Generating structural distributions of atomistic models of Li2O nanoparticles using simulated crystallisation

Sayle, Thi X. T.; Ngoepe, Phuti E.; Sayle, Dean C.

doi:10.1039/c0jm01580f

Cited by 9 publications

(12 citation statements)

References 42 publications

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“…49,[85][86][87][88][89][90][91][92][93][94][95][96] Most of these works focused on developing and evaluating force field parameters for molecular dynamics simulations, which were then used to analyze structure, physical properties, and diffusion. [85][86][87][88][89][90][91][92][93][94] Experimentally, diffusion of Li + in Li 2 O was studied by Oishi et. al 95 using mass spectrometry and the 6 Li radioisotope as a tracer.…”

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confidence: 99%

Ion Diffusivity through the Solid Electrolyte Interphase in Lithium-Ion Batteries

Benitez

Seminario

2017

J. Electrochem. Soc.

126

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Understanding the transport properties of the solid electrolyte interphase (SEI) is a critical piece in the development of lithium ion batteries (LIB) with better performance. We studied the lithium ion diffusivity in the main components of the SEI found in LIB with silicon anodes and performed classical molecular dynamics (MD) simulations on lithium fluoride (LiF), lithium oxide (Li 2 O) and lithium carbonate (Li 2 CO 3 ) in order to provide insights and to calculate the diffusion coefficients of Li-ions at temperatures in the range of 250 K to 400 K, which is within the LIB operating temperature range. We find a slight increase in the diffusivity as the temperature increases and since diffusion is noticeable at high temperatures, Li-ion diffusion in the range of 1300 K to 1800 K was also studied and the diffusion mechanisms involved in each SEI compound were analyzed. We observed that the predominant mechanisms of Li-ion diffusion included vacancy assisted and knock-off diffusion in LiF, direct exchange in Li 2 O, and vacancy and knock-off in Li 2 CO 3 . Moreover, we also evaluated the effect of applied electric fields in the diffusion of Li-ions at room temperature. The continuous demand for smart phones, tablets and other mobile devices has enormously promoted the improvement of Li-ion batteries. Moreover, volatile oil prices, pollution and climate change concerns have further increased the need for energy storage devices for renewable energies and electric vehicles. The latter applications require batteries with even higher energy density, better cycle life, better power performance, lower cost and improved safety.1 Therefore, improving and increasing the fundamental scientific knowledge of lithium ion batteries is essential for their continual advancement.A key component in lithium ion batteries is the solid electrolyte interphase (SEI) film. The SEI film is a thin passivating layer that is initially formed, on both anode and cathode surfaces, from the reduction of the electrolyte during the first charging/discharging cycles. [2][3][4][5][6][7][8][9] It consists of a mixture of inorganic and organic products, such as LiF, Li 2 O and LiCO 3 , and (CH 2 OCO 2 Li) 2 , ROCO 2 Li and ROLi, where R is an organic group such as CH 2 , CH 3 , CH 2 CH 2 , CH 2 CH 3 , CH 2 CH 2 CH 3 that depends on the electrolyte solvent.10-24 Proposed structure models suggest that a dense layer of inorganic products is found near the electrode (inner layer) followed by a porous organic layer near the electrolyte/SEI interface (outer layer). [19][20][21] In carbon anodes, the SEI layer prevents further decomposition of the electrolyte by hindering electron transport from the electrode to the electrolyte, and by blocking the travel of solvent molecules to the active surface of the anode, where they can react with lithium ions and electrons. 25 In silicon anodes, i.e., the huge volume expansion of the anode creates cracks in the SEI layer and generates new surfaces which are freshly exposed to the electrolyte. 26 In both carbon and si...

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confidence: 99%

Ion Diffusivity through the Solid Electrolyte Interphase in Lithium-Ion Batteries

Benitez

Seminario

2017

J. Electrochem. Soc.

126

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“…19 This can be explained if the crystalline seed spontaneously evolves as a liquid enabling MD simulation to adequately explore the potential hypersurface and spontaneously evolve a crystalline seed because the energy barriers for ion mobility in a liquid are normally much lower than for a solid. In particular, simulated crystallisation, using MD, has been used to 'observe' the crystallisation of water, 11 Li 2 O( in ve rs ef lu ori te) , 20 TiO 2 (rutile), 21 ZnS (wurtzite), 19 MgO (rocksalt) 19 and MnO 2 (pyrolucite) 22 via the spontaneous evolution of a crystalline seed. Accordingly, we propose that nucleation of the liquid-solid phase change, via 'liquid' crystal seeds, is a more general phenomenon, applicable to other materials spanning several structural classes.…”

Section: Discussionmentioning

confidence: 99%

Liquid crystal seed nucleates liquid–solid phase change in ceria nanoparticles

Sayle

2015

Phys. Chem. Chem. Phys.

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Molecular dynamics (MD) simulation was used to explore the liquid-solid (crystal) phase change of a ceria nanoparticle. The simulations reveal that the crystalline seed, which spontaneously evolves and nucleates crystallisation, is a liquid rather than a solid. Evidence supporting this concept includes: (a) only 3% of the total latent heat of solidification had been liberated after 25% of the nanoparticle had (visibly) crystallised. (b) Cerium ions, comprising the (liquid) crystal seed had the same mobility as cerium ions comprising the amorphous regions. (c) Cerium ion mobility only started to reduce (indicative of solidification) after 25% of the nanoparticle had crystallised. (d) Calculated radial distribution functions (RDF) revealed no long-range structure when 25% of the nanoparticle had (visibly) crystallised. We present evidence that the concept of a liquid crystal seed is more general phenomenon rather than applicable only to nanoceria.

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“…Several interatomic interaction potentials have been developed for lithium oxide (see, e.g., [22][23][24]). In the present study we used the potential developed by Fracchia et al [25] from ab initio calculations and successfully applied to the study of the superionic transition [25], as well as in a recent non-equilibrium molecular dynamics study of diffusion in Li2O above 873 K [10].…”

Section: Methodsmentioning

confidence: 99%