Conductive carbon nanofiber interpenetrated graphene architecture for ultra-stable sodium ion battery

Fast-Charging Anode Materials for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) have undergone rapid development as a complementary technology to lithium-ion batteries due to abundant sodium resources. However, the extended charging time and low energy density pose a significant challenge to the widespread use of SIBs in electric vehicles. To overcome this hurdle, there is considerable focus on developing fast-charging anode materials with rapid Na⁺ diffusion and superior reaction kinetics. Here, the key factors that limit the fast charging of anode materials are examined, which provides a comprehensive overview of the major advances and fast-charging characteristics across various anode materials. Specifically, it systematically dissects considerations to enhance the rate performance of anode materials, encompassing aspects such as porous engineering, electrolyte desolvation strategies, electrode/electrolyte interphase, electronic conductivity/ion diffusivity, and pseudocapacitive ion storage. Finally, the direction and prospects for developing fast-charging anode materials of SIBs are also proposed, aiming to provide a valuable reference for the further advancement of high-power SIBs.

Massively Reconstructing Hydrogen Bonding Network and Coordination Structure Enabled by a Natural Multifunctional Co-Solvent for Practical Aqueous Zn-Ion Batteries

The practical application of aqueous Zn-ion batteries (AZIBs) is hindered by the crazy Zn dendrites growth and the H2O-induced side reactions, which rapidly consume the Zn anode and H2O molecules, especially under the lean electrolyte and Zn anode. Herein, a natural disaccharide, d-trehalose (DT), is exploited as a novel multifunctional co-solvent to address the above issues. Molecular dynamics simulations and spectral characterizations demonstrate that DT with abundant polar -OH groups can form strong interactions with Zn2+ ions and H2O molecules, and thus massively reconstruct the coordination structure of Zn2+ ions and the hydrogen bonding network of the electrolyte. Especially, the strong H-bonds between DT and H2O molecules can not only effectively suppress the H2O activity but also prevent the rearrangement of H2O molecules at low temperature. Consequently, the AZIBs using DT30 electrolyte can show high cycling stability even under lean electrolyte (E/C ratio = 2.95 µL mAh-1), low N/P ratio (3.4), and low temperature (-12 °C). As a proof-of-concept, a Zn||LiFePO4 pack with LiFePO4 loading as high as 506.49 mg can be achieved. Therefore, DT as an eco-friendly multifunctional co-solvent provides a sustainable and effective strategy for the practical application of AZIBs.

3D Fast Sodium Transport Network of MoS2 Endowed by Coupling of Sulfur Vacancies and Sn Doping for Outstanding Sodium Storage

A sulfur vacancy-rich, Sn-doped as well as carbon-coated MoS2 composite (Vs-SMS@C) is rationally synthesized via a simple hydrothermal method combined with ball-milling reduction, which enhances the sodium storage performance. Benefiting from the 3D fast Na+ transport network composed of the defective carbon coating, Mo─S─C bonds, enlarged interlayer spacing, S-vacancies, and lattice distortion in the composite, the Na+ storage kinetics is significantly accelerated. As expected, Vs-SMS@C releases an ultrahigh reversible capacity of 1089 mAh g-1 at 0.1 A g-1, higher than the theoretical capacity. It delivers a satisfactory capacity of 463 mAh g-1 at a high current density of 10 A g-1, which is the state-of-the-art rate capability compared to other MoS2 based sodium ion battery anodes to the knowledge. Moreover, a super long-term cycle stability is achieved by Vs-SMS@C, which keeps 91.6% of the initial capacity after 3000 cycles under the current density of 5 A g-1 in the voltage of 0.3-3.0 V. The sodium storage mechanism of Vs-SMS@C is investigated by employing electrochemical methods and ex situ techniques. The synergistic effect between S-vacancies and doped-Sn is evidenced by DFT calculations. This work opens new ideas for seeking excellent metal sulfide anodes.

Graphene-based iron single-atom catalysts for electrocatalytic nitric oxide reduction: a first-principles study

The electrocatalytic NO reduction reaction (NORR) emerges as an intriguing strategy to convert harmful NO into valuable NH3. Due to their unique intrinsic properties, graphene-based Fe single-atom catalysts (SACs) have gained considerable attention in electrocatalysis, while their potential for NORR and the underlying mechanism remain to be explored. Herein, using constant-potential density functional theory calculations, we systematically investigated the electrocatalytic NORR on the graphene-based Fe SACs. By changing the local coordination environment of Fe single atoms, 26 systems were constructed. Theoretical results show that, among these systems, the Fe SAC coordinated with four pyrrole N atoms and that co-coordinated with three pyridine N atoms and one O atom exhibit excellent NORR activity with low limiting potentials of -0.26 and -0.33 V, respectively, as well as have high selectivity toward NH3 by inhibiting the formation of byproducts, especially under applied potential. Furthermore, electronic structure analyses indicate that NO molecules can be effectively adsorbed and activated via the electron "donation-backdonation" mechanism. In particular, the d-band center of the Fe SACs was identified as an efficient catalytic activity descriptor for NORR. Our work could stimulate and guide the experimental exploration of graphene-based Fe SACs for efficient NORR toward NH3 under ambient conditions.

Precise Tuning of Hollow and Pore Size of Bimetallic MOFs Derivate to Construct High-Performance Nanoscale Materials for Supercapacitors and Sodium-Ion Batteries

Precise control of pore volume and size of carbon nanoscale materials is crucial for achieving high capacity and rate performances of charge/discharge. In this paper, starting from the unique mechanism of the role of In, Zn combination, and carboxyl functional groups in the formation of the lumen and pore size, the composition of InZn-MIL-68 is regulated to precisely tune the diameter and wall pore size of the hollow carbon tubes. The hollow carbon nanotubes (CNT) with high-capacity storage and fast exchange of Na+ ions and charges are prepared. The CNT possess ultra-high specific capacitance and ultra-long cycle life and also offer several times higher Na+ ion storage capacity and rate performance than the existing CNTs. Density functional theory calculations and tests reveal that these superior characteristics are attributed to the spacious hollow structure, which provides sufficient space for Na+ storage and the tube wall's distinctive porosity of tube wall as well as open ends for facilitating Na+ rapid desorption. It is believed that precise control of sub-nanopore volume and pore size by tuning the composition of the carbon materials derived from bimetallic metal-organic frameworks (MOFs) will establish the basis for the future development of high-energy density and high-power density supercapacitors and batteries.

Yolk-Shell MnSe/ZnSe Heterostructures with Selenium Vacancies Encapsulated in Carbontubes for High-Efficiency Sodium/Potassium Storage

The pursuit of high-performance batteries has propelled the investigation into advanced materials and design methodologies. Herein, the yolk-shell MnSe/ZnSe heterojunction encapsulated in hollow carbontubes (MnSe/ZnSe@HCTs) is prepared as a prospective electrode material for sodium/potassium batteries. The band structure in the heterojunction is methodically adjusted and regulated by intentionally utilizing Mn with unpaired electrons in the 3d orbital. The ZnSe shell confer effectively mitigates volumetric expansion challenges inherent in ions insertion/extraction processes and 1D carbontubular conductive substrate avert the aggregation of MnSe/ZnSe nanoparticles. Concurrently, the heterojunctions implantation induces sublattice distortion and charge redistribution, enriching active sites and regulating band structure. The selenium vacancies within these heterojunctions contribute to the provision of abundant active sites, thereby promoting efficient ions insertion/extraction. In sodium-ion batteries (SIBs), MnSe/ZnSe@HCTs present a superior capacity of 475 mA hg-1 at 0.1 A g-1 and sustains a capacity of 408.5 mAh g-1 even after 1000 cycles. In potassium-ion batteries (KIBs), MnSe/ZnSe@HCTs deliver a higher specific capacity of 422 mAh g-1 at a current density of 0.1 A g-1 and maintain a high coulombic efficiency of 99% after 1000 cycles. The yolk-shell structured MnSe/ZnSe heterojunction demonstrates excellent electrode properties for high-performance sodium/potassium batteries, holding significant promise for future energy storage applications.

Multilevel Gradient-Ordered Silicon Anode with Unprecedented Sodium Storage

While cost-effective sodium-ion batteries (SIBs) with crystalline silicon anodes promise high theoretical capacities, they perform poorly because silicon stores sodium ineffectively (capacity <40 mAh g-1 ). To address this issue, herein an atomic-order structural-design tactic is adopted for obtaining unique multilevel gradient-ordered silicon (MGO-Si) by simple electrochemical reconstruction. In situ-formed short-range-, medium-range-, and long-range-ordered structures construct a stable MGO-Si, which contributes to favorable Na-Si interaction and fast ion diffusion channels. These characteristics afford a high reversible capacity (352.7 mAh g-1 at 50 mA g-1 ) and stable cycling performance (95.2% capacity retention after 4000 cycles), exhibiting record values among those reported for pure silicon electrodes. Sodium storage of MGO-Si involves an adsorption-intercalation mechanism, and a stepwise construction strategy of gradient-ordered structure further improves the specific capacity (339.5 mAh g-1 at 100 mA g-1 ). Reconstructed Si/C composites show a high reversible capacity of 449.5 mAh g-1 , significantly better than most carbonaceous anodes. The universality of this design principle is demonstrated for other inert or low-capacity materials (micro-Si, SiO2 , SiC, graphite, and TiO2 ), boosting their capacities by 1.5-6 times that of pristine materials, thereby providing new solutions to facilitate sodium storage capability for better-performing battery designs.

A Universal Cross-Synthetic Strategy for Sub-10 nm Metal-Based Composites with Excellent Ion Storage Kinetics

The sub-10 nm metal-based nanomaterials (SMNs) show great potential for the electrochemical energy storage field. However, their ion storage capacity and stability suffer from severe agglomeration and interface problems. Herein, a universal strategy is reported to synthesize a wide range of SMNs (e.g., metal, nitride, oxide, and sulfides) embedded in free-standing carbon foam (SMN/FC-F) composite electrodes by crossing the interfacial confinement of NaCl self-assembly with the thermal-mechanical coupling of powder metallurgy. The pressure-enhanced NaCl self-assembly interfacial confinement is greatly beneficial to preventing SMN agglomeration and promoting SMNs embedded in FC-F which originate from the welding of carbon nanosheets. They are confirmed via a series of advanced characterizations including X-ray photoelectron spectroscopy, and spherical aberration-corrected scanning transmission electron microscopy, with theoretical computations. Benefiting from the unique structure, SMNs/FC-F delivers ultrafast and stable ion-storage kinetics. As a proof-of-concept demonstration, the MoS2 /FC-F shows excellent ion storage kinetics and superior long-term cycling performance for ion storage (e.g., Na3 V2 (PO4 )2 O2 F/C//MoS2 /FC-F sodium-ion batteries exhibit a high reversible capacity of 185 mAh g-1 at 0.5 A g-1 with a decay rate of 0.05% per cycle.). This work provides a new opportunity to design and fabricate promising SMN-based free-standing working electrodes for electrochemical energy storage and conversion applications.

Soft-Rigid Heterostructures with Functional Cation Vacancies for Fast-Charging and High-Capacity Sodium Storage

Optimizing charge transfer and alleviating volume expansion in electrode materials are critical to maximize electrochemical performance for energy-storage systems. Herein, an atomically thin soft-rigid Co9 S8 @MoS2 core-shell heterostructure with dual cation vacancies at the atomic interface is constructed as a promising anode for high-performance sodium-ion batteries. The dual cation vacancies involving VCo and VMo in the heterostructure and the soft MoS2 shell afford ionic pathways for rapid charge transfer, as well as the rigid Co9 S8 core acting as the dominant active component and resisting structural deformation during charge-discharge. Electrochemical testing and theoretical calculations demonstrate both excellent Na+ -transfer kinetics and pseudocapacitive behavior. Consequently, the soft-rigid heterostructure delivers extraordinary sodium-storage performance (389.7 mA h g-1 after 500 cycles at 5.0 A g-1 ), superior to those of the single-phase counterparts: the assembled Na3 V2 (PO4 )3 ||d-Co9 S8 @MoS2 /S-Gr full cell achieves an energy density of 235.5 Wh kg-1 at 0.5 C. This finding opens up a unique strategy of soft-rigid heterostructure and broadens the horizons of material design in energy storage and conversion.

Unraveling the Ion Uptake Capacitive Deionization of Sea- and Highly Saline-Water by Sulfur and Nitrogen Co-Doped Porous Carbon Modified with Molybdenum Sulfide

In parallel to the depletion of potable water reservoirs, novel technologies have been developed for seawater softening, as it is the most abundant source for generating deionized water. Although salt removal at subosmotic pressures and ambient temperatures by applying low-operating potentials with high energy efficiency made capacitive deionization (CDI) an advantageous water-softening process, its practical application is limited by insufficient ion removal capacity and low concentration influent. The performance of a CDI system is in progress with engineering the electrode active materials, also facilitating the advance design in highly saline- and seawater study. Herein, an innovative strategy was developed to provide high-performance CDI systems based on efficient and electrochemical ion-uptake active materials with a simple initial preparation. Nitrogen-doped porous carbons (N-pCs) received benefits from a high specific surface area and good surface wettability. The N-pCs were modified with molybdenum oxide/sulfide intercalative array and developed as CDI electrode active materials for desalination of both low/medium saline- and seawater. The MoS2/S,N-pC electrode materials exhibited perfect optimized salt adsorption capacity (SACs) of 47.9 mg g-1 when compared to N-pC (37.9 mg g-1) and MoO3/N-pC (39.6 mg g-1) counterparts at 1.4 V in a 750 ppm NaCl solution. In addition, the assembled CDI cells exhibited reasonable cycle stability and retained 96.7% of their initial SAC in continuous CDI cycles for 128,000 s. The fabricated CDI cell rendered an excellent salt removal efficiency (SRE, %) of 13.34% from the real seawater sample at 1.2 V. In detail, the SRE % of the NaCl, KCl, MgCl2, and CaCl2 soluble salts with respect to seawater sample exhibited a remarkable SRE % of 30.8%, 36%, 32.6%, and 19.3%, respectively. These SRE % values (>13.34%) provide convincing evidence on the reasonable ion uptake capability of the fabricated CDI cells for removing Na+, K+, Mg2+, and Ca2+ ions compared to other soluble component. The advanced cell design parallel to the promising outcomes provided herein makes these CDI systems immensely propitious for efficient water softening.

FeN Coordination Induced Ultralong Lifetime of Sodium-Ion Battery with the Cycle Number Exceeding 65 000

Sodium-ion batteries (SIBs) have received increasing attention because of their appealing cell voltages and cost-effective features. However, the atom aggregation and electrode volume variation inevitably deteriorate the sodium storage kinetics. Here a new strategy is proposed to boost the lifetime of SIB by synthesizing sea urchin-like FeSe2 /nitrogen-doped carbon (FeSe2 /NC) composites. The robust FeN coordination hinders the Fe atom aggregation and accommodates the volume expansion, while the unique biomorphic morphology and high conductivity of FeSe2 /NC enhance the intercalation/deintercalation kinetics and shorten the ion/electron diffusion length. As expected, FeSe2 /NC electrodes deliver excellent half (387.6 mAh g-1 at 20.0 A g-1 after 56 000 cycles) and full (203.5 mAh g-1 at 1.0 A g-1 after 1200 cycles) cell performances. Impressively, an ultralong lifetime of SIB composed of FeSe2 /Fe3 Se4 /NC anode is uncovered with the cycle number exceeding 65 000. The sodium storage mechanism is clarified with the aid of density function theory calculations and in situ characterizations. This work hereby provides a new paradigm for enhancing the lifetime of SIB by constructing a unique coordination environment between active material and framework.

Diatomite-Templated Synthesis of Single-Atom Cobalt-Doped MoS2 /Carbon Composites to Boost Sodium Storage

2D transition metal dichalcogenides (TMDCs) and single-atom catalysts (SACs) are promising electrodes for energy conversion/storage because of the layered structure and maximum atom utilization efficiency. However, the integration of such two type materials and the relevant sodium storage applications remain daunting challenges. Here, an ingenious diatomite-templated synthetic strategy is designed to fabricate single-atom cobalt-doped MoS2 /carbon (SA Co-MoS2 /C) composites toward the high-performance sodium storage. Benefiting from the unique hierarchical structure, high electron/sodium-ion conductivity, and abundant active sites, the obtained SA Co-MoS2 /C reveals remarkable specific capacity (≈604.0 mAh g-1 at 0.1 A g-1 ), high rate performance, and outstanding long cyclic stability. Particularly, the sodium-ion full cell composed of SA Co-MoS2 /C anode and Na3 V2 (PO4 )3 cathode demonstrates unexpected stability with the cycle number exceeded 1200. The internal sodium storage mechanism is clarified with the aid of density functional theory calculations and in situ experimental characterizations. This work not only represents a substantial leap in terms of synthesizing SACs on 2D TMDCs but also provides a crucial step toward the practical sodium-ion battery applications.

Densified vertically lamellar electrode architectures for compact energy storage

As one of the most compact electrochemical energy storage systems, lithium-ion batteries (LIBs) are playing an indispensable role in the process of vehicle electrification to accelerate the shift to sustainable mobility. Making battery electrodes thicker is a promising strategy for improving the energy density of LIBs which is essential for applications with weight or volume constraints, such as electric-powered transportation; however, their power densities are often significantly restricted due to elongated and tortuous charge traveling distances. Here, we propose an effective methodology that couples bidirectional freeze-casting and compression-induced densification to create densified vertically lamellar electrode architectures for compact energy storage. The vertically lamellar architectures not only overcome the critical thickness limit for conventional electrodes but also facilitate and redistribute the lithium-ion flux enabling both high rate capability and stable cyclability. Furthermore, this proposed methodology is universal as demonstrated in various electrochemical active material systems. This study offers a facile approach that realizes simultaneous high energy and high power in high-loading battery electrodes and provides useful rationales in designing electrode architectures for scalable energy storage systems.

Defect-rich Mo2S3 loaded wood-derived carbon acts as a spacer in lithium-sulfur batteries: forming a polysulfide capture net and promoting fast lithium flux

Due to the sluggish kinetics of sulfur conversion and the large volume change of the lithium anode, along with the formation of lithium dendrites, lithium-sulfur batteries (LSBs) usually exhibit severe capacity decay and poor cycle life. It is necessary to consider the factors associated with cathodes, separators and anodes in an integrated manner to solve the problems existing in LSBs. In this paper, a vertically aligned porous carbon decorated with transition metal sulfides was introduced between a cathode and an anode to comprehensively solve the problems of LSBs. Widely existing natural wood was used as the framework structure, and Mo₂S₃ with abundant sulfur vacancies was deposited into its channels. Theoretical calculations and experimental results have confirmed a low energy barrier for sulfur conversion and the presence of a strong electric field around the spacer, which benefits fast ion transportation. As a result, on employing the multifunctional spacer, LSB full cells delivered a high initial capacity and a long cycle life. This study provides a reference for reducing development cost, simplifying optimization steps and promoting the commercial application of LSBs.

A High-Temperature Accelerometer with Excellent Performance Based on the Improved Graphene Aerogel

A high-temperature accelerometer plays an important role for ensuring normal operation of equipment in aerospace, such as monitoring and identifying abnormal vibrations of aircraft engines. Phase transitions of piezoelectric crystals, mechanical failure and current leakage of piezoresistive/capacitive materials are the prominent inherent limitations of present high-temperature accelerometers working continuously above 973 K. With the rapid development of aerospace, it is a great challenge to develop a new type of vibration sensor to meet the crucial demands at high temperature. Here we report a high-temperature accelerometer working with a contact resistance mechanism. Based on the improved graphene aerogel (GA) prepared by a modulated treatment process, the accelerometer can operate continuously and stably at 1073 K and intermittently at 1273 K. The developed sensor is lightweight (sensitive element <5 mg) and has high sensitivity (an order of magnitude higher than MEMS accelerometers) and wide frequency response range (up to 5 kHz at 1073 K) with marked stability, repeatability and low nonlinearity error (<1%). These merits are attributed to the excellent and stable mechanical properties of the improved GA in the range of 299-1073 K. The accelerometer could be a promising candidate for high-temperature vibration sensing in space stations, planetary rovers and others.

How Size and Strain Effect Synergistically Improve Electrocatalytic Activity: A Systematic Investigation Based on PtCoCu Alloy Nanocrystals

To reveal how the size effect and strain effect synergistically regulate the mass activity (MA) and specific activity (SA) of Pt alloy nanocrystal catalysts in oxygen reduction reaction (ORR), remains to be difficult due to the highly entangled factors. In this work, six ternary PtCoCu catalysts with sequentially changed composition, size, and compression strain are prepared. It is found that the smaller the alloy particles, the higher the electrochemical active surface area (ECSA) and MA values, that is, the particle size plays a decisive role in the size of the ECSA and MA. While, along alloy size decrease, the intrinsic activity SA first increases, then remains unchanged, and finally rapidly increases again. This detailed analysis shows that for the alloys above 4 nm, it is the surface coordination number that decides the SA, while for those below 4 nm, it is the well-regulated compression strain that determines the SA. Particularly, Pt₄₇ Co₂₆ Cu₂₇ demonstrates the MA of 1.19 A mg_Pt ^-1 and SA of 1.48 mA cm^-2 , being 7.9 and 6.4 times those of commercial Pt/C respectively, representing an especially superior ORR catalyst.

MoS2/CoS heterostructures grown on carbon cloth as free-standing anodes for high-performance sodium-ion batteries

Heterostructure construction with mixed transition metal sulfides has been recognized as a promising strategy to boost the performance of sodium-ion batteries (SIBs). Herein, a carbon-decorated MoS₂/CoS heterostructure on carbon cloth (MoS₂/CoS@CC) as a free-standing anode for SIBs was synthesized via a facile growth-carbonization strategy. In the composite, the generated built-in electric field at MoS₂ and CoS heterointerfaces is beneficial for elevating the electron conductivity, thus expediting the Na-ion transport rate. Moreover, different redox potentials between MoS₂ and CoS can effectively mitigate the mechanical strain induced by repeated Na⁺ de-/intercalation, thus ensuring the structural integrity. In addition, the carbon skeleton derived from the carbonization of glucose can enhance the conductivity of the electrode and maintain the structural integrity. Consequently, the resulting MoS₂/CoS@CC electrode delivers a reversible capacity of 605 mA h g^-1 at 0.5 A g^-1 after 100 cycles, and prominent rate performance (366 mA h g^-1 at 8.0 A g^-1). Theoretical calculations also confirm that the establishment of a MoS₂/CoS heterojunction can powerfully promote the electron conductivity, thereby enhancing the Na-ion diffusion kinetics.

Atomically dispersed Mn atoms coordinated with N and O within an N-doped porous carbon framework for boosted oxygen reduction catalysis

Developing efficient and robust catalysts to replace Pt group metals for the oxygen reduction reaction (ORR) is conducive to achieving highly efficient energy conversion. Here, we develop a general ion exchange strategy to construct highly efficient ORR catalysts consisting of various atomically dispersed metal atoms anchored on N-doped porous carbon (M-SAs/NC) to investigate the atomic structure-catalytic activity relationship. The structure characterization results demonstrated that the achieved atomic structure varied due to the presence of different metal centers. Mn-SAs/NC consists of MnN₃O₁ centers, in which the Mn single atoms are stabilized by 3 N and 1 O. In contrast, the center metals in Fe-/Co-/Cu single-atom catalysts are coordinated by merely N atoms. Mn-SAs/NC delivers superior performance for the ORR with a half-wave potential (E_1/2) of 0.91 V vs. RHE in 0.1 M KOH solution, outperforming that of the commercial Pt/C catalyst and the control Fe-/Co-/Cu single-atom catalysts. Furthermore, Mn-SAs/NC also shows excellent methanol tolerance and stability up to 5000 cycles. Density functional theory (DFT) calculations reveal that Mn single atom catalysts with MnN₃O₁ centers contributed to the superior ORR performance with lower energy barriers and optimized adsorption capacity of intermediates. These findings provide insights into the design and development of specific coordinated structures of atomically dispersed catalysts to facilitate the practical applications of energy conversion.

Bond modulation of MoSe2+x driving combined intercalation and conversion reactions for high-performance K cathodes

The urgent demand for large-scale global energy storage systems and portable electronic devices is driving the need for considerable energy density and stable batteries. Here, Se atoms are introduced between MoSe₂ layers (denoted as MoSe_2+x ) by bond modulation to produce a high-performance cathode for potassium-ion batteries. The introduced Se atoms form covalent Se-Se bonds with the Se in MoSe₂, and the advantages of bond modulation are as follows: (i) the interlayer spacing is enlarged which increases the storage space of K⁺; (ii) the system possesses a dual reaction mechanism, and the introduced Se can provide an additional conversion reaction when discharged to 0.5 V, which improves the capacity further; (iii) the Se atoms confined between MoSe₂ layers do not give rise to the shuttle effect. MoSe_2+x is compounded with rGO (MoSe_2+x -rGO) as a cathode for potassium-ion batteries and displays an ultrahigh capacity (235 mA h g^-1 at 100 mA g^-1), a long cycle life (300 cycles at 100 mA g^-1) and an extraordinary rate performance (135 mA h g^-1 at 1000 mA g^-1 and 89 mA h g^-1 at 2000 mA g^-1). Pairing the MoSe_2+x -rGO cathode with graphite, the full cell delivers considerable energy density compared to other K cathode materials. The MoSe_2+x -rGO cathode also exhibits excellent electrochemical performance for lithium-ion batteries. This study on bond modulation driving combined intercalation and conversion reactions offers new insights into the design of high-performance K cathodes.

Supramolecular Framework Constructed by Dendritic Nanopolymer for Stable Flexible Perovskite Resistive Random-Access Memory

The 3D supramolecular framework (3D-SF) is constructed in this work through the hydrogen bond assisted self-assembly of spherical dendritic nanopolymer to regulate the flexibility, stability, and resistive switching (RS) performance of perovskite resistive random-access memory (RRAM). Herein, the 3D-SF network acts as the perovskite crystallization template to regulate the perovskite crystallization process due to its coordination interaction of functional groups with the perovskite grains, presenting the uniform, pinhole-free, and compact perovskite morphology for stable flexible RRAM. The 3D-SF network in situ stays at the perovskite intergranular boundaries to crosslink the perovskite grains. The RS performance of 3D-SF-modified perovskite RRAM device is evidently improved to the ON/OFF ratio of 10⁵ , the cycle number of 500 times, and the data retention time of 10⁴ s. The 50-days exposure of unencapsulated RRAM device at ambient environment still makes the ON/OFF ratio to be kept at ≈10⁴ , indicating the potential of long-term stable multilevel storage in the high-density data storage. The bending action under different radius also does not change the RS performance due to the excellent bending-resistant ability of 3D-SF-modified perovskite film. This work explores a novel polymer additive strategy to construct the 3D supramolecular framework for stable flexible perovskite optoelectronic devices.

Enhanced in-plane thermal conductivity of polyimide-based composites via in situ interfacial modification of graphene

Interfacial thermal resistance is the main barrier restricting the heat dissipation of thermal management materials in electronic equipment. The interface structure formed by covalent bonding is an effective way to promote interfacial heat transfer. Herein, an integrated composite with multi-aspect covalent bonding beneficial for heat transmission is constructed by polyimide (PI) polymerization with maleimide modified graphene nanosheets (M@GNS). The interfacial structure with low thermal resistance built by covalent bonding and oriented graphene arrangement initiated by the coating process makes the in-plane thermal conductivity of the composite as high as 16.10 W m^-1 K^-1. Finite element simulation and 1000 bending tests are carried out to further verify the performance advantages of the integrated structure in the internal thermal diffusion and long-term use of the composite. M@GNS/PI with integrated structure provides extra heat transfer channels for heat dissipation, possibly providing an effective way to address the traditional thermal accumulation issue of electronic devices.

Integrated structure design and synthesis of a pitaya-like SnO2/N-doped carbon composite for high-rate lithium storage capability

Tin dioxide (SnO₂) with a high theoretical capacity of 1494 mA h g^-1 has great potential to break through the capacity limitation of the conventional graphite anode (372 mA h g^-1) in lithium-ion batteries. However, its practical application still faces several obstacles such as high volumetric expansion and poor electrical conductivity. To solve these problems, innovative design and synthesis of SnO₂-based nanocomposite structures are necessary. Herein, we demonstrate an integrated design of a hierarchical pitaya-like P-SnO₂/C@NC core-shell nanostructure which includes the core of SnO₂ nanoparticles (∼4-12 nm) uniformly embedded in the porous carbon sphere and the shell of a continuous nitrogen-doped carbon (NC) layer. Specifically, during repetitive lithiation and delithiation processes, the ultrasmall SnO₂ nanoparticles reduce the internal stress greatly, the porous carbon matrix provides buffer space for a large volume change, and the N-doped carbon shell further guarantees the whole structure unit sufficient electrical conductivity and structural stability. Consequently, the resultant battery exhibits a reversible capacity of 936.8 mA h g^-1 after 100 cycles at 100 mA g^-1 and even an average capacity of 460.0 mA h g^-1 at a high current density of 3.2 A g^-1. The excellent electrochemical performance of pitaya-like SnO₂/C@NC proves the efficacy of this structure design and thus provides significant reference for the construction of other electrode materials in rechargeable alkali metal ion batteries.

Effective Solution toward the Issues of Zn-Based Anodes for Advanced Alkaline Ni-Zn Batteries

Alkaline nickel-zinc (Ni-Zn) batteries, as traditional rechargeable aqueous batteries, possess an obvious advantage in terms of energy density, but their development has been hindered by the anode-concerned problems, Zn dendrites, self-corrosion, passivation, deformation, and hydrogen evolution reaction (HER). Herein, to solve these problems, a dual protective strategy is proposed toward the anode using ZnO as an initial active material, including a C coating on ZnO (ZnO@C) and a thin poly(vinyl alcohol) (PVA) layer coating on the electrode (ZnO@C-PVA). In a three-electrode configuration, the reversible capacity can reach 600 mAh g^-1 for the ZnO@C-PVA. Using excessive commercial Ni(OH)₂ as the cathode, the alkaline Ni-Zn cells exhibit good electrochemical performance: Discharge capacity can be as high as 640-650 mAh g^-1 at 4 A g^-1 with a Coulomb efficiency (CE) as high as 97-99% after activity, suggesting low self-corrosion and HER. Capacity retention is 97% after 1200 cycles, indicating rather good durability. The discharge capacity is even slightly increased with the increase of charge/discharge current density (≤8 A g^-1), implying good rate performance. Additionally, the discharge voltage can reach 1.8 V (midpoint value) at various current densities, reflecting the fast reaction kinetics of the anode. Most importantly, no Zn dendrites and passivation are observed after long-term cycling. The strategy proposed here can solve the anode-concerned problems effectively, exhibiting a high application prospect.

Graphene based magnetite carbon nanofiber composites as anodes for high-performance Li-ion batteries

For energy storage applications, highly flexible free-standing electrodes are ideal for the fabrication of electrochemical cells.

Prediction of boridenes as high-performance anodes for alkaline metal and alkaline Earth metal ion batteries

We conducted a comprehensive density functional theory investigation using the r²SCAN-rVV10 functional on the structural stability and electrochemical properties of boridenes for their use as anode materials in rechargeable alkaline (earth) metal-ion batteries (Li⁺, Na⁺, K⁺, Mg²⁺ and Ca²⁺). According to first-principles molecular dynamics simulations and reaction thermodynamic calculations, Mo_4/3B₂(OH)₂ and Mo_4/3B₂F₂ are unstable in the presence of alkaline (earth) metal ions due to the surface-conversion reactions between the surface terminations and adsorbates. Meanwhile, the bare Mo_4/3B₂ and Mo_4/3B₂O₂ monolayers not only can accommodate alkaline (earth) metal ions, but also form stable multi-layer adsorption structures for most of the studied metal ions (Li⁺, Na⁺, K⁺, Mg²⁺ and Ca²⁺). The predicted gravimetric capacities of the bare Mo_4/3B₂ monolayer (Mo_4/3B₂O₂) are 625.9 mA h g^-1 (357.3 mA h g^-1), 247.20 mA h g^-1 (392.1 mA h g^-1), 101.8 mA h g^-1 (206.4 mA h g^-1), 667.0 mA h g^-1, and 413.0 mA h g^-1 (485.4 mA h g^-1) for Li⁺, Na⁺, K⁺, Mg²⁺ and Ca²⁺ ions, respectively. The bare Mo_4/3B₂ exhibits lower onset charging open circuit voltages for alkaline (earth) metal ions than that of Mo_4/3B₂O₂. The diffusivities of the metal ions were revealed to be high on the boridene monolayer especially for the outer fully stable adsorption layers, where the migration energy barriers were found to be less than 0.10 eV. Similar to that of MXenes, the negative electron cloud (NEC) also plays a vital role in stabilizing the observed multi-layer adsorption structures for various metal ions on either the bare Mo_4/3B₂ or Mo_4/3B₂O₂ monolayer.

Thermodynamic Transformation of Crystalline Organic Hybrid Iron Selenide to FexSey@CN Microrods for Sodium Ion Storage

Carbon-coated metal chalcogenide composites have been demonstrated as one type of promising anode material for sodium-ion batteries (SIBs). However, combining carbon materials with micronanoparticles of metal chalcogenide always involve complicated processes, such as polymer coating, carbonization, and sulfidation/selenization. To address this issue, herein, we reported a series of carbon-coated FexSey@CN (FexSey = FeSe2, Fe3Se4, Fe7Se8) composites prepared via the thermodynamic transformation of a crystalline organic hybrid iron selenide [Fe(phen)2](Se4) (phen = 1,10-phenanthroline). By pyrolyzing the bulk crystals of [Fe(phen)2](Se4) at different temperatures, FexSey microrods were formed in situ, where the nitrogen-doped carbon layers were coated on the surface of the microrods. Moreover, all the as-prepared FexSey@CN composites exhibited excellent sodium-ion storage capabilities as anode materials in SIBs. This work proves that crystalline organic hybrid metal chalcogenides can be used as a novel material system for the in situ formation of carbon-coated metal chalcogenide composites, which could have great potential in the application of electrochemical energy storage.

Human-muscle-inspired single fibre actuator with reversible percolation

Artificial muscles are indispensable components for next-generation robotics capable of mimicking sophisticated movements of living systems. However, an optimal combination of actuation parameters, including strain, stress, energy density and high mechanical strength, is required for their practical applications. Here we report mammalian-skeletal-muscle-inspired single fibres and bundles with large and strong contractive actuation. The use of exfoliated graphene fillers within a uniaxial liquid crystalline matrix enables photothermal actuation with large work capacity and rapid response. Moreover, the reversible percolation of graphene fillers induced by the thermodynamic conformational transition of mesoscale structures can be in situ monitored by electrical switching. Such a dynamic percolation behaviour effectively strengthens the mechanical properties of the actuator fibres, particularly in the contracted actuation state, enabling mammalian-muscle-like reliable reversible actuation. Taking advantage of a mechanically compliant fibre structure, smart actuators are readily integrated into strong bundles as well as high-power soft robotics with light-driven remote control.

Free-Standing, Self-Doped Porous Hard Carbon: Na-Ion Storage with Enhanced Initial Coulombic Efficiency

The use of porous hard carbons (PHCs) as electrode materials in sodium-ion batteries has great potential; however, the exposure of large surface areas to electrolyte flow results in irregular and irreversible solid electrolyte interfaces (SEIs), leading to deteriorated ionic and electronic mobility and inferior initial Coulombic efficiency (ICE). These issues can be addressed through suitable structural modifications of PHC materials. Herein, the integration of high-surface-area PHCs with carbon nanofibers (CNFs) was accomplished by a simple electrospinning technique, which resulted in a uniform and reversible SEI layer. In the meantime, the CNFs' mesh provided connectivity and conductivity in the as-integrated electrodes, whereas PHCs offered fast diffusion kinetics and high Na⁺ ion storage capacity. Additionally, PHC integration with CNFs demonstrated an excellent ICE of 77% and a specific capacity of 505 mAh/g at 25 mA/g. Furthermore, the conjugated microstructure also provided flexibility and stability to the electrode (260 mAh/g after 500 cycles). This remarkable synergy may promote the development of free-standing, flexible, and highly porous properties in a single material for advanced energy storage applications.

Hard Carbons as Anodes in Sodium-Ion Batteries: Sodium Storage Mechanism and Optimization Strategies

Sodium-ion batteries (SIBs) are regarded as promising alternatives to lithium-ion batteries (LIBs) in the field of energy, especially in large-scale energy storage systems. Tremendous effort has been put into the electrode research of SIBs, and hard carbon (HC) stands out among the anode materials due to its advantages in cost, resource, industrial processes, and safety. However, different from the application of graphite in LIBs, HC, as a disordered carbon material, leaves more to be completely comprehended about its sodium storage mechanism, and there is still plenty of room for improvement in its capacity, rate performance and cycling performance. This paper reviews the research reports on HC materials in recent years, especially the research process of the sodium storage mechanism and the modification and optimization of HC materials. Finally, the review summarizes the sterling achievements and the challenges on the basis of recent progress, as well as the prospects on the development of HC anode materials in SIBs.

Electrolyte Salts and Additives Regulation Enables High Performance Aqueous Zinc Ion Batteries: A Mini Review

Aqueous zinc ion batteries (ZIBs) are regarded as one of the most ideally suited candidates for large-scale energy storage applications owning to their obvious advantages, that is, low cost, high safety, high ionic conductivity, abundant raw material resources, and eco-friendliness. Much effort has been devoted to the exploration of cathode materials design, cathode storage mechanisms, anode protection as well as failure mechanisms, while inadequate attentions are paid on the performance enhancement through modifying the electrolyte salts and additives. Herein, to fulfill a comprehensive aqueous ZIBs research database, a range of recently published electrolyte salts and additives research is reviewed and discussed. Furthermore, the remaining challenges and future directions of electrolytes in aqueous ZIBs are also suggested, which can provide insights to push ZIBs' commercialization.

Molybdenum sulfide selenide ultrathin nanosheets anchored on carbon tubes for rapid-charging sodium/potassium-ion batteries

The structural stability and reaction kinetics of anodes are essential factors for high-performance battery systems. Herein, the molybdenum sulfide selenide (MoSSe) nanosheets anchored on carbon tubes (MoSSe@CTs) are synthesized by a facile hydrothermal method combining with further selenization/calcination treatment. The unique tubular carbon skeletons expose abundant active sites for the well-dispersed growth of MoS₂ ultrathin nanosheets on both sides of the tubular carbon skeleton. In addition, the further selenization treatment can expand the interlayer spacing of molybdenum sulfide (MoS₂) nanosheets and facilitate the fast sodium/potassium-ion transition and storage. When used in sodium-ion batteries (SIBs), MoSSe@CTs electrode delivers a specific capacity of 486 mAh g^-1 at 1 A g^-1 and retains a stable reversible capacity of 465 mAh g^-1 after 1000 cycles, indicating its good cycling stability. For potassium-ion batteries (KIBs), the MoSSe@CTs composite shows a capacity of 352 mA hg^-1 at 1 A g^-1 and a good cycling stability (maintains at 272 mA hg^-1 after 1000 cycles). This work shows informative guiding significance for exploring advanced electrode materials of sodium/potassium-ion batteries.

Tortuosity Engineering for Improved Charge Storage Kinetics in High-Areal-Capacity Battery Electrodes

The increasing demands of electronic devices and electric transportation necessitate lithium-ion batteries with simultaneous high energy and power capabilities. However, rate capabilities are often limited in high-loading electrodes due to the lengthy and tortuous ion transport paths with their electrochemical behaviors governed by complicated electrode architectures still elusive. Here, we report the electrode-level tortuosity engineering design enabling improved charge storage kinetics in high-energy electrodes. Both high areal capacity and high-rate capability can be achieved beyond the practical level of mass loadings in electrodes with vertically oriented architectures. The electrochemical properties in electrodes with various architectures were quantitatively investigated through correlating the characteristic time with tortuosity. The lithium-ion transport kinetics regulated by electrode architectures was further studied via combining the three-dimensional electrode architecture visualization and simulation. The tortuosity-controlled charge storage kinetics revealed in this study can be extended to general electrode systems and provide useful design consideration for next-generation high-energy/power batteries.

Decoupling layer metal-organic frameworks via ligand regulation to achieve ultra-thin carbon nanosheets for oxygen reduction electrocatalysis

2D imidazole MOFs are considered to be ideal carbon precursors for oxygen reduction reactions owing to their adjustable ligand components and durable coordination mode. Due to the massive electron delocalization in the lamella, the conjugative effect among 2D MOF layers immensely restricts the exposure of catalytic sites after carbonization, which makes the decoupling layer extremely important on the premise of ensuring activity. Herein, atomic thickness ultra-thin zinc-imidazole MOF precursors were prepared through a bottom-up ligand regulated strategy to achieve the aim of lamellar decoupling. The introduction of heterologous ligands excites stable delocalized electrons, resulting in a decrease in the interlayer force of 2D zinc-imidazole MOF precursors. Subsequent salt template-supported ammonia pyrolysis assisted the MOF-derived carbon sheets to grow along the transverse direction and optimize pore size distribution as did the doping nitrogen type. The MOF-derived carbon sheets demonstrated increasing mesopores and fringe graphitic N which could significantly promote the mass transfer and electron transfer speed during the oxygen reduction reaction. In addition, the obtained ultra-thin carbon delivered an outstanding onset potential (0.98 V vs. RHE) and durability (retaining 91% of the initial current after 12000 s of operation), showing tremendous commercial prospects in sustainable energy.

Recent Progress on Graphene-Based Nanocomposites for Electrochemical Sodium-Ion Storage

In advancing battery technologies, primary attention is paid to developing and optimizing low-cost electrode materials capable of fast reversible ion insertion and extraction with good cycling ability. Sodium-ion batteries stand out due to their inexpensive price and comparable operating principle to lithium-ion batteries. To achieve this target, various graphene-based nanocomposites fabricate strategies have been proposed to help realize the nanostructured electrode for high electrochemical performance sodium-ion batteries. In this review, the graphene-based nanocomposites were introduced according to the following main categories: graphene surface modification and doping, three-dimensional structured graphene, graphene coated on the surface of active materials, and the intercalation layer stacked graphene. Through one or more of the above strategies, graphene is compounded with active substances to prepare the nanocomposite electrode, which is applied as the anode or cathode to sodium-ion batteries. The recent research progress of graphene-based nanocomposites for SIBs is also summarized in this study based on the above categories, especially for nanocomposite fabricate methods, the structural characteristics of electrodes as well as the influence of graphene on the performance of the SIBs. In addition, the relevant mechanism is also within the scope of this discussion, such as synergistic effect of graphene with active substances, the insertion/deintercalation process of sodium ions in different kinds of nanocomposites, and electrochemical reaction mechanism in the energy storage. At the end of this study, a series of strategies are summarized to address the challenges of graphene-based nanocomposites and several critical research prospects of SIBs that provide insights for future investigations.

Vanadium dissolution at 30 °C and its suppression at a low temperature of -20 °C for a Na3V1.5Cr0.5(PO4)3 cathode

Na₃V_1.5Cr_0.5(PO₄)₃ cycled at 30 °C shows fast capacity decay, due to the migration of V ions into the electrolyte and the loss of V³⁺/V⁴⁺ redox. A low temperature of -20 °C attenuates V-ion dissolution, retains V³⁺/V⁴⁺ redox and improves the electrochemical performance, favorable for use in cold climates and high-altitude drones.

Hollow nanospheres constructed by ultrafine few-layered MoS2 partially with amorphous fragments homogeneously incorporated in N-doped amorphous carbon for enhanced lithium storage performance

The rational design of ultrathin and few-layered structures for three-dimensional MoS₂ nanospheres is crucial for achieving attractive lithium-ion batteries (LIBs). Herein, hollow nanospheres constructed by ultrafine and few-layered MoS₂ homogeneously incorporated in N-doped amorphous carbon (HUF-MoS₂/NC) have been successfully synthesized as high-performance anode for LIBs. Using Mo-glycerol spheres as templates and dopamine hydrochloride as coordination ligands, hollow Mo-glycerol-polydopamine precursors are formed with Mo-containing groups which are surrounded by organic carbon species. Consequently, the MoS₂ is confined to the nanoscale and grows partially amorphous fragments while being uniformly embedded in NC. This unique architecture can not only hinder the substantial restacking between MoS₂ interlayers, offering more active sites, but also vastly enhance the electrical conductivity and relieve the mechanical stress ascribed to volume changes. As a result, the HUF-MoS₂/NC composite anode exhibits excellent cyclic stability (980mAhg^-1 after 300 cycles at 0.2Ag^-1) and superior rate performance (498mAhg^-1 at 5.0Ag^-1) for LIBs.

Construction of three-dimensional cobalt sulfide/multi-heteroatom co-doped porous carbon as an efficient trifunctional electrocatalyst

Exploring cost-effective non-precious metal electrocatalysts is vital for the large-scale application of clean energy conversion devices (i.e., fuel cells, metal-air batteries and water electrolysers). Herein, we present the construction of a three-dimensional cobalt sulfide/multi-heteroatom co-doped carbon composite as a trifunctional electrocatalyst for the oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) through one-step sulfidation of zeolitic-imidazolate frameworks (ZIFs) using sulfur powder as a sulfur source. By virtue of the distinct periodic metal-nitrogen coordination structure and the abundant micropores within the ZIF precursor, sub-10 nm Co₉S₈ nanoparticles (NPs) are homogenously anchored on a Co, S and N multi-heteroatom co-doped carbon framework with a large specific surface area that exposes sufficient reactive sites for these electrocatalytic reactions. The optimized Co₉S₈/CoNSC exhibits outstanding ORR, OER and HER performance, comparable or even superior to those of commercial Pt/C and RuO₂. The small Co₉S₈ NPs and Co-N_x species embedded in the carbon matrix cooperatively catalyze the OER and ORR, while the HER catalysis is mainly contributed by Co₉S₈ NPs. Furthermore, the Co₉S₈/CoNSC shows outstanding anti-poisoning capability towards sulfur species during ORR catalysis with no obvious activity degradation observed in 0.1 M KOH containing 50 μM SO₃^2- species, significantly outperforming commercial Pt/C. The assembled rechargeable Zn-air battery using the Co₉S₈/CoNSC as a cathode shows a high power density (150 mW cm^-2) and the assembled water electrolyzer only requires 1.585 V at a current density of 10 mA cm^-2 when using this material as an anode and a cathode. This work provides an effective strategy to design and synthesize efficient, durable and anti-poisoning cobalt chalcogenide-based trifunctional electrocatalysts for the large-scale application of clean energy conversion devices.

N-doped carbon-coated Cu2O nanowire arrays on copper foam for rapid and stable water disinfection

High-speed, low-cost and long-term water disinfection method is important for us to away from waterborne diseases. Nanowires-modified electrodes can inactivate microorganisms under low energy consumption. However, small processing capacity remains a major obstacle for practical application. In this study, we coated N-doped carbon layer on Cu₂O NWs to improve the conductivity and stability for electrodes. Compared with Cu₂O, the work functions of Cu₂O-PANI structures is 3.623 eV, indicating the electrodes can prevent the recombination of electron-hole pairs and improve the carrier transport efficiency. In addition, Mulliken charge density showed that Cu₂O-PANI structure reduce the oxidation trend of Cu atom and improve the stability of electrodes. Besides, the Cu₂O NWs@NC electrodes showed excellent disinfection performance for E. coli and S. aureus, which can achieve 99.9% sterilizing rate under high flux (1200 mL min^-1). Under this condition, the electrodes can continuously treat 576 L wastewater, which is about 10-folds handling capacity than others. Moreover, the bactericidal mechanism is synergistic of electroporation and reactive oxygen species, and the main ROS were electrons, OH and O₂^-. Therefore, this electrodes has a great prospect for rapid and stable water treatment system.

Unveiling the advantages of an ultrathin N-doped carbon shell on self-supported tungsten phosphide nanowire arrays for the hydrogen evolution reaction experimentally and theoretically

Packaging electrocatalysts with carbon shells offers an opportunity to develop stable and effective hydrogen evolution reaction (HER) materials. Here, an ultrathin N-doped carbon-coated self-supported WP nanowire array (WP@NC NA) hybrid has been synthesized. Owing to the encapsulation of the ultrathin N-doped carbon shell on the WP surface, the as-prepared WP@NC NA hybrid exhibits enhanced physicochemical stability, more active sites, and superior conductivity compared with WP NA without carbon coating. Besides, density functional theory calculations demonstrate that the carbon shell can optimize the hydrogen adsorption step in the acidic HER, and simultaneously facilitate water physical adsorption, water dissociation, and hydroxyl group desorption steps during the alkaline HER. These findings demonstrate the intrinsic mechanism of how a carbon shell promotes the acidic and alkaline HER kinetics, and provide scientific guidance for the packaging design of promising carbon-encapsulating self-supported electrocatalysts.

Self-Assembly of Hausmannite Mn3O4 Triangular Structures on Cocosin Protein Scaffolds for High Energy Density Symmetric Supercapacitor Application

Recent advances in using biological scaffolds for nanoparticle synthesis have proven to be useful for preparing various nanostructures with uniform shape and size. Proteins are significant scaffolds for generating various nanostructures partly because of the presence of many functional groups to recognize different chemistries. In this endeavor, cocosin protein, an 11S allergen, is prepared from coconut fruit and employed as a potential scaffold for synthesizing Mn₃O₄ materials. The interaction between protein and manganese ions is studied in detail through isothermal calorimetric titration. At increased scaffold availability, the Mn₃O₄ material adopts the exact hexamer structure of the cocosin protein. The electrochemical supercapacitive properties of the cocosin-Mn₃O₄ material are found to have a high specific capacitance of 751.3 F g^-1 at 1 A g^-1 with cyclic stability (92% of capacitance retention after 5000 CV cycles) in a three-electrode configuration. The Mn₃O₄//Mn₃O₄ symmetric supercapacitor device delivers a specific capacitance of 203.8 F g^-1 at 1 A g^-1 and an outstanding energy and power density of 91.7 W h kg^-1 and 899.5 W kg^-1, respectively. These results show that cocosin-Mn₃O₄ could be considered a suitable electrode for energy storage applications. Moreover, the cocosin protein to be utilized as a novel scaffold in protein-nanomaterial chemistry could be useful for protein-assisted inorganic nanostructure synthesis in the future.

Hierarchical multi-yolk-shell copper oxide@copper-1, 3, 5-benzenetricarboxylate as an ultrastable anode for lithium ion batteries

The capacity attenuation of transition metal oxides (TMOs) and metal-organic frameworks (MOFs) is the obstacle for practical application in lithium ion batteries, due to the extensive volume variation upon charge/discharge cycles. Herein, a hierarchical composite material with copper oxide (CuO) multi-yolks and copper-1, 3, 5-benzenetricarboxylate (Cu-BTC) shell is synthesized by a facile method to study the effect of the hierarchical structure on the electrochemical performance. The porosity and pore volume of CuO@Cu-BTC composites are optimized to buffer the volume change and facilitate the infiltration of electrolytes by altering reaction conditions. The CuO@Cu-BTC (20 h) with the largest surface area and pore volume delivers an excellent reversible capacity of 780.7 mAh g^-1 at 200 mA g^-1 after 100 cycles, and ultrastable long-term performance with a specific capacity of 569 mAh g^-1 at a current density of 1000 mA g^-1 after 900 cycles. The corresponding full battery shows moderate capacity retention from 149.4 to 125.8 mAh g^-1 after 70 cycles, with a specific capacity retention of 84.2%, based on the mass of lithium iron phosphate (LiFePO₄) at 0.2 C (1 C = 170 mA g^-1). This strategy applies copper oxide as the metal source of the coordination compound, as well as the internal yolks, which can be extended to the in-situ construction of other hierarchical composites, providing a new avenue for practical application of TMOs and MOFs as anode materials.

Carbon-coated MoS1.5Te0.5 nanocables for efficient sodium-ion storage in non-aqueous dual-ion batteries

Sodium-based dual-ion batteries have received increased attention owing to their appealing cell voltage (i.e., >3 V) and cost-effective features. However, the development of high-performance anode materials is one of the key elements for exploiting this electrochemical energy storage system at practical levels. Here, we report a source-template synthetic strategy for fabricating a variety of nanowire-in-nanotube MS_xTe_y@C (M = Mo, W, Re) structures with an in situ-grown carbon film coating, termed as nanocables. Among the various materials prepared, the MoS_1.5Te_0.5@C nanocables are investigated as negative electrode active material in combination with expanded graphite at the positive electrode and NaPF₆-based non-aqueous electrolyte solutions for dual-ion storage in coin cell configuration. As a result, the dual-ion lab-scale cells demonstrate a prolonged cycling lifespan with 97% capacity retention over 1500 cycles and a reversible capacity of about 101 mAh g⁻¹ at specific capacities (based on the mass of the anode) of 1.0 A g⁻¹ and 5.0 A g⁻¹, respectively.

Sodium-based dual-ion batteries are promising electrochemical energy storage devices. Here, the authors report a source-template synthetic strategy to prepare carbon-coated MoS_1.5Te_0.5 nanocables and their use as anode active materials in Na-based dual ion cells.

Preparation and Electrochemical Performance of Three-Dimensional Vertically Aligned Graphene by Unidirectional Freezing Method

Three-dimensional vertically aligned graphene (3DVAG) was prepared by a unidirectional freezing method, and its electrochemical performances were evaluated as electrode materials for zinc−ion hybrid supercapacitors (ZHSCs). The prepared 3DVAG has a vertically ordered channel structure with a diameter of about 20−30 μm and a length stretching about hundreds of microns. Compared with the random structure of reduced graphene oxide (3DrGO), the vertical structure of 3DVAG in a three−electrode system showed higher specific capacitance, faster ion diffusion, and better rate performance. The specific capacitance of 3DVAG reached 66.6 F·g⁻¹ and the rate performance reached 92.2%. The constructed 3DVAG zinc−ion hybrid supercapacitor also showed excellent electrochemical performance. It showed good capacitance retention up to 94.6% after 3000 cycles at the current density of 2 A·g⁻¹.