Conductive additive content balance in Li-ion battery cathodes: Commercial carbon blacks vs. in situ carbon from LiFePO4/C composites (original) (raw)
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Electrochemical and Solid-State Letters, 2005
The electrochemical properties of LiFePO 4 cathodes with different carbon contents were studied to determine the role of carbon as conductive additive. LiFePO 4 cathodes containing from 0 to 12% of conductive additive ͑carbon black or mixture of carbon black and graphite͒ were cycled at different C rates. The capacity of the LiFePO 4 cathode increased as conductive additive content increased. Carbon increased the utilization of active material and the electrical conductivity of electrode, but decreased volumetric capacity of electrode. This composition ͑LiFePO 4 with 3 wt % of carbon and 3 wt % of Graphite͒ is suitable for HEV application.
Journal of Physics and Chemistry of Solids, 2008
Carbon-coated LiFePO 4 (LiFePO 4 /C) composite cathode-active materials of submicron size and phase-pure olivine structure were synthesized by a mechanical activation (MA) process. The conductive carbon coating was achieved by addition of (i) carbon powder directly or (ii) sucrose as the carbon precursor, during synthesis. LiFePO 4 /C containing 6 wt% carbon prepared by the two methods showed good electrochemical properties as cathodes in lithium batteries at room temperature with high active material utilization of 494% at 0.1 C rate and stable cycle performance. The sucrose precursor method leads to the formation of a thin, porous and more uniform carbon coating around the particles and results in a slightly higher discharge capacity ($3%) compared to the other sample.
Performance improvement on LiFePO4/C composite cathode for lithium-ion batteries
Solid State Sciences, 2013
Temperature glycine assisted solid-state synthesis was used to prepare LiFePO 4 /C composite samples with two types of material improvements. It will be shown how can addition of a high conductive support as well as doping with supervalent metal ions improve the electrochemical performance of Li-ion cathode. Three samples with different properties were prepared and investigated e pure LiFePO 4 / C with no material improvements, LiFePO 4 /C prepared with multi walled carbon nanotubes (MWCNT) conductive support and LiFePO 4 /C doped by 1% of cobalt. Glycine was used as inorganic carbon coating precursor during the synthesis of all samples. XRD measurements confirmed production of highly crystalline LiFePO 4 cathode material with diameter varying between 40 nm and 200 nm. Electrochemical measurements confirmed increasing the intra-particle conductivity by MWCNT or Co doping. Galvanostatic battery testing shows that LiFePO 4 /MWCNT/C composite delivers highest capacity 130 mA h g À1 at C/5. LiFePO 4 /MWCNT/C cathode material prepared by solid state synthesis exhibit excellent electrochemical performances, improved conductivity, and good rate capability compared to the LiFePO 4 /C composite material.
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.
International Journal of Sustainable Transportation Technology
The application of reduced carbon anode layer and LiFePO4 cathode was conducted in laboratory-scale battery. Both electrodes were fabricated into lithium - ion battery with LiCl electrolyte in both gel and liquid based. The carbon was prepared by using Hummer method and solvent sonification to exfoliate the carbon layer from biocarbon. The battery performance tests were carried out in potentiostat for Cyclic Voltammetry (CV) and galvanostatic measurements. The highest current of CV measurement can be obtained in the battery with reduced carbon layer anode and 20% of liquid electrolyte. It was calculated that the same battery produced the highest energy and power. Current - Voltage profile is relatively stable in CV of batteries with 40% electrolytes in both gel and liquid media. All batteries have two peaks in both anodic and cathodic. The reduction peaks show in around 0.5 and 1.5 volts. The cathodics show in around –0.5 and –1.5 volts. The best power and energy values are given by...
Springer Proceedings in Physics, 2019
LiFePO4 is a potential cathode material for its application in Li-ion batteries to provide high energy density, high power density and flat discharge voltage which are the basic requirements of underwater electric vehicles. It is non toxic, low cost, safe and environmentally benign material with high operating voltage (~3.4 V vs. Li). Although it has a high specific theoretical capacity (170 mAh/g), its discharge capacity is highly influeced by the method of preparation and mixing sequence of the ingredients of composite slurry for coating of electrode. In the present work, the electrode slurry is prepared by two different methods namely conventional method and conductive glue method. CR2032 coin cells in half cell configuration are fabricated using the electrodes prepared by both these methods. Electrochemical characterization of these half cells is carried out using cyclic voltammetry, AC-impedance, charge-discharge characteristics and specific capacity studies. It is found that c...
The role of carbon black distribution in cathodes for Li ion batteries
Journal of Power Sources, 2003
The influence of carbon black distribution/arrangement in cathode composite on cathode performance is studied using three types of active materials: LiMn 2 O 2 -spinel, LiCoO 2 , and LiFePO 4 . To the active materials, carbon black is added in two different ways: (a) using a conventional mixing procedure and (b) using a novel coating technology (NCT) invented in our laboratory. Different technologies yield different arrangement (distribution) of carbon black around active particles. It is shown that the uniformity of carbon black distribution affects significantly the cathode kinetics, regardless of the type of active particles used. A simple model explaining the influence of carbon black distribution on cathode kinetics is presented. #
In the present study, we have developed a simple and cost-effective approach for the synthesis of carbon coated LiFePO 4 wherein different carbon precursors were used to find out the suitable precursor for carbon coating. Initially, the appropriate amount of Li, Fe, and P precursors and carbon source (glucose/sucrose/fructose) were dissolved in ethanol solution followed by hydrothermal treatment at 180 C to obtain carbon coated LiFePO 4. The structure and morphological analysis of in-situ carbon coated LiFePO 4 revealed the formation of thin and homogeneous carbon layer on crystalline single-phase LiFePO 4 particles with fructose used as carbon precursor. Raman analysis confirms the presence of more ordered graphitic carbon and the I D /I G ratio is 1.01, 0.69 and 0.87 for C-LFP-S, C-LFP-F and C-LFP-G respectively, indicating that fructose assisted in-situ carbon coating leads to the formation of more ordered carbon coating on LiFePO 4 with high graphitization degree in comparison with carbon coating by glucose and sucrose. HR-TEM results revealed the presence of uniform carbon distribution, which encapsulates the crystalline LiFePO 4 particles forming a core-shell structure in the presence of fructose as carbon precursor. C-LFP-S delivered a capacity of 125 mAh/g at 0.1 C rate but then due to non-uniform carbon layer distribution, the capacity faded out completely when tested at higher Crates. Whereas C-LFP-F delivered a discharge capacity of 98 mAh/g at 0.1 C and 48 mAh/g at 1 C, which is promising compared to the LiFePO 4 carbon coated using sucrose and glucose. It is concluded that LiFePO 4 carbon coated using monosacrides as carbon precursors showed better electro-chemical performance in terms of capacity and cyclic stability when compared to LiFePO 4 carbon coated using dissacrides, attributing that uniform, thin layer, and highly ordered graphitic carbon coverage on nano sized LiFePO 4 particles greatly reduces the polarization resistance and hence improving the electrochemical performance of C-LFP-F.
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.
Electrochimica Acta, 2015
Triple carbon coated LiFePO 4 composite is prepared by spray drying-carbothermal reduction (SD-CTR) method. The triple carbon sources (viz. graphene oxide, thermoplastic phenolic resin and water-solubility starch) play different roles in constructing the hierarchical conductive architecture. The structure, component and morphology of the as-obtained LiFePO 4 composites are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and Raman spectroscopy. The results indicate that, compared with double carbon coated LiFePO 4 counterparts, the triple carbon coated LiFePO 4 composite possesses smaller crystallite and high-efficiency of carbon coating such as more complete coating, lower I D /I G ratio, and better conductive architecture. Benefited from the above mentioned superiority, the triple carbon coated LiFePO 4 composite exhibits outstanding electrochemical performance, especially for high-rate capability, which reaches up to 120 mA h g −1 at 10 C.