Supplementary Figure 4 | Electrochemical impedance spectra. a, Electrochemical. 56 impedance spectrum of 1 M 0.5Na-BP-DME (cell constant K=1.05) (Note ...
1 2
Supplementary Figures
3 4
5 6 7
Supplementary Figure 1 | Solubility of BP in DME and Na in BP-DME solvent.
8
Photograph of BP-DME solutions. b, Chemical titration profile and photograph of 5 M
9
Na-BP-DME solution. Chemical titration was carried out to check solubility of Na in
10
BP-DME solvent. In detail, 1 mL Na saturated 5 M Na-BP-DME solution was dissolved
11
into 3 mL H2O, and the final products (NaOH solution) was titrated by 0.225 mL HCl
a,
12
to PH=7.0. From this result, we can calculate the solubility of Na is 5 M.
13 14 15 16 17 18
19 20 21
Supplementary Figure 2 | Photograph of conductivity measurement devices. a,
22
Illustration of Rosull DJS-1 cell, the cell constant is K=1.05.
23
ion blocking cell which was designed by sandwiched a copper foil between two Pt
24
electrodes to block Na+ ion transportation during measurement, the cell constant is
25
K=7.0.
26 27
b, Illustration of the Na+
28 29 30 31 32 33
34 35 36
Supplementary Figure 3｜Stability of Na-β"-Al2O3 in Na-BP-DME solution.
37
patterns of fresh Na-β"-Al2O3 compared with Na-β"-Al2O3 soaked in Na-BP-DME for
38
one month.
39 40 41 42
XRD
43 44 45 46 47 48 49 50 51 52 53
54 55 56
Supplementary Figure 4 | Electrochemical impedance spectra.
57
impedance spectrum of 1 M 0.5Na-BP-DME (cell constant K=1.05) (Note that the
a, Electrochemical
58
0.5Na-BP-DME refers to 0.5 mol Na removal from 1 mol Na-BP-DME.).
59
Electrochemical impedance spectrum of 1 M 1.5Na-BP-DME (cell constant K=1.05)
60
(Note that the 1.5Na-BP-DME refers to 0.5 mol Na uptake into 1 mol Na-BP-DME.).
61 62 63 64 65 66 67 68 69 70 71 72
b,
73 74 75
Supplementary Figure 5 | Solubility of polysulfides in DMSO. a, Photograph of
76
Na2S8 dissolve into DMSO solutions. b, Photograph of Na2S3 dissolve into DMSO
77
solutions. c, Photograph of Na2S4 dissolve into DMSO solutions. Na2S8, Na2S4 and
78
Na2S3 solutions were prepared by dissolving Na2S and S into DMSO at molar ratio of
79
1:7, 1:3, 1:2 respectively, and the concentrations of Na2S8, Na2S4 and Na2S3 were 1 M
80
respectively.
81
on the bottom, indicating that the solubility of Na2S3 in DMSO is less than 1 M.
82
contrast, we do not observe any precipitation for 1 M Na2S4 and Na2S8 system, which
83
is in good agreement with Ref. [7].
84 85 86 87 88
For 1 M Na2S3 system, one can clearly see that there is precipitation In
89 90 91 92 93
94 95 96
Supplementary Figure 6 | Photograph and schematic of the cylinder cell.
97
stainless steel cylinder cell. b, Schematic of the Na2S8∣BASE∣Na-BP-DME cell in
98
which nickel foam was used as the Na-BP-DME anode current collector and carbon
99
felt as the Na2S8 cathode current collector.
100 101 102 103
a, The
c, Schematic of the Na2S8∣BASE∣
Na-BP-DME cell with Na metal insertion into Na saturated BP-DME hybrid anode.
104 105 106 107 108 109 110
111 112
Supplementary Figure 7｜Electrochemical performance of the cell with high
113
concentration Na-BP-DME liquid anode. Typical charge-discharge profiles of the cell
114
with 1 M Na-BP-DME and 5 M Na-BP-DME anode.
115 116 117
118 119 120
121 122
Supplementary Figure 8 ｜ Electrochemical performance of Na saturated
123
Na-BP-DME solution with an excessive Na metal soaked inside. a, Charge-discharge
124
profiles of symmetric cell constructed with Na saturated Na-BP-DME solution as
125
cathode and anode at a constant current of 0.5 mA. b, Voltage vs. time profiles of
126
this symmetric cell. c, The electrochemical impedance spectra of this symmetric cell
127
along with different cycles. d, Raman spectra of Na saturated Na-BP-DME solution
128
and Na metal taken from the solution. These preliminary results shown here indicate
129
that this Na saturated Na-BP-DME solution exhibits a high Na+ uptake and removal
130
reversibility and stability. The Raman results show that the components from the
131
surface of Na metal are the same as the Na saturated Na-BP-DME solution,
132
suggesting that there is no SEI formation on Na metal surface when Na is soaked in
133
this solution.
134 135 136 137 138
139 140 141
Supplementary Figure 9｜Conductivity of Na-BP-ether systems. Electrochemical
142
impedance spectra of Na-BP dissolved in different ether solvents: DME, DEGDME,
143
TRGDME, and TEGDME. There conductivities at room temperature are calculated to
144
be 1.2x10-2 S cm-1, 7x10-3 S cm-1, 3.5x10-3 S cm-1, 2.5x10-3 S cm-1, respectively (cell’s
145
constant K=1.05).
146 147 148 149 150 151 152 153 154 155
156 157 158
Supplementary Figure 10|Safety tests of Na-BP-DME liquid anode.
159
Na-BP-DME liquid anode with distilled water.
160
mL Na-BP-DME react with 1 mL water. c, Reaction of Na-BP-DME liquid anode with
161
Na2S8-DMSO liquid cathode.
162
(1M ) react with 10 mL Na2S8-DMSO (1 M) cathode (corresponding to ca. 500 mAh
163
cell).
164 165 166 167
a, Reaction of
b, Temperature change profile of 1
d, Temperature change profile of 40 mL Na-BP-DME
168 169
170
Supplementary Figure 11 | Schematic of the redox flow cells with Na-BP-DME
171
liquid anode. a, Schematic of common redox flow cell .
172
cathode flow cell. c, Schematic of single anode flow cell.
173
174 175 176
b, Schematic of single
177 178
179 180 181
Supplementary Figure 12 | Electrochemical performance of symmetrical redox flow
182
battery.
183
glove box, the thicknesses of the BASE and the electrode are 2 mm and 10 mm
184
respectively. b, Typical charge-discharge profile of (3 M) Na-BP-TEGDME∣BASE∣
185
Na-BP-TEGDME (0.5 M) symmetrical cell.
186
(3 M) dissolved into 3 M BP-TEGDME as catholyte, and Na (0.5 M) dissolved into 3 M
187
BP-TEGDME as anolyte. This cell was named as 3Na-BP-TEGDME ∣ BASE ∣
188
0.5Na-BP-TEGDME.
189
Na-BP-TEGDME. The volume of each electrolyte was 0.58 mL, theoretical capacity is
190
33 mAh based on volumetric capacity of 3 M Na-BP-TEGDME. Then, the utilization
191
ratio of Na+ is 88% calculated from charge capacity and theoretical capacity.
192 193 194 195
a, Digital photograph of the designed redox flow battery operated in the
Symmetrical cell was constructed with Na
This cell was assembled to investigate the reversibility of 3 M
196 197 198 199 200 201 202 203 204 205 206 207
208 209 210
Supplementary Figure 13 | Proof-of-concept of a redox flow battery testing. Typical
211
discharge-charge profile of Na2S8∣BASE∣Na-BP-TEGDME(3 M) redox flow battery with
212
3 M Na-BP-TEGDME anolyte. Note that the polarization is larger than that of cylinder
213
battery as shown in Fig. 4, which is mainly due to the design of the flow battery: on
214
one hand, the thickness of the BASE plate in the flow battery is 2 mm, however, the
215
thickness of the BASE tube used in the cylinder battery is 1 mm; on the other hand,
216
the thickness of the electrode in the flow battery is 10 mm while it is only 2 mm in
217
the cylinder battery. We believe that the performance can be further improved by
218
optimizing the system and engineering the cell structure, for instance, using new
219
catholyte system with higher energy density, a thinner Na-β"-Al2O3 electrolyte or
220
new electrolyte with higher ionic conductivity, and a highly porous current collector.
221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240
Supplementary Tables
241
Supplementary Table 1 | Total conductivity of Na-BP-DME solutions with different
242
concentrations. Concentration (mol L-1)
0.1
0.2
0.5
1
Total conductivity (S cm-1)
2.1x10-4
1.7 x10-3
6.2 x10-3
1.2 x10-2
4 1.7 x10-2
243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265
Supplementary Table 2｜ Capacity calculation of Na-BP-DME and Na2S8-DMSO Concentration
Volumetric capacity
Gravimetric capacity
1 M Na-BP-DME (real 0.87 M Na)
23 Ah L-1
25.6 Ah kg-1
2 M Na-BP-DME (real 1.49 M Na)
40 Ah L-1
44 Ah kg-1
3 M Na-BP-DME (real 2.09 M Na)
56 Ah L-1
57 Ah kg-1
4 M Na-BP-DME (real 2.51 M Na)
67 Ah L-1
68 Ah kg-1
5 M Na-BP-DME (real 2.77 M Na)
75 Ah L-1
76 Ah kg-1
Na/Na-BP-DME hybrid anode
1109 Ah L-1
1165 Ah kg-1
1 M Na2S8-DMSO
100 Ah L-1
72 Ah kg-1
266
Volumetric capacity was calculated based on total volume of Na, BP and DME. Gravimetric
267
capacity was calculated based on total mass of Na, BP and DME
268 269 270 271 272 273 274 275 276 277 278 279 280 281 282
283 284 285 286
Supplementary Table 3｜ Energy density calculation Anode
Cathode
Volumetric
Gravimetric
1 M Na-BP-DME
1 M Na2S8-DMSO
42 Wh L-1
42 Wh kg-1
2 M Na-BP-DME
1 M Na2S8-DMSO
63 Wh L-1
61 Wh kg-1
3 M Na-BP-DME
1 M Na2S8-DMSO
79 Wh L-1
70 Wh kg-1
4 M Na-BP-DME
1 M Na2S8-DMSO
88 Wh L-1
77 Wh kg-1
5 M Na-BP-DME
1 M Na2S8-DMSO
94 Wh L-1
81 Wh kg-1
1 M Na2S8-DMSO
201 Wh L-1
149 Wh kg-1
Na/Na-BP-DME hybrid anode
287
All of the volumetric energy density calculated based on total volume of anode and cathode, and
288
average operation voltage of 2.2 V. All of the gravimetric energy density calculated based on total
289
mass of anode and cathode, and average operation voltage of 2.2 V.
290 291 292 293 294 295 296 297
298 299 300 301 302 303 304 305 306 307 308
Supplementary Table 4｜ Cost calculation of Na2S8∣BASE∣Na-BP-DME(5 M) 1
309
kWh cell Na(＄0.23 kg-1) 0.38 kg ＄0.09
BP(＄1.2 kg-1)
DME(＄1.6 kg-1)
Total
2.53 kg
2.88 kg
5.79 kg
＄3
＄4.6
＄7.7
DMSO(＄0.8 kg-1)
Total
4.88 kg
6.26 kg
＄3.9
＄4.1
310 Na2S(＄0.23 kg-1)
S(＄0.13 kg-1)
0.35 kg
1 kg
＄0.08
＄0.13
311
Raw material cost of Na2S8∣BASE∣Na-BP-DME(4 M) cell is 11.8＄/kWh.
312
All of these raw materials are non-toxic and environmentally-friendly.
313 314
315 316 317 318 319 320 321 322 323 324 325 326
Supplementary Table 5 ｜ Comparison among different battery systems and
327
vanadium RFB. Battery type
328
Volumetric energy density
Gravimetric energy density
Reference
Vanadium RFB
25~30 Wh L-1
25~30 Wh kg-1
[1]
AQDS/Br RFB
50 Wh L-1
50 Wh kg-1
[2]
Polymer based RFB
10 Wh L-1
No description
[3]
4-HO-TEMPO/MV RFB
43.2 Wh L-1
No description
[4]
This work
201 Wh L-1
149 Wh kg-1
329 330 331 332 333 334 335 336 337 338 339
Supplementary Methods:
340
Flow battery construction and electrochemical tests.
341
A symmetrical flow battery was assembled with Na-BP-TEGDME solutions in both
342
compartments. Nickel foams were used as current collectors, and Na-β"-Al2O3 was
343
used as the membrane. In detail, 3 M BP and 3M Na were dissolved in the catholyte,
344
while 3 M BP and 0.5 M Na were dissolved in the anolyte. The volume of each
345
electrolyte was 0.58 mL. The electrolytes were circulated with a peristaltic pump. The
346
charge/discharge test was conducted with a multi-channel potentiostat (Metrohm
347
Autolab, PGSTAT302N) in an argon-filled glove box. The current was 1.0 mA.
348
A prototype flow battery of Na2S8∣BASE∣Na-BP-TEGDME was assembled with a
349
piece of Na-β"-Al2O3 as the membrane. The catholyte was 0.2 M Na2S8 dissolved in
350
0.5 M NaSO3CF3-DMSO catholyte, and the anolyte was 3 M Na-BP-TEGDME. The
351
electrolytes were circulated with a peristaltic pump. Charge/discharge test was
352
conducted under a constant current of 0.5 mA with a multi-channel potentiostat
353
(Metrohm Autolab, PGSTAT302N) in an argon-filled glove box.
354
Chemical titration.
355
The solubility of Na in the BP-DME solution was determined by a chemical titration.
356
In detail, an excessive Na metal was added into 5 M BP-DME solutions for several
357
days to ensure that the solution was saturated (named as Na saturated BP-DME
358
solution). Then, 1 mL Na saturated BP-DME solution was pipetted to react with 1
359
mL distill water (note that NaOH was produced in this reaction, which can be titrated
360
by an acid). After complete reaction, the solution was titrated by 0.225 mL HCl
361
(Aldrich, 38% with density of 1.18 g cm-3: 12.3 mol L-1).
362
calculate the solubility of Na in BP-DME is 5 M.
From this result, we can
363 364
Supplementary References:
365
1. Li, L., Kim, S., Wang, W., Yang, Z, G., et al. A Stable Vanadium Redox-Flow Battery with High
366
Energy Density for Large-Scale Energy Storage. Adv. Energy Mater. 1, 394-400 (2011).
367
2. Huskinson, B. et al. A metal-free organic-inorganic aqueous flow battery. Nature 505, 195-198
368
(2014).
369
3. Janoschka, T. et al. An aqueous, polymer-based redox-flow battery using non-corrosive, safe,
370
and low-cost materials. Nature 527, 78-81 (2015).
371
4. Liu, T., Wei, X., Nie, Z. et al. A Total Organic Aqueous Redox Flow Battery Employing a Low Cost
372
and Sustainable Methyl Viologen Anolyte and 4-HO-TEMPO Catholyte. Adv. Energy Mater. 6,
373
1501449(2015).
374
