Solvothermal Route Based in Situ Carbonization to Metal-Oxide/Carbon Composite As Anode Material for Lithium Ion Battery

Magnetite (Fe₃O₄) is a very promising candidate as anode material in rechargeable lithium ion battery (LIBs) because of its ability to store up to eight Li per formula unit via reversible reactions, resulting in a high theoretical capacity of 924 mAh g^-1. Moreover, advantages such as low cost, ease of synthesis and environmental friendliness make it a promising candidate for large scale commercial applications for LIBs. However, Fe₃O₄ suffers from poor conductivity, large volume change and voltage hysteresis during the electrochemical reaction, which strongly limits its practical application. For the fact that carbon in its own feature exhibits several interesting properties, including electronic conductivity, high surface area, tunable porous structure, etc., the combination of Fe₃O₄ nanostructures and different forms of carbon materials show promising potential in the preparation of composite anode materials.

In this work, a high pressure and temperature based solvothermal route was developed for the synthesis of Fe₃O₄ with carbon as a composite anode for lithium-ion batteries (LIBs). The carbon in products was a result of the in situ carbonization of organic components under high pressure (24.0 MPa) and temperature (350 °C). Composites with different amounts of carbon were prepared by annealing the solvothermal products at different temperature. Taking advantage of the high theoretical capacity of Fe₃O₄ and favorable characteristics of carbon, a capacity of about 610 mAh g^-1 after 100 cycles was achieved for the composite with 54.6% carbon. The carbon amount depended electrochemical performance was also investigated. The Fe₃O₄@C composite can be used as an alternative anode material and the introduced synthetic strategy may provide further insights into the preparation of inorganic oxides coupled with carbon via in situ carbonization of organic components.