Rational design of porous Sn nanospheres/N-doped carbon nanofibers as an ultra-stable potassium-ion battery anode material

Potassium-ion batteries (PIBs) are considered as a promising candidate for large-scale energy storage applications due to the abundant potassium resources. In this work, a hybrid of porous Sn nanospheres incorporated in N-doped carbon nanofiber frameworks (Sn/N-CNFs) was fabricated via electrospinning and a subsequent carbonization process. As a PIB anode, Sn/N-CNFs exhibit superior cycling stability (198.0 mA h g −1 at 1 A g −1 after 3000 cycles, and the corresponding capacity retention rate is as high as 88.4%), outperforming other Sn-based materials. Such an excellent performance is ascribed to the synergistic effects of porous Sn nanospheres composed of ultra-small nanoparticles as well as to the unique and interconnected network of N-CNFs, which provide sufficient space for the volume expansion/contraction of Sn, supply efficient electrolyte diffusion paths, offer short K + diffusion distance, suppress the agglomeration of Sn nanoparticles, enhance the electronic conductivity, and thus facilitate the electron/ion transport. A hybrid of porous Sn nanospheres encapsulated in N-doped carbon nanofiber frameworks (Sn/N-CNFs) was constructed, and the as-fabricated Sn/N-CNFs exhibited a super-long cycle life, outperforming other Sn-based materials.