In Situ Fast Construction of Ni3S4/FeS Catalysts on 3D Foam Structure Achieving Stable Large-Current-Density Water Oxidation.

By increasing the content of Ni3+, the catalytic activity of nickel-based catalysts for the oxygen evolution reaction (OER), which is still problematic with current synthesis routes, can be increased. Herein, a Ni3+-rich of Ni3S4/FeS on FeNi Foam (Ni3S4/FeS@FNF) via anodic electrodeposition to direct obtain high valence metal ions for OER catalyst is presented. XPS showed that the introduction of Fe not only further increased the Ni3+ concentration in Ni3S4/FeS to 95.02%, but also inhibited the dissolution of NiOOH by up to seven times. Furthermore, the OER kinetics is enhanced by the combination of the inner Ni3S4/FeS heterostructures and the electrochemically induced surface layers of oxides/hydroxides. Ni3S4/FeS@FNF shows the most excellent OER activity with a low Tafel slope of 11.2 mV dec-1 and overpotentials of 196 and 445 mV at current densities of 10 and 1400 mA cm-2, respectively. Furthermore, the Ni3S4/FeS@FNF catalyst can be operated stably at 1500 mA cm-2 for 200 h without significant performance degradation. In conclusion, this work has significantly increased the high activity Ni3+ content in nickel-based OER electrocatalysts through an anodic electrodeposition strategy. The preparation process is time-saving and mature, which is expected to be applied in large-scale industrialization.

A "tug-of-war" effect tunes Li-ion transport and enhances the rate capability of lithium metal batteries.

"Solvent-in-salt" electrolytes (high-concentration electrolytes (HCEs)) and diluted high-concentration electrolytes (DHCEs) show great promise for reviving secondary lithium metal batteries (LMBs). However, the inherently sluggish Li+ transport of such electrolytes limits the high-rate capability of LMBs for practical conditions. Here, we discovered a "tug-of-war" effect in a multilayer solvation sheath that promoted the rate capability of LMBs; the pulling force of solvent-nonsolvent interactions competed with the compressive force of Li+-nonsolvent interactions. By elaborately manipulating the pulling and compressive effects, the interaction between Li+ and the solvent was weakened, leading to a loosened solvation sheath. Thereby, the developed electrolytes enabled a high Li+ transference number (0.65) and a Li (50 µm)‖NCM712 (4 mA h cm-2) full cell exhibited long-term cycling stability (160 cycles; 80% capacity retention) at a high rate of 0.33C (1.32 mA cm-2). Notably, Li (50 µm)‖LiFePO4 (LFP; 17.4 mg cm-2) cells with a designed electrolyte reached a capacity retention of 80% after 1450 cycles at a rate of 0.66C. An 6 Ah Li‖LFP pouch cell (over 250 W h kg-1) showed excellent cycling stability (130 cycles, 96% capacity retention) under practical conditions. This design concept for an electrolyte provides a promising path to build high-energy-density and high-rate LMBs.

Revealing Surfactant Effect of Trifluoromethylbenzene in Medium-Concentrated PC Electrolyte for Advanced Lithium-Ion Batteries.

Despite wide-temperature tolerance and high-voltage compatibility, employing propylene carbonate (PC) as electrolyte in lithium-ion batteries (LIBs) is hampered by solvent co-intercalation and graphite exfoliation due to incompetent solvent-derived solid electrolyte interphase (SEI). Herein, trifluoromethylbenzene (PhCF3 ), featuring both specific adsorption and anion attraction, is utilized to regulate the interfacial behaviors and construct anion-induced SEI at low Li salts' concentration (<1 m). The adsorbed PhCF3 , showing surfactant effect on graphite surface, induces preferential accumulation and facilitated decomposition of bis(fluorosulfonyl)imide anions (FSI- ) based on the adsorption-attraction-reduction mechanism. As a result, PhCF3 successfully ameliorates graphite exfoliation-induced cell failure in PC-based electrolyte and enables the practical operation of NCM613/graphite pouch cell with high reversibility at 4.35 V (96% capacity retention over 300 cycles at 0.5 C). This work constructs stable anion-derived SEI at low concentration of Li salt by regulating anions-co-solvents interaction and electrode/electrolyte interfacial chemistries.

Passivating Lithiated Graphite via Targeted Repair of SEI to Inhibit Exothermic Reactions in Early-Stage of Thermal Runaway for Safer Lithium-Ion Batteries.

The self-exothermic in early stage of thermal runaway (TR) is blasting-fuse for Li-ion battery safety issues. The exothermic reaction between lithiated graphite (LiCx ) and electrolyte accounts for onset of this behavior. However, preventing the deleterious reaction still encounters hurdles. Here, we manage to inhibit this reaction by passivating LiCx in real time via targeted repair of SEI. It is shown that 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane (D3 F) can be triggered by LiCx to undergo ring-opening polymerization at elevated temperature, so as to targeted repair of fractured SEI. Due to the high thermal stability of polymerized D3 F, exothermic reaction between LiCx and electrolyte is inhibited. As a result, the self-exothermic and TR trigger temperatures of pouch cell are increased from 159.6 and 194.2 °C to 300.5 and 329.7 °C. This work opens up a new avenue for designing functional additives to block initial exothermal reaction and inhibit TR in early stage.

Why does the capacity of vanadium selenide based aqueous zinc ion batteries continue to increase during long cycles?

At present, rechargeable aqueous zinc ion batteries (RZIBs) have become a rising star and highly sought after in the field of new energy. While vanadium-based RZIBs often exhibit an anomaly of increased long-cycle capacity, which has not been explored in depth. Nevertheless, it is critical to understand this phenomenon to develop high-performance RZIBs. Therefore, this study investigated the growth mechanism of VSe2-based RZIBs using VSe2/MXene as the cathode material via in-situ and ex-situ characterization techniques and electrochemical measurements. Experimental results indicated that with the interaction/extraction of Zn2+/H+ in the host material during cycling, an obvious oxidation reaction occurs at high voltage, and the formed vanadium oxide further reacts with Zn2+ from the electrolyte. As a result, Zn0.25V2O5·H2O is continuously produced and accumulated, contributing to the increasing capacity of the prepared RZIBs.

A Fe3N/carbon composite electrocatalyst for effective polysulfides regulation in room-temperature Na-S batteries.

The practical application of room-temperature Na-S batteries is hindered by the low sulfur utilization, inadequate rate capability and poor cycling performance. To circumvent these issues, here, we propose an electrocatalyst composite material comprising of N-doped nanocarbon and Fe3N. The multilayered porous network of the carbon accommodates large amounts of sulfur, decreases the detrimental effect of volume expansion, and stabilizes the electrodes structure during cycling. Experimental and theoretical results testify the Fe3N affinity to sodium polysulfides via Na-N and Fe-S bonds, leading to strong adsorption and fast dissociation of sodium polysulfides. With a sulfur content of 85 wt.%, the positive electrode tested at room-temperature in non-aqueous Na metal coin cell configuration delivers a reversible capacity of about 1165 mA h g-1 at 167.5 mA g-1, satisfactory rate capability and stable capacity of about 696 mA h g-1 for 2800 cycles at 8375 mA g-1.

Design of an amperometric glucose oxidase biosensor with added protective and adhesion layers.

Enzymes have demonstrated great potential in the development of advanced electroanalysis devices due to their unique recognition and catalytic properties. However, unsatisfactory stability and limited electron communication of traditional enzyme sensors seriously hinder their large-scale application. In this work, a simple and effective method is proposed to improve the stability of enzyme sensors by using sodium hyaluronate (SH) as a protective film, MXene-Ti3C2/Glucose oxidase (GOD) as the reaction layer, and chitosan (CS) /reduced graphene oxide (rGO) as the adhesion layer. Results demonstrate that the repeatability of the designed sensor increased by 73.3% after improving the adhesion between the reaction layer and the current collector and that its response ability was greatly enhanced. Moreover, the long-term stability of the electrode surface with SH protective film proved to be superior than that without protective film, which suggests that this design can effectively improve the overall performance of the enzyme biosensor. This work proposed a multi-tier synergistic approach for improving the reliability of enzyme sensors. Graphical abstract Our proposed protective and adhesion layer can greatly improve the stability of enzyme sensor and realize the rapid detection of glucose in serum sample.

A self-healing neutral aqueous rechargeable Zn/MnO2 battery based on modified carbon nanotubes substrate cathode.

Rechargeable aqueous Zn/MnO2 batteries show great potential for grid-scale storage due to their low cost, high safety, and energy density, yet suffer from continuous capacity decay during operation. Therefore, this work proposes a capacity self-healing aqueous Zn/MnO2 (Zn/cCNTs-MnO2) battery using carboxyl-modified carbon nanotubes (cCNTs) as the cathode substrate, ZnSO4 + MnSO4 mixed aqueous solution as the electrolyte, and Zn foil as the anode. Based on the controllable electrodeposition reaction of MnO2, the specific capacity of Zn/cCNTs-MnO2 batteries can be achieved or recovered by operating several cycles under a low current density (0.1 mA cm-2). Then, the batteries can stably perform under a high current density (1 mA cm-2). By repeating the above steps, a capacity self-healing usage scheme was established, which can significantly improve the cycling performance of Zn/cCNTs-MnO2 batteries. Moreover, the results of the proposed Zn/cCNTs-MnO2 batteries verify the MnO2 electrodeposition mechanism and introduce a novel method for the development of durable aqueous rechargeable Zn/MnO2 batteries.

Highly Efficient Sodium-Ion Storage Enabled by an rGO-Wrapped FeSe2 Composite.

Exploitation of superior anode materials is a key step to realize the pursuit of high-performance sodium-ion batteries. In this work, a reduced graphene oxide-wrapped FeSe2 (FeSe2 @rGO) composite derived from a metal-organic framework (MOF) was synthesized to act as the anode material of sodium-ion batteries. The MOF-derived carbon framework with high specific surface area could relieve the large volumetric change during cycling and ensure the structural stability of electrode materials. Besides, the rGO conductive network allowed to promote the electron transfer and accelerate reaction kinetics as well as to provide a protection role for the internal FeSe2 . As a result, the FeSe2 @rGO composite exhibited a high capacity of 350 mAh g-1 after 600 cycles at 5 A g-1 . Moreover, in situ XRD was conducted to explore the reaction mechanism of the FeSe2 @rGO composite upon sodiation/de-sodiation. Importantly, the presented method for the synthesis of MOF-derived materials wrapped by rGO could not only be used for FeSe2 @rGO-based sodium-ion batteries but also for the different transition metal-based composite materials for electrochemical devices, such as water splitting and sensors.

Puzzle-inspired carbon dots coupled with cobalt phosphide for constructing a highly-effective overall water splitting interface.

Inspired by the structure of puzzles, bombyx mori silk-derived carbon dots (CDs) with abundant negative groups, as jigsaw pieces, were combined with nano-CoP to create a highly effective electrocatalytic interface. The hollow cavity and thin wall of the bamboo-like CDs/CoP nanoarray is beneficial to produce more H˙ radicals and accelerate water decomposition.

(001) Facet-Dominated Hierarchically Hollow Na2Ti3O7 as a High-Rate Anode Material for Sodium-Ion Capacitors.

Sodium-ion capacitors (SICs) have shown great potential to combine the merits of high-power capability of traditional capacitors and high energy capability of batteries. However, the sluggish kinetics and inferior stability of conventional sodium-ion storage anode materials are major challenges for the practical utilization of SICs. In this work, interconnected urchin-like hollow Na2Ti3O7 (Na2Ti3O7-IcUH) chains were designed and prepared by a simple one-step template-assisting method. Through a variety of controlled experiments, we explored how to effectively engineer the crystal-oriented growth and string the urchin-like spheres together. Benefiting from its urchin-like hollow structure and fully exposed (001) facet, the resulting Na2Ti3O7-IcUH exhibits a superior rate capability of 96.2 mA h g-1 at 5 A g-1. Meanwhile, the interconnected three-dimensional primary structure endows Na2Ti3O7-IcUH with excellent cyclic stability (15% capacity loss at 5 A g-1 after 2000 cycles). By coupling with commercial active carbon, the assembled SIC successfully demonstrates a energy density of 134.3 W h kg-1 at a power density of 125 W kg-1 and 38.2 W h kg-1 at a high-power density of 2500 W kg-1, as well as a superior capacity retention of 75% after 2000 cycles at 2 A g-1 within 1-4 V.