Supplementary Material for

Critical aspects of Membrane-Free Aqueous Battery based on two immiscible neutral electrolytes

Table S1. Fitting parameters of equation (1), TLL and α values.

A B C TLL α94.866

7-

0.599733.2988 · 10-4 33.85 0.769

1

Table S2. Comparison of the performance of the battery with literature studies based on the same active species families

Anolyte Catholyte ConcentrationCell

Voltage (V)

CE(%)

EE(%)

Cycles Ref

MV OH-TEMPO 0.5M in NaCl 1.25 99 62 100 [1]

BTMAP-Viologen

NMe-TEMPO

0.5M in NaCl 1.38 99 60 500 [2]

[(NPr)2TTz]Br4

NMe-TEMPO

0.2M in NaCl 1.44 99 68.6 300 [3]

MV NMe-TEMPO

2M in NaCl 1.4 99 65 100 [4]

Vio-TEMP Vio-TEMP 25mM in NaCl 1.06 NA NA NA [5]

MVTEMPO polymer

0.37M in NaCl 1.3 99 93 125 [6]

Viologen polymer

TEMPO polymer

0.4M in NaCl 1.1 75 NA 100 [7]

MVTEMPO polymer

0.5M in NaCl 1.3 98 NA 2500 [8]

MV TEMPO20mM in IL+Na2SO4

1.35 70 70 20 [9]

MV TEMPO0.1M in

PEG+Na2SO41.25 82 70 550

This work

[1] T. Liu, X.Wei, Z. Nie, V.Sprenkle, W.Wang, A Total Organic Aqueous Redox Flow Battery Employing a Low Cost and Sustainable Methyl Viologen Anolyte and 4 HO TEMPO ‐ ‐Catholyte, Adv. Energy Mater. 6 (2016) 1501449. https://doi.org/10.1002/aenm.201501449

[2] B.Hu, Y.Tang, J. Luo, G. Grove, Y. Guo and T. Leo Liu, Improved radical stability of viologen anolytes in aqueous organic redox flow batteries, Chem. Commun. 54 (2018) 6871-6874. https://doi.org/10.1039/C8CC02336K

[3] J. Luo, B.Hu, C. Debruler, T. Leo Liu, A π Conjugation Extended Viologen as a Two Electron Storage Anolyte for Total Organic Aqueous Redox Flow Batteries, Angew. Chem.‐ ‐ Int. Ed. 57 (2018) 231 –235. https://doi.org/10.1002/anie.201710517

[4] T. Janoschka, N. Martin, M.D. Hager, U.S. Schubert, An Aqueous Redox Flow Battery with High Capacity and Power: The TEMPTMA/MV System, Angew. ‐ Chem. Int. Ed. 55 (2016) 14427 –14430. https://doi.org/10.1002/anie.201606472

[5] T. Janoschka, C. Friebe, M.D. Hager, N. Martin, U.S. Schubert, An Approach Toward Replacing Vanadium: A Single Organic Molecule for the Anode and Cathode of an Aqueous Redox Flow Battery, ChemistryOpen, 6 (2017) 216 – 220. https://doi.org/10.1002/open.201600155‐

[6] Y.Liu, S. Lu, S. Chen, H. Wang, J. Zhang, Y. Xiang, A Sustainable Redox Flow Battery with Alizarin-Based Aqueous Organic Electrolyte, Chem. Mater. 31 (2019) 7987-7999. https://doi.org/10.1021/acsaem.8b01512

[7] K.Hatakeyama-Sato, T.Nagano, S.Noguchi, Y. Sugai, J.Du, H. Nishide, K. Oyaizu, Hydrophilic Organic Redox-Active Polymer Nanoparticles for Higher Energy Density Flow Batteries, ACS Appl. Polym. Mater. 1 (2019) 188−196. https://doi.org/10.1021/acsapm.8b00074

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[8]T.Hagemann, J. Winsberg, M. Grube, , I. Nischang, T. Janoschka, N. Martin, M.D. Hager, U.S. Schubert, An aqueous all-organic redox-flow battery employing a (2,2,6,6-tetramethylpiperidin-1-yl)oxyl-containing polymer as catholyte and dimethyl viologen dichloride as anolyte, Journal of Power Sources 378 (2018) 546-554. https://doi.org/10.1016/j.jpowsour.2017.09.007

[9] P.Navalpotro, C. M. S. S. Neves, J. Palma, M. G. Freire, J. A. P. Coutinho, R. Marcilla, Pioneering Use of Ionic Liquid Based Aqueous Biphasic Systems as Membrane Free‐ ‐ Batteries Adv. Sci. 2018, 1800576. https://doi.org/10.1002/advs.201800576.

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Fig. S1. (a) CV of the bottom phase of PEG-based ABS containing 20 mM of MV. CVs of the top phase of PEG-based ABS containing 20 mM of (b) QUI, (c) AQ2S, (d) H2Q and (e) TEMPO.

4

-0.5 0.0 0.5 1.0-0.04

-0.02

0.00

0.02

0.04

0.06

Cu

rrent

(mA)

Potential (V vs Ag/AgCl)

d

Fig. S2. Rotating Disk Electrode Experiments. (a), (b) Linear Sweep Voltammetry (LSV) and Levich plot at 10 mV·s-1 of 5 mM MV in bottom phase. (c), (d) LSV and Levich plot at 10 mV·s-1

of 5 mM TEMPO in top phase.

5

Fig. S3. Polarization curves of battery and catholyte, anolyte and interface potential profiles at 20 % SOC. a) charge polarization and (b) discharge polarization.

6

Fig. S4. Self-discharge experiment (starting at 20 %SOC) consisting of monitoring the evolution of the OCV of the battery over time.

7

Fig. S5. Discharge battery voltage (20% SOC): (a) Consecutive discharge experiments at C and C/2; (b) Consecutive discharge experiments at 2C and C.

8