Enhancing Energy Storage Devices with Biomacromolecules in Hybrid Electrodes

The development of energy storage devices with higher energy and power outputs, and long cycling stability is urgently required in the pursuit of the expanding challenges of electrical energy storage. The utilization of biologically renewable redox compounds holds a great potential in designing sustainable energy storage systems and contributes in reducing the dependence on fossil fuels for energy materials. Quinones are the principal redox centers in natural organic materials and play a key role as charge storage electrode materials because of their abundance, multiple forms and integration into the materials flow through the biosphere. Electrical energy storage devices and systems can be significantly improved by the combination of scalable quinone‐based biomaterials with good electronic conductors. This review uses recent examples to show how biopolymers are providing new directions in the development of renewable biohybrid electrodes for energy storage devices.     

Superelastic Hybrid CNT/Graphene Fibers for Wearable Energy Storage

The demands for wearable technologies continue to grow and novel approaches for powering these devices are being enabled by the advent of new electromaterials and novel fabrication strategies. Herein, a novel approach is reported to develop superelastic wet‐spun hybrid carbon nanotube graphene fibers followed by electrodeposition of polyaniline to achieve a high‐performance fiber‐based supercapacitor. It is found that the specific capacitance of hybrid carbon nanotube (CNT)/graphene fiber is enhanced up to ≈39% using a graphene to CNT fiber ratio of 1:3. Fabrication of spring‐like coiled fiber coated with an elastic polymer shows an extraordinary elasticity capable of 800% strain while affording a specific capacitance of ≈138 F g^?1. The elastic rubber coating enables extreme stretchability and enabling cycles with up to 500% strain for thousands of cycles with no significant change in its performance. Multiple supercapacitors can be easily assembled in series or parallel to meet specific energy and power needs.     

A Calcium‐Ion Hybrid Energy Storage Device with High Capacity and Long Cycling Life under Room Temperature

Ca‐ion based devices are promising candidates for next‐generation energy storage with high performance and low cost, thanks to its multielectrons, superior kinetics, as well as abundance (2500 times lithium). Because of the lack of an appropriate combination of suitable electrode materials and electrolytes, it is unsuccessful to attain a satisfactory performance on complete Ca‐ion energy storage devices. Here, the multiion reaction strategy is defined to construct a complete Ca‐ion energy storage device and a capacitor–battery hybrid mechanism is deliberately adopted. Profiting from the elaborate design, it exhibits a high reversible capacity of 92 mAh g^?1, unmatchable rate capability, and a high capacity retention of 84% over 1000 cycles under room temperature, which is the best performance of reported Ca‐based energy storage devices.     

Hollow Carbon Spheres and Their Hybrid Nanomaterials in Electrochemical Energy Storage

Electrochemical energy storage is of extraordinary importance for fulfilling the utilization of renewable and sustainable energy sources. There is an increasing demand for energy storage devices with high energy and power densities, prolonged stability, safety, and low cost. In the past decade, numerous research efforts have been devoted to achieving these requirements, especially in the design of advanced electrode materials. Hollow carbon spheres (HCS) derived nanomaterials combining the advantages of 3D HCS and porous structures have been considered as alternative electrode materials for advanced energy storage applications, due to their unique features such as high surface‐to‐volume ratios, encapsulation capability, together with outstanding chemical and thermal stability. In this review, the authors first present a comprehensive overview of the synthetic strategies of HCS, and elucidate the design and synthesis of HCS‐derived nanomaterials including various types of HCS and their nanohybrids. Additionally, their significant roles as electrode materials for supercapacitors, lithium‐ion or sodium‐ion batteries, and sulfur hosts for lithium sulfur batteries are highlighted. Finally, current challenges in the synthesis of HCS and future directions in HCS‐derived nanomaterials for energy storage applications are proposed.     

Metamorphosis of Seaweeds into Multitalented Materials for Energy Storage Applications

Transition metal ion dissolution due to hydrofluoric acid attack is a long‐standing issue in the Mn‐based spinel cathode materials of lithium‐ion batteries (LIBs). Numerous strategies have been proposed to address this issue, but only a fragmentary solution has been established. In this study, reported is a seaweed‐extracted multitalented material, namely, agar, for high‐performance LIBs comprising Mn‐based cathode materials at a practical loading density (23.1 mg cm^?2 for LiMn₂O₄ and 10.9 mg cm^?2 for LiNi_0.5Mn_1.5O₄, respectively). As a surface modifier, 3‐glycidoxypropyl trimethoxysilane (GPTMS) is employed to enable the agar to have different phase separation behaviors during the nonsolvent‐induced phase separation process, thus eventually leading to the fabrication of an outstanding separator membrane that features a well‐defined porous structure, superior mechanical robustness, high ionic conductivity, and good thermal stability. The GPTMS‐modified agar separator membrane coupled with a pure agar binder to the LiNi_0.5Mn_1.5O₄/graphite full cell leads to exceptional improvement in electrochemical performance outperforming binders and separator membrane in current commercial products even at 55 °C; this improvement is due to beneficial features such as Mn²⁺ chelation and PF₅ stabilizing capabilities. This study is believed to provide insights into the potential energy applications of natural seaweeds.     

Transition Metal Sulfides Based on Graphene for Electrochemical Energy Storage

Transition metal sulfides, as an important class of inorganics, can be used as excellent electrode materials for various types of electrochemical energy storage, such as lithium‐ion batteries, sodium‐ion batteries, supercapacitors, and others. Recent works have identified that mixing graphene or graphene derivatives with transition metal sulfides can result in novel composites with better electrochemical performance. This review summarizes the latest advances in transition metal sulfide composites with graphene or graphene derivatives. The synthetic strategies and morphologies of these composites are introduced. The authors then discuss their applications in lithium‐ion batteries, sodium‐ion batteries, and supercapacitors. Finally, the authors give their personal viewpoints about the challenges and opportunities for the future development about this direction.     

Metal Sulfide Hollow Nanostructures for Electrochemical Energy Storage

Metal sulfide hollow nanostructures (MSHNs) have received intensive attention as electrode materials for electrical energy storage (EES) systems due to their unique structural features and rich chemistry. Here, we summarize recent research progress in the rational design and synthesis of various metal sulfide hollow micro‐/nanostructures with controlled shape, composition and structural complexity, and their applications to lithium ion batteries (LIBs) and hybrid supercapacitors (HSCs). The current understanding of hollow structure control, including single‐shelled, yolk‐shelled, multi‐shelled MSHNs, and their hybrid micro‐/nanostructures with carbon (amorphous carbon nanocoating, graphene and hollow carbon), is focused on. The importance of proper structural and compositional control on the enhanced electrochemical properties of MSHNs is emphasized. A relationship between structural and compositional engineering with improved electrochemical activity of MSHNs is sought, in order to shed some light on future electrode design trends for next‐generation EES technologies.     

Textile‐Based Electrochemical Energy Storage Devices

In the past few years, insensitive attentions have been drawn to wearable and flexible energy storage devices/systems along with the emergence of wearable electronics. Much progress has been achieved in developing flexible electrochemical energy storage devices with high end‐use performance. However, challenges still remain in well balancing the electrochemical properties, mechanical properties, and the processing technologies. In this review, a specific perspective on the development of textile‐based electrochemical energy storage devices (TEESDs), in which textile components and technologies are utilized to enhance the energy storage ability and mechanical properties of wearable electronic devices, is provided. The discussion focuses on the material preparation and characteristics, electrode and device fabrication strategies, electrochemical performance and metrics, wearable compatibility, and fabrication scalability of TEESDs including textile‐based supercapacitors and lithium‐ion batteries.