Interlayer Modulation of Layered Transition Metal Compounds for Energy Storage.

Layered transition metal compounds are one of the most important electrode materials for high-performance electrochemical energy storage devices, such as batteries and supercapacitors. Charge storage in these materials can be achieved via intercalation of ions into the interlayer channels between the layer slabs. With the development of lithium-beyond batteries, larger carrier ions require optimized interlayer space for the unrestricted diffusion in the two-dimensional channels and effectively shielded electrostatic interaction between the slabs and interlayer ions. Therefore, interlayer modulation has become an efficient and promising approach to overcome the problems of sluggish kinetics, structural distortion, irreversible phase transition, dissolution of some transition metal elements, and air instability faced by these materials and thus enhance the overall electrochemical performance. In this review, we focus on the interlayer modulation of layered transition metal compounds for various batteries and supercapacitors. Merits of interlayer modulation on the charge storage procedures of charge transfer, ion diffusion, and structural transformation are first discussed, with emphasis on the state-of-art strategies of intercalation and doping with foreign species. Following the obtained insights, applications of modified layered electrode materials in various batteries and supercapacitors are summarized, which may guide the future development of high-performance and low-cost electrode materials for energy storage.

Suppressed Layered-to-Spinel Phase Transition in δ-MnO2 via van der Waals Interaction for Highly Stable Zn/MnO2 Batteries.

Although birnessite-type manganese dioxide (δ-MnO2 ) with a large interlayer spacing (≈7 Å) is a promising cathode candidate for aqueous Zn/MnO2 batteries, the poor structural stability associated with Zn2+ intercalation/deintercalation limits its further practical application. Herein, δ-MnO2 ultrathin nanosheets are coupled with reduced graphene oxide (rGO) via van der Waals (vdW) self-assembly in a vacuum freeze-drying process. It is interesting to find that the presence of vdW interaction between δ-MnO2 and rGO can effectively suppress the layered-to-spinel phase transition in δ-MnO2 during cycling. As a result, the coupled δ-MnO2 /rGO hybrid cathode with a sandwich-like heterostructure exhibits remarkable cycle performance with 80.1% capacity retained after 3000 cycles at 2.0 A g-1 . The first principle calculations demonstrate that the strong interfacial interaction between δ-MnO2 and rGO results in improved electron transfer and strengthened layered structure for δ-MnO2 . This work establishes a viable strategy to mitigate the adverse layered-to-spinel phase transition in layered manganese oxide in aqueous energy storage systems.

Stabilizing Layered Structure in Aqueous Electrolyte via O2-Type Oxygen Stacking.

Despite the high energy density of O3-type layered cathode materials, the short cycle life in aqueous electrolyte hinders their practical applications in aqueous lithium-ion batteries (ALIBs). In this work, it is demonstrated that the structural stability of layered LiCoO2 in aqueous electrolyte can be remarkably improved by altering the oxygen stacking from O3 to O2. As compared to the O3-type LiCoO2 , the O2-type LiCoO2 exhibits significantly improved cycle performance in neutral aqueous electrolyte. It is found that the structural degradation caused by electrophilic attack of proton can be effectively mitigated in O2-type layered structure. With O2 stacking, CoO6 octahedra in LiCoO2 possess stronger CoO bonds while Co migration from Co layer to Li layer is strongly hampered, resulting in enhanced structural stability against proton attack and prolonged cycle life in aqueous electrolyte. The findings in this work reveal that regulating oxygen stacking sequence is an effective strategy to improve the structural stability of layered materials for ALIBs.

Sacran polysaccharide improves atopic dermatitis through inhibiting Th2 type immune response.

AIMS: This study was aimed to explore whether sacran polysaccharide has a therapeutic effect on atopic dermatitis (AD) and its possible mechanisms. MATERIALS AND METHODS: 2, 4-dinitrochlorobenzene (DNCB)-induced AD mice were treated with 0.2% Sacran, 0.5% Sacran and 0.1% tacrolimus. Through scoring dermatitis severity, measuring ear thickness, cracking behavior, open field test, we evaluated the therapeutic effect of Sacran on DNCB-induced AD mice. CD4+ T cells and CD8+ T cells were evaluated by flow cytometry. The relative expression of Ifng and Il4 were measured by real-time quantitative PCR. KEY FINDINGS: Sacran could relieved the symptoms of DNCB-induced AD mice, such as AD score, ear thickness, and IgE release. Sacran may alleviate dermatitis by inhibiting Th2 activation and reducing IgE release. SIGNIFICANCE: Our research further proved that polysaccharide Sacran has anti-dermatitis effects, and also clarified its mechanism of alleviating dermatitis by inhibiting the activation of Th2 cells and reducing the release of IgE, which provides a theoretical basis for the future clinical transformation of polysaccharide Sacran.

Fluorine Triggered Surface and Lattice Regulation in Anatase TiO2- x Fx Nanocrystals for Ultrafast Pseudocapacitive Sodium Storage.

Sodium-ion batteries (SIBs) have been considered as one of the most promising secondary battery techniques for large-scale energy storage applications. However, developing appropriate electrode materials that can satisfy the demands of long-term cycling and high energy/power capabilities remains a challenge. Herein, a fluorine modulation strategy is reported that can trigger highly active exposed crystal facets in anatase TiO2- x Fx , while simultaneously inducing improved electron transfer and Na+ diffusion via lattice regulation. When tested in SIBs, the optimized fluorine doped TiO2- x Fx nanocrystals exhibit a high reversible capacity of 275 mA h g-1 at 0.05 A g-1 , outstanding rate capability (delivering 129 mA h g-1 at 10 A g-1 ), and remarkable cycling stability with 91% capacity retained after 6000 cycles at 2 A g-1 . Importantly, the optimized TiO2- x Fx nanocrystals are dominated by pseudocapacitive Na+ storage, which can be attributed to the fluorine induced surface and lattice regulation, enabling ultrafast electrode kinetics.

When Layered Nickel-Cobalt Silicate Hydroxide Nanosheets Meet Carbon Nanotubes: A Synergetic Coaxial Nanocable Structure for Enhanced Electrocatalytic Water Oxidation.

Developing robust earth-abundant electrocatalysts for oxygen evolution reaction (OER) is an ongoing scientific challenge, which is coupled with a number of important electrochemical processes and many key renewable energy systems, such as water splitting, rechargeable metal-air batteries, and regenerative fuel cells. Here, we proposed a rational design and fabrication of the synergetic coaxial nanocable structures by intimate growth of the layered nickel-cobalt silicate hydroxide nanosheets on the outer surfaces of multiwalled carbon nanotubes (MWCNTs@NCS) and demonstrated their high efficiency in electrocatalytic OER from water splitting. The electrocatalytic activities of the MWCNTs@NCS were found to be significantly higher than that of bare NCS and pristine MWCNTs, synergetically determining by such the constituted individual components. Among them, the MWCNTs@NCS-2 exhibited best electrocatalytic OER performance, showing a small OER onset potential, large anodic current and long-term durability, which was favorably comparable to the previously reported NiCo-based OER electrocatalysts in alkaline electrolytes. To the best of our knowledge, this was a first example on the earth-abundant metal silicate hydroxides utilized in electrochemical water splitting.