Mechanical Activation of Graphite for Na-Ion Battery Anodes: Unexpected Reversible Reaction on Solid Electrolyte Interphase via X-Ray Analysis.

Although sodium-ion batteries (SIBs) offer promising low-cost alternatives to lithium-ion batteries (LIBs), several challenges need to be overcome for their widespread adoption. A primary concern is the optimization of carbon anodes. Graphite, vital to the commercial viability of LIBs, has a limited capacity for sodium ions. Numerous alternatives to graphite are explored, particularly focusing on disordered carbons, including hard carbon. However, compared with graphite, most of these materials underperform in LIBs. Furthermore, the reaction mechanism between carbon and sodium ions remains ambiguous owing to the structural diversity of disordered carbon. A straightforward mechanical approach is introduced to enhance the sodium ion storage capacity of graphite, supported by comprehensive analytical techniques. Mechanically activated graphite delivers a notable reversible capacity of 290.5 mAh·g-1 at a current density of 10 mA·g-1. Moreover, it maintains a capacity of 157.7 mAh·g-1 even at a current density of 1 A·g-1, benefiting from the defect-rich structure achieved by mechanical activation. Soft X-ray analysis revealed that this defect-rich carbon employs a sodium-ion storage mechanism distinct from that of hard carbon. This leads to an unexpected reversible reaction on the solid electrolyte surface. These insights pave the way for innovative design approaches for carbon electrodes in SIB anodes.

Engineering Covalent Organic Frameworks Toward Advanced Zinc-Based Batteries.

Zinc-based batteries (ZBBs) have demonstrated considerable potential among secondary batteries, attributing to their advantages including good safety, environmental friendliness, and high energy density. However, ZBBs still suffer from issues such as the formation of zinc dendrites, occurrence of side reactions, retardation of reaction kinetics, and shuttle effects, posing a great challenge for practical applications. As promising porous materials, covalent organic frameworks (COFs) and their derivatives have rigid skeletons, ordered structures, and permanent porosity, which endow them with great potential for application in ZBBs. This review, therefore, provides a systematic overview detailing on COFs structure pertaining to electrochemical performance of ZBBs, following an in depth discussion of the challenges faced by ZBBs, which includes dendrites and side reactions at the anode, as well as dissolution, structural change, slow kinetics, and shuttle effect at the cathode. Then, the structural advantages of COF-correlated materials and their roles in various ZBBs are highlighted. Finally, the challenges of COF-correlated materials in ZBBs are outlined and an outlook on the future development of COF-correlated materials for ZBBs is provided. The review would serve as a valuable reference for further research into the utilization of COF-correlated materials in ZBBs.

Heterostructured grafting of NiFe-layered double hydroxide@TiO2 for boosting photoelectrochemical cathodic protection.

Accelerating the oxidation process at photoanode-electrolyte interfaces can prolong the lifetime of photoexcited electrons and improve the efficiency of photoelectrochemical cathodic protection (PECCP) systems without relying on hole scavengers. However, the systematic design of precisely structured heterostructures for efficient photoanodes remains challenging. Here we meticulously engineered a type-II heterostructure featuring precise spatial organization, wherein NiFe-layered double hydroxide nanosheets (NiFe-LDH NSs) were assembled onto annealed TiO2 nanorod arrays (ATNAs), demonstrating their effectiveness in achieving efficient PECCP. The interfacial electronic coupling and appropriate energy alignment between the NiFe-LDH NSs and ATNAs allowed rapid hole extraction from the ATNAs to the NiFe-LDH NSs. Furthermore, the uniform distribution of the NiFe-LDH NSs on top of ATNAs drastically reduced the overpotential of oxygen evolution reactions (OER) from 370 to 200 mV and Tafel slope from 162 to 56 mV dec-1, leading to significantly improved cathodic protection of 304 stainless steel (SS) under extended illumination and interesting post-illumination protection. In addition, with the increase of testing cycles, the as-prepared NiFe-LDH NSs@ATNAs demonstrated a progressively enhanced cathodic protection potential from 0.15 to 0.13 V vs. RHE over 50 cycles. These findings provide important guidelines for the design of future high-efficiency green metal protection through rational photoanode design.

Data-centric artificial olfactory system based on the eigengraph.

Recent studies of electronic nose system tend to waste significant amount of important data in odor identification. Until now, the sensitivity-oriented data composition has made it difficult to discover meaningful data to apply artificial intelligence in terms of in-depth analysis for odor attributes specifying the identities of gas molecules, ultimately resulting in hindering the advancement of the artificial olfactory technology. Here, we realize a data-centric approach to implement standardized artificial olfactory systems inspired by human olfactory mechanisms by formally defining and utilizing the concept of Eigengraph in electrochemisty. The implicit odor attributes of the eigengraphs were mathematically substantialized as the Fourier transform-based Mel-Frequency Cepstral Coefficient feature vectors. Their effectiveness and applicability in deep learning processes for gas classification have been clearly demonstrated through experiments on complex mixed gases and automobile exhaust gases. We suggest that our findings can be widely applied as source technologies to develop standardized artificial olfactory systems.

Heterometallic Electrocatalysts Derived from High-Nuclearity Metal Clusters for Efficient Overall Water Splitting.

The development of cost-effective electrocatalysts with an optimal surface affinity for intermediates is essential for sustainable hydrogen fuel production, but this remains insufficient. Here we synthesize Ni2P/MoS2-CoMo2S4@C heterometallic electrocatalysts based on the high-nuclearity cluster {Co24(TC4A)6(MoO4)8Cl6}, in which Ni2P nanoparticles were anchored to the surface of the MoS2-CoMo2S4@C nanosheets via strong interfacial interactions. Theoretical calculations revealed that the introduction of Ni2P phases induces significant disturbances in the surface electronic configuration of Ni2P/MoS2-CoMo2S4@C, resulting in more relaxed d-d orbital electron transfers between the metal atoms. Moreover, continuous electron transport was established by the formation of multiple heterojunction interfaces. The optimized Ni2P/MoS2-CoMo2S4@C electrocatalyst exhibited ultralow overpotentials of 198 and 73 mV for oxygen and hydrogen evolution reactions, respectively, in alkaline media, at 10 mA cm-2. The alkali electrolyzer constructed using Ni2P/MoS2-CoMo2S4@C required a cell voltage of only 1.45 V (10 mA cm-2) to drive overall water splitting with excellent long-term stability.

Hierarchical Spatial Confinement Unlocking the Storage Limit of MoS2 for Flexible High-Energy Supercapacitors.

Molybdenum sulfide (MoS2) is a promising electrode material for supercapacitors; however, its limited Mo/S edge sites and intrinsic inert basal plane give rise to sluggish active electronic states, thus constraining its electrochemical performance. Here we propose a hierarchical confinement strategy to develop ethylene molecule (EG)-intercalated Co-doped sulfur-deficient MoS2 (Co-EG/SV-MoS2) for efficient and durable K-ion storage. Theoretical analyses suggest that the intercalation-confined EG and lattice-confined Co can enhance the interfacial K-ion storage capacity while reducing the K-ion diffusion barrier. Experimentally, the intercalated EG molecules with mildly reducing properties induced the creation of sulfur vacancies, expanded the interlayer spacing, regulated the 2H-1T phase transition, and strengthened the structural grafting between layers, thereby facilitating ion diffusion and ensuring structural durability. Moreover, the Co dopants occupying the initial Mo sites initiated charge transfer, thus activating the basal plane. Consequently, the optimized Co-EG/SV-MoS2 electrode exhibited a substantially improved electrochemical performance. Flexible supercapacitors assembled with Co-EG/SV-MoS2 delivered a notable areal energy density of 0.51 mW h cm-2 at 0.84 mW cm-2 with good flexibility. Furthermore, supercapacitor devices were integrated with a strain sensor to create a self-powered system capable of real-time detection of human joint motion.

Covalent Organic Frameworks: Their Composites and Derivatives for Rechargeable Metal-Ion Batteries.

Covalent organic frameworks (COFs) have attracted considerable interest in the field of rechargeable batteries owing to their three-dimensional (3D) varied pore sizes, inerratic porous structures, abundant redox-active sites, and customizable structure-adjustable frameworks. In the context of metal-ion batteries, these materials play a vital role in electrode materials, effectively addressing critical issues such as low ionic conductivity, limited specific capacity, and unstable structural integrity. However, the electrochemical characteristics of the developed COFs still fall short of practical battery requirements due to inherent issues such as low electronic conductivity, the tradeoff between capacity and redox potential, and unfavorable micromorphology. This review provides a comprehensive overview of the recent advancements in the application of COFs, COF-based composites, and their derivatives in rechargeable metal-ion batteries, including lithium-ion, lithium-sulfur, sodium-ion, sodium-sulfur, potassium-ion, zinc-ion, and other multivalent metal-ion batteries. The operational mechanisms of COFs, COF-based composites, and their derivatives in rechargeable batteries are elucidated, along with the strategies implemented to enhance the electrochemical properties and broaden the range of their applications.

Zinc-Bismuth Binary Alloy Enabling High-Performance Aqueous Zinc Ion Batteries.

Reconfiguration of zinc anodes efficiently mitigates dendrite formation and undesirable side reactions, thus favoring the long-term cycling performance of aqueous zinc ion batteries (AZIBs). This study synthesizes a Zn@Bi alloy anode (Zn@Bi) using the fusion method, and find that the anode surfaces synthesized using this method have an extremely high percentage of Zn(002) crystalline surfaces. Experimental results indicate that the addition of bismuth inhibits the hydrogen evolution reaction and corrosion of zinc anodes. The finite-element simulation results indicate that Zn@Bi can effectively achieve a uniform anodic electric field, thereby regulating the homogeneous depositions of zinc ions and reducing the production of Zn dendrite. Theoretical calculations reveal that the incorporation of Bi favors the anode structure stabilization and higher adsorption energy of Zn@Bi corresponds to better Zn deposition kinetics. The Zn@Bi//Zn@Bi symmetric cell demonstrates an extended cycle life of 1000 h. Furthermore, when pairing Zn@Bi with an α-MnO2 cathode to construct a Zn@Bi//MnO2 cell, a specific capacity of 119.3 mAh g-1 is maintained even after 1700 cycles at 1.2 A g-1 . This study sheds light on the development of dendrite-free anodes for advanced AZIBs.

In Situ Construction of the Fe-Cu Hydroxide Interlocking Structure with Solution-Derived Cu/Ag Current Collectors for Flexible Symmetric Supercapacitors.

The current collector serves as a crucial element in supercapacitors, acting as a medium between the electrode material and the substrate. Due to its excellent conductivity, a metal collector is typically favored. Enhancing the binding strength between the collector and the substrate as well as between the collector and the electrode material has emerged as a critical factor for enhancing the capacitance performance. In this study, a Ag film with a grass root-like structure was initially grown on a PI substrate through the surface modification and ion exchange (SMIE) process. This Ag interlocking structure contributes to strong binding between the PI substrate and Ag without compromising the mechanical properties of the Ag film. To further enhance the electrochemical properties at low scan rates, electroless-plated Cu was subsequently deposited on the Ag film to form the Cu/Ag current collector. Moreover, the Cu within the Cu/Ag current collector served as a precursor for the growth of FeOOH-Cu(OH)2 via a two-step in situ method. The resulting FeOOH-Cu(OH)2/Cu/Ag structure as a whole is binder-free. Supercapacitors employing symmetric FeOOH-Cu(OH)2/Cu/Ag structures were assembled, and their energy storage properties were investigated. The solution-based low-temperature process used in this study offers the potential for cost-effective and large-scale applications.

Tensile Strain-Mediated Spinel Ferrites Enable Superior Oxygen Evolution Activity.

Exploring efficient strategies to overcome the performance constraints of oxygen evolution reaction (OER) electrocatalysts is vital for electrocatalytic applications such as H2O splitting, CO2 reduction, N2 reduction, etc. Herein, tunable, wide-range strain engineering of spinel oxides, such as NiFe2O4, is proposed to enhance the OER activity. The lattice strain is regulated by interfacial thermal mismatch during the bonding process between thermally expanding NiFe2O4 nanoparticles and the nonexpanding carbon fiber substrate. The tensile lattice strain causes energy bands to flatten near the Fermi level, lowering eg orbital occupancy, effectively increasing the number of electronic states near the Fermi level, and reducing the pseudoenergy gap. Consequently, the energy barrier of the rate-determining step for strained NiFe2O4 is reduced, achieving a low overpotential of 180 mV at 10 mA/cm2. A total water decomposition voltage range of 1.52-1.56 V at 10 mA/cm2 (without iR correction) was achieved in an asymmetric alkaline electrolytic cell with strained NiFe2O4 nanoparticles, and its robust stability was verified with a voltage retention of approximately 99.4% after 100 h. Furthermore, the current work demonstrates the universality of tuning OER performance with other spinel ferrite systems, including cobalt, manganese, and zinc ferrites.

Emerging Pristine MOF-Based Heterostructured Nanoarchitectures: Advances in Structure Evolution, Controlled Synthesis, and Future Perspectives.

Metal-organic frameworks (MOFs) can be customized through modular assembly to achieve a wide range of potential applications, based on their desired functionality. However, most of the initially reported MOFs are limited to microporous systems and are not sufficiently stable, which restricts their popularization. Heterogeneity is introduced into a simple MOF framework to create MOF-based heterostructures with fascinating properties and interesting functions. Heterogeneity can be introduced into the MOFs via postsynthetic/ligand exchange. Although the ligand exchange has shown potential, it is difficult to precisely control the degree of exchange or position. Among the various synthesis strategies, hierarchical assembly is particularly attractive for constructing MOF-based heterostructures, as it can achieve precise regulation of MOF-based heterostructured nanostructures. The hierarchical assembly significantly expands the compositional diversity of MOF-based heterostructures, which has high elasticity for lattice matching during the epitaxial growth of MOFs. This review focuses on the synthetic evolution mechanism of hierarchical assemblies of MOF-based nanoarchitectures. Subsequently, the precise control of pore structure, pore size, and morphology of MOF-based nanoarchitectures by hierarchical assembly is emphasized. Finally, possible solutions to address the challenges associated with heterogeneous interfaces are presented, and potential opportunities for innovative applications are proposed.

Stabilizing Zn Metal Anode Through Regulation of Zn Ion Transfer and Interfacial Behavior with a Fast Ion Conductor Protective Layer.

Aqueous Zn-ion batteries (AZIBs) attract intensive attention owing to their environmental friendliness, cost-effectiveness, innate safety, and high specific capacity. However, the practical applications of AZIBs are hindered by several adverse phenomena, including corrosion, Zn dendrites, and hydrogen evolution. Herein, a Zn anode decorated with a 3D porous-structured Na3 V2 (PO4)3 (NVP@Zn) is obtained, where the NVP reconstruct the electrolyte/anode interface. The resulting NVP@Zn anode can provide a large quantity of fast and stable channels, facilitating enhanced Zn ion deposition kinetics and regulating the Zn ions transport process through the ion confinement effect. The NASICON-type NVP protective layer promote the desolvation process due to its nanopore structure, thus effectively avoiding side reactions. Theoretical calculations indicate that the NVP@Zn electrode has a higher Zn ion binding energy and a higher migration barrier, which demonstrates that NVP protective layer can enhance Zn ion deposition kinetics and prevent the unfettered 2D diffusion of Zn ions. Therefore, the results show that NVP@Zn/MnO2 full cell can maintain a high specific discharge capacity of 168 mAh g-1 and a high-capacity retention rate of 74.6% after cycling. The extraordinary results obtained with this strategy have confirmed the promising applications of NVP in high-performance AZIBs.

Electronic Structure Engineered Heteroatom Doped All Transition Metal Sulfide Carbon Confined Heterostructure for Extrinsic Pseudocapacitor.

Ultra-high energy density battery-type materials are promising candidates for supercapacitors (SCs); however, slow ion kinetics and significant volume expansion remain major barriers to their practical applications. To address these issues, hierarchical lattice distorted α-/γ-MnS@Cox Sy core-shell heterostructure constrained in the sulphur (S), nitrogen (N) co-doped carbon (C) metal-organic frameworks (MOFs) derived nanosheets (α-/γ-MnS@Cox Sy @N, SC) have been developed. The coordination bonding among Cox Sy , and α-/γ-MnS nanoparticles at the interfaces and the π-π stacking interactions developed across α-/γ-MnS@Cox Sy and N, SC restrict volume expansion during cycling. Furthermore, the porous lattice distorted heteroatom-enriched nanosheets contain a sufficient number of active sites to allow for efficient electron transportation. Density functional theory (DFT) confirms the significant change in electronic states caused by heteroatom doping and the formation of core-shell structures, which provide more accessible species with excellent interlayer and interparticle conductivity, resulting in increased electrical conductivity. . The α-/γ-MnS@Cox Sy @N, SC electrode exhibits an excellent specific capacity of 277 mA hg-1 and cycling stability over 23 600 cycles. A quasi-solid-state flexible extrinsic pseudocapacitor (QFEPs) assembled using layer-by-layer deposited multi-walled carbon nanotube/Ti3 C2 TX nanocomposite negative electrode. QFEPs deliver specific energy of 64.8 Wh kg-1 (1.62 mWh cm-3 ) at a power of 933 W kg-1 and 92% capacitance retention over 5000 cycles.

Electronic and Structural Engineering of Atomically Dispersed Isolated Single-Atom and Alloy Architectures.

Precise configurations of isolated metal atoms in nitrogen-doped carbon materials with 2D single or multilayers and 3D nanoarchitectures are gaining attention owing to their good stability and activity at high current densities. Atomic metal-Nx moieties, which utilize maximum atoms to attain high intrinsic activity and novel electronic architecture of support materials, facilitate strong interaction between the central metal atom and support matrix. However, resource consumption is considerably high due to the inferior atomic utilization of active sites. Therefore, energy-efficient electrochemical processes are needed to develop advanced isolated single-atom architecture, which would provide high atom-utilization and good durability. Herein, the concepts of atomically dispersed metal sites in single-atom and alloy architectures and their electronic features associated with structural evolution are discussed. Opportunities and challenges associated with the use of isolated single-atoms in 2D materials are discussed based on their unique electronic defects, low-valence central metals, mechanical flexibility, and maximum access to metal sites. This insightful revisit into the engineering of single-atom and alloy architectures would provide a profound understanding of electronic modulations and regulation of geometric characteristics, and unravels potential directions for electrochemical energy conversion, charge storage, and sensing processes.

Multiplexed DNA-functionalized graphene sensor with artificial intelligence-based discrimination performance for analyzing chemical vapor compositions.

This study presents a new technology that can detect and discriminate individual chemical vapors to determine the chemical vapor composition of mixed chemical composition in situ based on a multiplexed DNA-functionalized graphene (MDFG) nanoelectrode without the need to condense the original vapor or target dilution. To the best of our knowledge, our artificial intelligence (AI)-operated arrayed electrodes were capable of identifying the compositions of mixed chemical gases with a mixed ratio in the early stage. This innovative technology comprised an optimized combination of nanodeposited arrayed electrodes and artificial intelligence techniques with advanced sensing capabilities that could operate within biological limits, resulting in the verification of mixed vapor chemical components. Highly selective sensors that are tolerant to high humidity levels provide a target for "breath chemovapor fingerprinting" for the early diagnosis of diseases. The feature selection analysis achieved recognition rates of 99% and above under low-humidity conditions and 98% and above under humid conditions for mixed chemical compositions. The 1D convolutional neural network analysis performed better, discriminating the compositional state of chemical vapor under low- and high-humidity conditions almost perfectly. This study provides a basis for the use of a multiplexed DNA-functionalized graphene gas sensor array and artificial intelligence-based discrimination of chemical vapor compositions in breath analysis applications.

Reconfiguring the Electronic Structure of Heteroatom Doped Carbon Supported Bimetallic Oxide@Metal Sulfide Core-Shell Heterostructure via In Situ Nb Incorporation toward Extrinsic Pseudocapacitor.

High-energy-density battery-type materials have sparked considerable interest as supercapacitors electrode; however, their sluggish charge kinetics limits utilization of redox-active sites, resulting in poor electrochemical performance. Here, the unique core-shell architecture of metal organic framework derived N-S codoped carbon@Cox Sy micropetals decorated with Nb-incorporated cobalt molybdate nanosheets (Nb-CMO4 @Cx Sy NC) is demonstrated. Coordination bonding across interfaces and π-π stacking interactions between CMO4 @Cx Sy and N and, S-C can prevent volume expansion during cycling. Density functional theory analysis reveals that the excellent interlayer and the interparticle conductivity imparted by Nb doping in heteroatoms synergistically alter the electronic states and offer more accessible species, leading to increased electrical conductivity with lower band gaps. Consequently, the optimized electrode has a high specific capacity of 276.3 mAh g-1 at 1 A g-1 and retains 98.7% of its capacity after 10 000 charge-discharge cycles. A flexible quasi-solid-state SC with a layer-by-layer deposited reduced graphene oxide /Ti3 C2 TX anode achieves a specific energy of 75.5 Wh kg-1 (volumetric energy of 1.58 mWh cm-3 ) at a specific power of 1.875 kWh kg-1 with 96.2% capacity retention over 10 000 charge-discharge cycles.

Covalently Interlayer-Confined Organic-Inorganic Heterostructures for Aqueous Potassium Ion Supercapacitors.

Artificial assembly of organic-inorganic heterostructures for electrochemical energy storage at the molecular level is promising, but remains a great challenge. Here, a covalently interlayer-confined organic (polyaniline [PANI])-inorganic (MoS2 ) hybrid with a dual charge-storage mechanism is developed for boosting the reaction kinetics of supercapacitors. Systematic characterizations reveal that PANI induces a partial phase transition from the 2H to 1T phases of MoS2 , expands the interlayer spacing of MoS2 , and increases the hydrophilicity. More in-depth insights from the synchrotron radiation-based X-ray technique illustrate that the covalent grafting of PANI to MoS2  induces the formation of MoN bonds and unsaturated Mo sites, leading to increased active sites. Theoretical analysis reveals that the covalent assembly facilitates cross-layer electron transfer and decreases the diffusion barrier of K+ ions, which favors reaction kinetics. The resultant hybrid material exhibits high specific capacitance and good rate capability. This design provides an effective strategy to develop organic-inorganic heterostructures for superior K-ion storage. The K-ion storage mechanism concerning the reversible insertion/extraction upon charge/discharge is revealed through ex situ X-ray photoelectron spectroscopy.

Highly Dispersed Pt Clusters on F-Doped Tin(IV) Oxide Aerogel Matrix: An Ultra-Robust Hybrid Catalyst for Enhanced Hydrogen Evolution.

Dispersing the minuscule mass loading without hampering the high catalytic activity and long-term stability of a noble metal catalyst results in its ultimate efficacy for the electrochemical hydrogen evolution reaction (HER). Despite being the most efficient HER catalyst, the use of Pt is curtailed due to its scarcity and tendency to leach out in the harsh electrochemical reaction environment. In this study, we combined F-doped tin(IV) oxide (F-SnO2) aerogel with Pt catalyst to prevent metallic corrosion and to achieve abundant Pt active sites (approximately 5 nm clusters) with large specific surface area (321 cm2·g-1). With nanoscopic Pt loading inside the SnO2 aerogel matrix, the as-synthesized hybrid F-SnO2@Pt possesses a large specific surface area and high porosity and, thus, exhibits efficient experimental and intrinsic HER activity (a low overpotential of 42 mV at 10 mA·cm-2 in 0.5 M sulfuric acid), a 22-times larger turnover frequency (11.2 H2·s-1) than that of Pt/C at 50 mV, and excellent robustness over 10,000 cyclic voltammetry cycles. The existing metal support interaction and strong intermolecular forces between Pt and F-SnO2 account for the catalytic superiority and persistence against corrosion of F-SnO2@Pt compared to commercially used Pt/C. Density functional theory analysis suggests that hybridization between the Pt and F-SnO2 orbitals enhances intermediate hydrogen atom (H*) adsorption at their interface, which improves the reaction kinetics.

Bio-inspired interface engineering of Ag2O rooted on Au, Ni-modified filter paper for highly robust Zn-Ag2O batteries.

Flexible zinc-silver oxide (Zn-Ag2O) batteries have attracted extensive attention for comfortable wearable electronics owing to their stable output voltage, inherent safety, and environmental benignity. However, they suffer from inferior specific capacity and poor mechanical stability due to the low utilization of Ag2O cathodic material and weak interfacial adhesion of active material/substrate. Inspired by the nature of the tree root system, we develop an interface-engineered cathode, in which Ag2O nanoparticles are rooted on an Au, Ni co-modified filter paper substrate (CFP) through an electroless plating followed by an in situ electrochemical oxidation. The staggered-stacked Ag2O nanoparticles provide abundant electrochemically active sites and convenient ion diffusion paths, and the unique biological tree-root-like structure of the electrode material creates robust interlocking interfaces. A quasi-solid-state Zn-Ag2O battery assembled with a tree-root-like Ag2O/CFP cathode delivers a high areal specific capacity of 1.08 mAh cm-2 and long-term cycling durability with a capacity retention of 77.3% even after 100 cycles. Moreover, the device presents good mechanical stability under various flexural deformations, including bending, folding, and twisting, and exhibits minimal capacity changes after 1000 bending cycles. These findings suggest that the bio-inspired interface-engineered electrode structure is an efficient approach for developing flexible batteries with excellent electrochemical performance and mechanical properties.

Realizing Superior Redox Kinetics of Hollow Bimetallic Sulfide Nanoarchitectures by Defect-Induced Manipulation toward Flexible Solid-State Supercapacitors.

As a typical battery-type material, CuCo2 S4 is a promising candidate for supercapacitors due to the high theoretical specific capacity. However, its practical application is plagued by inherently sluggish ion diffusion kinetics and inferior electrical transport properties. Herein, sulfur vacancies are incorporated in CuCo2 S4 hollow nanoarchitectures (HNs) to accelerate redox reactivity. Experimental analyses and theoretical investigations uncover that the generated sulfur vacancies increase the active electron states, reduce the adsorption barriers of electrolyte ions, and enrich reactive redox species, thus achieving enhanced electrochemical performance. Consequently, the deficient CuCo2 S4 with optimized vacancy concentration presents a high specific capacity of 231 mAh g-1 at 1 A g-1 , a ≈1.78 times increase compared to that of pristine CuCo2 S4 , and exhibits a superior rate capability (73.8% capacity retention at 20 A g-1 ). Furthermore, flexible solid-state asymmetric supercapacitor devices assembled with the deficient CuCo2 S4 HNs and VN nanosheets deliver a high energy density of 61.4 W h kg-1 at 750 W kg-1 . Under different bending states, the devices display exceptional mechanical flexibility with no obvious change in CV curves at 50 mV s-1 . These findings provide insights for regulating electrode reactivity of battery-type materials through intentional nanoarchitectonics and vacancy engineering.