title: Facet-Dependent Thermal Instability in LiCoO2.
abstract: Thermal runaways triggered by the oxygen release from oxide cathode materials pose a major safety concern for widespread application of lithium ion batteries. Utilizing in situ aberration-corrected scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) at high temperatures, we show that oxygen release from LixCoO2cathode crystals is occurring at the surface of particles. We correlated this local oxygen evolution from the LixCoO2structure with local phase transitions spanning from layered to spinel and then to rock salt structure upon exposure to elevated temperatures. Ab initio molecular dynamics simulations (AIMD) results show that oxygen release is highly dependent on LixCoO2facet orientation. While the [001] facets are stable at 300 °C, oxygen release is observed from the [012] and [104] facets, where under-coordinated oxygen atoms from the delithiated structures can combine and eventually evolve as O2. The novel understanding that emerges from the present study provides in-depth insights into the thermal runaway mechanism of Li-ion batteries and can assist the design and fabrication of cathode crystals with the most thermally stable facets.
authors.affiliation: Mechanical and Industrial Engineering Department, University of Illinois at Chicago , Chicago, Illinois 60607, United States.
authors.forename: Soroosh
authors.identifier: 0000-0003-0441-9231
authors.initials: S
authors.lastname: Sharifi-Asl
authors.affiliation: Department of Chemical Engineering, Texas A&M University , College Station, Texas 77843, United States.
authors.forename: Fernando A
authors.initials: FA
authors.lastname: Soto
authors.affiliation: Materials Genome Institute, Shanghai University , Shanghai 200444, China.
authors.forename: Anmin
authors.identifier: 0000-0002-0180-1366
authors.initials: A
authors.lastname: Nie
authors.affiliation: Mechanical and Industrial Engineering Department, University of Illinois at Chicago , Chicago, Illinois 60607, United States.|Chemical Science and Engineering Division, Argonne National Laboratory , 9700 S. Cass Avenue, Argonne, Illinois 60439, United States.
authors.forename: Yifei
authors.initials: Y
authors.lastname: Yuan
authors.affiliation: Mechanical and Industrial Engineering Department, University of Illinois at Chicago , Chicago, Illinois 60607, United States.
authors.forename: Hasti
authors.initials: H
authors.lastname: Asayesh-Ardakani
authors.affiliation: Mechanical and Industrial Engineering Department, University of Illinois at Chicago , Chicago, Illinois 60607, United States.
authors.forename: Tara
authors.initials: T
authors.lastname: Foroozan
authors.affiliation: Mechanical and Industrial Engineering Department, University of Illinois at Chicago , Chicago, Illinois 60607, United States.
authors.forename: Vitaliy
authors.initials: V
authors.lastname: Yurkiv
authors.affiliation: Mechanical and Industrial Engineering Department, University of Illinois at Chicago , Chicago, Illinois 60607, United States.
authors.forename: Boao
authors.initials: B
authors.lastname: Song
authors.affiliation: Mechanical and Industrial Engineering Department, University of Illinois at Chicago , Chicago, Illinois 60607, United States.
authors.forename: Farzad
authors.initials: F
authors.lastname: Mashayek
authors.affiliation: Department of Physics, University of Illinois at Chicago , Chicago, Illinois 60607, United States.
authors.forename: Robert F
authors.initials: RF
authors.lastname: Klie
authors.affiliation: Chemical Science and Engineering Division, Argonne National Laboratory , 9700 S. Cass Avenue, Argonne, Illinois 60439, United States.
authors.forename: Khalil
authors.identifier: 0000-0001-9206-3719
authors.initials: K
authors.lastname: Amine
authors.affiliation: Chemical Science and Engineering Division, Argonne National Laboratory , 9700 S. Cass Avenue, Argonne, Illinois 60439, United States.
authors.forename: Jun
authors.identifier: 0000-0003-0858-8577
authors.initials: J
authors.lastname: Lu
authors.affiliation: Department of Chemical Engineering, Texas A&M University , College Station, Texas 77843, United States.
authors.forename: Perla B
authors.identifier: 0000-0002-2358-3910
authors.initials: PB
authors.lastname: Balbuena
authors.affiliation: Mechanical and Industrial Engineering Department, University of Illinois at Chicago , Chicago, Illinois 60607, United States.
authors.forename: Reza
authors.identifier: 0000-0002-7744-4780
authors.initials: R
authors.lastname: Shahbazian-Yassar
keywords: LiCoO2 degradation; Lithium-ion batteries; ab initio molecular dynamics; in situ STEM/EELS; oxygen release; thermal stability