PDF Publication Title:
Text from PDF Page: 006
Molecules 2022, 27, 6949 6 of 17 considerably larger than that of EC but is even larger than that of DFEC and tri-FEC and only slightly smaller than that of tetra-FEC. To reflect the real-world solution environment, we compared the energy gaps of the six systems in the presence of Na-ion (Figure 2d), which revealed that the presence of Na-ion had distinct effects on the six systems. The Na- ion decreased the energy gap of EC and considerably increased the energy gaps of DFEC, tri-FEC, and tetra-FEC but had almost no effect on the energy gap of FEC. In the actual solution environment, the weakly fluorinated FEC did not exhibit a high ESW, whereas the ESW of DFEC and tri-FEC remained lower than that of the strongly fluorinated tetra-FEC. By contrast, tetra-FEC exhibited the widest ESW. Numerous studies have investigated EC and FEC synthesis and their applications in SIBs [43,44]. However, limited studies have reported the synthesis of tetra-FEC and its composition in electrolyte systems. Considering previous studies have investigated balanced and excellent performance of tetra-FEC in SIB systems, tetra-FEC is a highly promising solvent molecule that provides a novel approach for SIB electrolyte optimization strategies. A similar conclusion was verified in LIBs. Zhang [21] et al. confirmed the superiority of tetra-FEC applied to LIBs to produce a homogeneous, denser LiF-containing SEI, which renders tetra-FEC a high-performing SEI modifier. Thus, tetra-FEC is an optimal choice for electrolytes in both SIBs and LIBs. The calculated electrostatic potential mapping of the [Na+-Tetra-FEC] complex is shown in Supplementary Materials (Figure S1); its atom coordinates are also supplemented. 2.2. 1,2-Dimethoxylethane Fluorination DME, which stands for 1,2-dimethoxylethane, is a linear ether solvent molecule typi- cally used in SIB electrolytes. The ether-based solvent has a specialized solvated structure, and the electrolyte formed with Na-ion exhibits several characteristics. 1. Compared with carbonate ester solvents, sodium–ether complexes exhibit high LUMO, low solvation energy, and good stability in electrochemical reactions. 2. Compared with carbonate ester solvents, ether-based solvents exhibit high reductive stability, which can inhibit dissolution during discharge and form a thin SEI layer. SEI formation typically occurs during the first few charge/discharge cycles of the battery, with sodium salts decomposing preferentially into the inorganic components of the inner layer and ether solvents decomposing into the organic components of the outer layer. An appropriately designed electrolyte facilitates the formation of NaF during the decomposition process and effectively protects the SEI. 3. Ether solvents are more compatible with electrodes because of saturated bonds, which reduces the occurrence of side reactions and enhances cycling performance. Despite these advantages, ethers exhibit poor oxidative stability and using them in high-voltage battery systems is difficult. In this study, we applied -CF1, -CF2, and -CF3 to design fluorinated DME. For the consistency of results, as in EC, we considered the van der Waals force under the solvation effect, optimized the structure of the electrolyte system of DME, fluorinated DME with Na-ion, calculated the BNa-O bond length, and measured the distance between Na and F. Because multiple Na-ions or F atoms exist, we considered the smallest (Figure 3a). The results revealed that the Na-ions bond with O (bond lengths between 2.336 and 3.229 Å). Considering that the atomic radius of F is smaller than that of the Na atom, but the distance between Na and F (between 2.375 and 3.556 Å) is only slightly larger than the Na-O bond length, the Na-ion also bonds with the F atom in the fluorinated DME with some strength as well. In -CF1/-CF2 units only, the maximum number of F atoms can reach 4 (1 F–4 F), and the bond lengths of BNa-O and BNa-F are maximum at 2.594 and 2.911 Å, respectively. However, the bond length of the -CF1CF2- combination, which is composed of -CF1 and -CF2 units only is markedly smaller than that of -CF3, which is even larger than that of 4 F fluorinated -CF2CF2-. This phenomenon indicates that the bond length increase induced by the -CF3 group is considerably larger than those of the -CF1 and -CF2 units. The bond length change in the interval of 1 F–4 F can be described as a “unidirectional increase.” After onePDF Image | First-Principles-Based Optimized Design of Fluoride Electrolytes
PDF Search Title:
First-Principles-Based Optimized Design of Fluoride ElectrolytesOriginal File Name Searched:
molecules-27-06949.pdfDIY PDF Search: Google It | Yahoo | Bing
Salgenx Redox Flow Battery Technology: Salt water flow battery technology with low cost and great energy density that can be used for power storage and thermal storage. Let us de-risk your production using our license. Our aqueous flow battery is less cost than Tesla Megapack and available faster. Redox flow battery. No membrane needed like with Vanadium, or Bromine. Salgenx flow battery
CONTACT TEL: 608-238-6001 Email: greg@salgenx.com (Standard Web Page)