What electrolyte for non-aqueous Na-ion batteries?
Transcript of What electrolyte for non-aqueous Na-ion batteries?
What electrolyte for non-aqueous Na-ion batteries?
Patrik Johansson
Patrik Johansson1,2, Ma Rosa Palacín2,3, Damien Monti1-3, Andrea Boschin1,2, Alexandre Ponrouch2,3, and Erlendur Jónsson1
1) Applied Physics, Chalmers University of Technology, SE-412 96 Göteborg, Sweden 2) Alistore-ERI
3) ICMAB-CSIC, Campus de la UAB, 08193 Bellaterra, Spain
1st Symposium on Na batteries by CIC EnergiGUNE Vitoria-Gasteiz Oct 16-17 2013
The Li-ion to Na-ion battery transition in materials
Patrik Johansson
New Electrode Mtrls: Anodes, Cathodes… !No Graphite Anodes! => No need to keep “the standard electrolyte” ≈1M LiPF6 in carbonates
New Electrolytes? Salts/Solvents/Additives/Concentrations etc possible… … but the basics stay the same
M. R. Palacin, Chem. Soc. Reviews 38 (2009) 2565
What electrolytes are being used for Na-ion? “Google research”
Patrik Johansson
Cathode studies Anode studies
Salts
NaClO4 > NaPF6 > NaTf
NaClO4 >> NaPF6 > NaFSI
Solvents PC, EC/DXC, TEGDME
EC/DXC, PC
Electrolytes 1M NaClO4 in PC 1M NaPF6 in EC/DXC
Notable new materials and concepts – arising from electrolyte focused groups: i) Not VC, but FEC as SEI forming additive (2 wt%) (FEC:DEC 1:1) ii) NaFSI/KFSI (56:44) eutectic - mp 61 °C iii) Tailoring conductivity and viscosity; single => binary => ternary solvent mix
What electrolyte should we pick?
Salt = NaClO4 !?
Na+-conducting organic electrolytes: single solvent to binary solvent mix
Patrik Johansson
A. Ponrouch et al., Energy Environ. Sci. (2012)
Macroscopic observations: i)Salt anion of minor importance for conductivity & viscosity (@ RT (20 °C) & 1M) Why not ση ≈ k? What about tNa
+? ii)Conductivities ≈ LP30 possible – other parameters decide choice (Tstab, ESW, etc) What electrolyte to pick? => NaPF6 in EC:PC
Solvent = PC Salt = NaClO4
Na+-conducting organic electrolytes: binary to ternary solvent mix
Patrik Johansson
A. Ponrouch et al., Energy Environ. Sci. 6 (2013) 2361. DOI:10.1039/c3ee41379a
Macroscopic & molecular observations: i)ση ≈ k ii)EC:PC:DMC (0.45:0.45:0.1) chosen based on s iii)DMC acts indirectly – very minor Na+ interaction iv)EC and TFSI both interact with Na+
0.1
Basics of Li+ vs. Na+ solvation in organic solvents
Patrik Johansson
+ +
Facts and beliefs about Na-salt vs. Li-salt solvation: i) Na+ is more weakly solvated than Li+ => Na-salts are less soluble (?) ii) Na-salts use same basic anions: weakly cation coordinating, delocalized iii) Na-salts have lower lattice energies => Na-salts are more soluble (?) iv) Na+ has more ligands and higher CN (?) v) Na+ has other ligand preferences (?)
Consequences of Li+ vs. Na+ solvation in organic solvents: Gedanken example of M+ in PC
Patrik Johansson
+ +
E. Jónsson et al., in manuscript (2013)
Solvation of Na-salts: Modelling by MC + DFT
Patrik Johansson
E. Jónsson et al., Phys. Chem. Chem. Phys. 14 (2012) 10774. E. Jónsson et al., in manuscript (2013)
NaAn Na+ + An- DEd
=> ΔEdNa ≈ ΔEdLi * 0.80-085
=> ΔEsolvNa ≈ ΔEsolvLi * 0.80-0.85
Status Quo !?
Lots of details to be discovered…
+ +
Na+ + xEC + yDMC [Na(EC)x(DMC)y]+
DEsolv
Ionic liquids for Li+ and Na+ solvation
Patrik Johansson
Promises: - thermally and el. chem. stable - low (no) volatility - ”high” conductivities - excellent salt solubilities - variety - 1012! - ...
Problems: - high viscosity => low conductivity - cost - manufacturing(?) - nature of charge carriers? - ...
Pyr14FSI
Use of ILs as matrices?!
Solvation of LiTFSI in Ionic Liquid matrices
Patrik Johansson
LiTFSI in XMITFSI: IR + Raman + DFT
J. C. Lassègues et al., J. Phys. Chem A 113 (2009) 305.
0
0.2
0.4
0.6
0.8
1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
EMI 25C
EMI 80°CBMI 25CBMMI 25C
BMMI 80C
1 - A/A0
m/C0
520560600640680
Ab
sorb
ance
Wavenumber/cm-1
618
571
515
651
b
c
e
a
f
g
d
581
601
615
658 520
581
571
Exp. IR
DFT IR Wavenumbers [cm-1]
74X cm-1 Raman band
… and existing on a NMR time-scale… S. Duluard et al., J. Raman Spectrosc. (2008)
[Li(TFSI)2]- CN=4
Solvation of NaTFSI in Ionic Liquid matrices
Patrik Johansson
[Na(TFSI)3]2- CN= 5-6
(MD [Wipff] => CN=6.3)
D. Monti et al., J. Power Sources 245 (2014) 630.
A comparison of organic solvent vs. ILs for Li+ vs. Na+-salt solvation
Patrik Johansson
Org. Solv.
+ -
-
Li+An-
-
Charge of Carriers:
0 -2 -1 +1
Org. Solv.
IL (TFSI)
IL
(TFSI)
+
-
- +
+
Na+An-
- +
+ -
- +
+
+ +
Summary & Open Questions Remaining…
Patrik Johansson
- Changing Li+ to Na+ induce interaction & coordination changes = f(salt conc) => What is the optimal Na-salt concentration? => Are there safety implications by the coordination changes?
=> What solvent(s) should be chosen? => What is the Na+ coordination?
- Are there any especially promising Na-salt anions?
=> DFT studies give “No…” => New/old anions to (re-)discover?
- Matrices other than organic solvents: => IL-based electrolytes – profound changes – beneficial or not?
=> SPE-based electrolytes – minor changes – beneficial or not?
Patrik Johansson
Acknowledgements
Prof. Per Jacobsson Lic. Sc. Erlendur Jónsson MSc. Damien Monti MSc. Andrea Boschin - poster #5
International Collaborators Prof. Michel Armand CIC EnergiGUNE Prof. Jean-Claude Lassègues Univ. Bordeaux I Dr. Ma Rosa Palacin ICMAB – CSIC Dr. Alexandre Ponrouch ICMAB – CSIC
Funding
Thank you for your attention!