Highly Nitrogen-Doped Three-Dimensional Carbon Fibers Network with Superior Sodium Storage Capacity

An Overview of Bacterial Cellulose in Flexible Electrochemical Energy Storage

The emerging generation of flexible energy storage devices has accelerated the research pace in terms of new materials, new processing techniques, and new designs that can meet the demands of mechanical stability upon bending or stretching at an acceptable cost, without compromising their electrochemical performance. Among the materials currently explored, biomass-derived materials have received extensive attention, because they are renewable, low in cost, earth-abundant and structurally diverse. This review is focused on fundamentals and applications of the bio-derived material bacterial cellulose (BC) in flexible electrochemical energy storage systems. Specifically, recent advances are summarized in the utilization of BC in stretchable substrates, carbonaceous species, and scaffolds for flexible core component construction. Finally, several perspectives related to BC-based materials for flexible electrochemical energy storages are proposed, aiming to provide possible future research directions in these fields.

Polyacrylamide hydrogel-derived three-dimensional hierarchical porous N,S co-doped carbon frameworks for electrochemical capacitors

Polyacrylamide hydrogel-derived 3D porous hierarchical N,S co-doped carbon frameworks are purposefully fabricated, and exhibit superior electrochemical capacitance in both alkaline and acidic electrolytes.

Nitrogen-doped graphene–TiOxNy nanocomposite electrode for highly efficient capacitive deionization

A nanocomposite electrode of nitrogen-doped graphene and titanium oxynitride is applied as an effective and efficient electrode to deliver outstanding salt adsorption capacity in a flow-by capacitive deionization (CDI) cell.

Multiscale honeycomb-structured activated carbon obtained from nitrogen-containing mandarin peel: high-performance supercapacitors with significant cycling stability

Electrochemical kinetics on symmetrical supercapacitors fabricated from mandarin peel biomass-activated carbon.

Phosphorus-Doped Hard Carbon Nanofibers Prepared by Electrospinning as an Anode in Sodium-Ion Batteries

Phosphorus-doped hard carbon nanofibers with macroporous structure were successfully synthesized by electrospinning followed by a thermal treatment process using polyacrylonitrile and H₃PO₄ as carbon and phosphorus precursors, respectively. X-ray photoelectron spectroscopy analysis reveals that the doped phosphorus atoms can incorporate into the carbon framework and most of them are connecting with carbon atoms to form P-C bond. The (002) plane interlayer spacing was taken from the X-ray diffraction pattern, which shows a large spacing of 3.83 Å for the obtained P-doped hard carbon nanofibers. When used as an anode in sodium-ion batteries, the as-prepared P-doped hard carbon nanofibers can deliver a reversible capacity of 288 and 103 mAh g^-1 at a current density of 50 mA g^-1 and 2 A g^-1, respectively. After 200 cycles at 50 mA g^-1, the capacity retention of P-doped hard carbon nanofibers still reaches 87.8%, demonstrating good cycling durability. These excellent electrochemical performances of P-doped hard carbon nanofibers can be attributed to the macroporous structure, large interlayer spacing, and the formation of P-C bond.

Metal-Organic-Framework-Derived N-Doped Hierarchically Porous Carbon Polyhedrons Anchored on Crumpled Graphene Balls as Efficient Selenium Hosts for High-Performance Lithium-Selenium Batteries

Developing carbon scaffolds showing rational pore structures as cathode hosts is essential for achieving superior electrochemical performances of lithium-selenium (Li-Se) batteries. Hierarchically porous N-doped carbon polyhedrons anchored on crumpled graphene balls (NPC/CGBs) are synthesized by carbonizing a zeolitic imidazolate framework-8 (ZIF-8)/CGB composite precursor, producing an unprecedented effective host matrix for high-performance Li-Se batteries. Mesoporous CGBs obtained by one-pot spray pyrolysis are used as a highly conductive matrix for uniform polyhedral ZIF-8 growth. During carbonization, ZIF-8 polyhedrons on mesoporous CGBs are converted into N-doped carbon polyhedrons showing abundant micropores, forming a high-surface-area, high-pore-volume hierarchically porous NPC/CGB composite whose small unique pores effectively confine Se during melt diffusion, thereby providing conductive electron pathways. Thus, the integrated NPC/CGB-Se composite ensures high Se utilization originating from complete electrochemical reactions between Se and Li ions. The NPC/CGB-Se composite cathode exhibits high discharge capacities (998 and 462 mA h g^-1 at the 1st and 1000th cycles, respectively, at a 0.5 C current density), good capacity retention (68%, calculated from the 3rd cycle), and excellent rate capability. A discharge capacity of 409 mA h g^-1 is achieved even at an extremely high (15.0 C) current density.

Chemical Foaming Coupled Self-Etching: A Multiscale Processing Strategy for Ultrahigh-Surface-Area Carbon Aerogels

Due to the unique structure, carbon aerogels have always shown great potential for multifunctional applications. At present, it is highly desirable but remains challenging to tailor the microstructures with respect to porosity and specific surface area to further expand its significance. A facile chemical foaming coupled self-etching strategy is developed for multiscale processing of carbon aerogels. The strategy is directly realized via the pyrolysis of a multifunctional precursor (pentaerythritol melamine phosphate) without any special drying process and multiple steps. In the micrometer scale, the macroporous scaffold structures with interconnected and strutted carbon nanosheets are built up by chemical foaming from decomposition of melamine, whereas the meso/microporous nanosheets are formed via self-etching by phosphorus-containing species. The delicately hierarchical structures and record-breaking specific surface area of 2668.4 m² g^-1 render the obtained carbon aerogels great potentials for absorption (324.1-593.6 g g^-1 of absorption capacities for varied organic solvents) and energy storage (338 F g^-1 of specific capacitance). The construction of such novel carbon nanoarchitecture will also shed light on the design and synthesis of multifunctional materials.