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Emergence of Conduction Channels in Lithium Silicate  [PDF]
H. Lammert,A. Heuer
Physics , 2004, DOI: 10.1103/PhysRevB.70.024204
Abstract: The existence of conduction channels in lithium silicate (Li_2O)(SiO_2) is investigated. Regions of the system where many different ions pass by form channels and are thus spatially correlated. For a closer analysis the properties of the individual ionic sites are elucidated. The mobility of ions in single sites is found to depend strongly on the number of bridging oxygens in the coordination shell. The channels are not reflected in the network structure as obtained from the distribution of the bridging oxygens. Spatial correlations similar to those found in the silicate also emerge from studying the dynamics of particles in a simple random lattice model. This supports the suggestion that the observed spatial correlations can be viewed in analogy to the emergence of percolation paths.
Geochemistry of silicate-rich rocks can curtail spreading of carbon dioxide in subsurface aquifers  [PDF]
Silvana S. S. Cardoso,Jeanne T. H. Andres
Physics , 2014, DOI: 10.1038/ncomms6743
Abstract: Pools of carbon dioxide are found in natural geological accumulations and in engineered storage in saline aquifers. It has been thought that once this CO2 dissolves in the formation water, making it denser, convection streams will transport it efficiently to depth, but this may not be so. Here, we assess theoretically and experimentally the impact of natural chemical reactions between the dissolved CO2 and the rock formation on the convection streams in the subsurface. We show that, while in carbonate rocks the streaming of dissolved carbon dioxide persists, the chemical interactions in silicate-rich rocks may curb this transport drastically and even inhibit it altogether. These results challenge our view of carbon sequestration and dissolution rates in the subsurface, suggesting that pooled carbon dioxide may remain in the shallower regions of the formation for hundreds to thousands of years. The deeper regions of the reservoir can remain virtually carbon free.
Crystal Growth and Nucleation in Glasses in the Lithium Silicate System  [PDF]
Galina A. Sycheva
Journal of Crystallization Process and Technology (JCPT) , 2016, DOI: 10.4236/jcpt.2016.64004
Abstract: The crystal growth and nucleation in glasses in the lithium silicate system have been investigated. Phase separation in ultimately homogenized glasses of the lithium silicate system xLi2O·(100 x)SiO2 (where x = 23.4, 26.0, 29.1, and 33.5 mol% Li2O) has been studied. The glasses of these compositions have been homogenized using the previously established special temperature-time conditions, which make it possible to provide a maximum dehydration and removal of bubbles from the glass melt. The parameters of nucleation and growth of phase separated in homogeneities and homogeneous crystal nucleation have been determined. The absolute values of the stationary nucleation rates Ist of lithium disilicate crystals in the 23.4Li2O·76.6SiO2, 26Li2O·74SiO2 and 29.1Li2O·70.9SiO2 glasses with the compositions lying in the metastable phase separation region have been compared with the corresponding rates Ist for the glass of the stoichiometric lithium disilicate composition 33.51Li2O·66.5SiO2. It has been found that the crystal growth rate has a tendency toward a monotonic increase with an increase in the temperature, whereas the dependences of the crystal growth rate on the time of low temperature heat treatment exhibit an oscillatory behavior with a monotonic decrease in the absolute value of oscillations. The character of crystallization in glasses with the compositions lying in the phase separation region of the Li2O-SiO2 system is compared with that in the glass of the stoichiometric lithium disilicate composition. The conclusion has been made that the phase separation weakly affects the nucleation parameters of the lithium disilicate and has a strong effect on the crystal growth.
Coupling of ion and network dynamics in lithium silicate glasses: a computer study  [PDF]
Magnus Kunow,Andreas Heuer
Physics , 2005, DOI: 10.1039/b501265a
Abstract: We present a detailed analysis of the ion hopping dynamics and the related nearby oxygen dynamics in a lithium meta silicate glass via molecular dynamics simulation. For this purpose we have developed numerical techniques to identify ion hops and to sample and average dynamic information of the particles involved. This leads to an instructive insight into the microscopic interplay of ions and network. It turns out that the cooperative dynamics of lithium and oxygen can be characterized as a sliding door mechanism. It is rationalized why the local network fluctuations are of utmost importance for the lithium dynamics.
Characterization of the complex ion dynamics in lithium silicate glasses via computer simulations  [PDF]
Andreas Heuer,Magnus Kunow,Michael Vogel,Radha D. Banhatti
Physics , 2002, DOI: 10.1039/b201121b
Abstract: We present results of molecular dynamics simulations on lithium metasilicate over a broad range of temperatures for which the silicate network is frozen in but the lithium ions can still be equilibrated. The lithium dynamics is studied via the analysis of different correlation functions. The activation energy for the lithium mobility agrees very well with experimental data. The correlation of the dynamics of adjacent ions is weak. At low temperatures the dynamics can be separated into local vibrational dynamics and hopping events between adjacent lithium sites. The derivative of the mean square displacement displays several characteristic time regimes. They can be directly mapped onto respective frequency regimes for the conductivity. In particular it is possible to identify time regimes dominated by localized dynamics and long-range dynamics, respectively. The question of time-temperature superposition is discussed for the mean square displacement and the incoherent scattering function.
Lithium ion storage between graphenes  [cached]
Chan Yue,Hill James
Nanoscale Research Letters , 2011,
Abstract: In this article, we investigate the storage of lithium ions between two parallel graphene sheets using the continuous approximation and the 6-12 Lennard-Jones potential. The continuous approximation assumes that the carbon atoms can be replaced by a uniform distribution across the surface of the graphene sheets so that the total interaction potential can be approximated by performing surface integrations. The number of ion layers determines the major storage characteristics of the battery, and our results show three distinct ionic configurations, namely single, double, and triple ion forming layers between graphenes. The number densities of lithium ions between the two graphenes are estimated from existing semi-empirical molecular orbital calculations, and the graphene sheets giving rise to the triple ion layers admit the largest storage capacity at all temperatures, followed by a marginal decrease of storage capacity for the case of double ion layers. These two configurations exceed the maximum theoretical storage capacity of graphite. Further, on taking into account the charge-discharge property, the double ion layers are the most preferable choice for enhanced lithium storage. Although the single ion layer provides the least charge storage, it turns out to be the most stable configuration at all temperatures. One application of the present study is for the design of future high energy density alkali batteries using graphene sheets as anodes for which an analytical formulation might greatly facilitate rapid computational results.
Progression of the silicate cathode materials used in lithium ion batteries
LiYing Bao,Wei Gao,YueFeng Su,Zhao Wang,Ning Li,Shi Chen,Feng Wu
Chinese Science Bulletin , 2013, DOI: 10.1007/s11434-012-5583-3
Abstract: Poly anionic silicate materials, which demonstrate a high theoretical capacity, high security, environmental friendliness and low-cost, are considered one of the most promising candidates for use as cathode materials in the next generation of lithium-ion batteries. This paper summarizes the structure and performance characteristics of these materials. The effects of different synthesis methods and calcination temperature on the properties of these materials are reviewed. Materials that demonstrate low conductivity, poor stability, cationic disorder or other drawbacks, and the use of various modification techniques, such as carbon-coating or compositing, elemental doping and combination with mesoporous materials, are evaluated as well. In addition, further research topics and the possibility of using these kinds of cathode materials in lithium-ion batteries are discussed.
液相法结合冷冻干燥技术制备Li4SiO4材料及其高温二氧化碳吸收性能
A Liquid Phase Method Combined with Freeze-Drying Technique to Lithium Silicate Materials and Their Carbon Dioxide Absorption Properties at High Temperatures
 [PDF]

童沂, 黄雪芹, 许春慧, 肖强, 钟依均, 朱伟东
Journal of Advances in Physical Chemistry (JAPC) , 2015, DOI: 10.12677/JAPC.2015.42010
Abstract:
选用LiOH?H2O、LiNO3、Li2CO3为锂源,硅溶胶为硅源,采用液相法结合冷冻干燥技术制备了Li4SiO4材料,采用热重分析(TGA)研究了Li4SiO4前躯体的失重行为,采用X射线粉末衍射仪(XRD)和扫描电子显微镜(SEM)对Li4SiO4材料的结构和形貌进行分析。在热重分析仪(TGA)上考察了制备材料的高温CO2吸收性能,发现以LiOH?H2O为锂源时,合成材料的吸收性能最好。考察了该材料在不同温度、不同CO2分压下的高温CO2吸收性能,结果表明,在吸收温度为550℃,CO2分压为0.25 bar时,样品在5 min时吸收量为24.1 wt%,10 min内即可达到吸收平衡,平衡吸收量为29.9 wt%。经过5次吸收-解吸后,吸收速率、吸收量都没有出现明显下降。
A liquid phase method combined with the freeze-drying technique was developed to synthesize Li4SiO4 materials using LiOH?H2O, LiNO3, Li2CO3 and silica sol as the lithium and silicon sources, respectively. The weight loss behaviors of the prepared Li4SiO4 precursors were investigated by the thermal gravimetric analysis (TGA). The structure and morphology of the prepared Li4SiO4 materials were characterized by XRD and SEM, respectively. The CO2 absorption properties of prepared Li4SiO4 were investigated by thermal gravimetric analysis (TGA). The results show that the Li4
Carbon dioxide in silicate melts: A molecular dynamics simulation study  [PDF]
B. Guillot,N. Sator
Physics , 2011, DOI: 10.1016/j.gca.2011.01.004
Abstract: The distribution, recycling and storage of carbon in the Earth are of fundamental importance to understand the global carbon cycle between the deep Earth and near surface reservoirs. Degassing of CO2 at mid-ocean ridges may give information on the source region but the very low solubility of CO2 in tholeitic basalts has for consequence that near all Mid-Ocean Ridge Basalts glasses exsolve their CO2 rich vapor at shallow depth as they approach the ocean floor. Hence their CO2 contents mostly represent the pressure at eruption and not the source region. Recent petrological investigations have shown that the presence of carbonates at depth in the upper mantle has a large effect on the solidus of carbonated silicates by inducing incipient melting at much lower temperature. So the role of carbon-rich melts at great depth is now becoming a credible scenario to explain the extraction of CO2 from the source region to the surface. During the last three decades many studies have been devoted to measure the solubility of CO2 in silicate melts of various composition. But due to experimental difficulties these studies were generally restricted to low and moderate pressures (below ~20 kbar). By performing a series of molecular dynamics simulation where a supercritical CO2 phase is in contact with a silicate melt of various composition (from felsic to ultrabasic) at different temperatures (1473-2273K) and pressures (20-150kbar), we have been able to evaluate the solubility of CO2, the population of molecular and carbonate species, their diffusivity through the melt and the local structure. We show that this kind of molecular simulation is a useful theoretical guide to better understand the behavior of CO2 in magmas at depth.
Feasibility of Lithium Storage on Graphene and Its Derivatives  [PDF]
Yuanyue Liu,Vasilii I. Artyukhov,Mingjie Liu,Avetik R. Harutyunyan,Boris I. Yakobson
Physics , 2013, DOI: 10.1021/jz400491b
Abstract: Nanomaterials are anticipated to be promising storage media, owing to their high surface-to-mass ratio. The high hydrogen capacity achieved by using graphene has reinforced this opinion and motivated investigations of the possibility to use it to store another important energy carrier - lithium (Li). While the first-principles computations show that the Li capacity of pristine graphene, limited by Li clustering and phase separation, is lower than that offered by Li intercalation in graphite, we explore the feasibility of modifying graphene for better Li storage. It is found that certain structural defects in graphene can bind Li stably, yet more efficacious approach is through substitution doping with boron (B). In particular, the layered C3B compound stands out as a promising Li storage medium. The monolayer C3B has a capacity of 714 mAh/g (as Li1.25C3B), and the capacity of stacked C3B is 857 mAh/g (as Li1.5C3B), which is about twice as large as graphite's 372 mAh/g (as LiC6). Our results help clarify the mechanism of Li storage in low-dimensional materials, and shed light on the rational design of nano-architectures for energy storage.
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