LiFe0.5Mn0.5PO4/C prepared using a novel colloidal route as a cathode material for lithium batteries (original) (raw)
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Pure lithium iron phosphate (LiFePO 4 ) and carbon-coated LiFePO 4 (C-LiFePO 4 ) cathode materials were synthesized for Li-ion batteries. Structural and electrochemical properties of these materials were compared. X-ray diffraction revealed orthorhombic olivine structure. Micro-Raman scattering analysis indicates amorphous carbon, and TEM micrographs show carbon coating on LiFePO 4 particles. Ex situ Raman spectrum of C-LiFePO 4 at various stages of charging and discharging showed reversibility upon electrochemical cycling. The cyclic voltammograms of LiFePO 4 and C-LiFePO 4 showed only a pair of peaks corresponding to the anodic and cathodic reactions. The first discharge capacities were 63, 43, and 13 mAh/g for C/5, C/3, and C/2, respectively for LiFePO 4 where as in case of C-LiFePO 4 that were 163, 144, 118, and 70 mAh/g for C/5, C/3, C/2, and 1C, respectively. The capacity retention of pure LiFePO 4 was 69% after 25 cycles where as that of C-LiFePO 4 was around 97% after 50 cycles. These results indicate that the capacity and the rate capability improved significantly upon carbon coating.
Low temperature synthesis of nanostructured LiFePO4/C cathode material for lithium ion batteries
Materials Research Bulletin, 2020
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Insertion properties of LiFe0.5Mn0.5PO4 electrode materials for Li-ion batteries
Ionics, 2008
This paper addresses the synthesis structural and electrochemical properties of LiFe 0.5 Mn 0.5 PO 4 electrode materials for Li-ion batteries. The charge-discharge reaction of Li/LiPF 6-EC-DEC/LiFe 0.5 Mn 0.5 PO 4 cell carried out at the 1-C rate shows a capacity retention of 128 mAh/g. The local structure of the delithiated Li x Fe 0.5 Mn 0.5 PO 4 phases have been studied by Fourier transform infrared spectroscopy and magnetometry. Spectral features indicate that the structure of the delithiated phase remains in the orthorhombic system. The compositional dependence of the magnetic moment is found to be in quantitative agreement with the theoretical value predicted for oxidation of M 2+ ions in the high spin state.
Journal of Alloys and Compounds, 2018
A LiFe 0.5 Mn 0.3 Co 0.2 PO 4 /C composite cathode material was prepared using a solid-state ball-milling method. The flower-like Co 3 O 4 precursor was prepared by hydrothermal method and used to improve the electrochemical properties of composite material. The galvanostatic charge-discharge profile is performed in the potential range of 2-5 V by using different electrolyte compositions with/without 1wt.% trimethyl boroxane (TMB) additive at various C rates. The highest discharge capacities of the composite material were 150.42 mAh g-1 at 0.1C and 120 mAh g-1 at 1C in LiPF 6 +1wt%TMB in EC:EMC (1:2, v/v). In addition, the excellent cycle-life was observed at 0.1C and 1C rate for 30 and 100 cycles with the charge retention of 97.7% and 73%, respectively. These appreciable results were obtained due to the carbon coating layer and highly active composite material. The thickness of cathode electrolyte interphase layer on composite electrode is ca. 3 nm which was measured by secondary ion mass spectroscopy. And also, we found that the B element on interphase layer that acts as F-scavenger to reduce the amount of LiF formation over cathode interphase layer. As a result, it can markedly reduce the charge transfer resistance and improve the electrochemical performance for long-term cycling.
2011
CITATIONS 3 READS 69 4 authors, including: Some of the authors of this publication are also working on these related projects: Synthesis and studies on controlled porosity composite thin layers and systems for energy storage and conversion applications View project Research Cooperation Project: Synthesis and studies on controlled porosity composite thin layers and systems for energy storage and conversion applications (2014-2017) View project
A new process is developed for preparation of conductive carbon coated LiFePO 4. Excess lithium significantly improved the electrochemical performance of LiFePO 4. M€ ossbauer spectroscopy identifies the presence of new impurity phases. LiFePO 4 with excess lithium made in presence of surfactant is a promising cathode. a b s t r a c t We have synthesized carbon coated LiFePO 4 (C-LiFePO 4) and C-Li 1.05 FePO 4 with 5 mol% excess Li via sol egel method using oleic acid as a source of carbon for enhancing electronic conductivity and reducing the average particle size. Although the phase purity of the crystalline samples was confirmed by x-ray diffraction (XRD), the 57 Fe M€ ossbauer spectroscopy analyses show the presence of ferric impurity phases in both stoichiometric and non-stoichiometric C-LiFePO 4 samples. Transmission electron microscopy measurements show nanosized C-LiFePO 4 particles uniformly covered with carbon, with average particle size reduced from ~100 nm to ~50 nm when excess lithium is used. Electrochemical measurements indicate a lower charge transfer resistance and better electrochemical performance for C-Li 1.05 FePO 4 compared to that of C-LiFePO 4. The aim of this work is to systematically analyze the nature of impurities formed during synthesis of LiFePO 4 cathode material, and their impact on electrochemical performance. The correlation between the morphology, charge transfer resistance, diffusion coefficient and electro-chemical performance of C-LiFePO 4 and C-Li 1.05 FePO 4 cathode materials are discussed.
Journal of Applied Electrochemistry, 2014
LiFePO 4 /C and LiFe 0.96 Pt 0.04 PO 4 /C nanocomposite cathode materials were synthesized using the sol-gel method in a nitrogen atmosphere. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Their electrochemical properties were investigated using galvanostatic charge/discharge tests, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The XRD results indicate that substituting iron with platinum does not destroy the structure of LiFePO 4 , but expands the lattice parameters and enlarges the cell volume. The electrochemical results show that platinum doping improves the electrochemical performance of LiFePO 4 /C particles owing to the expansion of the lattice structure, which provides more space for Li ion diffusion. The, larger lattice structure parameters of the LiFe 0.96 Pt 0.04 PO 4 /C material result in a high discharge capacity of 166, 156, 142 and 140 mAh g -1 at rates of 0.2, 1, 5, and 10 C, respectively, as compared to 164, 150, 120, and 105 mAh g -1 for undoped LiFePO 4 /C.
Nanostructured high specific capacity C-LiFePO 4 cathode material for lithium-ion batteries
We report synthesis of nanosize LiFePO 4 and C-LiFePO 4 powders with a narrow particle size distribution (20-30 nm) by ethanol-based sol-gel method using lauric acid (LA) as a surfactant for high specific capacity lithium-ion battery cathode material. X-ray diffraction measurements demonstrated that the samples were single-phase materials without any impurity phases. The average crystallite size was found to decrease slightly from 29 nm to approximately 23 nm with carbon coating. The ratio of the Raman D-band (;1350 cm À1 ) to G-band (;1590 cm À1 ) intensities (I D /I G ) and electronic conductivity of these materials show strong dependence on the amount of surfactant coverage. Remarkably, cell prepared with carbon-coated LiFePO 4 synthesized using 0.25 M solution of LA showed a very large specific capacity approaching the theoretical limit of 170 mAh/g, in stark contrast to the specific capacity of cell consisting of pure of LiFePO 4 (;75 mAh/g) measured at the same C/2 discharge rate.
Carbon-coated LiFePO 4 (C-LiFePO 4 ) nanocomposites particles have been scale-up synthesized by a direct and economic solid-state reaction process. A variety of analytical techniques such as X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM, TEM, HRTEM, and HAADF), and selected area electron diffraction (SAED) are applied to investigate particles morphologies and phase structures on the nanometer scale. Single crystal and an olivine structure of the rough spherical LiFePO 4 are confirmed by XRD pattern, HRTEM images and SAED patterns. The details of the coating including carbon content, thickness, and structure are particularly studied by energy filtered EF-TEM imaging, electron energy-loss spectroscopy (EELS) analysis, and X-ray photoelectron spectroscopy (XPS) analysis. The size distribution is estimated at 50-200 nm from XRD analysis and TEM images. An average 4.2% carbon content is measured and a homogenous 3 nm carbon thick layer on the particles surfaces is clearly revealed by HRTEM and EF-TEM imaging. An amorphous carbon structure was further confirmed by both EELS and XPS valence analysis. The characteristics of these nanostructures and the amorphous carbon-coating has been demonstrated to improve the electronic conductivity and cell performance by reducing the path of both electron transfer and lithium ions diffusion while the C-LiFePO 4 cathode is used in the battery cell. Electrochemical performance has been evaluated by cyclic voltammetry (CV), and galvanostatic charge/discharge cycling, and AC impedance spectroscopy (EIS). The C-LiFePO 4 particles exhibited improved electric conductivity, good rate capability, capacity retention, and cycling performance and superior discharge capacity with delivery of almost 99% of its theoretical discharge capacity of 168 mAh/g at a C/10 rate with a high coulomb efficiency. The CV profiles show that lithium ions and electrons are quite active during two-phase kinetic reaction, which could be attributed to the smaller particles and carbon-coating layer that facilitated extraction and insertion of lithium ions and electrons transfers, thereby is beneficial to the kinetic behavior and improving electrochemical performance during charge-discharge