Millerite Core–Nitrogen‐Doped Carbon Hollow Shell Structure for Electrochemical Energy Storage

Abstract

Nickel sulfides have drawn much attention with the benefits of a high redox activity, high electrical conductivity, low cost, and fabrication ease; however, these metal sulfides are susceptible to mechanical degradation regarding their cycling performance. Conversely, hollow carbon shells exhibit a substantial electrochemical steadiness in energy storage applications. Here, the design and development of a novel millerite core-nitrogen-doped carbon hollow shell (NiS-NC HS) structure for electrochemical energy storage is presented. The nitrogen-doped carbon hollow shell (NC HS) protects against the degradation and the millerite-core aggregation, giving rise to an excellent rate capability and stability during the electrochemical charging-discharging processes, in addition to improving the NiS-NC HS conductivity. The NiS-NC HS/18h supercapacitor electrode displays an outstanding specific capacitance of 1170.72 F g (at 0.5 A g ) and maintains 90.71% (at 6 A g ) of its initial capacitance after 4000 charge-discharge cycles, owing to the unique core-shell structure. An asymmetric-supercapacitor device using NiS-NC HS and activated-carbon electrodes exhibits a high power and energy density with a remarkable cycling stability, maintaining 89.2% of its initial capacitance after 5000 cycles.

Graphene Nanosphere as Advanced Electrode Material to Promote High Performance Symmetrical Supercapacitor

“…Moreover, the pseudocapacitive components suffer inferior cycle stability in the electrochemistry environment. [31] Therefore, it is of great significance to make full use of the advantages of fast charge-discharge property, excellent conductivity, and excellent electrochemical stability of carbon materials, and further improve the structures to get high energy density, high power density, and long cycle life, at the same time, for supercapacitor electrodes. Graphene has the characteristics of high conductivity, large surface area, and high electrochemical stability.…”

Dual Hybrid Effect Endowing Nickel–Cobalt Sulfides with Enhanced Cycling Stability for Asymmetrical Supercapacitors

“…Supercapacitors are a kind of promising high-efficiency electrical energy storage (EES) devices for large-scale application, on account of their attractive power density and ultralong life span compared with other traditional EES devices such as rechargeable organic/aqueous batteries and fuel cells. − The novel and potential electrodes, configurated by pseudo-capacitive or battery-like materials including transition metal-based oxides/hydroxides and sulfides, shedding light on superior electroactivity with rich redox reaction and high energy density than the carbonaceous materials, have attracted growing attention in recent years. − Unfortunately, so far, these redox electrode materials available are often restrained by the insufficient contact between the large-sized active materials and electrolyte, sluggish ion/electron transport kinetics caused by low conductivity, and the collapse of the structure during the electrochemical reaction, resulting in unsatisfied charge-storage capability and inferior electrochemical cycling stability. , In this regard, tremendous attempts have been devoted to elevating the overall electrochemical performance of these kinds of electrode materials via developing various structure architectures. For instance, the design and fabrication of unique heterojunction/interface hybrid structures are represented by core–shell and superlattice configurations via in situ coating and multiple calcination/etching process. − Such a hybrid configuration is believed to accelerate electron transfer and improve the ion mobility under the utilization of a built-in electric field that happened at the tangent interfaces, thus leading to enhanced electrochemical performance. − However, the requirements for the preparation process of the heterojunction/interface hybrid structures are normally harsh and complex, which impede their further practical applications. More recently, the addition of the external electric field is considered to be a facile and time-saving strategy to fabricate advanced redox materials with the desired composition and structure. , In this procedure, a phase transition or partially electrooxidation of active materials has been employed to activate their intrinsic electrochemical performance. , For example, Wan et al synthesized a Co@Co­(OH) 2 heterostructure nanosheet supported by cellulose via a joint strategy of magnetron sputtering and electrooxidation process.…”

Recent Developments of Transition Metal Compounds-Carbon Hybrid Electrodes for High Energy/Power Supercapacitors

“…Carbon shell with high mechanical strength not only could enhance the electrical conductivity of composite, but also protect against the degradation and aggregation of TMCs nanoparticles. In this case, Yoon et al [ 79 ] designed and developed a novel millerite core-nitrogen-doped carbon hollow shell (NiS–NC HS) structure by using PD-derived carbon as coated and NiS as the core. Compared with pristine Ni 3 S 2 (828.21 F g −1 ), the maximum specific capacitance of NiS–NC HS was 1170.72 F g −1 at 0.5 A g −1 , and 90.71% of its initial capacitance could be maintained at 6 A g −1 after 4000 charge–discharge cycles.…”