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

Abstract

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 ribbonlike nickel cobaltite (NiCo 2 O 4 ) microstructure with unique layerby-layer-assembled nanocrystallites. This material demonstrates significant kinetic reversibility, good rate efficiency and bulk diffusibility of the electroactive ions, and a predominant semiinfinite 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 NiCo 2 O 4 -based all-solid-state supercapattery (NiCo 2 O 4 ||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 NiCo 2 O 4 , supplemented with enhanced electronic and ionic conductivities of N-doped rGO (negative electrode) and PVA/KOH gel (electrolyte separator), respectively.

Electrostructural Compatibility of Battery-Type Diffuse-Porous Co9S8–NiCo2S4/Defective Reduced Graphene Oxide and Flaky FeS/Nitrogen-Doped Defective Reduced Graphene Oxide for Ultra-High-Performance All-Solid-State Hybrid Pseudocapacitors

“…Since i = av b ( a and b are the parametric constants), the slope of the log i vs log v plot (linear fitted) offers the value approximation of b . For instance, the charge storage process is considered as battery type if b ≤ 0.5, and it is considered as capacitive if 0.5 < b ≤ 1. , From the log i vs log v plot in Figure S5, b ≈ 0.42, which evidently suggests that the electrochemical charge storage in Co 9 S 8 –NiCo 2 S 4 /D-rGO majorly involves the semi-infinite diffusion process …”

“…Further, the C s versus applied current density plot is presented in inset I of Figure C, which shows ∼68% rate capacitance of Co 9 S 8 –NiCo 2 S 4 /D-rGO over applied current densities of 1–24 A g –1 ; that is, Co 9 S 8 –NiCo 2 S 4 /D-rGO retains ∼68% of C s when subjected to the extreme condition of 24 times faster redox reactions. As the electrochemical characteristics of Co 9 S 8 –NiCo 2 S 4 /D-rGO, as observed in the CV and GCD profiles, partially mimic the electrochemical characteristics of battery-type electrode materials, the specific capacity values ( C in C g –1 ) of Co 9 S 8 –NiCo 2 S 4 /D-rGO were estimated with the use of the GCD parameters [Δ t (s) = time taken for complete discharging; m (g) = mass of Co 9 S 8 –NiCo 2 S 4 /D-rGO in the working electrode] in eq , at all applied current densities ( i in A) C = i Δ t m …”

“…The slope ( k 1 ) of the linear fitted i v 1 / 2 vs k 1 v 1/2 plot corresponds to the surface contribution, and the intercept ( k 2 ) corresponds to the diffusion contribution to the overall charge storage of Co 9 S 8 –NiCo 2 S 4 /D-rGO. By substituting the values of k 1 and k 2 in eq for each scan rate, the corresponding anodic peak current ( i ) has been derived for the surface and diffusion contributions, and accordingly the resultant scan rate controlled surface and diffusion capacitance values are calculated for Co 9 S 8 –NiCo 2 S 4 /D-rGO . Consequently, the diffusion contributions to the overall charge storage of Co 9 S 8 –NiCo 2 S 4 /D-rGO are found to be 87, 80, 75, 70, and 66% at the respective scan rates of 10, 20, 30, 40, and 50 mV s –1 , and the resultant scan rate versus C s contribution plot is shown in Figure D.…”

Carboxylated graphene oxide nanosheets as efficient electrodes for high-performance supercapacitors

“…Inset Figure 5F depicts the first ten (1st to 10th) GCD cycles of Frontiers in Chemistry frontiersin.org ECG-46, which demonstrates regular charge/discharge in the GCD curves. The preparation method of the ECGs can generate a high number of channels for effective electrolyte diffusion and enhance the material's conductivity and specific capacitance (Srivastav, Paliwal, and Meher, 2022), which is responsible for the exceptional electrochemical properties and performance.…”

Electrochemical Preparation of Hydroxylated Boron Nitride Nanosheets for Solid–State Flexible Supercapacitors Using Deep Eutectic Solvent and Water Mixture as Electrolytes

“…PVA–based gel polymer electrolytes (GPEs) have received extensive attention in solid–state flexible supercapacitors owing to its non–toxicity, low cost, and high film–forming ability . Usually, PVA–based GPEs gain ionic conductivity by adding strong acids, strong alkaline or salts, − which enables the assembled supercapacitors with narrow electrochemical operating window .…”