A universal strategy to fabricate metal sulfides@carbon fibers as freestanding and flexible anodes for high performance lithium/sodium storage

The future trend toward flexible electronics creates a demand for flexible power sources using rechargeable batteries, where freestanding and flexible electrodes are of critical importance. The utilization of high capacity anode materials like metal sulfides in flexible batteries is highly desirable for the miniaturization of electronic devices but is nevertheless very challenging in the fabrication of an electrode that is freestanding and flexible. Herein, a universal electrospinning strategy to fabricate freestanding and flexible metal sulfides@carbon electrodes is proposed based on the formation of chelate complexes between l-cysteine and metal cations. Taking SnS as a model material, flexible fiber electrodes are realized with SnS nanoparticles well embedded in the continuous and interwoven carbon fibers. As freestanding electrodes for lithium and sodium storage, a high capacity, good rate capability, and excellent cycling stability are simultaneously achieved. Such a strategy is also successfully extended to the fabrication of Ni ₃S ₂/C fibers and Fe ₇S ₈/C fibers, suggesting the universality in fabricating freestanding and flexible high capacity electrodes.