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 (N+/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 nano-particles embedded in a three-dimensional (3D) porous carbon framework (EMP-Bi@3DCF) that shows excellent both sodium/potassium storage performance at -20 degrees C. The ultrasmall sized Bi nanoparticles (similar to 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 EMP-Bi@3DCF 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 degrees C. Furthermore, when used as potassiumion hybrid capacitors (PIHCs), the EMP-Bi@3DCF 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. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The novel electrochemical milling process (EMP) is used to prepare ultrasmall-sized Bi nanoparticles embedded in a three-dimensional porous carbon framework (EMP-Bi@3DCF), showing excellent sodium/potassium storage performance at -20 degrees C. The ultrafast kinetics process is achieved through the ultrasmall sized Bi nanoparticles via EMP and 3D interconnected porous channels, leading to superior rate performances and long cycle life for both NIBs and KIBs at Low-T.