Empowering organic-based negative electrode material based on conjugated lithium carboxylate through molecular design

Article abstract of DOI:10.1002/cssc.202000140

In this article, we describe the design and gram-scale synthesis of a new anthracene-based negative electrode material for Li-ion batteries. Based on rational design, featuring a strong electronic delocalization and a long conjugation length, this material has power performance to date unmatched for a conjugated lithium carboxylate, displaying a gravimetric capacity of 150 mAh g^?1 at a cycling rate of 20 Li⁺/h (10 C) without any electrode engineering. Additionally, to the design, partial solubility of the fully reduced phase may also explain the electrochemical performances obtained at a low and high rate.

Full text of DOI:10.1002/cssc.202000140

Accepted Article
Title: Empowering organic-based negative electrode material based on
conjugated lithium carboxylate through molecular design
Authors: Lionel Fédèle, Olivier Ouari, Amadou Thiam, Frédéric
Sauvage, and Matthieu Becuwe
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To be cited as: ChemSusChem 10.1002/cssc.202000140
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ChemSusChem
10.1002/cssc.202000140
Empowering organic-based negative electrode material based on
conjugated lithium carboxylate through molecular design
Lionel Fédèle,1-4 Olivier Ouari,3,4 Frédéric Sauvage, 1,2,4 Amadou Thiam,1,2,4 Matthieu
Becuwe*1,2,4
1
Laboratoire de Réactivité et Chimie des Solides (LRCS), UMR CNRS 7314, Université de Picardie
Jules Verne (UPJV), Amiens, 33 rue Saint-leu, 80039 Amiens, France
2
Institut de Chimie de Picardie (ICP), FR CNRS 3085, 80039 Amiens, France
3
Aix Marseille Univ, CNRS, Institut de Chimie Radicalaire (ICR), UMR 7273, Marseille
13013, France
4
Réseau sur le Stockage Electrochimique de l’Energie (RS2E), FR CNRS 3459, 80039 Amiens,
France
TABLE OF CONTENT
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ChemSusChem
10.1002/cssc.202000140
ABSTRACT
In this article, we describe the design and gram-scale synthesis of a new anthracene-
based negative electrode material for Li-ion batteries. Based on rational design, featuring a
strong electronic delocalization and a long conjugation length, this material has power
performance to date unmatched for a conjugated lithium carboxylate, displaying a gravimetric
-1
+
capacity of 150 mAh.g at a cycling rate of 20 Li /h (10C) without any electrode engineering.
Additionally, to the design, partial solubility of the fully reduced phase may also explain the
electrochemical performances obtained at low and high rate.
INTRODUCTION
We are currently facing global climate change mainly caused by global warming. This
increase is directly linked to the release of greenhouse gases by human activities, which is
constantly increasing. To hamper this critical issue, a complete overhaul of our habits in terms
of transport, energy production and consumption is required. This has already started with the
growth of renewable energies. However, owing to the intermittency of these processes, it is
essential to have efficient storage systems for delivering on-demand and transporting the energy
thus produced.
Ion batteries are currently the most efficient systems addressing these specifications.
Nevertheless, the electroactive compounds used as an electrode in these systems are exclusively
inorganic materials based on Co, Mn, Fe, Ni, V, which are exhaustible, difficult to recycle and
sometimes toxic. In parallel to the eco-conception of electroactive materials2–4 and the
1
5
recycling of current Li-ion batteries constitutants, a promising solution to overcome these
problems is to use renewable resources such as organic compounds, from inedible agro-
resources and/or "green" sustainable synthesis processes taking into account the resource aspect
and ecological sustainability, to create sustainable, efficient and easy recycling electrical energy
6
storage systems. For now, Organic batteries field benefits of more than ten years of intensive
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ChemSusChem
10.1002/cssc.202000140
research and is still an active research area. 7–9 Positioned between sulfur and intercalation
1
0
compound in the battery materials landscape, performances of organic electrode materials
have strongly evolved representing a serious alternative in support to inorganic compounds and
to the constantly growing demand for more sustainable batteries. These last years, several
improvements were realized like high potential and high power positive electrode materials11–
1
3
and high specific capacity.14–20 From our side, we focused on the enhancement of the rate
capability of conjugated lithium carboxylate, used as a negative electrode. Based on our
2
1
22
23
previous studies on naphthalene, perylene and biphenyl derivatives, it is now established
that kinetic properties of the materials depend on the electronic conjugation of the aromatic ring
on one hand and of the length and nature of the spacer and the associated crystallographic
opening of the material structure on the other hand.
On this basis, we capitalize our expertise to design a new material to improve the power
performances of the family of conjugated lithium carboxylate derivatives. The anthracene core,
well-known in the optoelectronic field, was selected as a basis to welcome electroactive
function. Anthracene derivatives caught interest in the last ten years since the discovery of
remarkable electroluminescence, photoluminescence and semiconducting properties.24 This
family of molecules is nowadays integrated into various application fields like electronics,25
2
6
27
sensing or supramolecular chemistry. They have also been used as an emitter and electrical
transport layer in organic light-emitting diodes (OLED) in which they serve as building blocks
2
8
for the design of new robust materials. To make it electroactive at low potential, we have
developed the synthesis of the 2,6-anthracene dicarboxylate lithium (Li -ADC) which has a
strong electronic delocalization and in the same time has a slightly larger size than the dilithium
,4’-Biphenyl dicarboxylate also known as Li -BPDC (Figure 1).
2
4
2
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10.1002/cssc.202000140
Figure 1: Evolution of the distance between the two end carboxylates (carbon-carbon distance) and
electrostatic map, obtained using Spartan 18 software, in different centrosymmetric aromatic organic
conjugated lithium carboxylate used as a negative electrode material. In the electrostatic maps, electron-
poor and electron-rich regions are indicated respectively in blue and red.
Li -ADC was synthesized at gram scale from cheap and commercially available 2,6-diamino
2
-1
+
anthraquinone and exhibits outstanding rate capability with 160 mAhg at 20 Li /h (10C) rate
which is the higher value reported in the literature at te best of our knowledge.
RESULTS AND DISCUSSION
Unlike the previously described materials based on naphthalene, perylene and
biphenyl,21–23 2,6-anthracene dicarboxylic acid (ADC) is not commercially available. Multiple
strategies and synthetic routes have been explored to obtain Li
2
-ADC on a multiple gram scale.
The most efficient synthetic pathway in our hands starts from 2,6-diaminoanthraquinone. Li
2
-
ADC was prepared in a 7-step sequence with a 30% overall yield (Scheme 1). Two functional
group transformations were identified as key steps: the introduction of carboxylic groups from
amino derivatives (from diaminoanthraquinone to 3) and the reduction of anthraquinone to
anthracene (from 3 to 6).29–32
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10.1002/cssc.202000140
i) NH4OH, Zn
i) CuBr, tBuONO, ACN
ii) CuCN, NMP
ii) Li2CO3,DMF, MeI
iii)DDQ, Toluene
iv) KOH, MeOH reflux
iii) H2SO4, Reflux
(
3)
(6)
Scheme 1: Preparation of 2,6-anthracene dicarboxylic acid from 2,6-diaminoanthraquinone. (i) t-BuONO,
CuBr
2
, ACN, 80°C, 96%. (ii) CuCN, NMP, 180°C, 6h, 98%. (iii) H
0°C, 95%. (v) CH I, Li CO
8%.
2
SO
4
, water, 160°C, 80%. (iv) Zn, NH OH,
4
°
8
8
3
2
3
, DMF, RT, 78%. (vi) DDQ, Toluene, 115 C, 70%. (vii) NaOH, EtOH, 70°C,
Targeted lithium carboxylate (Li -ADC) was then obtained by refluxing the diacid in an EtOH
2
solution of lithium hydroxide, enabling crystallization of the titled compound (8) (Figure 2a).
1
Complete lithiation was evidenced by H NMR with shielding the characteristic peaks of the
carboxylic acid (Figure 2b). Signals corresponding to the isolated protons 1 and 9 (Figure 2a)
are shielded after the deprotonation, shifting from 8.89 and 8.83 ppm to 8.47 and 8.45 ppm,
respectively (Figure 2b). The peaks corresponding to the protons 3 and 4 are also affected with
13
shifts from 8.21 to 7.98 ppm and 7.98 to 7.89 ppm, respectively (Figure 2b). Solid-state C
NMR analysis confirms the total conversion of the carboxylic acid groups to lithium
carboxylate with a shift of the peak corresponding to the carbonyl groups from 170 ppm to 176
1
3
ppm (Figure 2c). A change in the C NMR chemical shifts of the aromatic carbon atoms is also
observed, evolving from large peaks to 4 narrower peaks. FT-Infrared spectroscopy analysis
leads to the same conclusions with the disappearance of the broad peak corresponding to O-H
-
1
-1
group between 2000 cm and 3500 cm and the modification of the asymmetric vibration of
-1
-1
the carbonyl group moving from 1690 cm in the carboxylic acid form to 1420 cm for the
lithium carboxylate (Figure 2d).
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ChemSusChem
10.1002/cssc.202000140
9
1
9
1
a)
LiOH.H 0 (3eq.)
2
EtOH
3
3
4
4
b)
c)
d)
1
9
nC=O Asym
C
Ar
nC=O Sym
COOLi
3
4
Li
2
-ADC
1
9
4
nC=O Asym
3
COOH
O-H Déformation
nC=O Sym
ADC
100
1
90
180
170
160 150
140
13
130
120
110
4
000 3500 3000 2500 2000 1500 1000
500
1
Wavenumber (cm-1)
Chemical shift H (ppm)
Dé
C
p
h
l
e
a
m
ce
i
m
ca
e
l
n
sh
t
i
c
f
h
t
im
C
iq
(
u
p
e
p m( p
)
pm)
Figure 2: (a) Synthesis of dilithium 2,6-anthracene dicarboxylate (Li
dicarboxylic acid (ADC). Comparison between ADC (blue curves) and Li
2
-ADC) from 2,6-anthracene
2
-ADC (red curves) by (b) liquid-
state H NMR (400 MHz) in DMSO-d6, (c) solid-state C NMR (500 MHz) using CP-MAS sequence and
d) FTIR in transmission mode.
1
13
(
The lithiation process also leads to structural notable modifications as evidenced by powder X-
ray diffraction (Figure 3a). While only three very large diffraction peaks are observed for the
acid form, indicating a strong disorder in the initial structure, the diffraction pattern of the
corresponding lithiated form reveals intense and highly resolved peaks. Scanning electron
microscopy also shows an important morphological change. The carboxylic acid ADC is
organized into rods 10 μm long and 3 μm wide (Figure 3b) while the dilithium salt forms mainly
agglomerates of small particles whose size is in the order of 400-700 nm (Figure 3c). This
change in textural parameters can be explained by the partial dissolution of acid in ethanol
followed by precipitation of the lithium salt which is very poorly soluble in this solvent.
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ChemSusChem
10.1002/cssc.202000140
a)
b)
c)
ADC
Li -ADC
2
Li -ADC
2
ADC
5
µm
5 µm
10
20
30
40
50
Diffraction angle 2θ (°)-CuKα
Figure 3: Comparison between Li
2
-ADC (red curve) and ADC (black curve) by (a) powder X-ray diffraction
and (b and c) by Scanning Electron Microscopy.
In terms of storage performances, Li
2
-ADC has an electrochemical signature similar to the one
-
generally obtained with lithium carboxylate with the presence of a low potential 2e -plateau
traducing a bi-phasic type lithium insertion/deinsertion reaction (Figure 4). The reduction
+
potential is situated at 0.81 V (vs. Li /Li) indicating that the addition of an aromatic ring (from
naphthalene to anthracene) has little influence on the redox potential. The particularity of Li -
2
ADC comes from the exceptional power behaviour compared to the set of conjugated lithium
carboxylate-based materials described so far.22,23,33–39 Indeed, up to 5 Li /h (maximum speed
+
for the Li
4
-PTC for instance), Li
2
-ADC exhibits complete electrochemical activity (reversibility
+
-1
of 2 Li , specific capacity of 190 mAh.g ) associated with a quite low polarization of about
1
60mV despite a high regime and lack of optimization of the electrode (Figure 4a and 4b). At
+
+
even higher cycling rate, namely, 10 Li /h and 20 Li /h, the electrochemical activity is always
-1
present with an outstanding reversible capacity on the first cycles of 166 mAh.g and 162
-1
mAh.g respectively, despite an increase on the polarization reaching about 320 mV (Figure
c and 4d). To the best of our knowledge, these performances were never obtained for a
4
conjugated lithium carboxylate-based material without electrode formulation and recall the
-PTC.22,40
story about Li
4
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ChemSusChem
10.1002/cssc.202000140
a)
b)
c)
d)
3
3
2.5
2
3
2.5
2
3
2.5
2
+
+
+
+
2
Li /h
5 Li /h
10 Li /h
20 Li /h
2
1
0
.5
2
1
.5
1
1
.5
1
1.5
1
.5
1
0.5
0.5
0.5
.5
0
0.5
1
1.5
2
2.5
3
3.5
0
0.5
1
1.5
2
2.5
3
3.5
4
0
0.5
1
1.5
2
2.5
3
3.5
0
0.5
1
1.5
2
2.5
3
3.5
x in Li2+xC16H O Li
x in Li2+xC16H O Li
x in Li2+xC16H O Li
x in Li2+xC16H O Li
8 4 2
8
4
2
8
4
2
8
4
2
Figure 4: Galvanostatic potential-composition profiles for Li2-ADC manually grind with 40% carbon mass
+
+
+
+
Super P at regime of (a) 2 Li /h, (b) 5 Li /h, (c) 10 Li /h and (d) 20 Li /h rate.
It is interesting to note the absence of the bump of potential observed at the end of oxidation
for Li
consequence of the greater distance between the two carboxylates for Li
accommodate even better to the penetration of the solvated ion and/or electrolyte in material
structure. After 50 cycles, Li -ADC still displays impressive capabilities especially at very high
speeds with specific capacities of 144 mAh.g , 134 mAh.g and 133 mAh.g at speeds of 5
2
-BPDC and belonging with the solvent intercalation.23 This fact is probably the
2
-ADC that would
2
-1
-1
-1
+
+
+
Li /h, 20 Li /h and 10 Li /h respectively (Figure 5).
320
280
240
200
160
120
+
0
2
5
1
.4 Li /h
+
Li /h
+
Li /h
+
0 Li /h
Shuttling effect
boosting power)
+
At high rate
20 Li /h
(
8
0
0
0
Dissolution of Li
4
-ADC
(
capacity fading)
4
At low rate
0
10
20
30
40
50
Cycle number
+
+
Figure 5: Evolution of the gravimetric capacity at different regimes (from 0.4 Li /h to 20 Li /h) as a function
of the number of cycles and illustration of the origin of both rate capability rise and loss of capacity at a low
rate.
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10.1002/cssc.202000140
Despite such performances at a high rate, the cycling of Li
2
-ADC at a lower rate reveals a
+
-1
decrease in capacity at a regime of 2 Li /h (111 mAh.g ) and becoming drastically significant
+
-1
at 0.4 Li /h (37 mAh.g ) independently of the electrolyte concentration or type used. One
possible explanation of this gradual fading, also observed for previously reported high rate
cycling materials based on lithium carboxylate, could be the solubility of the materials (never
observed for lithium carboxylate). In the present case, since a solvent change was realized for
the lithiation reaction (ethanol instead of methanol), this fact can make sense. To verify
solubility of the material at the reduced state (Li
including Li
4
-ADC phase), a specific electrochemical cell
+
2
-ADC/composite was assembled and reduced until 0.5V at a low rate (0.4Li /h).
The cell was allowed to stand for 48h at this state before being opened. The separators were
then collected and compared with pure and impregnated separators with LP30. Since anthracene
derivatives are fluorescent (emission of a blue fluorescence when exposed to UV-light),41
separators were exposed to such type of radiation (335nm precisely) to perceive any fluorescent
compound. While pure and impregnated separators are uncolored, the separator recovered from
the cell shows a blue fluorescence signal attributed to the anthracene derivative. This
observation indicated that the reduced state of the molecular compound tends to solubilize in
the electrolyte and can explain the capacity fading at a low rate. The same experiments were
realized on separators of cycled cells at a high rate. No fluorescence was detected in the
separators which indicated that no materials were dissolved in the electrolyte at a high rate,
presumably because of the cycling kinetics. At a sufficient rate, the dissolution of the reduced
phase is not sufficient to cause capacity fading. Based on this fact, it might be possible to have
only surface solubility of the material (and directly followed by reprecipitation on the surface
of the materials particle or insoluble part). This could lead to explain the excellent power
performances by the boosting of the electron transfer from the conductive additive particle to
the material and vice-versa though a molecular shuttling effect (Figure 5).
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CONCLUSIONS
We presented here the rational design of a new conjugated lithium carboxylate including an
anthracene unit as negative electrode materials for lithium-ion batteries. Owing to the strong
electronic delocalization of the anthracene unit coupled with the high conjugation distance
between the two carboxylates (opening of the material), this material exhibits an excellent rate
+
capability with 77% of the theoretical gravimetric capacity after 50 cycles at 20 Li /h rate
without any formulation engineering. Additionally to the specific design, the outstanding power
performances may also be attributed to the partial solubility of the molecular material at the
reduced state promoting an electronic shuttle effect between conductive additive particle and
active material.
EXPERIMENTAL SECTION
Reagents and Chemicals
All the compounds used were purchased either from Alfa Aesar or Sigma-Aldrich. All
the solvents were purchased from Fischer scientific. Deuterated dimethylsulfoxide (DMSO-d6)
was purchased from Euriso-top. All solvents and reagents were used as received.
Instrumentation
FT-IR (Fourier Transform Infra-Red) spectra were recorded in transmission mode at
room temperature using a Nicolet AVATAR 370 DTGS spectrometer from Thermo Electron
−
1
Corporation. Spectra were acquired over a range of 4000 to 400 cm with a resolution of 2
−
1 1
cm . H liquid NMR (Nuclear Magnetic Resonance) spectra were recorded on a Bruker 300
MHz spectrometer, chemical shifts are reported in parts per million (ppm) and coupling
1
3
constants (J) values are given in hertz. The solid-state C-NMR experiments were carried out
1
at room temperature on a Bruker Avance I wide-bore spectrometer operating at a H Larmor
frequency of 300 MHz, with a Bruker 4 mm double resonance CPMAS probe-head. The magic
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ChemSusChem
10.1002/cssc.202000140
1
3
angle spinning rate was 12.5 kHz. All C chemical shifts presented in this manuscript were
referenced with respect to the CH
TMS.
2
resonance of adamantane at 38.48 ppm with respect to neat
X-Ray Powder Diffraction patterns (XRPD) were acquired using a Bruker D8
diffractometer equipped with a Cu anti-cathode (K radiation, operating at 40 kV–40 mA).
α
Patterns were collected in the 2θ range of 10–60° with a step size of 0.03°. The particles
morphology and their size were estimated by Scanning Electron Microscopy (SEM) using an
environmental FEI Quanta 200 FEG-microscope.
Electrochemical performances were determined using 2 electrodes Swagelok-type cell
assembled in an argon-filled glovebox. For this, a typical working electrode was composed of
ca. 10 mg of active material (60%) manually mixed with 40 % of Super P carbon. It was
separated from a lithium foil playing both the role of counter and reference electrode by two
Whatman fibreglass sheets soaked with LiPF
6
(1M) in ethylene carbonate-dimethyl carbonate
(EC-DMC) 1/1 (v/v) mixture (LP30 electrolyte, certified battery purity grade, Merck). The
+
different galvanostatic measurements were recorded between 3 V and 0.4 V (vs. Li /Li) using
a Biologic VMP potentiostat/galvanostat.
Synthesis of Li
2
-ADC
2
,6-dibromo-9,10-anthraquinone (1):29
Copper (II) Bromide (21.09 g, 94.42mmol) was dissolved in 90 mL of anhydrous acetonitrile
and tert-butyl nitrite (26.2 mL, 220.36mmol) was slowly added under stirring. The mixture was
heated to 70°C and 2,6-diaminoanthraquinone (1) (15 g, 62.96mmol) were added over for 10
minutes. Strong release of nitrogen is observed. When the nitrogen evolution has stopped, the
mixture was cooled at room temperature and was poured into an aqueous solution of HCl (20%
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ChemSusChem
10.1002/cssc.202000140
v/v) under vigorous stirring during 20 minutes. Then the precipitate was recovered by filtration
and was washed several times with water to give a yellow-brown product (22.10 g, 96% yield).
1H NMR (400 MHz, CDCl
), δ in ppm: 8.43 (d, J = 2.00 Hz, 2H), 8.17 (d, J = 8.30 Hz, 2H),
3
1
3
7
1
1
.94 (dd, J = 2.00 Hz, J = 8.30 Hz, 2H); C NMR (100.62 MHz, CDCl ), δ in ppm: 181.43,
3
37.55, 134.47, 131.90, 130.52, 130.34, 129.29. IR (KBr): 3091, 3065, 1673, 1573, 1313, 1282,
160, 1065, 826, 730.
2
,6-dicyano-9,10-anthraquinone (2):30
A mixture of Copper (I) Cyanide (17.61 g, 196.72mmol) and 2,6-dibromo-9,10-anthraquinone
1) (18 g, 49.18 mmol) were added in 220 mL of NMP and stirred. The mixture was heated to
90°C for 8 hours, then cooled at room temperature and then precipitated in water (300 mL). A
(
1
solid dark compound was filtered and washed with a saturated EDTA solution to eliminate
residual Copper. After washing with EDTA solution until complete discoloration, the powder
was washed again with water to give a brown solid (12.5 g, 98.5% yield) and was used without
further purification.
1H NMR (400 MHz, DMSO-d
IR (KBr): 3091, 3043, 2230, 1678, 1600, 1317, 1295, 1195, 860, 730
), δ in ppm: 8.61 (d, J = 35.5 Hz, 2H), 8.34 (s, 2H), 7.73 (s, 1H).
6
2
,6-Anthraquinone dicarboxylic acid (3):30
2
,6-dicyano-9,10-anthraquinone (2, 12 g, 46.47mmol) was stirred in 53 mL of water and then
(158 mL, 4.92mol) of sulphuric acid (95%) was slowly added under vigorous stirring. The
mixture was heated to 160°C for 6h and was cooled to room temperature. The mixture was
poured into 160 mL of water under stirring for 20 minutes then filtered and washed with water
to give a pale brown powder (11 g, 80% yield).
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10.1002/cssc.202000140
1H NMR (400 MHz, CDCl
), δ in ppm: 8.54 (s, 2H), 8.31 (d, J = 6.8 Hz, 2H), 8.20 (d, J = 7.7
3
1
3
Hz, 2H). C NMR (100.62 MHz, CDCl
3
), δ in ppm: 181.27, 165.76, 135.76, 135.37, 134.52,
1
7
32.94, 127.38. IR (KBr): 3343, 3047, 2634, 2360, 1695, 1604, 1478, 1430, 1273, 969, 869,
13
9
,10-dihydro-anthracene-2,6-dicarboxylic acid (4):31
A mixture of 2,6-anthraquinone dicarboxylic acid (3, 9 g, 30.38 mmol) and 90 mL of
ammonium hydroxide (28% in water) was stirred and zinc powder (12.5 g, 191.4 mmol) was
added before heating to 80°C and maintained at this temperature until the end of the reaction.
The mixture was stirred for 24h and an additional 10 mL of ammonium hydroxide was added
through this period until the red colour disappeared. Then, the mixture was filtered to remove
zinc powder and was acidified with 35% concentrated aqueous HCl. A yellow precipitate was
recovered by filtration and washed with water and dried under vacuum to give 7.75 g (95%
Yield).
1H NMR (400 MHz, DMSO-d
), δ in ppm: 12.84 (s, 2H), 7.93 (s, 2H), 7.80 (d, J = 7.6 Hz, 2H),
6
1
3
7
1
2
.46 (d, J = 7.8 Hz, 2H), 4.07 (s, 4H). C NMR (100.62 MHz, DMSO-d ), δ in ppm: 167.30,
6
41.59, 136.40, 128.76, 128.16, 127.47, 127.32, 39.52, 35.27. IR (KBr): 3434, 3017, 2804,
000, 1704, 1617, 1569, 1408, 1265, 930, 752
Dimethyl-9,10-dihydro-2,6-anthracenedicarboxylate (5):
In 110 ml of DMF, 8 g of 9,10-dihydro-anthracene-2,6-dicarboxylic acid (4) (29.82 mmol) and
1
3.2 g of lithium carbonate (178.9 mmol) were added under vigorous stirring. Then 11.2 ml of
methyl iodide (178.9 mmol) was added and the mixture was stirred at room temperature for 48
h. The mixture was poured in 300 ml of aqueous HCl solution (1M) then the precipitate was
filtered and washed several times with water. The solid was dried under reduced pressure to
afford (5), as a brown solid (6.8 g, 78%) which was used without further purification.
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ChemSusChem
10.1002/cssc.202000140
1H NMR (400 MHz, DMSO-d
), δ in ppm: 7.94 (s, 2H), 7.81 (d J=7.6 Hz, 2H), 7.47 (d, J=7.82
6
1
3
2
1
1
H), 4.08 (s, 2H), 3.86 (s, 3H). C NMR (100.62 MHz, DMSO-d ), δ in ppm: 166.20, 142.00,
6
36.53, 127.94, 127.62, 127.16, 52.00, 39.73, 35.18. IR (KBr): 3021, 2947, 1713, 1669, 1434,
317, 1247, 1086921, 752
Dimethyl-2,6-anthracenedicarboxylate (6):
A mixture of Dimethyl-9,10-dihydro-2,6-anthracenedicarboxylate (5), (6 g, 20.25 mmol), 2,3-
dichloro-5,6-dicyano-1,4-benzoquinone (12.73 g, 56.09 mmol) in toluene (125 mL) was stirred
at 115°C for 3h. The mixture was cooled at room temperature and filtered under vacuum. The
precipitate was washed several times with toluene and then methanol until complete
discoloration. The solid was dried under reduced pressure to give dimethyl anthracene-2,6-
dicarboxylate (6), (4.2 g, 70 %) as a brown solid.
1H NMR (400 MHz, CDCl
), δ in ppm: 8.82 (s, 2H), 8.59 (s, 2H), 8.20–7.93 (m, 4H), 4.02 (s,
3
1
3
6
1
9
H). C NMR (100.62 MHz, CDCl ), δ in ppm: 167.01, 132.98, 132.10, 131.82, 128.76,
3
28.58, 127.98, 124.60, 77.00, 52.38. IR (KBr): 3013, 2956, 1713, 1665, 1430, 1313, 1082,
21, 873, 756.
2
,6-Anthracene-dicarboxylic acid (7):
To a suspension of 4 g of dimethyl-2,6-anthracenedicarboxylate (6) (13.59 mmol) in 70 mL of
ethanol was added 7.62 g of KOH (135.91 mmol). The mixture was heated at reflux under
stirring overnight. The mixture was cooled at room temperature and poured to 1M aqueous HCl
solution (200 mL) then the dark brown precipitate was collected by vacuum filtration. The dark
brown solid was washed several times with water dried under reduced pressure to afford
anthracene-2,6-dicarboxylic acid (ADC, 7) (3.2 g; 88 % yield).
1H NMR (400 MHz, DMSO-d
.9 Hz, 2H), 7.98 (dd, J = 8.9, 1.6 Hz, 2H). C NMR (300MHz, DMSO-d ), δ in ppm: 167.25,
) δ in ppm: 8.89 (s, 2H), 8.83 (d, J = 1.5 Hz, 2H), 8.21 (d, J =
6
1
3
8
6
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ChemSusChem
10.1002/cssc.202000140
1
1
32.40, 131.67, 131.52, 131.36, 128.80, 128.53, 124.57. IR (KBr): 3352, 1934, 1678, 1621,
473, 1408, 1273, 921, 747
Dilithium 2,6-Anthracene dicarboxylate (Li -ADC) :
2
To a suspension of 0.5 g of 2,6-anthracene dicarboxylic acid (ADC) in 20 mL of ethanol was
added 3 equivalents of LiOH. The mixture was then heated under stirring at reflux overnight to
yield to the crystallization of the di-lithium salt as a brow powder (yield 89 %). The solid was
collected by centrifugation and washed successively with pure ethanol, acetone and diethyl
ether. The powder was finally dried under vacuum at 80°C and transferred into an argon-filled
glovebox for storage.
ACKNOWLEDGEMENTS
The authors would like to thank the French Research Network on Electrochemical Energy
Storage (RS2E) for support of this project and the Agence Nationale de la Recherche (Labex
STORE-EX) for the PhD grant of L.F. This work is also part of the ANR “VOLTA” project
(ANR-13-PRGE-0012). The authors would like to thank Pr P. Poizot (IMN, Nantes) and Dr F.
Dolhem (LG2A, Amiens) for fruitful discussions.
CONFLICT OF INTEREST
The authors declare no conflict of interest.
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