Homogeneous nickel bicarbonate nanocrystals as electrode materials for high-performance asymmetric supercapacitors

In this work, we successfully synthesized nickel bicarbonate nanocrystals with different uniformity as electrode materials for asymmetric supercapacitors to study this relationship. Compared with heterogeneous nickel bicarbonate nanocrystals (HTNBs), homogeneous nickel bicarbonate nanocrystals (HMNBs) as electrode material possess a larger specific surface area, which could provide more electroactive sites for the electrochemical reactions, thus exhibiting excellent electrochemical performance. The HMNBs electrode materials possess excellent rate performance (1560 ​F ​g−1 at 2 ​A ​g−1 and 1350 ​F ​g−1 at 30 ​A ​g−1, respectively). Notably, the asymmetric supercapacitors constructed with HMNBs as anode material and activated carbon (AC) as cathode material have high energy density (41.2 ​Wh·kg−1 at 160 ​W ​kg−1 and 28.9 ​Wh·kg−1 at 4000 ​W ​kg−1, respectively), which was significantly higher than HTNBs//AC asymmetric supercapacitors (27.42 ​Wh·kg−1 at 160 ​W ​kg−1 and 16.67 ​Wh·kg−1 at 4000 ​W ​kg−1, respectively). The cycling stability for HMNBs//AC asymmetric supercapacitors is also better than the HTNBs//AC asymmetric supercapacitors.