Kinetics Of De-intercalation Research Articles

Highly Stable Aqueous Zn‐Ion Batteries Achieved by Suppressing the Active Component Loss in Vanadium‐Based Cathode

AbstractAqueous zinc–ion batteries (AZIBs) hold significant promise for large‐scale energy storage due to their inherent safety and environmental benefits. However, their practical application is often limited by rapid capacity loss from the dissolution of active cathode materials. Here, an effective strategy is proposed to suppress the active component loss by doping high‐valence Sn4+ in V3O7·H2O (Sn–V3O7·H2O) cathode material to achieve highly stable AZIBs. An impressive capacity retention of 89.3% over 6000 cycles at 5.0 A g−1 and a high specific capacity of 408 mAh g−1 at 0.1 A g−1 are attained. The Sn4+ doping thermodynamically lowers the formation energy of Sn–V3O7·H2O and increases the dissolution energy of VO2+ ions, thereby reinforcing the structural stability and suppressing the vanadium dissolution. Besides, Sn4+ doping enhances electrical conductivity and broadens Zn2+ diffusion channels, significantly accelerating Zn2+ intercalation and deintercalation kinetics. The experimental results are integrated with mechanism analysis and density functional theory calculation to elucidate the dissolution dynamics of V‐based cathodes, and employ X‐ray absorption spectroscopy to reveal the local electronic structures and chemical valences of vanadium during charge/discharge processes, thereby providing comprehensive insights into high‐performance cathode materials for AZIBs.

Preparation of Ni–Zn dual-doped polyhedral LiMn2O4 for endurable cycling lithium ion batteries at high rate

Jahn-Teller distortion and manganese dissolution are always the dominant problem of attenuating long cyclic performance and rate capacity of spinel LiMn2O4 cathode materials. Herein, a Ni–Zn dual-doping strategy is proposed to synthesize various LiNi0.05ZnxMn1.95-xO4 (x = 0–0.05) materials via a solid phase combustion method. All the as-prepared Ni–Zn co-doping materials have a good spinel structure with Fd3m space group and present unique polyhedron morphology with exposed (111) facets, which is conductive to relieving the manganese dissolution and Jahn-Teller effect. Moreover, the Ni–Zn co-doping gives rise to the extended Li–O bond and increased cell volume, hence boosting the favorable intercalation and deintercalation kinetics of Li+ ions. Consequently, the optimized LiNi0·05Zn0·02Mn1·93O4 cathode exhibits good electrochemical performance with the initial discharge capacity of 127.30 mAh g−1 and capacity retention of 70% after 1000 cycles at 1 C. At 5 C, an ultra-long cycle stability with a capacity retention of 61% is obtained up to 1800 cycles. Even at the high current rates of 10 C and 20 C, the relatively high first discharge capacities of 106.50 mAh g−1 and 99.40 mAh g−1 are also delivered, respectively. The Ni–Zn co-doping polyhedral LiMn2O4 will provide a solution for developing high-performance cathode materials in lithium ion battery.

Applications of graphene-based composites in the anode of lithium-ion batteries

Limited by the disadvantages of low theoretical capacity, sluggish lithium ion deintercalation kinetics as well as inferior energy density, traditional graphite anode material has failed to meet the ever-increasing specific energy demand for lithium-ion battery technologies. Therefore, constructing high-efficiency and stable anodes is of great significance for the practical application of lithium-ion batteries. In response, graphene-based composite anodes have recently achieved much-enhanced electrochemical performance due to their unique two-dimensional cellular lattice structure, excellent electrical conductivity, high specific surface area and superior physicochemical stability. In this review, we start with the geometric and electronic properties of graphene, and then summarize the recent progresses of graphene preparation in terms of both methods and characteristics. Subsequently, we focus on the applications of various graphene based lithium-ion battery anodes and their inherent structure-activity relationships. Finally, the challenges and advisory guidelines for graphene composites are discussed. This review aims to provide a fresh perspective on structure optimization and performance modulation of graphene-based composites as lithium-ion battery anodes.

Carbon coated tetrakaidecahedron tin ferrite (SnFe2O4) with high pseudocapacitance as anode material for lithium-ion batteries

A series of carbon coated SnFe2O4 (SFO) with octahedron, decahedron and tetrakaidecahedron morphologies have been synthesized by a simple hydrothermal process using ferrocene as common source of iron and carbon, applying a cationic surfactant CTAB to modify the morphology. Compared with the octahedral SFO (no CTAB) and decahedral SFO-0.1 (with CTAB at the first critical micelle concentration (CMC)), the tetrakaidecahedral SFO-0.7 (with CTAB at the second CMC) as an anode of LIB shows a high charge/discharge capacity of 481.0/482.7 mAh g−1 after 1000 cycles at 2 A g−1,and 281.0/281.6 mAh g−1 after 2000 cycles at 6 A g−1. The investigations on Li-ions inter-/de-intercalation kinetics show that the main rate-controlled step of SFO-0.7 is pseudocapacitive behavior, with higher contribution of 95.88% at a scan rate of 2.0 mV s−1. The results suggest that the carbon layer obtained directly from ferrocene can effectively inhibit the volume expansion and structure damage of SnFe2O4. At the same time, more oxygen-vacancies increase the conductivity, the enhanced strength of the dominant (111) plane can adsorb Li-ions more easily, and the smaller SnFe2O4 can reduce the diffusion distance of Li-ions, all of which lead to a high and stable Li-ions storage capacity and rate capability.

Tunable Intracrystal Cavity in Tungsten Bronze‐Like Bimetallic Oxides for Electrochromic Energy Storage (Adv. Energy Mater. 5/2022)

Electrochromic Energy Storage In article number 2103106, Guofa Cai, Pooi See Lee and co-workers report that Nb18W16O93 nanomaterials with superstructure motifs show fast Li+ intercalation–deintercalation kinetics and robust stability for both electrochromic and rechargeable energy storage applications. A complementary smart window is further fabricated based on the Nb18W16O93 film, which can dynamically regulate the sunlight and solar radiant heat input of buildings while electrical energy can be stored in the smart window, providing a multifunctional system consisting of electrochromism, energy storage and an indicator.

Side-View Operando Optical Microscopy Analysis of a Graphite Anode to Study Its Kinetic Hysteresis.

Operando analyses have provided several breakthroughs in the construction of high-performance materials and devices, including energy storage systems. However, despite the advances in electrode engineering, the formidable issues of lithium intercalation and deintercalation kinetics cannot be investigated by using planar observations. This study concerns side-view operando observation by optical microscopy of a graphite anode based on its color changes during electrochemical lithiation. Since the graphite color varies according to the optical energy gap during lithiation and delithiation, this technique can be used to study the corresponding charge-discharge kinetics. In addition, the cell configuration uses liquid electrolytes similar to commercial cells, allowing practical application. Furthermore, this side-view observation has shown that microscale spatial variations in rate and composition control the insertion and deinsertion, revealing the kinetics throughout the whole electrode. The results of this study could enhance the fundamental understanding of the kinetics of battery materials.

A comparison of molecular structure and de-intercalation kinetics of kaolinite/quaternary ammonium salt and alkylamine intercalation compounds

It has great significance to research the effect of intercalated molecules with the same carbon chain and different functional groups on the properties of intercalation compounds since it can reveal the effect of different functional groups on the properties of intercalated compounds without considering the difference of carbon chains. In this study, the intercalation compounds of kaolinite/dodecyl trimethyl ammonium chloride (Kaol-DTAC) and kaolinite/dodecylamine (Kaol-DA) were studied by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetry and differential scanning calorimetry (TG-DSC) analysis, and Scanning electron microscope (SEM). Then the de-intercalation kinetics with different heating rates was investigated, and the optimized the mechanism function for de-intercalation process was calculated. The results showed that the basal spacings of Kaol-DTAC and Kaol-DA intercalation compounds are 3.56 and 4.08 nm, respectively. The DTAC molecules are arranged the Kaol surface in a single layer with an angle of 90° while the DA molecules are tilted towards the Kaol surface in bilayer and the inclination angle is 39.9°, which is due to the different structure between these two type molecules. The SEM showed that the ratio, nanoscrolls length to diameter, of Kaol-DA is larger than that of Kaol-DTAC, and for the yield of nanoscrolls, the former is greater than the latter. Moreover, by using KAS and Ozawa methods, the activation energy (E) of Kaol-DTAC and Kaol-DA were obtained and the average values are 102.44 kJ mol−1 and 130.80 kJ mol−1, respectively. Furthermore, The optimal mechanism function for the intercalation compounds of Kaol-DTAC and Kaol-DA are G(α) = -ln(1-α) and G(α) = [(1-α)(−1/3)−1]2, respectively.

Real-Time Monitoring of Cation Dissolution/Deintercalation Kinetics from Transition-Metal Oxides in Organic Environments

The future of high-voltage rechargeable batteries is closely tied to the fundamental understanding of the processes that lead to the potential-dependent degradation of electrode materials and organic electrolytes. To date, however, there have been no methods able to provide quantitative, in situ and in real timeinformation about the electrode dissolution kinetics and concomitant electrolyte decomposition during charge/discharge. We describe the development of such a method, which is of both fundamental and technological significance. Our novel approach enables simultaneous and independent measurements of transition-metal cation dissolution rates from different oxide hosts (Co3+/4+ or Cr3+/4+), deintercalation kinetics of working cations (Mg2+), and the relative rate of electrolyte decomposition.

Enhanced electrochromic properties of TiO2 nanocrystal embedded amorphous WO3 films

We investigated the effect of nanocrystalline TiO2 doping on the electrochromic properties of tungsten trioxide (WO3) films. Here, we prepared various TiO2 nanocrystal-embedded amorphous WO3 films by a simple one-step dip-coating method. XRD data of the films show amorphous nature for both undoped and nanoparticle TiO2 doped WO3 films with anatase phase of TiO2 having (101) plane, which were further confirmed by TEM measurements. XPS of TiO2 doped WO3 film shows +6 oxidation state of W atom, implying the stoichiometric WO3 composition. The electrochromic properties of the films were investigated by in situ spectroelectrochemical methods, showing the markedly different behaviors of the films depending on the amount of nanocrystalline TiO2 doped. In particular, charge deintercalation kinetics of the films were significantly affected by the content of nanocrystalline TiO2 in amorphous WO3 matrix with 7 times faster deintercalation process by 30 wt% of TiO2 doping into WO3 at the expense of the reduced bleaching transmittance. This phenomenon may be associated with the effect of nanocrystalline TiO2 particles on blocking accessibility of Li ions to the trapping sites which has to be de-trapped if the ions are to be released.

Hierarchical Li1.2Mn0.54Ni0.13Co0.13O2 hollow spherical as cathode material for Li-ion battery

Lithium-rich manganese-based layered materials have been considered as the most promising cathode materials for future high-energy-density lithium-ion batteries. However, a great loss of irreversible capacity at the initial cycle, poor cycle stability, and rate performance severely restrict its application. Herein, we develop a new strategy to synthesize hierarchical hollow Li1.2Mn0.54Ni0.13Co0.13O2 microspheres using sucrose and cetyltrimethylammonium bromide as a soft template combined with hydrothermal assisted homogeneous precipitation method. The hollow microspheres are assembled by the primary particles with the size of 50 nm. As a result, the as-prepared material exhibits high reversible capacity, good cycling stability, and excellent rate property. It delivers a high initial discharge capacity of 305.9 mAh g−1 at 28 mA g−1 with coulombic efficiency of 80%. Even at high current density of 560 mA g−1, the sample also shows a stable discharge capacity of 215 mAh g−1. The enhanced electrochemical properties are attributed to the stable hierarchical hollow sphere structure and the appropriate contact area between electrode and electrolyte, thus effectively improve the lithium-ion intercalation and deintercalation kinetics.

Tailoring Anisotropic Li-Ion Transport Tunnels on Orthogonally Arranged Li-Rich Layered Oxide Nanoplates Toward High-Performance Li-Ion Batteries.

High-performance Li-rich layered oxide (LRLO) cathode material is appealing for next-generation Li-ion batteries owing to its high specific capacity (>300 mAh g-1). Despite intense studies in the past decade, the low initial Coulombic efficiency and unsatisfactory cycling stability of LRLO still remain as great challenges for its practical applications. Here, we report a rational design of the orthogonally arranged {010}-oriented LRLO nanoplates with built-in anisotropic Li+ ion transport tunnels. Such a novel structure enables fast Li+ ion intercalation and deintercalation kinetics and enhances structural stability of LRLO. Theoretical calculations and experimental characterizations demonstrate the successful synthesis of target cathode material that delivers an initial discharge capacity as high as 303 mAh g-1 with an initial Coulombic efficiency of 93%. After 200 cycles at 1.0 C rate, an excellent capacity retention of 92% can be attained. Our method reported here opens a door to the development of high-performance Ni-Co-Mn-based cathode materials for high-energy density Li-ion batteries.

Electrochemical deintercalation kinetics of 0.5Li2MnO3·0.5LiNi1/3Mn1/3Co1/3O2 studied by EIS and PITT

The charge transfer resistances (Rct) and chemical diffusion coefficients of lithium ions (DLi+) in 0.5Li2MnO3·0.5LiNi1/3Mn1/3Co1/3O2 at various potentials in the first charge process were systematically tested by EIS and PITT. In the initial stage of the charging process, Rct gradually decreased to a minimum value of 68.5 Ω at 4.0 V. Then it sharply increased to 977.5 Ω at 4.8 V. The main reason was the activation of Li2MnO3 component started to decompose to Li2O and MnO2 at about 4.5 V. The DLi+ obtained from EIS and PITT was greatly dependent on the potential and it in the range of 10−16 to 10−12 cm2 s−1and 10−14 to 10−13 cm2 s−1, respectively. The DLi+ variation tendency with cell potential obtained from EIS and PITT was consistent with each other and with a maximum value at 4.0 V. The low Li+ diffusion coefficients was due to the high kinetic barrier associated with oxygen loss, surface and structural rearrangement. The results showed that the kinetic of 0.5Li2MnO3·0.5LiNi1/3Mn1/3Co1/3O2 was controlled by lithium-ion diffusion in the low voltage (<4.0 V) and controlled by charge transfer resistance in the high voltage (>4.3 V).

Determination of Physico-Chemical Parameters for Simulation of Lithium Ion Batteries

For understanding of existing battery systems such as lithium-ion batteries and for the development of future battery systems, advanced numerical simulation tools are important. One beneficial aspect of computational methods is that they can provide insight into physical and chemical aspects, which sometimes cannot be probed by experimental methods. Accuracy and reliability are key issues for such numerical simulations and depend on appropriate physical models, boundary conditions, and accurately determined physico-chemical parameters1. For numerical simulations of battery systems, the ion-transport model for concentrated electrolyte solutions introduced by Newman and Thomas-Alyea is frequently used and depends on three ion transport parameters, namely the conductivity, the transference number and the binary diffusion coefficient. In addition to the transport parameters, the thermodynamic factor which is derived from the mean molar activity coefficient is required for the correct description of the thermodynamic behavior of a binary electrolyte solution. Since the microscopic geometry of actually used porous electrodes and separators are largely unknown, a homogenization approach is applied for the macroscopic description of porous media. In this case, the influence of the microstructure on the macroscopic behavior is modelled by additional geometric parameters such as the porosity ε and the tortuosity τ. For an accurate description of the interface reactions the intercalation and deintercalation kinetics have to be known, often described by a Butler-Volmer behavior. Lastly solid state diffusion of lithium ions within the active materials may limit the battery performance, especially at high charge and discharge currents. A vast spectrum of physico-chemical parameters can be found in the literature (e.g., Valoen and Reimers2), but since the investigated electrolytes and the experimental techniques differ from study to study, it is difficult to find a consistent parameter set for a given electrolyte. In addition, some of the parameters are often fitted to match experimental performance data and may thus be fitting parameters rather than intrinsic physico-chemical parameters with predictive capability. We will present an overview of the necessary physico-chemical parameters for simulation of lithium ion battery performance and will show methods by which they can be measured rigorously. For example, novel methods will be shown with which one can determine transport, thermodynamic and geometrical properties like for instance the transference number, the thermodynamic factor and the separator and electrode tortuosity3-5. Figure 1 exemplarily shows one of those results, namely the determination of electrode tortuosities based on impedance spectroscopy measurements in symmetrical cells. Our concentration and temperature dependent studies of physico-chemical parameters as well as the methodology for their unambiguous deter-mination will allow for an improved correlation between lithium ion battery experiments and simulations. More importantly, the use of intrinsic physico-chemical paramters will enable predictive simulations rather than data fitting models, which helps in understanding as well as predicting present and future lithium ion battery technologies. Figure 1: Comparison of determined tortuosities for different electrodes at porosities between 30% and 35% and comparison with the tortuosity obtained by the commonly used Bruggeman estimate (τ=ε -0.5). Acknowledgements We gratefully acknowledge the funding by the Bavarian Ministry of Economic Affairs and Media, Energy, and Technology for its financial support under the auspices of the EEBatt project.

Thermal decomposition behavior and de-intercalation kinetics of kaolinite/quaternary ammonium salt complexes

Kaolinite/quaternary ammonium salt complexes were prepared by intercalation and displacement of kaolinite–N-methylformamide (Kaol–NMF) with methanol (Me) and quaternary ammonium salt. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetry and differential scanning calorimetry (TG–DSC) analysis. The d-values of the kaolinite/quaternary ammonium salts complexes increase with the alkyl chain length of the quaternary ammonium salts. Based on the results and the available evidence pointing toward the interlayer structure of kaolinite intercalation complexes, the most possible structural model for the kaolinite/quaternary ammonium salt intercalation complexes was proposed. For the kaolinite–dodecyl trimethyl ammonium chloride, kaolinite–trimethyl tetradecyl ammonium chloride and kaolinite–hexadecyltrimethylammonium chloride, the intercalation molecules are oriented perpendicular to the kaolinite surface in a single layer. However, for kaolinite–stearyl trimethyl ammonium chloride, the cationic head of intercalated stearyl trimethyl ammonium chloride molecules may be partially hydrated and arrayed aslant in the interlayer space of kaolinite with an inclination angle of 35°. Thermal analysis results revealed that the thermal decomposition of kaolinite/quaternary ammonium salt complexes occurs in two main steps. The function of the most probable mechanism, activation energy E and pre-exponential factor were obtained by mutual authentication using KAS and Ozawa methods, Satava integral method and Achar–Brindley–Sharp–Wendworth methods. The average activation energy E of four kaolinite/quaternary ammonium salt intercalation complexes is 108.147, 153.478, 125.723 and 88.008 kJ mol−1, respectively. The optimized mechanism function for de-intercalation process of quaternary ammonium salt is f(α) = 1 − α and G(α) = −ln(1 − α).

Influence of Dopant Concentration on the Electrochromic Properties of Tungsten Oxide Thin Films

In order to achieve neutral coloration suitable for smart window applications WO3 thin films modified by V2O5 doping were deposited using RF magnetron sputtering method with 100W RF power at room temperature (RT). The influence of dopant concentration on the structural and electrochromic performance have been investigated. Amorphous structure was revealed by the surface characteristics facilitates electrochromic process. Uniformly distributed channels between the aggregated grains provide shorter path ways to enhance coloration efficiency. PL emission presented higher photonic efficiency for 2% of V2O5 doped WO3 film. Reversible color change between transparent oxidized and deep blue colored reduced state depicted faster ion intercalation / deintercalation kinetics and faster switching responses with the bleaching time of 3.3s and coloration time of 4.1s. Better reversibility of 59.10 %, larger photopic contrast ratio of 2.29 and greater coloration efficiency of 66.75cm2C−1 at 630nm unveiled by 2% of V2O5 doping, makes the film promising for practical applications.

The Impact of Additives upon the Propensity of Lithium Plating at Low Temperatures in Mcmb-LiNiCoAlO2-Based Li-Ion Cells with Methyl Propionate-Based Electrolytes

For both aerospace and terrestrial applications, there is a strong desire to obtain Li-ion rechargeable cells that can operate over a wide temperature range. Generally through the use of improved electrolyte formulations, Li-ion cells have been demonstrated to operate down to the very low temperature (i.e., to -50oC) while still providing reasonable performance at the warmer temperatures (up to +60oC). For example, utilizing electrolytes containing ester co-solvents, with and without additives, we have demonstrated wide operating temperature range capability in a number of Li-ion systems, including LiNiCoO2 1,2,3 LiNiCoAlO2 4 , and LiNi1/3Co1/3Mn1/3O2 5 , and LiFePO4 6 . However, although excellent discharge power capability has been demonstrated at low temperatures with a number of these systems, the charge characteristics at low temperature are not ideal and undesirable lithium plating can occur, especially at high rates. It is well known that the deposition of metallic lithium can occur on the carbon anode under certain conditions, rather than the preferred intercalation of lithium. 7,8 This process can occur when the lithium intercalation kinetics are significantly slowed at low temperature and the lithium plating reaction becomes more facile, due to its favorable kinetics. In our previous studies 9,10 , we have shown there to be a strong influence of electrolyte type upon the susceptibility towards lithium plating. For example, we have observed that the use of particular electrolyte additives, such as vinylene carbonate (VC), can increase the propensity of lithium plating when charging at high rates at low temperatures. This increased likelihood of plating is due to retarded lithium intercalation kinetics at the anode due to resistive surface films, and, in the case of VC, improved de-intercalation kinetics at the cathode. In collaboration with Quallion, we have recently demonstrated improved wide operating temperature range performance of MCMB-LiNiCoAlO2-based prototype cells containing electrolytes with methyl propionate (MP) and ethyl butyrate (EB) 4 , and more recently with MP-based electrolytes with various additives. In summary, excellent performance was obtained with these cells at low temperature, with discharge rates of 5C at -40oC and 20C at -20oC being supporting with various MP-based formulations, significantly out-performing the baseline, all carbonate-based electrolyte. However, much of the initial evaluation involved charging at moderate rates and temperatures, with the intent of avoiding any lithium plating in the cell. In the continuation of this study, we have investigated the impact of the electrolyte type, and especially the influence of the electrolyte additives, upon the likelihood of lithium plating when charging at low temperatures. In particular, we have investigated the influence that MP-based electrolytes containing various electrolyte additives play upon the charging behavior at low temperatures. The electrolyte additives studied include mono-fluoroethylene carbonate (FEC), lithium oxalate, vinylene carbonate (VC), and lithium bis(oxalato) borate (LiBOB). To understand the impact of the electrolyte upon the electrode kinetics, studies were performed in three-electrode lithium-ion cells, consisting of MCMB carbon anode and LiNiCoAlO2cathodes (fabricated by Quallion, LLC),using various techniques, including EIS, Tafel, and linear micro-polarization. Some electrolyte formulations were also incorporated into prototype 0.30Ah cells for evaluation (manufactured by Quallion), consisting of a cell design optimized for biomedical applications. The charge characteristics of these cells were evaluated over a range of conditions, including different temperatures, charge rates, and charge voltages. In general, we have observed a negative influence of some of these additives, such as VC and LiBOB, upon the charge acceptance characteristics under certain conditions at low temperature. ACKNOWLEDGEMENT The work described here was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA) and supported by the NASA Engineering and Safety Center (NESC) and the DOE BATT-ABR program. 1. M. C. Smart, et.al., J. Electrochem. Soc., 157 (12), A1361-A1374 (2010). 2. M. C. Smart, et.al., J. Electrochem. Soc., 149 (4), A361-A370 (2002). 3. M. C. Smart, et.al., J. Electrochem. Soc., 159 (6), A739-A751 (2012). 4.M. C. Smart, B. V. Ratnakumar, M. R. Tomcsi, M. Nagata, V. Visco, and H. Tsukamoto, 2010 Power Sources Conference, June 16, 2010. 5. M. C. Smart, B. V. Ratankumar, and K. Amine, 218th Meeting of ECS, Las Vegas, Nevada, Oct. 13, 2010. 6. M. C. Smart, B.V. Ratnakumar, A. S. Gozdz, and S. Mani, 214th Meeting of ECS, Honolulu, HI, Oct. 12-17, 2008. 7. A. H. Whitehead, M. Perkins, and J. R. Owen, J. Electrochem., Soc., 144, L92 (1997). 8 J. Fan and S. Tan, J. Electrochem. Soc., 153, A1081 (2006). 9. M. C. Smart, et.al. , Proc. 16th Annual Battery Conference, Long Beach California, January 2002. 10. M. C. Smart and B. V. Ratnakumar, J. Electrochem. Soc., 158 (4), A379-A389 (2011).

Kinetics of Deintercalation of Potassium Acetate from Kaolinite — A Raman Spectroscopic Study

The kinetics of structural change of a highly ordered kaolinite intercalated with potassium acetate have been studied through both intercalation and deintercalation. Deintercalation of the intercalated kaolinite, brought about by washing for different time intervals was followed by both X-ray diffraction and Raman microscopy. X-ray diffraction shows the kaolinite to be highly ordered with a Hinckley index of 1.42 and intercalated to approximately 90%. X-ray diffraction also showed that the intercalated kaolinite was deintercalated by 80% in the first minute of washing. An additional Raman band, attributed to the inner surface hydroxyl groups, strongly hydrogen bound to the acetate, is observed at 3605 cm (super -1) for the potassium acetate intercalate with the concomitant loss of intensity in the bands at 3652, 3670, 3684 and 3693 cm (super -1) . Upon deintercalation, the intensity of the 3605 cm (super -1) band decreased as the 3695 cm (super -1) band increased. The Raman spectral changes brought about upon deintercalation mirrored the changes observed by X-ray diffraction. Deintercalation of kaolinite caused disordering of the kaolinite.

Kinetics of Deintercalation of Potassium Acetate from Kaolinite — A Raman Spectroscopic Study

Kinetics of Deintercalation of Potassium Acetate from Kaolinite — A Raman Spectroscopic Study

Time-Resolved X-ray Diffraction Study of the Staging Phase Transition in CuCl2-Intercalated Graphite

The staging phase transitions during deintercalation of CuCl2-intercalated graphite have been studied using real-time X-ray powder diffraction. The evolution of the diffraction pattern observed during the deintercalation revealed gradual changes in phase composition. A detailed profile analysis enabled a quantitative phase analysis and visualized the phase composition at any time during the reaction. Conclusions concerning the mechanism and kinetics of deintercalation are compared with theoretical results.