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Mazzapioda et al. Energy Mater 2023;3:300019 https://dx.doi.org/10.20517/energymater.2023.03 Page 17 of 30

[134]
1 M LiCF SO -DOL/DME as well as LLZO-type 1 M LiTFSI-DOL/DME . Busche et al. examined the
3
3
chemical compatibility of NASICON-type LAGP and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) in
1,3-dioxolane and 1,2-dimethoxyethane (DOL/DME; 1:1 vol.) for Li|S batteries. They observed the
8
formation of a resistive solid-liquid electrolyte interphase (SLEI) between Li and QSSE, similar to the SEI
formed in conventional LE-based cells. The SLEI was composed of the degradation products of both the LE
and ISEs, which imparted an additional impedance to the system. Similar behaviour was observed with
other ISEs, such as LiPON and LATGP [Figure 6B] .
[135]

With respect to the QSSE based on LAGP and LiTFSI in DOL/DME, Wang et al. demonstrated that the
QSSE suppresses the polysulphide shuttling effect and improves the interface contact between the
electrolyte and Li. From XPS and energy dispersive spectrometer (EDS)/SEM measurements, it was
demonstrated that no side reaction between Li and polysulphides occurred. As a result, discharge specific
-1
capacities of 1,528 mAh g , 1,386 mAh g and 1,341 mAh g were achieved at C/20, C/5 and C/2 rates,
-1
-1
[136]
respectively, with good Coulombic efficiency .
Based on several preliminary studies, it was considered that the phenomenon of co-decomposition occurred
in all QSSEs, and the properties of the SLEI would be dependent on the electrolyte combinations. Despite
the added resistance, various studies demonstrated significant enhancement in the interfacial properties due
to the addition of LE.

Xu et al. studied the QSSE consisting of Ta-doped LLZO (Li La Zr Ta O ), displaying a Li ion
+
1.5
3
12
0.5
7
-4
conductivity of 6 × 10 S cm at room temperature, and a carbonate-based LE containing butyl lithium (n-
-1
BuLi), a superbase. This QSSE was employed in Li|LiFePO batteries displaying superior electrochemical
4
performance by virtue of a lower interfacial resistance resulting from the addition of a small amount of
[137]
n-BuLi [Figure 6C] . Specifically, they demonstrated that the ISE|LE interface resistance increased upon
cycling when no n-BuLi was added, which was most likely due to the formation of a Li-poor or poorly
conducting SLEI. In contrast, the addition of n-BuLi in the LE appears to suppress the interface side
reactions. Furthermore, n-BuLi lithiates the garnet/LE interface, forming a stable and Li conductive SLEI,
+
yielding a good capacity retention of QSSLMB. Alkyl lithium is a well-known anionic polymerisation
initiator. Thus, the addition of n-BuLi may promote the formation of linear oligomeric carbonates, and on
the anode side, it is reported that the polymerised products of carbonate stabilise the electrode surface .
[138]
Wang et al. reported the impressive electrochemical performance of the Li|LiFePO cell employing the
4
QSSE composed of a glass ceramic, Li Al Ti (PO ) (GC-LATP), coated with a small amount (2 μL) of
4 3
1.6
0.4
1.4
-1
LiPF in EC/DMC/DEC 1:1:1 in vol. The QSSLMB delivered a specific capacity of 125 mAh g at 1C and
6
98 mAh g at 4C. The performance was attributed to the formation of a stable SLEI on the ISE surface,
-1
which prevents the reduction of GC-LATP by Li metal, as revealed by EIS measurements [Figure 6D] .
[139]
Since QSSE is able to physically separate the anode and cathode, it is possible to apply different LE on each
electrode respectively. Nikodimos et al. designed reduction-resistant LE (RRLE) and oxidation-resistant LE
(ORLE) [Table 1] and applied them to the anode and cathode of Mg-doped LAGP
(Li Al Mg Ge (PO ) ), respectively . When the electrodes were treated with RRLE, the specific capacity
[140]
1.5
0.4
0.1
1.6
4 3
-1
of Li|LiNi Mn Co O cell was 145.3 mAh g with a capacity retention rate of 71.8% at the 300th cycle.
1/3
2
1/3
1/3
This performance can be ameliorated further by replacing RRLE on the anode with ORLE. In addition to
these materials, the performances of other QSSLMB systems are summarised in Table 1.