Flexible FeS@Fe2O3/CNT composite films as self-supporting anodes for high-performance lithium-ion batteries.

The transition metal sulfides/oxides have been considered as promising anode materials for lithium ion batteries (LIBs) due to their high theoretical capacities but have suffered limits from the unsatisfactory electronic conductivity and limited lifespan. Here, FeS micro-flowers are synthesized by hydrothermal treatment and are wared and grafted into layer-by-layer carbon nanotubes (CNT). Subsequently, FeS@Fe2O3/CNT composite films are obtained by annealing, during which the FeS micro-flowers are partially oxidized to core-shell FeS@Fe2O3 micro-flowers. The FeS@Fe2O3/CNT composite electrodes exhibited high reversible capacity of 1722.4 mAh/g (at a current density of 0.2 A/g after 100 cycles) and excellent cycling stability (545.1 mAh/g at a current density of 2 A/g after 600 cycles) as self-supporting anodes. The prominent electrochemical performances are attributed to the unique reciprocal overlap architecture. This structure serves as a cushion to buffer large volume expansion during discharge/charge cycles, and ameliorates electrical conductivity. Due to their good specific capacity and cycle stability, these FeS@Fe2O3/CNT films have high potential application value to be used as high-performance anodes for lithium-ion, lithium sulfur and flexible packaging batteries.