Designing mesostructured iron (II) fluorides with a stable in situ polymer electrolyte interface for high-energy-density lithium-ion batteries

• Published in: eScience (Beijing) Vol. 4; no. 1; p. 100188
• Main Authors: Sun, Lidong, Wang, Yong, Kong, Lingchen, Chen, Shaoshan, Peng, Cong, Zheng, Jiahui, Li, Yu, Feng, Wei
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.02.2024; KeAi Communications Co. Ltd
• Subjects: In situ polymer electrolyte; Iron fluorides; Lithium-ion batteries; Mesoporous structure; Lithium-ion batteries; Mesoporous structure; In situ polymer electrolyte; Iron fluorides
• ISSN: 2667-1417; 2667-1417
• DOI: 10.1016/j.esci.2023.100188

As high-energy cathode materials, conversion-type metal fluorides provide a prospective pathway for developing next-generation lithium-ion batteries. However, they suffer from severe performance decay owing to continuous structural destruction and active material dissolution upon cycling, which worsen at elevated temperatures. Here, we design a novel FeF2 cathode with in situ polymerized solid-state electrolyte systems to enhance the cycling ability of metal fluorides at 60 °C. Novel FeF2 with a mesoporous structure (meso-FeF2) improves Li+ diffusion and relieves the volume change that typically occurs during the alternating conversion reactions. The structural stability of the meso-FeF2 cathode is strengthened by an in situ polymerized solid-state electrolyte, which prevents the pulverization and ion dissolution that are inevitable for conventional liquid electrolytes. Under the double action of this in situ polymerized solid-state electrolyte and the meso-FeF2’s mesoporous structure, the active material maintains an intact SEI layer and part of the mesoporous structure after long charge–discharge cycling, showing excellent cycling stability at high temperatures. [Display omitted] •A mesostructured FeF2 material (meso-FeF2) has been designed and synthesized for the first time.•A reasonable reaction mechanism for the meso-FeF2 is proposed.•The meso-FeF2 and in situ polymerized solid-state electrolytes guarantee homogeneous SEI formation, achieving the highly efficient and stable conversion of active materials.•High energy density and high cycling performance of meso-FeF2 materials at high temperatures are achieved.