Next Generation Batteries: Realization of High Energy Density Rechargeable Batteries by Kiyoshi Kanamura

Author:Kiyoshi Kanamura
Language: eng
Format: epub
ISBN: 9789813366688
Publisher: Springer Singapore

Neutron total scattering with the 6/7Li isotopic substitution technique is quite powerful for the Li+ local structure analysis in solutions. This technique has been applied to the Li+ local structure in an equimolar mixture of LiTFSA and tetraglyme [14]. Figure 2 displays the proposed Li+ local structure model with the experiments. The Li+–O (tetraglyme) distances are spread such as 2.06, 2.09, 2.13, 1.93 and 2.24 Å in the proposed Li+ local structure model. The average distance of 2.05 Å except the longest one is significantly larger than values of 1.95–1.97 Å usually found in aqueous solutions. On the other hand, the distances are similar to the values for cyclic and acyclic carbonates (2.04–2.08 Å) and for the polyethyleneoxide solutions (2.07–2.1 Å). Clearly, the longest distance of 2.24 Å is significantly larger than the others. According to the MD simulations, on average one of the terminal oxygen atoms in the glyme molecules is not fully coordinated to the Li+, which is reasonably consistent with the rather longer 2.24 Å distance for the Li+–O proposed by the neutron total scattering experiments. Thus, the Li+ is not simultaneously coordinated by all five oxygen atoms of the tetraglyme molecule (deficient 5-coordination), but only to four of them (actual 4-coordination). The solvate cation is considerably distorted, which can be ascribed to the limited phase space of the ethyleneoxide chain and competition for the coordination sites from the TFSA anion. The coordination numbers are listed in Table 1 along with various methods.

Fig. 2Li+ local structure model proposed with neutron total scattering experiments

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