In-Situ Construction of Functional Multi-Dimensional MXene-based Composites Directly from MAX Phases through Gas-Solid Reactions.

The weak bonding of A atoms with MX layers in MAX phases not only enables the selective etching of A layers for MXene preparation but brings about the chance to construct A derivatives/MXene composites via in-situ conversion. Here, a facile and general gas-solid reaction systems are elegantly devised to construct multi-dimensional MXene based composites including AlF3 nanorods/MXene, AlF3 nanocrystals/MXene, amorphous AlF3/MXene, A filled carbon nanotubes/MXene, layered metal chalcogenides/MXene, MOF/MXene, and so on. The intrinsic effect mechanism of interlayer confinement towards crystal growth, catalytic behavior, van der Waals-heterostructure construction and coordination reaction are rationally put forward. The tight interface combination and synergistic effect from distinct components make them promising active materials for electrochemical applications. More particularly, the AlF3 nanorods/Nb2C MXene demonstrate bi-directional catalytic activity toward the conversion between Li2S and lithium polysulfides, which alleviates the shuttle effect of lithium-sulfur batteries.

Chemomechanically Stable Small Single-crystal Mo-doped LiNi0.6 Co0.2 Mn0.2 O2 Cathodes for Practical 4.5†V-class Pouch-type Li-ion Batteries.

High voltage can cost-effectively boost energy density of Ni-rich cathodes based Li-ion batteries (LIBs), but compromises their mechanical, electrochemical and thermal-driven stability. Herein, a collaborative strategy (i.e., small single-crystal design and hetero-atom doping) is devised to construct a chemomechanically reliable small single-crystal Mo-doped LiNi0.6 Co0.2 Mn0.2 O2 (SS-MN6) operating stably under high voltage (≥4.5 V vs. Li/Li+ ). The substantially reduced particle size combined with Mo6+ doping absorbs accumulated localized stress to eradicate cracks formation, subdues the surface side reactions and lattice oxygen missing meanwhile, and improves thermal tolerance at highly delithiated state. Consequently, the SS-MN6 based pouch cells are endowed with striking deep cycling stability and wide-temperature-tolerance capability. The contribution here provides a promising way to construct advanced cathodes with superb chemomechanical stability for next-generation LIBs.

Single-Crystal Nano-Subunits Assembled Accordion-Shape WNb2 O8 Framework with High Ionic/Electronic Conductivities towards Li-Ion Capacitors.

Recently, Li-ion capacitors (LICs) have drawn tremendous attention due to their high energy/power density along with long cycle life. Nevertheless, the slow kinetics and stability of the involved anodes as bottleneck barriers always result in the modest properties of devices. The exploration of advanced anodes with both high ionic and electronic conductivities as well as structural stability thus becomes more significant for practical applications of LICs. Herein, a single-crystal nano-subunits assembled hierarchical accordion-shape WNb2 O8 micro-/nano framework is first designed via a one-step scalable strategy with the multi-layered Nb2 CTx as a precursor. The underlying solid solution Li-storage mechanism of the WNb2 O8 just with a volumetric expansion of ≈1.5% is proposed with in situ analysis. Benefiting from congenitally crystallographic merits, single-crystalline characteristic, and open accordion-like architecture, the resultant WNb2 O8 as a robust anode platform is endowed with fast electron/ion transport capability and multi-electron redox contributions from W/Nb, and accordingly, delivers a reversible capacity of ≈135.5 mAh g-1 at a high rate of 2.0 A g-1 . The WNb2 O8 assembled LICs exhibit an energy density of ≈33.0 Wh kg-1 at 9 kW kg-1 , coupled with remarkable electrochemical stability. The work provides meaningful insights into the rational design and construction of advanced bimetallic niobium oxides for next-generation LICs.

Recent Progress of Carbon-Based Anode Materials for Potassium Ion Batteries.

With the increasing demand for clean energy, rechargeable batteries with K+ as carriers have attracted wide attention due to their advantages of expandability and low cost. High-performance anode materials are the key to the development of potassium ion batteries (PIBs), improving their competitiveness and feasibility. Carbon materials have become promising anodes for PIBs due to their abundant resources, low cost, non-toxicity and electrochemical diversity. This article reviews the research progress of carbon based anode materials in recent years. Firstly, the unique characteristics of carbon as a competitive anode for advanced PIBs are discussed, which provides guidance for optimal design and exploration. Then, various carbon materials as the anodes towards PIBs are summarized in detail, and the involved problems and corresponding solutions are analyzed. Finally, the future development and perspective of advanced carbons for next-generation PIBs are proposed.

Organic-Inorganic Hybridization Engineering of Polyperylenediimide Cathodes for Efficient Potassium Storage.

Polyperylenediimide (PDI) is always subject to its modest conductivities, limited reversible active sites and inferior stability for potassium storage. To address these issues, herein, we firstly propose an organic-inorganic hybrid (PDI@Fe-Sn@N-Ti3 C2 Tx ), where Fe/Sn single atoms are bound to the N-doped MXenes (N-Ti3 C2 Tx ) via the unsaturated Fe/Sn-N3 bonds, and functionalized with PDI via d-π hybridization, forming a high conjugated δ skeleton. The resulted hybrid cathode endowed with enhanced electronic/ionic conductivities, lowered dissociation barriers of multiple redox centers and a stable cathode electrolyte interphase layer displays a 14-electron involved high-rate capacities and long cycle life. Moreover, it shows competitive performance in full cells even under different folding states and low operating temperatures.

Unveiling Intrinsic Potassium Storage Behaviors of Hierarchical Nano Bi@N-Doped Carbon Nanocages Framework via In Situ Characterizations.

Metallic bismuth has drawn attention as a promising alloying anode for advanced potassium ion batteries (PIBs). However, serious volume expansion/electrode pulverization and sluggish kinetics always lead to its inferior cycling and rate properties for practical applications. Therefore, advanced Bi-based anodes via structural/compositional optimization and sur-/interface design are needed. Herein, we develop a bottom-up avenue to fabricate nanoscale Bi encapsulated in a 3D N-doped carbon nanocages (Bi@N-CNCs) framework with a void space by using a novel Bi-based metal-organic framework as the precursor. With elaborate regulation in annealing temperatures, the optimized Bi@N-CNCs electrode exhibits large reversible capacities and long-duration cyclic stability at high rates when evaluated as competitive anodes for PIBs. Insights into the intrinsic K+ -storage processes of the Bi@N-CNCs anode are put forward from comprehensive in situ characterizations.

Construction of Hierarchical Nanotubes Assembled from Ultrathin V3 S4 @C Nanosheets towards Alkali-Ion Batteries with Ion-Dependent Electrochemical Mechanisms.

Ultrathin core-shell V3 S4 @C nanosheets assembled into hierarchical nanotubes (V3 S4 @C NS-HNTs) are synthesized by a self-template strategy and evaluated as general anodes for alkali-ion batteries. Structural/physicochemical characterizations and DFT calculations bring insights into the intrinsic relationship between crystal structures and electrochemical mechanisms of the V3 S4 @C NS-HNTs electrode. The V3 S4 @C NS-HNTs are endowed with strong structural rigidness owing to the layered VS2 subunits and interlayer occupied V atoms, and efficient alkali-ion adsorption/diffusion thanks to the electroactive V3 S4 -C interfaces. The resulting V3 S4 @C NS-HNTs anode exhibit distinct alkali-ion-dependent charge storage mechanisms and exceptional long-durability cyclic performance in storage of K+ , benefiting from synergistic contributions of pseudocapacitive and reversible intercalation/de-intercalation behaviors superior to those of the conversion-reaction-based Li+ -/Na+ -storage counterparts.

Scalable Synthesis of One-Dimensional Mesoporous ZnMnO3 Nanorods with Ultra-Stable and High Rate Capability for Efficient Lithium Storage.

The cost-efficient ZnMnO3 has attracted increasing attention as a prospective anode candidate for advanced lithium-ion batteries (LIBs) owing to its resourceful abundance, large lithium storage capacity and low operating voltage. However, its practical application is still seriously limited by the modest cycling and rate performances. Herein, a facile design to scalable synthesize unique one-dimensional (1D) mesoporous ZnMnO3 nanorods (ZMO-NRs) composed of nanoscale particles (≈11 nm) is reported. The 1D mesoporous structure and nanoscale building blocks of the ZMO-NRs effectively promote the transport of ions/electrons, accommodate severe volume changes, and expose more active sites for lithium storage. Benefiting from these appealing structural merits, the obtained ZMO-NRs anode exhibits excellent rate behavior (≈454 mAh g-1 at 2 A g-1 ) and ultra-long term cyclic performance (≈949.7 mAh g-1 even over 500 cycles at 0.5 A g-1 ) for efficient lithium storage. Additionally, the LiNi0.8 Co0.1 Mn0.1 O2 //ZMO-NRs full cell presents a practical energy density (≈192.2 Wh kg-1 ) and impressive cyclability with approximately 91 % capacity retention over 110 cycles. This highlights that the ZMO-NRs product is a highly promising high-rate and stable electrode candidate towards advanced LIBs in electronic devices and sustainable energy storage applications.

Spatially Self-Confined Formation of Ultrafine NiCoO2 Nanoparticles@Ultralong Amorphous N-Doped Carbon Nanofibers as an Anode towards Efficient Capacitive Li+ Storage.

The exploration of anode materials with a high degree of electrochemical utilization for Li-ion batteries (LIBs) still remains a huge challenge despite pioneering breakthroughs. Rational engineering of electrode structures/components by facile strategies would offer infinite possibilities for the development of LIBs. In this study, one-dimensional ultralong nanohybrids of ultrafine NiCoO2 nanoparticles dispersed in situ in and/or on the surface of amorphous N-doped carbon nanofibers (NCO@ANCNFs) were fabricated by a bottom-up electrospinning protocol. By virtue of synergistic structural/component features, the obtained ultralong NCO@ANCNFs with low NCO loading (≈33.6 wt %) show highly efficient Li+ storage performance with high reversible capacity, high rate capability, and long cycle life. The unusual reversible crystalline transformation during cycling was analyzed. Quantitative analysis revealed that the pseudocapacitive contribution mainly accounts for the superior lithium storage of the NCO@ANCNFs. Besides, the ability of the hybrid anode to deliver competitive Li-storage properties even without conductive carbon greatly enhances its commercial applicability. An NCO@ANCNFs//LiNi0.8 Co0.15 Al0.05 O2 full battery was assembled and exhibited striking electrochemical properties. This contribution offers a scalable methodology to fabricate highly efficient hybrid anodes for advanced next-generation LIBs.

Hierarchical sulfur-impregnated hydrogenated TiO2 mesoporous spheres comprising anatase nanosheets with highly exposed (001) facets for advanced Li-S batteries.

In this contribution, we purposefully designed hierarchical hydrogenated TiO2 spheres (HTSs) constructed from ultrathin anatase nanosheets with highly exposed (001) facets, and further utilized them as an efficient encapsulated host of sulfur species for advanced Li-S batteries (LSBs). Strikingly, the as-fabricated hybrid S/HTSs cathode exhibited high Coulombic efficiency (>94%), exceptional long cycling performance (capacity decay of ∼0.399% per cycle at 0.5 C), and large reversible discharge capacity (∼579 mAh g(-1) at 2.0 C) at high C rates, benefiting from better electronic conductivity, smaller charge transfer resistance and strong chemical bonding between [Formula: see text] and the reduced (001) facets of HTSs, according to experimental measurements and systematical theoretical calculations. More significantly, our in-depth insights into the mechanism involved in the hybrid S/HTSs could efficiently guide future design, optimization and synthesis of other metal oxide-based matrixes with specific exposed crystal facets for next-generation advanced LSBs.

Metal-organic-framework-derived two-dimensional ultrathin mesoporous hetero-ZnFe2O4/ZnO nanosheets with enhanced lithium storage properties for Li-ion batteries.

Mesoporous hetero-structures have drawn tremendous attention due to their unprecedented inherent advantages in advanced Li-ion batteries (LIBs). In this study, we developed a facile metal-organic-framework-engaged synthetic methodology for large-scale fabrication of two-dimensional (2D) mesoporous hetero-ZnFe2O4/ZnO nanosheets (ZFOZ NSs) with homogeneously dispersed hetero-nanodomains of spinel ZnFe2O4 and ZnO. When evaluated as a promising anode for LIB applications, the resultant 2D ultrathin mesoporous hetero-ZFOZ NSs exhibited extraordinary electrochemical Li storage performance with long-cycle behavior and large reversible capacities for next-generation LIB applications, thanks to the attractive synergetic contributions from ultrathin mesoporous architecture and electroactive bi-component hetero-interfaces at the nanoscale. Even more encouragingly, the electrode concept we developed here can be easily generalized to rational design and synthesis of other mesoporous hetero-hybrids with remarkable lithium storage capacities for LIBs.

Hierarchical Porous ZnMn2 O4 Hollow Nanotubes with Enhanced Lithium Storage toward Lithium-Ion Batteries.

We have purposefully developed a smart template-engaged methodology to efficiently fabricate well-defined ternary spinel ZnMn2 O4 hollow nanotubes (NTs). The procedure involves coating carbon nanotubes (CNTs) with ZnMn2 O4 nanosheets (NSs), followed by heating at high temperature in air to oxidize the CNT template. Physicochemical characterization demonstrated that the formed ZnMn2 O4 NTs with a diameter of approximately 100 nm were composed of assembled NSs and/or nanoparticles (NPs) as building blocks and possessed numerous nanopores of several nanometers in the sidewall of the NTs. In favor of the intrinsic structural advantages, the resulting ZnMn2 O4 NTs exhibited superior electrochemical lithium-storage performance with a large capacity, good rate behavior, and excellent cyclability when evaluated as promising anodes for lithium-ion batteries (LIBs). The remarkable electrochemical performance was rationally ascribed to the appealing one-dimensional (1D) porous hollow tubular architecture with nanoscale subunits and mesopores in the sidewalls, which decreased the diffusion length for the Li(+) ions, improved the kinetic process, and enhanced the structural integrity with sufficient void space to tolerate the volume variation during Li(+) -ion insertion/extraction. These results highlight the promising application of 1D ZnMn2 O4 NTs as anodes for high-performance LIBs.

Green Template-Free Synthesis of Hierarchical Shuttle-Shaped Mesoporous ZnFe2 O4 Microrods with Enhanced Lithium Storage for Advanced Li-Ion Batteries.

Invited for the cover of this issue is Changzhou Yuan and co-workers at the Anhui University of Technology. The image depicts hierarchical shuttle-shaped mesoporous ZnFe2 O4 micro-rods, as a low-cost yet high-performance anode, for advanced next-generation Li-ion batteries. Read the full text of the article at 10.1002/chem.201501876.

Green Template-Free Synthesis of Hierarchical Shuttle-Shaped Mesoporous ZnFe2 O4 Microrods with Enhanced Lithium Storage for Advanced Li-Ion Batteries.

In the work, a facile and green two-step synthetic strategy was purposefully developed to efficiently fabricate hierarchical shuttle-shaped mesoporous ZnFe2 O4 microrods (MRs) with a high tap density of ∼0.85 g cm(3) , which were assembled by 1D nanofiber (NF) subunits, and further utilized as a long-life anode for advanced Li-ion batteries. The significant role of the mixed solvent of glycerin and water in the formation of such hierarchical mesoporous MRs was systematically investigated. After 488 cycles at a large current rate of 1000 mA g(-1) , the resulting ZnFe2 O4 MRs with high loading of ∼1.4 mg per electrode still preserved a reversible capacity as large as ∼542 mAh g(-1) . Furthermore, an initial charge capacity of ∼1150 mAh g(-1) is delivered by the ZnFe2 O4 anode at 100 mA g(-1) , resulting in a high Coulombic efficiency of ∼76 % for the first cycle. The superior Li-storage properties of the as-obtained ZnFe2 O4 were rationally associated with its mesoprous micro-/nanostructures and 1D nanoscaled building blocks, which accelerated the electron transportation, facilitated Li(+) transfer rate, buffered the large volume variations during repeated discharge/charge processes, and provided rich electrode-electrolyte sur-/interfaces for efficient lithium storage, particularly at high rates.

Scalable room-temperature synthesis of mesoporous nanocrystalline ZnMn2O4 with enhanced lithium storage properties for lithium-ion batteries.

In this work, we put forward a facile yet efficient room-temperature synthetic methodology for the smart fabrication of mesoporous nanocrystalline ZnMn2O4 in macro-quality from the birnessite-type MnO2 phase. A plausible reduction/ion exchange/re-crystallization mechanism is tentatively proposed herein for the scalable synthesis of the spinel phase ZnMn2O4. When utilized as a high-performance anode for advanced Li-ion battery (LIB) application, the as-synthesized nanocrystalline ZnMn2O4 delivered an excellent discharge capacity of approximately 1288 mAh g(-1) on the first cycle at a current density of 400 mA g(-1), and exhibited an outstanding cycling durability, rate capability, and coulombic efficiency, benefiting from its mesoporous and nanoscale structure, which strongly highlighted its great potential in next-generation LIBs. Furthermore, the strategy developed here is very simple and of great importance for large-scale industrial production.

Heterostructured core-shell ZnMn2O4 nanosheets@carbon nanotubes' coaxial nanocables: a competitive anode towards high-performance Li-ion batteries.

In this study, we rationally designed a rapid, low-temperature yet general synthetic methodology for the first time, involving in situ growth of two-dimensional (2D) birnessite-type MnO2 nanosheets (NSs) upon each carbon nanotube (CNT), and we designed the subsequent phase transformation into untrathin mesoporous ZnMn2O4 NSs with a thickness of ∼2-3 nm at room temperature to efficiently fabricate heterostructured core-shell ZnMn2O4 NSs@CNT coaxial nanocables with well-dispersed and tunable ZnMn2O4 loading. The underlying insights into the low-temperature formation mechanism of the unique core-shell hybrid nanoarchitectures were tentatively proposed here. When utilized as a high-performance anode for advanced LIBs, the resultant core-shell ZnMn2O4@CNTs' coaxial nanocables (∼84.5 wt.% loading) exhibited large specific discharge capacity (∼1033 mAh g(-1)), good rate capability (∼528 mAh g(-1)) and excellent cycling stability (average capacity degradation of only ∼5.2% per cycle) at a high current rate of 1224 mA g(-1), originating from the distinct core-shell synergetic effect of fast electronic delivery and from the large electrode/electrolyte contacting surfaces/interfaces provided by three-dimensional entangling coaxial CNT-based nanonetwork topology.

Self-sacrifice template construction of a conductive Cu3(HHTP)2 nanowhisker arrays@copper foam toward robust lithium storage.

Nanowhisker-like Cu3(HHTP)2 composed of neat arrays grown on a copper foam is rationally designed and prepared using Cu(OH)2 nanowire arrays as a self-sacrifice template. Benefiting from the good conductivity of Cu3(HHTP)2 and an ordered array structure, the optimized Cu3(HHTP)2@CF-3 electrode exhibits high area capacity, good rate performance and cyclic stability.

High-entropy doping promising ultrahigh-Ni Co-free single-crystalline cathode toward commercializable high-energy lithium-ion batteries.

The development of advanced layered Ni-rich cathodes is essential for high-energy lithium-ion batteries (LIBs). However, the prevalent Ni-rich cathodes are still plagued by inherent issues of chemomechanical and thermal instabilities and limited cycle life. For this, here, we introduce an efficient approach combining single-crystalline (SC) design with in situ high-entropy (HE) doping to engineer an ultrahigh-Ni cobalt-free layered cathode of LiNi0.88Mn0.03Mg0.02Fe0.02Ti0.02Mo0.02Nb0.01O2 (denoted as HE-SC-N88). Thanks to the SC- and HE-doping merits, HE-SC-N88 is featured with a grain-boundary-free and stabilized structure with minimal lattice strain, preventing mechanical degradation, reducing surface parasitic reactions, and mitigating oxygen loss. Accordingly, our HE-SC-N88 cathode demonstrates exceptional electrochemical properties particularly with prolonged cycling stability under strenuous conditions in both half and full cells, and the delayed O loss-induced phase transitions upon heating. More meaningfully, our design of HE doping in redefining the ultrahigh-Ni Co-free SC cathodes will make a tremendous progress toward industrial application of next-generation LIBs.

Ultra-Sensitive Simultaneous Detection of Dopamine and Acetaminophen over Hollow Porous AuAg Alloy Nanospheres.

Hollow porous AuAg nanospheres (AuAg HPNSs) were obtained through a simple solvothermal synthesis, complemented by a dealloying strategy. The hollow interior, open pore voids, and integral interconnected skeleton shell in AuAg HPNSs are beneficial for providing sufficient electrolyte diffusion and contacts, abundant active sites, and efficient electron transport. This specific structure and the favorable alloy synergism contribute to the superior electrocatalytic activity toward dopamine (DA) and acetaminophen (AC). AuAg HPNSs show high sensitivity, good selectivity, excellent sensing durability, and outstanding repeatability for amperometric assays of AC and DA. In particular, the AuAg-based sensors achieve effective ultrasensitive simultaneous analyses of AC and DA, exhibiting the characteristics of the wide linear range and low detection limit. With their prominent electrocatalytic activity and simple preparation methods, AuAg HPNSs present broad application prospects for constructing a highly responsive electrochemical sensing system.

Multifunctional Vanadium Nitride-Modified Separator for High-Performance Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSBs) are recognized as among the best potential alternative battery systems to lithium-ion batteries and have been widely investigated. However, the shuttle effect has severely restricted the advancement in their practical applications. Here, we prepare vanadium nitride (VN) nanoparticles grown in situ on a nitrogen-doped carbon skeleton (denoted as VN@NC) derived from the MAX phase and use it as separator modification materials for LSBs to suppress the shuttle effect and optimize electrochemical performance. Thanks to the outstanding catalytic performance of VN and the superior electrical conductivity of carbon skeleton derived from MAX, the synergistic effect between the two accelerates the kinetics of both lithium polysulfides (LiPSs) to Li2S and the reverse reaction, effectively suppresses the shuttle effect, and increases cathode sulfur availability, significantly enhancing the electrochemical performance of LSBs. LSBs constructed with VN@NC-modified separators achieve outstanding rate performance and cycle stability. With a capacity of 560 mAh g-1 at 4 C, it exhibits enhanced structural and chemical stability. At 1 C, the device has an incipient capacity of 1052.4 mAh g-1, and the degradation rate averaged only 0.085% over 400cycles. Meanwhile, the LSBs also show larger capacities and good cycling stability at a low electrolyte/sulfur ratio and high surface-loaded sulfur conditions. Thus, a facile and efficient way of preparing modified materials for separators is provided to realize high-performance LSBs.