Kinetically-controlled formation of Fe2O3 nanoshells and its potential in Lithium-ion batteries

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2022-04, Vol.433, p.133188, Article 133188
• Main Authors: Lin, Xi-Jie, Sun, Yong-Gang, Guo, Si-Jie, Zhang, Si-Dong, Liu, Yuan, Cao, An-Min
• Format: Article
• Language: English
• Subjects: Fe2O3 nanoshells; Kinetic control; LiNi0.5Mn1.5O4; Lithium-ion batteries; Surface coating
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2021.133188

•A wet chemical synthetic protocol was developed to build uniform Fe2O3 nanoshells.•Hexamethylenetetramine was critical in modulating the precipitation kinetics.•This protocol was successful in building Fe2O3 coatings around various substrates.•A nondestructive surface treatment could be achieved by this anhydrous protocol.•The cycling performance of LiNi0.5Mn1.5O4 greatly improved after Fe2O3 coating. The construction of uniform metal oxide nanoshells has been widely considered as an effective protocol for the protection of high energy cathodes in lithium-ion batteries. Solution-based synthetic routes have recently become feasible to build such protective shells, but are challenged by the incidental damage to cathodes since an acidic condition is usually needed to prevent the fast precipitation of active metal cations in aqueous solutions. Here, by switching to anhydrous solution, we demonstrate the possibility of creating Fe2O3 nanoshells by taking advantage of the much-reduced ionic activity of Fe3+ in ethanol without the involvement of corrosive environment. Hexamethylenetetramine is identified as an efficient growth controller, whose slow decomposition is critical to modulate the growth kinetics of the formed metal hydroxide precursor, forming core@shell structures with the shell thickness controlled at nanometer accuracy. This synthetic protocol is successful in building uniform Fe2O3 coatings around various substrates, particularly LiNi0.5Mn1.5O4, a well-known high energy cathode whose applications are challenged by poor cycling performance related to the high working voltage. This surface treatment for LiNi0.5Mn1.5O4 is effective in improving the electrochemical behavior of the cathode with a successful suppression of its structural degradation as well as a substantial improvement in its high temperature stability.