Long-Life Room-Temperature Sodium–Sulfur Batteries by Virtue of Transition-Metal-Nanocluster–Sulfur Interactions

Article abstract of DOI:10.1002/anie.201811080

Room-temperature sodium–sulfur (RT-Na/S) batteries hold significant promise for large-scale application because of low cost of both sodium and sulfur. However, the dissolution of polysulfides into the electrolyte limits practical application. Now, the design and testing of a new class of sulfur hosts as transition-metal (Fe, Cu, and Ni) nanoclusters (ca. 1.2 nm) wreathed on hollow carbon nanospheres (S@M-HC) for RT-Na/S batteries is reported. A chemical couple between the metal nanoclusters and sulfur is hypothesized to assist in immobilization of sulfur and to enhance conductivity and activity. S@Fe-HC exhibited an unprecedented reversible capacity of 394 mAh g^?1 despite 1000 cycles at 100 mA g^?1, together with a rate capability of 220 mAh g^?1 at a high current density of 5 A g^?1. DFT calculations underscore that these metal nanoclusters serve as electrocatalysts to rapidly reduce Na₂S₄ into short-chain sulfides and thereby obviate the shuttle effect.

Full text of DOI:10.1002/anie.201811080

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Accepted Article
Title: Long-life room-temperature sodium-sulfur batteries by virtue of
transition metal nanocluster-sulfur interactions
Authors: binwei zhang, tian sheng, yunxiao wang, shulei chou,
Kenneth Davey, Shi-Xue Dou, and Shizhang Qiao
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To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201811080
Angew. Chem. 10.1002/ange.201811080
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10.1002/anie.201811080
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Long-life room-temperature sodium-sulfur batteries by virtue of
transition metal nanocluster-sulfur interactions
Bin-Wei Zhang,[a, b]† Tian Sheng,[c]† Yun-Xiao Wang,*[b] Shulei Chou,[b] Kenneth Davey,[a] Shi-Xue Dou[b]
and Shi-Zhang Qiao*[a, d]
[8]
Abstract: Room-temperature sodium-sulfur (RT-Na/S) batteries hold
significant promise for large-scale application because of low cost of
both sodium and sulfur. However, the dissolution of polysulfides into
the electrolyte limits practical application. Here, we report the design
and testing of a new class of sulfur hosts as transition metal (Fe, Cu,
and Ni) nanoclusters (~ 1.2 nm) wreathed on hollow carbon
nanospheres (S@M-HC) for RT-Na/S batteries. A chemical couple
between the metal nanoclusters and sulfur is hypothesized to assist
in immobilization of sulfur and to enhance conductivity and activity.
S@Fe-HC exhibited an unprecedented reversible capacity of 394
mAh g-1 despite 1000 cycles at 100 mA g-1, together with the a rate
capability of 220 mAh g-1 at a high current density of 5 A g-1.
Importantly, density functional theory calculations underscore that
these metal nanoclusters serve as electrocatalysts to rapidly reduce
Na2S4 into short-chain sulfides and thereby obviate the ‘shuttle
effect’. We conclude these novel S host cathodes will provide new
opportunities to construct electrode materials for various practical
battery technologies.
conducting polymer.
Although the carbon matrix used can
improve performance of RT-Na/S batteries, their nonpolar
character means they cannot effectively chemically interact with
polar sodium polysulfides. This results in capacity decay. An
improved rational design of cathode materials to inhibit
polysulfides dissolution is therefore urgently required for RT-
Na/S batteries.
S
hosts, with inherent polarization, are expected to
enhance reactivity of S and impede the shuttle effect. [9] These S
host cathodes with intrinsic sulfiphilic properties, such as metal
[9]
sulfides
and metal oxides [10], bind polysulfides and prevent
their dissolution into the electrolyte. These however have been
limited to TiO2, [11] Cu/CuSx, [12] Cu current foam
[13]
[14]
and SSe
for construction of intrinsic sulfiphilic hosts in RT-Na/S batteries.
Moreover, the interaction between the polar surface of S hosts
with polysulfides is limited, and sodium polysulfides remain
prone to dissolution into the electrolyte. Recently, a strategy was
established to circumvent this through reduction of polysulfides
into short-chain sulfides, and production of Na2S. This reduction
conversion can obviate dissolution of sodium polysulfides and
Room-temperature sodium-sulfur (RT-Na/S) batteries have
attracted significant attention due to the abundance, non-toxicity,
low cost and high theoretical capacity of sulfur (1672 mAh g-1). [1]
[15]
achieve, simultaneously, an improved capacity.
Transition
metal-based catalysts however have received significant
attention because of low cost and abundance and, generally,
However, RT-Na/S batteries present
a practical challenge
excellent catalytic performance across
a
range of
(widely known also to afflict Li-S batteries) of low reversible
capacity and rapid capacity fade. [2] The low accessible capacity
is caused by the insulating nature of sulfur and the sluggish
reactivity of sulfur with sodium. This results in an incomplete
reduction, rather than the complete production of Na2S. [3] The
dissolution of polysulfides into the electrolyte during cycling i.e.
the ‘shuttle effect’, is the key reason for rapid capacity fade. [4]
Recently, significant gains have been made in attempting
to solve these problems through novel S host materials,
including hollow carbon spheres, [5] interconnected mesoporous
[16]
electrochemical reduction reactions.
It was hypothesized that
the introduction of these metals into RT-Na/S batteries, to
reduce polysulfides to short-chain sulfides, might lower the
decomposition energy barrier of polysulfides. Additionally, that
transition metals such as Fe, Cu and Ni, would form a chemical
bond with S and significantly improve conductivity of an S
cathode. [14, 17]
Here, we report transition metal (M = Fe, Cu, and Ni)
nanoclusters loaded onto hollow carbon nanospheres (HC) as
new, polarized S hosts to improve the reactivity of S and to
inhibit the shuttle effect. These transition metal nanoclusters
enhance reactivity of S via chemical coupling. We show,
perhaps surprisingly, that the Fe nanocluster (~1.2 nm)
wreathed S host, S@Fe-HC, exhibits the greatest reversible
capacity of initially 1023 mAh g-1, and 394 mAh g-1 despite 1000
[6]
[7]
carbon hollow nanospheres,
carbon fibre cloth,
and
[a]
[b]
Mr. Bin-Wei Zhang, Dr. Kenneth Davey, Prof. Shi-Zhang Qiao
School of Chemical Engineering, The University of Adelaide,
Adelaide, South Australia 5005, Australia
E-mail: s.qiao@adelaide.edu.au
Mr. Bin-Wei Zhang, Dr. Yun-Xiao Wang, Dr. Shulei Chou, Prof.
Shi-Xue Dou
cycles
at
100 mA g-1. The role of these transition metal nanoclusters in
RT-Na/S batteries is explored using density functional theory
(DFT) calculations to underscore that metal nanoclusters serve
as electrocatalysts and reduce long-chain polysulfides to short-
chain sulfides and thereby prevent the shuttle effect.
Institute for Superconducting and Electronic Materials, Australian
Institute of Innovative Materials, University of Wollongong,
Innovation Campus, Squires Way, North Wollongong, New South
Wales 2500, Australia
E-mail: yunxiao@uow.edu.au
Transmission electron microscope (TEM) images of HC
revealed that these are homogeneous with a thickness of 5.1
nm (see Figure S1 in the Supporting Information). Metal (M = Fe,
Cu, and Ni) nanoclusters supported on HC (denoted as M-HC)
were successfully fabricated through controlled thermal
treatment. TEM images of M-HC demonstrated that the metal
nanoclusters had a uniform distribution, in which the average
diameter was 1.1 nm (Figure S2-S4). Melted sulfur was loaded
[c]
[d]
Prof. Tian Sheng
College of Chemistry and Materials Science, Anhui Normal
University, Wuhu, 241000, P. R. China
Prof. Shi-Zhang Qiao
School of Materials Science and Engineering, Tianjin University,
Tianjin 300072, P.R. China
† These authors contributed equally to this work.
Supporting information for this article is given via a link at the end
of the document.
o
into the M-HC through a facile melt-diffusion strategy at 155 C
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10.1002/anie.201811080
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for 12 h, then sealed in a quartz ampoule and kept at 200 oC for
2 h (S@M-HC). Atomic resolution, high-angle annular dark field
(HAADF) scanning transmission electron microscope (STEM)
images of S@Fe-HC demonstrated that the Fe-HC matrix all but
completely kept its morphology after S loading without any
aggregation on the HC of Fe nanoparticles and S (Figure 1). As
can be seen in Figure 1b and 1d, the Fe nanoclusters were
amorphous and well-dispersed on the HC, with an average size
of ~1.3 nm (Figure 1f). Interestingly, after loading S, the size of
Fe nanoclusters in S@Fe-HC increased about ~0.2 nm
compared with the Fe-HC matrix (Figure S2). This indicates that
S is chemically adsorbed on the Fe nanoclusters to form Fe-S
bonds. The element mapping and line-profile analysis of S@Fe-
HC demonstrated that the S is well-embedded in the carbon
shell and that the amorphous Fe nanoclusters are distributed on
the carbon shell (Figure 1c and 1e). It should be noted that the
amongst these M-S bonds. Inductively coupled plasma-optical
emission spectroscopy (ICP-OES) results reveal that the Fe, Cu,
and Ni content in S@Fe-HC, S@Cu-HC and S@Ni-HC are very
similar, with weight ratios of, respectively, 9.82, 9.56 and
9.23, %. This approximately equal metal nanocluster loading
makes for a reliable comparison of the results of TGA. X-ray
diffraction (XRD) patterns of S@Fe-HC, S@Cu-HC, S@Ni-HC
and S powder are shown as Figure 2b. The peaks in these four
samples reveal that the S is crystalline. The lack of typical XRD
peaks with Fe, Cu and Ni underscore the STEM results that
these metal nanoclusters are amorphous. X-ray photoelectron
spectroscopy (XPS) results are presented as Figure 2c, 2d and
Figure S9 and S10. The Fe 2p XPS spectrum of S@Fe-HC
could be separated into Fe0 (707.10 eV) and Fe2+ (712.30 eV).
The Fe0 state in S@Fe-HC highlights the amorphous phase of
the Fe nanoclusters. It is seen that the binding energy of Fe0
2p3/2 peak (707.1 eV) is right-shifted 0.1 eV compared with that
for pure Fe (707.0 eV). This implies the formation of Fe-S bonds
between Fe nanoclusters and S. To further prove this hypothesis,
the S 2p spectrum is presented as Figure 2d. The S 2p3/2 peak
of S@Fe-HC is at 163.90 eV, which is 0.10 eV left-shifted
compared with pure S (S 2p3/2,164.0 eV). This shift can explain
the enhancement of immobilization and reactivity of S through
formation of the Fe-S bonds. Interestingly, this phenomenon was
found also in S@Cu-HC and S@Ni-HC. The binding energies of
the Cu0 2p3/2 XPS peak and the Ni0 2p3/2 XPS are 932.8 eV and
852.8 eV, which both are right-shifted by 0.1 eV from those of
pure Cu (932.7 eV) and pure Ni (852.7 eV), whilst the S 2p3/2
peaks of S@Cu-HC and S@Ni-HC are both at 163.90 eV. This
implies that Cu nanoclusters and Ni nanoclusters also form Cu-S
and Ni-S bonds.
intensity of
S increases with increasing intensity of Fe,
suggesting that the presence of Fe nanoclusters immobilize S by
formation of Fe-S bonds. The HAADF-STEM images of S@Cu-
HC and S@Ni-HC demonstrate that these share a similar
structure with S@Fe-HC, where the average size of amorphous
Cu and Ni nanoclusters are 1.3 + 0.3 nm (Figure S6) and 1.2 +
0.3 nm (Figure S7), respectively. This approximately similar size
of the three cathode materials permits a reliable comparison of
results. Significantly, the size of the M nanoclusters in S@Cu-
HC and S@Ni-HC are meaningfully larger when compared to
counterparts without S loading (Figure S2 and Figure S3). This
indicates that these also form Cu-S and Ni-S bonds and that
these chemical bonds between metal nanoclusters and S are
able to chemically stabilize S and improve its conductivity. [15, 18]
S@Fe-HC
S@Cu-HC
S@Ni-HC
b
a100
S@Ni-HC
S@Fe-HC
~19%
~21%
80
~22%
~13%
S@Cu-HC
~8%
60
S@HC
40
10 20 30 40 50 60 70 80
150 300 450 600 750 900
Temperature / °C
2
q
/
degree
c
S@Fe-HC
Fe
d
S@Fe-HC
S
Fe0
2p1/2
Fe0
164.9 eV
163.9 eV
2p3/2
2p1/2
707.1 eV
2p3/2
Fe2+
2p1/2
Sulfate
Fe2+
712.3 eV
2p3/2
Figure
1 a-d, HAADF-STEM images and corresponding
elemental mapping images of S@Fe-HC. e, Line-profile analysis
as indicated in d. f, Histogram showing size distribution of Fe
nanoclusters based on a count of 200 nanoclusters.
730
720
710
700
170
165
160
Binding Energy / eV
Binding Energy / eV
Figure 2 a, Thermogravimetry of S@Fe-HC, S@Cu-HC and
S@Fe-HC. b, XRD patterns of S@Fe-HC, S@Cu-HC, S@Ni-HC,
and S@HC. c, S 2p and d, Fe 2p XPS spectra for S@Fe-HC.
The thermogravimetric analysis (TGA) of these three
samples indicates that the S content in S@Fe-HC, S@Cu-HC
and S@Ni-HC are, respectively, ~ 40, 35, and 30 % (Figure 2a).
The greatest S loading ratio with S@Fe-HC, shows that the
amorphous Fe nanoclusters are favourable for capture of S and
increases its loading. In particular, the amount of S in S@Fe-HC,
Cyclic voltammetry (CV) was measured to investigate the
sodiation/desodiation mechanism of S@M-HC (Figure 3a and
Figure S12). The S@Fe-HC cell presented four conspicuous
peaks at 1.92, 1.54, 1.40, and 0.8, V during the initial cathodic
o
measured through sublimation at high temperature (450 C), is
greatest at ~ 21%. This can be attributed to formation of the Fe-
S bonds. This means also that the Fe-S bond is strongest
scan. The greatest peak at 1.92
transformation of solid sulfur into dissolved liquid long-chain
V corresponds to the
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polysulfides (Na2Sx, 4 < x ≤ 8), whilst the second peak at 1.54 V
is attributed to added sodiation of Na2Sx to Na2S4. The peak at
1.40 V, Na2S4 implies further sodiation to short-chain sulfides
(Na2Sy, 1 < y ≤ 3) and the peak at 0.8 V corresponds to the final
Na2S product. These four pairs of peaks were highly
reproducible, suggesting good cycling stability of S@Fe-HC.
Interestingly, the greater-voltage peaks of S@Cu-HC (1.93 V)
and S@Ni-HC (1.94 V) are greater than that for S@Fe-HC
(Figure S12). This indicates for S@Fe-HC that the highest
energy is that dissociated from the Fe-S bonds. [17] This finding
suggests also that the chemical bond between Fe and S is
strongest, and results in better electrochemical performance of
S@Fe-HC. The discharge/charge profiles of the 1st, 2nd, and 3rd
cycles at 100 mA g-1 of S@Fe-HC, S@Cu-HC and S@Ni-HC
cathode materials are shown in Figure 3b and Figure S15. The
RT-Na/S@Fe-HC cell shows two, long plateaus during the first
discharge from 1.75 to 1.18 V, and from 1.18 to 0.8, V. This
high-voltage plateau is attributed to the transition from S to long-
chain polysulfides Na2Sx, whilst the low-voltage plateau is
attributed to the reduction of Na2Sx to short-chain sulfides Na2Sy.
The plateaus for S@Fe-HC are less well-defined than those for
S/Fe-HC (Figure S16), S@Cu-HC and S@Ni-HC. This less
defined plateau for S@Fe-HC likely originates from two main
causes. The first is the strong chemical bond formed by S and
Fe. This bond will affect the reaction of sulfur with sodium i.e.
differences in electrochemical performance was investigated
during the initial charge-discharge process by electrochemical
impedance spectra (EIS) (Figure 3e) that corresponds to the
fitted lines of Nyquist plots. The equivalent circuit (inset in Figure
3e) consists of the electrolyte resistance (Rs), interfacial
nanolayer resistance (Rsuf), charge transfer resistance (Rct), and
Warburg impedance (Wo). Rsuf is associated with the SEI film
and Rct with the kinetic resistance of charge transfer through the
electrode boundary. [20] The Rct values for S@Fe-HC, S@Cu-HC
and S@Ni-HC were 243.0, 276.2 and 434.9 ῼ, suggesting that
Fe nanoclusters enhance conductivity of S and decrease Rct.
3.0
a
S@Fe HC
1st
b
1.72 V
0.02
2.06 V
2nd
1.51 V
2.5
2.0
1.5
1.0
0.5
10th
50th
100th
200th
1.81 V
0.00
1.86 V
-0.02
-0.04
-0.06
1.47 V
S@Fe-HC
1st cycle
0.80 V
0.5
1.0
1.5
2.0
E / V
2.5
3.0
0
400 800 1200 1600 2000
Capacity (mAh g-1)
c
1000
800
600
400
200
0
S@Fe-HC
S@Cu-HC
S@Ni-HC
additional energy is needed to dissociate sulfur, and results in
[18]
the plateau being less defined than that for S/Fe-HC.
The
0
100
200
300
400
500
600
700
800
900 1000
Cycle number
second is that Fe nanoclusters serve as electrocatalysts to
rapidly reduce long-chain polysulfides into short-chain sulfides,
which results in the low-voltage plateau not apparent. The long
cycling-stabilities of S@Fe-HC, S@Cu-HC and S@Ni-HC
cathodes are shown over 1000 cycles at 0.1 A g-1 (Figure 3c).
The S@Fe-HC delivered an initial capacity of 1023 mAh g-1, and
an excellent reversible capacity of 394 mAh g-1 after 1000 cycles.
In contrast, the S@Cu-HC and S@Ni-HC cathodes delivered
initial capacities of 945 mAh g-1 and 783 mAh g-1, respectively,
and following > 1000 cycles, maintained 263 mAhg-1 and 201
mAh g-1. It should be noted that these cathode materials
displayed clear capacity decay over the first 50 cycles, due to
dissolution of long-chain polysulfides from the outer carbon-shell.
These cells all presented relatively stable cycling for the
following 1000 cycles. S@Fe-HC maintained the greatest
cycling stability. This likely originates from the ability of the
amorphous Fe nanoclusters to enhance reactivity of S by
formation of Fe-S bonds and impede dissolution of remaining
long-chain polysulfides. Significantly, S/Fe-HC displays rapid
capacity degradation. From an initial reversible capacity of
811ꢀmAꢀhꢀg−1 it degraded to 57ꢀmAꢀhꢀg−1 after only 25 cycles. This
rapid degradation of S/Fe-HC is due to the fact that the surface
of S does not chemical couple with Fe nanoclusters that can
quickly dissolve into the electrolyte. The rate-capacity tests of
S@M-HC were carried out at different current densities (Figure
3d). As is seen, when compared with S@Cu-HC and S@Ni-HC,
S@Fe-HC exhibited the greatest reversible capacity of ~ 820,
498, 383, 313, 269, and 220 mAh g-1, at 0.1, 0.2, 0.5, 1, 2 and 5
A g-1, respectively. Strikingly, when the current density was
returned to 0.1 A g-1, the capacity of RT-Na/S@Fe-HC was 534
mAh g-1, whilst that for S@Cu-HC was 370 mAh g-1 and that for
S@Ni-HC was 266 mAh g-1. The likely reason for these clear
1000
800
600
400
200
0
600
d
e
S@Fe-HC
S@Cu-HC
S@Ni-HC
S@Fe-HC
S@Cu-HC
S@Ni-HC
Fitting curves
400
200
0
0.1 Ah g-1
Rct
Rsuf
Csuf
Rs
W
Cdl
0
20
40
60
80
100
0
200 400 600 800 1000 1200
Cycle number
Z ' / W
Figure 3. a, Cyclic voltammograms, and b, discharge/charge
curves of S@Fe-HC at 100 mA g-1. c, cycle performance, d, rate
performance and e, Nyquist plots for S@Fe-HC, S@Cu-HC and
S@Ni-HC (inset in e: the equivalent circuit model).
To investigate the role of M nanoclusters in realistic RT-
Na/S batteries, ab initio molecular dynamics (AIMD) simulations
[21]
was preformed to reveal the decomposition of the Na2S4
following adsorption on Fe, Cu, and Ni nanoclusters/carbon.
Figure 4a-c presents the structural evolution of Na2S4 and Na2S2,
respectively, on metal nanoclusters as a function of AIMD
simulation time. These results reveal that Na2S4 decomposes
into Na2S2 on these nanoclusters. AIMD simulation results can
be used to estimate the interaction between Na2S4 and metal
nanoclusters and to gain understanding of the order of reactivity
for these metal nanoclusters (Figure 4d). The greater the
reactivity of a nanocluster, the greater the adsorption energy of
Na2S4 and the better performance in RT/Na-S batteries. The Fe
nanocluster is the most active in reaction with Na2S4, which
decomposed into Na2S2 in only 1 ps of the MD simulation. The
dissociative adsorption energy converged to -10.24 eV. For the
Cu nanocluster, after ~1 ps of MD simulation, the system
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stabilized where the adsorption energy was -7.76 eV. The Na2S4
decomposition on the Ni nanocluster was found to be
significantly slower than for the Fe and Cu nanoclusters. After ~
2.3 ps of MD simulation, the total energy converged to give a
value of the adsorption energy of -7.74 eV. It was observed that
Na2S4 decomposed most rapidly on the Fe nanocluster. This
observation highlights that the Fe nanocluster possessed the
most suitable reactivity for RT/Na-S batteries.
g-1 at a high current density of 5 A g-1. Our new findings show
that these metal nanoclusters serve as electrocatalysts to rapidly
reduce Na2S4 into short-chain sulfides and thereby obviate the
shuttle effect. These novel S host cathodes should prove to be
of practical benefit in the construction of electrode materials for a
range of battery technologies.
Acknowledgements
This research was supported by the Australian Research
Council (ARC) (FL170100154, DP160104866, DP170104464
and DE170100928), the Commonwealth of Australia, through
the Automotive Australia 2020 Cooperative Research Centre
(Auto CRC).
Keywords: Metal nanoclusters • novel S hosts •
electrocatalysts• shuttle effect• room temperature Na/S batteries
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adsorb polysulfides was evaluated by exposing Na2S4 to S@Fe-
HC, S@Cu-HC and S@Ni-HC (Figure S17). The Na2S4 solution
exhibited a peak for S42 at ~ 313 cm-1. [22] When the solution was
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exposed to S@Fe-HC this disappeared and another peak at ~
2- [1a]
252 cm-1 appeared. This finding is attributed to S2
.
For the
solutions exposed to S@Cu-HC and S@Ni-HC the intensity of
the S42- peak decreased, and the S22- peak evolved. This finding
suggests that part of Na2S4 are converted to Na2S2. These
findings indicated that S@Fe-HC gave the most efficient
confinement of the polysulfides and electrocatalytically
transformed these into short-chain sulfides – a finding consistent
with corresponding DFT results. The electrochemical
performance of the Fe/HC plain matrix is presented in Figures
S18 and S19 in which the capacity contribution can be seen to
be negligible for S@Fe-HC. Schematic illustrations of the M
nanocluster electrode mechanism are presented as Figure S20.
These M nanoclusters enhance the reactivity of S by formation
M-S chemical bonds and bind polysulfide dissolution, and then
catalyzed into short-chain sulfides.
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[12]
[13]
[14]
[15]
[16]
[17]
[18]
In conclusion, we have designed and tested a new class of
sulfur hosts as three transition metal (Fe, Cu, and Ni)
nanoclusters (~ 1.2 nm) wreathed on hollow carbon
[19]
[20]
nanospheres for RT-Na/S batteries, and hypothesized
a
chemical couple between the metal nanoclusters and sulfur that
assists in immobilization of sulfur and enhances conductivity and
activity. Of these, S@Fe-HC was found to exhibit an
unprecedented reversible capacity of 394 mAh g-1 despite 1000
cycles at 100 mA g-1, together with a rate capability of 220 mAh
[21]
[22]
This article is protected by copyright. All rights reserved.

10.1002/anie.201811080
Angewandte Chemie International Edition
COMMUNICATION
COMMUNICATION
Transition metal nanoclusters (~1.2
nm) wreathed on hollow carbon
nanospheres as novel S hosts were
applied to enhance conductivity and
activity of sulfur. These nanoclusters
chemisorb the resultant polysulfide
and electro-catalyze these into short-
chain sulphides, to achieve excellent
cycling stability and rate performance
for room-temperature sodium sulfur
batteries.
Bin-Wei Zhang, Tian Sheng, Yun-Xiao
Wang,* Shulei Chou, Kenneth Davey,
Shi-Xue Dou and Shi-Zhang Qiao*
Fe Cluster
Cu Cluster
Ni Cluster
-2
-4
S@Fe-HC
-6
-8
-10
-12
Page No. – Page No.
10 nm
0
1
2
3
4
5
MD time / ps
1000
800
600
400
200
0
Long-life room-temperature sodium-
S@Fe-HC
S@Cu-HC
S@Ni-HC
sulfur batteries
by virtue of
transition metal nanocluster-sulfur
interactions
0
100
200
300
400
500
600
700
800
900 1000
Cycle number
This article is protected by copyright. All rights reserved.