Concave Engineering of Hollow Carbon Spheres toward Advanced Anode Material for Sodium/Potassium‐Ion Batteries

Abstract Concave carbon spheres have attracted enormous interest due to their unique physicochemical properties. However, the precise synthetic methodology is still scarce, because it is a great challenge to control the dynamic and nonselective deformation process of the intermediate precursor. Herein, a series of hollow carbon spheres with tunable concavity are prepared by a facile and efficient polymerization‐buckling strategy. Both the concave degree and concave density of these hollow carbon spheres can be precisely regulated. Finite element analysis indicates the unique concave morphology can relieve the stress accumulation during the cycling process, endowing concave hollow carbon spheres with superior potassium and sodium storage performance. As the anode for potassium‐ion batteries, stable capacity of 104.9 mAh g −1 can be achieved at 4 A g −1 after 1350 cycles. For sodium‐ion batteries, reversible capacity of 116.4 mAh g −1 after 2700 cycles can be enabled at 2 A g −1 . This work may open a new avenue for the design of concave hollow carbon materials and promote their practical application in energy storage field.