Flexible aqueous Cr-ion hybrid supercapacitors with remarkable electrochemical properties in all climates.

The integration of hostless battery-like metal anodes for hybrid supercapacitors is a realistic design method for energy storage devices with promising future applications. With significant Cr element deposits on Earth, exceptionally high theoretical capacity (1546 mAh g-1), and accessible redox potential (-0.74 V vs. reversible hydrogen electrode) of Cr metals, the design of Cr anodes has rightly come into our focus. This work presents a breakthrough design of a flexible Cr-ion hybrid supercapacitor (CHSC) based on a porous graphitized carbon fabric (PGCF) substrate prepared by K2FeO4 activation. In the CHSC device, PGCF acts as both a current collector and cathode material due to its high specific surface area and superior conductivity. The use of a highly concentrated LiCl-CrCl3 electrolyte with high Cr plating/stripping efficiency and excellent antifreeze properties enables the entire PGCF-based CHSC to achieve well-balanced performance in terms of energy density (up to 1.47 mWh cm-2), power characteristics (reaching 9.95 mW cm-2) and durability (95.4% capacity retention after 30,000 cycles), while realizing it to work well under harsh conditions of -40 °C. This work introduces a new concept for low-temperature energy storage technology and confirms the potential application of Cr anodes in hybrid supercapacitors.

A highly sensitive electrochemical biosensor for protein based on a tetrahedral DNA probe, N- and P-co-doped graphene, and rolling circle amplification.

A tetrahedral DNA probe can effectively overcome the steric effects of a single-stranded probe to obtain well-controlled density and minimize nonspecific adsorption. Herein, a highly sensitive electrochemical biosensor is fabricated for determination of protein using a tetrahedral DNA probe and rolling circle amplification (RCA). N- and P-co-doped graphene (NP-rGO) is prepared, and AuNPs are then electrodeposited on it for DNA probe immobilization. Benefitting from the synergistic effects of the excellent electrical conductivity of NP-rGO, the stability of the tetrahedral DNA probe and the signal amplification of RCA, the biosensor achieves a low limit of 3.53 × 10-14 M for thrombin and a wide linear range from 1 × 10-13 to 1 × 10-7 M. This study provides a sensitive and effective method for the detection of protein in peripheral biofluids, and paves the way for future clinical diagnostics and treatment of disease. Graphical abstract.

Urchin-like (NH4)2V10O25·8H2O hierarchical arrays with significantly expanded interlayer spacing for superior aqueous zinc-ion batteries.

The practical application of zinc ion batteries (ZIBs) can be facilitated by designing cathode materials with unique structures that can overcome the critical problems of slow reaction kinetics and large volume expansion associated with the intercalation reaction of divalent zinc ions. In this study, a novel urchin-like (NH4)2V10O25·8H2O assembled from nanorods was synthesized by a simple hydrothermal method, noted as U-NVO. The interlayer organic pillar of cetyltrimethylammonium cation (CTAB) has been intercalated between layers to regulate the interlayer microstructure and expand the interlayer spacing to 1.32 nm, which effectively increased the contact between the electrode and electrolyte interface and shortened the diffusion path of electrolyte ions. The interlayer pillars of structural H2O and NH4+ provide a flexible framework structure and enhance the cohesion of the layered structure, which helps to maintain structural stability during the charging and discharging process, resulting in long-term durability. These unique properties result in the U-NVO cathodes demonstrating high specific capacity (401.7 mA h g-1 at 0.1 A g-1), excellent rate capability (99.6 % retention from 0.1 to 5 A g-1 and back to 0.1 A g-1), and long-term cycling performance (∼87.5 % capacity retention after 2600 cycles). These results offer valuable insights into the design of high-performance vanadium oxide cathode materials.

MoSe2 hollow nanospheres with expanded selenide interlayers for high-performance aqueous zinc-ion batteries.

Transition metal dichalcogenides (TMDs) as materials for aqueous zinc-ion batteries (ZIBs) have received a lot of interest because of their large theoretical capacity and unique layered structure. However, the sluggish kinetics and inferior cyclic stability limit the usefulness of ZIBs. In the present investigation, the interlayer spacing enlarged MoSe2 hollow nanospheres comprised of nanosheets with ultrathin shells have been successfully synthesized through a combined strategy of template assistance and anion-exchange reaction. The hierarchical ultrathin nanosheets and hollow structure effectively suppress the agglomeration of pure nanosheets and ameliorate volume fluctuations induced by ion migration during (dis)charging/charging. The interlayer expansion provides good channels for the transport of Zn2+ ions and speeds up the insertion/extraction of Zn2+. In addition, in-situ carbon modification can significantly improve electronic conductivity. Therefore, the electrode prepared from MoSe2 hollow nanospheres with enlarged interlayer spacing not only exhibits outstanding cycle stability (capacity retention of 94.5% after 1600 cycles) but also exhibits high-rate capability (266.1 mA h g-1 at 0.1 A g-1 and 203.6 mA h g-1 at 3 A g-1). This work could provide new insights into the design of cathode using TMDs of hollow structure for Zn2+ storage.

Engineering stable and fast sodium diffusion route by constructing hierarchical MoS2 hollow spheres.

Two-dimensional layered transition metal dichalcogenides, such as MoS2, have been considered to be a promising anode material for sodium storage. However, their performance have been limited by the sluggish sodium diffusion kinetics. In this work, high performance anode material was obtained through constructing hierarchical MoS2 nanosheets assembled hollow spheres. The used self-templating method show more feasibility than the commonly reported template removal-involved routes. The prepared hollow structure can also provide rapid and stable electron/sodium ion transport without the assistance of conducting substrates, which enables the MoS2 anodes exhibit a high specific capacity of 527 mAh g-1 at 0.1 A g-1. Even at a high current density of 1 A g-1, capacity of 357 mAh g-1 can still be obtained after 500 cycles (capacity retention ~94.5%). This work provides a facile way towards high performance MoS2 anode materials for sodium-ion battery.

Interconnected MoS2 on 2D Graphdiyne for Reversible Sodium Storage.

In this study, graphdiyne (GDY) was first reported as a substrate material for sodium-ion batteries (SIBs). The creative hybridization of GDY and molybdenum disulfide (MoS2) endows the composite with unique heterostructural and morphological advantages that boost the charge transport rate and enhance the battery discharge properties. Electrochemical results indicated that the MoS2@GDY anode displays a considerable discharge capacity of up to 328 mAh g-1 at 1000 mA g-1. A capacity retention of 93% even at testing current back to 200 mA g-1 suggests superior rate characteristics. An outstanding stable cyclic performance of 217 mAh g-1 is obtained at a high testing density. The attractive results not only demonstrate that GDY could be used not only as an effective conductive substrate to prevent the host material from agglomerating in the electrochemical process but also provide a novel design for fabricating efficient electrode materials for future energy-storage systems.