Although rechargeable aqueous zinc-ion batteries have attracted extensive interest due to their environmental friendliness and low cost, they still lack suitable cathodes with high rate capabilities, which are hampered by the intense charge repulsion of bivalent Zn . Here, a novel intercalation pseudocapacitance behavior and ultrafast kinetics of Zn into the unique tunnels of VO (B) nanofibers in aqueous electrolyte are demonstrated via in situ X-ray diffraction and various electrochemical measurements. Because VO (B) nanofibers possess unique tunnel transport pathways with big sizes (0.82 and 0.5 nm along the b- and c-axes) and little structural change on Zn intercalation, the limitation from solid-state diffusion in the vanadium dioxide electrode is eliminated. Thus, VO (B) nanofibers exhibit a high reversible capacity of 357 mAh g , excellent rate capability (171 mAh g at 300 C), and high energy and power densities as applied for zinc-ion storage.

Metallic 1T MoS2 is highly desirable for catalyzing electrochemical hydrogen production from water owing to its high electrical conductivity. However, stable 1T MoS2 is difficult to be produced in large‐scale by either common chemical or physical approaches. Here, ultrastable in‐plane 1T–2H MoS2 heterostructures are achieved via a simple one‐pot annealing treatment of 2H MoS2 bulk under a mixture gas of Ar and phosphorous vapor, where phosphorus cannot only occupy the interspace of MoS2 bulk, resulting in the expansion of MoS2, but also embed into the lattice of MoS2, inducing the partial phase transition from 2H to 1T phases of MoS2. Benefiting from its significantly improved electrical conductivity, highly exposed active sites, and hydrophily property, in‐plane 1T–2H MoS2 heterostructures exhibit largely improved electrocatalytic properties for hydrogen evolution reaction (HER) in alkaline electrolytes.

Unfortunately, the volume changes of such metals and metal oxides during sodiation/desodiation processes are more severe than those during lithiation/delithiation processes, resulting in a large loss of electric contact and eventually rapid capacity decay. [7d,10a] To circumvent above volume change issues of metals and metal oxides during sodiation/desodiation processes, various metal (oxide)-carbon nanocomposites such as Sb/carbon fibers, [7d,11] Sb/ porous carbons, [12] and Sb 2 O 3 /Sb@graphene architectures [13] have been recently designed and fabricated via various chemical approaches and demonstrated improved gravimetric capacities, cycle performances, and high-rate capabilities. Although it has been a great achievement, these metal (oxide)/carbon nanocomposites commonly show very low volumetric capacities (100-350 mAh cm −3 ), [14] largely hampering the development, and practical applications of sodium ion batteries.Different from other metals, metallic Sb with gray allotrope (R3m space group) has rarely been considered from the viewpoint of 2D layered system is actually a graphite-like layered material, in which Sb layers consist of fused, ruffled, six-membered rings; [15] the nearest and next-nearest Sb atoms form an irregular octahedral complex, with three atoms in each double layer slightly closer than the three atoms in the next. Such close packing generates a high density of 6.7 g cm −3 for gray Sb, [15b] and the weak bonding between the layers enable to be a potential candidate for the top-down fabrication of Sb nanosheets. Given that metallic Sb nanosheets can be played like graphene, it would be anticipated to obtain a new anode material with superior electrochemical performances for sodium storage.In this work, we propose an efficient strategy to fabricate free-standing metallic Sb nanosheets via liquid-phase exfoliation of gray Sb powder in an isopropyle alcohol (IPA) solution with a constant concentration of sodium hydroxide. Remarkably, the resultant metallic Sb nanosheets have ultrathin (≈4 nm), foldable features and large aspect ratios. Such unique features render metallic Sb nanosheets behaving like graphene and enable to construct uniform and compacted films with other nanosheets. As a proof of the concept, several hybrid films composed of metallic Sb nanosheets and graphene with tunable densities are achieved, in which the notorious volume change of metallic Sb can be efficiently alleviated with the aid of Metallic antimony (Sb) with gray allotrope has rarely been considered from the viewpoint of two-dimension layered system is actually a graphite-like material, in which Sb layers consist of fused, ruffled, and six-membered rings. Given that metallic Sb nanosheets can be played like graphene, it would be anticipated to obtain a new anode material with superior electrochemical performances for sodium storage. In this work, we propose an efficient strategy to fabricate free-standing metallic Sb nanosheets via liquid-phase exfoliation of gray Sb powder in an ios-propyle alcohol (IPA) so...

Owing to the intense charge repulsion of multivalent ions and intrinsic slugggish kenetics, vast and fast storage of zinc ions into electrode materials has remained unattainable. Here, an efficient strategy to unlock the electrochemical activity of rocksalt vanadium oxynitride is developed via the substitution of low‐valent oxygen for high‐valent nitrogen, forming disordered rocksalt with abundant vacancies/defects due to the charge‐compensating function. Unexpectedly, the disordered rocksalt not only provides plentiful active sites for zinc ions but is also beneficial for the rapid diffusion of zinc ions, owing to the large presence of vacancies/defects in the matrix. Hence, a very high reversible capacity (603 mAh g−1, 0.2C) and high rate capability (124 mAh g−1at 600C) are achieved for zinc storage. This should open a new and efficient avenue for the design of electrode materials with both high energy and power densities for aqueous zinc‐ion batteries.

Lithium (Li) metal has been considered as one of the most prospective anodes for Li-based batteries owing to its high theoretical gravimetric capacity (3860 mAh g–1) and low potential (−3.04 V vs standard hydrogen electrode (SHE)). Unfortunately, there commonly exist uncontrollable dendrites in lithium anodes during the repeated plating–stripping processes, causing short cycle life and even short circuiting of lithium batteries. Here, single zinc atoms immobilized on MXene (Ti3C2Cl x ) layers (Zn-MXene) were produced to efficiently induce Li nucleation and growth. At the initial plating stage, lithium tended to nucleate homogeneously on the surface of Zn-MXene layers due to the large presence of Zn atoms and then grow vertically along the nucleated sites owing to a strong lightning rod effect at the edges, affording bowl-like lithium without lithium dendrites. Thus, a low overpotential of 11.3 ± 0.1 mV, long cyclic life (1200 h), and deep stripping–plating levels up to 40 mAh cm–2 are obtained by using Zn-MXene films as lithium anodes.

No abstract

Single atom catalysts possess attractive electrocatalytic activities for various chemical reactions owing to their favorable geometric and electronic structures compared to the bulk counterparts. Herein, we demonstrate an efficient approach to producing single atom copper immobilized MXene for electrocatalytic CO 2 reduction to methanol via selective etching of hybrid A layers (Al and Cu) in quaternary MAX phases (Ti 3 (Al 1−x Cu x )C 2 ) due to the different saturated vapor pressures of Al-and Cu-containing products. After selective etching of Al in the hybrid A layers, Cu atoms are wellpreserved and simultaneously immobilized onto the resultant MXene with dominant surface functional group (Cl x ) on the outmost Ti layers (denoted as Ti 3 C 2 Cl x ) via Cu−O bonds. Consequently, the as-prepared single atom Cu catalyst exhibits a high Faradaic efficiency value of 59.1% to produce CH 3 OH and shows good electrocatalytic stability. On the basis of synchrotron-based X-ray absorption spectroscopy analysis and density functional theory calculations, the single atom Cu with unsaturated electronic structure (Cu δ+ , 0 < δ < 2) delivers a low energy barrier for the rate-determining step (conversion of HCOOH* to absorbed CHO* intermediate), which is responsible for the efficient electrocatalytic CO 2 reduction to CH 3 OH.

pure Li phase. Such solid solution surface layers can act as buffer layers for the following Li plating, effectively eliminating nucleation barriers. This understanding opens up the opportunity to guide the uniform deposition of metallic lithium via preplanting nucleation seeds, which is becoming an efficient strategy to regulate lithium plating with controllable positions and morphologies. [19][20][21][22][23] To circumvent the issue of lithium dendrites, another efficient strategy is to explore 3D nanomaterials with high electric conductivities, good chemical stabilities, and large surface areas, [14,20,[24][25][26][27][28][29][30][31][32][33] which can significantly reduce effective current densities of electrodes and uniformize the electric field distribution to avoid the charge accumulation. Based on this principle, some 3D structures, such as copper/nickel sponges, [24][25][26] carbon materials, [20,[28][29][30] and stacked reduced graphene oxide films, [32,33] have been employed as hosts for metallic lithium and exhibited enhanced electrochemical stabilities and low overpotentials. More importantly, such 3D hosts with high porosities can also efficiently solve the infinite volume change of Li during stripping/plating processes. [34,35] Therefore, 3D lithiophilic hosts associated with homogeneous nucleation seeds are highly desirable in rechargeable metallic lithium anodes.It is known that zeolitic imidazolate frameworks (ZIFs) are one prototypical metal-organic frameworks (MOFs) with sodalite zeolite-type structure, [36][37][38][39] composed of tetrahedrally coordinated transition metal ions (Cu 2+ , Co 2+ , Zn 2+ , etc.) connected by imidazolate linkers. After a simple thermal treatment, ZIFs can be transformed to unique microporous carbons with wellconfined metal clusters. [40][41][42] Here, we demonstrate that carbonized MOF with zinc species (ZIF-8, 2-methylimidazolate as organic ligand) is an ideal lithiophilic host for metallic lithium, which enables facile molten Li infusion to the matrix, forming a uniform lithium-carbonized MOFs (Li-cMOFs) hybrid. In this hybrid, numerous Zn clusters are homogeneously dispersed in the matrix, behaving like preplanted nucleation seeds to guide Li deposition owing to their well thermodynamic match with lithium that can overcome the nucleation barrier; at the same time, the 3D conductive porous structure dramatically homogenizes the distributions of electric field and Li ion flux, preventing the formation of lithium dendrites. Moreover, the infinite volume change of lithium caused by plating and stripping can be also well addressed by the porous cMOFs. These Although metallic lithium is a promising anode material due to its high theoretical capacity, the uncontrollable growth of lithium dendrites and infinite volume change hamper its practical applications. Here, the lithiophilic property of carbonized metal-organic frameworks (cMOFs) is harnessed with zinc species to achieve a uniform lithium-cMOFs (Li-cMOFs) hybrid via a molten lithium infusion approach. In the res...