Improving the Cyclic Stability of LiNi_0.5Mn_1.5O₄ Cathode by Modifying the Interface Film with 8‐Hydroxyquinoline

Abstract

Abstract8‐Hydroxyquinoline (8‐HDQN) is used as a bifunctional film‐forming additive to improve the capacity retention of Li/LiNi0.5Mn1.5O4 (LNMO) cell. Electrochemical analysis and ex‐situ analysis prove that 8‐HDQN can preferentially oxidize on the surface LNMO cathode to modify the Cathode Electrolyte Interface (CEI) film. The modified film effectively reduces the oxidation reaction of the electrolyte and the increase of polarization during the cycle. The CEI film derived from 8‐HDQN also inhibits the dissolution of transition metals ions from the LNMO electrode, and reduces the self‐discharge of the Li/ LNMO cell. Moreover, 8‐HDQN can also reduce the side reaction of PF5 by coordination with PF5 to improve the thermal stability of the electrolyte.

Counteracting Thermal Degradation of Lipf6-Based Electrolyte with Additives or Lithium Salts: A Gas Analysis Revealing the Impact of Nmc

“…Typically, three methods are implemented to prove directly or indirectly the formation of a complex between PF 5 and the chosen molecules: i) A visual inspection. In the literature, some PF 5 -complexing additives were reported to prevent the electrolyte from turning brown when stored at elevated temperatures [10,[23][24][25][26], this color being associated with the electrolyte degradation. However, color inspection is insufficient in our opinion as an absence of coloring does not mean an absence of degradation.…”

“…-iii) An XPS analysis of the SEI/CEI. Complex formation prevents PF 5 from reacting with the basic components of the SEI/CEI, thus reducing the amount of LiF visible in the F1s spectra [23,[27][28][29]. The interpretation of the results can be tricky when the additive contains a fluorine atom and has a limited electrochemical stability window.…”