Mechanistic insights into nitrate-pillared Co(OH)2/rGO hybrids: Toward supercapattery with superior rate performance and long-term stability

This study investigates pristine cobalt hydroxide (Co(OH) 2 ), nitrate-intercalated Co(OH) 2 (NO 3 − -CH), and its reduced graphene oxide (rGO) composite as advanced hybrid electrodes for high-performance supercapattery device. Co(OH) 2 has limited rate capability, with only 56% capacitance retention after 500 cycles, due to typically exhibited diffusion-limited kinetics and structural degradation. Nitrate intercalation expands the interlayer spacing, enhances ion transport, and improves structural stability, leading to superior electrochemical performance. The NO 3 − -CH/rGO composite delivers a high specific capacitance of 428 F g −1 at 1 A g −1 , retains 330 F g −1 at 15 A g −1 , and exhibits a low charge-transfer resistance of 2.5 Ω, compared with 16.8 Ω for pristine Co(OH) 2 . The synergistic effect of nitrate-induced structural modification and the conductive rGO network promotes rapid electron/ion transport and enables 76% capacitance retention after 3000 charge–discharge cycles. An asymmetric supercapattery device (NO 3 − -CH/rGO//AC) delivers a maximum energy density of 22.5 Wh kg −1 and a power density of 399 W kg −1 , while maintaining 13.3 Wh kg −1 at 2394 W kg −1 . The device further retains 90.5% of its initial capacitance after 5000 cycles, highlighting the effectiveness of anion engineering and carbon hybridization for durable, high-performance energy storage device.