Core-Double-Shell TiO 2 @Fe 3 O 4 @C Microspheres with Enhanced Cycling Performance as Anode Materials for Lithium-Ion Batteries.

Due to the volume expansion effect during charge and discharge processes, the application of transition metal oxide anode materials in lithium-ion batteries is limited. Composite materials and carbon coating are often considered feasible improvement methods. In this study, three types of TiO 2 @Fe 3 O 4 @C microspheres with a core-double-shell structure, namely TFCS (TiO 2 @Fe 3 O 4 @C with 0.0119 g PVP), TFCM (TiO 2 @Fe 3 O 4 @C with 0.0238 g PVP), and TFCL (TiO 2 @Fe 3 O 4 @C with 0.0476 g PVP), were prepared using PVP (polyvinylpyrrolidone) as the carbon source through homogeneous precipitation and high-temperature carbonization methods. After 500 cycles at a current density of 2 C, the specific capacities of these three microspheres are all higher than that of TiO 2 @Fe 2 O 3 with significantly improved cycling stability. Among them, TFCM exhibits the highest specific capacity of 328.3 mAh·g -1 , which was attributed to the amorphous carbon layer effectively mitigating the capacity decay caused by the volume expansion of iron oxide during charge and discharge processes. Additionally, the carbon coating layer enhances the electrical conductivity of the TiO 2 @Fe 3 O 4 @C materials, thereby improving their rate performance. Within the range of 100 to 1600 mA·g -1 , the capacity retention rates for TiO 2 @Fe 2 O 3 , TFCS, TFCM, and TFCL are 27.2%, 35.2%, 35.9%, and 36.9%, respectively. This study provides insights into the development of new lithium-ion battery anode materials based on Ti and Fe oxides with the abundance and environmental friendliness of iron, titanium, and carbon resources in TiO 2 @Fe 3 O 4 @C microsphere anode materials, making this strategy potentially applicable.