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Boaretto et al. Energy Mater. 2025, 5, 500040 https://dx.doi.org/10.20517/energymater.2024.203 Page 3 of 24

several studies. To cite some examples, Zhang et al. reported improved performance using LiNO as co-salt
3
[42]
in trimethyl phosphate-based QSPEs . Wang et al. used LiNO as the main salt in a triethyl phosphate/
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fluoroethylene carbonate-based gel polymer electrolyte, formulation showing better performance than the
control electrolyte with LiPF . Jing et al. used N,N-dimethylacrylamide to increase the solubility of LiNO
[53]
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6
in carbonate-based crosslinked gel polymer electrolytes, showing improved cycling performance of
LiNi Mn Co Co ||Li cells containing LiNO as co-salt . Cui et al. used LiNO as an additive in
[46]
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0.2
0.2
3
3
0.6
poly(ethylene carbonate)-based polymer electrolytes to increase the stability of the SEI [47,54] . LiNO was also
3
[48]
used as a salt additive in low-concentration sulfolane/fluorobenzene-based electrolytes . In general, LiNO
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is recognized as a beneficial SEI-forming additive. However, little attention has been paid to its effect on the
electro-oxidative stability of electrolytes and the characteristics of the CEI.
Herein, we present the properties and performance of QSPEs supported on a microporous polyolefin
separator, composed of PVdF-HFP, EC and two salt mixtures, a binary salt mixture with LiFSI and LiBOB,
and a ternary salt mixture with additional LiNO . The attention is in particular on the role of LiNO , as the
3
3
salt combination LiFSI/LiBOB/LiNO has been rarely used in polymer electrolytes . As expected, LiNO
[54]
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3
greatly improved the Li plating-stripping performance. However, results also indicate a deleterious effect on
the oxidative stability of the electrolyte, the cathode charge transfer resistance, and the coulombic efficiency
during full cell cycling. This might be due to various factors, such as catalytic activity of LiNO towards
3
electrolyte oxidation, crossover of the LiNO decomposition products from the anode to the cathode, or the
3
interference with the formation of the LiBOB-borne CEI.
Besides, we show that supporting PVDF-HFP-based QSPEs on polyolefin microporous separators has a
significant beneficial effect on the resistance against dendrites growth, allowing Li||Li cells cycling for over
-2
1,000 h at a cycled capacity of 2 mAh cm and at room temperature. With this improvement, we could cycle
NMC-811|QSPE|Li monolayer pouch cells in a practical configuration, featuring a high cathode active
-2
material loading (ca. 2.5 mAh cm and 13 mg cm ) and a thin lithium metal anode (~20 µm thick). Overall,
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QSPEs with LiFSI/LiBOB mixture showed excellent performance in NMC-811||Li monolayer pouch cells, at
-1
-1
room temperature, with initial discharge capacity of 200 mAh g at C/20, 150 mAh g at 1C, and 80%
capacity retention after 100 cycles. Such cycling results in practical cell configuration indicate that
supported QSPEs represent a viable alternative electrolyte for HV-LMBs.
EXPERIMENTAL SECTION
Materials
PVdF-HFP (experimental copolymer grade) was provided by Arkema and dried under vacuum at 100 °C
before use. LiFSI (Foranext®) was provided by Arkema and used without further purification. LiBOB
(American Elements, 99.9%) and LiNO (Alfa Aesar, 99%) were dried under vacuum at 60 and 70 °C,
3
overnight, respectively. Methyl ethyl ketone (MEK, anhydrous, 99.5%, Thermo Scientific) and acetone
(anhydrous, 99.8%, max., 0.005% H O, Thermo Scientific) were used without further purification. PC (99%,
2
< 10 ppm H O, Sigma Aldrich) and EC (Battery grade, Fujifilm) were used without further purification.
2
Tetra(ethylene glycol)dimethyl ether (99%, Sigma Aldrich) was dried under vacuum at room temperature
and stored on molecular sieves. Spray-dried LiNi Mn Co O (NMC-811), used for the full cell tests in
0.1
2
0.8
0.1
coin cells, was kindly provided by Cerpotech. The NMC-811 used for the cycling tests in pouch cells was
purchased from Targray. Li sheets laminated on Cu (Li-Cu) were kindly provided by ABEE.
QSPEs preparation
Unsupported quasi-solid electrolytes (QSPEs) for the preliminary study were processed by solvent casting,
in an Ar glovebox, by dissolving the PVdF-HFP in acetone and then by adding a solution of lithium salt in a