Open AccessTracking the Influence of Thermal Expansion and Oxygen Vacancies on the Thermal Stability of Ni‐Rich Layered Cathode Materials
Author(s) -
Lee Eunkang,
Muhammad Shoaib,
Kim Taewhan,
Kim Hyunchul,
Lee Wontae,
Yoon WonSub
Publication year - 2020
Publication title -
advanced science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.388
H-Index - 100
ISSN - 2198-3844
DOI - 10.1002/advs.201902413
Subject(s) - cathode , materials science , spinel , thermal stability , thermal expansion , lithium (medication) , thermal runaway , transition metal , oxygen , phase transition , ion , chemical engineering , battery (electricity) , chemical physics , composite material , metallurgy , chemistry , thermodynamics , physics , organic chemistry , engineering , medicine , power (physics) , biochemistry , endocrinology , catalysis
The ever‐growing demand for high‐energy lithium‐ion batteries in portable electronics and electric vehicles has triggered intensive research efforts over the past decade. An efficient strategy to boost the energy and power density of lithium‐ion batteries is to increase the Ni content in the cathode materials. However, a higher Ni content in the cathode materials gives rise to safety issues. Herein, thermal expansion and oxygen vacancies are proposed as new critical factors that affect the thermal stability of charged Ni‐rich cathode materials based on a systematic synchrotron‐based X‐ray study of Li 0.33 Ni 0.5+ x Co 0.2 Mn 0.3‐ x O 2 ( x = 0, 0.1, 0.2) cathode materials during a heating process. Charged cathode materials with higher Ni contents show larger thermal expansion, which accelerates transition metal migration to the Li layers. Oxygen vacancies are formed and accumulate mainly around Ni ions until the layered‐to‐spinel phase transition begins. The oxygen vacancies also facilitate transition metal migration to the Li layers. Thermal expansion and the presence of oxygen vacancies decrease the energy barrier for cation migration and facilitate the phase transitions in charged cathode materials during the heating process. These results provide valuable guidance for developing new cathode materials with improved safety characteristics.