Solid‐State Hybrid Supercapacitor Assembled from a Heterostructured Co−Ni Battery‐like Cathode and Supercapacitor‐Type Highly Disordered Carbon Nanosheets

Abstract

Hybrid at either the mechanism or the device level can lead to a hybridization effect of the kinetics and electrochemical characteristic of a supercapacitor (SC). Herein, a heterostructured NiCo 2 S 4 /Co x Ni 1-x (OH) 2 battery-like cathode material was designed, with which the obtained sample accomplished the combination of excellent electronic and ionic conductivity so as to realize an enhanced faradaic redox storage process. Besides, a SC-type highly capacitive anode material of a N and S codoped porous carbon nanosheets (ACNS) was also fabricated, which exhibits great advantages in terms of its enlarged specific surface area, the ease of introducing pseudocapacitive reactions, and its physical structure. These features directly lead to significant improvements in the electric double-layer capacitor (EDLC)-type electrochemical properties of the carbon anode. The combination of an EDLC-type carbon anode with the redox-reaction-type cathode in a full cell device could potentially lead to a charge storage process that simultaneously integrates the electrophysical and electrochemical processes. For these reasons, the obtained solid-state hybrid SC delivers a wide voltage window of 1.6 V, a high specific capacity of 121.3 C g À 1 , and enhanced energy/power densities of 26.1 Wh kg À 1 /11 kW kg À 1 . The as-assembled device can maintain a high and stable capacity retention of 89.1 % for over 10 000 cycles. The developed hybrid assembly strategy and the electrode combination may provide design guidelines for designing other high-energy hybrid SCs.

Oriented Nanosheet-Assembled CoNi-LDH Cages with Efficient Ion Diffusion for Quasi-Solid-State Hybrid Supercapacitors

“…Figure h presents GCD profiles of the AC//CoNi-LDH 2 HSC, from which one can obtain gravimetric capacities of 281.2–171.5 C g –1 at 1–10 A g –1 (61% retention) (Figure i). On the basis of the EIS curves and fitted equivalent circuit (inset) depicted in Figure j, the HSC possesses low resistance properties (0.6 Ω for R s and 4.2 Ω for R ct ) and good capacitive nature . The cycling stability of the AC//CoNi-LDH 2 is shown in Figure k.…”

“…In addition, compared with some recently reported related materials, CoNi-LDH 2 is competitive in gravimetric capacity and capacity retention (Table S1), which further confirms that our CoNi-LDH 2 is an excellent redox-type material. In Figure d, CV curves of the CoNi-LDH 2 electrode taken at 1–10 mV s –1 display apparent peaks between 0 and 0.6 V, which are attributed to the redox reactions involving Ni­(OH) 2 /NiOOH, Co­(OH) 2 /CoOOH, and CoOOH/CoO 2 transform reactions. − The kinetics of CoNi-LDH 2 is revealed by the peak current ( i ) and sweep rate ( v ) relationship by eqs and − where a and b represent arbitrary parameters. The 0.5 and 1.0 for b correspond to the capacitive-governed and diffusion-controlled processes, respectively. ,− The b values derived from the linear plots (Figure e) are 0.608 for peak I and 0.588 for peak II, bearing out the complex charge-storage mechanism combining the capacitive and diffusion behavior .…”

“…In Figure d, CV curves of the CoNi-LDH 2 electrode taken at 1–10 mV s –1 display apparent peaks between 0 and 0.6 V, which are attributed to the redox reactions involving Ni­(OH) 2 /NiOOH, Co­(OH) 2 /CoOOH, and CoOOH/CoO 2 transform reactions. − The kinetics of CoNi-LDH 2 is revealed by the peak current ( i ) and sweep rate ( v ) relationship by eqs and − where a and b represent arbitrary parameters. The 0.5 and 1.0 for b correspond to the capacitive-governed and diffusion-controlled processes, respectively. ,− The b values derived from the linear plots (Figure e) are 0.608 for peak I and 0.588 for peak II, bearing out the complex charge-storage mechanism combining the capacitive and diffusion behavior . The contributions for these two processes are quantified by eq , where k 1 v and k 2 v 1/2 denote the capacitive and diffusion contributions, respectively. , Figure f confirms that the capacitance contribution increases gradually from 52.3% at 1 mV s –1 to 78.7% at 10 mV s –1 , corresponding to the diffusion contribution from 47.7 to 21.3%.…”

“…On the basis of the EIS curves and fitted equivalent circuit (inset) depicted in Figure 4j, the HSC possesses low resistance properties (0.6 Ω for R s and 4.2 Ω for R ct ) and good capacitive nature. 34 The cycling stability of the AC//CoNi-LDH 2 is shown in Figure 4k. The gravimetric capacity is enhanced in the first 100 cycles stemmed from the electrochemical activation, 50 and about 60.7% of the initial capacity at 4 A g −1 is preserved over 5000 cycles.…”

Hybrid solid state supercapacitors (HSSC’s) for high energy & power density: an overview

“…Hence, HSC tackles all the difficulties, which have been faced in SC's and batteries by the advantages of a combination of the high energy density of batteries along with the high power density of SC. [51,52] As shown in Fig. 2, from the year 2000 onwards, a large number of researchers are attracted towards HSC.…”