Sodium-ion batteries have captured widespread attention for grid-scale energy storage owing to the natural abundance of sodium. The performance of such batteries is limited by available electrode materials, especially for sodium-ion layered oxides, motivating the exploration of high compositional diversity. How the composition determines the structural chemistry is decisive for the electrochemical performance but very challenging to predict, especially for complex compositions. We introduce the "cationic potential" that captures the key interactions of layered materials and makes it possible to predict the stacking structures. This is demonstrated through the rational design and preparation of layered electrode materials with improved performance. As the stacking structure determines the functional properties, this methodology offers a solution toward the design of alkali metal layered oxides.

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Rational design of layered oxide materials for sodium-ion batteries

To meet the application needs of rechargeable Zn-air battery and electrocatalytic overall water splitting (EOWS), developing high-efficiency, cost-effective, and durable trifunctional catalysts for the hydrogen evolution reaction (HER), oxygen evolution, and reduction reaction (OER and ORR) is extremely paramount yet challenging. Herein, the interface engineering concept and nanoscale hollowing design were proposed to fabricate N-doping carbon nanoboxes confined with Co/MoC nanoparticles. Uniform zeolitic imidazolate framework nanocube was employed as the starting material to construct the trifunctional electrocatalyst through the conformal polydopamine-Mo layer coating and the subsequent pyrolysis treatment. The Co@IC/MoC@PC catalyst displayed superior electrochemical ORR performances with a positive half-wave potential of 0.875 V and a high limiting current density of 5.89 mA/cm2. When practically employed as an electrocatalyst in regenerative Zn-air battery, a high specific capacity of 728 mAh/g, a large peak power density of 221 mW/cm2, a high open-circuit voltage of 1.482 V, and a low charge/discharge voltage gap of 0.41 V were obtained. Moreover, its practicability was further exploited by overall water splitting, affording low overpotentials of 277 and 68 mV at 10 mA/cm2 for the OER and HER in 1 M KOH solution, respectively, and a decent operating potential of 1.57 V for EOWS. Ultraviolet photoelectron spectroscopy and density functional theory calculation revealed that the Co/MoC interface synergistically facilitated the charge-transfer, thereby contributing to the enhancements of electrocatalytic ORR/OER/HER processes. More importantly, this catalyst design concept can offer some interesting prospects for the construction of outstanding trifunctional catalysts toward various energy conversion and storage devices.

Co/MoC Nanoparticles Embedded in Carbon Nanoboxes as Robust Trifunctional Electrocatalysts for a Zn-Air Battery and Water Electrocatalysis.

Quantum dot heterostructure with directional charge transfer channels for high sodium storage

Recent progress in sodium/potassium hybrid capacitors

The industrial synthesis of ammonia mainly relies on the Haber-Bosch (H-B) process, which requires high temperature (350–550 °C) and pressure conditions (50–350 atm).[1–3] Up to date, it has become a new research hotspot to produce ammonia through electrochemical nitrogen reduction reaction (eNRR) technology under ambient conditions due to its environmentally friendly characteristics, flexibility, and low cost.[4] The extremely stable NN bond, weak N2 adsorption, and high energy barrier of key intermediates usually require electrocatalysts to improve the eNRR activity and selectivity in ammonia production.[5] However, developing advanced electrocatalysts to improve the eNRR performance with high selectivity is challenging work. Boron-based materials such as boron carbide nanosheets, metal boride, boron nitride, and B-doped carbon have been considered as promising eNRR electrocatalysts.[6–9] Doping engineering and pyrolysis of B-based organic compounds are the two main strategies to generate B active sites.[10,11] Yan groups have demonstrated that boron-rich covalent–organic frameworks could effectively facilitate the N2 accessibility, achieving a high Faradaic efficiency (FE) of 45.43%.[12] This work shows a sign that increasing the B contents and numbers of B active sites could be an effective approach to improve the eNRR activity and selectivity. Recently, applying intermetallic compounds to achieve isolated single-atom sites is an important strategy to improve atomic utilization and break the intrinsic activity limit.[13–17] Extensive efforts mainly focus on the metal sites isolation using intermetallic compounds. Few works have reported the non-metal site isolation in intermetallic compounds and these atomic-scale regulations have become a grand challenge. As a special intermetallic compound, vanadium carbide (VC) has high compositional richness and structural diversity that can make the nonmetal C atoms as well as B and N atoms mutually soluble in the VC crystal matrix.[18] The ordered intermetallic structure of VC can isolate contiguous B atoms into single-B sites with specific electronic structures. Rational regulation in The electrochemical N2 reduction reaction (eNRR) is considered to be an attractive alternative to overcome the short-comings of the Haber-Bosch method, where the electrocatalysts play a vital role in the eNRR efficiency. Herein, isolated single-B sites with electron deficiency in intermetallic carbide are rationally designed to trigger charge density redistribution, achieving excellent selectivity for eNRR. The B-rich VC nanocrystals are in situ synthesized on carbon nanofibers (B-VC/CNFs), and the ordered intermetallic structure of VC can isolate contiguous B atoms into single-B sites with specific electronic structures. In light of density functional theory calculations, the as-designed BCV configuration can regulate the adsorption behavior of N2 and decrease the energy barrier for the proton–electron coupling and transferring process (*NN → *NNH), endowing the distinguished activity and selectivity, as evidenced by excellent Faradaic efficiency of 46.1% and NH3 yield of 0.443 μmol h–1 cm–2. The operando Raman spectra reveals the formation of NH intermediates on the surfaces of B-VC/CNFs, further confirming the calculated eNRR pathway. This intermetallic carbide host strategy for generating electron-deficient single-B sites offers powerful guidelines for designing advanced eNRR electrocatalysts to achieve effective ammonia production.

Isolation of Metalloid Boron Atoms in Intermetallic Carbide Boosts the Catalytic Selectivity for Electrocatalytic N2 Fixation

Various MoC/nitrogen (N)-doped carbon nanosheet hybrid materials (MoC@NCs) have been synthesized, and the effects of various N dopants [graphitic N (G6-N), pyrrolic N (P5-N), pyridinic N (P6-N), and Mo–N] on the electrochemical properties were systematically investigated. With increasing N-doping of MoC@NCs, the electronic conductivity increases. The formation of Mo–N bonds improves the electrochemical stability of MoC@NCs by pinning MoC nanoparticles (NPs) on carbon nanosheets, while the defective species (P5–N and P6–N) are of benefit for ion storage. Thus, MoC@NC-1.0 displays the best cycling stability and rate capability for both sodium-ion batteries (SIBs) (98% capacity retention after 1000 cycles at 1.0 A g−1) and lithium-ion batteries (LIBs) (762 mA h g−1 at 1.0 A g−1). This work not only presents an in-depth understanding of how various N dopants can enhance the electrochemical properties of MoC@NC electrodes but also offers new avenues to develop novel electrode materials for alkaline-ion batteries.

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Correction: Investigating the electroactivity of nitrogen species in MoC nanoparticles/N-doped carbon nanosheets for high-performance Na/Li-ion batteries

Promoting electrochemical performances of vanadium carbide nanodots via N and P co-doped carbon nanosheets wrapping

Na0.9Ni0.45Ti0.55O2 as novel bipolar material for sodium ion batteries

The invention discloses a VC0.75@NPC composite material used for a sodium-ion battery cathode, and preparation and application thereof, belongs to the field of sodium-ion battery cathode material preparation, and particularly relates to the VC0.75@NPC composite material used for the sodium-ion battery cathode, and the preparation and the application thereof. The invention aims to solve the problems that a traditional cathode material used for the sodium-ion battery can not effectively improve the cycling stability of the material on a premise that a good specific capacity is guaranteed. The method comprises the following steps: 1) preparing melamine dispersion liquid; 2) adding complex acid into the dispersion liquid to obtain sediments; 3) cleaning and drying the sediments to obtain a precursor A; 4) preparing gel which contains a vanadium source and a phosphorus source; 5) mixing the precursor A with the gel, and drying to obtain a precursor B; 6) raising the temperature and keepingthe temperature of the precursor B under a condition of argon or nitrogen to obtain black powder; 7) after the black powder is cleaned and dried, obtaining the VC0.75@NPC composite material. The composite material serves as the sodium-ion battery cathode material.

Qing Wu

Papers

Correction: Investigating the electroactivity of nitrogen species in MoC nanoparticles/N-doped carbon nanosheets for high-performance Na/Li-ion batteries

Promoting electrochemical performances of vanadium carbide nanodots via N and P co-doped carbon nanosheets wrapping

Na0.9Ni0.45Ti0.55O2 as novel bipolar material for sodium ion batteries

VC0.75@NPC composite material used for sodium-ion battery cathode as well as preparation and application thereof