Laser etching of PI films to synthesize carbon-wrapped transition metal sulfides for long life sodium ion batteries

Transition metal sulfide is a kind of anode material with high application value for sodium ion batteries, and its theoretical specific capacity is much higher than that of commonly used materials such as hard carbon. However, due to the large volume change during the insert/extraction process of sodium ions, these materials generally suffer from poor cycle stability and poor rate performance. Wrapping a protective framework material in the outer layer of sulfide is an effective way to improve performance. Herein, we prepared a PI film doped with transition metal sulfides in this work, and obtained a carbon skeleton support structure by a facile method of laser etching, and finally synthesized a stable carbon-supported transition metal sulfide (L-S-PI@FeS2). This hybrid not only has high transition metal sulfide content with abundant sodium ion binding sites, but also has a large-volume three-dimensional carbon skeleton support network, which has high structural strength and limited volume change under large-scale charging and discharging condition. Benefiting from the efficient conversion of iron sulfide to sodium sulfide by this compound, it has a high specific capacity (460 mAh g-1 at 0.2 A g-1) and good cycle life (500 cycles) in the half-cell, and with excellent rate performance, it retains 92 % capacity after charging and discharging at high current (25 times). After the full battery is assembled, the specific capacity is 123 mAh g-1. Our work proposes a low-cost scheme to construct a carbon framework support system, thereby facilitating the development of anodes for sodium-ion batteries.