Materials Design and System Construction for Conventional and New-Concept Supercapacitors

Superlithiated Polydopamine Derivative for High-Capacity and High-Rate Anode for Lithium-Ion Batteries

Organic electrode materials, with low-cost synthesis and environmental friendliness, have gained significant research interest in lithium-ion batteries (LIBs). Polydopamine (PDA), as a bioderived organic electrode material, exhibits a low capacity of ∼100 mAh g^-1, greatly limiting the practical application in LIBs. In this work, we find that a simple heat treatment at 300 °C can endow PDA-derived material (PDA300) with superior electrochemical performance. The obtained PDA300 electrode exhibits an ultrahigh capacity of 977 mAh g^-1 at 50 mA g^-1. Further combining the PDA300 with highly conductive Ti₃C₂T _x MXene, the obtained PDA300/Ti₃C₂T _x composite is demonstrated by high capacity (1190 mAh g^-1, 50 mA g^-1), excellent rate capability (remaining 552 mAh g^-1 at 5 A g^-1), and good cycling stability (82% retaining after 1000 cycles). The outstanding lithium storage performance is highly associated with the superlithiation process of the unsaturated carbon-carbon bonds in the PDA derivative and the introduction of the highly conductive Ti₃C₂T _x substrate with a unique two-dimensional nanostructure. This work will provide new opportunities for the expansion of high-performance organic anodes for LIBs.

A facile and processable integration strategy towards Schiff-base polymer-derived carbonaceous materials with high lithium storage performance

Herein, a novel in situ concentrated-solution-induced polymerization strategy is developed towards the integration of Schiff-base networks into graphene foam with processable and moldable characteristics. This bottom-up design process endows the resultant composites with a high nitrogen content (9.6 at%) and abundant porosity and accordingly demonstrates high lithium storage properties.

Synthesis and Electrochemical Performance of Molybdenum Disulfide-Reduced Graphene Oxide-Polyaniline Ternary Composites for Supercapacitors

Molybdenum disulfide/reduced graphene oxide/polyaniline ternary composites (MoS₂/rGO/PANI) were designed and synthesized by a facile two-step approach including hydrothermal and in situ polymerization process. The MoS₂/rGO/PANI composites presented an interconnected 3D network architecture, in which PANI uniformly coated the outer surface of the MoS₂/rGO binary composite. The MoS₂/rGO/PANI composites with a weight percent of 80% (MGP-80) exhibits the best specific capacitance (570 F g⁻¹ at 1 A g⁻¹) and cycling stabilities (78.6% retained capacitance after 500 cycles at 1 A g⁻¹). The excellent electrochemical capacitive performance is attributed to its 3D network structure and the synergistic effects among the three components that make the composites obtain both pseudocapacitance and double-layer capacitance.

Binder-free 2D titanium carbide (MXene)/carbon nanotube composites for high-performance lithium-ion capacitors

Two-dimensional (2D) MXenes have a very good application prospect in the field of electrochemical energy storage due to their metallic conductivity, high volumetric capacity, mechanical and thermal stability. Herein, we report the preparation of titanium carbide (Ti3C2Tx)/carbon nanotube (CNT) flexible self-supporting composite films by vacuum filtration. The CNTs can effectively prevent Ti3C2Tx from stacking and improve the electrochemical performance. The as-fabricated Ti3C2Tx/CNT film shows a high reversible capacity of 489 mA h g-1 at a current density of 50 mA g-1 together with good cycling performance. The full-cell lithium-ion capacitor (LIC) is assembled using the Ti3C2Tx/CNT film as the anode and activated carbon as the cathode. The LIC exhibits a high energy density of 67 Wh kg-1 (based on the total weight of the anode and the cathode), and a good capacity retention of 81.3% after 5000 cycles. These results suggest that Ti3C2Tx-CNT films are promising as anode materials for lithium ion capacitors.

Towards flexible solid-state supercapacitors for smart and wearable electronics

Flexible solid-state supercapacitors (FSSCs) are frontrunners in energy storage device technology and have attracted extensive attention owing to recent significant breakthroughs in modern wearable electronics. In this study, we review the state-of-the-art advancements in FSSCs to provide new insights on mechanisms, emerging electrode materials, flexible gel electrolytes and novel cell designs. The review begins with a brief introduction on the fundamental understanding of charge storage mechanisms based on the structural properties of electrode materials. The next sections briefly summarise the latest progress in flexible electrodes (i.e., freestanding and substrate-supported, including textile, paper, metal foil/wire and polymer-based substrates) and flexible gel electrolytes (i.e., aqueous, organic, ionic liquids and redox-active gels). Subsequently, a comprehensive summary of FSSC cell designs introduces some emerging electrode materials, including MXenes, metal nitrides, metal-organic frameworks (MOFs), polyoxometalates (POMs) and black phosphorus. Some potential practical applications, such as the development of piezoelectric, photo-, shape-memory, self-healing, electrochromic and integrated sensor-supercapacitors are also discussed. The final section highlights current challenges and future perspectives on research in this thriving field.

Carbon nanofibers (CNFs) supported cobalt- nickel sulfide (CoNi2S4) nanoparticles hybrid anode for high performance lithium ion capacitor

Lithium ion capacitors possess an ability to bridge the gap between lithium ion battery and supercapacitor. The main concern of fabricating lithium ion capacitors is poor rate capability and cyclic stability of the anode material which uses sluggish faradaic reactions to store an electric charge. Herein, we have fabricated high performance hybrid anode material based on carbon nanofibers (CNFs) and cobalt-nickel sulfide (CoNi₂S₄) nanoparticles via simple electrospinning and electrodeposition methods. Porous and high conducting CNF@CoNi₂S₄ electrode acts as an expressway network for electronic and ionic diffusion during charging-discharging processes. The effect of anode to cathode mass ratio on the performance has been studied by fabricating lithium ion capacitors with different mass ratios. The surface controlled contribution of CNF@CoNi₂S₄ electrode was 73% which demonstrates its excellent rate capability. Lithium ion capacitor fabricated with CNF@CoNi₂S₄ to AC mass ratio of 1:2.6 showed excellent energy density of 85.4 Wh kg⁻¹ with the power density of 150 W kg⁻¹. Also, even at the high power density of 15 kW kg⁻¹, the cell provided the energy density of 35 Wh kg⁻¹. This work offers a new strategy for designing high-performance hybrid anode with the combination of simple and cost effective approaches.

A novel porous carbon material derived from the byproducts of bean curd stick manufacture for high-performance supercapacitor use

Preparation of heteroatom-functionalized porous carbon derived from byproducts of bean curd stick manufacture as an electrode material for high performance supercapacitors.

Graphene hybridization for energy storage applications

Graphene hybridization principles and strategies for various energy storage applications are reviewed from the view point of material structure design, bulk electrode construction, and material/electrode collaborative engineering.

Ultrathin nickel hydroxide on carbon coated 3D-porous copper structures for high performance supercapacitors

Ultrahigh rate capability, cycle stability, and high energy density supercapacitors supported by the three-dimensional (3D) carbon coated copper structure.

Two-dimensional materials for miniaturized energy storage devices: from individual devices to smart integrated systems

This review summarizes recent advances, key challenges and perspectives regarding two-dimensional materials for miniaturized energy storage devices.

Nonaqueous Hybrid Lithium-Ion and Sodium-Ion Capacitors

Hybrid metal-ion capacitors (MICs) (M stands for Li or Na) are designed to deliver high energy density, rapid energy delivery, and long lifespan. The devices are composed of a battery anode and a supercapacitor cathode, and thus become a tradeoff between batteries and supercapacitors. In the past two decades, tremendous efforts have been put into the search for suitable electrode materials to overcome the kinetic imbalance between the battery-type anode and the capacitor-type cathode. Recently, some transition-metal compounds have been found to show pseudocapacitive characteristics in a nonaqueous electrolyte, which makes them interesting high-rate candidates for hybrid MIC anodes. Here, the material design strategies in Li-ion and Na-ion capacitors are summarized, with a focus on pseudocapacitive oxide anodes (Nb₂ O₅ , MoO₃ , etc.), which provide a new opportunity to obtain a higher power density of the hybrid devices. The application of Mxene as an anode material of MICs is also discussed. A perspective to the future research of MICs toward practical applications is proposed to close.

Organic salt-derived nitrogen-rich, hierarchical porous carbon for ultrafast supercapacitors

Nitrogen-rich, high surface area, hierarchical porous carbons were simply prepared by the pyrolysis of a nitrogen-containing organic salt, and exhibit excellent rate capability in supercapacitors.

Binder free 2D aligned efficient MnO2 micro flowers as stable electrodes for symmetric supercapacitor applications

δ-MnO₂ thin film electrodes (M1) deposited on stainless steel mesh using CBD were used in symmetric supercapacitor device (SSM/M1//M1/SSM) with aqueous 1 M Na₂SO₄ electrolyte. The device shows 138% retention of specific capacitance after 2500 cycles.