Boosting low-temperature sodium/potassium storage performance of Bi via novel electrochemical milling process

The development of low-temperature (Low-T) sodium/potassium-ion batteries (NIBs/KIBs) with both high power density and high energy density is essential for critical applications (i.e. defense, aerospace). However, it is greatly challenged to realize high-performance electrode material because of the extremely sluggish desolvation of the charge carrier (Na+/K+) at Low-T. Here, we exploit a mechanism implicitly occurring in sodium batteries during cycling to develop it into a top-down method in the synthesis of electrode materials with ultrasmall particle size and pronounced nanoporosity associated with unprecedented electrochemical properties at Low-T. Taking bismuth (Bi) as an example, we demonstrate this novel electrochemical milling process (EMP) to prepare ultrasmall-sized Bi nanoparticles embedded in a three-dimensional (3D) porous carbon framework ([email protected]) that shows excellent both sodium/potassium storage performance at −20 °C. The ultrasmall sized Bi nanoparticles (~10 nm) via EMP and 3D interconnected porous channels reduce the diffusion path of electron/ion, realizing the ultrafast kinetics process at Low-T. The [email protected] anodes demonstrate superior rate performances (190 mAh g−1 at 5 A g−1 for NIBs and 233 mAh g−1 at 20 A g−1 for KIBs) and long cycle life (205 mAh g−1 after 2,000 cycles at 10 A g−1 for KIBs) at −20 °C. Furthermore, when used as potassium-ion hybrid capacitors (PIHCs), the [email protected] exhibits a distinctly better performance than the previously reported PIHCs at Low-T. This work offers a new top-down method to fabricate high-performance electrode materials for both NIBs and KIBs at Low-T.