Hetero-Packing Nanostructures of Iron (III) Fluoride Nanocomposite Cathode for High-Rate and Long-Life Rechargeable Lithium-Ion Batteries

High-performance metal fluoride cathodes are crucial to design ultrahigh-capacity lithium metal batteries for taking part in the next-generation energy storage market. However, their insulating nature and sluggish reaction kinetics result in voltage hysteresis, low-rate capability, and rapid capacity degradation. Herein, a generalizable one-step melt synthesis approach is reported to construct hetero-packing nanostructures of FeF 3 @C-Asphalt nanocomposites, where ultrafine FeF 3 nanoparticles are homogeneously covered by a high conductive carbon framework. By the electrochemical kinetics calculation and multiphysics simulations, this FeF 3 @C-Asphalt nanocomposites consist of ultrafine nanoparticles and a constrained carbon framework, offering a high tap density (1.8 g cm −3 ), significantly improved conductivity, and enhanced charge pathways, and thereby enabling the fast electron transport, rapid ion migration, depressed electrode internal stress, and mitigated volume expansion. As a result, the optimized FeF 3 @C-Asphalt cathode delivers a high capacity of 517 mAh g −1 , high cyclic stability of 87.5% after 1000 cycles under 5 A g −1 (10 C), and excellent capacity retention of 77% from 0.5 A g −1 to 10 A g −1 (20 C, 250 mAh g −1 ). The work provides an easy-to-operate and low-cost approach to accomplish high cyclic stability metal fluoride-lithium batteries, which will guide the development of fast-charging ultrahigh-capacity cathode materials for the new energy industry.