Electrochemical Performance of Carbon Modified LiNiPO4 as Li-Ion Battery Cathode: A Combined Experimental and Theoretical Study (original) (raw)
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Journal of Sol-Gel Science and Technology, 2017
Acetates of lithium (LiC 2 H 3 O 2) and nickel (NiC 2 H 3 O 2) together with ammonium dihydrogen phosphate (NH 4)H 2 PO 4 were used as starting materials to prepare LiNiPO 4 cathode materials via sol-gel technique. This simple and effective method of using distilled water as main solvent was assisted by small amount of oxalic acid. Final product was obtained after sintering process at temperatures of 500°C, 600°C, 700°C, and 800°C for 3 h. The peaks in X-ray diffraction patterns reveal ordered olivine structure of LiNiPO 4 under Pnma space group. The surface morphologies as in field emission scanning electron microscopy images clearly showed complete formation of LiNiPO 4 with uniform size distribution. Charge-discharge tests recorded initial discharge capacities of 97.3 mAh g −1 and 91.1 mAh g −1 for LiNiPO 4 obtained at sintering temperatures of 700 and 800°C respectively in the voltage range 2.5-4.5 V. Insitu carbon coating during synthesis improved electrochemical performances of LiNiPO 4. Sintering temperature 700°C produced smaller LiNiPO 4 particles compared to 800°C, which enables good capacity retention.
Journal of Asian Ceramic Societies, 2016
Olivine-type LiNiPO 4 has been considered as a most competitive positive electrode active material for lithium-ion batteries. In the present paper, the LiNiPO 4 and Co-doped LiNi 0.5 Co 0.5 PO 4 are synthesized by solid-state reaction method under air atmosphere. All the X-ray diffraction peaks of both the compounds are indexed and it is found that the samples are well crystallized in orthorhombic olivine structure belonging to the space group Pnma. The crystallite size is calculated from the Scherrer formula and it is found to be 6.918 and 4.818 nm for pure and doped samples, respectively. The surface morphology and grain sizes of the materials are investigated through scanning electron microscope. Presence of preferred local cation environment is understood from Fourier transform infrared spectroscopy (FTIR) studies. The conductivity and dielectric analysis of the samples are carried out at different temperatures and frequencies using the complex impedance spectroscopy technique. The electrical conductivity of LiNi 0.5 Co 0.5 PO 4 is higher than that of pure LiNiPO 4 .
Characterization of Nanocathode Material for Rechargeable Lithium Ion Battery
International Journal of Engineering Research and, 2016
Li-ion batteries are one of the most commercialized solutions to store electrochemical energy, but until now their broad use is limited to small electronic devices. During the past few years, much attention was focused on cathode materials with either high voltage or high capacity coupled with high stability. In the present work, we focused on the synthesis and characterization of LiNiPO4 and lanthanum-doped LiNiPO4 prepared by Pechini-type precursor method. The X-ray diffraction analysis confirms the formation of compounds LiNiPO4 and lanthanum-doped LiNiPO4 with orthorhombic structure. The Fourier transform infra-red analysis has been made to confirm the formation of Li1-yLayNiPO4 (y = 0.05, 0.07, 0.09 mol%). From AC impedance analysis, it is found that the undoped LiNiPO4 has ionic conductivity of 8.13×10-09 S cm-1 and the La-doped sample (Li0.93La0.07NiPO4) has maximum conductivity of 3.83×10-08 S cm-1 at ambient temperature. This value is one order greater than that of the undoped LiNiPO4.
A Review: Carbon Additives in LiMnPO4- and LiCoO2-Based Cathode Composites for Lithium Ion Batteries
Batteries
Carbon plays a critical role in improving the electronic conductivity of cathodes in lithium ion batteries. Particularly, the characteristics of carbon and its composite with electrode material strongly affect battery properties, governed by electron as well as Li+ ion transport. We have reviewed here various types of carbon materials and organic carbon sources in the production of conductive composites of nano-LiMnPO4 and LiCoO2. Various processes of making these composites with carbon or organic carbon sources and their characterization have been reviewed. Finally, the type and amount of carbon and the preparation methods of composites are summarized along with their battery performances and cathode materials. Among the different processes of making a composite, ball milling provided the benefit of dense and homogeneous nanostructured composites, leading to higher tap-density and thus increasing the volumetric energy densities of cathodes.
Materials Today: Proceedings, 2019
LiNiPO 4 is one of the cathode Lithium-Ion Batteries (LiB) with olivine structure which has the potential to improve LiB performance, because highest operating voltage. The phase of olivine structure with high purity plays an important role in electrochemical properties of LiB. In this research, LiNiPO 4 materials were synthesized with temperature sintering at 900 C using solid-state reaction method to get high purity samples. Moreover, LiNiPO 4 samples were coated with sucrose as a carbon source to increase of ionic conductivity. The samples were characterized by an investigation of phase and microstructure with Xray Diffraction, X-Ray Fluorescence and Fourier Transform Infrared Spectroscopy.
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.
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.
Electrochemical performance of nanocomposite LiMnPO4/C cathode materials for lithium batteries
Electrochemistry Communications, 2010
A LiMnPO 4 /C composite cathode was prepared by a combination of spray pyrolysis and wet ball milling. The cathode showed stable performance at various cutoff voltages up to 4.9 V. The cutoff voltage increase up to 4.9 V allowed the achievement of a high discharge capacity in galvanostatic charge-discharge tests. The discharge capacities of 153 mAh g -1 at 0.05C and 149 mAh g -1 at 0.1C were achieved at room temperature; the trickle-mode discharge capacities at room temperature were 132, 120 and 91 mAh g -1 at 0.1, 1 and 5C discharge rates, respectively. The cell exhibited a good rate capability in the galvanostatic cycling up to 5C discharge rate at both ambient temperature and 50 o C.
Electrochemistry Communications, 2009
LiCo 1Àx Fe x PO 4 /C composites with various amounts of Fe (x = 0, 0.05 and 0.1) were synthesized by vibrant type ball-milling coupled with microwave heating to investigate the role of doped Fe 2+ in LiCo 1Àx Fe x PO 4 /C composites. The initial charge-discharge curves and cyclic voltammetry profiles of LiCo 1Àx Fe x PO 4 /C composites apparently featured an improved kinetic property compared to LiCoPO 4. It was observed that the initial discharge capacity (120 mA hg À1) of LiCo 0.95 Fe 0.05 PO 4 is higher than that (108 mA hg À1) of LiCoPO 4 and the difference between the oxidation-reduction peaks is getting smaller with the increase of Fe doping. The electrochemical improvement in LiCo 1Àx Fe x PO 4 /C composites could be attributed to the enhanced Li + diffusivity induced by the enlargement of 1D channel in polyanion structure of LiCoPO 4 .