Mesoporous Thorn‐Covered Core–Shell Cathode and 3D Reduced Graphene Oxide Aerogel Composite Anode with Conductive Multivalence Metal Sulfides for High‐Performance Aqueous Hybrid Capacitors

Abstract

friendly, and safe electrochemical energy storage is growing. Conventional LIBs possess relatively high-energy density but suffer from slow charging rates owing to their low power density and short cycle stability. There are also safety hazards associated with the use of these environmentally toxic and flammable material. Moreover, these LIBs require expensive organic electrolytes to maintain the high voltages required for high-energy density. [3,4] Hence, low-cost aqueous ECs, which can operate in environmentally friendly and safe aqueous electrolytes, have been developed as candidates to overcome the aforementioned challenges of organic electrolyte-based electrochemical energy storage. Nevertheless, their low capacity and working voltage limit high-energy density for advanced use. [5,6] Aqueous hybrid capacitors (AHCs) present a promising alternative as electrochemical energy storage systems and can be designed as asymmetric full-cells using the different potential windows of anode and cathode reactions for high-energy density. [7-9] Earth-abundant metal oxides are promising materials for atom-by-ion reactions, but their low conductivity limits full capacitance, resulting in a slow charging rate and poor cycle stability. [10-12] This suggests that conductive metal sulfides are suitable electrode materials for a fast charging rate and long-life cycle stability. [6,13-15] Moreover, the synthesis of cathode materials at nanometer-scale sizes is required to enlarge active surface areas for high capacity and to shorten diffusion lengths for fast ion transfer; however, the random dense packing and agglomeration in electrodes lead to low tap density and capacity fading during repeated charge-discharge cycles. [16,17] Therefore, the development of a new cathode material to promote high tap density and long-life stability remains an enormous challenge. Moreover, very few materials capable of high-energy density have been synthesized as anode materials compatible with cathode materials. [18-20] Reduced graphene oxide aerogel (rGOA), which is a three-dimensional (3D) self-assembled material with rGO sheets, is a novel anode material that possesses ultra-light density, hierarchical pores for fast ion transport, and carbon networks for facile electron conduction. [18,19] However, rGOA anode gives a low capacity due to its limited active Aqueous hybrid capacitors (AHCs) are very promising electrochemical energy devices due to their being safe, cheap, and environmentally friendly, but their low energy and power densities are yet to be overcome for prolonged operation in a single fast charging device. Herein, a strategy to realize high-energy density and ultrafast rechargeable AHCs is reported. A thorn-covered core-shell conductive multivalence metal sulfide is synthesized as a cathode material that achieves high capacity via multivalence Ni and Co states and contains multiple mesoporous channels for fast ion transfer and ultrafine nanoparticles for efficient contact with electrolyte ions. Moreover, the multivalence metal stat...

CoFe Prussian blue analogues on 3D porous N-doped carbon nanosheets boost the intercalation kinetics for a high-performance quasi-solid-state hybrid capacitor

“…In this respect, the fine-tuning of electro-active battery-type materials can achieve a high energy performance of SCs. 10–12 An aqueous electrolyte is also attractive as its non-flammable nature can offer stable cell conditions for various applications such as wearable and flexible devices.…”

Zeolitic-imidazolate framework derived Ni–Co layered double hydroxide hollow microspheres with enhanced pseudocapacitive properties for hybrid supercapacitors

“…5a, the Ni–Co-LDH-M electrode has three pairs of obvious redox peaks, which is due to the combined potential of three individual components, demonstrating that they contribute independently to the redox reactions. Three pairs of peaks can be attributed to the reversible faradaic redox processes of Co 2+ /Co 3+ (Peak M1), 9 Ni 2+ /Ni 3+ (Peak M2) 36 and Co 3+ /Co 4+ (Peak M3), 37 which correspond to the reactions in eqn (3)–(5), respectively.Co(OH) 2 + OH − ↔ CoOOH + H 2 O + e − CoOOH + OH − ↔ CoO 2 +H 2 O + e − Ni(OH) 2 + OH − ↔ NiOOH + H 2 O + e − …”

A multi-interface CoNi-SP/C heterostructure for quasi-solid-state hybrid supercapacitors with a graphene oxide-containing hydrogel electrolyte

“…1,2 In the HSC, compared with the negative electrode material that obeys the electric double layer charge storage, the positive electrode material based on the faradaic redox reaction will be one of the keys to improve the specific capacity and energy density of the whole device. 3 Therefore, there is an urgent need for ideal positive electrode materials to truly achieve the above purpose.…”