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Cite this: DOI: 10.1039/d3ee04333a
Zinc iso-plating/stripping: toward a practical Zn
powder anode with ultra-long life over 5600 h†
Hongli Chen,
a
Wanyu Zhang,
a
Shan Yi,
a
Zhe Su,
a
Zhiqiang Zhao,
a
Yayun Zhang,
a
Bo Niu*
a
and Donghui Long *
ab
Zn powder with large-scale production and good tunability is promising for aqueous Zn-ion batteries,
but its extremely short lifespan seriously hinders the practical application. Herein, we disclose that Zn
powder anode failure is majorly caused by top-down plating and bottom-up stripping behaviors.
Therefore, an iso-plating/stripping strategy has to be developed accordingly to achieve an ultra-
long lifetime Zn powder anode for practical applications. Zincophilic Bi-metal nanosheets
areanchoredontheZnpowdersurface,whichcouldserveaspreferredZnnucleationsitesand
charge-aggregated protrusions, leading to homogeneous plating/stripping and gradient-free
Zn
2+
distribution throughout the powder electrode. Furthermore, Bi has additional advantages
including the ability to guide Zn(002)-orientated growth and suppress side reactions for achiev-
ing further structural stability, permitting unprecedented stable cycling of over 5600 h at 1 mA cm
2
and585hevenat15mAcm
2
. The corresponding Bi@Zn powder//MnO
2
full batteries feature
an extraordinary capacity retention of 82.12% after 1150 cycles at 2 A g
1
and a low negative/
positive electrode capacity ratio of 6.65. When applied in pouch-type batteries, Bi@Zn powder
delivers an impressive energy density of 138.6 W h kg
1
at a superfast power density of 700 W kg
1
.
This study clarifies the failure mechanism of the Zn powder anode and develops a concise yet
effective strategy that paves the way for fabricating practical Zn anodes with a long life and dendrite-
free structure.
Broader context
Aqueous zinc-ion batteries (AZIBs) are considered promising ‘‘beyond Li-ion’’ technologies for storing and maximizing intermittent renewable energy owing to
their inherent safety and environmentally friendly nature. More importantly, the Zn powder anode offers good adjustability and processability, which is
suitable for the traditional wet electrode process, endowing low cost and high battery-level energy density. Unfortunately, the extremely short lifespan of the Zn
powder anode hinders its practical application. Until now, its potential failure mechanisms and corresponding effective strategies have not been clearly
elucidated. In this work, we point out the structural collapse caused by top-down plating and bottom-up stripping behaviors, and correspondingly develop an
iso-plating/stripping strategy. Zincophilic Bi-metal nanosheets serve as preferred Zn nucleation sites and charge-aggregated protrusions to realize gradient-free
Zn
2+
distribution and homogeneous plating/stripping throughout the powder electrode. Thus, plating/stripping in the same location is achieved, leading to
structural integrity without dendrites and collapse. The Bi@Zn powder anode displays an ultra-long life of over 5600 h, a new record for all zinc powder anodes
reported to date. This study is an exemplary effort, and provides significant guidance for the design of advanced powder-based anodes with high stability and
long lifespan.
Introduction
Developing safe, cost-effective, and environmentally friendly
energy storage systems (ESSs) is vital for storing and maximizing
energy from widespread but intermittent renewable power.
1–3
The most widely used Li batteries, however, face alarming safety
hazards due to organic electrolyte flammability and short-circuit
overheating, as well as increasing cost concerns with limited
lithium resources.
4–6
Aqueous Zn-ion batteries (AZIBs) are con-
sidered promising candidates for the next generation of ESSs
a
State Key Laboratory of Chemical Engineering, East China University of Science
and Technology, Shanghai 200237, China. E-mail: longdh@mail.ecust.edu.cn
b
Key Laboratory of Specially Functional Polymeric Materials and Related
Technology, East China University of Science and Technology, Shanghai 200237,
China
†Electronic supplementary information (ESI) available. See DOI: https://doi.org/
10.1039/d3ee04333a
Received 13th December 2023,
Accepted 2nd April 2024
DOI: 10.1039/d3ee04333a
rsc.li/ees
Energy &
Environmental
Science
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owing to their inherent safety and environmentally friendly
nature.
7–9
Besides, their anode material, Zn metal, offers unique
advantages including high theoretical capacity (5855 mA h cm
3
;
820 mA h g
1
), low redox potential (0.762 V vs. the standard
hydrogen electrode), and low cost thanks to great Zn reserve
abundance (44 times Li).
10–12
Unfortunately, Zn anodes suffer
from uncontrolled dendrite growth and undesired parasitic
reactions, which seriously hinder the stability and durability of
AZIBs and their large-scale application in ESSs.
13–15
Zn foil anodes have been widely studied for AZIBs owing to
their convenience in experimental operation. And several stra-
tegies have been proposed to alleviate the critical problems of
Zn foil, including alloying of Zn,
16–18
separator functiona-
lization,
19–21
electrolyte optimization,
22–24
and surface
coating,
25–27
which contribute to promoted rapid Zn
2+
trans-
portation, even current density distribution, and decreased
water activity. Although the cycling performance of the Zn foil
anode has been improved, so far, it is still unable to overcome the
following inherent defects: (i) the spontaneous dendrite formation
along the vertical direction due to the 2D plane structure; (ii) poor
energy density because of redundantly thick Zn foil; (iii) techni-
cally difficult production of ultra-thin Zn foil; (iv) severe pulveriza-
tion of Zn foil at high current owing to its simultaneous use as a
working electrode and a current collector.
28–30
Zn powder shows potential for practical industrial produc-
tion over Zn foil due to its low cost, large-scale processability,
and good-tunability.
31–33
More importantly, the use of Zn
powder avoids the drawbacks of planar Zn foil and allows a
more well-controlled mass loading which is essential for the
anode vs. cathode mass balance and high battery-level energy
densities.
34–36
Furthermore, Zn powder, well-known as the
anode material of dry batteries, can be directly used in existing
electrode preparation techniques, such as the electrode paste-
casting method. Unfortunately, the cycle life of the bare Zn
powder anode has been reported to be less than 20 h at
1mAcm
2
, which is far shorter than that of pristine Zn foil
(50 h).
37–39
Until now, few studies have been reported on the
application and modification of Zn powder anodes, and in
particular, its potential failure mechanisms and corresponding
effective strategies have not been clearly elucidated.
Herein, we first disclose that the rapid failure of Zn powder
anodes is mainly attributed to electrode collapse caused by the
top-down plating and bottom-up stripping behaviors (Fig. 1a).
During the charging process, the outermost Zn powder has a
higher current density to attract Zn
2+
, so deposition occurs
mainly on the outside (Fig. S1 and Movie S1, ESI†). However,
the inevitable volume shrinkage originating from Zn dissolu-
tion during discharging mainly occurs on Zn powder close
to the current collector (Fig. S2a, b and Movie S2, ESI†). The
COMSOL simulations further verify inhomogeneous current
density distributions and significant Zn
2+
concentration gradi-
ents, which result in plating mainly on the outermost Zn
powder and stripping primarily on the innermost Zn powder
(Fig. S2c and d, ESI†). After several cycles, internal structural
collapse and surface dendritic growth occur, leading to over-
potential deterioration and Zn powder falling off (Fig. S3 and S4,
ESI†). This failure mechanism of Zn powder is completely differ-
entfromthatofZnfoil,whichistheconventionalshort-circuit
due to the dendrite growth (Fig. S5 and S6, ESI†).
In this regard, we develop a zincophilic metal guiding
iso-plating/stripping strategy to achieve a practical Zn powder
anode with an unprecedented lifetime of over 5600 h at
1mAcm
2
(Fig. 1b). The Bi-metal nanosheets with high Zn
2+
-
adsorption-ability are homogenously anchored on the Zn pow-
der surface, which could serve as preferred Zn nucleation sites
and regulate current density distribution. Thus, gradient-free
Zn
2+
distribution and homogeneous plating/stripping along
the powder electrode thickness direction are realized, allowing
for plating/stripping at the same position, which in turn
endows structural integrity without dendrites and collapses.
Fig. 1 Schematic illustration of the plating/stripping behavior of the (a) bare Zn powder anode and (b) Bi@Zn powder anode.
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Furthermore, Bi has additional advantages including the ability
to guide Zn(002)-orientated growth and suppress side reactions
for achieving further structural stability, permitting stable cycling
for585hevenatanultra-largecurrentdensityof15mAcm
2
and super-high Zn utilization of 45%. The corresponding
Bi@Zn powder//MnO
2
full batteries with a low negative/positive
electrode capacity (N/P) ratio of 6.65 feature an extraordi-
nary specific capacity of 365.9 mA h g
1
at 0.2 A g
1
and a
good capacity retention of 82.12% after 1150 cycles at 2 A g
1
.
When applied in pouch-type batteries, Bi@Zn powder deli-
vers an impressive energy density of 138.6 W h kg
1
at a
superfast power density of 700 W kg
1
. This study discloses
the failure mechanism of Zn powder anodes and develops
the corresponding strategy that paves the way for fabri-
cating long-lifespan Zn anode and the practical application
of AZIBs.
Fig. 2 The electrochemical stability of Bi@Zn powder. (a) Long-term galvanostatic cycling performance of Zn//Zn symmetric batteries for the bare Zn
powder and Bi@Zn powder tested at 1 mA cm
2
and 0.5 mA h cm
2
; the insets are detailed voltage profiles at different cycle time ranges. Morphology
evolution of (b)–(e) Bi@Zn powder anodes after different cycles at a current density of 1 mA cm
2
. (f) Rate performance and (g) cycling performance of
the symmetric batteries using the Bi@Zn powder anode at a current density of 15 mA cm
2
for a capacity of 7.5 mA h cm
2
. (h) Comparison of cycling
performance between this work and other previous reports on the Zn powder anode.
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Results and discussion
Characterization of Bi@Zn powder and enhanced
electrochemical stability
Zn powders are decorated with zincophilic Bi-metal nanosheets
by a spontaneous galvanic replacement reaction (3Zn + 2Bi
3+
-
3Zn
2+
+2Bi) through dipping bare Zn powders into 0.05 M
Bi(NO
3
)
3
solution (Fig. S10–S13, ESI†). As shown in Fig. S14–
S17 (ESI†), the nanosheets on the Bi@Zn powder surface are
mainly composed of Bi-metal with exposed (012) and (104)
planes, as evidenced by HRTEM and XRD. In addition, the
Bi@Zn powders show a strong Raman peak centered at
91.2 cm
1
and XPS signals at 164.2/158.9 eV, which are attrib-
uted to Bi–Bi bonds (Fig. S18 and S19, ESI†).
40–42
The above
results confirm that Bi-metal nanosheets are successfully
anchored on the Zn powder surface (Bi@Zn powder).
To evaluate the cycling performance of the Bi@Zn powder
anode, symmetric batteries are assembled and tested at a
current density of 1 mA cm
2
and a capacity density of
0.5 mA h cm
2
(Fig. 2a). Impressively, the Bi@Zn powder
batteries show remarkable cycling stability for more than
5600 h, 374 times higher than that of the bare Zn powder
batteries (15 h). To understand how the Bi-metal nanosheets
affect the Zn plating/stripping behavior, the surface morphol-
ogies of Bi@Zn powder anode after 5, 20, 200, and 5000 cycles
are further monitored using SEM images (Fig. 2b–e and
Fig. S25, ESI†). In the initial 5 cycles, the dense and neat Zn
deposits are observed on and between the spheroids of the
Bi@Zn powder anode (Fig. 2b). As the cycle proceeds, the
deposits are further filled in the interstitial spaces, leading
to the structural integrity and close electrical contact of the
Bi@Zn powder anode, in contrast to the bare Zn powder anode
(Fig. 2c–e). Notably, the new Zn on the cycled Bi@Zn powder
anode completely covers the metallic Bi nanosheets, showing a
completely different morphology from that the bare Zn powder
anode (Fig. S4 and S26–S27, ESI†). Such a striking contrast
verifies that the Bi-metal as a nucleation seed is capable of
changing the plating/stripping behavior and endowing struc-
tural integrity without dendrites and collapse.
The rate capability of the symmetric batteries is measured at
current densities ranging from 1 to 10 mA cm
2
with a fixed
capacity of 1 mA h cm
2
. In contrast to the rapid deterioration
of overpotentials in symmetric batteries using bare Zn powder
anodes, the Bi@Zn powder batteries are capable of stable
Fig. 3 Nucleation and growth evolution of Zn deposition. (a) The first Zn deposition voltage profiles of the bare Zn powder anode and Bi@Zn powder
anode at 1 mA cm
2
. Morphology evolution of the (b)–(e) bare Zn powder anode and (f)–(i) Bi@Zn powder anode with a plating capacity from
0.5 mA h cm
2
to 5 mA h cm
2
.
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reversible Zn plating/stripping with almost no voltage fluctua-
tion (Fig. 2f). For practical AZIBs, the depth of discharge (DOD)
is an extremely important metric since it determines how much
of the promised high energy density can be realized at the
device level.
43,44
At a high DOD of 45%, the symmetric batteries
of the Bi@Zn powder anode show a prolonged lifetime over
585 h (Fig. 2g and Fig. S29, ESI†). More surprisingly, the Bi@Zn
powder batteries also exhibit highly reversible plating/stripping
even under the harsh conditions, i.e., impressively a DOD
of 60% and an ultra-large current/capacity of 40 mA cm
2
/
10 mA h cm
2
(Fig. S30, ESI†). Furthermore, the symmetric
battery assembled with an antifreeze hydrogel as the electrolyte
can cycle steadily for 190 h at 20 1C, which proves that the
Bi@Zn powder anode has good low-temperature applicability
(Fig. S31, ESI†). Compared with the previously reported works,
our work has reached a new threshold to enable Zn powder
anode cycling continuously and stably for over 5600 h (Fig. 2h
and Table S1, ESI†). More importantly, the iso-plating/stripping
ensures the structural integrity of the Bi@Zn powder anode,
giving it the advantages of stable cycling at higher current
density and larger capacity density.
Study on nucleation and growth evolution of Zn deposition on
the Bi@Zn powder anode
To gain a better understanding of the change in the Zn
deposition behavior, the nucleation and subsequent growth
processes are specially analyzed in correlation with the evolu-
tion of the voltage profile. The symmetric batteries of Bi@Zn
powder exhibit a smaller nucleation overpotential of 35.6 mV
than that of bare Zn powder, indicating that the Bi-metal favors
the nucleation of Zn (Fig. 3a and Fig. S32, ESI†). The morphol-
ogies of the Zn deposits on the bare Zn powder anode at fixed
current densities of 1 mA cm
2
with a different deposition
amount of Zn from 0.5 to 5 mA h cm
2
are shown in Fig. 3b–e
and Fig. S33 (ESI†). On the topmost Zn powder, plenty of
vertical and loose flakes are observed, which gradually increase
in size as the amount of Zn deposited increases, and even form
‘‘dead zinc’’. Unexceptionally, the new Zn is preferentially
deposited on the already-formed thin flakes rather than on
the inner Zn powder, leaving the interior almost free of deposit.
In contrast, the Bi@Zn powder anode has no significant Zn
deposits and consequent growth in the outer region from 0.5 to
2mAhcm
2
, implying that part of the deposition occurs
Fig. 4 Zn deposition mechanism. (a) The calculated adsorption energy of the Zn atom on Zn and Bi. COMSOL simulation of (b) current density
distribution, (c) and (d) Zn
2+
concentration and morphology evolution of the Bi@Zn powder anode during plating. COMSOL simulation of (e) current
density distribution, (f) and (g) Zn
2+
concentration and morphology evolution of the bare powder anode during plating. (h) and (i) In situ optical
observation of Zn plating on the Bi@Zn powder anode at 5 mA cm
2
. (The thickness of the Bi@Zn powder anode is 200 mm.)
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internally (Fig. 3f–h). When the deposition capacity reaches
5mAhcm
2
, the Bi@Zn powder anode exhibits a dense and
coherent particle structure with an overall flat morphology
(Fig. 3i).
In order to explore the role of Bi-metal nanosheets in the
deposition process, the adsorption energies of Zn atoms (E
ads-
Zn
) on Zn and Bi are calculated using density functional theory
(DFT) calculations. According to the results, Zn
2+
is more
inclined to approach and adsorb onto Bi, suggesting that Bi
has better zincophilicity and can act as a nucleating agent to
guide Zn deposition inside the Bi@Zn powder anode (Fig. 4a
and Fig. S34, ESI†). To further reveal the Zn plating behavior of
the Bi@Zn powder anode, surface evolution, current density
distribution, and Zn
2+
concentration distribution are simulated
using COMSOL Multiphysics based on an established electro-
deposition model.
45
Since Bi-metal nanosheets are protrusions
on the surface of Bi@Zn powder, the structure is modeled as a
10 mm radius circle with six 1 mm radius circles (Fig. S8c, ESI†).
As exhibited in Fig. 4b, charges will heavily accumulate around
the protrusions, forming multiple high current density sites,
thereby promoting Zn
2+
internal diffusion. As deposition con-
tinues, there is no significant concentration gradient within the
Bi@Zn anode, ensuring Zn homogenous deposition throughout
the electrode (Fig. 4c, d and Fig. S35, ESI†), which is quite different
from that of the bare Zn anode (Fig. 4e, f and Fig. S36, ESI†). In situ
observation also verifies that zincophilic Bi-metal nanosheets
contribute to achieving homogeneous deposition along the anode
thickness direction (Fig. 4h, i and Movie S3, ESI†).
Fig. 5 Zn oriented deposition process. Morphology of the (a) bare Zn powder anode and (b) Bi@Zn powder anode with a plating capacity of 10 mA h cm
2
.
(c) The illustration of the hexagonal close packed structure of Zn. The atomic structures of multiple Zn atoms with (d) (100) and (e) (002) surfaces adsorbed
on the Bi material. (f) The calculated adsorption energy per Zn atom of the (002) surface and (100) surface on the Bi material. Operando evolution of the XRD
pattern of the (g) bare Zn powder anode and (h) Bi@Zn powder anode during cycling.
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It should be noted that Bi-metal not only promotes homo-
geneous deposition at the macro level but also induces Zn-
oriented deposition at the micro level. As shown in Fig. 5b and
Fig. S37 (ESI†), the Bi@Zn powder anode surface exhibits a Zn
(002) typical texture at 10 mA h cm
2
, unlike the bare Zn
powder anode. Based on the hexagonal close-packed structure
of Zn (Fig. 5c), it is speculated that Bi-metal acts as a nucleat-
ing agent to promote the deposition towards the horizon-
tal orientation of the (002) crystal plane, which can further
inhibit dendrite growth and side reactions.
46–49
The internal
mechanism of Zn oriented deposition is investigated in detail
using DFT calculations, which are used to calculate the adsorp-
tion energies (E
ads
) of Zn atoms forming (100)
Zn
and (002)
Zn
crystal planes on Bi. Comparing the atomic arrangement of Zn
nucleation on Bi, the lattice mismatch of (002)
Zn
is smaller than
that of the (100)
Zn
(Fig. 5d and e). Meanwhile, the (002) crystal
plane (0.93 eV) has lower E
ads
than the (100) crystal plane
(0.59 eV), indicating that Zn prefers to adsorb on Bi in an
array arrangement similar to the (002) crystal plane, and the
deposited Zn will grow in this direction (Fig. 5f). The process of
Fig. 6 Environmental stability and anti-side reaction of Bi@Zn powder. In situ optical observation of Zn deposited on the (a) bare Zn powder anode and
(b) Bi@Zn powder anode at 1 mA cm
2
. (The thickness of the bare Zn powder anode and Bi@Zn powder anode is 50 mm.) (c) Differential electrochemical
gas chromatography for the bare Zn powder and Bi@Zn powder symmetric batteries at 0.5 mA cm
2
. (d) LSV curves of bare Zn powder and Bi@Zn
powder in 1 M aqueous Na
2
SO
4
electrolyte at a scan rate of 1 mV s
1
. (e) The calculated adsorption free energy of H (DG
H*
) on the Zn and Bi. (f) Tafel
curves of bare Zn powder and Bi@Zn powder anodes in the conventional electrolyte (2 M ZnSO
4
+ 0.1 M MnSO
4
, pH = 4.55) at a scan rate of 1 mV s
1
.
SEM images of (g) bare Zn powder and (h) Bi@Zn powder after immersion in the conventional electrolyte for 1 day. (i) XRD patterns of the bare Zn powder
anode and Bi@Zn powder anode after 5 days of immersion in the conventional electrolyte.
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Fig. 7 The electrochemical performance of Zn//Ti asymmetry batteries and Zn//MnO
2
full batteries. (a) Coulombic efficiencies (CE) of Zn//Ti asymmetry
batteries using the bare Zn powder anode and Bi@Zn powder anode at 1 mA cm
2
for a capacity 1 mA h cm
2
. Cycling performance, and CE of the
Zn//MnO
2
full batteries using the bare Zn powder and Bi@Zn powder as the anode with a negative/positive electrode capacity (N/P) ratio of 6.65 at
(b) 0.2 A g
1
and (c) 2 A g
1
. (d) Rate performance of the Zn//MnO
2
full batteries using the bare Zn powder and Bi@Zn powder as the anode. (e) Self-
discharge tests of the Zn//MnO
2
full batteries using the Bi@Zn powder as the anode after a rest of 120 h. (f) Cycling performance, and CE of the Zn//MnO
2
full batteries using the Bi@Zn powder as the anode after two cycles for 120 h. (g) Cycling performance and optical image of the pouch-type Zn//MnO
2
full
battery using the Bi@Zn powder as the anode at 0.5 A g
1
. (h) Digital images of the pouch-type Zn//MnO
2
full batteries using the Bi@Zn powder anode at
different states. (i) Digital images of the pouch-type Zn//MnO
2
full batteries to light a LED indicator.
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Zn orientation deposition induced by Bi-metal nucleating
agents is further studied using an in situ XRD device (Fig. S38,
ESI†).
50
The I
(002)
/I
(100)
of the bare Zn powder anode decreases
for each deposition cycle, whereas that of the Bi@Zn powder
anode increases, suggesting that the presence of Bi-metal
promotes the Zn deposition in the (002) orientation (Fig. 5g,
h and Fig. S39, ESI†).
Environmental stability and anti-side reaction of the Bi@Zn
powder anode
The much-enlarged surface area of Zn powder poses a higher
risk of side reactions including the hydrogen evolution reaction
(HER) and corrosion (Fig. 6a and Movie S4, ESI†). Clearly,
the Bi@Zn powder anode has no bubbles during deposition,
indicating the inhibition of side reactions (Fig. 6b and
Movie S5, ESI†). Differential electrochemical mass spectrome-
try (DEMS) is used to quantitatively analyze the HER (Fig. S42,
ESI†). Compared with the obvious H
2
flux signal of the bare Zn
powder anode, using the Bi@Zn powder anode shows a negli-
gible H
2
flux signal during the cycle process, indicating that
the HER has been effectively inhibited (Fig. 6c). Linear sweep
voltammetry (LSV) curves are a routine characterization tool for
evaluating the HER on the electrodes (Fig. S43a, ESI†).
51
It is
difficult for the Bi@Zn powder anode to undergo the HER,
which has a much lower onset potential for the HER (1.772 V
at 10 mA cm
2
vs. SCE) compared to the bare Zn powder
anode (1.480 V at 10 mA cm
2
vs. SCE), as illustrated in
Fig. 6d. To further elucidate the origin of the inhibition of HER,
the free energy of DG
H*
is calculated to predict and evaluate
the HER activity (Fig. 6e and Fig. S44, ESI†). According to the
Sabatier principle, the greater the absolute value of DG
H*
, the
weaker the HER activity and the more difficult the H
2
genera-
tion. Therefore, the Bi has an HER inert feature, which is
completely consistent with experimental results of in situ DEMS
and LSV.
The corrosion resistance of the Bi@Zn powder anode is
verified using Tafel curves; it has a higher corrosion potential
and lower corrosion current than the bare Zn powder anode as
illustrated in Fig. 6f and Fig. S45 (ESI†). This result suggests
that the presence of Bi-metal can suppress corrosion and
provide good protection to the Zn powder anode.
52
Further-
more, the electrolyte immersion experiments could also con-
firm this finding (Fig. S43b, ESI†). The Bi@Zn powder anode
retains its original morphology without the formation of
Zn
4
SO
4
(OH)
6
4H
2
O (JCPDS No. 44-0673), in obvious contrast
to the bare Zn powder anode. (Fig. 6g–i and Fig. S46, ESI†).
Alternatively, immersion in water also shows that the Bi@Zn
powder anode is inert to corrosion (Fig. S47, ESI†). Based on the
above research results, it is demonstrated that the Bi@Zn
powder anode has excellent environmental stability and anti-
side reaction ability.
Electrochemical practicality of the Bi@Zn powder anode
Taking advantages of iso-plating/stripping, guided Zn(002)-
orientated growth and suppressed side reactions, the Bi@Zn
powder anode holds great potential for the development of
advanced energy storage systems. The Bi@Zn powder//Ti half
batteries delivered over 230 plating/stripping cycles with an
ultra-high average Coulombic efficiency (CE) of 99.99%, which
proves that the Bi@Zn powder anode has good reversibility
(Fig. 7a and Fig. S48, ESI†). Furthermore, Zn//MnO
2
full bat-
teries are assembled, in which the hydrothermally synthesized
a-MnO
2
nanofibers serve as the cathode (Fig. S49 and S50,
ESI†).
53
The negative/positive electrode capacity ratio is fixed to
a low value of 6.65, which could endow AZIBs with a higher
energy density.
54–56
As shown in Fig. 7b, c and Fig. S51–S54
(ESI†), the Bi@Zn powder//MnO
2
full batteries exhibit an ultra-
high specific capacity of 365.9 mA h g
1
at 0.2 A g
1
and an
impressive capacity retention of 82.12% after 1150 cycles at
2Ag
1
. Meanwhile, the Bi@Zn powder//MnO
2
full batteries
display a superior rate performance at different current
densities (Fig. 7d). Even at lower rates (e.g., 5–10 mA g
1
), the
batteries can maintain stable charge and discharge (Fig. S55
and S56, ESI†). The self-discharge behavior of the full batteries
is also disclosed; it could hold 89.3% of its original capacity
after a rest of 120 h. (Fig. 7e and Fig. S57, ESI†). In addition, the
batteries still have a high capacity and coulomb efficiency after
two cycles for 120 h (Fig. 7f).
The practicability of the Bi@Zn powder anode is demon-
strated via pouch-type Bi@Zn powder//MnO
2
full batteries with
large-area electrodes (4 8cm
2
) and high-mass loadings
(the Zn mass loading is 160 mg and the MnO
2
mass loading
is 64 mg). The pouch-type batteries display an impressively
high initial discharge capacity of 80.5 mA h g
1
and the
capacity remains at 99 mA h g
1
after 260 cycles at a super-
fast power density of 700 W kg
1
(Fig. 7g). This achieved
gravimetric energy density of 138.6 W h kg
1
is better than
those of commercial aqueous metal batteries such as Pb-acid
(30–40 W h kg
1
), Ni–Cd (50–70 W h kg
1
) and Ni–Zn
(60–100 W h kg
1
).
57
Furthermore, the Bi@Zn powder anode is utilized in the
construction of a flexible Zn–ion battery to explore its addi-
tional potential. The output voltage of this flexible battery is
1.399 V. Remarkably, even under twisting and bending condi-
tions, the voltage remains stable, as depicted in Fig. 7h. With
its high capacity and stable voltage, the pouch-type batteries
enable powering an LED display device (Fig. 7i). These results
confirm the advantage of the Bi@Zn powder anode, supporting
the merits of our zincophilic metal guiding iso-plating/strip-
ping strategy.
Conclusions
In summary, we developed a zincophilic metal guiding iso-
plating/stripping strategy aimed at overcoming the Zn powder
anode collapse caused by top-down plating and bottom-up
stripping behaviors. The effectiveness of this strategy is verified
by the replacement reaction to decorate Zn powder with zinco-
philic Bi-metal nanosheets (Bi@Zn powder). The Bi-metal nano-
sheets served as the preferred Zn nucleation sites to realize
homogeneous deposition throughout the powder electrode and
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thus simultaneously endowed structural integrity without den-
drites and collapse. Furthermore, Bi has additional advantages
including the ability to guide Zn(002)-orientated growth and
suppress side reactions. Therefore, an unprecedented life of over
5600 h and a super-high Zn utilization of 60% at high current
densities (40 mA cm
2
,10mAhcm
2
) were achieved. Compared
with the previously reported works, our work has reached a
new threshold to enable Zn powder anode cycling continuously
and stably for nearly 8 months. Meanwhile, the Bi@Zn powder//
MnO
2
full batteries exhibited a superb specific capacity of
365.9 mA h g
1
at 0.2 A g
1
and an impressive capacity retention
of 82.12% after 1150 cycles at 2 A g
1
with a low negative/positive
electrode capacity ratio of 6.65. The pouch-type batteries demon-
strated the commercialization potential of Bi@Zn powder. This
study clarified the failure mechanism of the Zn powder anode and
developed a concise yet effective strategy that paves the way for
fabricating practical Zn anodes with a long lifespan and dendrite-
free structure.
Author contributions
D. L. and B. N. supervised the project. H. C. conceived the idea,
designed the experiments, and performed materials synthesis,
electrochemical testing, and COMSOL simulations. H. C. and
W. Z. performed materials characterization (including in situ
observation, SEM, DEMS, etc.). S. Y. and Z. S. synthesized
MnO
2
. The manuscript was written by H. C. and revised by
other co-authors. All authors discussed the results and pro-
vided comments on the manuscript.
Conflicts of interest
There are no conflicts to declare.
Acknowledgements
This work was supported by the National Natural Science
Foundation of China (No. 22078100, No. 52102098, and
No. 22008073) and the Fundamental Research Funds for the
Central Universities (No. 222201718002). The authors would
like to thank Shiyanjia Lab (www.shiyanjia.com) for the
XRD tests.
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