Structural Distortion in the Wadsley-Roth Niobium Molybdenum Oxide Phase Triggering Extraordinarily Stable Battery Performance

In-depth insight into the effects of oxygen vacancies on the excellent Li+-storage performances of Cu2Nb34O87-x/N-doped carbon composite

Wadsley-Roth phase niobates demonstrate significant Li+-storage advantages. Even though their Nb5+ can fully transform into Nb4+ during lithiation process, however, only partial Nb4+ can further convert to Nb3+, leading to much lower practical capacities than the theoretical values according to the two-electron transfer per Nb5+. The specific mechanism to improve their conversion ratio of Nb4+ to Nb3+ during lithiation process has rarely been reported so far. Herein, the ultrafine oxygen-deficient Cu2Nb34O87-x nanoparticles are closely connected by the N-doped carbon-based 3D conductive framework to form a cloud-like Cu2Nb34O87-x/N-doped carbon composite (denoted as VU-CNO-NC) with nanoaggregate structure and porous structure. Based on density functional theory (DFT) calculations and ex situ X-ray photoelectron spectrometer (XPS), the oxygen vacancies in VU-CNO-NC can catalyze the conversion of Nb4+ to Nb3+ during lithiation process, which significantly enhance the conversion ratio of Nb4+ to Nb3+ to generate much higher capacity. This effect of oxygen vacancies has rarely been reported so far. Moreover, the oxygen vacancies, ultrafine primary nanoparticles, 3D conductive framework, porous structure, and nanoaggregate structure synergistically endow VU-CNO-NC with fast Li+-storage kinetics and highly stable structure. Consequently, VU-CNO-NC not only shows high capacity (287 mAh g-1 after 500 cycles at 1 C and 181 mAh g-1 after 1000 cycles at 10 C) and excellent rate performance as anode material of lithium-ion batteries, but also endows hybrid lithium-ion capacitor with high energy density (126 Wh kg-1 at 175 W kg-1) and remarkable capacity retention (87.3 % after 9000 cycles at 2 A g-1), demonstrating great application prospect.

S-S Bond Strategy at Sulfide Heterointerface: Reversing Charge Transfer and Constructing Hydrogen Spillover for Boosted Hydrogen Evolution

Developing efficient electrocatalyst in sulfides for hydrogen evolution reaction (HER) still poses challenges due to the lack of understanding the role of sulfide heterointerface. Here, we report a sulfide heterostructure RuSx/NbS2, which is composed of 3R-type NbS2 loaded by amorphous RuSx nanoparticles with S-S bonds formed at the interface. As HER electrocatalyst, the RuSx/NbS2 shows remarkable low overpotential of 38 mV to drive a current density of 10 mA cm-2 in acid, and also low Tafel slope of 51.05 mV dec-1. The intrinsic activity of RuSx/NbS2 is much higher than that of Ru/NbS2 reference as well as the commercial Pt/C. Both experiments and theoretical calculations unveil a reversed charge transfer at the interface from NbS2 to RuSx that driven by the formation of S-S bonds, resulting in electron-rich Ru configuration for strong hydrogen adsorption. Meanwhile, electronic redistribution induced by the sulfide heterostructure facilitates hydrogen spillover (HSo) effect in this system, leading to accelerated hydrogen desorption at the basal plane of NbS2. This study provides an effective S-S bond strategy in sulfide heterostructure to synergistically modulate the charge transfer and adsorption thermodynamics, which is very valuable for the development of efficient electrocatalysts in practical applications.

"Zero-Strain" NiNb2O6 Fibers for All-Climate Lithium Storage

Niobates are promising all-climate Li+-storage anode material due to their fast charge transport, large specific capacities, and resistance to electrolyte reaction. However, their moderate unit-cell-volume expansion (generally 5%-10%) during Li+ storage causes unsatisfactory long-term cyclability. Here, "zero-strain" NiNb2O6 fibers are explored as a new anode material with comprehensively good electrochemical properties. During Li+ storage, the expansion of electrochemical inactive NiO6 octahedra almost fully offsets the shrinkage of active NbO6 octahedra through reversible O movement. Such superior volume-accommodation capability of the NiO6 layers guarantees the "zero-strain" behavior of NiNb2O6 in a broad temperature range (0.53%//0.51%//0.74% at 25// - 10//60 °C), leading to the excellent cyclability of the NiNb2O6 fibers (92.8%//99.2% // 91.1% capacity retention after 1000//2000//1000 cycles at 10C and 25// - 10//60 °C). This NiNb2O6 material further exhibits a large reversible capacity (300//184//318 mAh g-1 at 0.1C and 25// - 10//60 °C) and outstanding rate performance (10 to 0.5C capacity percentage of 64.3%//50.0%//65.4% at 25// - 10//60 °C). Therefore, the NiNb2O6 fibers are especially suitable for large-capacity, fast-charging, long-life, and all-climate lithium-ion batteries.

Electropolymerized Bipolar Poly(2,3-diaminophenazine) Cathode for High-Performance Aqueous Al-Ion Batteries with An Extended Temperature Range of -20 to 45 °C

Achieving reversible insertion/extraction in most cathodes for aqueous aluminum ion batteries (AAIBs) is a significant challenge due to the high charge density of Al3+ and strong electrostatic interactions. Organic materials facilitate the hosting of multivalent carriers and rapid ions diffusion through the rearrangement of chemical bonds. Here, a bipolar conjugated poly(2,3-diaminophenazine) (PDAP) on carbon substrates prepared via a straightforward electropolymerization method is introduced as cathode for AAIBs. The integration of n-type and p-type active units endow PDAP with an increased number of sites for ions interaction. The long-range conjugated skeleton enhances electron delocalization and collaborates with carbon to ensure high conductivity. Moreover, the strong intermolecular interactions including π-π interaction and hydrogen bonding significantly enhance its stability. Consequently, the Al//PDAP battery exhibits a large capacity of 338 mAh g-1 with long lifespan and high-rate capability. It consistently demonstrates exceptional electrochemical performances even under extreme conditions with capacities of 155 and 348 mAh g-1 at -20 and 45 °C, respectively. In/ex situ spectroscopy comprehensively elucidates its cation/anion (Al3+/H3O+ and ClO4 -) storage with 3-electron transfer in dual electroactive centers (C═N and -NH-). This study presents a promising strategy for constructing high-performance organic cathode for AAIBs over a wide temperature range.

Rational Design of Multinary Metal Chalcogenide Bi0.4 Sb1.6 Te3 Nanocrystals for Efficient Potassium Storage

Multinary metal chalcogenides hold considerable promise for high-energy potassium storage due to their numerous redox reactions. However, challenges arise from issues such as volume expansion and sluggish kinetics. Here, a design featuring a layered ternary Bi0.4 Sb1.6 Te3 anchored on graphene layers as a composite anode, where Bi atoms act as a lattice softening agent on Sb, is presented. Benefiting from the lattice arrangement in Bi0.4 Sb1.6 Te3 and structure, Bi0.4 Sb1.6 Te3 /graphene exhibits a mitigated expansion of 28% during the potassiation/depotassiation process and demonstrates facile K+ ion transfer kinetics, enabling long-term durability of 500 cycles at various high rates. Operando synchrotron diffraction patterns and spectroscopies including in situ Raman, ex situ adsorption, and X-ray photoelectron reveal multiple conversion and alloying/dealloying reactions for potassium storage at the atomic level. In addition, both theoretical calculations and electrochemical examinations elucidate the K+ migration pathways and indicate a reduction in energy barriers within Bi0.4 Sb1.6 Te3 /graphene, thereby suggesting enhanced diffusion kinetics for K+ . These findings provide insight in the design of durable high-energy multinary tellurides for potassium storage.