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Shi et al. Energy Mater 2023;3:300036 https://dx.doi.org/10.20517/energymater.2023.27 Page 5 of 14

Small-angle neutron scattering
Small-angle neutron scattering (SANS) measurements were performed on the small-angle diffractometer
KWS-1 operated by the Forschungszentrum Juelich at the Heinz Maier-Leibnitz Zentrum in
Garching/Munich to identify the phase structure of the polymer electrolytes. The selected wavelength was
0.45 nm, and the detector distances were 2 and 8 m, with the collimation being 8 m. The electrolyte
membranes containing PTFSI copolymers with various block lengths and PC contents were prepared with a
thickness of ~100 µm and diameter of 12 mm and were sealed in pouch bags (5 cm × 5 cm) under vacuum
in the dry room. An empty pouch bag and a pouch bag with 1 mL of PC of the same size were prepared as
references.

Electrochemical characterization
Symmetric LiǁLi cells were assembled to investigate the lithium electrode cycling behavior. 330 µm Li foils
(Rockwood Lithium) were used in combination with either 1M LiTFSI in PC comprised in a Whatman
GF/D glass fiber separator or with the PTFSI-10/5-70 membranes. A current density of 2 mA cm was
-2
applied and reversed every 30 min. Electrochemical impedance spectra were acquired on a VMP3
potentiostat (Biologic) to track the changes of the impedance of LiǁLi cells during the cycling process using a
10 mV amplitude. To characterize the morphology of the plating for high plating capacity, similar
-2
symmetrical cells were assembled, and a current of 1 mA cm was applied for 10 h. The cells were then
disassembled in a glovebox under argon with H O and O levels below 1 ppm, and the samples were
2
2
transferred to the scanning electron microscope (SEM) chamber (Zeiss Auriga) without air exposure using a
hermetical cell. SEM images of the plated lithium metal electrode were then acquired.

For the study of the Al current collector corrosion, cyclic voltammetry (CV) was performed on a VMP3
potentiostat (Biologic) with LiǁAl two-electrode coin cells between 3.0 and 5.0 V. The sweep rate was
-1
1 mV s . For the battery tests, LiNi Mn Co O (NMC ) electrodes were prepared by mixing NMC
0.33
0.33
2
111
111
0.33
(Toda), Super C65 (Inerys), PVdF (Solvay, Solef 5130), and PTFSI-10/5 in the ratio 8:1:0.75:0.25 by weight.
LiNi Mn Co O (NMC ) electrodes were prepared by mixing NMC (Rongbai), Super C65 (C-
0.2
2
0.2
622
622
0.6
NERGY), and PVdF (Solvay, 6020) with a weight ratio of 9.2:0.4:0.4. The mass loading of NMC was
~2.4 mg cm . The LiFePO (LFP) electrodes were prepared similarly to the NMC electrode with LFP: Super
-2
4
C65: PVDF: PTFSI-10/5= 8:1:0.75:0.25 by weight. The mass loading of LFP was ~1.41 mg cm . The cells
-2
were first cycled at 0.1 C for three cycles and then at different dis-/charge rates.
RESULTS AND DISCUSSION
Polymer electrolyte processing and characterization
More often than not, block copolymers designed for nano-phase separation require a careful selection of the
solvent for casting membranes with a well-defined phase separation upon solvent removal. We showed
previously, for a similar polymer with longer blocks and a higher fraction of "rigid phase" (PTFSI-15/15),
that the solvent used to cast the dry membrane affects the phase separation. Specifically, we found that
dimethyl sulfoxide (DMSO) allows for a sharp hydrophobic-ionic phase separation and a more regular
phase structure as compared with dimethylacetamide (DMAc). Nevertheless, in both cases, SANS
measurements unambiguously revealed a clear phase separation and a constant non-ionic domain size upon
ethylene carbonate (EC) uptake . The hydrophobic block, i.e., partially fluorinated copolymer, was
[25]
designed to be non-miscible with high dielectric constant solvents, such as EC and PC. However, solvent
casting, followed by the removal of a high boiling point solvent, such as DMSO or DMAc, and the dry
membrane swollen by the suitable solvent(s), is a lengthy and energy-consuming process, thus a priori too
costly for a future scale-up of such technology. Therefore, in the current study, we processed the electrolytes
using solely the eventually comprised liquid phase (i.e., PC) and the polymer powder. A mixing step at a
moderate temperature (70 °C) was followed by a pressing step in a laboratory-scale process mimicking the