In situ formed robust submicron-sized nanocrystalline aggregates enable highly-reversible potassium ion storage

We report an electrode architecture made of submicron-sized nanocrystalline aggregates obtained in situ from ball-milled BiSb crystals during the potassiation/depotassiation process for use as a potassium ion battery electrode with high electrochemical performance and great stability. Nanocrystalline aggregates are individual particles composed of nanocrystals clustered together. The interconnected nanoparticle network as a potassium ion battery (PIB) electrode shows various advantageous characteristics, including adaption to related structures variation, stable SEI layer formation between the interface of electrode and electrolyte, and high efficiency in conductivity and ion migration/diffusion. As the anode of a PIB, the BiSb nanocrystalline aggregate achieves a high capacity of 514.1 mA h g(-1) after 100 cycles at 0.25 A g(-1), a high-rate capability of up to 10 A g(-1), and an ultra-stable life cycle for 6000 cycles. A series of analyses including consecutive in situ X-ray diffraction measurements, in situ electrochemical impedance spectroscopy, and ex situ electron microscopy, are conducted to demonstrate the relevant reaction mechanism of the nanocrystalline aggregates during the evolution of composition as well as their structure during the cycling process.

Automated summary

This study presents an electrode architecture made of submicron-sized nanocrystalline aggregates obtained from ball-milled BiSb crystals during the potassiation/depotassiation process for high performance and stability in potassium ion batteries. Through various analyses, it demonstrates the reaction mechanism of the nanocrystalline aggregates during composition evolution and cycling process.