For the first time, we successfully synthesize a self-supported Na0.7CoO2 nanosheet arrays via the facile “sodiation and post-calcination” method. Different from the traditional high temperature solid-state technique, this facile strategy can easily maintain the novel construction of the precursor. A mass loading as high as 8 mg cm−2 is achieved for the Na0.7CoO2 electrode with an initial capacity of 145.2 mAh g−1 at 1 C. Most importantly, the corresponding areal capacity for the Na0.7CoO2 electrode is calculated to be 1.16 mAh cm−2. This superb areal capacity is higher than that of the previously reported cathode materials. This special “sodiation and post-calcination” protocol mentioned in this article guarantees the high mass loading of Na0.7CoO2 on Ni foam, providing a straightforward direction for engineering high-areal-capacity cathode materials.