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![2: Comparaison des technologies de batteries rechargeables en fonction de densités d'´ energie volumique et spécifiques. Figure de la référence [1]](profile/Veerapandian-Ponnuchamy/publication/278828214/figure/fig21/AS:613448778010714@1523268994984/Comparaison-des-technologies-de-batteries-rechargeables-en-fonction-de-densites-d.png)
2: Comparaison des technologies de batteries rechargeables en fonction de densités d'´ energie volumique et spécifiques. Figure de la référence [1]
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Due to the increasing global energy demand, eco-friendly and sustainable green resources including solar, or wind energies must be developed, in order to replace fossil fuels. These sources of energy are unfortunately discontinuous, being correlated with weather conditions and their availability is therefore strongly fluctuating in time. As a conse...
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Citations
... Additionally, it was noted that electrolyte combinations containing additional linear carbonates, like DEC, displayed lower decomposition temperatures than electrolyte mixtures containing LiPF 6 as a conducting salt and DMC as a co-solvent (in conjunction with EC). Depending on the linear carbonate alkyl chain length, distinct intermolecular interactions and solvent reactivity were suggested as the causes of this early disintegration [38][39][40]. ...
... The final solvated ion structures are presented in Figure 2. The van der Waals surface model (or Connolly surface), was used to derive the minimum and maximum dimensions of the solvated ions. With regards to desolvation energies, there is a large variation of values reported in the literature for Li + /EC:DMC, ranging from +4 to −41.4 kJ mol −1 [55] to −121 kJ mol −1 [56], while it is known that the solvated PF 6 − ion in is easily desolvated in organic solvents. As the values derived from simulations in this study and presented in Table 1 are in the range of values presented in the literature, for consistency we shall use our values in Table 1 as input data in the simulations in Section 4.4. ...
Graphene electrodes are investigated for electrochemical double layer capacitors (EDLCs) with lithium ion electrolyte, the focus being the effect of the pore size distribution (PSD) of electrode with respect to the solvated and desolvated electrolyte ions. Two graphene electrode coatings are examined: a low specific surface area (SSA) xGNP-750 coating and a high SSA coating based on a-MWGO (activated microwave expanded graphene oxide). The study comprises an experimental and a computer modeling part. The experimental part includes fabrication, material characterization and electrochemical testing of an EDLC with xGNP-750 coating electrodes and electrolyte 1M LiPF6 in EC:DMC. The computational part includes simulations of the galvanostatic charge-discharge of each EDLC type, based on a continuum ion transport model taking into account the PSD of electrodes, as well as molecular modeling to determine the parameters of the solvated and desolvated electrolyte ions and their adsorption energies with each type of electrode pore surface material. Predictions, in agreement with the experimental data, yield a specific electrode capacitance of 110 F g−1 for xGNP-750 coating electrodes in electrolyte 1M LiPF6 in EC:DMC, which is three times higher than that of the high SSA a-MWGO coating electrodes in the same lithium ion electrolyte.
... A large variation exists in the desolvation energy values reported in the literature for Li + ion in EC/ DMC, ranging from +4 to −41.4 kJ mol −1 [22] to −121 kJ mol −1 [23]. It is generally known that the solvated PF 6 − ion is easily desolvated in organic solvents [8]. ...
The operation of a lithium-sulfur (Li-S) battery involves the transport of Li⁺ ions and soluble sulfides mostly in the form of solvated ions. Key challenges in the development of Li-S battery technology are the diffusion of Li⁺ in micropores filled with sulfur and eliminating the “shuttling” of polysulfides. Ion dimensions in solvated and desolvated forms are key parameters determining the diffusion coefficient and the rate of transport of such ions, while constrictivity effects due to the effect of pore size compared to ion size control both transport and filling of the pores. We present molecular simulations to determine the solvation parameters of electrolyte ions and sulfides S2²⁻, S4²⁻, S6²⁻, and S8²⁻ in two different electrolyte systems: LiTFSI in DOL/DME and LiPF6 in EC/DMC. The calculated parameters include the coordination number and the geometrically optimized model and dimensions, using the van der Waals surface approach, of the solvated and desolvated ions. The desolvation energy of the electrolyte ions is also calculated. Such data is useful for the modeling and design of the pore sizes of cathode host materials to be able to accommodate the different sulfides while minimizing their “shuttling” between cathode and anode.
... The solvation shell of lithium cation has been extensively studied to better understand the interplay between the electrolyte's structure and the performances within lithium-ion batteries [26][27][28][29][30] . Nontheless, Ponnuchamy et al. on the basis of molecular dynamic calculations showed that the hexafluorophosphate anions contribute to the first solvation shell of lithium cation forming a Li + (EC) 2 (PF 6 − ) complex in the case of EC/DMC binary systems 30 . ...
... The solvation shell of lithium cation has been extensively studied to better understand the interplay between the electrolyte's structure and the performances within lithium-ion batteries [26][27][28][29][30] . Nontheless, Ponnuchamy et al. on the basis of molecular dynamic calculations showed that the hexafluorophosphate anions contribute to the first solvation shell of lithium cation forming a Li + (EC) 2 (PF 6 − ) complex in the case of EC/DMC binary systems 30 . The affinity of PF 6 − with respect to cyclic carbonates stems from hydrogen bonding owing to the high electronegativity of the fluorinated anion 31 . ...
Combining energy conversion and storage at a device and/or at a molecular level constitutes a new research field raising interest. This work aims at investigating how prolonged standard light exposure (A.M. 1.5G) interacts with conventional batteries electrolyte, commonly used in the photo-assisted or photo-rechargeable batteries, based on 1 mol.L⁻¹ LiPF6 EC/DMC electrolyte. We demonstrate the intrinsic chemical robustness of this class of electrolyte in absence of any photo-electrodes. However, based on different steady-state and time-resolved spectroscopic techniques, it is for the first time highlighted that the solvation of lithium and hexafluorophosphate ions by the carbonates are modified by light exposure leading to absorbance and ionic conductivity modifications without detrimental effects onto the electrochemical properties.
Developing high specific energy Lithium-ion (Li-ion) batteries is of vital importance to boost the production of efficient electric vehicles able to meet the customers’ expectation related to the electric range of the vehicle. One possible pathway to high specific energy is to increase the operating voltage of the Li-ion cell. Cathode materials enabling operation above 4.2 V are available. The stability of the positive electrode-electrolyte interface is still the main bottleneck to develop high voltage cells.
Moreover, important research efforts are devoted to the substitution of graphite anodes with Li metal: this would improve the energy density of the cell dramatically. The use of metallic lithium is prevented by the dendrite growth during charge, with consequent safety problems. To suppress the formation of dendrites solid-state electrolytes are considered the most promising approach.
For these reasons the present review summarizes the most recent research efforts in the field of high voltage solid-state electrolytes for high energy density Li-ion cells.
We present an automated method to clarify reaction pathways for complex reactive systems. The method uses accelerated molecular dynamics to find rare events and network graph analysis tools to map dynamic changes of species onto reaction networks. By the combined method, dominant pathways for complex reactions can be clarified without relying on experimental data and human intuition. To show the power of the method, it is applied to oxidation-induced decompositions of ethylene carbonates. A new energetically favorable decomposition pathway is obtained by the present scheme.
his paper focuses on of the use of implicit solvent in electrochemical density functional theory (DFT) calculations. We investigate both the necessity and limits of an implicit solvent polarizable continuum model (PCM). In order to recover the proper electrochemical behavior of the surface and in particular a proper potential scale, the solvent model is found mandatory: in the limit of a high dielectric constant, the surface capacitance becomes independent on the inter-slab space used in the model and therefore the electrochemical properties are only dominated by the interface structure. We show that the computed surface capacitance is not only dependent on the implicit solvent dielectric constant, but also on the solvent cavity parameter that should be precisely tuned. This model is then applied to the Li/electrolyte interface in order to check its ability to compute thermodynamic equilibrium properties. The use of a purely implicit solvent approach allows recovering a more reasonable equilibrium potential for the Li+/Li redox pair compared to vacuum approaches, but that it is still off by 1.5 V. Then, the inclusion of explicit solvent molecules improves the description of the solvent-Li+ chemical bond in the first solvation shell and allows recovering the experimental value within 100 mV. Finally, we show that the redox active center involves the first solvation shell of Li+, suggesting a particular pathway for the observed solvent dissociation in Li/Ion batteries.
