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\begin{document}

\title{Construction of Dynamic Alloy Interface for Uniform Li Deposition in
Li-Metal Batteries}



\author[1]{Guang He}%
\author[1]{Qingwen Li}%
\author[1]{Ziheng Zhang}%
\author[2]{Zelong Yang}%
\author[1]{Yulu Liu}%
\author[2]{Jinjie Chen}%
\affil[1]{Tianjin University of Technology}%
\affil[2]{Tianneng Co. Ltd}%


\vspace{-1em}



  
  \date{May 25, 2024}


\begingroup
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\selectlanguage{english}
\begin{abstract}
It is well accepted that a lithiophilic interface can effectively
regulate Li deposition behaviors, but the influence of the lithiophilic
interface is gradually diminished upon continuous Li deposition that
completely isolates Li from the lithiophilic metals. Herein, we perform
in-depth studies on the creation of dynamic alloy interface upon Li
deposition, arising from the exceptionally high diffusion coefficient of
Hg in the amalgam solid solution. As a comparison, other metals such as
Au, Ag and Zn have typical diffusion coefficients of 10-20 orders of
magnitude lower than for Hg in the similar solid solution phases. This
difference induced compact Li deposition pattern with an amalgam
substrate even with a high areal capacity of 55 mAh cm-2. This finding
provides new insight into the rational design of Li anode substrate for
the stable cycling of Li metal batteries.%
\end{abstract}%



\sloppy


Article category: Research Article

Subcategory: Lithium Ion Batteries

Construction of Dynamic Alloy Interface for Uniform Li Deposition in
Li-Metal Batteries

Qingwen Li, Yulu Liu, Ziheng Zhang, Jinjie Chen, Zelong Yang, and Guang
He*

Q. Li, Y. Liu, Z. Zhang, Prof. G. He

Tianjin Key Laboratory of Advanced Functional Porous Materials,
Institute for New Energy Materials and Low-Carbon Technologies, School
of Materials Science and Engineering, Tianjin University of Technology,
Tianjin 300384, China\emph{E-mail address:heguang@email.tjut.edu.cn}

J. Chen, Z. Yang, Prof. G. He

Tianneng Co. Ltd, Huzhou 313100, China

Keywords: uniform Li deposition, dynamic alloy interface, Li solid
solution, Li dendrites, diffusion coefficient

It is well accepted that a lithiophilic interface can effectively
regulate Li deposition behaviors, but the influence of the lithiophilic
interface is gradually diminished upon continuous Li deposition that
completely isolates Li from the lithiophilic metals. Herein, we perform
in-depth studies on the creation of dynamic alloy interface upon Li
deposition, arising from the exceptionally high diffusion coefficient of
Hg in the amalgam solid solution. As a comparison, other metals such as
Au, Ag and Zn have typical diffusion coefficients of 10-20 orders of
magnitude lower than for Hg in the similar solid solution phases. This
difference induced compact Li deposition pattern with an amalgam
substrate even with a high areal capacity of 55 mAh
cm\textsuperscript{-2}. This finding provides new insight into the
rational design of Li anode substrate for the stable cycling of Li metal
batteries.

1. Introduction

Nowadays, Li metal anode is among the most popular topics in the field
of battery research due to its ultra-high theoretical capacity (3860 mAh
g\textsuperscript{-1}) and low electrochemical redox potential (-3.04 V
vs. the standard hydrogen electrode).\textsuperscript{{[}1-4{]}} Yet the
uncontrolled Li plating/stripping is a fatal problem for its practical
application.\textsuperscript{{[}5-7{]}} Especially, unevenly distributed
electric fields cause lithium ions to deposit irregularly, resulting in
large amounts of dendritic or mossy lithium on the surface of Li metal
electrode.\textsuperscript{{[}8-10{]}} On the other hand, P-zone metal
anodes (Si, Sb, Sn, Ge\ldots{}) possess high capacities with little
risks of dendrites due to the inward diffusion of deposited Li atoms
driven by the essential alloying
reactions.\textsuperscript{{[}11-18{]}}The surface alloying process has
been successfully applied to Li metal anodes to regulate Li deposition
behaviors.\textsuperscript{{[}19-23{]}}

Electrochemical deposition morphology is largely affected by the
substrate properties such as absorption energy, nucleation barrier,
ionic mobility and exchange current
density.\textsuperscript{{[}24-28{]}} Certain substrate with definite
solubility in Li is preferable for reducing Li deposition
barriers.\textsuperscript{{[}29{]}} For example, the formation of
solid-solution alloy at the Li-rich region allows much reduced Li
nucleation potential for Au substrate.\textsuperscript{{[}30{]}} The
doping of small amount of Mg into Li substrate also greatly alters the
surface energy and results in distinct deposition morphologies from pure
Li substrate.\textsuperscript{{[}31,32{]}} Nonetheless, the substrate
influence is gradually decayed during Li accumulation due to the fact
that the original surface is gradually covered by deposited Li and thus
the uncontrolled morphologies remain unavoidable in practical Li metal
cells with large areal capacities and high current densities.

Hg is a unique metal that is thermodynamically and kinetically favorable
to form alloys with many metals.\textsuperscript{{[}33-35{]}} For
example, the alloying reaction is readily processed by casting Hg drops
onto Li foil without further treatment at room
temperature.\textsuperscript{{[}36{]}} The Li-Hg composite anodes with
Li amalgam on the top and Li metal at the bottom afford fast adsorption
of Li deposition in electrochemical cells, that is, the elimination of
dendrite morphologies at high current densities. In fact, the amalgam
layer can be easily peeled off from Li foils and served as an alloy
substrate due to the flexible, self-supported and ultra-thin
characteristics. Unlike regular metal substrates, Li-Hg interface is
kinetically maintained even with a high plating capacity, which is
distinct amalgams from other metal substrates that can only form Li-M
(M=metal) at the surface. The uniquely super-fast diffusion of Hg atoms
in the Li-rich Li-Hg solid solution phase affords fresh amalgam
interface during electrochemical Li deposition.

2. Results and discussion

To study different Li-M solid solution formation and their influence on
Li deposition, we first compared binary Li-M phase diagrams with
selected metals Hg, Ag, Au and Zn, respectively. \textbf{Figure 1} a
shows phase diagrams of these Li-M solid solution compositions in the
range of Li atomic ratio near 100\%.\textsuperscript{{[}37{]}} The
solubility of Li in the metal substrates significantly improve the
deposition interface and lead to much reduced overpotential upon Li
nucleation.\textsuperscript{{[}30{]}} The assembly of the cells
comprised of Li metal and various substrates are presented in Figure 1b,
in which Li foil was used as the counter electrode and the substrate for
Li deposition. The Ag, Au and Zn thin foils were purchased and cut into
desired size for use. LiHg film electrodes were synthesized by the
simple drop-casting method.\textsuperscript{{[}36{]}} 5 \selectlanguage{greek}μ\selectlanguage{english}L Hg was coated
onto 10 cm\textsuperscript{-2} pure Li foil to spontaneously form thin
alloy film (about \textasciitilde{}7 \selectlanguage{greek}μ\selectlanguage{english}m in thickness). LiHg film has a
lightweight areal density of 7 mg cm\textsuperscript{-2} and composition
of Li\textsubscript{0.46}Hg\textsubscript{0.54} (Figure S1).

In Figure 1c, the LiHg film shows a two-step feature in the curve. The
onset of voltage sharp-drop is attributed to the vast Li deposition on
the surface of the LiHg electrode at a large current density of 2 mA
cm\textsuperscript{-2}. However, the voltage is rapidly recovered to
above 0 V vs. Li\textsuperscript{+}/Li due to the formation of Li-Hg
alloys. After Li is saturated in the amalgam, Li deposition appears as
indicated by the flat curve below 0 V. Thus, LiHg substrate exhibits 3
distinct steps upon Li deposition: the initial Li nucleation, the
subsequent alloying between Li and LiHg, and the Li deposition on the
lithiated amalgam. This feature is not presented for other metal
substrates, which only have the sharp dip and the following flat curve
below 0 V. The deposition behaviors of Li on Au, Ag and Zn substrates in
this study is consistent with the previous studies by other
groups.\textsuperscript{{[}38-40{]}} The unique Li deposition process on
the amalgam substrate is correlated to the fast Li-Hg alloying reaction
that allows immediate Li diffusion into the amalgam phase above 0 V.
This assumption is also verified by the violent alloying upon the
contact between fresh Li and Hg even at room temperature when prepared
the LiHg film substrate (Figure S2).

We performed in-depth studies to understand the Li-Hg alloying
process.\textbf{Figure 2} a shows cross-section scanning electron
microscope (SEM) images of LiHg film with different Li deposition
capacities (0.0, 2.3, 3.1, 5.0, 9.0, 55.0 mAh cm\textsuperscript{-2},
respectively) at 2 mA cm\textsuperscript{-2}. A two-layer morphology is
clearly shown with the Li capacity of 2.3 mAh cm\textsuperscript{-2}. In
Figure 1c, the lithiation of LiHg film is completed above 1.5 mAh
cm\textsuperscript{-2}, followed by Li deposition on the amalgam
surface. The two-layer morphology of the electrode confirms the
electrochemical process. Both layers gradually expanded upon the
increase of Li deposition capacities, but the compact electrode feature
is maintained even with a high volume of 55 mAh cm\textsuperscript{-2}.
The growth of the bottom layer indicates it was not simply a
lithiation-deposition process. Instead, the amalgam layer was actively
involved in the Li deposition even after Li was saturated in the amalgam
solid solution phase to yield the compact Li layer with smooth surface
(Figure S3--S5).

The structures of deposited electrodes were analyzed with ex-situ XRD
shown in Figure 2b and Figure S6. The as-prepared LiHg film is consisted
intermetallic compounds of LiHg\textsubscript{3}, Li\textsubscript{3}Hg
and trace amounts of metallic Li or Li-rich Li-Hg solid solution. The
initial lithiation convert LiHg\textsubscript{3} into
Li\textsubscript{3}Hg within 10 min deposition (Li capacity of 0.34 mAh
cm\textsuperscript{-2}) and have completely evolved sole
Li\textsubscript{3}Hg phase after 20 min (\textasciitilde{} 0.67 mAh
cm\textsuperscript{-2}). This fast phase transformation is crucial to
guide the initial Li diffusion into the inner phase at a high current
density. With increased Li plating time to 80 min (\textasciitilde{}2.70
mAh cm\textsuperscript{-2}), Li\textsubscript{3}Hg is the main phase in
the pattern as indicated by the 23.520\textsuperscript{o},
27.220\textsuperscript{o} and 38.860\textsuperscript{o} peaks,
corresponding to the (111), (200), (220) diffractions. The growth of the
characteristic diffraction peaks indicates the alloying reactions were
dominant process in electrodes. The diffraction peak at
35.920\textsuperscript{o} is emerged and strengthened in subsequent
process (\textgreater{}80 min), suggest the nucleation and accumulation
of lithium atoms on the surface of the amalgam. Combined
electrochemistry, SEM and XRD results, the alloying process (stage I) is
the phase transition from LiHg\textsubscript{3} to
Li\textsubscript{3}Hg, while the subsequent Li deposition gives high
compact Li layer with the involvement of Hg (stage II) (Figure 2c).

As discussed above, it is highly possible that the Li deposition process
on the top of the amalgam layer is affected by Hg to obtain compacted
growth of Li layer. To examine this assumption, Energy disperse
spectroscopy (EDS) mappings, HR-TEM and Cs-corrected TEM were employed
to explore the composition and structure of the Li layer (\textbf{Figure
3} ). The electrodes with a Li capacity of 5 mAh
cm\textsuperscript{-2}were selected for the analysis of the compositions
of the Li layer. First, the electrode was examined by SEM and EDS
mapping. The EDS mapping clearly confirm the existence of Hg atoms in
the Li layer at micron scale (Figure 3a). Next, a sample was carefully
prepared by FIB (Figure S7) obtained from the top layer of the
electrode. The average thickness of the sample is \textasciitilde{}3 \selectlanguage{greek}μ\selectlanguage{english}m
to avoid any contamination from the bottom Hg-containing layer. It is
not easy to probe Li by EDS, but the electron energy loss spectroscopy
(EELS) spectrum still shows strong Li signals at 56.0 eV in this sample
(Figure 3b).\textsuperscript{{[}41,42{]}} XPS spectra confirm Hg 4f
peaks at 101.9, 103.9 eV as well as Li peak at 54.9 eV. The peaks can be
assigned to the metallic mercury and lithium (Figure 3c and d) with the
atomic ratio 1:99 for Hg:Li (Figure S8).\textsuperscript{{[}43,44{]}} In
addition, HR-TEM tests of the sample further confirm Hg is distributed
in the Li layer (Figure 3e--h). All the combined results suggest Hg can
diffuse upward along with the electrochemical deposition by forming a
dynamic alloy interface to regulate Li deposition pattern, as shown in
the SEM images in Figure 2.

In contrast, other selected substrates (Ag, Au and Zn foils) exhibit
different deposited Li

morphologies under the same electrochemical condition (2 mA
cm\textsuperscript{-2}, 5 mAh cm\textsuperscript{-2}). The porous and
loosely packed dendrites are clearly observed on the surface of theses
substrates upon Li deposition, and there is little Ag, Au and Zn being
detected in the deposition layer (\textbf{Figure 4} a--c), a sharp
contrast to observation on the LiHg substrate. The absence of Ag, Au and
Zn are also evidenced by the XPS analyses with the deposited Li layer
(Figure S9). These results imply the critical role of surface alloying
process in avoiding dendric morphologies. Along with the coverage of the
initial interface upon Li plating, the alloying function becomes weaker
and dendric morphologies appear for Ag, Au and Zn substrates (Figure
4d).

To understand the inherent different lithiation behaviors between Hg and
other metals, the diffusion coefficient (\emph{D} ) of each metal was
calculated in the Li-rich Li-M alloys. As shown in the phase diagrams,
the Li-rich zone has a solid solution phase for the selected metals M
(Hg, Au, Ag and Zn). The alloy diffusion theory can be explained with
Darken equation in a binary A-B alloy:\textsuperscript{{[}45{]}}

\(D=D_{A-B}=D_{A}x_{B}+D_{B}x_{A}\)(1)\textsuperscript{{[}46,47{]}}

Where A and B refer to Li and M (Ag, Au, Zn and Hg),
respectively.\emph{D\textsubscript{Li}} and \emph{D\textsubscript{M}}
are intrinsic diffusion coefficient of Li and M, and \emph{x}
\textsubscript{Li} and\emph{x} \textsubscript{M} are concentration of Li
and M in this study. For the Li-rich solid solution phase, it
has\emph{x\textsubscript{Li}} -100\% and\emph{x\textsubscript{M}} -0,
thus the above equation can be simplified as \emph{D}
=\emph{D\textsubscript{M}} (M=Ag, Au, Zn or
Hg).\emph{D\textsubscript{M}} can be calculated according to the

diffusion equation:

\(D_{M}=D_{0}\exp\frac{-Q_{\text{sd}}}{\text{RT}}\)(2)\textsuperscript{{[}48,49{]}}

In which, \emph{R} is the ideal gas constant (\emph{R} =8.314 J
mol\textsuperscript{-1} K\textsuperscript{-1}), \emph{T} is the room
temperature (\emph{T} =298 K), \emph{D\textsubscript{0}} is the
frequency factor of the atom and \emph{Q\textsubscript{sd}} is the
diffusion activation energy, respectively. \emph{D\textsubscript{o}}
and\emph{Q\textsubscript{sd}} of Ag, Au, Zn and Hg atoms are shown
in\textbf{Table 1} , respectively.\textsuperscript{{[}45{]}} By equation
(2), the diffusion coefficient of Ag, Au, Zn and Hg atom is calculated
as 1.8*10\textsuperscript{-31}, 1.0*10\textsuperscript{-30},
1.1*10\textsuperscript{-15},
1.55*10\textsuperscript{-3}mm\textsuperscript{2} s\textsuperscript{-1},
respectively. It is clearly that \emph{D\textsubscript{Hg}} is 28, 27
and 12 orders of magnitude higher than for \emph{D\textsubscript{Ag}} ,
\emph{D\textsubscript{Au}}and \emph{D\textsubscript{Zn}} , respectively.
Meanwhile, the radial distance \emph{R} (or net displacement) of an atom
can be estimated by the follow equation.

\(R=\sqrt{D*t}\) (3)\textsuperscript{{[}50{]}}

Where \emph{t} represents diffusion time (s), \emph{D} is the
interdiffusion diffusion coefficient
(mm\textsuperscript{2}s\textsuperscript{-1}). Thus, the radial distance
\emph{R} of each metallic atom can be up to 4.2*10\textsuperscript{-16},
1.0*10\textsuperscript{-15}, 3.2*10\textsuperscript{-8},
3.9*10\textsuperscript{-2} mm s\textsuperscript{-1}, respectively. The
results reveal Hg can migrate as much as 3-14 orders of magnitude
farther than for other metals \textbf{(Figure 5} a). Ideally, the
plating capacity of 2 mAh (2 mA cm\textsuperscript{-2} current with 1 hr
time and 1 cm\textsuperscript{2} square condition) corresponds to a
thickness of \textasciitilde{}9.7 \selectlanguage{greek}μ\selectlanguage{english}m. According to the calculated radial
distance\emph{R} , the super high Hg diffusion coefficient allows a
migration distance of 39 \selectlanguage{greek}μ\selectlanguage{english}m s\textsuperscript{-1}, which indicates Hg
can easily migrate from the LiHg substrate to the top
electrolyte/electrode interface to mitigate the formation of Li
dendrites through the alloying process. Instead, Ag (Au or Zn) has very
limited diffusion distance of 4.2*10\textsuperscript{-13} \selectlanguage{greek}μ\selectlanguage{english}m
(1.0*10\textsuperscript{-12} or 3.2*10\textsuperscript{-5} \selectlanguage{greek}μ\selectlanguage{english}m) within
the same time. The significant difference on metal diffusion coefficient
reveals these metals can only regulate Li plating patterns with small
current density and capacity, while Hg substrate is capable of evolve to
a dynamic Li-Hg interface for uniform Li deposition (Figure 5b).

Further studies on plating/stripping cycling were compared between Zn
substrate and LiHg film at 2 mA cm\textsuperscript{-2} and areal
capacity of 2 mAh cm\textsuperscript{-2}. The upper voltage was set 1.0
V when evaluated the Coulombic efficiencies. The cell with a LiHg film
shows stable stripping/plating over 400 hrs, and the Li\textbar{}LiHg
film cell exhibits superior Coulombic efficiency (100\%) over 160 cycles
(\textbf{Figure 6} a and b). The stable potential hysteresis indicate a
LiHg film can effectively guide Li deposition and stripping behaviors by
avoiding dead lithium and dendrites formation (Figure 6c). The
Li\textbar{}Zn cell exhibits a short-circuit phenomenon and unstable
columbic efficiency in the initial cycles (Figure 6d). Full cells were
also assembled with a high LiFePO\textsubscript{4} (LFP) loading of 12
mg cm\textsuperscript{-2}. LiHg film\textbar{}LFP full cell delivers a
stable capacity about 100 mAh g\textsuperscript{-1} after 100 cycles at
a high rate of 2C (1C=170 mA g\textsuperscript{-1}), while the Zn
foil\textbar{}LFP cell shows obvious capacity decay only in 40 cycles
(Figure 6e--g).

3. Conclusion

In summary, it is the first time to propose the concept of dynamic
alloying interface to regulate Li deposition pattern. The exceptionally
high diffusion coefficient of Hg allows its rapid migration from the
substrate to the top electrolyte/electrode interface, thus effectively
mitigate the formation of Li dendrites at high plating current (2 mA
cm\textsuperscript{-2}) and capacities (5 mAh cm\textsuperscript{-2}).
This unique feature is distinct from other metals such as Au, Ag and Zn,
which only work with the initial Li plating onto the substrates. This
study provides new insight into the rational design of the plating
substrates. Metals with low melting points such as Hg, Ga and In may
play a critical role in tailoring substrate compositions. Further
progress is expected with these metals for the design of binary or
ternary alloy substrates, or accurate control of coating species on
regular Cu substrates.

\textbf{4. Experimental Section}

\emph{Materials:} The pristine self-supported LiHg film was obtained by
coating method in an argon-filled glovebox with \textless{}0.1 ppm
O\textsubscript{2} and H\textsubscript{2}O. The preparation of LiHg film
was as follows: (1) mercury droplet was spread onto the pure lithium
metal to spontaneously form LiHg film by a brush; (2) this film was
peeled off the pure lithium metal, the thickness of the film is about 7
\selectlanguage{greek}μ\selectlanguage{english}m in thickness; (3) the obtained thin film was cut into squares of 1*1
cm\textsuperscript{2} by a scissor as electrode. After weighing of this
self-supported film, the surface load of LiHg film is 7 mg
cm\textsuperscript{-2}, and the surface load of Hg was 6.8 mg
cm\textsuperscript{-2} (5 \selectlanguage{greek}μ\selectlanguage{english}L liquid phase Hg was coated on 10
cm\textsuperscript{-2} Li foil), thus the surface load of Li was 0.2 mg
cm\textsuperscript{-2}. The commercial Ag, Au and Zn foils have the same
1*1 cm\textsuperscript{2} squares by a scissor with LiHg film, whose
possess thickness of 10, 2 and 10 \selectlanguage{greek}μ\selectlanguage{english}m, respectively.
LiFePO\textsubscript{4} (LFP) cathode material was provided by Lishen
company with mass loading of 12 mg cm\textsuperscript{-2}.

\emph{Physical Characterization:} Scanning Electron Microscope (SEM)
studies were carried out on Environment Scanning Electron Microscope
with a field emission gun (Quanta FEG 250). X-ray diffraction (XRD)
patterns were collected on a Rigaku Miniflex 600 desktop at 40 kV and 20
mA (Cu K\selectlanguage{greek}α\selectlanguage{english}radiation). Transmission Electron Microscope (TEM) analysis was
used on a High-Resolution Transmission Electron Microscope with FEG
(Talos F200 X) at 200 kV (HR-TEM) and Transmission Electron Microscope
with A Probe Corrector (Titan Themis Cubed G2 60-300) (Cs-TEM). Focused
Ion Beam (FIB) sample was synthesized on FIB-SEM system (Helios Nanolab
460HP) at 5 kV and 30 kV (Ga ion beam etching). X-Ray Photoelectron
Spectroscopy (XPS) characterization were measured with an X-Ray
Photoelectron Spectroscopy (Escalab 250Xi) spectrometer. Optical images
were conducted with a Keyence VHX-950F microscope and cell phone.

\emph{Electrochemical Evaluation:} Coin half cells and full cells were
assembled in an Ar-filled glove box (O\textsubscript{2} and
H\textsubscript{2}O level below 0.1 ppm). In half cells, Ag, Au, Zn
foils and LiHg film were acted as working electrodes and pure lithium
metal (thickness of 600 \selectlanguage{greek}μ\selectlanguage{english}m) as counter electrode. In full cells, LFP
electrode worked as cathode (12 mg cm\textsuperscript{-2} of mass load),
the LiHg film and Zn foil anodes were pre-deposited Li capacity of 4 mAh
cm\textsuperscript{-2}. The electrolyte was 1.0 M lithium
bis-(trifluoromethane-sulphonyl)imide (LiTFSI) in 1,3-dioxolane (DOL)
and 1,2-dimethoxyethane (DME) (1:1 vol/vol) without any additives. About
100 \selectlanguage{greek}μ\selectlanguage{english}L of electrolyte was used in each coin cell to standardize the
experiment. The three piece of separators with
Al\textsubscript{2}O\textsubscript{3} coating layer (Celgard 2400) was
placed in the middle of two electrodes to protect from short-circuit in
the cells. All electrochemical tests were carried out on LAND-CT 2001A
multichannel battery tester (Wuhan, China) at room temperature.
Electrochemical impedance spectroscopy (EIS) measurements were conducted
on a Princeton PARSTAT 2273. The frequency was ranged from 1 MHz to 0.01
mHz with an alternating voltage signal amplitude of 5 mV.

Conflicts of interest

There are no conflicts to declare.

Acknowledgements

This work was supported by the National Key Research and Development
Program of China (2019YFA0205700).

Received: (will be filled in by the editorial staff) Revised: (will be
filled in by the editorial staff) Published online: (will be filled in
by the editorial staff)

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\textbf{Table 1.} The frequency factor (\emph{D\textsubscript{0}} ) and
diffusion activation energy (\emph{Q\textsubscript{sd}} ) of Ag, Au, Zn
and Hg atom.\selectlanguage{english}
\begin{longtable}[]{@{}lllll@{}}
\toprule
& Ag & Au & Zn & Hg\tabularnewline
\midrule
\endhead
D\textsubscript{0} (mm\textsuperscript{2} s\textsuperscript{-1}) &
40.000 & 10.700 & 13.000 & 0.011\tabularnewline
Qsd*10\textsuperscript{3} (J mol\textsuperscript{-1}) & 184.600 &
177.000 & 91.600 & 4.850\tabularnewline
\bottomrule
\end{longtable}

\textbf{Figure 1.} a) Phase diagrams of Li-M (M=Hg, Ag, Au and Zn,
respectively). The regions where Hg, Ag, Au and Zn dissolved are denoted
as (Li), \selectlanguage{greek}δ\selectlanguage{english}(Li), (Li) and \selectlanguage{greek}β\selectlanguage{english}(Li); b) a schematic of Li\textbar{}substrate
cell and the formation of Li-rich solid solution alloys upon Li
deposition; c) Li plating profiles of four cells at 2 mA
cm\textsuperscript{-2} and 5 mAh cm\textsuperscript{-2}.

\textbf{Figure 2.} Morphology and structure evolution with different Li
plating capacities at 2 mA cm\textsuperscript{-2}. a) The
cross-sectional SEM images of LiHg electrodes with areal capacity of
0.0, 2.3, 3.1, 5.0, 9.0 and 55.0 mAh cm\textsuperscript{-2}; b) the
electrochemical profiles and corresponding ex-situ XRD patterns with
controlled Li capacities; c) the schematic illustration of morphology
evolution of LiHg substrate upon Li deposition.

\textbf{Figure 3.} Composition analyses for the sample with a plating
capacity of 5 mAh cm\textsuperscript{-2}. a) The SEM image and
corresponding EDS mapping of Hg; b) EELS spectrum of Li signal for the
FIB sample; c, d) XPS spectra of Hg and Li of the FIB sample; e, f)
HAADF image and corresponding EDS mapping image from HR-TEM; g, h) the
low, high HAADF images and corresponding EDS mapping from the
Cs-corrected TEM model, where Hg agglomeration are clarified as bright
domains in the dark Li zones due to the super energy exposure of
Cs-corrected TEM and significantly different atomic weight of the two
elements.

\textbf{Figure 4.} a--c) The cross- and top-sectional SEM images and
corresponding EDS mapping images with Li deposition capacity of 0 mAh
cm\textsuperscript{-2} and 5 mAh cm\textsuperscript{-2}: a) Ag foil, b)
Au foil and c) Zn foil. d) The schematic diagram of the morphology
evolution from pristine electrode to the subsequent plating process for
Ag, Au and Zn.

\textbf{Figure 5.} a) The histogram of theoretical diffusion equal
distance \emph{R} and diffusion coefficient \emph{D} of Ag, Au, Zn and
Hg in the Li-rich solid solution phases; b) the schematic upon Li atoms
deposition on different substrate foils (Ag, Au, Zn foil and LiHg film).

\textbf{Figure 6.} The electrochemical performance of cells assembled
with Zn foil and LiHg film electrodes with a prelithiation capacity of 4
mAh cm\textsuperscript{-2}. a) Stripping/plating-time curves at 2 mA
cm\textsuperscript{-2} and 2 mAh cm\textsuperscript{-2}; b--d) Coulombic
efficiencies and corresponding stripping/plating curves at 2 mA
cm\textsuperscript{-2} and 2 mAh cm\textsuperscript{-2}; e--g) LiHg
film\textbar{}LFP and Zn foil\textbar{}LFP full cell performance: e)
cycling performance, f) and g) capacity-voltage curves at various
cycles.

\textbf{Hosted file}

\verb`Dynamic alloying interface_Figures.docx`  available at \url{https://authorea.com/users/581753/articles/622192-construction-of-dynamic-alloy-interface-for-uniform-li-deposition-in-li-metal-batteries}

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