A review of Functional Separators for Lithium Metal Battery Applications

Figure 11. 
(
a
) Schematic of the poling process of the BTO-coated PE separator and the effect of 
polysulfide rejection. Reprinted with permission from [139]. Copyright (2016) WILEY-VCH. (
b
) 
Schematic configuration of the Li–S cells with a commercial separator (top) and mesoporous carbon-
coated separator (bottom). The cell configuration consists of, from left to right, a sulfur cathode, the 
corresponding separator, and a Li-metal anode. Reprinted with permission from [140]. Copyright 
(2015) WILEY-VCH. 
Figure 11.
(
a
) Schematic of the poling process of the BTO-coated PE separator and the e
ff
ect of polysulfide
rejection. Reprinted with permission from [
139
]. Copyright (2016) WILEY-VCH. (
b
) Schematic
configuration of the Li–S cells with a commercial separator (top) and mesoporous carbon-coated
separator (bottom). The cell configuration consists of, from left to right, a sulfur cathode, the
corresponding separator, and a Li-metal anode. Reprinted with permission from [
140
]. Copyright
(2015) WILEY-VCH.
Materials 
2020
, 
13
, x 
21 of 38 
corresponding separator, and a Li-metal anode. Reprinted with permission from [140]. Copyright 
(2015) WILEY-VCH. 
Cui group coated a 30-nm carbon nanoparticle and polyvinylidene mixture (9:1 in mass ratio) 
on one side of a PP separator. This separator enabled a large quantity of LiPS to be accommodated in 
the separator layer [26]. Therefore, a large quantity of LiPS could be located on the cathode side of 
the separator. During 500 cycles, the LSB exhibited an initial specific capacity of 1350 mAh g
−
1
at 0.5 
C and achieved stable cyclic performance with a decrease of 0.09% in every cycle. Giebeler group 
coated mesoporous carbon on a PP separator to trap LiPS to be placed in the cathode [140] (Figure 
11b). Goodenough group fabricated a rGO@sodium lignosulfonate (SL)/PP separator using a thin 
coating of rGO/SL on a standard PP separator [141] (Figure 12). They used the principle that a 
negatively charged separator effectively suppresses negatively charged LiPS ions. The SL, a 
byproduct of chemical industries, contains an abundant quantity of negatively charged sulfonic and 
dendritic groups; thus, it was used to inhibit the shuttle effects. The flexible characteristic of rGO 
successfully prevented SL from flaking off from PP. It functioned as a robust separator, which 
guaranteed fast ion transportation, and delayed the migration of LiPS.