Low-strain and ultra-long cycle stability large-diameter soft carbon microsphere potassium ion anode.

Potassium-ion batteries (PIBs) with high potassium abundance, low redox potential of K/K and similar energy storage mechanism to lithium-ion batteries are potential candidates for large-scale energy storage in the future. However, due to the large size of K (1.38 Å), PIBs exhibit poor kinetics in existing commercial graphite anode materials system. Additionally, they can degrade the material structure and induce significant volume effects, leading to material fragmentation and pulverization in the process of long cycling. It is not straightforward to achieve compatibility with existing potassium anode systems, which forces us to develop new high-performance, low-strain anode materials with outstanding structural stability. Hence, nitrogen doping low-strain and large diameter soft carbon microspheres (NDCS) anodes were successfully developed to meet the demands of high-performance PIBs. Due to its large diameter and low strain characteristics, the Coulomb efficiency is as high as 98.7 %, and the capacity retention is close to 70 % after 4000 cycles at a current density of 1 A/g. Furthermore, we employed advanced computed tomography (CT) techniques to enhance the comprehension of electrochemically driven reactions from the surface to the bulk. This work provides a promising and viable technical solution for exploring PIBs anode materials with low strain and long cycling capabilities to meet the requirements of various application scenarios.