Confined space self-propagating room temperature synthesis of carbon-encapsulated Fe₃O₄ nanocrystals and its lithium storage performance

Abstract

A self-propagating reaction between ferrocene and iron nitrate nonahydrate that is initiated at room temperature is discovered. Amorphous carbon-encapsulated Fe₃O₄ nanocrystals (Fe₃O₄@C) can be one-step prepared in an autoclave through this reaction. The equiaxed Fe₃O₄ nanocrystals have typical dimensions in the range of 5-60 nm with a median size of 24.1 nm, and their weight percent is up to 82.3%. The course of the reaction is recorded, and the formation mechanism of Fe₃O₄@C with the core-shell structure is proposed. The scaling-up synthesis is also achieved, and 52.1 g of the Fe₃O₄@C can be obtained in a single batch. The shock wave appeared in the fast gas release self-propagating reaction in confined space plays a decisive role in the preparation of homogeneous Fe₃O₄@C with a core-shell structure. The Fe₃O₄@C anode shows excellent capacity retention with a high specific capacity of 494 mAh g^-1 at 1 A g^-1 in the 200th cycle.