capacity retention ratio of 94.3% after 30 cycles. AC impendence investigation shows Li2Fe0.9Mn0.1SiO4/C have much lower resistance of electrode/electrolyte interface than Li2FeSiO4/C. 相似文献
8.
Marcella Bini Stefania Ferrari Doretta Capsoni Vincenzo Massarotti 《Electrochimica acta》2011,(6):267
The role played by the substitution of Mn on the electrochemical behaviour of Li3V2(PO4)3 has been investigated. Independently of the synthesis route, the Mn doping improves the electrochemical features with respect to the undoped samples. Different reasons can be taken into consideration to explain the electrochemical enhancement. In the sol–gel synthesis the capacity slightly enhances due to the Mn substitution on both the V sites, within the solubility limit x = 0.124 in Li3V2−xMnx(PO4)3. In the solid state synthesis the significant capacity enhancement is preferentially due to the microstructural features of the crystallites and to the LiMnPO4 phase formation. 相似文献
9.
Yourong Wang Yafang Chen Siqing Cheng Liangnian He 《Korean Journal of Chemical Engineering》2011,28(3):964-968
Olivine structure LiMnPO4/C as cathode materials for Li-ion batteries were synthesized via a simple solidstate reaction. Improvement of the electrochemical
performance of LiMnPO4/C cathode material was realized significantly by the method of doping Zn. The obtained LiMn0.95Zn0.05PO4/C electrode material was studied by the measurements of X-ray diffraction pattern, scanning electronic microscopy, electrochemical
impedance spectroscopy and electrochemical performance. The results indicate that the LiMn0.95Zn0.05PO4/C materials exhibit discharge specific capacity of 140.2 mA h g−1 at 0.02 C rate and better rate capability. These excellent results are elucidated by EIS test, which showed that there was
the decrease of charge transfer resistance and faster lithium-ion diffusion in LiMnPO4/C cathode materials after Zn doping. 相似文献
10.
LiFe1−xNdxPO4/C (x = 0-0.08) cathode material was synthesized using a solid-state reaction. The synthesis conditions were optimized by thermal analysis of the precursor and magnetic properties of LiFePO4/C. The structure and electrochemical performances of the material were studied using XRD, FE-SEM, EDS, electrochemical impedance spectroscopy and galvanostatic charge-discharge. The results show that a small amount of aliovalent Nd3+ ion-dopant substitution on Fe2+ ions can effectively reduce the particle size of LiFePO4/C. Cell parameters of LiFe1−xNdxPO4 (x = 0.04-0.08) were calculated, and the results showed that LiFe1−xNdxPO4/C had the same olivine structure as LiFePO4. LiFe0.4Nd0.6PO4/C delivers the discharge capacity of 165.2 mAh g−1 at rate of 0.2 C and the capacity retention rate is 92.8% after 100 cycles. Charge-transfer resistance decreases with the addition of glucose and Nd3+ ions. Poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) was synthesized and PZS nanorods were used as a carbon source to coat LiFePO4. All of the results show that aliovalent doping substitution of Fe in LiFePO4 is well tolerated. 相似文献
11.
M. Llusar J.A. BadenesA. García C. GargoriR. Galindo G. Monrós 《Ceramics International》2011,37(2):493-504
Solid solutions of mixed metal Mn3−xMgxFe4(PO4)6 orthophosphates (x = 0, 0.5, 1, 1.5, 2, 2.5, and 3) were prepared for the first time (from coprecipitate powders calcined up to 1000 °C) and characterized by thermal analysis, XRD, SEM/EDX, UV-vis-NIR spectroscopy and colour measurements (CIE-L*a*b*). Orthophosphate (Mn,Mg)3−yFe4+z(PO4)6 solid solutions isotypic to Fe7(PO4)6 structure (triclinic P-1(2) spatial group) formed successfully as the major crystalline phase within the studied range of compositions, accompanied only by variable quantities of α- and/or β-Mg2P2O7 diphosphates as secondary phases. Noteworthy, the obtained solid solutions were tested as potential ceramic dyes and exhibited an interesting interaction upon enamelling within a double-firing ceramic glaze: considerable amounts of Fe segregated from the solid solutions to be stabilized as hematite particles (α-Fe2O3) in the ceramic glaze and conferring the glaze an intense dark-brown colouration, which was almost independent of the amount of Mg doping. Thus, the obtained solid solutions with a minimized Mn content (especially Mg3Fe4(PO4)6 composition, without Mn) could serve as low-toxicity Fe reservoirs to stabilize hematite in double-firing glazes and produce an interesting dark-brown colouration, being an alternative to other brown ceramic pigments containing hazardous metals (i.e. Cr, Ni, Zn, or Sb). 相似文献
12.
Nanocrystalline LiFe1−xSnxPO4 (0 ≤ x ≤ 0.07) samples are synthesized using SnCl4·5H2O as dopant via an inorganic-based sol–gel method. The dependency of the physicochemical and electrochemical properties on the doping amount of tin are systemically worked out and regular changes are revealed. In the whole concentration range, the chemical valence of Fe2+ is not basically changed whereas tin is found in two different oxidation states, namely +2 and +4. The replacement of Fe2+ by supervalent Sn4+ would lead to electron compensation. Under the synergetic effects between the charge compensation and the crystal distortion, the electrical conductivities for the bulk samples first increase and then decrease with the increasing amount of Sn doping. Upon the doping amount, the apparent lithium-ion diffusion coefficient and the electrochemical performance also display the similar trends. The doping is beneficial to refine the particle size and narrow down the size distribution, however optimizing the doping amount is necessary. Compared with other samples, the sample with a doping amount of about 3 mol% delivers the highest capacities at all C-rates and exhibits the excellent rate capability due to the high electrical conductivity and the fast lithium-ion diffusion velocity. 相似文献
13.
《Ceramics International》2020,46(8):11698-11704
To successfully recycle spent LiFePO4 and LiMn2O4 batteries and simultaneously produce high performances nano-LiMnxFe1-xPO4/C powders, a mechanical activation-assisted method was effectively applied in the recycling process. The technique consists of the separation and purification of spent cathode materials, high-energy mechanical mixing of raw materials and a commonly used heat treatment processes. The structural and morphological characterization results indicate that nano-sized LiMnxFe1-xPO4/C composites with uniform amorphous carbon coatings were successfully synthesized from spent LiFePO4 and LiMn2O4 batteries. The electrochemical performance testing results show that the recovered nano-LiMnxFe1-xPO4/C cathodes possess promising Li-ion storage properties. LiMn0.5Fe0.5PO4/C displays high capacities of 143.2, 138.1, and 127.6 mAh g−1 at 0.1, 1, and 2C rates, respectively. The obtained cathodes also show outstanding cycling stabilities of 98.47% and 97.58% for LiMn0.5Fe0.5PO4/C and LiMn0.8Fe0.2PO4/C after 100 cycles, respectively. This work indicates that recycling spent LiFePO4 and LiMn2O4 to produce high-performance LiMnxFe1-xPO4/C is a promising strategy for recycling spent LiFePO4 and LiMn2O4 based lithium ion batteries (LIBs) in an efficient and environmentally friendly manner. 相似文献
14.
X.H. Rui 《Electrochimica acta》2009,54(12):3374-3380
The carbon-coated monoclinic Li3V2(PO4)3 (LVP) cathode materials were synthesized by a solid-state reaction process under the same conditions using citric acid, glucose, PVDF and starch, respectively, as both reduction agents and carbon coating sources. The carbon coating can enhance the conductivity of the composite materials and hinder the growth of Li3V2(PO4)3 particles. Their structures and physicochemical properties were investigated using X-ray diffraction (XRD), thermogravimetric (TG), scanning electron microscopy (SEM) and electrochemical methods. In the voltage region of 3.0-4.3 V, the electrochemical cycling of these LVP/C electrodes all presents good rate capability and excellent cycle stability. It is found that the citric acid-derived LVP owns the largest reversible capacity of 118 mAh g−1 with no capacity fading during 100 cycles at the rate of 0.2C, and the PVDF-derived LVP possesses a capacity of 95 mAh g−1 even at the rate of 5C. While in the voltage region of 3.0-4.8 V, all samples exhibit a slightly poorer cycle performance with the capacity retention of about 86% after 50 cycles at the rate of 0.2C. The reasons for electrochemical performance of the carbon coated Li3V2(PO4)3 composites are also discussed. The solid-state reaction is feasible for the preparation of the carbon coated Li3V2(PO4)3 composites which can offer favorable properties for commercial applications. 相似文献
15.
A LixMnPO4 (x = 1.0–0.15) composite cathode was investigated by Fourier-transform infrared spectroscopy at different states of charge. Significant spectral changes of the PO43− vibrations, which are correlated with the Jahn–Teller distortion of Mn3+ in MnPO4 and the 3rd ionization potential of Mn, were observed upon electrochemical delithiation of LiMnPO4. The presence of two sets of peaks observed in the series of delithiated LixMnPO4 spectra is consistent with a two-phase process for delithiation. These results provide insight into the structural changes that occur during lithium extraction and insertion in LiMnPO4. 相似文献
16.
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
17.
We report the electrical conductivity properties of solid-state synthesized perovskite-like La0.8Sr0.2Ga0.8Mg0.2O2.80 (LSGM) and LSGM-SrSn1−xFexO3 (x = 0.8; 0.9) composites. LSGM exhibits both bulk and grain-boundary contribution in the ac impedance plots. The grain-boundary conductivity (σgb) is slightly (≤half-order of magnitude) higher than that of the bulk oxide ion conductivity (σbulk). Powder XRD study reveals that no chemical reaction occurs between LSGM and SrSn1−xFexO3 (1:1 wt.%) at 1000 °C (48 h) and forms a single-phase perovskite-like compound at 1300 °C (48 h) in air, while in hydrogen atmosphere, at 800 °C for 48 h, a growth of LaSrGaO4 and LaSrGa3O7 impurity phases and formation of metallic Fe was observed. The LSGM-SrSn1−xFexO3 (x = 0.8; 0.9) composites show a single or part of semicircle in air at low-temperature regime. The electrical conductivity of the composites were found to be much higher compared to pure LSGM and lower about an order of magnitude than those of pure Sn-doped SrFeO3 perovskite. 相似文献
18.
Li3V2(PO4)3/C composite cathode material was synthesized via carbothermal reduction process in a pilot scale production test using battery grade raw materials with the aim of studying the feasibility for their practical applications. XRD, FT-IR, XPS, CV, EIS and battery charge-discharge tests were used to characterize the as-prepared material. The XRD and FT-IR data suggested that the as-prepared Li3V2(PO4)3/C material exhibits an orderly monoclinic structure based on the connectivity of PO4 tetrahedra and VO6 octahedra. Half cell tests indicated that an excellent high-rate cyclic performance was achieved on the Li3V2(PO4)3/C cathodes in the voltage range of 3.0-4.3 V, retaining a capacity of 95% (96 mAh/g) after 100 cycles at 20C discharge rate. The low-temperature performance of the cathode was further evaluated, showing 0.5C discharge capacity of 122 and 119 mAh/g at −25 and −40 °C, respectively. The discharge capacity of graphite//Li3V2(PO4)3 batteries with a designed battery capacity of 14 Ah is as high as 109 mAh/g with a capacity retention of 92% after 224 cycles at 2C discharge rates. The promising high-rate and low-temperature performance observed in this work suggests that Li3V2(PO4)3/C is a very strong candidate to be a cathode in a next-generation Li-ion battery for electric vehicle applications. 相似文献
19.
Gang Yang Haidong Liu Hongmei Ji Zhongzhong Chen Xuefan Jiang 《Electrochimica acta》2010,55(8):2951-198
Monoclinic Li3V2(PO4)3 can be rapidly synthesized at 750 °C for 5 min (MW5m) by using microwave solid-state synthesis method. The refined cell parameters and atomic coordination of the sample MW5m show some deviations compared with those of the sample synthesized in conventional solid-state synthesis method, especially the coordinate of Li atoms. Compared with the electrochemical properties of the carbon-coating sample Li3V2(PO4)3, the carbon-free sample MW5m presents well electrochemical properties. In the cut-off voltage of 3.0-4.3 V, MW5m sample presents a specific charge capacity of 132 mAh g−1, almost equivalent to the reversible cycling of two lithium ions per Li3V2(PO4)3 formula unit (133 mAh g−1), and specific discharge capacity of 126.4 mAh g−1. In the cut-off voltage of 3.0-4.8 V, MW5m shows an initial specific discharge capacity of 183.4 mAh g−1 at 0.1 C, near the theoretical discharge capacity. In the cycle performance, the capacity fade of Li3V2(PO4)3 is dependent on the cut-off voltage and the preparation method, more capacity lost at relatively higher charge/discharge voltage. The reasons for the excellent electrochemical properties of Li3V2(PO4)3 rapidly synthesized in microwave field are discussed in detail. 相似文献
20.
《Ceramics International》2017,43(3):3190-3195
Three-dimensional (3D) olivine LiMn0.8Fe0.2PO4 nanoflowers constructed by two-dimensional (2D) nanoflakes have been successfully synthesized through an easy liquid phase method. Hierarchical LiMn0.8Fe0.2PO4/C could be easily formed via a liquid coating technology and subsequent calcination treatment. When acting as cathode materials for lithium ion batteries, the LiMn0.8Fe0.2PO4/C nanoflowers show excellent rate performance and cycle stability. The unique flower-like hierarchical structured LiMn0.8Fe0.2PO4 and thin carbon coating outside make this composite a promising candidate as cathode materials for lithium ion batteries. 相似文献