Improved Thermal Stability of Lithium‐Rich Layered Oxide by Fluorine Doping. Issue 1 (7th December 2017)

• Record Type: Journal Article
• Authors: Kapylou, Andrei; Song, Jay Hyok; Missiul, Aleksandr; Ham, Dong Jin; Kim, Dong Han; Moon, San; Park, Jin Hwan
• Is Part Of: Chemphyschem. Volume 19:Issue 1(2018)
• Page Start: 116
• Page End: 122
• Publication Date: 2017-12-07
• Subjects: doping -- electrochemistry -- fluorine -- layered compounds -- lithium; Chemistry, Physical and theoretical -- Periodicals; 541.05
• DOI: 10.1002/cphc.201700927
• Languages: English
• ISSNs: 1439-4235

Abstract

Abstract: The thermal stability of lithium‐rich layered oxide with the composition Li(Li1/6 Ni1/6 Co1/6 Mn1/2 )O2− x F x ( x= 0.00 and 0.05) is evaluated for use as a cathode material in lithium‐ion batteries. Thermogravimetric analysis, evolved gas analysis, and differential scanning calorimetry show that, upon fluorine doping, degradation of the lithium‐rich layered oxides commences at higher temperatures and the exothermic reaction is suppressed. Hot box tests also reveal that the prismatic cell with the fluorine‐doped powder does not explode, whereas that with the undoped one explodes at about 135 °C with a sudden temperature increase. XRD analysis indicates that fluorine doping imparts the lithium‐rich layered oxide with better thermal stability by mitigating oxygen release at elevated temperatures that cause an exothermic reaction with the electrolyte. The origin of the reduced oxygen release from the fluorinated lithium‐rich layered oxide is also discussed. Abstract : Stable when the heat is turned up ! Lithium‐ion batteries composed of normal lithium‐rich layered oxides (LLOs) explode at 135 °C, but those with fluorine‐doped LLOs are more thermally stable and do not explode. Reduced transition metals in fluorinated LLOs suppress the formation of unstable surface phases (see figure).