High Areal Capacity Na_0.67CoO₂ Bundle Array Cathode Tailored for High‐Performance Sodium‐Ion Batteries

Abstract

Abstract Sodium‐ion batteries are enjoying increasing attention as the most optimal alternative to lithium‐ion batteries, due to their advantage of cost‐effectiveness. As a typical cathode material for SIBs, layered Na x CoO 2 was introduced, demonstrating a satisfactory ion diffusion efficiency. Nevertheless, the mass loading of cathode materials in most of the literature is between 0.5 and 2.0 mg cm −2 . In this regard, we introduce a facile “sodiation and calcination” method, to directly build self‐supported Na 0.67 CoO 2 bundle arrays on three‐dimensional conductive Ni foam. By this fabrication pathway, the mass loading of Na x CoO 2 on Ni substrate can reach values as high as ∼10 mg cm −2 . A high areal capacity of 1.66 mAh cm −2 can be achieved based on a current rate of 0.33 C with a voltage window of 2.0–3.8 V (vs Na/Na + ). Intriguingly, this high mass loading Na 0.67 CoO2 cathode also performs with a satisfactory cyclic stability over 100 cycles at a current rate of 1.4 C, with a discharge capacity of 123.6 mAh g −1 remaining without obvious capacity fading.