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SUMMARY:Microelectrochemical in situ observation of battery electrodes
DTSTART:20170330T103000
DTEND:20170330T113000
DTSTAMP:20260429T150850Z
UID:cac3dc777be99fc8e72ad6f88dab54a72304b5ee15d1061221411e9f
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Dr. Gunther Wittstock\nCarl von Ossietzky University of 
 Oldenburg\nGermany\nIn our society Li ion batteries are widely used. Inten
 sive research is conducted on next generation batteries such as metal-air 
 batteries. The requirements of high energy density dictate the use of very
  high (oxidizing) or very low (reducing) potential. These extreme potentia
 ls can cause molecular compounds to undergo electron transfer reactions at
  the interfaces. This is well documented for lithium-ion batteries\, where
  a solid electrolyte interphase (SEI) between the lithiated graphite elect
 rode and the electrolyte is formed by the decomposition of electrolyte com
 ponents mainly during the first charging process. This layer is critical f
 or the performance and safety of the Li ion batteries [1]. This talk will 
 review a number of approaches to understand charge transport across SEI by
  using concepts of microelectrochemistry in particular scanning electroche
 mical microscopy (SECM).\n            Characterization of the S
 EI is a challenge\, because of the variety of chemically similar component
 s and enclosed electrolyte species. Furthermore\, ex situ analysis of the 
 SEI requires separation and isolation of the SEI\, which may change the co
 ntent and the structure of the SEI [2]. Recently we used the feedback mode
  of scanning electrochemical microscopy (SECM) to investigate in situ the 
 electron transport at the lithiated graphite (Figure) [3]. 2\,5-di-tert-bu
 tyl-1\,4-dimethoxy benzene was identified as a useful SECM mediator provid
 ing sufficient stability and sensitivity to study passivation properties o
 f SEI. All measurements were conducted under open circuit conditions of ch
 arged negative electrodes. The SECM results show gradual and significant s
 hort-term spatiotemporal changes of the SEI properties and demonstrate the
  dynamic and spontaneous behavior of SEI formation\, damage and reformatio
 n under open circuit conditions above lithiated graphite anodes. The resul
 ts emphasize that spatiotemporal changes of the passivating SEI properties
  are highly localized and occur preferentially in between the gaps of grap
 hite particles. Significant short-term spatiotemporal changes of the SEI p
 roperties clarifies that electrolyte reduction still occurs after SEI form
 ation at localized spots. This methodology has also been applied to highly
  ordered pyrolytic graphite [4]\, lithiated silicon [5]\, lithium metal [6
 ].\n            These examples are examples for intensive attem
 pts to use electrochemcial microprobes to assess in situ properties of int
 erfaces in modern batteries [7\, 8]. Using a related setup for the investi
 gation of nonaqueous lithium-air batteries\, the fate of oxygen reduction 
 products has been investigated. It shows that also during discharge consid
 erable amounts of superoxide diffuse into the organic electrolyte. Soluble
  intermediates were identified by reaction with selective fluorgenic dyes 
 and quantified by cyclic voltammetry at a microelectrode [9].\n \nImporta
 nt contributions of my PhD students Dr. H. Bülter\, Dr. P. Schwager\, E. 
 dos Santos Sardinha and cooperation partners from Fraunhofer IFAM (F. Pete
 rs\, Dr. D. Fensker\, Dr. J. Schwenzel) and TU Graz (Dr. M. Stenard\, Prof
 . Dr. M. Wilkening) are gratefully acknowledged. Funding for this research
  has been obtained by the State of Lower Saxony through the graduate progr
 am Energy Storage and Electromobility in Lower Saxony (GEENI) and the Cons
 elho Nacional de Desenvolvimento Científico e Tecnológico (Brazil for E.
 d.S.S.).\n \n[1] S. Krueger\, R. Kloepsch\, J. Li\, S. Nowak\, S. Passeri
 ni\, M. Winter\; J. Electrochem. Soc. 2013\, 160\, A542.\n[2] P. Verma\, P
 . Maire\, P. Novak\; Electrochim. Acta 2010\, 55\, 6332.\n[3] H. Bülter\,
  F. Peters\, J. Schwenzel\, G. Wittstock\; Angew. Chem. Int. Ed. 2014\, 53
 \, 10531.\n[4] H. Bülter\, F. Peters\, G. Wittstock\; Energy Technol. (We
 inheim\, Ger.) 2016\, 4\, 1486.\n[5] H. Bülter\, M. Stenard\, E. dos Sant
 os Sardinha\, J. Witt\, C. Dosche\, M. Wilkening\, G. Wittstock\; J. Elect
 rochem. Soc. 2016\, 163\, A504.\n[6] H. Bülter\, F. Peters\, J. Schwenzel
 \, G. Wittstock\; J. Electrochem. Soc. 2015\, 162\, A7024.\n[7] P. Schwage
 r\, H. Bülter\, I. Plettenberg\, G. Wittstock\; Energy Technol. (Weinheim
 \, Ger.) 2016\, 4\, 1472.\n[8] H. Bülter\, P. Schwager\, D. Fenske\, G. W
 ittstock\; Electrochim. Acta 2016\, 199\, 366.\n[9] P. Schwager\, S. Dongm
 o\, D. Fenske\, G. Wittstock\; Phys. Chem. Chem. Phys. 2016\, 18\, 10774.\
 n 
LOCATION:Zeuzier
STATUS:CONFIRMED
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