Characterization of anodes for lithium-ion batteries (original) (raw)
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Ionics, 2013
Artificial graphite anode material was modified by coating an amorphous carbon layer on the particle surface via a sol-gel and pyrolysis route. The electrochemical measurements demonstrate that appropriate carbon coating can increase the specific capacity and the initial coulombic efficiency of the graphite material, while excessive carbon coating leads to the decrease in specific capacity. Thick coating layer is obviously unfavorable for the lithium ion diffusion due to the increased diffusion distance, but the decreased specific surface area caused by carbon coating is beneficial to the decrease of initial irreversible capacity loss. The sample coated with 5 wt.% glucose exhibits a stable specific capacity of 340 mAhg −1 . Carbon coating can remarkably enhance the rate capability of the graphite anode material, which is mainly attributed to the increased diffusion coefficient of lithium ion.
Carbon-based anode materials for lithium-ion batteries
Lithium-Sulfur Batteries
Physical characterisation of tin-graphite composites 6.3.2 Electrochemical measurement of Sn-graphite composite electrodes 6.4 Conclusions CHAPTER 7. ELECTROCHEMICAL CHARACTERISTICS OF TIN-COATED MCMB GRAPHITE AS ANODE IN LITHIUM-ION CELLS 7.1 Introduction 7.2 Experimental 7.3 Results and discussion 7.4 Conclusion CHAPTER 8. GENERAL CONCLUSIONS
Effect of Solid Content in Electrochemical Performance of Graphite Anode of Lithium-ion Batteries
Journal of Technomaterial Physics
Rechargeable batteries have been implemented in most portable electronic devices. Lithium-ion battery (LIB), as the main power source, dominates the mobile device market due to its high energy density, long shelf life, and environmentally friendly operation. In the rechargeable lithium-ion battery, there are four main components, one of which is the anode. The anode material used is commercial graphite. Thus, this study aims to determine the effect of solid content solvents on battery performance. The main discussion in this study is to analyze the effect of solvent variations of N, N Dimethyl Acetamide (DMAC) on the characteristics of the sheet and the difference in solid content of graphite anode sheets on battery performance. Identification of the formed phase was carried out by XRD, reduction and oxidation reactions by cyclic voltammetry test, battery capacity by charge/discharge test, and study of the electrochemical characteristics of the electrode material by electrochemical ...
Performance of modified graphite as anode material for lithium-ion secondary battery
Carbon letters
Two different types of graphite, such as flake graphite (FG) and spherical graphite (SG), were used as anode materials for a lithium-ion secondary battery in order to investigate their electrochemical performance. The FG particles were prepared by pulverizing natural graphite with a planetary mill. The SG particles were treated by immersing them in acid solutions or mixing them with various carbon additives. With a longer milling time, the particle size of the FG decreased. Since smaller particles allow more exposure of the edge planes toward the electrolyte, it could be possible for the FG anodes with longer milling time to deliver high reversible capacity; however, their initial efficiency was found to have decreased. The initial efficiency of SG anodes with acid treatments was about 90%, showing an over 20% higher value than that of FG anodes. With acid treatment, the discharge rate capability and the initial efficiency improved slightly. The electrochemical properties of the SG anodes improved slightly with carbon additives such as acetylene black (AB), Super P, Ketjen black, and carbon nanotubes. Furthermore, the cyclability was much improved due to the effect of the conductive bridge made by carbon additives such as AB and Super P.
Journal of The Electrochemical Society, 1995
Carbon is one of the best candidate materials for the negative electrode of rechargeabte lithium batteries; however, the electrochemical characteristics are not fully understood in terms of the structure of the materials. The relationship linking the volume ration of the graphitic structure (P1) of mesocarbon microbeads (MCMBs) and the electrochemical characteristics has been examined, and it was found that the capacity in the range between 0 to 0.25 V (vs. Li/Li +) in 1 tool 9-~ LiC1OJethylene carbonate (EC) + 1,2-diethoxyethane (DEE) electrolyte increased with an increase of the P1 of the MCMBs. This result shows that the lithium storage mechanism in this potential range is the lithium-intercalation reaction into the graphitic layers with the AB or ABC stacking. On the other hand, MCMB heat-treatment temperature (HTT) 1000~ showed much larger capacity in the range between 0.25 to 1.3 V than higher HTT MCMBs, and it is suggested the interaction among each graphite layer is weaker in nongraphitized carbon than that in well-graphitized ones.
Zirconia-treated natural graphite C Zr anode and cobalt-substituted spinel LiMn 1.8 Co 0.2 O 4 cathode have previously been shown to have significant rate capability and cycle stability as half-cells in Li-ion batteries. We report attempts made to optimize the electrochemical performance of the Li-ion battery based on the above anode and cathode as a potential candidate for hybrid electric vehicles. A novel approach was taken to construct the full cell which is applicable to common Li-ion batteries, i.e., precycling of the graphite electrode at slower rate vs Li metal prior to assembling against LiMn 1.8 Co 0.2 O 4. Precycling was found to be effective in delivering high steady capacity on subsequent cycling as a full cell. A Li-ion cell composed of precycled C Zr as anode and LiMn 1.8 Co 0.2 O 4 as cathode shows pronounced cycle stability and high rate capability. The high cycle stability of C Zr anode was recognized as being due to the high stability of the surface film on graphite consisting of ZrO 2. Development of rechargeable batteries for electric vehicles EVs and hybrid electric vehicles HEVs is a topic under intense investigation. In practice, it is hard to meet numerous battery performance requirements such as high specific energy, high rate capability, long life, low cost, perfect safety, and minimal environmental impact simultaneously. Compared with other batteries, Li-ion batteries are attractive in terms of specific energy and power and also have the potential to be " the battery of choice " for HEVs. However, the low rate capability, high cost, and safety performance limit its successful application. The main factors affecting the poor rate capability appears to be the carbon anode. Numerous reports in literature have explored the issue, and improved cycle ability and considerable rate capabilities have been achieved. 1-7 Recently, we reported improved rate properties by surface modification of natural graphite with zir-conia ZrO 2 using a half-cell configuration Li/C Zr and considerable rate capabilities were shown. 8 However, the origin of the high cycle stability and the rate capability of the Li/C Zr cell had not been investigated. A part of the focus of the present work is, hence, to explore the mechanism of delivering high cycle stability. In addition, despite its unique performance as a full cell, the construction of the full cell with graphite-based anodes seems to be rather complicated. This is presumably true for whatever the electrode material concerned. The main objective of the present research work was to investigate ways of optimizing the full cell consisting of C Zr as anode. It is generally known that the electrochemical properties of graphite govern the behavior of the final cell as it shows irreversibility during few initial cycles, which has generally been ascribed to the formation of surface films solid electrolyte interface SEI. In the present work, the graphite electrode was precycled at slower rate vs the Li-metal electrode prior to assembling into the full cell with a view to suppress the irreversibility of the cell. LiMn 1.8 Co 0.2 O 4 was used as the cathode material due to its proven cell stability on cycling vs parent spinel LiMn 2 O 4. 9-11 Experimental Zirconia-modified natural graphite NG was prepared as follows. 8 0.5 g of NG Kansai Chemicals, particle size 3.5 m was dispersed in 2.5 mM zirconium isopropoxide High Purity Chemicals , 98% in dehydrated isopropanol Wako, 99.5% and stirred ultrasonically for 2 h. Filtered samples were dried in a vacuum oven at 110°C for 24 h and then annealed at 500°C in air for 24 h. For comparison, NG dispersion in isopropanol was also treated under similar condition. The electrodes were prepared on Cu foil using slurry of 80% active material AM and 10% by wt each conductor , acetylene black AB, and binder, polyvinylidene fluoride PVdF, dissolved in 1-methyl-2-pyrrolidinone NMP AM mass is 1 mg cm −2. Beaker-type two-electrode cells were used for all charge-discharge experiments which were carried out at 25°C on a Hokuto Denko charge-discharge tester. All cells were assembled in an Ar-filled glove box using 1 M LiClO 4 in ethylene carbonate/ diethyl carbonate EC/DEC, 1:1 by volume Tomiyama Pure Chem. Ind., Ltd. as the electrolyte except for the compatibility test with propylene carbonate PC based electrolyte in which 80% PC with 10% each EC/DEC by volume were used. Li/C and Li/C Zr half-cells were galvanostatically charge-discharge cycled between 2.5 and 0.01 V vs Li/Li +. LiCo 0.2 Mn 1.8 O 4 was prepared by solid-state reaction 10 using Li 2 CO 3 , CoCO 2 2 · 2H 2 O, and Mn 2 O 3 and deposited on an Al foil using slurry of 70% AM, 20% AB, and 10% PVdF in NMP AM mass is 2-5 mg cm −2. The Li/LiCo 0.2 Mn 1.8 O 4 half-cell was cycled between 4.5 and 3.5 V vs Li/Li +. Full cells were assembled and cycled as follows. At first, the ratio of cathode/anode r that gives optimum performance was determined by charge-discharge cycling of cells based on C or C Zr as anode and LiCo 0.2 Mn 1.8 O 4 as cathode at various weight ratios. The geometrical surface area of the anode and cathode was best kept constant by using an appropriate thickness of the cathode film. The observed optimum " r " is 3.3 and 3.4 by wt for cells based on C and C Zr , respectively. The optimum charge-discharge voltage range of the full cell determined similarly by cycling the cell at different voltage ranges is 4.2-3.3 V vs Li/Li +. Precycled cells were prepared as follows. The initial two cycles of C and C Zr electrodes, assembled as half-cells Li/C and Li/C Zr , were charge-discharge cycled between 2.5 and 0.01 V vs Li/Li + at 0.2 C rate and subsequently assembled into the full cell C or C Zr /electrolyte/LiCo 0.2 Mn 1.8 O 4. X-ray diffraction XRD and X-ray absorption near edge structure XANES spectra revealed the formation of monoclinic structure of ZrO 2 on the surface of graphite 8 and the synthesized LiMn 1.8 Co 0.2 O 4 is single phase with cubic symmetry and space group Fd3 ¯ m. The lattice parameter is 8.203 Å and is consistent with a previous study. 10 The phase identification and the evaluation of the lattice parameter of LiMn 1.8 Co 0.2 O 4 were carried out using a Rigaku RINT 2500 X-ray diffractometer with Cu K radiation. Impedance measurements were taken at room temperature in a three-electrode cell using a Solartron 1255 B frequency response analyzer with an SI 1287 electrochemical interface in the frequency range 1 MHz to 10 mHz at ac voltage of 3 mV. Lithium metal was used as the
The complex electrochemistry of graphite electrodes in lithium-ion batteries
Journal of Power Sources, 2001
This paper discusses the interrelated phenomena of solid electrolyte interphase (SEI) formation and the irreversible charge consumption which occurs during the ®rst cycle of a graphite electrode, as well as their relevance to the cycling stability of lithium-ion batteries. Thus, results from relevant characterization methods, namely, in situ mass spectrometry, in situ infrared spectroscopy, in situ Raman and video microscopy, in situ scanning probe microscopy, in situ quartz crystal microbalance, and differential scanning calorimetry were combined for a more thorough understanding of observations made in cycling experiments. From electrochemical cycling tests, we have learned that a high speci®c charge ($360 Ah/kg of carbon), satisfactory cycle life of the graphite electrodes (1000 deep cycles), and an irreversible charge of <7% during SEI formation can only be obtained when water contamination of the cell is avoided. Under such conditions, a good-quality SEI ®lm is formed on the carbon surface. We conclude that during SEI ®lm formation, at ®rst the carbonate solvent(s) are reduced, forming ethylene gas, organic radicals, oligomers, and polymers. Then a SEI ®lm is precipitated on the surface via a nucleation and growth mechanism. The irreversible charge consumption due to SEI formation is proportional to the BET speci®c surface area of the graphite and rapidly increases with increasing water content in the cell. #
Journal of Power Sources, 2003
The effect of electrode thickness and density for unpressed and pressed natural graphite electrodes were studied using electrochemical characterization. Pressing the graphite electrode decreases the reversible capacity and the irreversible capacity loss during formation. As electrode density increased, the capacity retention at high rate increased until 0.9g/cm 3 , and then decreased. The cycle performances of the pressed graphite electrodes were more stable than the unpressed one. Pressing graphite electrode affected on its electrochemical characterization such as irreversible capacity loss, high rate cycling and cycle performance.
Journal of energy storage, 2018
The performance of graphite electrodes in various electrolytes containing ethylene carbonate (EC) and mixtures of EC and propylene carbonate (PC) was studied at temperatures between 0 and 40°C. Included in the study was also the addition of ethyl acetate (EA). Differential scanning calorimetry (DSC) was employed to investigate phase transitions at low temperature (down to −80°C) and decomposition at elevated temperatures. Capacity loss was compared for graphite electrodes cycled at varying temperatures between 0 and 40°C for these electrolytes. Based on the results, suitable electrolytes able to work in a wide temperature range could be identified. Addition of EA improved the low temperature properties of the electrolyte and the graphite electrode, but the electrodes failed upon cycling at +40°C. Addition of PC to a multi-component system, making the total amount of cyclic carbonates 40% (i.e. 20% EC and 20% PC), increased the liquid temperature range of the electrolyte. However, the addition of PC, led to very high initial irreversible capacity loss of the graphite electrode, and reduced the capacity considerably at 0°C, most likely related to a higher resistance of the solid electrolyte interphase. Thus, mixtures of EC and linear carbonates like dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) were found to perform best in this temperature range.