Surface molecular engineering to enable processing of sulfide solid electrolytes in humid ambient air

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Article https://doi.org/10.1038/s41467-024-55634-8
# Surface molecular engineering to enable processing of sulfide solid electrolytes in humid ambient air

Received: 9 August 2024

Accepted: 17 December 2024

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Mengchen Liu 1,7, Jessica J. Hong 1,7, Elias Sebti 2,3,7, Ke Zhou1,7, Shen Wang1,
Shijie Feng 4, Tyler Pennebaker 2,3, Zeyu Hui1, Qiushi Miao4, Ershuang Lu5,
Nimrod Harpak 1, Sicen Yu 4, Jianbin Zhou 1, Jeong Woo Oh6, Min-Sang Song6,
Jian Luo 1,4, Raphaële J. Clément 2,3 & Ping Liu 1,4

Sulfide solid-state electrolytes (SSEs) are promising candidates to realize all
solid-state batteries (ASSBs) due to their superior ionic conductivity and
excellent ductility. However, their hypersensitivity to moisture requires processing environments that are not compatible with today’s lithium-ion battery
manufacturing infrastructure. Herein, we present a reversible surface modification strategy that enables the processability of sulfide SSEs (e. g., Li6PS5Cl)
under humid ambient air. We demonstrate that a long chain alkyl thiol, 1undecanethiol, is chemically compatible with the electrolyte with negligible
impact on its ion conductivity. Importantly, the thiol modification extends the
amount of time that the sulfide SSE can be exposed to air with 33% relative
humidity (33% RH) with limited degradation of its structure while retaining a
conductivity of above 1 mS cm -1 for up to 2 days, a more than 100-fold
improvement in protection time over competing approaches. Experimental
and computational results reveal that the thiol group anchors to the SSE surface, while the hydrophobic hydrocarbon tail provides protection by repelling
water. The modified Li6PS5Cl SSE maintains its function after exposure to
ambient humidity when implemented in a Li0.5In | |LiNi0.8Co0.1Mn0.1O2 ASSB.
The proposed protection strategy based on surface molecular interactions
represents a major step forward towards cost-competitive and energy-efficient
sulfide SSE manufacturing for ASSB applications.

Owing to the safety concerns associated with the use of flammable
organic electrolytes in conventional lithium-ion batteries, all solidstate batteries (ASSB) comprising a nonflammable solid electrolyte
have garnered significant interest over the past decade 1–4 . Solid-state
electrolytes (SSEs) also hold promise for higher interfacial stability and
better mechanical properties to suppress Li dendrite penetration,

opening the door to the implementation of lithium metal anodes that
enables high cell energy densities 5–8 . Among SSE materials, sulfides
such as Li9.6P3S12, Li10GeP2S12, and Li9.54Si1.74P1.44S11.7Cl0.3 are particularly attractive due to their superionic conductivities (as high as
~10 -2 S cm -1 ) and deformability 9 . Sulfide SSEs also exhibit lower Young’s
modulus values than oxide glasses and ceramics, which is beneficial for

1Aiiso Yufeng Li Family Department of Chemical and Nano Engineering, University of California San Diego, La Jolla, USA. 2Materials Department, University of
California Santa Barbara, Santa Barbara, USA. 3 Materials Research Laboratory, University of California, Santa Barbara, USA. 4 Program of Materials Science,
University of California San Diego, La Jolla, USA. 5 Department of Chemistry, University of California, San Diego, La Jolla, USA. 6 LG Energy Solution, Ltd. LG
Science Park, Magokjungang 10-ro, Gangseo-gu, Seoul, Republic of South Korea. 7 These authors contributed equally: Mengchen Liu, Jessica J. Hong, Elias
Sebti, Ke Zhou. [e-mail: rclement@ucsb.edu; piliu@eng.ucsd.edu](mailto:rclement@ucsb.edu)

producing favorable interfacial contacts with electrode materials by
mechanical compression 10 .

An Achilles’ heel of sulfide-based SSEs is their extremely poor
stability in the presence of water 11,12 . Hydrolysis generates toxic H2S gas
together with catastrophic loss of ionic conductivity 13, requiring sulfide SSEs to be handled in an inert glove box atmosphere with
exceptionally low moisture levels (−80 °C dew point) in academic
studies 14 . In an industrial setting, a dry room with a dew point of <

−60 °C is necessary, which is significantly more costly than the current
infrastructure for lithium-ion battery manufacturing with a dew point
of ~ −40 °C 15 .

Recently, the degradation process of sulfide SSEs in the presence
of moisture, and the main factors for the decreased ionic conductivity,
have been investigated 16 . The propensity for the hydrolysis reactions
of lithium argyrodites, Li12-x-mM m+ S6-xXx (M = P, As, Si, Ge, Sn, X = Cl, Br),
depend on the cation M m+ and halogen components 17 . During the
hydrolysis process of Li6PS5Cl, H2O tends to attack the P − S bond,
thereby releasing H2S by forming a P-O bond and breaking up the PS43−

units that are crucial for high Li-ion conductivity 18 .

There aretwoessentialrequirements for any approach to improve
the moisture resistance of sulfide SSEs: (1) the protection mechanism
should not significantly alter the critical properties of the material, i.e.,
ionic conductivity and redox stability; and (2) the protection needs to
be effective for an extended period of time, on the order of hours to
days, rather than minutes, commensurate with the time needed for
electrolyte processing to manufacture ASSBs. In this regard, approaches based on composite formation or on modifying the composition
of the SSEs themselves have been considered. Adding metal oxides
(such as ZnO, Fe2O3, Bi2O3) into sulfide SSEs can suppress H2S generation through the formation of metal sulfides, but often at the
expense of the ionic conductivity 19 . Alternatively, sulfide SSEs can be
coated with another ionic conductor that is more resistant to moisture,
to form a core-shell structure 20–23 . Sulfide SSEs can also be stabilized
through substitution, either at the S or P site 24 . Partially substituting
S 2– by O 2– to form oxysulfide compounds has led to improved air stability and wider electrochemical stability window 25 . Guided by the
hard/soft acid base theory, substituting the P 5+ hard acid (small, nonpolarizable) with a As 5+, Cu + and Sb 5+ soft acid (large, polarizable) can

Fig. 1 | Schematic illustration of the protection strategy for Li6PS5Cl (LPSC) in
humid ambient air. While LPSC undergoes hydrolysis and suffers a ~ 4 orders of
magnitude reduction in ionic conductivity, a liquid coating of 1-undecanethiol

reduce the rate of hydrolysis as the soft acids bind tightly to the S 2- soft
base, resisting the attack of the O 2- hard base 26–28 . While the chemical
stability of the electrolyte itself may improve from these substitutions,
this is often at the expense of the interfacial stability against lithium
metal, which jeopardizes the overall effectiveness of the ASSB.
Recently, organic hydrophobic material has been shown to improve
sulfide electrolyte (Li7P2S8Br0.5I0.5, Li6PS5Cl) moisture stability by
adsorbing on the surface through Van der Waals interaction 29,30 .
Finally, regardless of the approach, reported water stability tests are
usually limited to minutes of exposure time to ambient humidity
conditions under 10% - 35% RH 20,29,31 .

Results
The choice of a long-chain alkyl thiol to protect Li6PS5Cl
In this work, we propose an alternative strategy to current surface
modifiers. We note that sulfide SSEs, along with virtually all reported
inorganic modifiers, are mostly hydrophilic. While they have different
abilities to resist chemical decomposition in the presence of water,
they fundamentally lack the ability to repel water. On the other hand,
previously reported hydrophobic organic modifier has weak Van der
Waals interaction with the electrolyte. Here, we introduce an amphiphilic molecule, 1-undecanethiol (UDSH), that can chemically adsorb
onto the Li6PS5Cl (LPSC) SSE surface (labeled as UDSH@LPSC) to form
a hydrophobic shield (Fig. 1). Long-chain alkane thiol is a classic
example for the formation of self-assembled monolayers (SAM) on a
variety of substrates 32 . They are ideally suited for the protection of
sulfide solid electrolytes. Sulfide SSEs are highly susceptible to
nucleophilic attacks from polar organic solvents (e.g., diethylene glycol dimethyl ether or propylene carbonate) 33,34 . Very few functional
groups that chemically interact with the surface of LPSC without
altering the crystal structure have been identified. Toluene, an unsaturated hydrocarbon, is thus the most common choice. Their interaction with the LPSC is limited to Van der Waals forces, and not polar
enough to enable chemisorption 35 . These findings highlight the need
to tailor the chemistry of the head group of the surface modifier to
enable both stabilization of and attachment to the sulfide SSE surface.
A thiol head group is an ideal choice. It cannot launch nucleophilic
attack on the P-S bond while offering the possibility of forming S-S

(UDSH) with some of it chemically adsorbed onto the LPSC surface protects the
material, which loses less than 10-fold in conductivity in 33% relative humidity (RH).
UDSH forms a hydrophobic shield around the LPSC particles.

Fig. 2 | Chemical compatibility between the UDSH surface modifier and LPSC.
a Computed adsorption energies of undecane (UDCH) and UDSH onto the surface
of LPSC. The six types of atoms are represented by colored spheres as follows: Li
(light green), P (light purple), S (yellow), Cl (bright green), C (light Orange), and H
(silver). b 1 H spin echo NMR spectra collected at 18.8 T on a pure solution of UDSH
and on UDSH@LPSC sample. 1 H resonances in the UDSH@LPSC spectrum, and
their corresponding positions in the molecule, are labeled a–f in the upper left

bonds with the surface of LPSC without altering its crystal structure
and its ion conduction property 29 . We note that a thiol ((trimethylsilyl)
ethanethiol) has been employed to enhance cathode/electrolyte
interface stability 36 . The hydrocarbon tail of UDSH is also essential: it
provides the needed hydrophobicity to mitigate access of water to the
electrolyte surface. It is rather fortuitus that the most common SAM
molecule happens to be the most suitable for sulfide protection
although the rationales are unrelated: thiol-based SAM was overwhelmingly applied to metal surface where the formation of the
S-metal strong chemisorption scheme is the main motivation. In contrast, their ability to form S-S bond with LPSC is crucial for their
application in our case.

In order to gain insights into the UDSH water repelling ability
upon prolonged air exposure, we examined the interaction of the
UDSH with humid air in the absence of LPSC. Supplementary Fig. 1
shows the 300−1900 cm -1 region of Raman spectra recorded on an
UDSH solution and upon exposure to air with 33% RH for up to 3 days,
to monitor changes in the C − S stretching frequency. UDSH maintains
the C − S bond peak at 639 cm -1, and there is no evidence for S-S bond
formation at 450-495 cm -1, which suggests that UDSH molecules retain
their structural integrity in ambient air 37 . 1 H Nuclear magnetic resonance (NMR) spectra, shown in Supplementary Fig. 2, were also collected on the same series of UDSH samples and exhibit six 1H
resonances that are assigned to the six 1 H local environments present
in the UDSH molecule 38 . With prolonged exposure, 1 H signals exhibit

corner. The positions of the 1 H resonances associated with the UDSH molecule in
the pure UDSH solution, and in the UDSH@LPSC sample, are indicated with a red
dashed line and with a black dashed line/asterisk, respectively. S 2p c and P 2p d XPS
spectra collected on LPSC and UDSH@LPSC. Cryo-TEM images of LPSC e and
UDSH@LPSC f, visualizing the modifying layer on the LPSC surface in UDSH@LPSC.
g Nyquist plots of LPSC and UDSH@LPSC pellets sandwiched between two titanium
rods. Source data are provided as a Source Data file.

constant isotropic shifts, no appearance of H2O peaks, and minimal
changes in signal intensities. This implies that the UDSH molecule’s
structure remains unchanged, and H2O diffusion within UDSH is
exceptionally slow.

The introduction of a small molecule into the system leads to
good retention of the ionic conductivity of the SSE, unlike previously
reported polymeric surface modifier 39 . The protection mechanism is
highly effective: the UDSH@LPSC maintains the ionic conductivity to
above 1 mS cm -1 for up to 2 days of exposure (33% RH). Even after 3 days
of exposure, UDSH@LPSC powder maintains its original color and
crystallinity, while the control material suffered catastrophic loss of
conductivity along with clear discoloration (Fig. 1).

Chemical compatibility between UDSH and LPSC
To probe the chemical interaction between the LPSC and the UDSH, we
first conducted density functional theory (DFT) calculations of the
adsorption energies of undecane (UDCH) (Supplementary Fig. 3b),
which does not contain the thiol head group, and UDSH (Supplementary Fig. 3c), which contains the thiol functional group, onto the
surface of LPSC (Supplementary Fig. 3a). Figure 2a demonstrates that
both organic compounds can adsorb onto the LPSC surface, but UDSH
exhibits a much higher propensity to adsorb onto the surface
(−3.821 eV) as compared to UDCH (−1.172 eV). Furthermore, UDSH can
indeed form S-S bonds with LPSC, in line with our expectations
regarding the significance of the thiol head group.

We then prepared UDSH modified LPSC (UDSH@LPSC) by mixing
desired amounts of the materials using a planetary centrifugal mixer
(Supplementary Fig. 4). This mixture was then subjected to vacuum
drying at 80 °C for 2 h to remove residual unbonded UDSH on LPSC
surface. The compatibility of UDSH with LPSC was evaluated by
monitoring potential changes in crystal structure and ionic conductivity of UDSH@LPSC. Rietveld refinement of an X-ray Diffraction
(XRD) pattern obtained on the UDSH@LPSC sample (Supplementary
Fig. 5) indicates that the argyrodite structure remains intact. 1 H spin
echo NMR spectra, shown in Fig. 2b, were collected on a pure UDSH
solution and on the UDSH@LPSC sample to investigate the nature of
the interactions between UDSH and the LPSC surface. Six 1 H resonances can be resolved in the spectrum obtained on the UDSH solution, that are assigned to the six 1 H local environments, labeled (a–f), in
UDSH molecule. This assignment is based on predicted 1 H shifts from
the ACD/HNMR Predictor software package 38, and from the observed
integrated signal intensities and expected 1H site multiplicities. In
UDSH@LPSC, all the UDSH resonances remain visible, but the (a) and
(b) resonances are shifted downfield (to more positive ppm frequencies). The (a) and (b) resonances correspond to 1 H nuclei bonded
to carbons one and two bonds away from the thiol end group,
respectively. In NMR, the isotropic shift of a nucleus depends on the
degree of shielding from the static magnetic field provided by the local
electron cloud and is therefore a sensitive probe of local structure
changes. Here, changes in the isotropic shifts of the (a) and (b) resonances suggest that the UDSH molecules bond to the LPSC surface at
the thiol end. The downfield shift of the (a) resonance (0.2 ppm) is
greater than that of the (b) resonance (0.08 ppm), in line with the
greater change in the electron cloud around the 1 H nucleus closest to
the thiol end. While the seeming disappearance of the (d) resonance
assigned to the thiol group 1 H in the UDSH@LPSC spectrum could
provide further evidence for thiol end attachment to the LPSC surface,
this signal overlaps with the (c) and (e) resonances, and the presence of
residual, free UDSH molecules in the UDSH@LPSC sample makes it
difficult to correlate changes in (d) signal intensity with attachment
chemistry. An upfield shift is observed forthe (f) resonance (0.08 ppm)
that corresponds to the UDSH methyl chain end. We tentatively attribute this slight upfield shift to weak Van der Waals interactions
between the methyl end of the UDSH molecules and the LPSC surface.
The broad 1H resonance observed between 0.5–1 ppm in the
UDSH@LPSC spectrum in Fig. 2b corresponds to protonated impurities in the LPSC SSE, as confirmed by the 1 H spectrum obtained on
pure LPSC and shown in Supplementary Fig. 6. We also find that subjecting the UDSH@LPSC sample to a vacuum drying procedure at
80 °C for 2 h do not completely remove UDSH, as indicated by the
UDSH signals remaining in the corresponding 1H NMR spectrum
(Supplementary Fig. 6), with signal integration suggesting about
4–5 wt% of UDSH in the sample. However, almost all the UDSH modifiers can be volatilized after an additional heat treatment at 300 °C if
desired (Supplementary Fig. 6). Further details on the quantification
procedure are provided in Supplementary Fig. 6, Supplementary
Note 1, and representative fits of the corresponding spectra are provided in Supplementary Fig. 7.

The bonding interaction between UDSH and LPSC is further
investigated using surface-sensitive X-ray photoelectron spectroscopy
(XPS) analysis, with results presented in Fig. 2c,d. LPSC and
UDSH@LPSC display a P-S bond from PS43- at 161.5 eV in the S 2p

spectrum, and at 131.9 eV in the P 2p spectrum 40 . For LPSC, the signals
for Li-S at 160 eV (Fig. 2c) and P-O at 133.5 eV (Fig. 2d) are attributed to
surface decomposition products such as Li2S and POxSy40. Within

UDSH@LPSC, the increased intensity of the S-H peak at 160 eV, which
overlaps with Li-S, alongside the concurrent decrease in the P-O peak
at 133.5 eV, suggest the creation of a thin UDSH film on the LPSC surface. The increased intensity of the S-S peak at 164.5 eV on the
UDSH@LPSC sample (Fig. 2c), can be attributed to bridging sulfur

atoms 41 . This provides additional evidence for the establishment of S-S
bonds between UDSH molecules and S atoms at the surface of LPSC.
The integrity of the P-S bond at 131.9 eV in Fig. 2d indicates the good
compatibility of UDSH and LPSC. These findings corroborate the
existence of S-S interaction between UDSH and LPSC, aligning well
with the DFT calculation and NMR results.

Cryogenic transmission electron microscopy (cryo-TEM) images
of pristine LPSC and UDSH@LPSC samples reveal the nanoscale distribution of crystalline and amorphous regions, as shown in Fig. 2e,f.
The presence of an UDSH layer on the surface of LPSC does not alter its
bulk crystal structure, as indicated by the similar lattice spacing measured on UDSH@LPSC (of 0.182 nm, Fig. 2f), as compared to that
measured on pristine LPSC (0.185 nm, Fig. 2e). This observation validates the compatibility of UDSH with LPSC. An amorphous layer of ~
3 nm in thickness is present at the surface of the LPSC particle in the
UDSH@LPSC sample, which we attribute to the UDSH adsorption. The
presence of UDSH on the LPSC is also corroborated by Energy Dispersive X-ray Spectrometry (EDXS) results which confirm a uniform
carbon-rich layer on the surface of LPSC (Supplementary Figs. 8,9,
Supplementary Table 1). The structure of self-assembled alkyl thiol
layers has been traditionally characterized by atomic force microscopy
(AFM) conducted on flat substrates 32 . That is not feasible on a powder
sample with rough surfaces. To circumvent this difficulty, we prepared
a thin film LPSC layer by spin coating from an anhydrous ethanol
solution followed by thermal annealing (Supplementary Fig. 10a,b).
XRD spectra in Supplementary Fig. 10c confirm the crystal structure to
be consistent with the argyrodite structure. Two thiols, UDSH and
HDSH (hexadecane thiol, C16H33SH), were adsorbed onto the LPSC film
surface. AFM images show the formation of SAM-type layers for UDSH,
while the HDSH layer appears to be far more disorganized with the
hydrocarbon chain lying parallel to the substrates (Supplementary
Figs. 11,12). These observations indicate that UDSH is a preferred
protection agent than those with longer chains by forming a higher
quality surface coating. As will be shown later, the chain length has a
significant effect on their efficacy as protection agents.

The combined bulk and grain boundary resistance of
UDSH@LPSC exhibits a slight increase (Fig. 2g) as compared to
pristine LPSC. This modest increase can be attributed to the presence
of 4–5 wt% of UDSH adsorbent that remains after the 80 °C drying
procedure. Li-ion conductivities are 2.5 ± 0.05 mS cm -1 and 2.1 ± 0.2
mS cm -1, respectively, based on the average of 3 independent measurements (errors correspond to one standard deviation). The
modest effect of the UDSH surface modifier on the conductivity of
LPSC is highly unusual. For example, when subjecting sulfide SSEs to
other polar solvents, such as diethylene glycol dimethyl ether or
propylene carbonate, a two order of magnitude decrease in ionic
conductivity is typically observed due to nucleophilic attack from
electron donor from solvent molecules to the SSE species 33 . In the
case of propylene carbonate, the resulting mixture becomes sticky
and exhibits ionic conductivity too low to be measured 33 .

To examine the role of the UDSH molecule in influencing interfacial ion transport, we conducted 2D NMR using the exchange spectroscopy (EXSY) method which measures the Li ion exchange rate
between two different solid electrolytes (Supplementary Fig. 13). Here,
LPSC with or without the UDSH coating was mixed with Li2ZrCl6 (LZC).
The diagonal peaks represent lithium nuclei which remain in the same
environment during the given mixing time, while cross-peaks arise
from the signal of nuclei which have hopped between environments.
The cross-peak intensity ratio is 0.16 for pristine LPSC with LZC and
0.22 for UDSH@LPSC with LZC. The higher ratio in the UDSH@LPSC
means that more lithium is hopping between the LPSC and LZC during
the provided mixing time, thus proving that the UDSH coating does
not prevent diffusion between LPSC and other nearby environments.
More detailed analysis is provided in Supplementary Fig. 13, Supplementary Note 2.

Fig. 3 | Evaluation of LPSC and UDSH@LPSC upon exposure to humid
ambient air. a Ionic conductivity of LPSC and UDSH@LPSC as a function of air
exposure time. Data are presented as mean values ± SD. b A comparison of ionic
conductivity as a function of exposure time to humid air, highlighting the vastly
superior stability of UDSH@LPSC SSE for up to two orders of magnitude longer

Effectiveness of protection against moisture
The ultimate goal of this work is to drastically enhance the chemical
stability of LPSC by protecting it against hydrolysis. LPSC and
UDSH@LPSC were evaluated after exposure to humid ambient air
from 5 h and up to 3 days. The samples are labeled as “LPSC time air”,
e.g., LPSC 5H air refers to a sample that has been exposed for 5 h.

To evaluate the air stability of various LPSC samples in a quantitative manner and under specific humidity conditions, a humidifier
was used ensuring a consistent initial humidity of 33% RH. 600 mg
LPSC or a mixture of 600 mg LPSC and 120 mg UDSH, powder instead
of pellet, was placed inside the container. A thermo-hydrometer was
positioned near the sample to monitor changes in atmospheric
humidity levels over time. Supplementary Fig. 14a shows the evolution
of the relative humidity (RH) in the container as a function of exposure
time (t). After 72 h (3 days) of exposure, the relative humidity inside the
LPSC container decreases from 33% to 7%. In contrast, the relative
humidity within the UDSH@LPSC container decreases from 33% to
13%. The first derivative of the relative humidity with respect to time
provides an estimate of the rate of water uptake by the LPSC. The
results, shown in SupplementaryFig. 14b, reveal a significantly reduced
rate of water uptake for UDSH@LPSC, further confirming the effectiveness of the UDSH surface modifier at mitigating moisture reactivity. Concurrently, the production of H2S was also reduced by 5 times
after 3 days (Supplementary Fig. 15). LPSC showed continuous H2S
generation during exposure, while UDSH@LPSC exhibited a much
slower H2S generation rate. The generation of H2S should be closely
related to structural degradation and loss of conductivity, which
indicates that alkylthiol protections slows down both. The above air
exposed samples were subjected to a vacuum drying procedure at
80 °C for 2 h prior to following characterizations. We note that the
2-hour heat treatment at 80 °C has no discernible effect on conductivity (Supplementary Notes 3). The complete removal of UDSH by
a 3-hour heat treatment at 300 °C also indicates no degradation.
(Supplementary Figs. 16, 17)

The ionic conductivity of electrolyte pellets prepared by cold
pressing is plotted in Fig. 3a, based on the average of 3 independent

exposure times. Samples in references 2–8 were powders tested in closed systems,
similar to current work. Sample in reference 1 was a pellet tested in an open system.
c Ionic conductivity loss rate comparison. When normalized to the exposure
duration, the dramatic improvement offered by UDSH is also evident 20,29,31,42–46 .
Source data are provided as a Source Data file.

measurements (errors correspond to one standard deviation). When
UDSH absorbent is applied, the UDSH@LPSC ionic conductivity
slightly decreases from 2.5 ± 0.05 mS cm -1 to 2.1 ± 0.2 mS cm -1, as shown
in Fig. 3a. UDSH@LPSC exhibits excellent stability after air exposure,
based on the very small change of its ionic conductivity from 1.8 ± 0.10
mS cm -1 to 0.8 ± 0.27 mS cm -1 after 5 h to 3 days (Fig. 3a). In contrast,
LPSC without the UDSH coating experiences a significant drop in ionic
conductivity to 0.19 ± 0.003 mS cm -1 in 5 hours and to 8 × 10 −4 ± 4 × 10 −5

mS cm -1 after 3 days of air exposure (Fig. 3a). The rapid decrease in
ionic conductivity of LPSC within the first 5 h is consistent with the
findings in previous reports 20,40 .

The change in ionic conductivity of LPSC during exposure is a
function of both humidity and time. When the amount of LPSC powder
is reduced from 600 mg (Fig. 3a) to 200 mg (Supplementary Fig. 18),
thereby increasing the H2O to LPSC ratio, the relative effectiveness of
the UDSH protection becomes significantly more pronounced.
UDSH@LPSC exhibits an ionicconductivity of 0.4 ± 0.01 mS cm -1 that is
two orders of magnitude higher than LPSC (0.003 ± 1.5 × 10 -4 mS cm -1 )
after 1 day of air exposure. Further, we examined the moisture stability
of LPSC at UDSH:LPSC ratios of 1:5, 1:7, 1:9 and 1:24 with the results
shown in the Supplementary Fig. 19. The sample with a ratio of 1:24 is
prepared by vacuum drying when all remaining UDSH (4 wt%) is chemically adsorbed. In ambient air with an RH of 33%, the 1:24 sample
maintained an ionic conductivity of 1.0 mS cm -1 after 5 h, five times
higher than that observed for LPSC without UDSH protection. There is
indeed a correlation between UDSH:LPSC ratio and protection efficacy, with much longer protection for increased UDSH amount. This
indicates that both the surface SAM layer and the hydrophobic UDSH
liquid layer mitigate the diffusion of water to LPSC surface. The efficacy of the surface layer depends on its structure. On a rough particle
surface such as LPSC, it is difficult to form compact, defect free SAM
layers 32 . NMR results indicate that the hydrocarbon tail also has
interactions with the particle surface which is Van der Wall in nature.

To put our results in context, Fig. 3b-c summarizes previously
reported stability data collected on modified LPSC electrolytes after
air/moisture exposure 20,31,42–46 . UDSH protection extends the LPSC

Fig. 4 | Analysis of material degradation upon moisture exposure. a XRD patterns collected on LPSC and UDSH@LPSC exposed to humid air for up to 3 days.
b Ramanspectraof LPSC and UDSH@LPSC after 1 and 3 days ofhumid air exposure.

protection time from minutes to days (Fig. 3b). The conductivity loss
rate is in general ~ 3 orders of magnitude lower (Fig. 3c). Our approach
could enable sulfide SSE processing under standard atmospheric
conditions with no additional humidity controls, dramatically driving
down manufacturing costs. Needless to say, their stability in a standard
dry room with a dew point of −40 °C is fully expected. Moreover, we
have found that UDSH can dissolve the common binder for SSE,
hydrogenated nitrile butadiene rubber (HNBR), with a solubility of
10 wt% at room temperature (20 ± 2 °C) (Supplementary Fig. 20a,b).
UDSH can thus serve as both a processing solvent and a protection
agent, enabling processing of solid electrolyte films in less controlled
dry room environment (Supplementary Fig. 20c–f, Supplementary Note 4).

Structural evolution during air exposure
The progression of materials structural changes following exposure to
air (33%RH) was systematically examined. The XRD patterns in Fig. 4a
indicate that, following 1 day of exposure in 33% RH air, no new phases
are formed in the UDSH@LPSC sample, while new peaks at 25° and 35°
with very low intensities start to appear after 3 days of exposure. The

c–d XPS and e 31 P spin echo solid-state NMR spectra collected on LPSC and
UDSH@LPSC after 1 day or 3 days of air exposure. Source data are provided as
a Source Data file.

basic structure of LPSC remains unaltered, suggesting the effective
role of UDSH as a protective agent. On the contrary, the XRD pattern of
LPSC after being exposed for 3 days in 33% RH air exhibits major Li2S
and LiCl decomposition phases, indicated by the peaks at 25° and 35° 40 .
The complete XRD dataset is provided in Supplementary Fig. 21.

Raman spectroscopy was used to monitor the evolution of the
LPSC structure. Here, we monitor changes in the peak at 424.5 cm -1

(Fig. 4b), corresponding to PS43- units, a key structural component that

is responsible for the excellent ionic conduction of sulfide SSEs 47 . The
peak shifts to lower wavenumbers as the material degrades, which is
attributed to the decomposition of P-S bonds into P-O bonds, potentially forming oxy-thiophosphate species, although the exact speciation requires further investigation 47 . The spectrum obtained on the
UDSH@LPSC 1D air sample exhibits no change in the 424.5 cm -1 peak,
while the UDSH@LPSC 3D air sample shows a very small shift of the
same peak when 16.2% of PS43- unit is degraded. In contrast, the LPSC

(Fig. 4b), corresponding to PS4

same peak when 16.2% of PS43- unit is degraded. In contrast, the LPSC

1D air sample exhibits a substantial peak shift and signifies 41.8%
degradation of PS43- unit. These results agree with the XRD findings

degradation of PS43- unit. These results agree with the XRD findings

indicating that the bulk structure only starts to degrade at about 3 days
of humid air exposure for the UDSH@LPSC SSE.

Fig. 5 | Effect of functional group and chain length on LPSC protection upon
moisture exposure. a Ionic conductivity of LPSC, UDCH@LPSC and HECH@LPSC
as a function of time of exposure to humid air. b Ionic conductivity of LPSC,

The progression of materials changes was further monitored
using XPS and solid-state NMR (ssNMR), with results shown in
Fig. 4c–e. Upon examining the LPSC 1D air and LPSC 3D air samples,
S-O peaks from SOx2- at 167 eV appear (Fig. 4c) and the intensity of the

S-O peaks from SOx2- at 167 eV appear (Fig. 4c) and the intensity of the

P-O peak from oxysulfides (POxSy) increases at 132.5 eV (Fig. 4d),
indicating that hydrolysis has occurred, causing S 2- oxidation. Conversely, S-O peak is absent from UDSH@LPSC 1D air and UDSH@LPSC
3D air samples (Fig. 4c), and the intensity of P-O peaks remains
unchanged (Fig. 4d) when compared to the UDSH@LPSC (Fig. 2d). The
S-S bond intensities in UDSH@LPSC 1D and UDSH@LPSC 3D are
almost identical to UDSH@LPSC. We credit the bonding between
UDSH and LPSC for protecting the surface from oxidation, while the
hydrolysis reaction is significantly reduced so that the critical PS43

OCSH@LPSC, UDSH@LPSC, DOSH@LPSC, TESH@LPSC and HESH@LPSC as a
function of time of exposure to humid air. Data are presented as mean values ± SD.
Source data are provided as a Source Data file.

amount of UDSH adsorbed onto the LPSC surface decreases with air
exposure time (presumably due to evaporation), as indicated by a
decrease in the broad peak near (a) (~3.5 ppm) decreases, which could
partly explain the reduced efficiency of the UDSH coating with
increasing exposure time.

Discussion on the protection mechanisms
While we have established the effectiveness of UDSH in protecting
LPSC through the formation of a surface layer, its exact working
mechanism deserves further examination. In this regard, we first
investigated a variety of hydrophobic materials with different functional groups to see whether hydrophobicity itself is sufficient for
protection. The list includes petroleum wax (CnH2n+2, n = 20–40),
perfluoropolyether oil (PFPE, C50F102O16) (Supplementary Fig. 24),
undecane (UDCH) and hexadecane (HECH) (Fig. 5a). The weight ratio
of the hydrophobic material to LPSC is 1:5. LPSC protected by petroleum wax or PFPE oil suffered significant changes in crystal structure
after just one day of exposure in 33% RH humid air (Supplementary
Fig. 24a,b). As a control for UDSH, we also measured the air protection
effect of UDCH and HECH which do not have the thiol head group. The
ionic conductivity of UDCH or HECH coated LPSC dropped significantly from 1.8 to 0.7 mS cm -1 and 1.6 to 0.2 mS cm -1 after 1 day of
33%RH air exposure, respectively (Fig. 5a). 6 Li and 31 P spectra were also
collected on a series of samples modified with UDCH instead of UDSH
both before and after exposure to 33%RH air for one or three days.
Coating with UDCH (with a methyl rather than a thiol end group) does
not protect the LPSC SSE against hydrolysis, and significant changes
are observed in the 6 Li and 31 P resonances of the UDCH@LPSC 1D air
sample (Supplementary Figs. 25,26). The results shown in Supplementary Figs. 24,26 again indicate that the effectiveness of the UDSH is
not just the result of having the material being covered by excessive
amount of hydrophobic material. The presence of the thiol headgroup
is essential. Finally, we note that polar head group needs to be “oxygen” free to preserve conductivity. The mixing of undecanol with LPSC
(labeled as UDOH@LPSC) leads to > 4 magnitude of increase in LPSC
resistance even before air exposure as shown in Supplementary
Fig. 24c.

We also examined the role of hydrocarbon tail length since it is
known to affect the quality of the self assembled monolayer 32 . Octanethiol (labeld as OCSH, which has 8 -CH2-), undecanethiol (labeled as
UDSH, which has 11 -CH2-), dodecanethiol (labeled as DOSH, which has
12 -CH2-), tetradecanethiol (labeled as TESH, which has 14 -CH2-) and
hexadecanethiol (labeled as HESH, which has 16 -CH2-) are evaluted as
protection agent for LPSC (Fig. 5b). While all thiols show some benefits

units are effectively preserved.

LPSC and UDSH@LPSC samples were also investigated with 31 P
and 6 Li ssNMR before and after humid ambient air exposure, with
results shown in Fig. 4e and Supplementary Fig. 22, respectively.
Because ssNMR is element-specific, and sensitive to both crystalline
and amorphous phases, it can selectively probe 31 P and 6 Li nuclei within
the LPSC electrolyte. No clear differences are observed between the 31 P
spectra obtained on the LPSC and UDSH@ LPSC samples, signifying
that the LPSC bulk structure is unchanged upon mixing with UDSH.
The 31 P ssNMR spectrum collected on the UDSH@LPSC 1D air sample is
nearly identical to that obtained on LPSC, indicating that the coating
protects the LPSC structure from degradation. Even after 3 days in air,
most of the 31P spectral features attributed to pristine LPSC are
retained in the UDSH@LPSC sample. Nevertheless, the onset of
degradation is suggested by the appearance of new resonances at 82.9
and 88.7 ppm, as well as a third resonance at 86.8 ppm assigned to
isolated PS43– tetrahedra in β-Li3PS4-like environments48. Without any

isolated PS43– tetrahedra in β-Li3PS4-like environments48. Without any

protection, air exposure leads to significant degradation of the LPSC
bulk structure, reflected by the loss of the broad pristine LPSC resonance and the appearance of sharp resonances at 82.9 and 88.7 ppm,
assigned to POS33– tetrahedral units and isolated PS43– tetrahedra in

assigned to POS33– tetrahedral units and isolated PS43– tetrahedra in

Li3PS4-like environments, respectively 40,48 . Interestingly, air exposure
of the UDSH@LPSC samples appears to lead to the formation of more
Li3PS4-like isolated PS43– tetrahedra, as evidenced by the greater

Li3PS4-like isolated PS43– tetrahedra, as evidenced by the greater

intensity of the resonances at 86.8 ppm and 88.7 ppm in the spectrum
collected on the UDSH@LPSC 3D air sample relative to that obtained
on the LPSC 3D air sample. Overall, 31 P and 6 Li ssNMR results clearly
demonstrate that the UDSH modifying delays the onset of degradation
and largely preserves the LPSC structure after up to 3 days of exposure
to ambient air. Finally, 1H spectra collected on UDSH@LPSC and
UDSH@LPSC 1D air samples (Supplementary Fig. 23) suggest that the

when the liquid thiol thickness is consistent, UDSH offers the most
effective protection in terms of ionic conductivity, based on the
average of 2 independent measurements (errors correspond to one
standard deviation), likely due to the better quality of the surface
protection layer. As an example, the more effective protection of
UDSH@LPSC than HESH@LPSC after air exposure in Fig. 5b is consistent with the higher surface layer quality and more vertical chain
orientation of UDSH from AFM results (Supplementary Figs. 11,12) 32 .

The confirmed air stability of UDSH, and its ability to form S-S
bonds with the LPSC surface, make it a powerful, hydrophobic protecting agent. Specifically, UDSH forms a layer that impedes water
from reaching the LPSC surface. This protective layer prevents LPSC
from reacting with ambient moisture for up to several days. The slow
degradation of UDSH@LPSC upon extended air exposure likely
involves water penetration through defects that bypass the UDSH
protective layer, or through UDSH evaporation that leaves unbonded
LPSC surface exposed 49 .

Enhanced electrochemical performance
We next examine whether LPSC and UDSH@LPSC SSEs exposed to air
for 1 day can maintain their electrochemical stabilities in Li symmetric
and full cells. Li | |Li symmetric cells are commonly used to evaluate the
interfacial stability of SSEs with lithium metal. Critical current density
(CCD) is a metric to measure how well the SSE resists shorting due to
lithium dendrite growth 6 . Supplementary Fig. 27 shows that the CCD
value of UDSH@LPSC 1D air remains unchanged compared to pristine
LPSC, with a value of 0.6 mA cm -2, while the CCD value of LPSC 1D air
decreases from 0.6 to 0.3 mA cm -2 at room temperature (20 ± 2 °C).
Thus, in UDSH@LPSC 1D air, the surface modification along with the air
exposure do not appear to change the interactions between LPSC and
Li. Furthermore, Fig. 6 illustrates the galvanostatic cycling performance
of Li0.5In | |LiNi0.8Co0.1Mn0.1O2 with a capacity loading of 1.5 mAh cm -2 . As
compared to a base line cell using a pristine LPSC electrolyte (Supplementary Fig. 28), the cell fabricated with LPSC after 1 day of air exposure
(Fig. 6a-b) exhibits ~80 mV decreases in cell voltage as well as a lower
discharge capacity of 128 ± 15 mAh g -1 due to the increased electrolyte
resistance after the formation cycle. In contrast, the cell fabricated with

composite cell at 60 °C and at a 0.15 mA cm −2 . b, d 50 cycle capacity retention for
the cells shown in a and c, respectively. Source data are provided as a Source
Data file.

UDSH@LPSC after 1 day of air exposure (Fig. 6c-d) demonstrates similar
capacity of 152 ± 6 mAh g -1 and 82 ± 1.6% capacity retention even after 50
cycles as the pristine LPSC full cell (Supplementary Fig. 28), based on the
average of 2 independent measurements (errors correspond to one
standard deviation). This observation serves as strong evidence of the
remarkable protective effect of UDSH on LPSC, particularly in mitigating
the adverse effects of moisture exposure.

We have shown that a long chain thiol, 1-undecanethiol, can be
used to effectively protect the Li6PS5Cl solid electrolyte from humid air
exposure. 1-undecanethiol is found to be chemically compatible with
Li6PS5Cl, with negligible impact on its conductivity, and can be mostly
removed with a vacuum drying process. Structural analysis shows that
the -SH end group forms S-S bonds with S atoms at the surface of the
solid electrolyte without disrupting the P-S network, which is essential
for ion conductivity. The hydrocarbon tail of the thiol forms a hydrophobic layer that effectively repels water. The UDSH surface modification is found to be both effective at maintaining the bulk structure and
ionic conductivity of Li6PS5Cl, even upon extended exposure to humid
air. The UDSH-modified solid electrolyte maintains an ionic conductivity - 1 mS cm -1 for 2 days when exposed to air with a relative
humidity of 33%. These exceptional outcomes constitute a substantial
advancement in terms of moisture protection time, outperforming
prior work in this area by two orders of magnitude. With the
1-undecanethiol protection, the electrolyte shows comparable performance in solid state batteries even after 1 day of air exposure. While
practical implementation of using thiol requires scale up and cost
reduction, our results demonstrate their potential for preserving the
extremely air-sensitive sulfide solid electrolytes outside of a glovebox or
in a dry room. They can also serve as the solvents for polymer binders
during electrolyte processing. The introduction of the long-chain thiol
compound paves the way for more practical, efficient, and scalable
sulfide solid state battery production processes that are compatible
with today’s lithium-ion battery manufacturing infrastructure.

Methods
DFT calculation: The density functional theory (DFT) calculations were
conducted using the classic VASP code 50 . The Perdew-Burke-Ernzerhof

generalized gradient approximation (PBE-GGA) 51 was used for full
relaxation and calculations. A kinetic energy cut-off of 500 eV was used
when applying the projector augmented-wave pseudopotential
(PAW) 52 . The vacuum layer was fixed to 15 Å to prevent interaction
between LPSC and two organic materials (UDCH and UDSH). The
Brillouin-zone (BZ) of the unit cell was sampled using a Γ-centered
3 × 3 × 1 Monkhorst–Pack k-point mesh. All atomic positions were fully
relaxed until the total energy difference was 1 × 10 -5 eV and atomic
force difference was 0.03 eV/Å.

Li6PS5Cl surface engineering: LPSC ( > 95%) was purchased from
NEI corporation and was used as received, UDSH (98%), UDCH (≥99%),
OCSH ( > 98.5%), DOSH ( > 98%), TESH (≥98%) and HESH (99%) was
purchased from Sigma Aldrich and was used as received. The
UDSH@LPSC samples were prepared by planetary mixing LPSC and
UDSH with a 5:1 weight ratio in a 12 mL plastic vial using 6 of zirconium
balls (2 mm diameter) with a planetary mixer (Thinky) for 20 min at
1800 rpm. All samples were handled in a glovebox with oxygen and
water levels below 0.5 ppm.

Li6PS5Cl air exposure: In our home designed air exposure set up,
we used compressed air from Airgas AI UZ300 with 76.5–80.5%
nitrogen and 19.5–23.5% oxygen. The air flow for humidification is set
at 100 linear feet per minute (fpm) until the humidity inside the container stabilizes at 33% relative humidity (RH). The water container,
with a volume of 400 mL, contains a 200 mL volume of water and
200 mL of headspace. The 12-mL plastic vial (Thinky container) with
the mixture of 600 mg of LPSC powder and 120 mg of UDSH, or
600 mg of LPSC powder instead of pellets are put into a 16 oz jar for air
exposure with initial humidity 33%RH at room temperature (20 ± 2 °C).
The exposure times are 5 h, 1 day, 2 days, and 3 days. Real-time monitoring of humidity during LPSC and UDSH@LPSC exposure are
accomplished using a Govee Thermometer Hygrometer positioned in
close proximity to the powder.

After air exposure: The LPSC and UDSH@LPSC samples were
taken into the vacuum oven to dry excess solvent and moisture of the
surface of the materials at80 °C for 2 h with a heating ramp of 1 °C/min.
The dried samples were then moved into the glovebox for further
tests. Note that the complete removal of all UDSH residues can be
achieved through a 300 °C heating process where the crystal structure
and conductivity are consistent with the pristine LPSC. However, we
have found that the 80 o C drying step is sufficient to remove most of
the UDSH without detrimental effect on conductivity and stability
with Li.

LPSC film processing using UDSH as a solvent: A solution comprising 5 wt% HNBR (Sigma Aldrich) in UDSH was prepared at room
temperature (20 ± 2 °C). Subsequently, 600 mg of LPSC and 500 mg
HNBR/UDSH solution was mixed in a 12 mL plastic vial using zirconium
balls with a planetary mixer (Thinky) for 20 min at 1800 rpm, yielding a
uniform wet paste. This paste was then cast into a uniform film using
doctor blade within an Argon filled glove box or a dry room with a dew
point of −28 °C. The thus fabricated film was dried in vacuum at
80 °C for 6 h.
LPSC thin film preparation and AFM characterization: LPSC
thin films were deposited by spin coating onto glass substrates.
LPSC and anhydrous ethanol (≥99.5%, Sigma Aldrich) were used as a
starting material and solvent, respectively. The concentration of LPSC
was 0.1 wt%. The glass substrate was pre-cleaned sequentially by
detergent water, DI water, anhydrous ethanol and acetone (≥99.5%,
Sigma Aldrich) for 10 min each by using a Digital Pro ultrasonic cleaner
and then dried. 200 µL of the coating solution was dropped onto a
glass substrate, which was rotated at 1000 rpm for 60 s by using an
MTI VTC-50A spin coater. The deposited film was heated at 180 °C for
6 h in an Ar filled glovebox to evaporate the solvent. To form selfassembled layers of thiol on LPSC, 20 mg of UDSH or HESH was
deposited onto the surface of the thin film LPSC within an argon-filled

glovebox, followed by vacuum drying at 80 °C for 2 h to remove
unbonded thiol. The surface topography of the LPSC thin film was
characterized using a Park NX20 Atomic Force Microscope (AFM). All
topographical images were captured under ambient air conditions and
at room temperature (20 ± 2 °C), ensuring a brief exposure time of less
than 5 min, utilizing the tapping mode for measurement. Silicon cantilevers, featuring a resonance frequency of 300 kHz and a force constant of 26 N/m, were employed for this purpose. Image processing
and analysis were conducted using the Park Systems XEI software,
facilitating the detailed examination of the thin film’s surface
characteristics.

Materials characterization: Raman spectroscopy (Renishaw™
inVia™) measurements were taken from the range 300 ~ 2500 cm -1 at
an excitation wavelength of 785 nm. All powders were hand ground
and prepared in a glovebox covered with Kapton tape to prevent air
exposure during the measurements. Liquid UDSH samples before
and after air exposure were analyzed via 1 H NMR spectroscopy. To
prepare the sample, 100 μl of UDSH or air exposed UDSH specimen
was mixed with 1000 μL of chloroform D (99%, Sigma Aldrich), and
then transferred to an NMR sample tube. 1 H NMR is performed with a
500 MHz spectrometer (ECA500, JEOL). Powder XRD (D8 DISCOVERY, Bruker) was measured from 10°–80 ° at a scan rate of 2° /
min. The sample was sealed using a Kapton tape. In the cryo-TEM
imaging, the specimens were placed onto a copper grid and affixed
to a dual-tilt cryo-TEM transfer holder within a liquid nitrogen
environment. Cryo-TEM images were captured utilizing a JEM-2100F
electron microscope operating at an acceleration voltage of 200 kV.
XPS analyzes were conducted using an AXIS Supra XPS instrument by
Kratos Analytical. The XPS data was acquired utilizing a monochromatized Al Kα source emitting at 1486.7 eV with samples under
an ultra-high vacuum environment of 10 -8 Torr. The samples were
transferred from a nitrogen-filled glovebox to avoid further air
exposure. Prior to analysis, a 10 keV Ar (1000 atom) cluster source
was applied for a duration of 60 s for surface cleaning. All XPS
spectra were calibrated with the adventitious C 1 s peak at 284.6 eV
and subsequently analyzed using the CasaXPS software.

Solid state NMR: All solid-state NMR spectra were acquired at
18.8 T (800 MHz for 1H) on a Bruker Ultrashield Plus standard bore
magnet equipped with an Avance III console. High resolution 1 H and
31P solid-state NMR spectra were obtained using a 1.3 mm HX MAS
probe and at a magic angle spinning (MAS) speed of 60 kHz. The
powder samples were packed into zirconia rotors sealed with Vespel
caps under argon. A flow of dry N2 gas (2000 L/hr) was used to
control the temperature of rotor and protect the sample from
moisture exposure. A rotor synchronized spin-echo pulse sequence
(90°-τr-180°-τr-acquisition) were used to obtain data. For 1 H, 90° and
180° flip angles of 1.6 μs and 3.2 μs, respectively, at 75 W were used.
For 31 P, 90° and 180° flip angles of 1.5 μs and 3.0 μs, respectively, at
75 W were used. 1 H solution-state spectra were obtained for liquid
UDCH and UDSH using a BBO 800 MHz S4 5 mm probe. Data were
obtained using a direct excitation, single pulse sequence with a 30°
flip angle of 4.8us at 21 W. 1 H chemical shifts were referenced indirectly with adamantane to the 1H signal of tetrakis(trimethylsilyl)
silane at 0.247 ppm 53 . 31 P chemical shifts were referenced to the 31 P
signal of 85% H3PO4 at 0 ppm. 6 Li solid-state NMR spectra were
obtained using a 3.2 mm HXY MAS probe with zirconia rotors sealed
under Ar with Vespel caps at a spinning speed of 20 kHz. The powder
samples were packed in zirconia rotors sealed with Vespel caps
under argon. For the rotor synchronized spin-echo pulse sequence,
90° and 180° flip angles of 8.0 μs and 16.0 μs, respectively, at 200 W
were used. 6 Li chemical shifts were referenced to 1 M LiCl at 0 ppm.
Spectra destined for 1 H quantification in the UDSH@LPSC samples
were obtained using a 2.5 mm HX MAS probe with zirconia rotors
sealed with Vespel caps under Ar at a spinning speed of 20 kHz. A

larger rotor size was used in order to maximize sample content and
1H signal for quantification. The rotor synchronized spin-echo pulse
sequence used 90° and 180° flip angles of 2.66 μs and 5.32 μs,
respectively, at 100 W. T2* measurements on each sample were performed to compensate for any uneven signal decay during the 50 μs
echo delay. On each sample, a series of rotor synchronized spinechos (90°-τr-180°-τr-acquisition) with variable echo delays was
acquired and the spectra were fitted using an in-house package to
obtain a T2* value. To ensure accurate 1 H quantification, a spectrum
and T2* measurement was also obtained on an empty rotor. Thereafter, the same measurements were repeated on a known mass
of adamantane and signal contributions from the empty rotor were
subtracted to calibrate 1 H content to an integrated spectral intensity.
Identical measurements were conducted on a pristine LPSC sample,
and two UDSH@LPSC samples dried at 80 °C and 300 °C, respectively. For each sample, the proton content was calculated accounting for T2* signal decay of each fitted component and contributions
from the empty rotor. In the dried UDSH@LPSC samples, the proton
content of pristine LPSC was subtracted to calculate the
1-undecanethiol content of the sample. 2D exchange spectroscopy
(EXSY). LPSC and UDSH@LPSC were mixed with Li2ZrCl6 (LZC) to
examine exchange of Li between the two electrolytes using 2D EXSY.
The LZC electrolyte was mechanochemically synthesized using LiCl
and a 10% weight excess of ZrCl4, mixed with 15x 10 mm ZrO2
grinding media at 550 rpm for 3 h using a Retsch PM 100 ball mill.
Each of the LPSC sample was hand mixed for 15 minutes with 3 times
the molar amount of LZC to match the lithium content in each
environment. The resulting powder samples were packed in zirconia
rotors and sealed with PTFE tape and Vespel caps under argon. 2D
EXSY spectra were obtained using a 2.5 mm HX MAS probe tuned to
6Li at an MAS speed of 30 kHz. The data were acquired using a rotorsynchronized EXSY pulse sequence with 90-degree pulses of 3.5 μs at
200 W and a recycle delay of 7 s. Chemical shifts were referenced
with respect to a 1 M LiCl solution at 0 ppm. The resulting 2D spectra
were analyzed using TopSpin 3.6 and fit using dmfit.

Battery assembly: To evaluate the electrochemical performance,
ASSBs Swagelok cell composed of a polyaryletheretherketone (PEEK)
mold and Ti rods were assembled. In the symmetric cells, a pressure of
375 MPa was applied to compact 200 mg of solid electrolyte powder
into a pellet with a diameter of 13 mm for 7 min. Lithium metal foil, with
a diameter of 1.11 cm and a thickness of 100 μm (>99.9%, MSE Supplies), was attached to both sides of the electrolyte pellet. Subsequently, the resulting Li|SSE|Li symmetric cell was sandwiched
between two Ti rods. In full cells, the cathode composite was made by
mixing NCM811 (LiNi0.8Co0.1Mn0.1O2, LG Energy Solution) − LPSC
( > 99.9%, Ampcera Inc, used as received) − vapor grown carbon fiber
(>98%, Sigma Aldrich) in the weight ratio of 60:37:3 in a mortar and
pestle. 100 mg of pristine LPSC and 100 mg of air exposed SSEs (specimens in Fig. 3a) were pressed at 30 MPa to form a dual-layered
electrolyte pellet. Following this, a cathode composite weighing
16.2 mg was introduced onto the pristine LPSC side and pressed at
375 MPa for 7 min. The Li metal and In metal foil, with a diameter of
1.11 cm was attached to the side of air exposed SSE and pressed at
125 MPa for 1 min (In foil, 99.99%, 0.127 mm thick from Fisher Scientific). Subsequently, the resulting Li0.5In|air exposed SSE | LPSC|cathode cell was sandwiched between two Ti rods. Symmetric and full cells
were kept at 30 MPa and 55 MPa during testing, respectively. All cells
were assembled in an argon atmosphere glovebox with oxygen and
water levels below 0.5 ppm.

Electrochemical testing: Cell measurements were made on a
LAND multi-channel battery testing system. The galvanostatic chargedischarge tests of symmetric cells was carried out at stepwise
increasing current densities at room temperature (20±2°C) with
0.5 hour per half cycle. The galvanostatic charge-discharge tests of full
cells were conducted within the voltage range of 1.9–3.65 V at a rate of

0.15 mA cm -2 at 60 °C. The impedance measurements were conducted
in the frequency range of 7 MHz to 100 mHz with an applied AC
potential of 5 mV using a frequency response analyzer (Biologic
workstation) at room temperature (20 ± 2 °C). The impedance measurements setup involved the use of 100 mg of electrolyte pressed and
kept at 375 MPa with diameter of 13 mm at room temperature
(20 ± 2 °C), while the Ti rods served as blocking electrodes. All cells
were tested in an argon atmosphere glovebox with oxygen and water
levels below 0.5 ppm.

Data availability
The data that support the findings of this study are available within the
article and its Supplementary Information/Source Data files. Source
data are provided with this paper.

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Acknowledgements
This work was supported by LG Energy Solution–U.C. San Diego Frontier
Research Laboratory (FRL) via the Open Innovation program. This work
was partially supported by the National Science Foundation through the
Materials Research Science and Engineering Center (MRSEC) at UC
Santa Barbara: NSF DMR–2308708. This work was partially supported by
the National Science Foundation Graduate Research Fellowship under
Grant 1650114. This work was performed in part at the San Diego
Nanotechnology Infrastructure (SDNI) of UCSD, a member of the
National Nanotechnology Coordinated Infrastructure (NNCI), which is
supported by the National Science Foundation (Grant ECCS-2025752).
The authors acknowledge the use of facilities and instrumentation supported by NSF through the UC San Diego Materials Research Science
and Engineering Center (UCSD MRSEC), grant # DMR-2011924. The
authors acknowledge the use of facilities and instrumentation at the UC
Irvine Materials Research Institute (IMRI), which is supported in part by

the National Science Foundation through the UC Irvine Materials
Research Science and Engineering Center (DMR−2011967). XPS work
was performed using instrumentation funded in part by the National
Science Foundation Major Research Instrumentation Program under
grant no. CHE−1338173.

Author contributions
P.L. conceived the idea and MC.L., J.J.H. and P.L. designed the experiments. E.S. and T.P. carried out NMR experiments with supervision from
R.J.C. MC.L., J.J.H., S.W., S.F., Z.H., E.L., Q.M. and S.Y. carried out the
other experiments and measurements. K.Z. carried out the calculation.
N.H., J.Z., J.O., M.S. and J.L. helped with discussion. MC.L., J.J.H., E.S.,
K.Z., and P.L. prepared the manuscript with contributions from all
authors. P.L. supervised the research.

Competing interests
P.L., MC.L., J.J.H., K.Z., J.O. and M.S. have filed a US patent application
based on this work. The remaining authors declare no competing
interests.

Additional information
Supplementary information The online version contains
supplementary material available at
[https://doi.org/10.1038/s41467-024-55634-8.](https://doi.org/10.1038/s41467-024-55634-8)

Correspondence and requests for materials should be addressed to
Raphaële J. Clément or Ping Liu.

Peer review information Nature Communications thanks the anonymous, reviewers for their contribution to the peer review of this work. A
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