SNarayanan_E-MRS_Presentation Fall2022_E5.3.pptx

SNarayanan_E-MRS_Presentation Fall2022_E5.3

1. Effect of current density on SEI evolution in “anode-free” all-solid-state next-generation Li ion batteries Sudarshan Narayanan*, Mauro Pasta Postdoctoral Research Assistant, University of Oxford Sep 20, 2022 Presentation No. : E.5.3 [email protected]

2. Solid state electrolytes and Li anode 2 Shift to all-solid-state batteries (ASSB) https://www.solvay.com/en/innovation/science-solutions/fast-charging-safe-batteries http://energy.mit.edu/news/doubling-battery-power-consumer-electronics/ Non-flammable, non-volatile, wide temperature range  Better safety High ionic conductivity with near-unity t Li+  Better power capability Potentially enabling Li metal  Higher energy density Towards thin Li metal anode

3. Issues with Li metal anode 3 Narayanan et al., Current Opinion in Solid State & Materials Science 26 (2) 100978 ( 2021)

4. Need for interface characterisation 4 Key aspects of ASSB attributed to Li-metal/solid electrolyte (SE) interface: Critical current density of battery related to interfacial voids and lithium dendrites Formation of dendrites associated with wetting and mechanical properties of Li-metal Composition of interfacial reaction products contribute to impedance and overall ionic conductivity Mauro Pasta  et al  2020  J. Phys. Energy   2  032008

5. Key questions to address 5 How does the Li metal – Solid electrolyte interface evolve during plating/stripping? Role of interfacial chemistry – reaction products, SEI? Effect of kinetics on electrochemical processes? Development of in situ or operando characterization techniques? Electrochemistry Impedance evolution Li plating-stripping efficiency XPS (Surface Chemistry) In-situ Li deposition Operando interface evolution SE – Li 6 PS 5 Cl (Argyrodite – sulphide)

6. XPS – Characterization modes 6 PHI 5000 VersaProbe III XPS Techniques: XPS, UPS, LEIPS, GCIB Instrument capabilities “In-operando” plating

7. “Operando” XPS spectral evolution – Li 1s 7 Dependence of metallic Li component on “ plating kinetics” Faster deposition  greater Li-metal fraction Slower deposition  greater “SEI” fraction * XPS spectra charge-referenced to adventitious C at 284.8 eV, Cl 2p 3/2 at 198.5 eV Narayanan et al., “Effect of current density on the Li – Li 6 PS 5 Cl solid electrolyte interphase”, Under Review , ChemRxiv (2022)

8. “Operando” XPS spectral evolution – P 2p 8 Dependence of interphasial chemistry on “ plating kinetics” Faster deposition  faster reduction to Li 3 P Slower deposition  slow reduction to Li 3 P (through partially reduced Li x P ) * XPS spectra charge-referenced to adventitious C at 284.8 eV, Cl 2p 3/2 at 198.5 eV Narayanan et al., “Effect of current density on the Li – Li 6 PS 5 Cl solid electrolyte interphase”, Under Review , ChemRxiv (2022)

9. Stability of decomposition products 9 Partially reduced Li x P species still present even after 24 hours inside the XPS chamber Li x P also observed to be remain buried within the interface, from synchrotron XPS measurements (Diamond Light Source) High-energy synchrotron XPS (DLS, I09 beamline) Narayanan et al., “Effect of current density on the Li – Li 6 PS 5 Cl solid electrolyte interphase”, Under Review , ChemRxiv (2022)

10. Electrochemical evolution of solid-state cell 10 Narayanan et al., “Effect of current density on the Li – Li 6 PS 5 Cl solid electrolyte interphase”, Under Review , ChemRxiv (2022)

11. Electrochemical evolution of solid-state cell 11 Narayanan et al., “Effect of current density on the Li – Li 6 PS 5 Cl solid electrolyte interphase”, Under Review , ChemRxiv (2022) “Li-free” anode configuration solid-state cell XPS “operando” Li plating configuration

12. Prior evidence, and implications? 12 Interface potential distribution profiles – Finite Element Simulations Bare Li metal Li metal with Li 3 P surface layer Wu et al., Adv. Funct. Mater. 2020, 30, 2000831

13. SEI evolution – Mechanism 13 SEI evolution Current density dependence of SEI chemistry Uniform, homogeneous Li 3 P-rich SEI at high current densities Tune charge-discharge protocols to engineer interface? Narayanan et al., “Effect of current density on the Li – Li 6 PS 5 Cl solid electrolyte interphase”, Under Review , ChemRxiv (2022)

14. Acknowledgments 14 Funding: Nissan Motor Co. Ltd. (NML) Japan Faraday Institution – SOLBAT Project Innovate UK – LiMHiT Project People: Pasta group at University of Oxford Dr. Ulderico Ulissi (previously Nissan UK, currently RhoMotion Ltd.) Nissan Motors Ltd. (NML – UK and Japan)

15. Thank you! Questions? Contact: [email protected]

16. Morphological evolution 16 Courtesy: Yvonne Chart (Helios PFIB) Schlenker et al. , ACS Appl. Mater. Interfaces  2020, 12, 17, 20012-20025 Li Cl ToF -SIMS of plated Li on Li 6 PS 5 Cl More uniform distribution of plated Li at higher current densities “Boundary region” surrounding Li seeds representing interface is visibly larger for Li plated at low current densities – likely indicative of “thicker” SEI Narayanan et al., “Effect of current density on the Li – Li 6 PS 5 Cl solid electrolyte interphase”, Under Review , ChemRxiv (2022)

17. This study (2kV) (~18 nm est. thick.) This study (4kV) (~18 nm est. thick.) 55 eV ( LPSCl ) 53.5 eV (SEI) 52.5 eV (Li ) XPS spectra comparison – Li 1s 17 Dependence of metallic Li component on “ deposition energetics” Slower deposition  greater “SEI” fraction Faster deposition  greater Li-metal fraction XPS spectra fitted to 3 distinct Li-species  Li LPSCl , Li ”SEI ” and Li S. Wenzel et al. Solid State Ionics 318 (2018) 102–112 Wenzel et al. in-situ (4kV) (literature) ~ 55 mins @ 0.25 nm/min (13.75 nm est. thick.) 52.5 eV XPS spectra charge-referenced to adventitious C at 284.8 eV. Li thickness estimated from intensity attenuation of Cu 2p peak in Li sputtered simultaneously on Cu foil * * * ~7 nm

18. Detection of Li 3 P 18 S. Wenzel et al. Solid State Ionics 318 (2018) 102–112 Li 3 P, Li 2 S and LiCl  expected reaction products at Li metal–Li 6 PS 5 Cl interface Wenzel et al. in-situ (4kV) (literature) ~ 60 mins @ 0.25 nm/min (13.75 nm est. thick.) This study (2kV) (~18 nm est. thick.) This study (4kV) (~18 nm est. thick.) Dependence of interfacial chemistry on “ deposition energetics” Slower deposition  gradual reduction to Li 3 P (through intermediary partially reduced Li x P ) Faster deposition  faster reduction to Li 3 P ~126.5 eV (Li 3 P) XPS spectra charge-referenced to adventitious C at 284.8 eV. Li thickness estimated from intensity attenuation of Cu 2p peak in Li sputtered simultaneously on Cu foil

19. Solid state electrolytes (SE) 19 Critical current density is an index for high power capability of Li-Metal cell High ionic conductivity  higher critical current density (typically) Sulfides – good practical choice despite poor electrochemical stability High ionic conductivity, robust and relatively easier to scale-up Li | SE interface evolution not well studied  required for feasibility studies Bachman et al., Chem. Rev.  2016, 116, 1, 140–162 Bonnick et al., J. Mater. Chem. A , 2019, 7 , 24173-24179 Richards et al., Chem. Mater.  2016 , 28, 1, 266–273