Ribbon-like Nickel Cobaltite with Layer-by-Layer-Assembled Ordered Nanocrystallites for Next-Generation All-Solid-State Hybrid Supercapatteries

In the context to develop ultra-efficient electrode materials with good physicoelectrochemical and electrostructural properties, for their application in high-performance supercapatteries, herein, a facile tartrate-mediated inhibited crystal growth method is reported to engineer thoroughly uniform ribbon-like nickel cobaltite (NiCo₂O₄) microstructure with unique layer-by-layer-assembled nanocrystallites. This material demonstrates significant kinetic reversibility, good rate efficiency and bulk diffusibility of the electroactive ions, and a predominant semi-infinite diffusion mechanism during the redox-based charge storage process. This material also shows bias-potential-independent equivalent series resistance, very low charge-transfer resistance, and diagonal Warburg profile, corresponding to the ion diffusion occurring during the electrochemical processes in supercapacitors and batteries. Further, the fabricated NiCo₂O₄-based all-solid-state supercapattery (NiCo₂O₄||N-rGO) delivers excellent rate-specific capacity, very low internal resistance, good electrochemical and electrostructural stability (∼94% capacity retention after 10,000 charge–discharge cycles), energy density (31 W h kg^–1) of a typical rechargeable battery, and power density (13,003 W kg^–1) of an ultra-supercapacitor. The ultimate performance of the supercapattery is ascribed to low-dimensional crystallites, ordered inter-crystallite and channel-type bulk and boundary porosity, multiple reactive equivalents, enhanced electronic conductivity, and “ion buffering pool” like behavior of ribbon-like NiCo₂O₄, supplemented with enhanced electronic and ionic conductivities of N-doped rGO (negative electrode) and PVA/KOH gel (electrolyte separator), respectively.