Synchronous Regulation of D-Band Centers in Zn Substrates and Weakening Pauli Repulsion of Zn Ions Using the Ascorbic Acid Additive for Reversible Zinc Anodes.

The advanced aqueous zinc-ion batteries (AZIBs) are still challenging due to the harmful reactions including hydrogen evolution and corrosion. Here, a natural small molecule acid vitamin C (Vc) as an aqueous electrolyte additive has been selectively identified. The small molecule Vc can adjust the d band center of Zn substrate which fixes the active H+ so that the hydrogen evolution reaction (HER) is restrained. Simultaneously, it could also fine-tune the solvation structure of Zn ions due to the enhanced electrostatics and reduced Pauli repulsion verified by energy decomposition analysis (EDA). Hence, the cell retains an ultra-long cycle performance of over 1300 cycles and a superior Coulombic efficiency (CE) of 99.5 %. The prepared full cells display increased rate capability, cycle lifetime, and self-discharge suppression. Our results shed light on the mechanistic principle of electrolyte additives on the performance improvement of ZIBs, which is anticipated to render a new round of studies.

Self-Zincophilic Dual Protection Host of 3D ZnO/Zn⊂CF to Enhance Zn Anode Cyclability.

Zn dendrite growth and side reactions restrict the practical use of Zn anode. Herein, the design of a novel 3D hierarchical structure is demonstrated with self-zincophilic dual-protection constructed by ZnO and Zn nanoparticles immobilized on carbon fibers (ZnO/Zn⊂CF) as a versatile host on the Zn surface. The unique 3D frameworks with abundant zinc nucleation storage sites can alleviate the structural stress during the plating/stripping process and overpower Zn dendrite growth by moderating Zn2+ flux. Moreover, given the dual protection design, it can reduce the contact area between active zinc and electrolyte, inhibiting hydrogen evolution reactions. Importantly, density functional theory calculations and experimental results confirm that the introduced O atoms in ZnO/Zn⊂CF enhance the interaction between Zn2+ and the host and reduce Zn nucleation overpotential. As expected, the ZnO/Zn⊂CF-Zn electrode exhibits stable Zn plating/stripping with low polarization for 4200 h at 0.2 mA cm-2 and 0.2 mAh cm-2 . Furthermore, the symmetrical cell displays a significantly long cycling life of over 1800 h, even at 30 mA cm-2 . The fabricated full cells also show impressive cycling performance when coupled with V2 O3 cathodes.

Multifunctional Atomic Molybdenum on Graphene with Distinctive Coordination to Solve Li and S Electrochemistry.

The improvement of lithium-sulfur batteries is still impeded by notorious shuttling effect and sluggish kinetics on the S cathode, and rampant Li dendrite formation on the Li anode makes it worse. Herein, a type of single-atom dispersed Mo on nitrogen-doped graphene (Mo/NG) with a distinctive Mo-N2 O2 -C coordination structure first serving as a multifunctional material is designed by a structure-oriented strategy to solve Li and S electrochemistry. Mo/NG with superior intrinsic properties endowed by the unique coordination configuration adsorbs soluble polysulfides and promotes bidirectional conversion of LiPSs at the cathode side. Meanwhile, the suitable binding strength of Mo/NG with lithium ions endows it with an attractive lithiophilic feature. Specifically, Mo/NG is able to work as the adaptor to redistribute lithium ions on the interface of separator and homogenize the lithium ion flux. Due to the suitable binding ability with Li+ , it does not interfere with the diffusion of lithium ions across and provides tunnels exclusive to lithium ions to generate fast and homogeneous flux. Ascribed to such unique multifunctionality, Li-S batteries assembled with Mo/NG exhibit excellent electrochemical performance including long cycling stability over 1000 cycles and high areal capacities under high sulfur mass loading.

Molybdenum Oxynitride Atomic Nanoclusters Bonded in Nanosheets of N-Doped Carbon Hierarchical Microspheres for Efficient Sodium Storage.

Transition metal nitrides have attracted considerable attention as great potential anode materials due to their excellent metallic conductivity and high theoretical specific capacity. However, their cycling performance is impeded by their instability caused by the reaction mechanism. Herein, we report the engineering and synthesis of a novel hybrid architecture composed of MoO2.0N0.5 atomic nanoclusters bonded in nanosheets of N-doped carbon hierarchical hollow microspheres (MoO2.0N0.5/NC) as an anode material for sodium-ion batteries. The facile self-templating strategy for the synthesis of MoO2.0N0.5/NC involves chemical polymerization and subsequent one-step calcination treatments. The design is beneficial to improve the electrochemical kinetics, buffer the volume variation of electrodes during cycling, and provide more interfacial active sites for sodium uptake. Due to these unique structural and compositional merits, these MoO2.0N0.5/NC exhibits excellent sodium storage performance in terms of superior rate capability and stable long cycle life. The work shows a feasible and effective way to design novel host candidates and solve the long-term cycling stability issues for sodium-ion batteries.

Integrating Bi@C Nanospheres in Porous Hard Carbon Frameworks for Ultrafast Sodium Storage.

Sodium-ion batteries (SIBs) have emerged as an alternative technology because of their merits in abundance and cost. Realizing their real applications, however, remains a formidable challenge. One is that among the limitations of anode materials, the alloy-type candidates tolerate fast capacity fading during cycling. Here, a 3D framework superstructure assembled with carbon nanobelt arrays decorated with a metallic bismuth (Bi) nanospheres coated carbon layer by thermolysis of Bi-based metal-organic framework nanorods is synthesized as an anode material for SIBs. Due to the unique structural superiority, the anode design promotes excellent sodium-storage performance in terms of high capacity, excellent cycling stability, and ultrahigh rate capability up to 80 A g-1 with a capacity of 308.8 mAh g-1 . The unprecedented sodium-storage ability is not only attributed to the unique hybrid architecture, but also to the production of a homogeneous and thin solid electrolyte interface layer and the formation of uniform porous nanostructures during cycling in the ether-based electrolyte. Importantly, deeper understanding of the underlying cause of the performance improvement is illuminated, which is vital to provide the theoretical basis for application of SIBs.

Rationally Designed Three-Layered TiO2 @amorphous MoS3 @Carbon Hierarchical Microspheres for Efficient Potassium Storage.

Amorphous MoS3 has been an attractive electrode material for sodium-ion batteries and lithium-sulfur batteries. However, the potassium storage capability of amorphous MoS3 remains unreported. Herein, the construction of hybrid hierarchical microspheres composed of amorphous MoS3 nanosheets dual-confined with TiO2 core, and nitrogen-doped carbon shell layer (denoted as TiO2 @A-MoS3 @NC) via a self-templating method, combined with a low-temperature sulfurization process as a new anode material for potassium-ion batteries (PIBs), is reported. Benefitting from the unique structural merits including unique 1D chain structure, disordered arrangement of atoms and a large number of defects of amorphous MoS3 , more active heterointerfacial sites, effectively mitigated volume change, good electrical contact, and easy K+ ion migration, the TiO2 @A-MoS3 @NC microspheres exhibit excellent potassium-storage performance with high specific capacity, superior rate capability, and cycling stability.

WSe2 Flakelets on N-Doped Graphene for Accelerating Polysulfide Redox and Regulating Li Plating.

The practical application of lithium-sulfur batteries is still limited by the lithium polysulfides (LiPSs) shuttling effect on the S cathode and uncontrollable Li-dendrite growth on the Li anode. Herein, elaborately designed WSe2 flakelets immobilized on N-doped graphene (WSe2 /NG) with abundant active sites are employed to be a dual-functional host for satisfying both the S cathode and Li anode synchronously. On the S cathode, the WSe2 /NG with a strong interaction towards LiPSs can act as a redox accelerator to promote the bidirectional conversion of LiPSs. On the Li anode, the WSe2 /NG with excellent lithiophilic features can regulate the uniform Li plating/stripping to mitigate the growth of Li dendrite. Taking advantage of these merits, the assembled Li-S full batteries exhibit remarkable rate performance and stable cycling stability even at a higher sulfur loading of 10.5 mg cm-2 with a negative to positive electrode capacity (N/P) ratio of 1.4 : 1.

In Situ Electrochemically Activated Vanadium Oxide Cathode for Advanced Aqueous Zn-Ion Batteries.

The search for large-capacity and high-energy-density cathode materials for aqueous Zn-ion batteries is still challenging. Here, an in situ electrochemical activation strategy to boost the electrochemical activity of a carbon-confined vanadium trioxide (V2O3@C) microsphere cathode is demonstrated. Tunnel-structured V2O3 undergoes a complete phase transition to a layered, amorphous, and oxygen-deficient Zn0.4V2O5-m·nH2O on the first charge, thus allowing subsequent (de)intercalation of zinc cations on the basis of the latter structure, which can be regulated by the amount of H2O in the electrolyte. The electrode thus delivers excellent stability with a significantly high capacity of 602 mAh g-1 over 150 cycles upon being subjected to a low-current-rate cycling, as well as a high-energy density of 439.6 Wh kg-1 and extended life up to 10000 cycles with a 90.3% capacity retention. This strategy will be exceptionally desirable to achieve ultrafast Zn-ion storage with high capacity and energy density.

Dual-Functional MgO Nanocrystals Satisfying Both Polysulfides and Li Regulation toward Advanced Lithium-Sulfur Full Batteries.

Lithium-sulfur battery (LSB) is regarded as a preferential option for next-generation energy-storage system, but the lithium polysulfides (LiPSs) shuttling effect and the uncontrollable growth of dendritic Li in the anode impede its commercial viability. To address both of the issues simultaneously, a well-designed hybrid of MgO ultrafine nanocrystals dispersed on graphene-supported carbon nanosheets (MCG) is developed via a facile self-template strategy as dual-functional host for both sulfur and lithium. Relying on the coordination of strong LiPS-capturing capability, the shuttling effect is inhibited. Furthermore, the lithiophilic configuration with high specific surface area induce homogenous Li deposition, thus preventing the formation of disordered lithium dendrite. Integrating all these advantages, a full cell based on S@MCG cathode and Li@MCG@Cu anode exhibits a stable capacity at 0.5 C for 150 cycles with a low capacity fading rate. Furthermore, the full cell achieves a high capacity retention of 85.5% at a high S areal loading of 3.82 mg cm-2 under the condition of a low electrolyte/sulfur ratio (E/S) of 6.5 µL mg-1 and negative/positive capacity ratio (N/P) of 3. This strategy satisfying both cathode and anode host provides a viable approach to realize high-energy-density and dendrite-free LSBs.

Advances and Perspectives of Cathode Storage Chemistry in Aqueous Zinc-Ion Batteries.

Rechargeable aqueous zinc-ion batteries (AZIBs) have captured a surge of interest in recent years as a promising alternative for scalable energy storage applications owing to the intrinsic safety, affordability, environmental benignity, and impressive electrochemical performance. Despite the facilitated development of this technology by many investigations, however, its smooth implementation is still plagued by inadequate energy density and undesirable life span, which calls for an efficient and controllable cathode storage chemistry. Here, this review focuses on the key bottlenecks by offering a comprehensive summary of representative cathode materials and comparatively analyzing their structural features and electrochemical properties. Then, we critically present several feasible electrode design strategies to guide future research activities from a fundamental perspective for high-energy-density and durable cathode materials mainly in terms of interlayer regulation, defect engineering, multiple redox reactions, activated two-electron reactions, and electrochemical activation and conversion. Finally, we outline the remaining challenges and future perspectives of developing high-performance AZIBs.

A High-Rate and Ultrastable Aqueous Zinc-Ion Battery with a Novel MgV2 O6 ·1.7H2 O Nanobelt Cathode.

High-safety and low-cost aqueous Zn-ion batteries have triggered an astounding investigation surge in the last 5 years and are becoming competitive alternatives for grid-scale energy storage. However, the implementation of this promising technology is still plagued by the lack of effective and affordable cathode materials that can enable high energy densities and an exceptional cycling stability. Herein, a novel vanadium-based oxide cathode based on MgV2 O6 ·1.7H2 O nanobelts, which delivers a high capacity (425.7 mAh g-1 at 0.2 A g-1 ), a robust rate capability (182.1 mAh g-1 at 10 A g-1 ), and an ultrastable cycle without any visible deterioration, as well as an adequate energy density (331.6 Wh kg-1 ), is developed. Such excellent electrochemical Zn-ion storage performance is believed to result from the fast ion-diffusion kinetics boosted by a stable layered structure and an ultrahigh intercalation pseudocapacitance reaction, which are also benefited by a typical H+ /Zn2+ co-insertion mechanism, accompanied by an atypical Zn2+ intercalation chemistry with a partial but irreversible Mg2+ -Zn2+ ion-exchange reaction during the initial discharge. These results provide key and enlightening insights into the design of high-performance vanadium oxide cathode materials.

Atomic Tungsten on Graphene with Unique Coordination Enabling Kinetically Boosted Lithium-Sulfur Batteries.

Use of catalytic materials is regarded as the most desirable strategy to cope with sluggish kinetics of lithium polysulfides (LiPSs) transformation and severe shuttle effect in lithium-sulfur batteries (LSBs). Single-atom catalysts (SACs) with 100 % atom-utilization are advantagous in serving as anchoring and electrocatalytic centers for LiPSs. Herein, a novel kind of tungsten (W) SAC immobilized on nitrogen-doped graphene (W/NG) with a unique W-O2 N2 -C coordination configuration and a high W loading of 8.6 wt % is proposed by a self-template and self-reduction strategy. The local coordination environment of W atom endows the W/NG with elevated LiPSs adsorption ability and catalytic activity. LSBs equipped with W/NG modified separator manifest greatly improved electrochemical performances with high cycling stability over 1000 cycles and ultrahigh rate capability. It indicates high areal capacity of 6.24 mAh cm-2 with robust cycling life at a high sulfur mass loading of 8.3 mg cm-2 .

Bimetal CoNi Active Sites on Mesoporous Carbon Nanosheets to Kinetically Boost Lithium-Sulfur Batteries.

In order to solve the problem that soluble polysulfide intermediates diffuse between cathode and anode during charging and discharging, which leads to rapid attenuation of battery cycle life, the separator modification materials come into people's sight. Herein, a mesoporous carbon-supported cobalt-nickel bimetal composite (CoNi@MPC) is synthesized and directly coated on the original separator to serve as a secondary collector for lithium-sulfur batteries. CoNi@MPC exhibits multiple Co-Ni active sites, able to catalyze the reactions of soluble polysulfides, specifically accelerating the generation and decomposition of insoluble Li2 S in lithiation and delithiation process testified by the electrochemical results and density functional theory calculation. Relying on the bifunctionality of CoNi@MPC composite, the shuttle effect of lithium polysulfides can be effectively alleviated. Moreover, porous carbon as the conductive scaffold favors the improvement of electronic conductivity. Benefiting from the above advantages, the cell with CoNi@MPC separator indicates significantly enhanced electrochemical performances with excellent cycling life over 500 cycles and superior rate capabilities.

Ni12P5 nanoparticles bound on graphene sheets for advanced lithium-sulfur batteries.

Lithium-sulfur batteries (LSBs) have been regarded as potential energy storage devices by virtue of their high theoretical capacity, natural abundance of materials and low cost. However, the notorious shuttle effect and sluggish reaction kinetics are still significant challenges for further development. Herein, Ni12P5 nanoparticles are devised and grown on a reduced graphene oxide (Ni12P5@rGO) framework via a self-template and recrystallization-self-assembly strategy, as the modifier for separators in LSBs for the first time. The support of rGO for Ni12P5 nanoparticles could solve the self-aggregation problem. Ni12P5 nanoparticles not only effectively adsorb polysulfides by polar interaction, but also supply active sites to ameliorate the kinetics of the redox reaction of sulfur. Consequently, when a sulfur-containing commercial acetylene black material (70 wt% sulfur content) is used as the cathode composite without complicated fabrication or surface modification, an LSB with Ni12P5@rGO modified separator shows excellent cycling stability and a capacity degradation of 0.074% per cycle at the current density of 1 C for 500 cycles. When the areal mass of sulfur further increases to 3.5 mg cm-2, the capacity degradation is only 0.071% per cycle at 150 cycles. This study could accelerate the application of phosphides in LSBs.