Impact of Processing Conditions on Oxygen Vacancies in Ga-Doped Li7La3Zr2O12 Solid Electrolyte Using Tof-SIMS

Abstract

Currently a vast amount of research into fast lithium ion conductors is taking place for application into solid electrolytes. The most attractive compositions being from the garnet family with the chemical composition of Li7La3Zr2O12 [1]. LLZO has high lithium ion mobility at room temperature, a large electrochemical window which allows high voltage cathodes to be employed and good stability with lithium metal anodes. Typically, LLZO is doped at the lithium position with donor cations these include Al3+and Ga3+ which provide stability of the cubic crystal phase thus allowing Li+ mobility in three dimensions. The mobility for Ga-LLZO has been reported to be above 10-3 S.cm-1 [2], [3] this is the composition that will be mainly focused on in the poster. Preliminary investigations have shown that due to lithium loss during high processing temperatures oxygen vacancies are formed because of the charge compensation mechanism[4]. The quantification of oxygen vacancies as an affect of the processing conditions and it effect on the conductivity of oxygen and lithium ions have been investigated in this work using electrochemical impedance spectroscopy and cell cycling. The affect of different densification atmospheres (Ar, Vac, and O2) on oxygen vacancies are measured using 18O isotopic labelling coupled with the Time of Flight Secondary Ion Mass Spectrometer (ToF-SIMS) to assess which results in a higher degree of oxygen defects. This work will be correlated with lithium defect chemistry and mobility to understand the lithium critical current density for dendrite growth which are detrimental to battery life.