Opening ZnSe/C Nanocages: Multi-Hierarchy Stress-Buffer for Boosting Cycling Stability in Potassium-Ion Batteries
Potassium ion batteries (KIBs) are considered as the emerging and promising grid-scale energy storage devices owing to the earth-abundant potassium resource. A pivotal limitation of KIBs is the sluggish diffusion kinetics and structural degradation resulting from huge mechanical stress during repeated intercalation/deintercalation of K+ ions. Herein, we design the opening ZnSe/C nanocages composed of sub-10 nm nanoparticles with multi-hierarchy stress-buffered effect for KIBs. The primary ultrafine nanoparticles, the secondary opening structure and the tertiary hollow structure as stepwise stress-release hierarchies can effectively reduce diffusion-induced stresses and greatly enhance the structural integrity, which is further validated by detailed finite element simulation analysis. Meanwhile, the carbon layer can enhance the electronic conductivity and suppress the agglomeration of ZnSe nanoparticles, achieving high-rate performance. Owing to these merits, the opening ZnSe/C nanocages deliver a high reversible capacity of 318 mAh g-1 at 50 mA g-1 as well as excellent cyclability of 189 mAh g-1 up to 1000 cycles at 500 mA g-1. This work provides new insight into the excellent structural design with multi-hierarchy stress-buffered effect for advanced potassium storage.