N-doped 3D carbon encapsulating nickel selenide nanoarchitecture with cation defect engineering: An ultrafast and long-life anode for sodium-ion batteries.

Transition metal chalcogenides (TMCs) hold great potential for sodium-ion batteries (SIBs) owing to their multielectron conversion reactions, yet face challenges of poor intrinsic conductivity, sluggish diffusion kinetics, severe phase transitions, and structural collapse during cycling. Herein, a self-templating strategy is proposed for the synthesis of a class of metal cobalt-doped NiSe nanoparticles confined within three-dimensional (3D) N-doped macroporous carbon matrix nanohybrids (Co-NiSe/NMC). The cation defect engineering within the developed Co-NiSe and 3D N-doped carbon plays a crucial role in enhancing intrinsic conductivity, reinforcing structural stability, and reducing the barrier to sodium ion diffusion, which are verified by a series of electrochemical kinetic analyses and density functional theory calculations. Significantly, such cation defect engineering not only reduces overpotential but also accelerates conversion reaction kinetics, ensuring both exceptional high-rate capability and extended durability. Consequently, the optimally engineered Co-NiSe/NMC demonstrates a remarkable rate performance, delivering 390 mAh g-1 at 10 A g-1. Moreover, it exhibits an unprecedented lifespan, maintaining a remarkable capacity of 403 mAh g-1 after 1400 cycles and 318 mAh g-1 after 4000 cycles, even at high rates of 1.0 and 2.0 A g-1, respectively. This work marks a substantial advancement in achieving both high performance and prolonged cycle life in sodium-ion batteries.

Phase engineering of nickel-based sulfides toward robust sodium-ion batteries.

Nickel-based sulfides are considered promising materials for sodium-ion batteries (SIBs) anodes due to their abundant resources and attractive theoretical capacity. However, their application is limited by slow diffusion kinetics and severe volume changes during cycling. Herein, we demonstrate a facile strategy for the synthesis of nitrogen-doped reduced graphene oxide (N-rGO) wrapped Ni3S2 nanocrystals composites (Ni3S2-N-rGO-700 °C) through the cubic NiS2 precursor under high temperature (700 ℃). Benefitting from the variation in crystal phase structure and robust coupling effect between the Ni3S2 nanocrystals and N-rGO matrix, the Ni3S2-N-rGO-700 °C exhibits enhanced conductivity, fast ion diffusion kinetics and outstanding structural stability. As a result, the Ni3S2-N-rGO-700 °C delivers excellent rate capability (345.17 mAh g-1 at a high current density of 5 A g-1) and long-term cyclic stability over 400 cycles at 2 A g-1 with a high reversible capacity of 377 mAh g-1 when evaluated as anodes for SIBs. This study open a promising avenue to realize advanced metal sulfide materials with desirable electrochemical activity and stability for energy storage applications.

Visible-Light-Induced Oxidative C-H Functionalization of Unreactive Cycloalkanes, Alcohols, and Ethers with Alkynylphosphine Oxides into Benzo[b]phosphole Oxides under Photocatalyst-, Metal-, and Base-Free Conditions.

We developed the radical cyclization/addition of alkynylphosphine oxides with easily available cycloalkanes, alcohols, and ethers using a visible-light and environmentally friendly synthetic strategy in the absence of photocatalyst at room temperature. This mild and metal- and base-free reaction provided a structurally varied set of significant benzo[b]phosphole oxides through sequential C-H functionalization in an atom-economical manner.