A family of polyoxometalate-resorcin[4]arene-based metal–organic materials: Assemblies, structures and lithium ion battery properties

Article abstract of DOI:10.1016/j.jallcom.2021.159009

Polyoxometalates (POMs) are alternative anode materials of lithium ion batteries (LIBs) for their reversible electrochemical redox behaviors and electron storage functions. To overcome the low conductivity and poor stability of the POMs, embedment of POMs into metal–organic hybrid complexes is a promising synthetic strategy. Here, we designed a family of copper-containing POM-resorcin[4]arene-based complexes supported by a resorcin[4]arene ligand (TPTR4A), copper cations and Keggin-type POMs, namely, [Cu₄(TPTR4A)₂][PMo₁₂O₄₀](OH)·2DMA·H₂O (1a), [Cu₄(TPTR4A)₂][SiW₁₂O₄₀]·2.5DMA (1b) and [Cu₄(TPTR4A)₂][PW₁₂O₄₀](OH)·0.5DMA·5H₂O (1c) (DMA = N,N’-dimethylacetamide). To improve the conductivity of the complexes, composites 1a@GO-1c@GO were obtained through mechanical grinding of the complexes and graphene oxide (GO). Strikingly, they show high initial specific capacity and stability for LIBs. This work offered a strategy for application of the POM-based complexes as LIBs via combining POM-based complexes and RGO.

Full text of DOI:10.1016/j.jallcom.2021.159009

Journal of Alloys and Compounds 868 (2021) 159009
Contents lists available at ScienceDirect
Journal of Alloys and Compounds
journal homepage: www.elsevier.com/locate/jalcom
A family of polyoxometalate-resorcin[4]arene-based metal–organic
materials: Assemblies, structures and lithium ion battery properties
Ming-Yue Yu1, Jin-Hua Liu1, Jin Yang⁎, Jian-Fang Ma⁎
Key Lab for Polyoxometalate Science, Department of Chemistry, Northeast Normal University, Changchun 130024, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Polyoxometalates (POMs) are alternative anode materials of lithium ion batteries (LIBs) for their reversible
electrochemical redox behaviors and electron storage functions. To overcome the low conductivity and poor
stability of the POMs, embedment of POMs into metal–organic hybrid complexes is a promising synthetic
strategy. Here, we designed a family of copper-containing POM-resorcin[4]arene-based complexes supported
by a resorcin[4]arene ligand (TPTR4A), copper cations and Keggin-type POMs, namely, [Cu4(TPTR4A)2]
Received 12 November 2020
Received in revised form 7 January 2021
Accepted 30 January 2021
Available online 10 February 2021
[PMo12O40](OH)·2DMA·H2O (1a), [Cu4(TPTR4A)2][SiW12O40]·2.5DMA (1b) and [Cu4(TPTR4A)2][PW12O40
]
Keywords:
(OH)·0.5DMA·5H2O (1c) (DMA = N,N’-dimethylacetamide). To improve the conductivity of the complexes,
composites 1a@GO-1c@GO were obtained through mechanical grinding of the complexes and graphene
oxide (GO). Strikingly, they show high initial specific capacity and stability for LIBs. This work offered a
strategy for application of the POM-based complexes as LIBs via combining POM-based complexes and RGO.
© 2021 Elsevier B.V. All rights reserved.
Polyoxometalate
Resorcin[4]arene
Crystal structure
Lithium-ion batteries
1. Introduction
groups are excellent candidate ligands for this purpose [38,39]. Thus,
the proper combination of POMs with calix[4]arenes will produce
Lithium ion batteries (LIBs) have gained considerable attention
owing to their potential application in energy storage systems [1–5].
In this aspect, traditional graphites, as the most common commer-
cial electrode materials, impede their development in LIBs due to the
limited theoretical capacity [6–10]. Thus, the exploration of new
electrode materials has become a hotspot for energy storage. Poly-
oxometalates (POMs), a class of nanoscale metal-oxo clusters, are
ideal candidates for anode materials of LIBs owing to their attractive
physical and chemical properties [11–17], including tunable com-
positions, electron storage functions and reversible electrochemical
redox behaviors [18,19]. Nevertheless, poor conductivity and in-
stability in electrolyte hinder their further development as anode
materials [20–23]. Self-assembly of POMs and proper substrates to
form POM-based hybrid complexes is a promising synthetic ap-
proach owing to the structural diversity and increased stability of
the resulting materials [15,20,24–31].
inorganic–organic complexes with tunable structures, high stability
and potential applications [40–42]. However, the examples that
POM-calixarene-based hybrid complexes applied in LIBs have been
rarely reported [5,43].
In this work, we synthesized a new resorcin[4]arene-based li-
gand with four chelating 4-(pyridin-2-yl)pyrimidine-2-thiolate
groups (TPTR4A) (Scheme 1). The multidentate TPTR4A ligand is
easy to chelate with metal ions to generate attractive structures and
improved stability of the obtained complexes [5,43]. In this work, a
family of stable POM-resorcin[4]arene-based complexes, namely,
[Cu4(TPTR4A)2][PMo12O40](OH)·2DMA·H2O (1a), [Cu4(TPTR4A)2]
[SiW12O40]·2.5DMA (1b) and [Cu4(TPTR4A)2][PW12O40](OH)·0.5D-
MA·5H2O (1c) (DMA = N,N’-dimethylacetamide), were achieved by
assembly of TPTR4A, copper cations and Keggin-type POMs. To im-
prove the conductivity and capacity of these complexes, such POM-
resorcin[4]arene-based materials were anchored to the surface of
reduced graphene oxide (RGO) through mechanical grinding of the
complexes and graphene oxide (Cu-POMs@GO, Scheme 2) [44–50].
As a consequence, the resulting composites show much better
electrochemical behaviors than the POM-resorcin[4]arene-based
complexes.
In this facet, functionalized calix[4]arenes are potential macro-
cyclic ligands for constructing inorganic–organic complexes [32–37].
Particularly, the functionalized calix[4]arenes with multi-chelating
⁎
Corresponding authors.
E-mail addresses: yangj808@nenu.edu.cn (J. Yang),
majf247@nenu.edu.cn (J.-F. Ma).
1
These authors contributed equally to this work.
https://doi.org/10.1016/j.jallcom.2021.159009
0925-8388/© 2021 Elsevier B.V. All rights reserved.

M.-Y. Yu, J.-H. Liu, J. Yang et al.
Journal of Alloys and Compounds 868 (2021) 159009
Scheme 1. Synthetic scheme of TPTR4A ligand.
Scheme 2. Synthetic route of 1a@GO.
2. Results and discussion
ball-milling of 1a–1c with GO, respectively. Powder X-ray diffraction
(PXRD) of each composite is consistent with the simulated one,
demonstrating that the mechanical grinding does not change the
structure of the Cu-POMs system (Fig. 3) [47,52,53]. FT-IR spectra of
1a–1c also correspond to those of 1a@GO-1c@GO. For example, both
1a and 1a@GO show the characteristic peaks at 1059, 962, 876 and
2.1. Structural description
SQUEEZE routine was used for removing the disordered solvents
in the refinement of the compounds [51]. The number of the solvents
was proved with thermogravimetric analysis (TG), electron diffrac-
tion density and elemental analysis (Fig. S1) [41]. The oxidation
states of molybdenum atoms, tungsten atoms, copper atoms in the
compounds were verified via X-ray photoelectron spectroscopy
(XPS) (Figs. S2–S6).
811 cm−1
[PMo12O40
, which are assigned to P-O and Mo-O vibrations of
3-
]
anions [40]. Besides, the characteristic peaks at 971,
922, 884 and 804 cm−1 for 1b/1b@GO and 1080, 977 and 891 cm−1
4-
for 1c/1c@GO correspond to [SiW12O40
]
(Si-O and W-O) and
3-
[PW12O40
]
(P-O and W-O), respectively [27,40]. The bands in the
range of 2973–1212 cm−1 for Cu-POMs and Cu-POMs@GO belong to
the characteristic peaks of ligand TPTR4A (Fig. S9). Particularly, the
characteristic peaks of functional groups from RGO were almost
covered by the sharp peaks of Cu-POMs after the Cu-POMs in-
corporation into RGO [54], demonstrating the successful preparation
of Cu-POMs@GO.
2.1.1. Structural description of (1a)–(1c)
Single-crystal XRD reveals that 1a–1c crystallized in the triclinic
system with space group P-1. The structures of 1b and 1c are similar to
4-
that of 1a except that the anions are replaced by [SiW12O40
]
and
3-
[PW12O40
]
anions, respectively, (Figs. 1, S7 and S8). In 1a, the
As illustrated in Fig. 4, N2 adsorption isotherms for 1a and
1a@GO were determined. For 1a, the Brunauer-Emmett-Teller (BET)
value is 57.998 m2 g−1 and the average pore diameter is 1.007 nm.
The corresponding ones of 1a@GO were enhanced to 169.551 m2 g−1
and 3.385 nm, respectively [55,56]. The result may account for Cu-
POM incorporation into RGO, which increased contact areas be-
tween the electrolyte and the composite. Similarly, for 1b@GO and
asymmetric unit contains one TPTR4A ligand, two Cu(I) cations, half of
3-
a [PMo12O40
]
anion, and half of a free OH- anion. Two Cu(I) cations
(Cu1 and Cu2) adopt the same four-coordinated mode: each Cu(I)
cation is coordinated with four N atoms (N1, N3, N10 and N12 for Cu1;
N4, N6, N7 and N9 for Cu2) (Fig. 2a). The Cu(I)-N distances are in the
range of 1.975(7)–2.063(7) Å (Table S1). Two [Cu2(TPTR4A)]2+ units are
3-
linked by a [PMo12O40
]
anion to form a [Cu4(TPTR4A)2(PMo12O40)]+
1c@GO, the BET surface areas are 115.559 and 124.367 m2 g−1
,
unit via the weak C–H···O hydrogen bonds (Fig. 2b). Further, adjacent
[Cu4(TPTR4A)2(PMo12O40)]+ units were linked via C–H···O interactions
to form 1D supramolecular chains (Table S2), as shown in Fig. 2c and d.
respectively (Fig. S10).
Scanning electron microscope (SEM) and transmission electron
microscopy (TEM) images of Cu-POMs and Cu-POMs@GO are illu-
strated in Fig. 5. It is clear that complexes Cu-POMs are visible with a
crystalline phase of diamond-shaped lamellar crystals (Fig. 5a–c).
The species of Cu-POMs are well-dispersed on RGO based on the
SEMs and TEMs of Cu-POMs@GO (Fig. 5d–i). The result further de-
monstrated the successful combination of RGO and Cu-POMs after
ball milling, which may account for the improvement of the
2.2. Physical characterization
POM-resorcin[4]arene-based complexes 1a–1c are stable in
electrolyte (Fig. 3a–c). Evidently, POMs with redox behaviors act as a
key role in stabilizing the structures of complexes during their
construction. The composites of 1a@GO-1c@GO were obtained by
2

M.-Y. Yu, J.-H. Liu, J. Yang et al.
Journal of Alloys and Compounds 868 (2021) 159009
Fig. 1. Schematic representation of the synthetic strategy for 1a–1c.
conductivity of the resulting composites. Obviously, the reduced
sizes were achieved after ball milling (Fig. S11), resulting in the
enlarged BET surface areas and exposed active sites. Thus, it is easy
for Li+ to contact with active sites. The mapping analysis of each
element was collected from the designated area (Figs. 6, S12 and S13,
revealing that the uniform distribution of these elements within
composites Cu-POMs@GO.
was explored as electrode materials for LIBs. As shown in Fig. 7, the
cyclic voltammogram (CV) curves of Cu-POMs and Cu-POMs@GO
were recorded from 0.01 to 3 V. For these materials, the irreversible
reduction peak was observed between 0.6 and 0.8 V in the first cycle,
which was from the production of the solid electrolyte interphase
(SEI) film and the electrolyte decomposition [57,58]. The reduction
peaks at ~1.6 V for Cu-POMs and ~1.7 V for Cu-POMs@GO may be
ascribed to the first process of the inserting Li+ ions [59,60]. In addi-
tion, for 1a@GO, a pair of reversible redox peaks were observed at
1.42 V (the oxidation) and 1.30 V (the reduction) in the first cycle,
demonstrating a defined electrochemical process, which accounted
for the reduction and oxidation of Mo6+ [5,46]. Meanwhile, the
2.3. Electrochemical performance
Inspired by the outstanding electrochemical behaviors of the
POM-based materials, the potential application of 1a@GO-1c@GO
Fig. 2. (a) Coordination environments of Cu(I) cations in 1a. (b) View of the [Cu4(TPTR4A)2(PMo12O40)]+ unit formed with the weak C–H···O interactions. (c) and (d) view of the
supramolecular chains formed by the weak C–H···O interactions.
3

M.-Y. Yu, J.-H. Liu, J. Yang et al.
Journal of Alloys and Compounds 868 (2021) 159009
Fig. 3. PXRD patterns of 1a–1c for the simulated, the as-synthesized, the sample soaked in electrolyte and the ones combined with GO (a–c). FT-IR spectra for the as-synthesized
1a–1c and the combined with GO (d–f).
reversible redox peak pairs were also found for 1b@GO and 1c@GO,
respectively, which may be attributed to the reduction and oxidation
of W6+ [12]. Noticeably, the subsequent CV curves were almost over-
lapped, revealing the good electrochemical stability of Cu-POMs@GO
composites. Moreover, the CV curves of Cu-POMs@GO were similar
to those of Cu-POMs, demonstrating that the electrochemical
mechanism is not changed.
As illustrated in Fig. S14, the initial discharge/charge capacities of
1a–1c were only 812/220, 1066/236 and 592/154 mA h g−1, respec-
tively. By contrast, 1a@GO-1c@GO displayed the initial discharge/
charge capacities of 1506/862, 1771/1035 and 1380/798 mA h g−1, re-
spectively. The corresponding coulombic efficiencies (CE) are 57%, 58%
and 58%, respectively. Clearly, these CE values were much higher than
those of 1a (27%), 1b (22%) and 1c (26%) (Fig. 8). The obvious capacity
loss for these materials was probably ascribed to the generation of the
SEI films [52,58,61]. At the same time, the galvanostatic charge-dis-
charge (GCD) curves were overlapped for the second and the third
cycles, indicating the good recycling stability. In addition, these ma-
terials displayed obvious plateaus. For example, the GCD curves of
1a@GO showed three plateaus at 1.67, 1.33 and 0.75 V, which corre-
sponded to the results of CVs. Particularly, Cu-POMs@GO composites
exhibited much higher reversible capacities than those of Cu-POMs in
the whole recycling process, in which the high reversible discharge
capacities (836, 947 and 888 mA h g−1 for 1a@GO-1c@GO, respec-
tively) with the high CE of 99% were achieved after 100 cycles (Fig. 8).
In view of the remarkable electrochemical performance of the
Cu-POMs@GO composites at 0.1 A g−1, the recycling stability and
practical applications of the composites were further investigated at
Fig. 4. N2 adsorption isotherms (a) and pore size distributions (b) for 1a@GO and 1a.
4

M.-Y. Yu, J.-H. Liu, J. Yang et al.
Journal of Alloys and Compounds 868 (2021) 159009
Fig. 5. SEMs of 1a–1c (a–c), 1a@GO-1c@GO (d–f) and TEMs of 1a@GO-1c@GO (g–i), respectively.
0.1–5 A g−1 (Fig. 9, Table S3). For instance, the discharge capacities for
1a@GO were ca. 805, 756, 698, 626, 596, 496, 376 and 326 mA h g−1
at 0.1–5 A g−1, respectively (Fig. 9a). The capacity (840 mA h g−1) was
still retained at 0.1 A g−1, verifying the composite possessed high
stability. Remarkably, compared with 1a, 1a@GO possessed the su-
perior rate performance, demonstrating that RGO acted as a key role
in improving the conductivity of the resulting composites [44–50].
Evidently, the discharge capacity of 1a@GO was better than the
known CPR/rGO composites (790 mA h g−1) at 0.1 A g−1 [62]. The
electrochemical performance of 1a@GO was compared to other
POM-based materials (Table S4). In addition, electrochemical
impedance spectroscopies (EISs) were determined to discuss the
electrochemical processes of these electrodes. R1 represented the
electrodes and electrolyte resistance. The Nyquist plots of compo-
sites Cu-POMs@GO showed smaller semicircles at high-frequency
region than those Cu-POMs (Fig. 9d–f), indicating that the
Cu-POMs@GO electrodes possessed the low internal resistance
(R2 and R3) [63]. Meanwhile, the large slopes were observed for
Cu-POMs@GO in the region of the low frequency, which showed the
low ion diffusion resistance (Wo). The result revealed that the
Fig. 6. Elemental mapping images of 1a@GO.
5

M.-Y. Yu, J.-H. Liu, J. Yang et al.
Journal of Alloys and Compounds 868 (2021) 159009
Fig. 7. CV curves of 1a–1c (a–c) and 1a@GO-1c@GO (d–f) at 0.01–3 V.
combination of Cu-POMs and RGO not only resulted in fast charge
transfer and Li+ migration, but also highly improved the electro-
chemical properties of the resulting composites.
(284.5 eV) (Fig. 11b) [64,65]. After discharge at 0.01 V, the C=O peak
became clear because of the intercalation of Li+ and the formation of
SEI films (the main composite was Li2CO3) (Fig. 11e) [20]. The similar
phenomenon was also observed for 1b and 1c (Figs. S2e and S3e). In
addition, the Mo 3d spectrum of 1a before test showed two main
peaks at the banding energy of 232.0 eV and 235.1 eV, corresponding
to MoVI3d5/2 and MoVI3d3/2 (Fig. 11c) [18]. After discharge at 0.01 V,
part of MoVI was reduced to MoV due to the appearance of MoV peaks
at 231.4 eV and 234.7 eV (Fig. 11f) [66,67]. Meanwhile, in respect to
the original WVI oxidation state, the XPS signals of partially reduced
WV appeared at 35.1 eV (W 4f7/2) and 37.2 eV (W 4f7/2) for 1b, and at
35.1 eV (W 4f7/2) and 37.3 eV (W 4f7/2) for 1c, respectively, after
discharge at 0.01 V (Figs. S2f and S3f) [68]. The result further proved
that the redox reactions occurred in lithium-ion batteries. Moreover,
Cu 2p spectrum of 1a possessed two main peaks of Cu 2p3/2
(931.8 eV) and Cu 2p1/2 (951.7 eV), demonstrating the presence of
Cu+ (Fig. S17a) [69]. Also, there existed two peaks at 933.4 eV and
953.6 eV, which may be assigned to Cu2+ 2p3/2 and Cu2+ 2p1/2 derived
from the oxidation of Cu+ by O2 in air, respectively [69,70]. The ratios
of Cu+/Cu2+ of 1a–1c were almost unchanged after discharge, de-
monstrating that copper did not participate in the electrochemical
Moreover, the 1a@GO//NCM111-1c@GO//NCM111 full-cells were
assembled to evaluate the practical applications of these materials
(Figs. S15 and S16). Fig. 10a showed the GCD curves of NCM111 and
1a@GO at 100 mA g−1 in the half cell. The GCD curves of the 1a@GO//
NCM111 full-cell from 1.2 to 4.5 V were depicted in Fig. 10b. The
charge and discharge capacities for the first cycle were 203 and
165 mA h g−1, respectively, and the initial CE value was up to 81.3%.
For the cycling performance, a high discharge capacity of 92 mA h g−1
was achieved at 100 mA g−1 (Fig. 10c), and the capacity retention
reached to 55.8% after 100 cycles.
To further evaluated the reaction mechanism of LIBs, the che-
mical composition and element valence of Cu-POMs before and after
discharge at 0.01 V were measured with the XPS measurements
(Figs. 11, S2 and S3). As illustrated in Fig. 11a, 1a contained C, N, O, S,
P, Mo and Cu elements, and 1b and 1c possessed C, N, O, S, Si, W, Cu
elements and C, N, O, S, P, W, Cu elements, respectively (Figs. S2a and
S3a). For the C 1s spectrum of 1a, there exist four peaks associated
with C=O (288.4 eV), C–O (286.8 eV), C–N (285.5 eV) and C–C
6

M.-Y. Yu, J.-H. Liu, J. Yang et al.
Journal of Alloys and Compounds 868 (2021) 159009
Fig. 8. GCD curves of 1a@GO-1c@GO (a–c) from 0.01 to 3 V. Cycling capacity and CE of 1a–1c and 1a@GO-1c@GO (d–f) at 0.1 A g−1
.
reactions (Fig. S17d). Ex-situ PXRD patterns of 1a–1c after the first
cycle were determined to explore the impressive reversibility. The
results showed that the peak intensities of 1a–1c reduced after the
insertion of lithium ions, indicating that the crystallization of 1a–1c
became weak [12]. Nevertheless, the structures of 1a–1c could still
retain after the first cycle (recharged to 3.0 V), indicating that these
materials could endure the volume variation with structural in-
tegrity after undergoing the redox reaction (Fig. 12), which ensured
the excellent capacity retention.
In view of the results of XPS and ex-situ XRD, the electrochemical
redox process mainly occurred on the Mo and W species in POMs,
and these materials can endure the volume variation with structural
integrity after undergoing the redox reaction. The results established
a specific lithium storage mechanism for the Cu-POMs@GO com-
posites.
Based on our experiments and the XPS results, the possible
reason for the enhanced electrochemical performance of Cu-
POMs@GO composites was discussed. In this respect, the Li+ storage
mechanism of Cu-POMs@GO composites may account for the sy-
nergistic effects of Cu-POMs and RGO. First, the combination of re-
sorcin[4]arene and POMs improved the stability of Cu-POMs
[35–37], thus affording a prerequisite for their application as anode
materials of LIBs. Second, the high density of the exposed O sites on
POMs led to the increased Li+ storage capacity [15]. The valence
changes of Mo and W (from Mo6+ to Mo5+ and from W6+ to W5+
)
calculated with XPS confirms that the redox reactions occurred be-
tween POMs and Li+ after discharge at 0.01 V [67]. Third, the un-
coordinated N atoms from ligand TPTR4A in Cu-POMs maybe
capture the Li+ ions and participate in Li insertion, which was in
favor of storing Li+ ions and generating excellent electrochemical
performance [20]. Finally, the combination with RGO not only im-
proved the conductivity of Cu-POMs, but also made full use of the
advantage of the small sizes and large surface areas of the resulting
composites, thus realizing to full contact with electrolyte [44–50].
To certify whether the capacity is dominated by the capacitive
behaviors or not, the CVs of Cu-POMs@GO with different scan rates
(0.1–5 mV/s) were recorded from 0.01 to 3.0 V (Figs. 13a, S18a and
S19a). Further, the power law i = avb was used to explore the elec-
trode reaction types (i, v, a and b are the peak current, scan rate and
alterable parameters, respectively). Generally, the b value of 0.5 re-
veals a diffusion-controlled process, whereas the b value of 1 means
the reaction being capacitive-controlled [20]. For 1a@GO-1c@GO,
the b values for anodic peaks were 0.77, 0.78, and 0.81, respectively,
demonstrating that their electrochemical behaviors are mainly ca-
pacitive process (Figs. 13b, S18b and S19b). Based on i = k1ν + k2ν0.5
(k1 and k2 represented the surface capacitive- and diffusion-con-
trolled contributions, respectively) [46], 66%, 72% and 77% of the
capacitance-contributions at 5 mV/s were achieved for 1a@GO-
7

M.-Y. Yu, J.-H. Liu, J. Yang et al.
Journal of Alloys and Compounds 868 (2021) 159009
Fig. 9. Rate capability comparison of 1a–1c and 1a@GO-1c@GO (a–c) at 0.1 A g−1 and 5 A g−1. EIS plots of 1a–1c and 1a@GO-1c@GO (d–f) anodes.
Fig. 10. Electrochemical performance of the 1a@GO//NCM111 full-cell. (a) Charge-discharge curves of NCM111 and 1a@GO in the Li+ half cells at 100 mA g−1. (b) Charge-discharge
curves of the 1a@GO//NCM111 full-cell at 100 mA g−1. (c) Cycling performance for 1a@GO//NCM111 full-cell.
8

M.-Y. Yu, J.-H. Liu, J. Yang et al.
Journal of Alloys and Compounds 868 (2021) 159009
Fig. 11. XPS analysis of 1a before test and after discharge at 0.01 V. (a) Survey XPS spectrum, (b) high-resolution XPS spectra of C 1s, (c) Mo 3d for the as-synthesized sample, (d)
survey XPS spectrum after discharge at 0.01 V for 1a, (e) high-resolution XPS spectra of C 1s and (f) Mo 3d.
Fig. 12. Ex-situ PXRD patterns of 1a–1c for the simulated, the as-synthesized, the discharged to 1.3 V or 1.35 V, and the recharged to 3.0 V.
9

M.-Y. Yu, J.-H. Liu, J. Yang et al.
Journal of Alloys and Compounds 868 (2021) 159009
Fig. 13. (a) CV profiles of 1a@GO with different scan rates (0.1–5 mV/s). (b) Cathodic peak plot of 1a@GO from log (ip) to log (v). (c) Capacitance contribution for 1a@GO (scan rate:
5 mV/s). (d) Capacitance contribution for 1a@GO with different scan rates (0.1–5 mV/s).
1c@GO, respectively (Figs. 13c, S18c and S19c), enhanced by 46%
Appendix A. Supporting information
relative to the ones at 0.1 mV/s (Fig. 13d, S18d and S19d).
Supplementary data associated with this article can be found in
the online version at doi:10.1016/j.jallcom.2021.159009.
3. Conclusions
References
We have designed a series of stable POM-resorcin[4]arene-based
metal–organic complexes with different Keggin-type POMs. Through
the ball-milling synthetic method, the redox Cu-POMs complexes
were successfully incorporated into the conductive RGO to give Cu-
POMs@GO composites. Significantly, the obtained Cu-POMs@GO
composites exhibit remarkable electrochemical performance as
anode materials of LIBs. This work presented a feasible synthetic
strategy for constructing Cu-POMs and Cu-POMs@GO. The sig-
nificant improvement of the electrochemical performance for the
resulting Cu-POMs@GO composites provide the meaningful gui-
dance for the application of POM-based metal–organic complexes as
anode materials of LIBs.
[1] N. Chen, Y. Dai, Y. Xing, L. Wang, C. Guo, R. Chen, S. Guo, F. Wu, Biomimetic ant-
nest ionogel electrolyte boosts the performance of dendrite-free lithium bat-
teries, Energy Environ. Sci. 10 (2017) 1660–1667.
[2] X. Zhang, Y. Yang, Z. Zhou, Towards practical lithium-metal anodes, Chem. Soc.
Rev. 49 (2020) 3040–3071.
[3] Q. Huang, K. Turcheniuk, X. Ren, A. Magasinski, A.-Y. Song, Y. Xiao, D. Kim,
G. Yushin, Cycle stability of conversion-type iron fluoride lithium battery
cathode at elevated temperatures in polymer electrolyte composites, Nat. Mater.
18 (2019) 1343–1349.
[4] F. Wu, V. Srot, S. Chen, S. Lorger, P.A. van Aken, J. Maier, Y. Yu, 3D honeycomb
architecture enables a high-rate and long-life iron (III) fluoride-lithium battery,
Adv. Mater. 31 (2019) 1905146.
[5] X.-Y. Yang, T. Wei, J.-S. Li, N. Sheng, P.-P. Zhu, J.-Q. Sha, T. Wang, Y.-Q. Lan,
Polyoxometalate-incorporated metallapillararene/metallacalixarene metal-or-
ganic frameworks as anode materials for lithium ion batteries, Inorg. Chem. 56
(2017) 8311–8318.
[6] Z. Zheng, H.-H. Wu, H. Liu, Q. Zhang, X. He, S. Yu, V. Petrova, J. Feng, R. Kostecki,
P. Liu, D.-L. Peng, M. Liu, M.-S. Wang, Achieving fast and durable lithium storage
through amorphous FeP nanoparticles encapsulated in ultrathin 3D P-doped
porous carbon nanosheets, ACS Nano 14 (2020) 9545–9561.
CRediT authorship contribution statement
This work was completed through contributions of all authors.
[7] J. Xu, J. Mahmood, Y. Dou, S. Dou, F. Li, L. Dai, J.-B. Baek, 2D frameworks of C2N
and C3N as new anode materials for lithium-ion batteries, Adv. Mater. 29 (2017)
1702007.
[8] Y.-T. Weng, H.-W. Liu, A. Pei, F. Shi, H. Wang, C.-Y. Lin, S.-S. Huang, L.-Y. Su, J.-
P. Hsu, C.-C. Fang, Y. Cui, N.-L. Wu, An ultrathin ionomer interphase for high
efficiency lithium anode in carbonate based electrolyte, Nat. Commun. 10 (2019)
5824.
[9] C. Xu, Z. Liu, T. Wei, L. Sheng, L. Zhang, L. Chen, Q. Zhou, Z. Jiang, L. Wang, Z. Fan,
Mesoporous single-crystalline MnOx nanofibers@graphene for ultra-high rate
Declaration of Competing Interest
The authors declare that they have no known competing fi-
nancial interests or personal relationships that could have appeared
to influence the work reported in this paper.
and long-life lithium-ion battery anodes, J. Mater. Chem.
24756–24766.
A 6 (2018)
[10] Y. Luo, D. Huang, C. Liang, P. Wang, K. Han, B. Wu, F. Cao, L. Mai, H. Chen, Fe2VO4
hierarchical porous microparticles prepared via a facile surface solvation treat-
ment for high-performance lithium and sodium storage, Small 15 (2019)
1804706.
Acknowledgments
[11] J. Hua, F. Jia, Y.-F. Song, Engineering high-performance polyoxometalate/PANI/
MWNTs nanocomposite anode materials for lithium ion batteries, Chem. Eng. J.
326 (2017) 273–280.
This work was financially supported by the National Natural
Science Foundation of China (Grant 21471029).
10

M.-Y. Yu, J.-H. Liu, J. Yang et al.
Journal of Alloys and Compounds 868 (2021) 159009
[38] T.-T. Guo, D.-M. Cheng, J. Yang, X. Xu, J.-F. Ma, Calix[4]resorcinarene-based [Co16
[12] K. Sun, H. Li, H. Ye, F. Jiang, H. Zhu, J. Yin, 3D-structured polyoxometalate mi-
crocrystals with enhanced rate capability and cycle stability for lithium-ion
storage, ACS Appl. Mater. Interfaces 10 (2018) 18657–18664.
]
coordination cages mediated by isomorphous auxiliary ligands for enhanced
proton conduction, Chem. Commun. 55 (2019) 6277–6280.
[13] H. Ilbeygi, I.Y. Kim, M.G. Kim, W. Cha, P.S.M. Kumar, D.-H. Park, A. Vinu, Highly
crystalline mesoporous phosphotungstic acid: a high performance electrode
material for energy storage applications, Angew. Chem. Int. Ed. 58 (2019)
10849–10854.
[14] J.-H. Liu, M.-Y. Yu, J. Yang, Y.-Y. Liu, J.-F. Ma, Polyoxometalate-based complex/
graphene for high-rate lithium-ion batteries, Microporous Mesoporous Mater.
310 (2021) 110666.
[39] T.-T. Guo, X.-F. Su, X. Xu, J. Yang, L.-K. Yan, J.-F. Ma, A calix[4]resorcinarene-based
[Co12] coordination cage for highly efficient cycloaddition of CO2 to epoxides,
Inorg. Chem. 58 (2019) 16518–16523.
[40] M.-Y. Yu, T.-T. Guo, X.-C. Shi, J. Yang, X. Xu, J.-F. Ma, Z.-T. Yu, Polyoxometalate-
bridged Cu(I)- and Ag(I)-thiacalix[4]arene dimers for heterogeneous catalytic
oxidative desulfurization and azide–alkyne “click” reaction, Inorg. Chem. 58
(2019) 11010–11019.
[15] X. Chen, Z. Wang, R. Zhang, L. Xu, D. Sun, A novel polyoxometalate-based hybrid
[41] M.-Y. Yu, J. Yang, T.-T. Guo, J.-F. Ma, Efficient catalytic oxidative desulfurization
toward thioether and sulfur mustard stimulant by polyoxomolybdate–resorcin
[4]arene-based metal–organic materials, Inorg. Chem. 59 (2020) 4985–4994.
[42] W.-Y. Pei, J. Yang, H. Wu, W. Zhou, Y.-W. Yang, J.-F. Ma, A calix[4]resorcinarene-
based giant coordination cage: controlled assembly and iodine uptake, Chem.
Commun. 56 (2020) 2491–2494.
[43] D. Liu, B.-B. Lu, W.-Y. Pei, Z.-Y. Gu, J. Yang, X.-L. Wu, J.-F. Ma, A new poly-
oxometalate-resorcin[4]arene-based framework as an efficient anode material
for lithium-ion batteries, J. Alloy. Compd. 835 (2020) 155314.
[44] Y. Zheng, S. Zheng, H. Xue, H. Pang, Metal-organic frameworks/graphene-based
materials: preparations and applications, Adv. Funct. Mater. 28 (2018) 1804950.
[45] H. Wu, W. Zhang, S. Kandambeth, O. Shekhah, M. Eddaoudi, H.N. Alshareef,
Conductive metal-organic frameworks selectively grown on laser-scribed graphene
for electrochemical microsupercapacitors, Adv. Energy Mater. 9 (2019) 1900482.
[46] T. Wei, M. Zhang, P. Wu, Y.-J. Tang, S.-L. Li, F.-C. Shen, X.-L. Wang, X.-P. Zhou, Y.-
Q. Lan, POM-based metal-organic framework/reduced graphene oxide nano-
composites with hybrid behavior of battery-supercapacitor for superior lithium
storage, Nano Energy 34 (2017) 205–214.
[47] C. Li, X. Lou, Q. Yang, Y. Zou, B. Hu, Remarkable improvement in the lithium
storage property of Co2(OH)2BDC MOF by covalent stitching to graphene and the
redox chemistry boosted by delocalized electron spins, Chem. Eng. J. 326 (2017)
1000–1008.
[48] J. Sun, A. Klechikov, C. Moise, M. Prodana, M. Enachescu, A.V. Talyzin, A mole-
cular pillar approach to grow vertical covalent organic framework nanosheets on
graphene: hybrid materials for energy storage, Angew. Chem. Int. Ed. 57 (2018)
1034–1038.
[49] K. Jayaramulu, D.P. Dubal, A. Schneemann, V. Ranc, C. Perez-Reyes, J. Stráská,
Š. Kment, M. Otyepka, R.A. Fischer, R. Zbořil, Shape-assisted 2D MOF/graphene
derived hybrids as exceptional Lithium-ion battery electrodes, Adv. Funct. Mater.
29 (2019) 1902539.
[50] J. Hu, H. Diao, W. Luo, Y.-F. Song, Dawson-type polyoxomolybdate anions
(P2Mo18O626-) captured by ionic liquid on graphene oxide as high-capacity anode
material for lithium-ion batteries, Chem. Eur. J. 23 (2017) 8729–8735.
[51] A.L. Spek, PLATONSQUEEZE: a tool for the calculation of the disordered solvent
contribution to the calculated structure factors, Acta Crystallogr. Sect. C Struct.
Chem. 71 (2015) 9–18.
[52] P. Xiao, F. Bu, R. Zhao, M.F. Aly Aboud, I. Shakir, Y. Xu, Sub-5 nm ultrasmall
metal–organic framework nanocrystals for highly efficient electrochemical en-
ergy storage, ACS Nano 12 (2018) 3947–3953.
containing a 2D [CoMo8O26
] structure as the anode for lithium-ion batteries,
∞
Chem. Commun. 53 (2017) 10560–10563.
[16] H. Wang, S. Hamanaka, Y. Nishimoto, S. Irle, T. Yokoyama, H. Yoshikawa,
K. Awaga, In operando X-ray absorption fine structure studies of poly-
oxometalate molecular cluster batteries: polyoxometalates as electron sponges,
J. Am. Chem. Soc. 134 (2012) 4918–4924.
[17] J.-J. Chen, M.D. Symes, S.-C. Fan, M.-S. Zheng, H.N. Miras, Q.-F. Dong, L. Cronin,
High-performance polyoxometalate-based cathode materials for rechargeable
lithium-ion batteries, Adv. Mater. 27 (2015) 4649–4654.
[18] Y.-H. Ding, J. Peng, S.-U. Khan, Y. Yuan, A new polyoxometalate (POM)-based
composite: fabrication through POM-assisted polymerization of dopamine and
properties as anode materials for high-performance lithium-ion batteries, Chem.
Eur. J. 23 (2017) 10338–10343.
[19] S. Omwoma, C.T. Gore, Y. Ji, C. Hu, Y.-F. Song, Environmentally benign poly-
oxometalate materials, Coord. Chem. Rev. 286 (2015) 17–29.
[20] Q. Huang, T. Wei, M. Zhang, L.-Z. Dong, A.-M. Zhang, S.-L. Li, W.-J. Liu, J. Liu, Y.-
Q. Lan, A highly stable polyoxometalate-based metal–organic framework with π-
π stacking for enhancing lithium ion battery performance, J. Mater. Chem. A 5
(2017) 8477–8483.
[21] D. Chai, C.J. Gómez-García, B. Li, H. Pang, H. Ma, X. Wang, L. Tan,
Polyoxometalate-based metal-organic frameworks for boosting electrochemical
capacitor performance, Chem. Eng. J. 373 (2019) 587–597.
[22] R. Yu, X.-F. Kuang, X.-Y. Wu, C.-Z. Lu, J.P. Donahue, Stabilization and im-
mobilization of polyoxometalates in porous coordination polymers through
host–guest interactions, Coord. Chem. Rev. 253 (2009) 2872–2890.
[23] I.V. Kozhevnikov, Catalysis by heteropoly acids and multicomponent poly-
oxometalates in liquid-phase reactions, Chem. Rev. 98 (1998) 171–198.
[24] P.-P. Zhu, N. Sheng, M.-T. Li, J.-S. Li, G.-D. Liu, X.-Y. Yang, J.-Q. Sha, M.-L. Zhu,
J. Jiang, Fabrication and electrochemical performance of unprecedented POM-
based metal–carbene frameworks, J. Mater. Chem. A 5 (2017) 17920–17925.
[25] M. Genovese, K. Lian, Ionic liquid-derived imidazolium cation linkers for the
layer-by-layer assembly of polyoxometalate-MWCNT composite electrodes with
high power capability, ACS Appl. Mater. Interfaces 8 (2016) 19100–19109.
[26] F. Xiao, J. Hao, J. Zhang, C. Lv, P. Yin, L. Wang, Y. Wei, Polyoxometalatocyclophanes:
controlled assembly of polyoxometalate-based chiral metallamacrocycles from
achiral building blocks, J. Am. Chem. Soc. 132 (2010) 5956–5957.
[27] C.T. Buru, P. Li, B.L. Mehdi, A. Dohnalkova, A.E. Platero-Prats, N.D. Browning,
K.W. Chapman, J.T. Hupp, O.K. Farha, Adsorption of a catalytically accessible
polyoxometalate in
Chem. Mater. 29 (2017) 5174–5181.
a
mesoporous channel-type metal–organic framework,
[53] C. Dong, L. Xu, Cobalt- and cadmium-based metal-organic frameworks as high
performance anodes for sodium ion batteries and lithium ion batteries, ACS
Appl. Mater. Interfaces 9 (2017) 7160–7168.
[54] D. Fu, H. Li, X.-M. Zhang, G. Han, H. Zhou, Y. Chang, Flexible solid-state super-
capacitor fabricated by metal-organic framework/graphene oxide hybrid inter-
connected with PEDOT, Mater. Chem. Phys. 179 (2016) 166–173.
[55] K. Vasanth Kumar, C. Valenzuela-Calahorro, J.M. Juarez, M. Molina-Sabioa,
J. Silvestre-Alberoa, F. Rodriguez-Reinoso, Hybrid isotherms for adsorption and
capillary condensation of N2 at 77 K on porous and non-porous materials, Chem.
Eng. J. 162 (2010) 424–429.
[56] P. Sharma, N. Kumar, R. Chauhan, V. Singh, V.C. Srivastava, R. Bhatnagar, Growth
of hierarchical ZnO nano flower on large functionalized rGO sheet for superior
photocatalytic mineralization of antibiotic, Chem. Eng. J. 392 (2020) 123746.
[57] J.-Q. Sha, X.-Y. Yang, Y. Chen, P.-P. Zhu, Y.-F. Song, J. Jiang, Fabrication and elec-
trochemical performance of polyoxometalate-based three-dimensional metal
organic frameworks containing carbene nanocages, ACS Appl. Mater. Interfaces
10 (2018) 16660–16665.
[58] J. Sha, P. Zhu, X. Yang, X. Li, X. Li, M. Yue, K. Zhou, Polyoxometalates templated
metal Ag–carbene frameworks anodic material for lithium-ion batteries, Inorg.
Chem. 56 (2017) 11998–12002.
̀
[28] H.N. Miras, L. Vila-Nadal, L. Cronin, Polyoxometalate based open-frameworks
(POM-OFs), Chem. Soc. Rev. 43 (2014) 5679–5699.
[29] H. Ma, B. Liu, B. Li, L. Zhang, Y.G. Li, H.Q. Tan, H.Y. Zang, G. Zhu, Cationic covalent
organic frameworks: a simple platform of anionic exchange for porosity tuning
and proton conduction, J. Am. Chem. Soc. 138 (2016) 5897–5903.
[30] G. Paille, M. Gomez-Mingot, C. Roch-Marchal, B. Lassalle-Kaiser, P. Mialane,
M. Fontecave, C. Mellot-Draznieks, A. Dolbecq, A fully noble metal-free photo-
system based on cobalt-polyoxometalates immobilized in a porphyrinic meta-
l–organic framework for water oxidation, J. Am. Chem. Soc. 140 (2018)
3613–3618.
[31] W. Salomon, C. Roch-Marchal, P. Mialane, P. Rouschmeyer, C. Serre, M. Haouas,
F. Taulelle, S. Yang, L. Ruhlmann, A. Dolbecq, Immobilization of polyoxometalates
in the Zr-based metal organic framework UiO-67, Chem. Commun. 51 (2015)
2972–2975.
[32] S.-T. Zhang, J. Yang, H. Wu, Y.-Y. Liu, J.-F. Ma, Systematic investigation of high-
sensitivity luminescent sensing for polyoxometalates and iron(III) by MOFs as-
sembled with a new resorcin[4]arene-functionalized tetracarboxylate, Chem.
Eur. J. 21 (2015) 15806–15819.
[33] B.-B. Lu, W. Jiang, J. Yang, Y.-Y. Liu, J.-F. Ma, Resorcin[4]arene-based microporous
metal–organic framework as an efficient catalyst for CO2 cycloaddition with
epoxides and highly selective luminescent sensing of Cr2O72−, ACS Appl. Mater.
Interfaces 9 (2017) 39441–39449.
[34] W.-Y. Pei, G.H. Xu, J. Yang, H. Wu, B.L. Chen, W. Zhou, J.-F. Ma, Versatile assembly
of metal-coordinated calix[4]resorcinarene cavitands and cages through ancil-
lary linker tuning, J. Am. Chem. Soc. 139 (2017) 7648–7656.
[59] Y. Jin, C. Zhao, Z. Sun, Y. Lin, L. Chen, D. Wang, C. Shen, Facile synthesis of Fe-
MOF/RGO and its application as a high performance anode in lithium-ion bat-
teries, RSC Adv. 6 (2016) 30763–30768.
[60] Y.-Y. Wang, M. Zhang, S.-L. Li, S.-R. Zhang, W. Xie, J.-S. Qin, Z.-M. Su, Y.-Q. Lan,
Diamondoid-structured polymolybdate-based metal–organic frameworks as
high-capacity anodes for lithium-ion batteries, Chem. Commun. 53 (2017)
5204–5207.
[35] W. Jiang, J. Yang, Y.-Y. Liu, S.Y. Song, J.-F. Ma, A stable porphyrin-based porous
mog metal–organic framework as an efficient solvent-free catalyst for C–C bond
formation, Inorg. Chem. 56 (2017) 3036–3043.
[36] B.-B. Lu, J. Yang, G.-B. Che, W.-Y. Pei, J.-F. Ma, Highly stable copper(I)-based
metal–organic framework assembled with resorcin[4]arene and poly-
oxometalate for efficient heterogeneous catalysis of azide–alkyne “click” reac-
tion, ACS Appl. Mater. Interfaces 10 (2018) 2628–2636.
[61] D. Li, D. Yang, X. Yang, Y. Wang, Z. Guo, Y. Xia, S. Sun, S. Guo, Double-helix
structure in carrageenan–metal hydrogels: a general approach to porous metal
sulfides/carbon aerogels with excellent sodium-ion storage, Angew. Chem. Int.
Ed. 55 (2016) 15925–15928.
[62] D. Wu, H. Li, R. Li, Y. Hu, X. Hu, In situ growth of copper rhodizonate complexes
on reduced graphene oxide for high-performance organic lithium-ion batteries,
Chem. Commun. 54 (2018) 11415–11418.
[37] X.-X. Wang, J. Yang, X. Xu, J.-F. Ma, Highly stable copper(I)–thiacalix[4]arene-
based frameworks for highly efficient catalysis of click reactions in water, Chem.
Eur. J. 25 (2019) 16660–16667.
[63] R.R. Kapaev, S. Olthof, I.S. Zhidkov, E.Z. Kurmaev, K.J. Stevenson, K. Meerholz,
P.A. Troshin, Nickel(II) and copper(II) coordination polymers derived from 1,2,4,5-
tetraaminobenzene for lithium-ion batteries, Chem. Mater. 31 (2019) 5197–5205.
11

M.-Y. Yu, J.-H. Liu, J. Yang et al.
Journal of Alloys and Compounds 868 (2021) 159009
[64] J. Xie, Y. Zhang, Y. Han, C. Li, High-capacity molecular scale conversion anode
enabled by hybridizing cluster-type framework of high loading with amino-
functionalized graphene, ACS Nano 10 (2016) 5304–5313.
[65] M. Govindhan, B. Mao, A. Chen, Novel cobalt quantum dot/graphene nano-
composites as highly efficient electrocatalysts for water splitting, Nanoscale 8
(2016) 1485–1492.
[66] J.-S. Qin, D.-Y. Du, W. Guan, X.-J. Bo, Y.-F. Li, L.-P. Guo, Z.-M. Su, Y.-Y. Wang,
Y.-Q. Lan, H.-C. Zhou, Ultrastable polymolybdate-based metal–organic frame-
works as highly active electrocatalysts for hydrogen generation from water,
J. Am. Chem. Soc. 137 (2015) 7169–7177.
[67] W. Cheng, F.-C. Shen, Y.-S. Xue, X. Luo, M. Fang, Y.-Q. Lan, Y. Xu, A pair of rare
three-dimensional chiral polyoxometalate-based metal–organic framework
enantiomers featuring superior performance as the anode of lithium-ion bat-
tery, ACS Appl. Energy Mater. 1 (2018) 4931–4938.
[68] M.-T. Li, X.-Y. Yang, J.-S. Li, N. Sheng, G.-D. Liu, J.-Q. Sha, Y.-Q. Lan, Assembly of
multifold helical polyoxometalate-based metal–organic frameworks as anode
materials in lithium-ion batteries, Inorg. Chem. 57 (2018) 3865–3872.
[69] H. Hosseinia, S. Shahrokhian, Self-supported nanoporous Zn–Ni–Co/Cu selenides
microball arrays for hybrid energy storage and electrocatalytic water/urea
splitting, Chem. Eng. J. 375 (2019) 122090.
[70] J. Sun, J. Liu, H. Chen, X. Han, Y. Wu, J. He, C. Han, G. Yang, Y. Shan, Strongly
coupled Mo2C and Ni nanoparticles with in-situ formed interfaces encapsulated
by porous carbon nanofibers for efficient hydrogen evolution reaction under
alkaline conditions, J. Colloid Interface Sci. 558 (2020) 100–105.
12