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SUMMARY:SNSS Seminar Series: Neutron Diffraction\, Speaker 2 - Non-equilib
 rium phases and cation mixing in Li-rich rock salt derived positive electr
 ode materials
DTSTART;VALUE=DATE-TIME:20210511T113000Z
DTEND;VALUE=DATE-TIME:20210511T120000Z
DTSTAMP;VALUE=DATE-TIME:20260528T085830Z
UID:indico-contribution-1074@lindico453.srv.lu.se
DESCRIPTION:Speakers: William Brant (Uppsala University)\nOften within the
  domain of inorganic chemistry synthesis\, focus is placed on obtaining id
 eal materials under equilibrium conditions in order to accurately study sp
 ecific phenomena. However\, while extremely valuable\, these studies often
  do not represent the real structures which are formed when materials are 
 utilized in an application or a device. This is particularly true in the c
 ase of electrode materials for rechargeable ion batteries where it is noto
 riously difficult to predict what phases are formed as electrochemical ext
 raction of charged ions proceeds far from the thermodynamically stable con
 figuration of a material. In this contribution I will present results from
  two different Li-rich rock salt derived oxide systems\, Li1+xTM1-xO2 (0 
 ≤ x ≤ ⅓\, TM= Mn\, Ni and Co) and Li2VO2F. Both compounds do not exh
 ibit ideal structures and the properties are intricately tied to the local
  cation configurations generated via non-equilibrium phase transitions.\nT
 he structure of lithium rich layered phases\, Li1+xTM1-xO2\, is complicate
 d by disorder which manifests over multiple length scales. At the atomic s
 cale Li and TM cations can order forming a superstructure\, this superstru
 cture allows for the appearance of stacking faults which extends beyond th
 e unit cell. Finally\, phase segregation of different ordered domains can 
 occur on the nano to micron length scale. The disorder present can vary si
 gnificantly even for a single composition depending upon the specific synt
 hesis conditions. These multiple metastable phases which exhibit near iden
 tical average structures has confounded research into these materials\, hi
 ndering an understanding of their anionic redox properties.\nLi2VO2F is a 
 metastable disordered rock salt structure which shows promise as a high ca
 pacity cathode material. However\, significant capacity fade during electr
 ochemical cycling impedes its implementation. Understanding the origin of 
 the capacity fade is challenging due to the reconstructive phase transitio
 n that occurs upon lithium extraction. One might expect that over time the
  structure converts to more thermodynamically stable structures that are l
 ess electrochemically active. However\, using a combination of X-ray and n
 eutron diffraction\, we demonstrate that this is not the case and that oth
 er crystalline metastable phases stabilise and grow over successive electr
 ochemical cycles.\n\nhttps://lindico453.srv.lu.se/event/214/contributions/
 1074/
LOCATION:
URL:https://lindico453.srv.lu.se/event/214/contributions/1074/
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