A review of Functional Separators for Lithium Metal Battery Applications

2020
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13
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26 of 37
Materials 
2020
, 
13
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27 of 38 
Figure 17. 
(
a
) Illustration of the synthesis of the GPE. Reprinted with permission from [148]. 
Copyright (2017) John Wiley and Sons. (
b
) Step process for in situ polymerization of GPE. Reprinted 
with permission from [162]. Copyright (2018) John Wiley and Sons. (
c
) Schematics of the changes in 
the Li electrodes using a liquid electrolyte and 3D-GPE during the Li plating/stripping. Reprinted 
with permission from [148]. Copyright (2017) John Wiley and Sons. 
Similarly, Li and co-workers designed a novel dual-salt lithium 
bis(trifluoromethanesulfonyl)imide–lithium hexafluorophosphate (LiTFSI-LiPF
6
) GPE with a 3D 
cross-linked polymer network [162] (Figure 17b). The 3D cross-linked polymer network by 
poly(ethylene glycol) diacrylate (PEGDA) and ethoxylated trimethylolpropane triacrylate was 
formed using dual-salts. Accordingly, higher thermal stability and ion transference were obtained. 
The compact GPE solved contact problems by facilitating the uniform deposition of Li atoms and 
successfully restricted the growth of dendrites. Moreover, the linear chain motion of PEGDA 
increased ionic conduction. As a result, the measured ionic conductivity at 25 °C
was 5.6 × 10
−
4
S cm
−
1
, 
which was higher than that of single salt GPE, LiTFSI (1.6 × 10
−
4
S cm
−
1
) and LiPF
6
(1.2 × 10
−
4
S cm
−
1
). 
A remarkable method of converting liquid electrolytes to quasi-solid GPEs by
the addition of
commercial LiPF
6
exists. Guo and co-workers added LiPF
6
to simply transform traditional ether-
based 1,3-dioxolane and 1,2-dimethoxyethane to a quasi-solid GPE [163]. They reported various 
scenarios applying the specialized electrolyte to several different cathode materials. The quasi-solid