Search

Organic compounds have become a potentially important choice for a new generation of energy-storage electrode materials due to their designability, flexibility, green sustainability, and abundance. However, the applications of organic electrode materials are still limited because of their dissolution in electrolytes and low electrical conductivity, which in turn cause poor cycling stability. Here, for the first time, we report 2-amino-4-thiazole-acetic acid (ATA) and its sodium salt, sodium 2-amino-4-thiazol-derived polymer (PATANa), as an anode. The PATANa showed a two-dimensional (2D) nanosheet structure, offering a larger contact area with the electrolyte and a shorter ion-migration path, which improved the ion-diffusion kinetics. The polymer showed excellent cycling stability and outstanding rate capability when tested as an anode for sodium-ion batteries (SIBs). It could deliver a high reversible specific capacity of 303 mA h g−1 at 100 mA g−1 for 100 cycles and maintain a high discharge capacity of 190 mA h g−1 after 1000 long cycle numbers even at a high current density of 1000 mA g−1. This approach of salinizing the polymer opens a new way to develop anode materials for sodium-ion batteries. [ABSTRACT FROM AUTHOR]

Organic electrode materials with environmental friendliness and design flexibility at the molecular level are promising substitutes for inorganic materials as cathodes for sodium ion batteries (SIBs). However, traditional organic electrode materials usually exhibit poor cycling stability, mainly due to the dissolution of small organic molecules in electrolytes, and low electronic conductivity. Herein, conjugated porous polyimide poly(2,6-diaminoanthraquinone) benzamide (CP-PDAB) was prepared from 2,6-diaminoanthraquinone and pyromellitic dianhydride by a simple polycondensation reaction. The obtained CP-PDAB has disordered aggregates with a porous and loose structure, facilitating the penetration of the electrolyte and buffering the volume change during charging/discharging. The conjugated skeleton with electron delocalization offers the benefits of structural stability, insolubility in electrolyte and high electronic conductivity. When evaluated as a cathode for SIBs, it can retain a high reversible discharge capacity of 141 mA h g−1 at 500 mA g−1 for 100 cycles, and can maintain a high specific capacity of 71 mA h g−1 at 10 A g−1 after 500 cycles. This work demonstrates the potential application of organic materials containing a conjugated skeleton, porous and loose structure for next-generation electrochemical energy storage devices. [ABSTRACT FROM AUTHOR]

The need for improving the energy conversion efficiency of proton exchange membrane fuel cells (PEMFCs) has motivated the development of advanced electrocatalysts with desirable activity and durability. Pt-Based intermetallic compounds, featuring atomically ordered structures, have long been considered to be very promising alternatives to widely employed Pt and Pt alloy (solid solutions) catalysts. To facilitate the practical application of Pt-based intermetallics in PEMFCs, effective strategies have been developed to further improve their catalytic activity and durability over the last decade. This feature article overviews the recent advances on the strategies for enhancing the electrochemical performances of Pt-based intermetallic catalysts, which include size control, surface engineering, and composition tuning. Thermodynamic and kinetic perspectives on the formation of the intermetallic phases are summarized to better design the synthesis conditions and realize the size control. After this, the size-control approaches (e.g. coating protection, matrix protection) are illustrated and discussed. We highlight the positive effect of surface engineering and discuss the recently developed methods for surface engineering. Finally, we discuss the thermodynamic feasibility of composition tuning and recent work based on composition-tunable intermetallic electrocatalysts. [ABSTRACT FROM AUTHOR]

With the increasing energy demand of electronic devices and electric vehicles, the achievement of anode materials for lithium-ion batteries with high specific capacity and superior rate capability and cycling stability still remains a challenge. Herein, we report a novel strategy to prepare the core–shell mesoporous single-crystalline MnOx nanofibers@graphene (PSCMnOx@G) through a “spraying–rapid freezing” process. The elastic graphene shell not only improves the conductivity of the electrode but can also substantially inhibit the collapse of MnOx nanofibers (NFs) over continuous discharge–charge cycles. Moreover, the double-exchange interaction of manganese mixed-valence ions further improves the conductivity of manganese oxide, and Li ion diffusion is significantly enhanced by the vertically aligned single-crystalline and mesoporous structure of MnOx NFs. As a result, the PSCMnOx@G exhibits an ultrahigh rate performance (1072 mA h g−1 at 0.1 A g−1 and 419 mA h g−1 at 10 A g−1), which is among the best ever reported for MnOx based anodes, as well as excellent cycling stability (1162 mA h g−1 at 2 A g−1 over 500 cycles). [ABSTRACT FROM AUTHOR]

To achieve high-performance lithium ion batteries (LIBs), tremendous efforts have been devoted to the design of multifunctional electrode materials with a short Li+ diffusion pathway, high electronic conduction, large electrode/electrolyte contact area and efficiency elastic buffer space to accommodate volume change during cycling. However, the design and synthesis of these versatile structures still remain a big challenge. Here, for the first time we present a novel strategy for spatial confinement of ultra-small and highly crystallized ZnFe2O4 nanoparticles (∼12 nm) within double graphene networks constructed by ultra-small graphene sheets (USGNs) and large graphene sheets (GNs). The interconnected double graphene networks can act as a “barrier” for spatially confined growth of ZnFe2O4 and as a “structural buffer” for enhanced cycling stability, as well as electrically conductive paths. As a result, the ZnFe2O4/USGN/GN exhibits a large reversible capacity of 1257 mA h g−1 at 0.1 A g−1, excellent rate capability (575 mA h g−1 at 1 A g−1), and superior cycling stability (706 mA h g−1 at 0.5 A g−1 after 1000 cycles and 475 mA h g−1 at 1 A g−1 even after 2000 cycles). Our strategy can be further extended to the fabrication of other electrode materials for supercapacitors, fuel cells and metal-ion batteries. [ABSTRACT FROM AUTHOR]

Organic small-molecule compounds have become promising cathode materials for high-performance lithium-ion batteries (LIBs) due to their high theoretical capacity, efficient utilization of active sites, low cost, and sustainability. However, severe dissolution and poor electronic conductivity limit their further practical applications. Herein, we have synthesized an insoluble organic small molecule, ferrocenyl-3-(λ 1 -azazyl) pyrazinyl [2,3- f ] [1,10] phenanthrolino-2-amine (FCPD), by grafting ferrocene onto pyrazino[2,3-f] [1,10] phenanthroline-2,3-diamine (PPD). The combination of ferrocene (p-type Fe 2+ moiety) and PPD (n-type C[double bond, length as m-dash]N groups) in a bipolar manner endows the target FCPD cathode with an increased theoretical capacity and a wide voltage window. The highly conjugated π-π aromatic skeleton inside enhances FCPD's electron delocalization and promotes strong interaction between FCPD units. Additionally, the mesoporous structure within the FCPD can provide numerous electroactive sites, contact area, and ion diffusion channels. Benefiting from the bipolar feature, aromatic, and mesoporous structure, the FCPD cathode demonstrates a large capacity of 250 mA h g -1 at 0.1 A g -1 , a long lifespan of 1000 cycles and a high-rate capability of 151 mA h g -1 at 5 A g -1 along with a wide voltage window (1.2-3.8 V). Additionally, in situ synchrotron FT-IR and ex situ XPS reveal its dual ion storage mechanism in depth. Our findings provide essential insights into exploring the molecular design of advanced organic small molecules., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Organic compounds have become a potentially important choice for a new generation of energy-storage electrode materials due to their designability, flexibility, green sustainability, and abundance. However, the applications of organic electrode materials are still limited because of their dissolution in electrolytes and low electrical conductivity, which in turn cause poor cycling stability. Here, for the first time, we report 2-amino-4-thiazole-acetic acid (ATA) and its sodium salt, sodium 2-amino-4-thiazol-derived polymer (PATANa), as an anode. The PATANa showed a two-dimensional (2D) nanosheet structure, offering a larger contact area with the electrolyte and a shorter ion-migration path, which improved the ion-diffusion kinetics. The polymer showed excellent cycling stability and outstanding rate capability when tested as an anode for sodium-ion batteries (SIBs). It could deliver a high reversible specific capacity of 303 mA h g -1 at 100 mA g -1 for 100 cycles and maintain a high discharge capacity of 190 mA h g -1 after 1000 long cycle numbers even at a high current density of 1000 mA g -1 . This approach of salinizing the polymer opens a new way to develop anode materials for sodium-ion batteries.