Ex situ and operando study of LiCoO2 thin films by Raman spectroscopy: Thermal and electrochemical properties. (18th July 2019)

• Record Type: Journal Article
• Authors: Le Van‐Jodin, Lucie; Rouchon, Denis; Le, Van‐Hoan; Chevalier, Isabelle; Brun, Jean; Secouard, Christophe
• Is Part Of: Journal of Raman spectroscopy. Volume 50:Number 10(2019)
• Page Start: 1594
• Page End: 1601
• Publication Date: 2019-07-18
• Subjects: electrode materials -- in situ Raman -- phase transitions -- physical vapor deposition -- thin films; Raman spectroscopy -- Periodicals; 535.846
• DOI: 10.1002/jrs.5669
• Languages: English
• ISSNs: 0377-0486

Abstract

Abstract: Lithiated transition metal oxides are active materials used as positive electrode in lithium ion cells thanks to their high capacity and air stability when. Amongst lithiated oxides, LiCoO2 is the most commonly and practically used due to its high‐specific energy and its excellent cycle life. This work focuses on phase transformation of LiCoO2 thin films during the annealing step and during the cycling life. The formation of unwanted products is highlighted by an innovative method: in situ Raman analysis. During the annealing used to transform the almost amorphous as‐deposited LiCoO2 into the rhombohedral structure useful for electrochemical cycling, the formation of Co3 O4 has been observed. The second studied phase transformation is due to the electrochemical cycling and highlights the kinetics of the structure change. The study was done by comparing ex situ and operando results and highlights the main advantages of operando analysis: more data in a shorter time and the ability to assess the time dependence of phenomena. Abstract : In this Raman spectroscopic study, we examined the most useful material for batteries: LiCoO2 . Comparing ex situ and operando Raman characterization, it highlights some new results about the structural change of LiCoO2 in thin film microbatteries. We studied two types of structural changes: first, during LiCoO2 annealing just after deposition to reach the right structure for electrochemical applications (HT‐LiCoO2 ) and second, the time dependence of the structural change during the electrochemical cycling.