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com/science/article/pii/S240582972200527X
Manuscript_21942146ddbe3cb3861f25bb7f754d05

High-performance all-solid-state Li–S batteries enabled by an all-electrochem-active

prelithiated Si anode

Weixiao Ji, Xiaoxiao Zhang, Miao Liu, Tianyao Ding, Huainan Qu, Dantong Qiu, Dong Zheng,
Deyang Qu*

Department of Mechanical Engineering, University of Wisconsin Milwaukee, Milwaukee, WI

53211, USA
E-mail address: qud@uwm.edu (D. Qu)

Author statement
Weixiao Ji: Conceptualization, Methodology, Formal analysis, Investigation, Writing–original draft,
Visualization. Deyang Qu: Conceptualization, Writing–review & editing, Project administration.
Xiaoxiao Zhang and Huainan Qu: Methodology. Miao Liu, Tianyao Ding, Dantong Qiu, and Dong
Zheng: Data curation.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships
that could have appeared to influence the work reported in this paper.

Acknowledgements
The research done at the University of Wisconsin Milwaukee was supported by the U.S. Department
of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under the National Energy
Technology Lab Award Number DE-SC0012704 and DE-EE0008859.

© 2022 published by Elsevier. This manuscript is made available under the Elsevier user license
https://www.elsevier.com/open-access/userlicense/1.0/
High-performance all-solid-state Li–S batteries enabled by an all-electrochem-active
prelithiated Si anode

Abstract
The development of all-solid-state Li–S batteries has been greatly impeded by dendrite growth and
dendrite penetration, which are both related to the Li metal anode. As a compromised alternative, we
report lithium silicide (LixSi) as a dendrite-free and high-capacity anode with Li source. The
as-synthesized LixSi is relatively soft, highly electronically conductive, and with a high Li diffusivity.
These distinctive properties make LixSi anode viable as an “all-electrochem-active” electrode
(consisted of 100 wt.% LixSi). Compared with the typical composite electrode, the
all-electrochem-active electrode not merely maximizes the electrode-level energy density but also
minimizes the electrolyte-related interfacial degradation. LixSi symmetric cell demonstrates a
reversible cycling at 4 mA cm–2 for over 320 h. Stress change and morphological evolution of the
LixSi electrode are investigated upon dealloying/alloying. When paired with a S cathode (active mass
loading of 3 mg cm–2), LixSi–S full cell shows a good cycling behavior over 500 cycles and rate
performance (69% capacity retained at 1.2C) even at 25°C.

Keywords
all-solid-state batteries, lithium silicide anode, all-electrochem-active electrode, interface passivation,
sulfide electrolyte

1. Introduction
Li–S batteries have been regarded as a promising candidate for next-generation energy storage
devices, due to their high theoretical energy density (2600 Wh kg–1) as well as the non-toxic and
naturally abundant nature of elemental sulfur [1–4]. The emerging all-solid-state battery (ASSB)
technology can further improve the reliability of Li–S batteries due to the nonflammable feature of
solid-state electrolytes (SSEs) [5–8]. Among all types of SSEs, the highly conductive and easily
processible sulfide-based SSEs are exceptionally suitable for S cathode, due to their similarity in
both chemical composition and chemical potential [9]. Extensive studies on the Li–S ASSBs have

1
been dedicated to the cathode and SSE side, such as engineering cathode architecture and tuning SSE
composition and structure, aiming to accelerate S reaction kinetics while maintaining a high S
content and utilization [10–13]. Whereas less attention has been paid to the anode side and the
extensive full-cell configuration [14].
As the most energy-dense anode, Li metal suffers from dendrite growth and dendrite penetration
when operating at room temperature, especially under high current and high loading conditions. This
results from the intrinsically low self-diffusion rate of Li0, rendering Li0 unable to diffuse away
immediately from the hot spots during plating [15–19]. To accelerate Li0 diffusion, one approach is
to increase the operating temperature (e.g., 60°C). Another approach is to replace the
dendrite-forming Li metal with alloy-based anodes, whose Li+ diffusion coefficient is higher in
comparison with that of pure Li [20,21]. The most regularly used Li-alloys in Li–S ASSBs is LixIn
alloy (x ≤0.5), owing to its steady redox potential and high stability toward sulfide SSEs [9]. Yet, the
application of LixIn alloy in ASSBs is greatly challenged by the high redox potential (≈0.62 V vs.
Li+/Li), low capacity (113 mAh g–1 for Li0.5In), high mass density (7.31 g cm–3) and material cost
($200k ton–1) of In [22]. From a material perspective, exploring a lucrative Li-containing alloy, with
a relatively low redox potential, high theoretical capacity, and fast redox kinetics at room
temperature is an open challenge. From an electrode perspective, exploiting an energy-dense
electrode design that allows both high active material (AM) content and high AM utilization is
urgently needed.
Silicon possesses a high theoretical capacity (3580 mAh g−1 for Li15Si4 phase), a relatively low
delithiation voltage plateau (≈0.35 V vs. Li+/Li), and low cost ($2k ton–1) [23]. After lithiation, the
LixSi alloys can offer a higher cell voltage output compared with the LixIn counterpart, expecting to
boost the specific energy of a Li–S full cell [24–27]. However, only a few pioneering works have
reported the combination of a LixSi anode with a S cathode, not to mention they were all in
liquid-based electrolytes [28–31]. In fact, the capacity fading of most LixSi–S batteries was
alarmingly faster compared with that of conventional Li–S batteries. The continuous capacity decay
stems from the unceasing growth of solid electrolyte interface (SEI), due to the immense volume
change of AMs and the corrosion in polysulfides-dissolved electrolyte. Unfortunately, the 3D porous
architecture of LixSi electrode makes the corrosion more violent compared with a planar Li electrode

2
[32]. Also, the ether-based electrolytes customized for S cathode often are not compatible with the
LixSi anode [33]. To solve the issues of corrosion and non-compatibility, an ultimate solution might
be to replace liquid electrolytes with SSEs in order to preserve the benefits of LixSi–S chemistry. To
the best of our knowledge, an all-solid-state LixSi–S battery has rarely been reported before.
A solid-state electrode is routinely fabricated in a composite electrode structure, where SSE and
conductive carbon are homogeneously dispersed around AM particles to establish well-percolated
charge transfer pathways [34,35]. Recently, an all-electrochem-active electrode concept emerged as
an alternative to the composite electrode design [36]. Due to the complete exclusion of inactive
components (SSE and conductive carbon), the all-electrochem-active electrode is promised to greatly
boost the electrode-level energy density and simplify the electrode fabrication process. More
attractively, the concerns related to the (electro)chemical degradation between sulfide SSEs and
carbon agents within a composite electrode could be dispelled [37]. Principally, an
all-electrochem-active electrode only relies on the interparticle Li+ diffusion and electron transfer
among AMs themselves for charge/discharge. Therefore, seamless interparticle contact is crucial to
ensure unobstructed Li+ diffusion and electron transfer among AMs. Accordingly, desirable AM
candidates for all-electrochem-active electrode configuration should have appropriate mechanical
deformability, electronic conductivity, and Li diffusivity. To date, only graphite, Mo6S8, TiS2, and
silicon have been reported with the all-electrochem-active electrode design [36–40]. But these
electrodes are free of lithium and need to be paired with Li-containing materials as counter electrode.
Interestedly, LixSi exhibits high electronic conductivity and low hardness at a high lithiation level
[37,41]. We thereby envisioned the feasibility of constructing an all-electrochem-active LixSi
electrode to pair with the promising S cathode.
In this contribution, we report high-performance LixSi–S full cells enabled by 100 wt.% LixSi
anode and argyrodite Li6PS5Cl electrolyte. A facile lubricant-assisted ball-milling technique is
introduced to synthesize LixSi, by using Li metal and low-cost microsilicon (μ-Si) as starting
materials. The stress change and morphological evolution of LixSi electrode upon
dealloying/alloying process are revealed. LixSi–LixSi symmetric cell displays reversible cycling over
320 h at 4 mAh cm–2. With S loading of 3 mg cm–2, LixSi–S full cell shows appealing

3
room-temperature cycling performance (76% capacity retention after 500 cycles at 0.3C) and rate
performance (69% capacity retention at 1.2C).

2. Results and Discussion

2.1. Material characterization of μ-LixSi
Numerous prelithiation strategies have been reported for the preparation of LixSi, including
electrochemical lithiation, chemical lithiation, contact prelithiation, etc [27,42–44]. Among them, the
electrochemical lithiation needs to be done in a separate electrochemical cell and thereby is not
practical for the cell production. The chemical lithiation method, despite its growing popularity in
academic research, still concentrates at the laboratory scale due to the complex post-purification step
to remove the residual prelithiation agents. In comparison, the contact prelithation method is broadly
considered as an off-the-shelf strategy due to its high efficiency and no remnants. To further improve
the lithiation uniformity and Li source utilization, herein, a facile lubricant-assisted ball-milling
technique is introduced to synthesize μ-LixSi powder [42]. A stoichiometric amount of μ-Si powder
and pre-cut Li metal pieces were used as precursors and hexane solvent was used as a lubricant.
After high-energy ball milling, the color of the Si-based powder changed from dark brown to black
(Fig. S1). In comparison, without a lubricant, some Li residuals remained unreacted by firmly
sticking to the milling jar, demonstrating a poor lithiation homogeneity. Notably, the
nonhomogeneous lithiation of Si matrix can lead to potential discrepancies between the lithiated
spots and the non-lithiated spots, which could act as a driving force for the self-discharging and
aging behavior of batteries. Thereby, the adoption of a lubricant is pivotal to guarantee a good
lithiation conformity. Fig. 1a displays the X-ray diffraction (XRD) profiles. After milling process,
the pristine crystalline μ-Si (Fig. 1a, up) transformed to amorphous Li3.75Si (Li15Si4) phase (Fig. 1a,
bottom) after lithiation, as indicated by the newly emerged peaks at ca. 21°, 24°, 27°, 40°, and 43.5°.
Despite the Li/Si molar ratio of the precursors is 4.4/1, ca.10% extra Li is still required to obtain a
phase pure Li4.4Si (Li22Si5) compound. Since some unavoidable side reactions related with the
surface impurities of the pristine Si particles need to consume extra Li during milling process [42].
The as-synthesized Li3.75Si compound (denoted as μ-LixSi thereafter) was then used for the following
study. X-ray photoelectron spectroscopy (XPS) analysis of the pristine μ-Si in Fig. 1b shows two
peaks in the region Si 2p, representing the Si–Si bond (98.5 eV) and the Si–O bond (103 eV). The

4
Si–O bond originates from the native oxide layer (SixOy) existed on the surface of Si particles. After
lithiation, the new peak occurring at 101.5 eV is assigned to the Li–Si–O bond formed within LixSi
matrix. Scanning electron images (SEM) show that the pristine μ-Si were separate particles with
rigid edges (Fig. 1c, left), while the particles became expanded and interconnected with smoother
edges after lithiation (Fig. 1c, right).
The pristine μ-Si showed an electronic conductivity of 10–2 mS cm–1 and barely had any ion
diffusivity [37]. After lithiation, μ-LixSi exhibited three orders of magnitude higher electronic
conductivity (50.3 mS cm–1) (Fig. 1d). To evaluate the Li conductivity of μ-LixSi, direct current
(DC) polarization measurement was carried out on Li-In|SSE|μ-LixSi|SSE|Li-In cell, where the SSE
layer acted as an electron-blocking electrode. As illustrated in Fig. 1e, the overall DC resistance
includes two SSE layers (2Rion,SSE), two Li-In|SSE interfaces (2RLi-In|SSE), one μ-LixSi layer
(Rion,μ-LixSi), and two μ-LixSi|SSE interfaces (2Rμ-LixSi|SSE). To estimate the resistance contributed by
the SSE layer and the Li-In|SSE interface, a Li-In|SSE|Li-In cell was further fabricated; its AC
impedance is shown in Fig. 1f. The resistance of SSE layers (2Rion,SSE) and Li-In|SSE interface
(2RLi-In|SSE) was around 49.5 Ω cm2. Therefore, the Li conductivity of the μ-LixSi layer was roughly
calculated to be ˃ 0.1 mS cm–1, since it was hard to decouple the resistance of LixSi|SSE interface
from the overall resistance.

5
Fig. 1. a) X-ray diffraction profiles. b) XPS spectra of the Si 2p region. c) SEM images of the
pristine μ-Si and the as-synthesized μ-LixSi. d) Electronic conductivity measurement of μ-LixSi. e)
DC polarization measurement of Li-In|SSE|μ-LixSi|SSE|Li-In symmetric cell. f) AC impedance
measurement of Li-In|SSE|Li-In symmetric cell.

2.2. Schematic of solid-state electrode configuration

A solid-state electrode for ASSBs is typically a composite electrode design, which resembles
the porous electrode of conventional Li-ion batteries employing liquid electrolytes. As illustrated in
Fig. 2a, a well interconnected electronic–ionic network within the composite electrode is enabled by
the addition of SSE and carbon. Yet, it is well-known that the presence of carbon can be detrimental
to the stability of sulfide SSEs. The carbon-induced extensive interfacial reactions and SEI formation
not only impede Li+ transport but also increase the likelihood of dendrite formation. To ease the
burden caused by carbon-induced SSE decomposition, an all-electrochem-active electrode
(consisting of 100 wt.% AM) is proposed as an alternative. The electrode relies on the
diffusion-based Li+ transport among AM particles themselves to facilitate the alloying/dealloying
reaction. Unlike the composite electrode, the SSE|electrode interface of an all-electrochem-active
electrode is greatly reduced to a 2D plane, indicative of reduced interfacial reaction. Additionally,

6
the “all-in-one” electrode configuration can cut the production cost meanwhile boost the
electrode-level energy density. As illustrated in Fig. 2b, during the delithiation (dealloying) process,
a Li+ concentration gradient is gradually established across the μ-LixSi electrode and provides the
driving force for Li+ to diffuse. A certain degree of μ-LixSi deformation under external force would
allow intimate electronic and ionic contact between μ-LixSi particles, further enabling the reaction to
propagate smoothly throughout the electrode. The passivating SEI plane will be well retained despite
the volume change of μ-LixSi upon cycling.

Fig. 2. a) Schematic of a composite electrode design compared with an all-electrochem-active

electrode design. b) Illustration of the delithiation process of an all-electrochem-active μ-LixSi
electrode.

2.3. Electrochemical performance of μ-LixSi electrode in half cells and symmetric cells
Pellet-type half cells were assembled to investigate the electrochemical behavior of μ-LixSi
electrode. Li-In alloy and argyrodite Li6PS5Cl were used as counter electrode and SSE, respectively.
The pelletized SSE separator is ca. 475 μm thick with a porosity of 3.4% (Fig. S2). For the μ-LixSi
electrode, both an all-electrochem-active electrode and a composite electrode were fabricated by
adopting same amount of μ-LixSi (10 mg) as AM. The all-electrochem-active electrode in Fig. 3a
delivered 630 mAh g–1LixSi during delithiation and 915 mAh g–1 LixSi during lithiation at the 1st cycle.

7
The irreversible capacity as marked in the yellow region could be induced by the incomplete
prelithiation of the as-synthesized LixSi (x=3.75), which was validated by the enhanced delithiation
capacity (≈800 mAh g–1LixSi) at the 2nd cycle (Fig. S3). It is of note that the attainable initial
delithiation capacity can be slightly compromised due to the side reactions in the milling process
associated with the surface impurities of commercialized μ-Si and metallic Li. By contrast, the
composite electrode displays a significantly higher capacity of 1560 mAh g–1LixSi during delithiation
and 2100 mAh g–1LixSi during lithiation. dQ/dV curves in Fig. 3b show that two pairs of redox peaks
occurred at ≈0.4 V for both electrodes, ascribed to the different phase transformation reactions of
μ-LixSi [45]. But the extra peaks appeared at ≈0.9 V for the composite electrode was a sign of SSE
reductive decomposition promoted by carbon additives [46,47].
To analyze the decomposition products, a hand-ground μ-LixSi+SSE sample was prepared to
imitate the interphase between the all-electrochem-active electrode layer and the SSE layer. In
parallel, a ball-milled μ-LixSi+SSE+C sample was also prepared to reveal the interphase formed
within the composite electrode. As shown in Fig. 3c, XRD patterns of the former sample show barely
any new peaks other than the peaks from the pristine SSE, implying the negligible decomposition
products. By contrast, the latter sample presented a strong signal of Li2S while the original SSE
signal disappeared, indicative of massive interfacial reaction within the bulk composite electrode.
Therefore, the all-electrochem-active μ-LixSi electrode exhibited a self-limited interfacial
decomposition and was used thereafter. The voltage profiles of an all-electrochem-active μ-Si
electrode were also investigated in Fig. S4. Unlike the all-electrochem-active μ-LixSi electrode, the
μ-Si electrode displayed a voltage hysteresis in the 1st discharge process but disappeared in the
subsequent cycles. The polarization implies the intrinsic poor electronic/ionic conductivity and
highly tortuous structure of the μ-Si electrode, caused by its Li-deficient and mechanically rigid
nature. Conductive agents and nanostructure engineering are thereby often required for solid-state Si
electrodes [48].
Galvanostatic intermittent titration technique (GITT) was further employed to study the
interfacial evolution of the μ-LixSi electrode during cycling. For each step, a small current pulse was
applied on the cell followed by a 4 h relaxation. The obtained polarization (ΔV) for each step was
then plotted into a relaxation curve as shown in Fig. 3d. Upon oxidation (delithiation) of μ-LixSi (Fig.

8
3e, up), the ΔV value kept constant before a drastic increase above 0.55 V, which could be caused by
the depletion of active Li within the Si matrix. Upon reduction of μ-LixSi (Fig. 3e, bottom), the ΔV
decreased at first followed by a slight increase below 0.09 V. The decrease could be due to the
ameliorated Li diffusion within the Si matrix upon lithiation. The following slight increase could be
induced by Li plating on electrode surface at a low potential, which would slow down the Li kinetic
since the dominated charge carriers transformed from Li atoms (alloy lithiation) to Li vacancies
(lithium deposition) [49]. The diffusion coefficient of Li in the LixSi electrode was calculated to be
5×10–10 cm2 s–1 (Fig. S5).
Current ramping tests were carried out on symmetric cells to investigate the interfacial kinetics
at room temperature. The Li|SSE|Li cell (Fig. S6a) became shorted when the current increased to
0.75 mA cm–2. In contrast, both the Li-In|SSE|Li-In cell (Fig. S6b) and the μ-LixSi|SSE|μ-LixSi cell
(Fig. S6c) displayed reversible kinetics even at 4 mA cm–2. Prolonged cycling test at 4 mA cm–2 and
4 mAh cm–2 showed that the Li-In|SSE|Li-In cell experienced a severe voltage hysteresis until
reaching the cutoff voltage (–5V) after 13 cycles (Fig. 3g) while the μ-LixSi|SSE|μ-LixSi cell
remained stable cycling over 325 h (Fig. 3f). The inferior Li kinetic of the Li-In electrode compared
with the μ-LixSi electrode was also validated in previous work [37].

Fig. 3. a) Voltage profiles of the μ-LixSi|SSE|Li-In half cells at 0.02C and 60°C, b) corresponding

9
dQ/dV curves. c) XRD patterns. d) GITT curve and e) polarization plots of the μ-LixSi|SSE|Li-In half
cell at 0.02C and 60°C. Prolonged cycling of f) the μ-LixSi|SSE|μ-LixSi symmetric cell and g) the
Li-In|SSE|Li-In symmetric cell at 25°C.

2.4. Morphological evolution of Si-based electrodes

To visualize the morphological evolution of Si-based electrode upon cycling, cross-section SEM
images of a μ-Si electrode and a μ-LixSi electrode were compared at different lithiation levels. Same
amount (5 mg) of μ-Si and μ-LixSi was loaded to prepare the pristine all-electrochem-active
electrodes. As shown in Fig. 4a-b, the thickness of μ-Si electrode and μ-LixSi electrode is 41 μm and
67 μm after cold pressing, respectively. By referring to Eq. S1, the electrode porosity is 57% for μ-Si
electrode and 23% for μ-LixSi electrode, respectively. The weight and volume percentage of the
μ-LixSi electrode can reach up to 100% and 77%, respectively. From the enlarged views, the μ-Si
electrode (Fig. 4a, right) presents discrete microscale Si particles with distinct edges while the
μ-LixSi electrode (Fig. 4b, right) presents merged particles with smoother edges. The more densified
microstructure of the μ-LixSi electrode originates from the reduced hardness upon lithiation (≈11
GPa for Si versus ≈1.4 GPa for LixSi) [41]. The μ-LixSi electrode thereby possess a lower tortuosity,
which is beneficial to the through-plane Li+ diffusion. Subsequently, the μ-LixSi electrode was fully
delithiated and then fully lithiated, with the electrode layer contracting to 32.5 μm (Fig. 4c, left)
followed by re-expanding to 62.7 μm (Fig. 4d, left). The enlarged views (Fig. 4b-d, right) present
that the pristine μ-LixSi merged into larger interconnected particles with voids in between upon
charge/discharge. Unlike a pure Li electrode with a plating/stripping mechanism, voids formed
within the bulk μ-LixSi electrode instead of along the electrode|SSE interface, which can prevent the
formation of hot spots at the interface and the possible Li penetration. Apart from no Li penetration,
there was also no obvious cracking of the electrode throughout cycling (Fig. S7).

10
Fig. 4. a) Cross-section SEM images of a) pristine μ-Si electrode, b) pristine μ-LixSi electrode, c)
fully delithiated μ-LixSi electrode, and d) fully lithiated μ-LixSi electrode.

2.5. In-situ stress evolution of μ-LixSi electrode

The volume change of μ-LixSi electrode was explored by in-situ monitoring the dynamic
pressure change of μ-LixSi|SSE|Li4Ti5O12 full cell. Since the phase transition of Li4Ti5O12 (LTO)
cathode causes negligible volume change, the net stress change of the full cell is governed by the
μ-LixSi anode alone. Fig. S8 displays the thickness and morphology of LTO composite cathode.
Voltage profiles of full cell (Fig. 5a, up) along with the correlated evolution of stress (Fig. 5a,
middle) and the stress change (Fig. 5a, bottom) were recorded over five consecutive cycles. Fig. 5b
illustrates the stress measurement setup and Fig. 5c shows the corresponding dQ/dV curves. With an
areal capacity of ≈3 mAh cm–2, the full cell exhibited ≈0.7 MPa stress swing upon cycling, with a

11
stress decrease during discharge (Li extracted from μ-LixSi) and an increase during charge (Li
inserted to μ-LixSi). Theoretically, the stress change only depends on the quantity of Li inserted or
extracted from the μ-LixSi electrode, which is proportional to the areal capacity. But in real scenarios,
the stress change can be weakened due to the elastic deformation of SSE layer and the presence of
pores and void spaces within the cell. For example, the thicker the SSE layer is, the smaller stress
change would be detected. As shown in Fig. 5a (bottom) and Fig. 5d (bottom), a relatively large
stress hysteresis (irreversibility of stress change) is revealed from the initial cycle, which gradually
vanishes in the subsequent cycles. At the 5th cycle, the stress change became highly reversible upon
charge/discharging (Fig. 5a, bottom). The weakening of stress hysteresis could be attributed to the
rearrangement of pristine void space within the cell along the contraction and expansion of μ-LixSi at
the initial cycles. Also, stress hysteresis caused by the irreversible trap of some active Li inside the
LTO structure during the 1st cycle, as revealed by the initial Coulombic efficiency of 97.0% (Fig. 5d,
up), would disappear in the following cycles.

Fig. 5. a) The voltage profiles of μ-LixSi|SSE|LTO cell (up) along with correlated evolution of stress
(middle) and stress change (bottom). b) Schematic of pressure-monitoring cell. c) Corresponding
dQ/dV curves. d) Voltage and stress change plotted as a function of the molar amount of lithium
extracted from or inserted into the μ-LixSi phase.

2.6. Electrochemical performance of LixSi–S full cells

12
 Full cell performance was evaluated by pairing a S cathode with a pure Li anode, a Li-In alloy
anode, and a μ-LixSi alloy anode, respectively. All cells with an areal S loading of 3 mg cm–2 were
first tested under 60°C and ≈50 MPa. Li|SSE|S cell (Fig. S9a) became quickly shorted in the initial
charging process, induced by Li dendrite formation during Li plating. -LixSi|SSE|S cell (Fig. S9b-c)
displayed a discharge voltage plateau of 1.75 V, which is 280 mV higher than that compared with
Li-In|SSE|S cell (Fig. 9d-e). The discharge plateau represents the solid–solid conversion between S
and Li2S occurred within the S cathode. Long-term cycling tests were next carried out. Li-In|SSE|S
cell in Fig. 6a showed a rapid capacity fading after 50 cycles and became shorted at the 88th cycle. It
is noteworthy that a relatively high mass loading and high current condition could cause cavity
formation at the Li-In|SSE interface and unexpectedly Li-In filament growth, which would result in
capacity decay and cell failure [50]. In comparison, μ-LixSi|SSE|S cell in Fig. 6d showed stable
cycling and retained 85.4% capacity after 200 cycles. Cyclic voltammetry (Fig. S10) and voltage
profiles (Fig. S11) at different cycles displayed a highly reversible electrochemical behavior. Under
high current of 1C (1C=1600 mA g–1), Li-In|SSE|S cell only delivered 427 mAh g–1 (Fig. 6b-c),
whereas μ-LixSi|SSE|S cell can deliver 1301 mAh g–1 (Fig. 6e-f), again implying the more favorable
dealloying/alloying kinetics of μ-LixSi alloy compared with Li-In alloy. During a complete
charge/discharge cycle, the EIS evolution in Fig. S12 did not differ much except at the fully charged
state. The increased resistance is ascribed to higher interfacial resistance induced by the partial
oxidation of SSE at the cathode side.
Room-temperature operation has been a long-standing challenge to achieve ideal practical
application of ASSBs. Therefore, cycle life and rate capability of μ-LixSi|SSE|S cell were evaluated
at 25°C. Fig. 6g shows 76.3% capacity was retained after 500 cycles under 0.3C. Under 1.2C, an
accessible capacity of 866 mAh g–1 was achieved, corresponding to 69% of the capacity under 0.05C
(1249 mAh g–1). Table S1 summarizes the state-of-the-art Li–S ASSBs based on sulfide electrolytes
and Li-based anodes. Table S2 lists the parameters and performance of the reported LixSi–S batteries,
mostly in ether-based electrolytes. Our work stood out as one of the best results in terms of attainable
capacity and cycle life. More importantly, the all-electrochem-active and dense LixSi electrode in our
work set a precedent for developing Si-based electrodes with high electrode-level energy density.

13
Fig. 6. a) Cycling and b-c) rate performance of Li-In|SSE|S full cell at 60°C. d) Cycling and e-f) rate
performance of μ-LixSi|SSE|S full cell at 60°C. g) Cycling and e-f) rate performance of
μ-LixSi|SSE|S full cell at 25°C.

3. Conclusion
In summary, a facile solvent-assisted ball milling technique was introduced to prepare μ-LixSi
alloy. Derived from its distinctive properties, an all-electrochem-active μ-LixSi electrode architecture
has been validated to be feasible. When paired with S cathode, the all-solid-state LixSi–S batteries
show appealing rate and cycling performance at room temperature. To fully unleash the potential of
Si-based anode, advanced cell designs with a thinner electrolyte film and a lower stack pressure need
to be further explored. Overall, this work paves a pathway to solve the longstanding interface-related
14
issue of LixSi anode and advances the development of high-performance and high-energy-density
Li–S ASSBs.

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High-performance all-solid-state Li–S batteries enabled by an all-electrochem-active

prelithiated Si anode

Weixiao Ji, Xiaoxiao Zhang, Miao Liu, Tianyao Ding, Huainan Qu, Dantong Qiu, Dong Zheng,

Deyang Qu*

Graphical abstract