Rationally Designed Fluorinated Amide Additive Enables the Stable Operation of Lithium Metal Batteries by Regulating the Interfacial Chemistry.

A fluorinated amide molecule with two functional segments, namely, an amide group with a high donor number to bind lithium ions and a fluorine chain to expel carbonate solvents and mediate the formation of LiF, was designed to regulate the interfacial chemistry. As expected, the additive preferably appears in the first solvation sheath of lithium ions and is electrochemically reduced on the anode, and thus an inorganic-rich solid electrolyte interphase is generated. The morphology of deposited lithium metal evolves from brittle dendrites into a granular shape. Consequently, the Li||LiFePO4 cell shows an excellent capacity retention of 92.7% at a high rate of 5 C after 800 cycles. Besides, the Li||LiNi0.8Co0.1Mn0.1O2 cell succeeds to maintain 98.1% of the initial capacity after 100 cycles at 1 C. Our designing of N,N-diethyl- 2,3,3,3-tetrafluoropropionamide (denoted as DETFP) highlights the importance of a "high donor number" and may shed light on the design principles of electrolytes for high performance batteries.

Rational Design of Tungsten Selenide @ N-Doped Carbon Nanotube for High-Stable Potassium-Ion Batteries.

Potassium-ion batteries (PIBs) are deemed as one of the most promising energy storage systems due to their high energy density and low cost. However, their commercial application is far away from satisfactory because of limited suitable electrode materials. Herein, core-shell structured WSe2 @N-doped C nanotubes are rationally designed and synthesized via selenizing WO3 @ polypyrrole for the first time. The large interlayer spacing of WSe2 can facilitate the intercalation/deintercalation of K+ . Meanwhile, the core-shell structured nanotube provides favorable interior void space to accommodate the volume expansion of WSe2 during cycling. Thus, the obtained electrode exhibits superb electrochemical performance with a high capacity of 301.7 mAh g-1 at 100 mA g-1 over 120 cycles, and 122.1 mAh g-1 can remain at 500 mA g-1 even after 1300 cycles. Ex-situ X-ray diffraction analysis reveals the K-ion storage mechanism of WSe2 @N-doped C includes intercalation and conversion reaction. Density function theory (DFT) calculation demonstrates the reasonable diffusion pathway of K+ . In addition, the obtained WSe2 @N-doped C nanotubes have been used as anode material for lithium-ion batteries, which also show good rate performance and high cycle stability. Therefore, this work offers a new methodology for the ration design of new structure electrode materials with long cycle stability.

Construction of Integrated Electrodes with Transport Highways for Pure-Water-Fed Anion Exchange Membrane Water Electrolysis.

The design of high-performance and durable electrodes for the oxygen evolution reaction (OER) is crucial for pure-water-fed anion exchange membrane water electrolysis (AEMWE). In this study, an integrated electrode with vertically aligned ionomer-incorporated nickel-iron layered double hydroxide nanosheet arrays, used on one side of the liquid/gas diffusion layer, is fabricated for the OER. Transport highways in the fabricated integrated electrode, significantly improve the transport of liquid/gas, hydroxide ions, and electron in the anode, resulting in a high current density of 1900 mA cm-2 at 1.90 V in pure-water-fed AEMWE. Specifically, three-electrode and single-cell measurement results indicate that an anion-exchange ionomer can increase the local OH- concentration on the integrated electrodes surface and facilitate the OER for pure-water-fed AEMWE. This study highlights a new approach to fabricating and understanding electrode architecture with enhanced performance and durability for pure-water-fed AEMWE.

Continuous ammonia electrosynthesis using physically interlocked bipolar membrane at 1000 mA cm-2.

Electrosynthesis of ammonia from nitrate reduction receives extensive attention recently for its relatively mild conditions and clean energy requirements, while most existed electrochemical strategies can only deliver a low yield rate and short duration for the lack of stable ion exchange membranes at high current density. Here, a bipolar membrane nitrate reduction process is proposed to achieve ionic balance, and increasing water dissociation sites is delivered by constructing a three-dimensional physically interlocked interface for the bipolar membrane. This design simultaneously boosts ionic transfer and interfacial stability compared to traditional ones, successfully reducing transmembrane voltage to 1.13 V at up to current density of 1000 mA cm-2. By combining a Co three-dimensional nanoarray cathode designed for large current and low concentration utilizations, a continuous and high yield bipolar membrane reactor for NH3 electrosynthesis realized a stable electrolysis at 1000 mA cm-2 for over 100 h, Faradaic efficiency of 86.2% and maximum yield rate of 68.4 mg h-1 cm-2 with merely 2000 ppm NO3- alkaline electrolyte. These results show promising potential for artificial nitrogen cycling in the near future.

Superhydrophilic/Superaerophobic Hierarchical NiP2@MoO2/Co(Ni)MoO4 Core-Shell Array Electrocatalysts for Efficient Hydrogen Production at Large Current Densities.

Rationally constructing low-cost, high-efficiency, and durable electrocatalysts toward the hydrogen evolution reaction at large current densities is imperative for water splitting, especially for large-scale industrial applications. Herein, a hierarchical core-shell NiP2@MoO2/Co(Ni)MoO4 cuboid array electrode with superhydrophilic/superaerophobic properties is successfully fabricated and the formation mechanism of the core-shell structure is systematically investigated. Through an in situ partially converted gas-solid reaction during the phosphating process, Ni and Co elements are leached and rearranged to form NiP2 particles and amorphous CoO as the shell layer and the inner undecomposed Co(Ni)MoO4 crystals serve as the core layer. Because of its seamless core-shell structure and superhydrophilicity/superaerophobicity of hierarchical cuboid arrays, NiP2@MoO2/Co(Ni)MoO4 exhibits superior HER activity in 1 M KOH with only an overpotential of 297 mV to deliver 1000 mA cm-2 and can work steadily for 650 h at 200 mA cm-2. Remarkably, when coupled with NiFe LDH for overall water splitting, it can drive an AA battery with an ultralow cell voltage of 1.49 V to deliver 10 mA cm-2. This work sheds new light on designing large-current-density efficient HER electrocatalysts for large-scale industrial applications.

Lithium Bromide-Induced Organic-Rich Cathode/Electrolyte Interphase for High-Voltage and Flame-Retardant All-Solid-State Lithium Batteries.

Poly(ethylene oxide) (PEO)-based solid electrolyte suffers from limited anodic stability and an intrinsic flammable issue, hindering the achievement of high energy density and safe all-solid-state lithium batteries. Herein, we surprisingly found out that a bromine-rich additive, decabromodiphenyl ethane (DBDPE), could be preferably oxidized at an elevated voltage and decompose to lithium bromide at an elevated potential followed by inducing an organic-rich cathode/electrolyte interphase (CEI) on NCM811 surface, enabling both high-voltage resistance (up to 4.5 V) and flame-retardancy for the PEO-based electrolyte. On the basis of this novel solid electrolyte, all-solid-state Li/NCM811 batteries deliver an average reversible capacity of 151.4 mAh g-1 over the first 150 cycles with high capacity retention (83.0%) and high average Coulombic efficiency (99.7%) even at a 4.5 V cutoff voltage with a unprecedented flame-retardant properties. In view of these exploration, our studies revealed the critical role of LiBr in inducing an organic-rich thin and uniform CEI passivating layer with enhanced lithium ion surface diffusion and high-voltage resistant properties, which provides a new protocol for the further design of a high-voltage PEO-based all-solid-state electrolyte.

Designing Self-Supported Electrocatalysts for Electrochemical Water Splitting: Surface/Interface Engineering toward Enhanced Electrocatalytic Performance.

Electrochemical water splitting is regarded as the most attractive technique to store renewable electricity in the form of hydrogen fuel. However, the corresponding anodic oxygen evolution reaction (OER) and cathodic hydrogen evolution reaction (HER) remain challenging, which exhibit complex reactions and sluggish kinetic behaviors at the triple-phase interface. Material surface and interface engineering provide a feasible approach to improve catalytic activity. Besides, self-supported electrocatalysts have been proven to be highly efficient toward water splitting, because of the regulated catalyst/substrate interface. In this Review, the state-of-the-art achievements in self-supported electrocatalyst for HER/OER have demonstrated the feasibility of surface and interface engineering strategies to boost performance. The six key effective surface/interface engineering approaches for rational catalysts design are systematically reviewed, including defect engineering, morphology engineering, crystallographic tailoring, heterostructure design, catalyst/substrate interface engineering, and catalyst/electrolyte interface regulation. Finally, the challenges and opportunities on the valuable directions are proposed to inspire future investigation of highly active and durable HER/OER electrocatalysts.

Interface Engineering of Binder-Free Earth-Abundant Electrocatalysts for Efficient Advanced Energy Conversion.

Gas-involved electrocatalysts for the hydrogen evolution reaction, oxygen evolution reaction, and oxygen reduction reaction are crucial for many clean and effective energy technologies. The interface chemistry of electrocatalysts plays an important role in the optimization of their catalytic activity and stability. However, these gas-involved reactions exhibit sluggish kinetics and complex reactions at triple-phase interfaces. Thus, interface engineering at multiscale levels plays a decisive role. Binder-free electrocatalysts have gained increasing popularity, owing to their enhanced electron transfer and improved mass diffusion. This Review summarizes the influence of binder-free electrocatalysts with optimized interfaces and emphasizes three key interfaces, including the electrocatalyst/substrate interface, the inner interface of the electrocatalyst, and the electrocatalyst/electrolyte/gas interface, which are integral to determining the properties of gas-involved electrocatalysts, including the electrical conductivity, intrinsic catalytic activity, and mass transfer behavior. Finally, prospects and future challenges for the further development of binder-free electrocatalysts are discussed.

Construction of a Janus MnO2-NiFe Electrode via Selective Electrodeposition Strategy as a High-Performance Bifunctional Electrocatalyst for Rechargeable Zinc-Air Batteries.

MnO2 has been considered as the most promising bifunctional electrocatalyst toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Despite their highly active ORR performance, the OER catalytic activity of MnO2 species is still far from satisfying. Herein, for the first time, highly active OER catalytic NiFe layered double hydroxides (NiFe LDHs) are combined with MnO2 via a selective electrodeposition method to form a Janus electrode in which the MnO2 and NiFe LDHs are in situ grown on two sides of a porous nickel foam (MnO2-NiFe/Ni). The MnO2-NiFe/Ni electrode exhibits excellent bifunctional catalytic activity and stability for both ORR and OER compared to bare MnO2 on account of the rational design of the Janus bifunctional configuration separating OER and ORR active materials. Moreover, such a Janus MnO2-NiFe air electrode endows the zinc-air battery with better cycling stability and energy efficiency than the bare MnO2 electrode. Our work demonstrates a novel Janus electrode configuration to design high-performance electrocatalysts for energy storage and conversion applications.

NiFe Hydroxide Supported on Hierarchically Porous Nickel Mesh as a High-Performance Bifunctional Electrocatalyst for Water Splitting at Large Current Density.

The preparation of efficient and low-cost bifunctional catalysts with superior stability for water splitting is a topic of significant current interest for hydrogen generation. A facile strategy has been developed to fabricate highly active electrodes with hierarchical porous structures by using a two-step electrodeposition method, in which NiFe layered double hydroxide is grown in situ on a three-dimensional hierarchical Ni mesh (NiFe/Ni/Ni). The as-prepared NiFe/Ni/Ni electrodes demonstrate remarkable structural stability with high surface areas, effective gas transportation, and fast electron transfer. Benefiting from the unique structure, the self-supported NiFe/Ni/Ni electrodes exhibit overpotentials of 190 mV and 300 mV for the oxygen evolution reaction (OER) at current densities of 10 and 500 mA cm-2 , respectively. Furthermore, the self-supported NiFe/Ni/Ni electrodes also exhibit high performance in the hydrogen evolution reaction (HER) and excellent stability at a current density of 500 mA cm-2 for both OER and HER. Remarkably, using NiFe/Ni/Ni as both the cathode and anode for alkaline water electrolysis, a current density of 500 mA cm-2 is attained at a cell voltage of 1.96 V. Additionally, the water electrolyzer demonstrates superior stability even at a large current density (500 mA cm-2 ) when subjected to high temperatures.