Carbon Nitride Pillared Vanadate Via Chemical Pre-Intercalation Towards High-Performance Aqueous Zinc-Ion Batteries

Vanadium based compounds are promising cathode materials for aqueous zinc (Zn)-ion batteries (AZIBs) due to their high specific capacity. However, the narrow interlayer spacing, low intrinsic conductivity and the vanadium dissolution still restrict their further application. Herein, we present an oxygen-deficient vanadate pillared by carbon nitride (C₃N₄) as the cathode for AZIBs through a facile self-engaged hydrothermal strategy. Of note, C₃N₄ nanosheets can act as both the nitrogen source and pre-intercalation species to transform the orthorhombic V₂O₅ into layered NH₄V₄O₁₀ with expanded interlayer spacing. Owing to the pillared structure and abundant oxygen vacancies, both the Zn²⁺ ion (de)intercalation kinetics and the ionic conductivity in the NH₄V₄O₁₀ cathode are promoted. As a result, the NH₄V₄O₁₀ cathode delivers exceptional Zn-ion storage ability with a high specific capacity of about 370 mAh g⁻¹ at 0.5 A g⁻¹, a high-rate capability of 194.7 mAh g⁻¹ at 20 A g⁻¹ and a stable cycling performance of 10 000 cycles.     

Few-Layer Boron Nitride with Engineered Nitrogen Vacancies for Promoting Conversion of Polysulfide as a Cathode Matrix for Lithium–Sulfur Batteries

Lithium–sulfur (Li-S) batteries have become one of the most promising candidates as next-generation batteries, owing to their high specific capacity, low cost, and environmental benignity. Although many strategies have been proposed to restrain the shuttle of lithium polysulfides (LiPSs) through physical trapping and chemical binding, the sluggish kinetics of PS conversion still degrade the capacity, rate, and cycling performance of Li-S batteries. Herein, a novel kind of few-layer BN with engineered nitrogen vacancies (v-BN) has been developed as a cathode matrix for Li-S batteries. The positive vacancies in the BN nanosheets not only promote the immobilization and conversion of LiPSs, but also accelerate the lithium ion diffusion in cathode electrodes. Compared with pristine BN, the v-BN cathodes exhibit higher initial capacities from 775 mA h g⁻¹ to 1262 mA h g⁻¹ at 0.1 C and a high average coulombic efficiency of over 98 % during 150 cycles. Upon increasing the current density to 1 C, the cell still preserves a capacity of 406 mA h g⁻¹ after 500 cycles, exhibiting a capacity decay of only 0.084 % per cycle. The new vacancy-engineered material provides a promising method for achieving excellent performance in Li-S batteries.     

A Deep-Cycle Aqueous Zinc-Ion Battery Containing an Oxygen-Deficient Vanadium Oxide Cathode

Rechargeable aqueous zinc-ion batteries are attractive because of their inherent safety, low cost, and high energy density. However, viable cathode materials (such as vanadium oxides) suffer from strong Coulombic ion–lattice interactions with divalent Zn²⁺, thereby limiting stability when cycled at a high charge/discharge depth with high capacity. A synthetic strategy is reported for an oxygen-deficient vanadium oxide cathode in which facilitated Zn²⁺ reaction kinetic enhance capacity and Zn²⁺ pathways for high reversibility. The benefits for the robust cathode are evident in its performance metrics; the aqueous Zn battery shows an unprecedented stability over 200 cycles with a high specific capacity of approximately 400 mAh g⁻¹, achieving 95 % utilization of its theoretical capacity, and a long cycle life up to 2 000 cycles at a high cathode utilization efficiency of 67 %. This work opens up a new avenue for synthesis of novel cathode materials with an oxygen-deficient structure for use in advanced batteries.     

Boosting the “Solid–Liquid–Solid” Conversion Reaction via Bifunctional Carbonate-Based Electrolyte for Ultra-long-life Potassium–Sulfur Batteries

Potassium–sulfur (K−S) batteries have attracted wide attention owing to their high theoretical energy density and low cost. However, the intractable shuttle effect of K polysulfides results in poor cyclability of K−S batteries, which severely limits their practical application. Herein, a bifunctional concentrated electrolyte (3 mol L⁻¹ potassium bis(trifluoromethanesulfonyl)imide in ethylene carbonate (EC)) with high ionic conductivity and low viscosity is developed to regulate the dissolution behavior of polysulfides and induce uniform K deposition. The organic groups in the cathode electrolyte interphase layer derived from EC can effectively block the polysulfide shuttle and realize a “solid–liquid–solid” reaction mechanism. The KF-riched solid-electrolyte interphase inhibits K dendrite growth during cycling. As a result, the achieved K−S batteries display a high reversible capacity of 654 mAh g⁻¹ at 0.5 A g⁻¹ after 800 cycles and a long lifespan over 2000 cycles at 1 A g⁻¹.     

Triple-function Hydrated Eutectic Electrolyte for Enhanced Aqueous Zinc Batteries

Aqueous rechargeable zinc-ion batteries (ARZBs) are impeded by the mutual problems of unstable cathode, electrolyte parasitic reactions, and dendritic growth of zinc (Zn) anode. Herein, a triple-functional strategy by introducing the tetramethylene sulfone (TMS) to form a hydrated eutectic electrolyte is reported to ameliorate these issues. The activity of H₂O is inhibited by reconstructing hydrogen bonds due to the strong interaction between TMS and H₂O. Meanwhile, the preferentially adsorbed TMS on the Zn surface increases the thickness of double electric layer (EDL) structure, which provides a shielding buffer layer to suppress dendrite growth. Interestingly, TMS modulates the primary solvation shell of Zn²⁺ ultimately to achieve a novel solvent co-intercalation ((Zn-TMS)²⁺) mechanism, and the intercalated TMS works as a “pillar” that provides more zincophilic sites and stabilizes the structure of cathode (NH₄V₄O₁₀, (NVO)). Consequently, the Zn||NVO battery exhibits a remarkably high specific capacity of 515.6 mAh g⁻¹ at a low current density of 0.2 A g⁻¹ for over 40 days. This multi-functional electrolytes and solvent co-intercalation mechanism will significantly propel the practical development of aqueous batteries.     

Constructing 2D Sandwich-like MOF/MXene Heterostructures for Durable and Fast Aqueous Zinc-Ion Batteries

Two-dimensional metal–organic frameworks (2D MOFs) can be used as the cathodes for high-performance zinc-ion battery due to their large one-dimensional channels. However, the conventionally poor electrical conductivity and low structural stability hinder their advances. Herein, we report an alternately stacked MOF/MX heterostructure, exhibiting the 2D sandwich-like structure with abundant active sites, improved electrical conductivity and exceptional structural stability. Ex situ characterizations and theoretical calculations reveal a reversible intercalation mechanism of zinc ions and high electrical conductivity in the 2D heterostructure. Electrochemical tests confirm excellent Zn²⁺ migration kinetics and ideal pseudocapacitive behaviors. As a consequence, Cu-HHTP/MX shows a superior rate performance (260.1 mAh g⁻¹ at 0.1 A g⁻¹ and 173.1 mAh g⁻¹ at 4 A g⁻¹) and long-term cycling stability of 92.5 % capacity retention over 1000 cycles at 4 A g⁻¹.     

Co-Intercalation of Dual Charge Carriers in Metal-Ion-Confining Layered Vanadium Oxide Nanobelts for Aqueous Zinc-Ion Batteries

Vanadium-based oxides with high theoretical specific capacities and open crystal structures are promising cathodes for aqueous zinc-ion batteries (AZIBs). In this work, the confined synthesis can insert metal ions into the interlayer spacing of layered vanadium oxide nanobelts without changing the original morphology. Furthermore, we obtain a series of nanomaterials based on metal-confined nanobelts, and describe the effect of interlayer spacing on the electrochemical performance. The electrochemical properties of the obtained Al_2.65V₆O₁₃ ⋅ 2.07H₂O as cathodes for AZIBs are remarkably improved with a high initial capacity of 571.7 mAh ⋅ g⁻¹ at 1.0 A g⁻¹. Even at a high current density of 5.0 A g⁻¹, the initial capacity can still reach 205.7 mAh g⁻¹, with a high capacity retention of 89.2 % after 2000 cycles. This study demonstrates that nanobelts confined with metal ions can significantly improve energy storage applications, revealing new avenues for enhancing the electrochemical performance of AZIBs.     

Improved Reversible Zinc Storage Achieved in a Constitutionally Crystalline-Stable Mn(VO3)2 Nanobelts Cathode

Rechargeable zinc-ion batteries (ZIBs) are potential for grid-scale applications owing to their safety, low price, and available sources. The development of ZIBs cathode with high specific capacity, wide operating voltage window and stable cyclability is urgently needed in next-generation commercial batteries. Herein, we report a structurally crystalline-stable Mn(VO₃)₂ nanobelts cathode for ZIBs prepared via a facile hydrothermal method. The as-synthesized Mn(VO₃)₂ exhibited high specific capacity of 350 mAh g⁻¹ at 0.1 A g⁻¹, and maintained a capacity retention of 92 % after 10,000 cycles at 2 A g⁻¹. It also showed good rate performance and obtained a reversible capacity of up to 200 mAh g⁻¹ after 600 cycles at 0.2 A g⁻¹ under −20 °C. The electrochemical tests suggest that Mn(VO₃)₂ nanobelts impart fast Zn²⁺ ions migration, and the introduction of manganese atoms help make the structures more indestructible, leading to a good rate performance and prolonged cycle lifespan.     

Nanoscale Surface Modification of Lithium‐Rich Layered‐Oxide Composite Cathodes for Suppressing Voltage Fade

Lithium‐rich layered oxides are promising cathode materials for lithium‐ion batteries and exhibit a high reversible capacity exceeding 250 mAh g⁻¹. However, voltage fade is the major problem that needs to be overcome before they can find practical applications. Here, Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ (LLMO) oxides are subjected to nanoscale LiFePO₄ (LFP) surface modification. The resulting materials combine the advantages of both bulk doping and surface coating as the LLMO crystal structure is stabilized through cationic doping, and the LLMO cathode materials are protected from corrosion induced by organic electrolytes. An LLMO cathode modified with 5 wt % LFP (LLMO–LFP5) demonstrated suppressed voltage fade and a discharge capacity of 282.8 mAh g⁻¹ at 0.1 C with a capacity retention of 98.1 % after 120 cycles. Moreover, the nanoscale LFP layers incorporated into the LLMO surfaces can effectively maintain the lithium‐ion and charge transport channels, and the LLMO–LFP5 cathode demonstrated an excellent rate capacity.     

A ZIF-8 Host for Dendrite-Free Zinc Anodes and N,O Dual-doped Carbon Cathodes for High-Performance Zinc-Ion Hybrid Capacitors

Zn is a promising anode for aqueous energy storage owing to it intrinsic superior properties such as large capacity, abundant reserves, low potential and safety. But, the growth of dendrites during charge and discharge leads to a decrease in reversibility. In addition, further development of zinc-ion hybrid capacitors (ZICs) is seriously challenging because of the lack of an exceptional cathode. Herein, we use ZIF-8 annealed at 500 °C (annealed ZIF-8) as a host material for stable and dendrite-free Zn anodes. Utilization of annealed ZIF-8 results in dendrite-free Zn deposition and stripping as a result of its porous construction, which contains trace Zn. Furthermore, we firstly proposed innovative N,O dual-doped carbon which was designed by the derived ZIF-8 (ZIF-8 derived C) as cathode for high-energy and power-density ZICs. The new ZIC assembled by Zn@annealed ZIF-8 anode and ZIF-8 derived C cathode provides a capacity of 135.5 mAh g⁻¹ and an energy density of 108.4 Wh kg⁻¹ with a power density of 800 W kg⁻¹ at 1.0 A g⁻¹. In addition, it shows outstanding cycling stability of 91% capacity retention after 6000 cycles at 5.0 A g⁻¹. Moreover, the solid-state ZICs can drive LEDs and smart watches. This ZIC holds promise for the practical application of supercapacitors.     

Electrochemically Driven Transformation of Amorphous Carbons to Crystalline Graphite Nanoflakes: A Facile and Mild Graphitization Method

Although, in the carbon family, graphite is the most thermodynamically stable allotrope, conversion of other carbon allotropes, even amorphous carbons, into graphite is extremely hard. We report a simple electrochemical route for the graphitization of amorphous carbons through cathodic polarization in molten CaCl₂ at temperatures of about 1100 K, which generates porous graphite comprising petaloid nanoflakes. This nanostructured graphite allows fast and reversible intercalation/deintercalation of anions, promising a superior cathode material for batteries. In a Pyr₁₄TFSI ionic liquid, it exhibits a specific discharge capacity of 65 and 116 mAh g⁻¹ at a rate of 1800 mA g⁻¹ when charged to 5.0 and 5.25 V vs. Li/Li⁺, respectively. The capacity remains fairly stable during cycling and decreases by only about 8 % when the charge/discharge rate is increased to 10000 mA g⁻¹ during cycling between 2.25 and 5.0 V.     

Boosting Fe Cationic Vacancies with Graphdiyne to Enhance Exceptional Pseudocapacitive Lithium Intercalation

Modulating the electronic structure of electrode materials at atomic level is the key to controlling electrodes with outstanding rate capability. On the basis of modulating the iron cationic vacancies (IV) and electronic structure of materials, we proposed the method of preparing graphdiyne/ferroferric oxide heterostructure (IV-GDY-FO) as anode materials. The goal is to motivate lithium-ion batteries (LIBs) toward ultra-high capacity, superior cyclic stability, and excellent rate performance. The graphdiyne is used as carriers to disperse Fe₃O₄ uniformly without agglomeration and induce high valence of Fe with reducing the energy in the system. The presence of Fe vacancy could regulate the charge distribution around vacancies and adjacent atoms, leading to facilitate electronic transportation, enlarge the lithium-ion diffusion, and decrease Li⁺ diffusion barriers, and thus displaying significant pseudocapacitive process and advantageous lithium-ion storage. The optimized electrode IV-GDY-FO reveals a capacity of 2084.1 mAh g⁻¹ at 0.1 C, superior cycle stability and rate performance with a high specific capacity of 1057.4 mAh g⁻¹ even at 10 C.     

A Metal–Organic Compound as Cathode Material with Superhigh Capacity Achieved by Reversible Cationic and Anionic Redox Chemistry for High‐Energy Sodium‐Ion Batteries

Although sodium‐ion batteries (SIBs) are considered as alternatives to lithium‐ion batteries (LIBs), the electrochemical performances, in particular the energy density, are much lower than LIBs. A metal–organic compound, cuprous 7,7,8,8‐tetracyanoquinodimethane (CuTCNQ), is presented as a new kind of cathode material for SIBs. It consists of both cationic (Cu^II↔Cu^I) and anionic (TCNQ⁰↔TCNQ⁻↔ TCNQ²⁻) reversible redox reactions, delivering a discharge capacity as high as 255 mAh g⁻¹ at a current density of 20 mA g⁻¹. The synergistic effect of both redox‐active metal cations and organic anions brings an electrochemical transfer of multiple electrons. The transformation of cupric ions to cuprous ions occurs at near 3.80 V vs. Na⁺/Na, while the full reduction of TCNQ⁰ to TCNQ⁻ happens at 3.00–3.30 V. The remarkably high voltage is attributed to the strong inductive effect of the four cyano groups.     

Dual Dopamine Derived Polydopamine Coated N-Doped Porous Carbon Spheres as a Sulfur Host for High-Performance Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries are considered to be one of the most promising energy storage systems owing to their high energy density and low cost. However, their wide application is still limited by the rapid capacity fading. Herein, polydopamine (PDA)-coated N-doped hierarchical porous carbon spheres (NPC@PDA) are reported as sulfur hosts for high-performance Li-S batteries. The NPC core with abundant and interconnected pores provides fast electron/ion transport pathways and strong trapping ability towards lithium polysulfide intermediates. The PDA shell could further suppress the loss of lithium polysulfide intermediates through polar–polar interactions. Benefiting from the dual function design, the NPC/S@PDA composite cathode exhibits an initial capacity of 1331 mAh g⁻¹ and remains at 720 mAh g⁻¹ after 200 cycles at 0.5 C. At the pouch cell level with a high sulfur mass loading, the NPC/S@PDA composite cathode still exhibits a high capacity of 1062 mAh g⁻¹ at a current density of 0.4 mA cm⁻².     

Li+/Mg2+ Hybrid‐Ion Batteries with Long Cycle Life and High Rate Capability Employing MoS2 Nano Flowers as the Cathode Material

The demand for large‐scale and safe energy storage is increasing rapidly due to the strong push for smartphones and electric vehicles. As a result, Li⁺/Mg²⁺ hybrid‐ion batteries (LMIBs) combining a dendrite‐free deposition of Mg anode and Li⁺ intercalation cathode have attracted considerable attention. Here, a LMIB with hydrothermal‐prepared MoS₂ nano flowers as cathode material was prepared. The battery showed remarkable electrochemical properties with a large discharge capacity (243 mAh g^?1 at the 0.1 C rate), excellent rate capability (108 mAh g^?1 at the 5 C rate), and long cycle life (87.2 % capacity retention after 2300 cycles). Electrochemical analysis showed that the reactions occurring in the battery cell involved Mg stripping/plating at the anode side and Li⁺ intercalation at the cathode side with a small contribution from Mg²⁺ adsorption. The excellent electrochemical performance and extremely safe cell system show promise for its use in practical applications.     

A Metal–Organic Compound as Cathode Material with Superhigh Capacity Achieved by Reversible Cationic and Anionic Redox Chemistry for High-Energy Sodium-Ion Batteries

Although sodium-ion batteries (SIBs) are considered as alternatives to lithium-ion batteries (LIBs), the electrochemical performances, in particular the energy density, are much lower than LIBs. A metal–organic compound, cuprous 7,7,8,8-tetracyanoquinodimethane (CuTCNQ), is presented as a new kind of cathode material for SIBs. It consists of both cationic (Cu^II↔Cu^I) and anionic (TCNQ⁰↔TCNQ⁻↔ TCNQ²⁻) reversible redox reactions, delivering a discharge capacity as high as 255 mAh g⁻¹ at a current density of 20 mA g⁻¹. The synergistic effect of both redox-active metal cations and organic anions brings an electrochemical transfer of multiple electrons. The transformation of cupric ions to cuprous ions occurs at near 3.80 V vs. Na⁺/Na, while the full reduction of TCNQ⁰ to TCNQ⁻ happens at 3.00–3.30 V. The remarkably high voltage is attributed to the strong inductive effect of the four cyano groups.     

Transformation of Rusty Stainless-Steel Meshes into Stable,Low-Cost,and Binder-Free Cathodes for High-Performance Potassium-Ion Batteries

To recycle rusty stainless-steel meshes (RSSM) and meet the urgent requirement of developing high-performance cathodes for potassium-ion batteries (KIB), we demonstrate a new strategy to fabricate flexible binder-free KIB electrodes via transformation of the corrosion layer of RSSM into compact stack-layers of Prussian blue (PB) nanocubes (PB@SSM). When further coated with reduced graphite oxide (RGO) to enhance electric conductivity and structural stability, the low-cost, stable, and binder-free RGO@PB@SSM cathode exhibits excellent electrochemical performances for KIB, including high capacity (96.8 mAh g⁻¹), high discharge voltage (3.3 V), high rate capability (1000 mA g⁻¹; 42 % capacity retention), and outstanding cycle stability (305 cycles; 75.1 % capacity retention).     

Anion-Dependent Redox Chemistry of p-Type Poly(vinyldimethylphenazine) Cathode Materials

Metal-free organic electrode materials have attracted vast research attention owing to their designable structures and tunable electrochemical properties. Although n-type cathode materials could be used in various metal-ion batteries, p-type ones with high potential can deliver high energy density. Herein, we report a new p-type polymeric cathode material, poly(2-vinyl-5,10-dimethyl-dihydrophenazine) (PVDMP), with a theoretical capacity of 227 mAh g⁻¹. PVDMP featuring two-step redox reaction will be doped by two anions to maintain electroneutrality during oxidation, which resulted in an anion-dependent electrochemical behavior of PVDMP-based cathode. The suitable dopant anion for PVDMP was selected and the doping mechanism was confirmed. Under the optimized condition, PVDMP cathode can deliver a high initial capacity of 220 mAh g⁻¹ at 5 C and even remains 150 mAh g⁻¹ after 3900 cycles. This work not only provides a new kind of p-type organic cathode materials but also deepens the understanding of its anion-dependent redox chemistry.     

Catalytically Active CoSe2 Supported on Nitrogen-Doped Three Dimensional Porous Carbon as a Cathode for Highly Stable Lithium-Sulfur Battery

Lithium-sulfur batteries are promising secondary energy storage devices that are mainly limited by its unsatisfactory cyclability owing to inefficient reversible conversion of sulfur and lithium sulfide on the cathode during the discharge/charging process. In this study, nitrogen-doped three-dimensional porous carbon material loaded with CoSe₂ nanoparticles (CoSe₂-PNC) is developed as a cathode for lithium-sulfur battery. A combination of CoSe₂ and nitrogen-doped porous carbon can efficiently improve the cathode activity and its conductivity, resulting in enhanced redox kinetics of the charge/discharge process. The obtained electrode exhibits a high discharge specific capacity of 1139.6 mAh g⁻¹ at a current density of 0.2 C. After 100 cycles, its capacity remained at 865.7 mAh g⁻¹ thus corresponding to a capacity retention of 75.97 %. In a long-term cycling test, discharge specific capacity of 546.7 mAh g⁻¹ was observed after 300 cycles performed at a current density of 1 C.     

Facile Synthesis of Ultra-Small Few-Layer Nanostructured MoSe2 Embedded on N,P Co-Doped Bio-Carbon for High-Performance Half/Full Sodium-Ion and Potassium-Ion Batteries

Sodium/potassium-ion batteries (SIBs/PIBs) arouse intensive interest on account of the natural abundance of sodium/potassium resources, the competitive cost and appropriate redox potential. Nevertheless, the huge challenge for SIBs/PIBs lies in the scarcity of an anode material with high capacity and stable structure, which are capable of accommodating large-size ions during cycling. Furthermore, using sustainable natural biomass to fabricate electrodes for energy storage applications is a hot topic. Herein, an ultra-small few-layer nanostructured MoSe₂ embedded on N, P co-doped bio-carbon is reported, which is synthesized by using chlorella as the adsorbent and precursor. As a consequence, the MoSe₂/NP-C-2 composite represents exceedingly impressive electrochemical performance for both sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs). It displays a promising reversible capacity (523 mAh g⁻¹ at 100 mA g⁻¹ after 100 cycles) and impressive long-term cycling performance (192 mAh g⁻¹ at 5 A g⁻¹ even after 1000 cycles) in SIBs, which are some of the best properties of MoSe₂-based anode materials for SIBs to date. To further probe the great potential applications, full SIBs pairing the MoSe₂/NP-C-2 composite anode with a Na₃V₂(PO₄)₃ cathode also exhibits a satisfactory capacity of 215 mAh g⁻¹ at 500 mA g⁻¹ after 100 cycles. Moreover, it also delivers a decent reversible capacity of 131 mAh g⁻¹ at 1 A g⁻¹ even after 250 cycles for PIBs.