Unusual Stability of Acetonitrile-Based Superconcentrated. Electrolytes for Fast-Charging Lithium-Ion Batteries

Transcription

1 Supporting Information for Unusual Stability of Acetonitrile-Based Superconcentrated Electrolytes for Fast-Charging Lithium-Ion Batteries Yuki Yamada,, Keizo Furukawa, Keitaro Sodeyama,, Keisuke Kikuchi, Makoto Yaegashi, Yoshitaka Tateyama,,, and Atsuo Yamada,, * Department of Chemical System Engineering, The University of Tokyo, Tokyo , Japan Elements Strategy Initiative for Catalysts & Batteries (ESICB), Kyoto University, Kyoto , Japan International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Ibaraki , Japan PRESTO, Japan Science and Technology Agency (JST), Saitama , Japan Corresponding Author * yamada@chemsys.t.u-tokyo.ac.jp S1

2 Figure S1. Total energy profiles of (a) dilute (1-LiTFSA/43-AN, fully dissociated), (b) dilute (1- LiTFSA/43-AN, CIP), and (c) superconcentrated (10-LiTFSA/20-AN) solutions as the function of DFT-MD simulation step. The equilibrations with ca. 5 ps were carried out before the present equilibrium trajectories, which are not shown here. S2

3 mol dm 3 LiTFSA/AN Current / ma Potential / V vs. Li + /Li Ni plate 10 mv s 1 Figure S2. Cyclic voltammograms of a Ni plate in 4.2 mol dm 3 LiTFSA/AN solution. Scan rate was set at 10 mv s 1. The redox pair at around 0 V corresponds to lithium-metal deposition and dissolution. S3

4 3.0 mol dm 3 LiTFSA/AN 0.0 Current / ma Potential / V vs. Li + /Li Ni plate 10 mv s 1 Figure S3. Cyclic voltammograms of a Ni plate in 3.0 mol dm 3 LiTFSA/AN solution. Scan rate was set at 10 mv s 1. Lithium-metal deposition/dissolution reaction was thoroughly irreversible in this electrolyte. S4

5 mol dm 3 LiTFSA/AN Current / ma Pt plate 1 mv s Potential / V vs. Li + /Li Figure S4. Oxidative stability of 4.2 mol dm 3 LiTFSA/AN solution. Linear sweep voltammetry (1 mv s 1 ) was conducted at room temperature with a three-electrode cell employing a platinum plate as a working electrode and lithium metal foil as reference and counter electrodes. In addition to the enhanced reductive stability, the superconcentrated AN solution exhibits remarkably high oxidative stability up to ca. 5 V. S5

6 N1s S-N-S or cyanide O1s several O-containing groups Intensity / a.u. Intensity / a.u Binding energy / ev Binding energy / ev Figure S5. N 1s and O 1s spectra for the natural graphite electrode after one-cycle charge-discharge test at C/10 rate in 4.2 mol dm 3 LiTFSA/AN electrolyte. The peak at 399 ev in N 1s spectrum derives from S-N-S part or cyanide. In O 1s spectrum, various O-containing groups give a peak at almost the same binding energy in 532~533 ev and hence, no useful information was obtained. S6

7 Figure S6. PDOS of (a-b) dilute (1-LiTFSA/43-AN, fully dissociated), (c-d) dilute (1-LiTFSA/43- AN, CIP), and (e-f) superconcentrated (10-LiTFSA/20-AN) solutions with different snapshots in the DFT-MD trajectories. These PDOSs are qualitatively in the same alignment as those of Figs. 5a-c. S7

8 Figure S7. PDOS of (a) dilute (1-LiTFSA/43-AN, fully dissociated), (b) dilute (1-LiTFSA/43-AN, CIP), and (c) superconcentrated (10-LiTFSA/20-AN) solutions at 350K DFT-MD simulations as an investigation of different initial configuration convergence. These PDOSs qualitatively have the same alignment as those in Figs. 5a-c. S8

9 a) b) Figure S8 a) Charge-discharge curves of a natural graphite / lithium metal half cell with superconcentrated 4.2 mol dm 3 LiTFSA/AN electrolytes at various C-rates and 25 o C. Charge and discharge were conducted at the same C-rate without using a constant-voltage mode at both ends of charge and discharge. b) Reversible capacity of natural graphite in the two electrolytes at various C- rates and 25 o C. Charge (Li + de-intercalation) capacity was plotted. S9

10 Table S1 Physicochemical properties of LiFSA/AN solutions at 30 o C. concentration molar ratio density viscosity conductivity (mol dm 3 ) (AN/LiFSA) (g cm 3 ) (mpa s) (ms cm 1 ) S10

11 Voltage / V M LiFSA/AN 1st 2nd-3rd Capacity / mah g 1 Figure S9 Charge-discharge curves of a natural graphite / lithium metal half cell with superconcentrated 4.5 mol dm 3 LiFSA/AN electrolyte at C/20 rate and 25 o C. S11