Electrode - Electrolyte Interface Studies in Lithium Batteries

2,569 views

Published on

Compilation of studies conducted at the Institut des Matériaux de Nantes under the supervision of Dr. Dominique Guyomard between 2008 and 2012.
Focused on solid-state NMR to characterize interphases between positive electrode and electrolyte.

Published in: Technology, Business
0 Comments
4 Likes
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
2,569
On SlideShare
0
From Embeds
0
Number of Embeds
23
Actions
Shares
0
Downloads
184
Comments
0
Likes
4
Embeds 0
No embeds

No notes for slide

Electrode - Electrolyte Interface Studies in Lithium Batteries

  1. 1. Electrode/Electrolyte Interface Studies in Lithium Batteries Marine Cuisinier University of Waterloo, Canada Nicolas Dupré, Dominique Guyomard Institut des Matériaux Jean Rouxel ‐ Université de Nantes, France Kouta Suzuki, Masaaki Hirayama, Ryoji Kanno Tokyo Institute of Technology, Japan 1/29
  2. 2. Li-ion & related challenges Energy (Wh/kg, Wh/l) Power (W/kg, W/l) Power (W / kg) HEV 1000 PHEV, power tools Li-ion Safety Cost EV Toxicity Ni-MH 100 Life Reactivity at interfaces Pb-acid btw. electrodes & electrolyte 10 10 100 1000 Safety Energy (Wh/kg) Long term cyclability Energy Autonomy Power Rate, acceleration 2/33
  3. 3. Aging mechanisms of cathode materials gas evolution electrolyte decomposition DMC O O EC dissolution O surface layer formation O O re-precipitation of new phases migration of soluble species F Li F P F F F F ROCO2Li OPF2(RO)nF O LixPOyFz LiF Adapted from J. Vetter et al., J. Power Sources 147 (2005) 269 3/33
  4. 4. Table of contents 1 CHARACTERIZATION METHODS   Review of interface characterization methods MAS NMR applied to surface species analysis 2 EXEMPLES: LINI0.5MN0.5O2/ELECTROLYTE INTERPHASE   Aging upon storage in LiPF6 electrolyte Aging upon cycling in LiPF6 and LiBOB modified electrolyte 3 CASE OF THE LIFEPO4/ELECTROLYTE INTERPHASE   Intrinsic interphasial behavior Surface aging upon storage: characterization and control towards improved electrochemical performance 4 GENERAL CONCLUSION & PERSPECTIVES 4/29
  5. 5. Classical interface characterization methods A strategy for R&D of Li and Li-ion batteries. Study of Electrodes Li, Li-C anodes and LixMOy cathodes. NMR Surface Chemistry in situ & ex situ FTIR, XPS, EDAX, EQCM Interfacial properties EIS, B.E.T. (surface area) Morphology in situ AFM (SEM) Structural analysis in situ & ex situ XRD (SEM) Correlation Performance Fast tests for cycling efficiency FTIR (GCPL) XPS MAS NMR 50 40 30 Solution studies Electrochemical windows, thermal stability, redox processes: CV, in situ FTIR, EQCM, EIS, DTA Optimization of electrolyte solutions 20 10 Published items each year Electroanalytical behavior of Li insertion compounds PITT, EIS, SSCV Testing in practical cells (coin cells and AA cells) 19 9 19 4 9 19 5 9 19 6 9 19 7 9 19 8 9 20 9 0 20 0 0 20 1 0 20 2 0 20 3 0 20 4 0 20 5 0 20 6 0 20 7 0 20 8 0 20 9 1 20 0 1 20 1 1 20 2 13 0 Publication year From Reuters, Web of Knowledge 5/33
  6. 6. Review of interface studies by NMR < 20 studies in the literature on « passivation layer on LiB materials »  Suitable for: 1H, 7Li, 13C, 19F and 31P in the interphase… or 23Na ! 6/33
  7. 7. 7Li NMR: Li-electron dipolar interaction Coupling between nuclear spin and electronic spin (paramagnetic ions) Distance between Li and paramagnetic center 0 1 H en  µe .Dij . 3 4 r Mn4+ t2g (unpaired electron spin) O Through space q B0 r Li (nuclear spin) 7/33
  8. 8. Using 7Li MAS NMR to selectively DETECT the interphase T2 para Distance between Li and paramagnetic center B0 0 1 H en  µe .Dij . 3 4 r y If r ↓ Hen ↑ x Surface species = diamagnetic (Li2CO3, LiF, LixOyPFz etc…) π/2 pulse Bulk Li Free Induction Decay Surface Time Longer T2 Mn then T2 ↓ t0 Li Short T2 acquisition T2para DEAD TIME (5-50 s) before acquisition of data REMOVE Li-bulk SIGNAL 8/33
  9. 9. Using 7Li MAS NMR to study electrode/interphase interactions 7Li, 500MHz, 14kHz FWHM  LiNi0.5Mn0.5O2 with surface Li2CO3 No dead time If r ↓ Hen ↑ then T2 ↓ If µe ↑ Hen ↑ then T2 ↓ a Bulk Dipolar interaction Dipolar interaction 0 ppm b Diamagnetic surface species Dead time 1 T2 2V 4.5 V Surface Li2CO3 c Li2CO3 powder 3000 2000 1000 40 0  (ppm) -1000 -2000 20 0 -20 -40 7  Li / ppmm Ménétrier, M. et al. Electrochem. And Solid State Lett., 2004, 7(6), A140. Dupré, N. et al. J. Mat. Chem., 2008, 18, 4266 DIPOLAR INTERACTION THICKNESS / INTIMACY of the interphase with the bulk9/33
  10. 10. integrated intensity / NS / RG integrated intensity / NS / RG (a. u.) Using MAS NMR to QUANTIFY the interphase 7Li NMR 50 40 LiFePO4 20 and 31P NMR spectra calibration curves LiMn1.5Ni0.5O4 30 7Li, 19F Si -1 y = 4.26 10 x 10 LiF / LiPF6 calibration 0 0 25 50 75 100 diamagnetic Li (µmol) 19F 5 NMR 4 LiMn1.5Ni0.5 O4 3 LiFePO4 Si Works for interphases grown on ≠ electrode materials: LiMn0.5Ni0.5O2 , LiFePO4 , Si -2 y = 6.38 10 x LiF calibration 2 -2 y = 2.80 10 x 1 From known amounts of diamagnetic nuclei (LiF, LiPF6) LiPF 6 calibration Absolute quantification of interphasial [Li], [F], [P] in mmol.g-1 or mmol.m-² 0 0 25 50 75 100 diamagnetic F (µmol) 10/33
  11. 11. (Li-alkylcarbonates) O -1 diamagnetic Li or F (mmol.g ) Interpretation of quantitative NMR results 7Li, 19F NMR Total Li Li 1.4 7 1.2 Li+ O (7Li 1.4 O O Li (Li2CO3) O Li in organic 1.0 ~ Total Li (7Li) – LiF (19F) ? F / PF 19 F / LiF 1.0 R Li NMR) 19 O 1.2 0.8 0.8 0.6 Fluorophosphates (19F NMR) 0.4 POF3/PO2F2-/ PO3F2- 0.6 0.4 0.2 0.2 0.0 0.0 OX1 RED1 OX5 RED5 OX20 RED20 O O F P R O F or F P O Li F LiF (19F NMR) Charge state O O O O n O O Non lithiated organic species remain invisible to our NMR experiments 11/33
  12. 12. Need for COMPLEMENTARY analytical tools 0 n Diamagnetic interphases m LiMn0.5Ni0.5O2 interphase formation Electrode active material NMR Electrode activ XPS Diamagnetic interphases Electrode active material LiPF6 electrolyte decomposition Electrode active material Electrode active material In situ EIS TEM/EELS Z’’/Ω 5 NMR Rinterfacial -50 Nyquist plot -25 Rel 0 Brookhaven Nat. Lab. 25 50 Z’/Ω 75 100 12/33
  13. 13. Table of contents 1 CHARACTERIZATION METHODS   Review of interface characterization methods MAS NMR applied to surface species analysis 2 EXAMPLES: LINI0.5MN0.5O2/ELECTROLYTE INTERPHASE   Aging upon storage in LiPF6 electrolyte Aging upon cycling in LiPF6 and LiBOB modified electrolyte 3 CASE OF THE LIFEPO4/ELECTROLYTE INTERPHASE   Intrinsic interphasial behavior Surface aging upon storage: characterization and control towards improved electrochemical performance 4 GENERAL CONCLUSION & PERSPECTIVES 13/29
  14. 14. Example 1: aging of the LiNi1/2Mn1/2O2 / LiPF6 interphase upon storage (SEM) 7Li 1 month NMR 19F 0 ppm NMR -205 ppm LiF 3 days 3 days 1 hour 5 min. 1 min. 30 sec. 1 µm (a) Pristine 1000 (b) 500 0 7  Li / ppm   1 µm normalized / NS / RG /m 1 µm normalized / NS / RG /m 2 weeks  -500 -1000 (c) 200 0 -200 -400  19F / ppm Soaking at RT in LiPF6 1M, EC:DMC (1:1) Surface “film” observation by SEM 19F: LiF only 14/33
  15. 15. mmol (Li or F) / g LMN Example 1: aging of the LiNi1/2Mn1/2O2 / LiPF6 interphase upon storage (NMR vs XPS) 0.4 7Li, 19F NMR 0.3 7 Li NMR One month 0.2 19 0.1 0.0 Li in organic = Total Li (7Li) – LiF (19F) 0 10 20 30 F NMR 40 50 60 300 400 500 600 700 Contact time (min) XPS F1s XPS C1s LiF CC/CH 1 hour LiF only  XPS: LiF screening 26% by Li-containing 16% organic species 5 min. 13% CO CO3 CO 2 1 month LixPFy LixPOyFz 1 month 1 hour 5 min. Contact time (h) 26% 33% 37%  19F: 15/33
  16. 16. Example 1: aging of the LiNi1/2Mn1/2O2 / LiPF6 interphase upon storage (EELS) EELS 100 %F F-K atomic % O-K 8 8 7 6 5 4 3 Mn-L Ni-L 2,3 500 2,3 600 700 800 900 Energy Loss (eV) 80 60 40 20 % Mn %O 0 8 7 6 5 4 3 spot number Interphase growth scenario: LiPF6 O PF5 + LiF O O O Li+ O O R LMN½ 5 Salt decomposition Solvents decomposition Contact time 16/33
  17. 17. 200 180 LiPF6 1M Coulombic 160 220 ) 220 -1 180 120 160 140 0 5 100 5 15 Cycle number20 10 15 100 st 1 ox Z" / .mg -2 25 th 5 ox 90 Q charge 20 Q discharge 15 80 Coulombic efficiency th 10 60 5 50 0 10 5 10 Cycle number 15 20 15 / .mg-2 20 Z' 25 50 120 20 0 20 ox 70 0 140 Cycle number 30 60 160 100 Coulombic efficiency (%) -2 0 10 180 30 30 25 20 15 10 5 0 Charge transfer resistance () 120 70 200 Z" / .mg Capacity (mA.h.g 200 140 Capacity (mA.h.g ) Q charge Q discharge 125 R 4.5 V ct st charge:  R 2V 100 1 parasitic electrochemical process Impedance ↑ : only Rct ↑ ct 80 75 efficiency LiPF 0.9M + LiBOB 0.1M  6 100 5 90 Q charge Q discharge Charge transfer resistance () ) 100 -1 Capacity (mA.h.g -1 220 Coulombic efficiency (%) Example 2: aging of the LiNi1/2Mn1/2O2 / LiPF6 interphase upon cycling (1) 0 5 10 Q charge Q discharge 50 25 0 5 15 20 Cycle number 125 10 15 20 Cycle number Rct 4.5 V Rct 2 V st 100 1 ox th 5 ox 75 th 20 ox 50 25 5 0 10 15 20 5 Z' / .mg -2 25 30 10 Cycle number 15 20 17/33
  18. 18. RED1 0.3 140 120 0.2 100 10 15 0 0.1 20 5 Cycle number 0.0 0.0 OX5 RED5 OX20 RED1 OX5 PRISTINEOX1 RED20 Charge state Li+ O O R O F P O Li F 70 60 50 100 RED 1 Q charge Q discharge 75 Coulombic efficiency 10 R902 V ct 80 70 50 OX 1 60 25 Cycle number 200 15 0 0 2019 5 50 -200 10 125 100 75 50 25  F / ppm Cycle number -400 0 15 0.0 RED5 OX20 RED20 Charge state O 80 100 Rct 4.5 V NMR Charge transfer resistance () 0.1 5 0 0.4 Coulombic efficiency 160 125 Coulombic efficiency (%) 100 0.2 ) -1 0.2 90 19F normalized / NS / RG /m 120 0.5 Q charge 180 Q discharge Charge transfer resistance () 0.4 0.3 140 200 100 Coulombic efficiency (%) 0.6 0.4 160 0.6 T2(Li) (ms) 0.8 0.5 Capacity (mA.h.g 1.0 ) -1 1.2 F / LiF 19 200 F / PF 7 180 Li 220 0.6 T2(Li) (ms) 220 19 1.4 Capacity (mA.h.g LiF PF diamagnetic Li/F (mmol/g) Example 2: aging of the LiNi1/2Mn1/2O2 / LiPF6 interphase upon cycling (2)   Appearance of fluorophosphates Electrochemical formation of the interphase? Indirect electrochemical oxidation: oxygen transfer from the oxide surface to the solvent molecules S.-W. Song et al., JES, 151, A1162 (2004) 18/33
  19. 19. 1.4 1.2 1.0 0.6 19 F / LiF 19 F / PF 7 Li 0.4 0.8 0.3 0.6 0.2 0.4 0.2 0.1 0.0 0.0 PRISTINEOX1 RED1 OX5 Li-poor interphase: LiF + non-lithiated species  T2(Li): No evolution of the AM /interphase intimacy  Stable (resistive) LiF-based interphase + growing non-lithiated (PEO type + phosphates)  0.5 T2(Li) (ms) diamagnetic Li/F (mmol/g) Example 2: aging of the LiNi1/2Mn1/2O2 / LiPF6 interphase upon cycling (3) Li-free organic RED5 OX20 RED20 Charge state Organic species Fluorophosphates LiF O O O O n O O O LMN½ M. Cuisinier et al. Solid State Nucl. Magn. Reson. 42, 51 (2011) LMN½ F P R O F 19/33
  20. 20. Example 3: aging of the LiNi1/2Mn1/2O2 / LiPF6 interphase upon cycling (effect of LiBOB additive) Cathode protecting agent Mn-containing insoluble surface layer [*] No LiBOB LiBOB 30 19F / LiF 19F / PF 7Li 1.2 1.2 1.0 0.8 0.6 0.6 0.4 0.4 20 15 10 0.2 0.0 PRISTINE OX1 RED1 OX5 RED5 OX20 5 0.0 0.2 BOB-1ox BOB-5ox BOB-20ox 25 1.0 0.8 200 1.4 Z'' / (mmol/g) diamagnetic LiOhm 1.4 Z'' / Ohm diamagnetic Li (mmol/g) 1.4 0 RED20 Charge state 1.2 150 5 10 15 20 Z' / Ohm 25 30 19F / LiF 19F / PF 7Li PF6-1ox PF6-5ox PF6-20ox 1.2 1.0 1.0 0.8 0.8 100 0.6 0.6 0.4 0.4 50 0.2 0.0 0 1.4 0.2 0 PRISTINE OX1 RED1 0 50 0.0 OX5 100 RED5 OX20 RED20 150 200 Z' / Ohm Charge state Composition of interphase is different: Presence of Li in org. species / fluorophosphates Less resistive interphase « good » interphase [*] Chen, Z. et al., Electrochim. Acta 51 (2006) 3322. ↑ electrochemical performance 20/33
  21. 21. Table of contents 1 CHARACTERIZATION METHODS   Review of interface characterization methods MAS NMR applied to surface species analysis 2 EXEMPLES: LINI0.5MN0.5O2/ELECTROLYTE INTERPHASE   Aging upon storage in LiPF6 electrolyte Aging upon cycling in LiPF6 and LiBOB modified electrolyte 3 CASE OF THE LIFEPO4/ELECTROLYTE INTERPHASE    Interphase dynamics upon voltage variations Interphase modeling using ideal 2D films Interphase evolution upon extended cycling 4 GENERAL CONCLUSION & PERSPECTIVES 21/29
  22. 22. -1 diamagnetic Li or F (mmol.g ) Evolution of the LiFePO4 interface with voltage 7 3.0 Li 3.0 19 F/PF 19 2.5 F/LiF 2.5 2.0 2.0 1.5 1.5 1.0 1.0 0.5 0.5 0.0 0.0 4.0 V 4V 4.5 V 4.5V 2.0 V 2V 2.7 V 2.7V 2.7 V 2.7V Charge state  7Li/19F: clarify XPS  stable inorganic interphase + fluctuating organic species FePO4 F. Croce et aL., J. Power Sources, 43 (1993) 9 Oxidized state 4.5 V 4.5V Interphase model: Solid Polymer Layer Li-organic species Fluorophosphates LiF LiFePO4 Reduced state 22/33
  23. 23. Modeling the interphase architecture (1) 100 Elemental percentage (%) EELS %O %F % Fe 80 60 40 20 -20 0 20 40 60 80 100 Distance from the surface (nm) F-K O-K #12: 14 nm #11: 19 nm #10: 18 nm Fe L2,3 500 550 600 650 700 #6: AM 750 800 Energy loss (eV)  EELS: Any multi-layered model is abusive ! (at least on powder samples) 23/33
  24. 24. a- oriented LiFePO4 thin films d / g·cm-3 Model surface: a- oriented LiFePO4 thin films Thickness l / nm 20.36 - Roughness t / nm glue Pulsed Laser (a) (b) Deposition: 20-80nm thick LiFePO4 4epitaxial LiFePO film on SrTiO3 (010) 1.33 1.06 0.55 1.08 690 520 525 530 535 540 545 550 555 700 710 720 730 energy loss (eV) energy loss (eV) (d)Pristine film:Surface LiFePO4 SrTiO3 (c) structurally homogeneous layer O 740  Possibility to monitor fine surface Density 2.11 3.62 5.12 structure changes upon Li (de)intercalation d / g·cm-3 Thickness a- oriented LiFePO4 thin films SrTiO substrate 1.33 20.36 Roughness t / nm 1.06 0.55 l / nm 3 - TEM-EELS 1.08 O-K Fe-L2,3 energy loss (e Pulsed (d)Pristine film: structurally hom (b) Ideal 2D surface Deposition: 20-80nm = model interphase  Possibility to monitor fine thick LiFePO4 4epitaxial LiFePO structure changes upon film on SrTiO3 (010) Subjected to storage in LiPF6 Li (d Pulsed Laser electrolyte and cycling Pristine film: structurally homogeneous Deposition: 320-80nm SrTiO substrate  Validate to monitor fine surface  Possibility the interphase model? thick LiFePO epitaxial glue Laser 520 525 530 535 540 54 520 525 530 535 540 545 550 555 energy loss (eV) 4 film on SrTiO3 (010) 690 700 710 720 730 740 energy loss (eV) structure changes upon Li (de)intercalation Hirayama et al., Electrochemistry (Tokyo), 5 (2010) 413 24/33
  25. 25. Modelingthe interphase architecture Modeling the interphase architecture (2) XPS Electron detector Electron detector X-ray X-ray XPS ) (θ in ) . s (θ n 3λ si . λ 3 ) (θ s o .c 3λ θ Penetration depth = 3λ.cos(θ) Penetration depth = 3λ.sin(θ) with λ ~λ~27Å with 22 Å θ θ varied from 0° to 60° I(θ)= Iinf . exp(-d/λ.cosθ) 3λ 3λ Bulk Bulk Surface Surface Interphase depth profile: ln C(Fe 2p1/2) 1.6 1.4 1.2 0.8 surface 5 Average λ (inelastic mean free path) is inaccurate ! air contact 4.5V 1st charge 2.5V 1st discharge 0.6 0.4 0.2 1.0 0.8 -0.2 -d 0 0.6 LiF PF CO CO2 Confirms NMR and EELS results: 1.0 1.2 1.4 1.6 1.8 2.0 Inner LiF, covered by fluorophosphates 1/cosq -1 and a dynamic Solid Polymer Layer (SPL) 0.4  d (nm) 4 Pristine 3 1 0.44 1st ox. 4.5 V 3.5 bulk dried PO Fe 4.5 V 2.5 V 4.5V 1st charge 2.5V 1st discharge 4.5 LN(P-O) LN(surface/bulk)  1 d, the interphase thickness 1.4 1st 1.2 1.4 1.6 1/cos(q) red 2.5 V 0.25 1.8 % 26 pristine 4.5V 2.5V 0.8 nm 1.7 nm 1.2 nm Voltage dependance of the interphase thickness 25/33
  26. 26. 2 Modeling the interphase architecture (3) XPS LiF F 1s ) ((θ) θ sn i . cλos .3 3λ X-ray k 1.0 θ C.P.S Electron detector 1.2 θ 3λ Bulk q = 60° q = 55° q = 48° q = 37° q = 0° 0.8 LixPOyFz 0.6 0.4 0.2 0.0 Surface -0.2 C %(60) 1.0 C %(0) 1.2 690 686 684 682 P Binding energy (eV) 1st Ox 4.5 V 0.8 688 0.6 CH2CO2Li, ROCO2Li 0.4 1st Red 2.5 V 0.2 0.0 OPF2OMe, OPF2(OCH2CH2)nF LiF LiFePO4 FePO4 -0.2 PO Fe LiF PF CO2 CO -- Inner interphase: stable / inorganic Outer interphase : dynamic / polymeric   26/33
  27. 27. 100 180 100 1 ox 4.5 V 5 ox 4.5 V 20 ox 4.5 V 1 red 2V 5 red 2V 20 red 2V Pristine - 4.5 V 80 Stable impedance, 60 no resistive film 140 120 100 Pristine - 2 V 80 60 -Z'' /  160 -Z'' /  Discharge capacity (mA.h.g -1 ) Interphase data upon cycling for bare LFP 5 40 40 80 0 20 40 60 80 20 1 20 20 20 250 Hz 100 100 Hz 0 cycle number 0 0 20 40 60 80 100 0 Z' /  -1 diamagnetic Li or F (mmol.g ) 7Li, 19F 0.5 NMR Accumulation of 0.5 interphase species 7 Li F / PF 19 F / LiF 19 0.4 0.4 0.3 0.3 0.2 0.2 0.1 0.1 0.0 0.0 1 ox 1 red 5 ox 5 red 20 ox 20 red OX1 RED1 OX5 RED5 Charge state 1 5 5 kHz Charge transfer 6 kHz OX20 RED20 20 40 60 80 100 Z' /  Stable performance vs Li No resistive film Lots of Li outside LiF, in LixPOyFz (?), in Li-organic (1H NMR, XPS) O F P O Li F O Li+ O O R 27/33
  28. 28. 0.0 x 20 red 0.4 0.3 0.3 7 0.2 0.2 0.1 0.1  T2(Li) (ms) -1 T2(Li) (ms) 0.4 0.0 0.4 0.5 0.3 NMR 0.2 7Li 0.1 Interphasial Li (mmol.g ) Interphase growth scenario for bare LFP 0.0 1 ox 1 red 5 ox 5 red 20 ox 20 red     Stable performance vs Li No resistive film Li-rich porous interphase Interphase growth by stacking Li-organic species Fluorophosphates LiF FePO4 M. Cuisinier et al. J. Power Sources, 224, 50 (2013) T2(Li): decreasing intimacy Signal integration: accumulation of surface Li Non blocking interphase, But no passivation: Oxidized state Li+ Li+ LiFePO4 Reduced state 28/33
  29. 29. The case of LiFePO4: summary vs. LiMn1/2Ni1/2O2  Stable performance require a Li-rich organic interphase  How to stop Li consumption in it? STABLE REVERSIBLE “BREATHING” FP LFP STABLE PERFORMANCE  Poor performance of our LMN material might be assigned to a “bad” interphase: no Li mobility, growing Li-free matrix on Organic species LiF-rich inner interphase Fluorophosphates Li-free organic O O O O n LiF O O O LMN½ M. Cuisinier et al. J. Power Sources, 224, 50 (2013) M. Cuisinier et al. Solid State Nucl. Magn. Reson. 42, 51 (2011) LMN½ F P R O F 29/33
  30. 30. Table of contents 1 CHARACTERIZATION METHODS   Review of interface characterization methods MAS NMR applied to surface species analysis 2 EXEMPLES: LINI0.5MN0.5O2/ELECTROLYTE INTERPHASE   Aging upon storage in LiPF6 electrolyte Aging upon cycling in LiPF6 and LiBOB modified electrolyte 3 CASE OF THE LIFEPO4/ELECTROLYTE INTERPHASE   Intrinsic interphasial behavior Surface aging upon storage: characterization and control towards improved electrochemical performance 4 GENERAL CONCLUSION & PERSPECTIVES 30/29
  31. 31. GENERAL CONCLUSION & PERSPECTIVES Battery performance is driven by surface chemistry  Need for powerful analytical tools  Validation of NMR for interphase studies (perspectives)  Use for full cells and negatives: Si or intermetallics  Use for the exploration of Na interphasial chemistry (NaClO4  NaTFSI?) even more critical at the negative  T1/T2(Li) mapping = principle of MRI !  use to localize liquid/confined/solid state Li in the battery 31/33
  32. 32. GENERAL CONCLUSION & PERSPECTIVES Battery performance is driven by surface chemistry  Interphase evolves upon voltage variations, depending on the AM  No general formation mechanism  Complex architecture/composition  conducting properties  Good interphase = SEI-like      Li-O-rich to be conducting Dense to passivate the AM surface Thin to limit Li consumption Not straightforward  tailor with additives or new electrolytes NMR for the diagnostic evaluation of detrimental phenomena  Cross-talk between the negative and positive interphases  Need for parallel studies on both electrodes 32/33
  33. 33. Acknowledgments Nicolas Dupré, Dominique Guyomard but also L. Lajaunie, J.-F. Martin, P. Moreau, Z.-L. Wang (co-workers) R. Kanno, M. Hirayama, K. Suzuki, S. Taminato (Tokyo Tech collab.) K. Edström (Uppsala), T. Épicier (INSA Lyon), L. Croguennec, M. Ménétrier & A. Wattiaux (ICMCB), J.-M. Tarascon (LRCS), J. Cabana (LBNL) for fruitful discussions and experimental contributions MESR, METSA (funding) marine.cuisinier@gmail.com nicolas.dupre@cnrs-imn.fr 33/33

×