Embedding amorphous SnS in electrospun porous carbon nanofibers for efficient potassium storage with ultralong cycle life

Potassium-ion batteries (PIBs) have gained substantial research interest for scalable and affordable stationary applications owing to their low cost, natural abundance, and high energy density. However, the large size of potassium (K) ion hampers its diffusion and causes significant strain in conventional electrode materials, resulting in low capacity, poor rate capability, and short lifespan. Herein, we develop a new strategy by confining amorphous tin sulfide (a-SnS) in electrospun porous carbon nanofibers (denoted as a-SnS@pCNFs) to realize the highly reversible potassiation/depotassiation of SnS. The amorphous nature of a-SnS enables a lower activation energy barrier towards structural rearrangement during any possible conversion reaction, which facilitates an increased electrochemical stability. Moreover, the pCNF skeleton not only improves the overall electrical conductivity of a-SnS@pCNFs, but also accommodates the volume variation of the SnS during the repeated cycles of charge/discharge. Combining these benefits of a-SnS and the tailored pore structures in pCNFs, the a-SnS@pCNFs composite delivers a high reversible capacity (∼300 mAh g−1 at 1 A g−1), a remarkable rate capability (∼85.4 mAh g−1 at 10 A g−1) and an ultralong lifespan (2000 cycles at 3 A g−1). This work provides a viable strategy to stabilize the conversion and alloying materials with fast and reversible K-ion storage towards practical applications.