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Supplementary Information

Revealing Electrolyte Oxidation via Carbonate Dehydrogenation

on Ni-based Oxides in Li-ion Batteries by in situ Fourier

Transform Infrared Spectroscopy

Yirui Zhang a,†,*, Yu Katayama b,c,†, Ryoichi Tatara b, Livia Giordano a,b, Yang Yu d, Dimitrios Fraggedakis

e, Jame Guangwen Sun a, Filippo Maglia f, Roland Jung f, Martin Z. Bazant e,g, Yang Shao-Horn a,b,d,*

a Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139,

USA

b Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA 02139,

USA

c Department of Applied Chemistry, Graduate School of Sciences and Technology for Innovation,

Yamaguchi University, Ube 755-8611, Japan

d Department of Material Science and Engineering, Massachusetts Institute of Technology, Cambridge,

MA 02139, USA

e Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139,

USA

f BMW Group, Petuelring 130, 80788 München, Germany

g Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA

† These authors contributed equally to this work.

Corresponding Authors:

* Yirui Zhang (yirui@mit.edu)

* Yang Shao-Horn (shaohorn@mit.edu)

Electronic Supplementary Material (ESI) for Energy & Environmental Science.This journal is © The Royal Society of Chemistry 2019

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Figure S1. IR spectra and electrochemical measurement of 1.5 M LiPF6 / EC electrolyte on Pt (without oxides). (a) ATR spectrum of EC with 1.5 M LiPF6 electrolyte measured with a Ge prism. (b)

Linear sweep voltammetry of EC with 1.5 M LiPF6, with voltage range of 3.1 VLi to 4.8 VLi. Pt works as

the positive electrode and Li is the negative electrode. The scan rate is 0.12 mV/s. (c) In-situ FTIR spectra

on Pt surface, during oxidation sweep in 1.5 M LiPF6 in EC. (d) The difference spectra of C=O region,

where the reference spectrum is the one at OCV.

Figure S2. In-situ FTIR spectra on NMC811 surface during galvanostatic charging in 1.5 M LiPF6

/ EC from OCV (3.3 VLi) to 4.4 VLi. In situ cell was galvanostatically charged at 27.5 mA/g.

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Figure S3. In-situ FTIR spectra on NMC811 surface during charging in 1.5 M LiPF6 / EC from OCV (3.3 VLi) to 4.8 VLi. In situ cell was galvanostatically charged at 27.5 mA/g. (a) Voltage profile

during NMC811 charging in 1.5 M LiPF6 / EC, with voltage up to 4.8 VLi. (b) In-situ FTIR difference

spectra for C=O stretching region (in red) on NMC811 surface during charging in 1.5 M LiPF6 / EC

electrolyte, and ATR spectra for 1.5 M LiPF6 in EC and 1.5 M LiPF6 in EC/VC (1:1) electrolyte solution

(in black). (c) Peak ratio of VC to EC, which continues to increase during charging. (d) DFT computed

spectra for EC-derived oligomers with EC-like rings intact (C=O stretching region).

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Figure S4. IR spectra and electrochemical measurement of LP57 on Pt (without oxides). (a) ATR

spectrum of LP57 electrolyte (measured with a Ge prism). (b) Linear sweep voltammetry of LP57, with

voltage range of 3 VLi to 4.8 VLi. Pt works as the positive electrode and Li is the negative electrode. The

scan rate is 0.12 mV/s. (c) In-situ FTIR spectra on Pt surface, during oxidation sweep in LP57. (d) The

difference spectra of C=O region, where the reference spectrum is the one at OCV.

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Figure S5. IR spectra and electrochemical measurement of 1 M LiPF6 / EMC electrolyte on Pt

(without oxides). (a) ATR spectrum of EMC (black), and 1 M LiPF6 / EMC electrolyte (red) measured

with a Ge prism. (b) Linear sweep voltammetry of 1 M LiPF6 / EMC, with voltage range of 3 VLi to 4.8

VLi. Pt works as the positive electrode and Li is the negative electrode. The scan rate is 0.12 mV/s. (c) In-

situ FTIR spectra on Pt surface, during oxidation sweep in 1 M LiPF6 / EMC. (d) The difference spectra

of C=O region, where the reference spectrum is the one at OCV.

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Figure S6. In-situ FTIR spectra on NMC811 surface upon 1st cycle galvanostatic charging in LP57.

Cell was galvanostatically charged at 27.5 mA/g.

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Figure S7. In situ FT-IR measurements on NMC811 surfaces in LP57 upon first cycle discharging to 2 VLi. (a) Voltage profile during discharge. In situ FT-IR cell was galvanostatically discharged at

-27.5 mA/g. (b) In situ FT-IR difference spectra in C=O stretching region (in blue), and ATR spectra

(in black) for LP57 and LP57/VC solutions (1:1).

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Figure S8. In-situ FTIR spectra on NMC111 surface upon 1st cycle galvanostatic charging in LP57.

Cell was galvanostatically charged at 27.5 mA/g.

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Figure S9. In-situ FTIR measurements on NMC111 surfaces in LP57 upon 3rd cycle charging to 4.8 VLi. Voltage profile during NMC111 charged in LP57. In situ FTIR cell was galvanostatically charged at

27.5 mA/g. In situ FTIR difference spectra in C=O stretching region (in red) on NMC111 surface during

charging in LP57 electrolyte, and ATR spectra (in black) for LP57 and LP57/VC solutions (1:1).

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Figure S10. In-situ FTIR measurements on NMC622 surfaces in LP57 upon first cycle charging to 4.8 VLi. Voltage profile during NMC622 charged in LP57. In situ FTIR cell was galvanostatically charged

at 27.5 mA/g. In situ FTIR difference spectra in C=O stretching region (in red) on NMC622 surface

during charging in LP57 electrolyte, and ATR spectra (in black) for LP57 and LP57/VC solutions (1:1).

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Figure S11. In-situ FTIR spectra on NMC622 surface during galvanostatic charging in LP57 (for

the 3rd cycle). Cell was galvanostatically charged at 27.5 mA/g.

Figure S12. In-situ FTIR spectra on Al2O3-coated NMC622 surface during galvanostatic charging

in LP57 (for the 3rd cycle). Cell was galvanostatically charged at 27.5 mA/g.

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Figure S13. ATR spectra for EC/EMC electrolytes with different LiPF6 concentrations. With

increasing the salt LiPF6 concentration from 1M to ~3M, free EC and free EMC decreased in amount,

while Li+-coordinated EC and Li+-EMC increased.

Figure S14. In-situ FTIR spectra on NMC811 surface during galvanostatic charging in

EMC/EC/3.1M LiPF6 concentrated electrolyte. Cell was galvanostatically charged at 27.5 mA/g.

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Figure S15. In-situ FTIR spectra on NMC811 surface during galvanostatic charging in

EMC/EC/1M LiClO4 electrolyte. Cell was galvanostatically charged at 27.5 mA/g.

Figure S16. EIS measurement on NMC811 composite electrode in 1 M LiPF6/EMC. (a) Charging

profile. (b) Nyquist plot and (c) enlarged Nyquist plot at different voltages. Frequency dependence of (d)

phase shift, (e) imaginary impedance, and (f) absolute impedance.

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Figure S17. EIS measurement on NMC811 composite electrode in LiPF6/EC. (a) Charging profile.

(b) Nyquist plot and (c) enlarged Nyquist plot at different voltages. Frequency dependence of (d) phase

shift, (e) imaginary impedance, and (f) absolute impedance.

Figure S18. EIS measurement on NMC811 composite electrode in LP57. (a) Charging profile. (b)

Nyquist plot and (c) enlarged Nyquist plot at different voltages. Frequency dependence of (d) phase shift,

(e) imaginary impedance, and (f) absolute impedance.

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Figure S19. EIS measurement on NMC811 composite electrode in 1M LiClO4 / EMC / EC. (a)

Charging profile. (b) Nyquist plot and (c) enlarged Nyquist plot at different voltages. Frequency

dependence of (d) phase shift, (e) imaginary impedance, and (f) absolute impedance.

Figure S20. EIS measurement on NMC111 composite electrode in LP57. (a) Charging profile. (b)

Nyquist plot and (c) enlarged Nyquist plot at different voltages. Frequency dependence of (d) phase shift,

(e) imaginary impedance, and (f) absolute impedance.

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Figure S21. EIS measurement on NMC622 composite electrode in LP57. (a) Charging profile. (b)

Nyquist plot and (c) enlarged Nyquist plot at different voltages. Frequency dependence of (d) phase shift,

(e) imaginary impedance, and (f) absolute impedance.

Figure S22. EIS measurement on NMC811 composite electrode in EMC/EC/3.1M LiPF6 concentrated electrolyte. (a) Charging profile. (b) Nyquist plot. Frequency dependence of (c) phase shift,

(d) imaginary impedance, and (e) absolute impedance.

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Figure S23. SEM image on NMC111, NMC622 and NMC811 particles.

Figure S24. Summary of charging time to reach 4.8 VLi during first cycle for in situ cells. The

electrode loadings were all around 6.5 mg/cm2, with areas all 78.5 mm2 (10 mm in diameter). In situ FT-

IR cells were galvanostatically charged at 27.5 mA/g, with voltage cutoffs all 4.8 VLi. 10 hours of charging

corresponds to 100% SOC (based on charge capacity of 275 mAh/g).