High energy-power Zn-ion hybrid supercapacitors enabled by layered B/N co-doped carbon cathode

A novel TiSe2 (de)intercalation type anode for aqueous zinc-based energy storage

The crucial request for alternative clean energy technologies to replace conventional fossil fuels and drive technological advancement in consumer and wearable electronics, electric vehicles etc. has led to great advancement in electrochemical energy storage systems research. The lithium-ion battery possesses high energy density while the supercapacitor can guarantee high power density. However, modern technologies such as integrated solar and wind energy solutions require a blend of high energy and power density devices, which is a great challenge. Presently, there is increased research interest in aqueous hybrid supercapacitors, a device capable of combining the high energy density of rechargeable batteries and the high-power density of electric-double layer capacitors.The current hotspot of the hybrid supercapacitor research is the zinc-ion hybrid supercapacitor owing to its several advantages such as the abundance of Zinc resource over lithium, high theoretical capacity of Zn, double charge transfer compared to univalent Lithium, environmental safety and high energy/power density. Wang et al first reported the carbon zinc-ion hybrid supercapacitor in 2018 by directly using zinc foil as anode and bio-carbon as cathode to realize long stability up to 20000 cycles. Next, Dong et al also developed an activated carbon-based zinc-ion hybrid supercapacitor which achieved a high energy density of ~84 Wh kg-1 and power density of 14.9 kW kg-1 in a potential window of 0.2 – 1.8 V. Despite the rapid advances over a short period in this class of energy storage devices, some problems still exist. The coulombic efficiency of Zinc-ion hybrid supercapacitors is inferior in low-cost ZnSO4 electrolytes owing to side reactions between the electrolyte and the Zn anode, while the mass loading of commonly used carbon cathode is extremely low (less than 2 mg cm-2). Importantly, the charge storage mechanism in zinc-ion hybrid supercapacitors is unclear.In this work, we developed high performance zinc-ion hybrid supercapacitors with superior charge storage, improved rate capability, and high power and energy density using a high mass density carbon anode with superior capacitive/pseudocapacitive storage. We successfully reveal that the charge storage of zinc-ion hybrid supercapacitors is extensively limited in zinc sulfate electrolytes and successfully address the coulombic efficiency problem using by modifying the electrolyte. Finally, using techniques such as in-situ Raman spectroscopy and X-ray diffraction analysis, we probe the charge storage mechanism and unravel a double cation charge storage mechanism, resulting in high energy density and extended potential window. Finally, our work provides crucial insights into understanding the charge storage process of zinc-ion hybrid supercapacitors and designing hybrid supercapacitors with new material chemistries.

In the last few years, zinc ion hybrid supercapacitors (ZHSs), comprising a capacitive-type cathode coupled with zinc foil as the anode, have attracted considerable attention for modern electrochemical applications due to their high theoretical capacity, reliability, and environmental friendliness. However, these ZHSs face substantial challenges owing to dendrite formation, hydrogen evolution, corrosion, and other passive reactions of Zn metal, posing significant obstacles to their practical feasibility. In this regard, Zn metal-free Type-II ZHSs offer a compelling alternative and are increasingly studied to resolve these intrinsic challenges. However, comprehensive review articles focused on their construction and the selection of related electrode materials, which are essential for the fabrication of Zn metal-free Type-II ZHSs, remain very scarce. Therefore, this article provides a comprehensive review of the historical developments in ZHSs, their fundamentals, and the limitations of Type-I ZHSs. Subsequently, an overview of recent progress in battery-type cathode (Mn-based, V-based, PBA, and others) and anode materials (Nb-based, Mo-based, TiS2, TiSe2, and others) investigated for Type-II Zn metal-free hybrid supercapacitors is provided. Finally, the advantages, key bottlenecks, and viewpoints are highlighted to facilitate the future progress of Type-II ZHSs. It is anticipated that this review article will provide strategic guidance, with a primary focus on the design and development of high-performance Zn metal-free ZHSs, complementing the existing Type-I ZHSs.

A comprehensive review on fundamentals and components of zinc-ion hybrid supercapacitors

Towards high energy density zinc-based nonaqueous hybrid supercapacitors via regulating oxygen substituents in carbon cathode

Zinc-ion hybrid supercapacitor (ZIHSC) is one of the popular emerging battery hybrid supercapacitors which integrates Zinc-ion battery electrode with capacitive electrode, thereby, taking advantages of high energy and power densities in addition to cycle stability. Their easy availability, optimum stability, high volumetric capacity and safety efficacy make ZIHSC a favoured choice over other battery hybrid supercapacitor. The research progress on ZIHSC is still in the bud stage and mainly faces challenges in developing a high energy density cathode and dendrite-free anode which hinder its practical applicability. To tackle these issues there must a proper understanding of the Zn2+ ion’s charge storage mechanism for the synthesised electrode materials which would be helpful in developing a technologically efficient ZIHSC. This review provides an overview of the fundamental working and performance metrics of ZIHSC. It then discusses about the different cathode and anode materials in length. This review work also highlights some of the newly developed electrode materials’ effectiveness in enhancing the ZIHSC’s performance. The challenges and the solutions associated with cathode and anode were also addressed in this review.

ABSTRACTOver the past decade, the extensive consumption of finite energy resources has caused severe environmental pollution. Meanwhile, the promotion of renewable energy sources is limited by their intermittent and regional nature. Thus, developing effective energy storage and conversion technologies and devices holds considerable importance. Zinc‐ion hybrid supercapacitors (ZISCs) merge the beneficial aspects of both supercapacitors and batteries, rendering them an exceptionally promising energy storage method. As an important cathode material for ZISCs, the tunnel structure MnO2 has poor conductivity and structural stability. Herein, the ZnxMnO2/PPy (ZMOP) electrode materials are prepared by hydrothermal method. Doping with Zn2+ is used to enhance its structural stability, while adding polypyrrole to improve its conductivity. Therefore, the fabricated ZMOP cathode presents superb specific capacity (0.1 A g−1, 156.4 mAh g−1) and remarkable cycle performance (82.6%, 5000 cycles, 0.2 A g−1). Furthermore, the assembled aqueous ZISCs with ZMOP cathode and PPy‐derived porous carbon nanotube anode obtain a superb capacity of 109 F g−1 at 0.1 A g−1. Meanwhile, at a power density of 867 W kg−1, the corresponding energy density can achieve 20 Wh kg−1. And over 5000 cycles at 0.2 A g−1, the cycle performance of ZISCs maintains at 86.4%, which exhibits excellent cycle stability. This suggests that ZMOP nanowires are potential cathode materials for superior‐performance aqueous ZISCs.

The hybrid supercapacitor is appealing for commercial applications which have the aptitude to supply high energy density without compromising other supercapacitor properties. The Review is the complete insight of a reported Na+- and Zn+-based hybrid supercapacitor with the principle of the working mechanism. The combination of different semiconductor-based electrodes as the anode or cathode has been presented so researchers can update the progress of the sodium-ion-based hybrid supercapacitor (Na-HSC). In pursuit of replacing the activated carbon (AC)-based electrode due to its limited capacitance which results from an imbalance between the cathode and anode, we provide this Review with tables, figures, and their comparative studies. Society is moving toward smart electronic and hybrid devices that require flexibility, resilience, and high safety as people closely interact with these devices. The zinc ion hybrid supercapacitor (Zn-HSCs) is a comprehensive solution to toxic and explosive sodium-ion and lithium-ion devices. This Review represents recent reported metal oxides, chalcogenides, ceramics, MXenes, and carbon-based materials used for Zn-HSCs. Additionally, the hybrid capacitors with flexibility and the lightweight micro-supercapacitors have been studied and presented along with their challenges for pragmatic usage.

Zinc ion hybrid supercapacitors (ZIHSCs) are truly promising as next-generation high-performance energy storage systems because they could offer high energy density like batteries while exhibiting high power output and long cycle life traits of supercapacitors. The key point of constructing a high-performance ZIHSC is to couple the Zn anode with an appropriate cathode material, which has high theoretical capacity, cost-effectiveness, and intrinsic safety features. In this work, we have demonstrated the potentiality of S, N co-doped porous carbon nanocubes (S, N-CNCs) as a cathode material for devising a ZIHSC with excellent energy density and cycle life. The S, N-CNCs are prepared from a zeolitic imidazolate framework (ZIF)-8 precursor via a simultaneous pyrolyzing-doping strategy in an inert atmosphere. Resultant CNCs are monodisperse with an average size of around 65 nm and porous in nature, with uniform N and S doping throughout the structure. Benefitted from such hierarchical porous architecture and the presence of abundant heteroatoms, the assembled ZIHSC with S, N-CNC as the cathode and Zn-foil as the anode in a ZnSO4 aqueous electrolyte could reach a specific capacity as high as 165.5 mA h g-1 (331 F g-1) at 1 A g-1, which corresponds to a satisfactory energy density of 148.9 W h kg-1 at the power density of 900 W kg-1. The ZIHSC has displayed a good cycle stability with more than 70% capacity retention after 10,000 charge-discharge cycles. Furthermore, to verify the practical feasibility of such a cathode material, an aqueous 3D Zn@Cu//S, N-CNC full-cell device is fabricated, which has demonstrated a satisfactory specific capacity (49.6 mAh g-1 at 0.25 A g-1) and an impressive energy density (42.2 Wh kg-1 with 212.2 W kg-1). Full ZIHSC devices are also found to be efficient in powering light-emitting diodes, further substantiating their feasibility in next-generation energy storage applications.

Zinc‐ion hybrid supercapacitors (ZIHSCs) represent a promising frontier in high‐performance energy storage, offering greater energy density characteristic shown by batteries alongside high power yield and extended life of supercapacitors. Carbon materials, due to their inexpensiveness, abundance, and excellent conductivity, have been promising cathode choices for ZIHSCs. However, the application of electrospun carbon nanofibers as cathodes in ZIHSCs remains relatively unexplored. This study describes the synthesis of electrospun porous N‐doped carbon (NC)‐carbon nanofibers (NC‐CNFs) through a carbonization‐activation pathway. The NC‐CNFs achieves specific surface area (SSA) of 2426.6 m2g−1 and a specific capacity of 173.5 mAhg−1 at 0.1 Ag−1 in a ZIHSC setup. A maximum energy density (ED) and power density (PD) of 138.8 Wh kg−1 and 7998.9 W kg−1, respectively is also obtained. After 10 000 charge‐discharge cycles, the device retains 91.7% initial capacitance. Additionally, the charge storage performances of a symmetric supercapacitor (SC) and a ZIHSC, made of NC‐CNFs, are compared to prove the superiority of the ZIHSC over SC. This study highlights that incorporating NC into electrospun carbon nanofibers, with potassium hydroxide (KOH) activation, yields a ZIHSC cathode material with an optimal porous 1D morphology, large SSA, optimized nanofiber diameter, and efficient heteroatom doping, leading to excellent electrochemical performance.

High energy-power density Zn-ion hybrid supercapacitors with N/P co-doped graphene cathode

Zinc-ion hybrid supercapacitors (ZHSCs) are attracting significant attention due to their high energies/power densities, safety, and low cost. In this review, recent advances in the development of ZHSCs are summarized. Particular emphasis is placed on state-of-the-art cathodes (including carbon, metal oxides, MXenes, and redox-active polymers), anodes (including Zn-based composites and Zn-free materials) and electrolytes for ZHSCs. Furthermore, the latest research on functional ZHSC devices with miniaturized ZHSCs, fiber-shaped ZHSCs, self-chargeable ZHSCs and self-healing devices is reported. Finally, further developments with ZHSCs are envisaged for future research in this thriving field.

Flexible reduced graphene oxide/V2O5 composite battery-type cathode and MXene capacitor-type anode for aqueous zinc ion hybrid supercapacitors with high energy density

Zincophilic zwitterionic hydrogel electrolyte towards dendrite-free zinc ion hybrid supercapacitors with anti-self-discharge ability

Rationally designed anode and gel polymer electrolyte for high-performance zinc-ion hybrid supercapacitors