Fast Ion Diffusion Research Articles

A Novel Triple Crosslinking Strategy on Carbon Nanofiber Membranes as Flexible Electrodes for Lithium-Ion Batteries.

In order to solve the problem of low electrical conductivity of carbon nanofiber membranes, a novel triple crosslinking strategy, including pre-rolling, solvent and chemical imidization crosslinking, was proposed to prepare carbon nanofiber membranes with a chemical crosslinking structure (CNMs-CC) derived from electrospinning polyimide nanofiber membranes. The physical-chemical characteristics of CNMs-CC as freestanding anodes for lithium-ion batteries were investigated in detail, along with carbon nanofiber membranes without a crosslinking structure (CNMs) and carbon nanofiber membranes with a physical crosslinking structure (CNMs-PC) as references. Further investigation demonstrates that CNMs-CC exhibits excellent rate performance and long cycle stability, compared with CNMs and CNMs-PC. At 50 mA g−1, CNMs-CC delivers a reversible specific capacity of 495 mAh g−1. In particular, the specific capacity of CNMs-CC is still as high as 290.87 mAh g−1 and maintains 201.38 mAh g−1 after 1000 cycles at a high current density of 1 A g−1. The excellent electrochemical performance of the CNMs-CC is attributed to the unique crosslinking structure derived from the novel triple crosslinking strategy, which imparts fast electron transfer and ion diffusion kinetics, as well as a stable structure that withstands repeated impacts of ions during charging and discharging process. Therefore, CNMs-CC shows great potential to be the freestanding electrodes applied in the field of flexible lithium-ion batteries and supercapacitors owing to the optimized structure strategy and improved properties.

Synthesis and characterization of Nb-doped strontium cobaltite@GQD electrodes for high performance supercapacitors

In this study, the fabrication and characterization of Nb-doped strontium cobaltite, SrCo0.9Nb0.1O3-δ (SCN), with a significant concentration of oxygen vacancies, as a charge storage material, prepared using sol-gel method, is reported. The results obtained show that the diffusion of oxygen ions is a rate limiting factor for charge storage. The perovskite material, niobium doped strontium cobalitite, on nano graphene sheets such as SCN@GQDs, has been prepared. The Graphene Quantum Dots (GQDs) have been synthesized by using a facile hydrothermal method. The morphology of SCN@GQDs was characterized by FESEM, and TEM. Additional characterization techniques such as PXRD, Raman Spectroscopy, FTIR, TGA/DTA, and BET were performed to observe the structure, porosity, functional groups, defects and thermal behavior of the material. The prepared SCN@GQDs act as an effective electrode material and exhibit high energy density. These SCN@GQD electrodes have been investigated for their electro-chemical properties. The specific capacitance of the synthesized perovskite materials, at 0.1 Ag−1 for supercapacitor, is higher than those of GQDs and SCN due to the improved conductivity, presence of oxygen vacancies and fast ion diffusion between the working electrodes and electrolyte. These properties of SCN@GQD perovskite material, with nanographene sheets, for boosting the capacity of electrodes, provide excellent opportunities for applications in supercapacitors. This perovskite material is superior in comparison to other candidates due to its larger oxygen vacancy concentration and higher oxygen-ion mobility.

Enhancing structural and cycle stability of Prussian blue cathode materials for calcium-ion batteries by introducing divalent Fe

Calcium-ion batteries (CIBs) have been of interest for rechargeable batteries due to their high energy density and fast ion diffusion in liquid electrolyte originated from the divalence and low charge/radius ratio of Ca ion. However, exploring high performance cathode materials for CIBs is very challenging. In this work, divalent Fe ions are introduced into copper hexacyanoferrate (CuHCF) to construct a new Prussian blue cathode material rich of Fe2+ by using K4Fe(CN)6 as the precursor instead of K3Fe(CN)6. The Fe2+ ions at low-spin state can improve the structural stability of CuHCF during Ca ions extraction and insertion processes effectively. It is found that the lattice parameter change of CuHCF is only 0.13 % during charge and discharge, much less than the CuHCF with Fe3+. X-ray absorption spectroscopy indicates that the charge compensation of CuHCF(Fe2+) is mainly contributed by Fe2+/Fe3+ redox couple. The octahedral distortion in CuHCF is also suppressed effectively. As a result, the CuHCF(Fe2+) cathode can deliver a reversible capacity of 54.5 mAh/g at 20 mA g−1 with a high capacity retention of 90.43 % after 1000 cycles.

Monodispersed FeS2 Electrocatalyst Anchored to Nitrogen‐Doped Carbon Host for Lithium–Sulfur Batteries

AbstractDespite their high theoretical energy density, lithium–sulfur (Li–S) batteries are hindered by practical challenges including sluggish conversion kinetics and shuttle effect of polysulfides. Here, a nitrogen‐doped continuous porous carbon (CPC) host anchoring monodispersed sub‐10 nm FeS2 nanoclusters (CPC@FeS2) is reported as an efficient catalytic matrix for sulfur cathode. This host shows strong adsorption of polysulfides, promising the inhibition of polysulfide shuttle and the promoted initial stage of catalytic conversion process. Moreover, fast lithium ion (Li‐ion) diffusion and accelerated solid–solid conversion kinetics of Li2S2 to Li2S on CPC@FeS2 host guarantee boosted electrochemical kinetics for conversion process of sulfur species in Li–S cell, which gives a high utilization of sulfur under practical conditions of high loading and low electrolyte/sulfur (E/S) ratio. Therefore, the surfur cathode (S/CPC@FeS2) delivers a high specific capacity of 1459 mAh g−1 at 0.1 C, a stable cycling over 900 cycles with ultralow fading rate of 0.043% per cycle, and an enhanced rate capability compared with cathode only using carbon host. Further demonstration of this cathode in Li–S pouch cell shows a practical energy density of 372 Wh kg−1 with a sulfur loading of 7.1 mg cm−2 and an E/S ratio of 4 µL mg−1.

Nanocomposite of Conducting Polymer and Li Metal for Rechargeable High Energy Density Batteries.

The structure and electrochemical performance of lithium (Li) metal degrade quickly owing to its hostless nature and high reactivity, hindering its practical application in rechargeable high energy density batteries. In order to enhance the electrochemical reversibility of metallic Li, we designed a Li/Li2S-poly(acrylonitrile) (LSPAN) composite foil via a facile mechanical kneading approach using metallic Li and sulfurized poly(acrylonitrile) as the raw materials. The uniformly dispersed Li2S-poly(acrylonitrile) (Li2S-PAN) in a metallic Li matrix buffered the volume change on cycling, and its high Li ion conductivity enabled fast Li ion diffusion behavior of the composite electrode. As expected, the LSPAN electrode showed reduced voltage polarization, enhanced rate capability, and prolonged cycle life compared with the pure Li electrode. It exhibited stable cycling for 600 h with a symmetric cell configuration at 1 mA cm-2 and 1 mA h cm-2, far outperforming the pure metallic Li counterpart (400 h). Also, the LiCoO2||LSPAN full cells with a cathode mass loading of ∼16 mg cm-2 worked stably for 100 cycles at 0.5 C with a high capacity retention of 96.5%, while the LiCoO2||Li full cells quickly failed within only 50 cycles.

Efficient charge storage by ZnCo2S4 nanoflakes@MgCo2O4 nanorods composite in Mg2+/Zn2+/K+ conducting electrolytes

Heretofore unreported, a unique binder free composite cathode of zinc cobalt sulfide nanoflakes (NFs) and magnesium cobaltite nanorods (NRs) (ZnCo2S4@MgCo2O4) is presented and its potential for efficient energy storage is realized in terms of (1) a high electrical conductivity of ~0.7 mS cm−1 imparted by the mixed-valence states of Co2+/Co3+, (2) the mesoporous structure of the MgCo2O4 NRs enabling fast ion-diffusion and (3) the 3D ZnCo2S4 flakes with large exposed facets that allow abundant electrolyte-electroactive site-interactions. These factors cumulatively result in a high specific capacitance (SC) of 609 F g−1 (at 1.25 A g−1), Emax of 217 Wh kg−1 and a Pmax of 8 kW kg−1 over a voltage window of 1.6 V along with a cycle life of 10,000 cycles with 98 % SC retention for the ZnCo2S4@MgCo2O4//AC asymmetric supercapacitor (ASC) with KOH as the electrolyte. These performance metrics are superior to those reported in literature for similar oxides/chalcogenides. The electrolyte's role in controlling the redox-behaviour of the ASC is also assessed by using four different uni-molar electrolytes that obey the following order: KOH > Mg(OH)2 > MgCl2 > ZnCl2, in terms of their ionic conductivities (σ: 189, 84, 83 and 58 mS cm−1), cation transport number (t+: 0.85, 0.83, 0.75 and 0.57) and SCs (609, 315, 208, 100 F g−1 at 1.25 A g−1) for the corresponding ASCs. With the KOH electrolyte, a dominant contribution from diffusional transport (68 %) relative to the capacitive double layer storage (32 %) (at 10 mV s−1) is ascertained which confirms the ZnCo2S4@MgCo2O4 composite's ability to exhibit facile Faradaic reactions for charge storage, thereby aligning with the morphological and spinel structure benefits. A green-LED-illumination with a 3S(series)-configuration encompassing three-fully-charged ASCs, further validates this configuration's applicability for niche applications in consumer-electronic-devices.

Hydrophobic lithium diffusion-accelerating layers enables long-life moisture-resistant metallic lithium anodes in practical harsh environments

Rechargeable lithium metal batteries are deemed as "Holy Grail" in high energy storage systems. However, lithium anode suffers from Li dendrite growth resulted from sluggish ion diffusion and random spatial deposition. Meanwhile, the practical harsh anhydrous and oxygen-free assembly-environmental conditions also challenge their wide assembly and application. Herein, a universal hydrophobic lithium diffusion-accelerated artificial layer is proposed on Li surface to resist moisture corrosion, realizing uniform lithium diffusion/plating morphology in practical harsh environments. As a demo, the robust moist-air-stable polymer-LiF-alloy hybrid hierarchical layer is fabricated (MASPLA-Li), inheriting robust interfacial stability towards moist air as high as 50 RH%, which are comprehensively revealed by X-ray spectroscopy, electronic microscopy, time-of-flight second-ionic mass spectroscopy, and sum frequency generation spectroscopy. Systematic investigations of being moist air exposure treatment for different time are performed, and the moist-air-exposed MASPLA-Li anode reserves fast ion diffusion, extends the longer plating lifespan over 600 h with overpotential of ∼ 10 mV, and displays much higher Coulombic efficiency of 99.3%, significantly better than the little literature reports. Coupling with LiFePO4 and sulfur cathodes, the so-fabricated full cells also show remarkably improved utilization, cycling stability, and capacity retention at 5 C, showing the promising future in the practical application.

Ultrathin δ-MnO2 nanosheets branched onto N-doped carbon nanotubes as binder-free cathode electrodes for aqueous zinc-ion batteries with a high areal capacity

Manganese-based materials have been considered as promising electrode materials for aqueous zinc-ion batteries (ZIBs). However, the development of manganese-based materials is seriously restricted by their low electrical conductivity and sluggish reaction kinetics. In the present work, ultrathin birnessite-type δ-MnO 2 nanosheets branched onto N-doped carbon nanotubes grown on carbon cloth substrate (CC/NCNTs/δ-MnO 2 ) have been rational synthesized as a binder-free cathode electrode for aqueous ZIBs. The CC/NCNTs/δ-MnO 2 cathode possesses the desired merits including high electrical conductivity, large specific surface area, abundant active sites, fast ion diffusion, good structural stability and free of any polymer binders. When evaluated as a binder-free cathode electrode for aqueous ZIBs, the CC/NCNTs/δ-MnO 2 exhibits high areal capacity and energy density of 1.95 mAh cm −2 and 2.56 mWh cm −2 at a current density of 0.4 mA cm −2 , respectively, as well as decent rate capability and cycling stability. This work could provide an effective method to construct high-performance binder-free cathode electrodes for aqueous ZIBs. Ultrathin birnessite-type δ-MnO 2 nanosheets branched onto N-doped carbon nanotubes grown on carbon cloth substrate (CC/NCNTs/δ-MnO 2 ) have been rational synthesized, which exhibit excellent performance as binder-free cathode electrodes for aqueous zinc-ion batteries. • Ultrathin δ-MnO 2 nanosheets branched onto N-doped carbon nanotubes grown on carbon cloth are synthesized. • The CC/NCNTs/δ-MnO 2 is directly used as a binder-free cathode for aqueous zinc-ion batteries. • The CC/NCNTs/δ-MnO 2 possesses desired morphological, structural and compositional merits. • The CC/NCNTs/δ-MnO 2 exhibits a high areal capacity of 1.95 mAh cm –2 .

Sustainable Self-Cleaning Evaporators for Highly Efficient Solar Desalination Using a Highly Elastic Sponge-like Hydrogel.

Interfacial evaporation using light-absorbing hydrogels offers efficient solar evaporation performance under natural sunlight, ensuring an affordable clean water supply. However, achieving light-absorbing hydrogels with durable and efficient utilization is still a challenge due to inevitable salt accumulation, a difficult-to-control surface morphology, and poor mechanical properties on the surfaces of hydrogel-based evaporators. In this work, a photothermal sponge-like hydrogel with a 3D interconnected porous structure was constructed using low-cost activated carbon as a photothermal material, as well as a double-network polymer chain as the basic skeleton using a simple foaming polymerization strategy. The sponge-like hydrogel evaporator showed tailored surface topography, adequate water transport, excellent elasticity and toughness, good salt rejection, and thermal localization properties. Under the irradiation of simulated sunlight (1.0 kW/m2), a high evaporation rate of 2.33 kg·m-2·h-1 was achieved. Furthermore, efficient salt self-cleaning behavior was achieved due to the fast ion diffusion within the 3D interconnected porous structures. Even in highly concentrated brine of 15 wt %, continuous and efficient water evaporation was still achieved. The excellent evaporation and salt rejection properties of this photothermal sponge-like hydrogel indicated its promising long-term sustainable utilization in seawater desalination.

In Situ Integrating Highly Ionic Conductive LDH‐Array@PVA Gel Electrolyte and MXene/Zn Anode for Dendrite‐Free High‐Performance Flexible Zn–Air Batteries

AbstractLow interfacial ion transfer kinetics and structure instability of solid‐state electrolytes are the bottleneck which seriously limits the working life and energy density of flexible zinc–air batteries (ZABs). Herein, an optimized electrode–electrolyte integrated MXene/Zn‐layered double hydroxides (LDH)‐array@PVA structure is developed via an electrochemical Zn deposition, in situ LDH growth, polymer infiltration, and crosslinking route, integrating anode and gel polymer electrolyte (GPE) for high‐performance flexible ZABs. The highly orientated hydrophilic CoNi‐LDH arrays sufficiently crosslink with poly(vinyl alcohol) (PVA) chains, which effectively decreases the crystallinity degree of the PVA polymer and provides fast ionic diffusion channels to reduce the ionic transport barrier, endowing LDH‐array@PVA GPE with significantly improved ionic conductivity, water retention capability, and mechanical flexibility. Moreover, the optimized anode‐GPE integrated interface of MXene/Zn‐LDH‐array@PVA demonstrates excellent interfacial compatibility and stability, effectively reduces the interfacial impedance, and promotes the interfacial ionic transfer kinetics, enhancing a uniform zinc deposition without dendrite formation. The optimized ionic transfer kinetics and stable anode‐GPE integrated interface bring the MXene/Zn‐LDH‐array@PVA‐based flexible ZAB a long cycling life up to 50 h, and a high power density of 92.3 mW cm−2. The rationally designed in situ crosslinking and integration strategies provide enlightening pathways for the design of high‐performance flexible ZABs.

Bi2O2S nanosheets anchored on reduced graphene oxides as superior anodes for aqueous rechargeable alkaline batteries

To achieve high-performance aqueous rechargeable alkaline batteries (ARABs), durable and high-rate anode materials should be developed. Bi-based materials have always been considered as promising anodes due to their enormous capacity, adequate negative operating voltage range, and three-electron redox characteristics. Nonetheless, the poor kinetics and low cycling stability of bi-based materials have severely limited their applications for ARABs. Here inspired by the unique structural characteristic of two-dimensional (2D) materials with a fast ion diffusion channel and relatively robust structure, 2D/2D Bi2O2S@rGO nanosheets were synthesized using a one-step hydrothermal process as the anode material for ARABs. At a current density of 1 A g−1, the as-optimized anodes exhibit a high specific capacity of 250.51 mAh g−1. Using Bi2O2S@rGO NSs as the anode and (NiCo)9S8 as the cathode, the full cell exhibit a high energy density of 82.91 W h kg−1, a high power density of 7.59 kW kg−1, and excellent cycling stability, with a capacity retention rate of 92.74% after 5,000 cycles. This work could open up a way for environmentally friendly and high-performance anode materials.

The balanced improvement of electrochemical performance of cobalt disulfide anode material for sodium-ion batteries by constructing reduced graphene oxide conductive network based on “bucket principle”

Recently, cobalt disulfide (CoS2) as a promising candidate of anode material for sodium ion batteries is paid much attention because of the high theoretical capacity. However, the poor rate capability and cycling stability are still the barriers to the large-scale application of CoS2 resulting from its low intrinsic electronic conductivity and severe volume change during the sodiation and desodiation process. In order to address above issues, herein, reduced graphene oxide (rGO) is introduced to define the CoS2 nanoparticles growth in the solvothermal synthesis process and construct the three-dimensional conductive network, which can tune the electronic conductivity, ionic diffusivity and inhibiting effect of volume change of CoS2/rGO composites anode material. It is found that these factors show different trends accompanying with the increase of rGO doping amount. The compact rGO network is beneficial to improve the electronic conductivity and hinder the volume change of the composites, however, it maybe does harm to the fast sodium ion diffusion. And when it becomes sparse, the opposite is true. Hence, a balanced strategy based on “bucket principle” is proposed to achieve the balanced enhancement of the rate capability and cycling performance. The optimized CoS2/rGO electrode acquires a superior performance, possessing 675.8 mAh g−1 at 0.1 A g−1 and 471.1 mAh g−1 at 2.0 A g−1 with the capacity retention of 69.7%, and it still has 272.5 mAh g−1 after 500 cycles at 1.0 A g−1 in the voltage range of 0.01–3.0 V. This can be attributed to the improvement of charge transfer process and the excellent accommodating capacity of volume change provided by rGO conductive network. This balanced strategy can also be used to synthesize high-performance composite materials in other fields.

Effects of Interlayer Properties on Electrochemical Ion Intercalation and Electrosorption in Layered and 2D Electrode Materials

The kinetics of electrochemical intercalation and electrosorption processes are often limited by the solid-state diffusion of ions inside the lattice of the host material. While some of these limitations can be mitigated by nanostructuring of the electrode material, there is a large interest in the electrochemical energy storage community to find materials with structural motifs that allow for intrinsically fast ion diffusion, even in bulk-sized particles.In this presentation, it will be highlighted how interlayer properties, such as interlayer distance and interlayer chemistry, affect electrochemical ion intercalation and electrosorption processes in layered host materials. Using the examples of hydrogen titanates1 and Ti3C2Tx MXenes2, it is demonstrated that the presence of structural interlayer atoms or molecules can increase the accessibility of ions to the interlayer space. In the model layered host material TiS2, it is shown that increased interlayer spacing and reduced deformation during ion intercalation can lead to a change from diffusion-limited to non-diffusion limited (or pseudocapacitive) charge storage behavior,3 providing some of the most compelling experimental evidence of the intimate relationship between deformation, interlayer distance, and intercalation kinetics in layered host materials.This contribution will emphasize the importance of interlayer properties of layered and 2D materials for electrochemical ion intercalation and electrosorption processes and provide perspectives and design strategies for next generation ion insertion hosts with fast kinetics for high power energy storage. Fleischmann, S. et al. Interlayer separation in hydrogen titanates enables electrochemical proton intercalation. J. Mater. Chem. A 8, 412–421 (2020).Liang, K. et al. Engineering the Interlayer Spacing by Pre-Intercalation for High Performance Supercapacitor MXene Electrodes in Room Temperature Ionic Liquid. Adv. Funct. Mater. 31, 2104007 (2021).Fleischmann, S., Shao, H., Taberna, P.-L., Rozier, P. & Simon, P. Electrochemically Induced Deformation Determines the Rate of Lithium Intercalation in Bulk TiS2. ACS Energy Lett. 6, 4173–4178 (2021).

Elemental Two-Dimensional Materials for Li/Na-Ion Battery Anode Applications.

Two-dimensional (2D) nanostructure is currently the subject in the fields of new energy storage and devices. During the past years, a broad range of 2D materials represented by graphene have been developed and endow with excellent electrochemical properties. Among them, elemental 2D materials (Xenes) are an emerged material family for Li/Na-ion battery (LIB/SIB) anodes. Compared with other 2D materials and bulk materials, Xenes may exhibit some great superiorities for Li/Na storage, including excellent conductivity, fast ion diffusion and large active sites exposure. In this review, we provide a systematic summary of the recent progress and achievements of Xenes as well as their applications in LIBs/SIBs. The broad categorization of Xenes from group IIIA to VIA has been concisely outlined, and the related details in syntheses, structures and Li/Na-ion storage properties are reviewed. Further, the latest research progress of Xenes in Li/Na ion batteries are summarized, together with mechanism discussions. Finally, the challenges and prospects of Xenes applied to Li/Na ion battery are proposed based on its current developments.

Fast ion diffusion alloy layer facilitating 3D mesh substrate for dendrite-free zinc-ion hybrid capacitors

Although aqueous zinc ion hybrid capacitors have advantageous integration of batteries and supercapacitors, they still suffer from the inherent problems of dendrite growth and interfacial side reactions on Zn anodes. Herein, a universal fast zinc-ion diffusion layer on a three-dimensional (3D) mesh structure model is demonstrated to effectively improve Zn plating/stripping reversibility. The fast ion diffusion alloy layer accelerates the Zn2+ migration in an orderly manner to homogenize Zn2+ flux and overcomes the defects of the commercial mesh substrate, effectively avoiding dendrite growth and side reactions. Consequently, the proof-of-concept silver-zinc alloy modified stainless steel mesh delivers superb reversibility with the high coulombic efficiency over 99.4% at 4 mA cm−2 after 1600 cycles and excellent reliability of over 830 h at 1 mA cm−2, Its feasibility is also evidenced in commercial zinc ion hybrid capacitors with activated carbon as the cathode. This work enriches the fundamental comprehension of fast zinc-ion diffusion layer combined with a 3D substrate on the Zn deposition and opens a universal approach to design advanced host for Zn electrodes in zinc ion hybrid capacitors.

Hydrothermal production of low-cost CeNi2S4-reduced graphene oxide composites as an efficient counter electrode for high performance dye-sensitized solar cells

Dye sensitized solar cell (DSSC) technology could become a low-cost solution for solar energy harvesting if the use of expensive dyes and Pt can be avoided. This work reports the development of a novel nanohybrid based on CeNi2S4 nanotubes embedded on sheets of reduced graphene oxide (RGO), which can serve as excellent counter electrode for DSSC showing great promise to replace Pt. The structural and morphological characterization of the nanocomposite synthesized using a simple one step hydrothermal method revealed well defined crystalline nanotubes of CeNi2S4 (with length 190 nm and diameter 8.54 nm) uniformly embedded on the surfaces of the RGO sheets (∼2.65 μm in size). The morphology and size of the nanotubes were found to be dependent on the duration of the hydrothermal reaction. The optimized CeNi2S4/RGO nanohybrid CE when used as counter electrode in DSSC, photo conversion efficiency as high as 9.21 ± 0.03 % was recorded, a value almost equal to that obtained from the DSSC fabricated with Pt as counter electrode and much higher than that with bare CeNi2S4 justifying its potential use in Pt-free DSSC. The improved performance of the electrode have been attributed to the hierarchical nanohybrid structure consisting of catalytically active 1D CeNi2S4 nanotubes embedded on electrically conducting 2D RGO sheets that provides fast ion diffusion pathways, large accessible surface area and good chemical and thermal stability.

Facile Electrodeposition of NiCo2O4 Nanosheets on Porous Carbonized Wood for Wood-Derived Asymmetric Supercapacitors.

Multichannel-porous carbon derived from wood can serve as a conductive substrate for fast charge transfer and ion diffusion, supporting the high-theory capacitance of pseudocapacitive materials. Herein, NiCo2O4 nanosheets, which are hierarchically porous, anchored on the surface of carbonized wood via electrodeposition for free-binder high-performance supercapacitor electrode materials, were proposed. Benefiting from the effectively alleviated NiCo2O4 nanosheets accumulation and sufficient active surface area for redox reaction, a N-doped wood-derived porous carbon-NiCo2O4 nanosheet hybrid material (NCNS–NCW) electrode exhibited a specific electric capacity of 1730 F g−1 at 1 A g−1 in 1 mol L−1 KOH and splendid electrochemical firmness with 80% capacitance retention after cycles. Furthermore, an all-wood-based asymmetric supercapacitor based on NCNS–NCW//NCW was assembled and a high energy density of 56.1 Wh kg−1 at a watt density of 349 W kg−1 was achieved. Due to the great electrochemical performance of NCNS–NCW, we expect it to be used as an electrode material with great promise for energy storage equipment.

Hierarchical layer to layer of ternary heterostructure: Nanograin nickel carbonate embedded layered NiMnO 3 ‐rGO‐Co 3 O 4 composite array as a high‐performance electrode for hybrid supercapacitors

Heterostructured metallic electrode materials fabricated by altering the structurally engineered morphologies are promising in ameliorating electrodes' functionality in energy storage applications. Effective and novel double-shell sandwich-like NiCO3/NiMnO3-rGO-Co3O4 (Ni-NMO-rGO-CoO) nanoflake array (NFA) heterostructures were prepared on highly conducting 3D Ni foam using a two-step hydrothermal process. rGO wrapping on the NiCO3 embedded NiMnO3 (Ni-NMO) nanocomposite flakes improved the cycling stability and avoided volume expansion by acting as an interlayer. The surface decorated Co3O4 nanograins showed a uniform distribution over the rGO wrapped Ni-NMO and facilitated the pathways for fast ion diffusion kinetics to enhance the specific capacity of the electrode. The layer to layered Ni-NMO-rGO-CoO NFA electrode yielded an ascendant specific capacity of 188.8 mA h g−1 (3.9 F cm−2) at 1 mA g−1. The fabricated all-solid-state Ni-NMO-rGO-CoO//AC hybrid supercapacitors (HSCs) showed a superior energy density of 57.2 W h kg−1 at 472.2 W kg−1 with 97.7% capacitance retention after 10 000 cycles. The fabricated HSCs have potential applications in portable electronics. The Ni-NMO-rGO-CoO NFA ternary layered architecture offers a promising approach for fabricating high-performance hierarchical composite array electrodes for next-generation energy storage devices.

Bifunctional design of cerium-based metal-organic framework-808 membrane modified separator for polysulfide shuttling and dendrite growth inhibition in lithium-sulfur batteries

Lithium-sulfur battery is perceived as one promising next generation rechargeable battery system, in view of its high theoretical specific capacity and energy density. However, the “shuttle effect” of polysulfides and the uncontrolled growth of lithium dendrites significantly obstruct its practical application. Herein, a bifunctional separator with double-sided modification is developed to simultaneously resolve these issues, which is constructed by growing continuous cerium-based metal-organic framework-808 (Ce-MOF-808) membranes on both sides of the commercial polypropylene (PP) separator through a simple in-situ growth method. On the cathode side, the Ce-MOF-808 membrane can play multiple roles of adsorption, selective sieving and catalytic conversion towards polysulfides, thereby effectively inhibiting their shuttle effect. On the anode side, the highly uniform pore distribution and polar groups of this MOF membrane ensure the fast and homogenous diffusion of lithium ions, endowing a stable lithium nucleation and growth in the cycles. Consequently, the Ce-MOF-808/PP separator exhibits a high initial specific capacity of 954.7 mAh g−1 under 1 C with a very limited capacity fading of 0.025% in 500 cycles, and an outstanding rate capability. Moreover, the separator also ensures the stable cycling of the battery at raised sulfur loading and lean-electrolyte conditions.

Constructing titanium carbide MXene/reduced graphene oxide superlattice heterostructure via electrostatic self-assembly for high-performance capacitive deionization

Capacitive deionization has attracted wide concern on accountof its high energy efficiency, low manufacturing cost and environmental friendliness. Nevertheless, the development of capacitive deionization is still impeded because of the scarcity of suitable electrode materials with superior performance. Herein, we successfully prepared the two-dimensional (2D) titanium carbide (Ti3C2Tx) MXene/ reduced graphene oxide (rGO) superlattice heterostructure by a facile electrostatic self-assembly strategy and systematically investigated its performance as capacitive deionized electrode materials. The unique 2D/2D superlattice heterostructure not only effectively alleviates the self-stacking problem of Ti3C2Tx MXene nanosheets, but also endows the heterostructure with superior conductivity and fast ion diffusion rate. As a result, the MXene/rGO superlattice heterostructure exhibits an outstanding salt (Na+) adsorption capacity (48 mg g−1) at 1.2 V significantly superior to pristine Ti3C2Tx MXene nanosheets, along with outstanding long-term cycling performance. Furthermore, the mechanism involved was elucidated through comprehensive characterizations. Therefore, this study offers a new pathway for designing high-performance electrode materials for capacitive deionization.