Delving into the dissimilarities in electrochemical performance and underlying mechanisms for sodium and potassium ion storage in N-doped carbon-encapsulated metallic Cu_(2)Se nanocubes

The large volumetric variations experienced by metal selenides within conversion reaction result in inferior rate capability and cycling stability,ultimately hindering the achievement of superior electrochemical performance.Herein,metallic Cu_(2)Se encapsulated with N-doped carbon(Cu_(2)Se@NC)was prepared using Cu_(2)O nanocubes as templates through a combination of dopamine polymerization and hightemperature selenization.The unique nanocubic structure and uniform N-doped carbon coating could shorten the ion transport distance,accelerate electron/charge diffusion,and suppress volume variation,ultimately ensuring Cu_(2)Se@NC with excellent electrochemical performance in sodium ion batteries(SIBs)and potassium ion batteries(PIBs).The composite exhibited excellent rate performance(187.7 mA h g^(-1)at 50 A g^(-1)in SIBs and 179.4 mA h g^(-1)at 5 A g^(-1)in PIBs)and cyclic stability(246,8 mA h g^(-1)at 10 A g^(-1)in SIBs over 2500 cycles).The reaction mechanism of intercalation combined with conversion in both SIBs and PIBs was disclosed by in situ X-ray diffraction(XRD)and ex situ transmission electron microscope(TEM).In particular,the final products in PIBs of K_(2)Se and K_(2)Se_(3)species were determined after discharging,which is different from that in SIBs with the final species of Na_(2)Se.The density functional theory calculation showed that carbon induces strong coupling and charge interactions with Cu_(2)Se,leading to the introduction of built-in electric field on heterojunction to improve electron mobility.Significantly,the theoretical calculations discovered that the underlying cause for the relatively superior rate capability in SIBs to that in PIBs is the agile Na~+diffusion with low energy barrier and moderate adsorption energy.These findings offer theoretical support for in-depth understanding of the performance differences of Cu-based materials in different ion storage systems.

Constructing Carbon Nanobubbles with Boron Doping as Advanced Anode for Realizing Unprecedently Ultrafast Potassium Ion Storage

Carbonaceous material with favorable K^(+)intercalation feature is considered as a compelling anode for potassium-ion batteries(PIBs).However,the inferior rate performance and cycling stability impede their large-scale application.Here,a facile template method is utilized to synthesize boron doping carbon nanobubbles(BCNBs).The incorporation of boron into the carbon structure introduces abundant defective sites and improves conductivity,facilitating both the intercalation-controlled and capacitivecontrolled capacities.Moreover,theoretical calculation proves that boron doping can effectively improve the conductivity and facilitate electrochemical reversibility in PIBs.Correspondingly,the designed BCNBs anode delivers a high specific capacity(464 mAh g^(-1)at 0.05 A g^(-1))with an extraordinary rate performance(85.7 mAh g^(-1)at 50 A g^(-1)),and retains a considerable capacity retention(95.2%relative to the 100th charge after 2000 cycles).Besides,the strategy of pre-forming stable artificial inorganic solid electrolyte interface effectively realizes high initial coulombic efficiency of 79.0%for BCNBs.Impressively,a dual-carbon potassium-ion capacitor coupling BCNBs anode displays a high energy density(177.8 Wh kg^(-1)).This work not only shows great potential for utilizing heteroatom-doping strategy to boost the potassium ion storage but also paves the way for designing high-energy/power storage devices.

Sulfur and nitrogen codoped cyanoethyl cellulose-derived carbon with superior gravimetric and volumetric capacity for potassium ion storage

We fabricated sulfur and nitrogen codoped cyanoethyl cellulose-derived carbons(SNCCs)with state-of-the-art electrochemical performance for potassium ion battery(PIB)and potassium ion capacitor(PIC)anodes.At 0.2,0.5,1,2,5,and 10 A g−1,the SNCC shows reversible capacities of 369,328,249,208,150,and 121 mA h g−1,respectively.Due to a high packing density of 1.01 g cm^(−3),the volumetric capacities are also uniquely favorable,being 373,331,251,210,151,and 122 mA h cm^(−3)at these currents,respectively.SNCC also shows promising initial Coulombic efficiency of 69.0%and extended cycling stability with 99.8%capacity retention after 1000 cycles.As proof of principle,an SNCC-based PIC is fabricated and tested,achieving 94.3Wh kg^(−1)at 237.5Wkg^(−1)and sustaining over 6000 cycles at 30 A g−1 with 84.5%retention.The internal structure of S and N codoped SNCC is based on highly dilated and defective graphene sheets arranged into nanometer-scale walls.Using a baseline S-free carbon for comparison(termed NCC),the role of S doping and the resultant dilated structure was elucidated.According to galvanostatic intermittent titration technique and electrochemical impedance spectroscopy analyses,as well as COMSOL simulations,this structure promotes rapid solid-state diffusion of potassium ions and a solid electrolyte interphase that is stable during cycling.X-ray diffraction was used to probe the ion storage mechanisms in SNCC,establishing the role of reversible potassium intercalation and the presence of KC36,KC24,and KC8 phases at low voltages.

Reduced graphene oxide doping flower-like Fe_(7)S_(8) nanosheets for high performance potassium ion storage

Finding easy-to-operate strategy to obtain anode material with well-designed structure and excellent electrochemical performance is necessary to promote the development of the future potassium-ion batteries(PIBs).In this work,we synthesized reduced graphene oxide doping flower-like Fe_(7)S_(8) nanosheets electrode materials using one-step hydrothermal strategy.The rGO@Fe_(7)S_(8) composite is composed of homogeneous Fe_(7)S_(8) and reduced graphene oxide thin nanosheets.This unique structure not only promotes the penetration of electrolyte and increases the conductive of the pure Fe_(7)S_(8) electrode materials,but also relieves the volume expansion of K^(+) during charge/discharge process.When applied this interesting anode electrode for PIBs,the rGO@Fe_(7)S_(8) exhibits excellent electrochemical performance.It delivers a high reversible specific capacity of 445 mAh g^(-1) at 50 mA g^(-1),excellent rate performance(284 mAhg^(-1)at 500 mA g^(-1) and 237 mAh g^(-1) at 1000 mA g^(-1)),and a high cycling stability at 100 mA g^(-1)(maintained 355 mAh g^(-1) after 300 cycles).

Engineering electronic structures of titanium vacancies in Ti_(1-x)O_(2)nanosheets enables enhanced Li-ion and Na-ion storage

Up to now,three kinds of ion-storage mechanisms are summarized towards anode materials in lithium/sodium-ion batteries,but they have low capacity and poor cyclic performance.Therefore,it is necessary to develop a new approach to optimize ion storage.Herein,we report an adsorption/desorption storage route through engineering electronic structure of cation-deficient Ti_(1-x)O_(2)nanosheets.Ti_(1-x)O_(2)nanosheets indeed exhibit higher capacity(332.1 mA h g^(-1)vs.137.7 mA h g^(-1)for LIBs,195.7 mA h g^(-1)vs.111 mA h g^(-1)for SIBs),and more stable cyclic performance(296 mA h g^(-1)vs.99 mA h g^(-1)for LIBs,178.1 mA h g^(-1)vs.80.2 mA h g^(-1)for SIBs after 100 cycles)at 0.1 A g^(-1)than TiO_(2)nanosheets.Kinetics analysis and density functional theory(DFT)calculations reveal that electronic structures of vacancy within Ti_(1-x)O_(2) nanosheets encourage a novel adsorption-desorption storage route.These results highlight the benefits of the engineered electronic structures within electrode material and implement novel ion-storage mechanism towards broad energy storage applications.

Chemical interaction motivated structure design of layered metal carbonate hydroxide/MXene composites for fast and durable lithium ion storage

Rational architecture design has turned out to be an effective strategy in improving the electrochemical performance of electrode materials for batteries.However,an elaborate structure that could simultaneously endow active materials with promoted reaction reversibility,accelerated kinetic and restricted volume change still remains a huge challenge.Herein,a novel chemical interaction motivated structure design strategy has been proposed,and a chemically bonded Co(CO_(3))_(0.5)OH·0.11 H_(2)O@MXene(CoCH@MXene)layered-composite was fabricated for the first time.In such a composite,the chemical interaction between Co^(2+)and MXene drives the growth of smaller-sized CoCH crystals and the subsequent formation of interwoven CoCH wires sandwiched in-between MXene nanosheets.This unique layered structure not only encourages charge transfer for faster reaction dynamics,but buffers the volume change of CoCH during lithiation-delithiation process,owing to the confined crystal growth between conductive MXene layers with the help of chemical bonding.Besides,the sandwiched interwoven CoCH wires also prevent the stacking of MXene layers,further conducive to the electrochemical performance of the composite.As a result,the as-prepared CoCH@MXene anode demonstrates a high reversible capacity(903.1 mAh g^(-1)at 100 mA g^(-1))and excellent cycling stability(maintains 733.6 mAh g^(-1)at1000 mA g^(-1)after 500 cycles)for lithium ion batteries.This work highlights a novel concept of layerby-layer chemical interaction motivated architecture design for futuristic high performance electrode materials in energy storage systems.

Embedding amorphous MoS_(x)within hierarchical porous carbon by facile one-pot synthesis for superior sodium ion storage

The design of anode materials with a high specific capacity,high cyclic stability,and superior rate performance is required for the practical applications of sodium-ion batteries(SIBs).In this regard,we introduce in this work a facile,low-cost and scalable method for the synthesis of nanocomposites of amorphous molybdenum sulfide(a-MoS_(x))and hierarchical porous carbon and have systematically investigated their performance for sodium ion storage.In the synthesis,ammonium molybdate tetrahydrate and thioacetamide are used as molybdenum and sulfur sources,respectively,with abundant corn starch as the carbon source and KOH as an activation agent.A simple pyrolysis of their mixtures leads to the formation of nanocomposites with a-MoS_(x)embedded within a hierarchical porous carbon(MoS_(x)@HPC),which are featured with a high surface area of up to 518.4 m^(2) g^(-1)and hierarchical pores ranging from micropores to macropores.It has also been shown that the annealing of MoS_(x)@HPC results in the formation of crystalline MoS_(2)nanosheets anchored in the hierarchical porous carbon matrix(MoS_(2)@HPC).The as-prepared nanocomposite MoS_(x)@HPC1 at an optimum carbon content of 32 wt%delivers a high specific sodium storage capacity of 599 mAh g^(-1)at 0.2 A g^(-1)and a high-rate performa nce with a retained capacity of 289 mAh g^(-1)at 5 A g^(-1).A comparison of the electrochemical performances of MoS_(x)@HPC and MoS_(2)@HPC demonstrates the superior specific capacity,rate performance,and charge transfer kinetics of the former,highlighting the unique advantageous role of amorphous MoS_(x)relative to crystalline MoS_(2).

Redox Charge Transfer Kinetics and Reversibility of VO_(2) in Aqueous and Non-Aqueous Electrolytes of Na-Ion Storage

The deep understanding about the electrochemical behavior of the nanostructured electrode in electrolytes provides crucial insights for the rational design of electrode for sodium(Na)-ion storage system(NIS).Here,we report redox charge transfer kinetics and reversibility of VO_(2)(B) nanorod electrodes in both aqueous and organic electrolytes for NIS.The assynthesized VO_(2)(B) nanorods show the reversible redox reaction with the higher specific and rate capacitances at high current density in aqueous electrolytes than in organic electrolytes.Temperature-dependent impedance measurements demonstrate the more facile interfacial charge transfer of Na ions into VO_(2)(B) nanorods in aqueous electrolytes.The reversible evolution in oxidation state and chemical composition of VO_(2)(B) nanorods is observed in aqueous electrolytes,as confirmed by ex situ XRD and ex situ X-ray photoelectron spectroscopy analyses.Given by the facile and reversible pseudocapacitive feature,the electrochemical performances of VO_(2)(B) nanorods are further improved by constructing the hierarchical structure of the reduced graphene oxide-VO_(2) composite for aqueous Na+ion storage.

Layered coordination polymer with two-dimensional covalent bismuth-organic networks:Semiconductor and lithium ion storage

Single crystals of a bismuth-based coordination polymer(CP)with carboxyl-thiol ligands,[Bi(C_(8)H_(2)O_(4)S_(2))(C2H8N)]n(Bi-DSBDC-DMA,DMBDC=2,5-disulfur-1,4-dicarboxylate,DMA=dimethylamine),have been successfully synthesized.X-ray diffraction analysis reveals that Bi-DSBDC-DMA possesses a layered structure,with two-dimensional(2D)Bi-DSBDC networks alternating with layers composed of dimethylamine ions.This material demonstrates semiconducting properties,featuring an optical bandgap of 2.2 eV and an electrical conductivity of 2×10^(-8) S/cm.Furthermore,electrodes based on this material exhibit a capacity of 250 mAh/g after 200 cycles for lithium-ion storage.

Anion storing,oxygen vacancy incorporated perovskite oxide composites for high-performance aqueous dual ion hybrid supercapacitors

Dual ion storage hybrid supercapacitors(HsCs)are considered as a promising device to overcome the limited energy density of existing supercapacitors while preserving high power and long cyclability.However,the development of high-capacity anion-storing materials,which can be paired with fast charg-ing capacitive electrodes,lags behind cation-storing counterparts.Herein,we demonstrate the surface faradaic OH-storage mechanism of anion storing perovskite oxide composites and their application in high-performance dual ion HsCs.The oxygen vacancy and nanoparticle size of the reduced LaMnO_(3)(r-LaMnO_(3))were controlled,while r-LaMnO_(3) was chemically coupled with ozonated carbon nanotubes(oCNTs)for the improved anion storing capacity and cycle performance.As taken by in-situ and ex-situ spectroscopic and computational analyses,OH-ions are inserted into the oxygen vacancies coordi-nating with octahedral Mn with the increase in the oxidation state of Mn during the charging process or vice versa.Configuring OH-storing r-LaMnO_(3)/oCNT composite with Na*storing MXene,the as-fabricated aqueous dual ion HSCs achieved the cycle performance of 73.3%over 10,000 cycles,delivering the max-imum energy and power densities of 47.5 w h kg^(-1) and 8 kw kg^(-1),respectively,far exceeding those of previously reported aqueous anion and dual ion storage cells.This research establishes a foundation for the unique anion storage mechanism of the defect engineered perovskite oxides and the advancement of dual ion hybrid energy storage devices with high energy and power densities.

Highly dispersed Co-Mo sulfide nanoparticles on reduced graphene oxide for lithium and sodium ion storage

A novel hybrid,highly dispersed spinel Co-Mo sulfide nanoparticles on reduced graphene oxide(Co3S4/CoMo2S4@rGO),is reported as anode for lithium and sodium ion storage.The hybrid is synthesized by one-step hydrothermal method but exhibits excellent lithium and sodium storage performances.The as-synthesized Co3S4/CoMo2S4@rGO presents reversible capacity of 595.4 mA·h·g^−1 and 408.8 mA·h·g^−1 after 100 cycles at a current density of 0.2 A·g^−1 for lithium and sodium ion storages,respectively.Such superior performances are attributed to the unique composition and structure of Co3S4/CoMo2S4@rGO.The rGO provides a good electronically conductive network and ensures the formation of spinel Co3S4/CoMo2S4 nanoparticles,the Co3S4/CoMo2S4 nanoparticles provide large reaction surface for lithium and sodium intercalation/deintercalation,and the spinel structure allows fast lithium and sodium ion diffusion in three dimensions.

Nanostructured Ion Storage Electrode Materials for Lithium Batteries and Supercapacitors

1 Results Performance of lithium-ion batteries, electrochemical capacitors, and other electric-energy storage devices is not only determined simply by macroscopic chemical composition of their electrode, but also strongly affected by shape and size of the active materials. Nanostructured materials are distinguished from conventional polycrystalline materials by the nanometer size of the structural units that compose them, and they often exhibit properties that are drastically different from the conventi...

Post lithium ion batteries for emerging energy storage technologies

It is obvious that in the next ten years,lithium ion batteries are still the dominating power source for a wide range of products including consumable electronics,vehicles(cars,motorbikes,scooters,buses),drones,and even robots and tanks.However,in the pursuit of cost-effective,safety-reliable,and highly efficient energy storage technologies,researchers are developing

Molten salt synthesis of α-MnO_(2)/Mn_(2)O_(3) nanocomposite as a high-performance cathode material for aqueous zinc-ion batteries

Thanks to low cost,high safety,and large energy density,aqueous zinc-ion batteries have attracted tremendous interest worldwide.However,it remains a challenge to develop high-performance cathode materials with an appropriate method that is easy to realize massive production.Herein,we use a molten salt method to synthesize nanostructured manganese oxides.The crystalline phases of the manganese oxides can be tuned by changing the amount of reduced graphene oxide added to the reactant mixture.It is found that the α-MnO_(2)/Mn_(2)O_(3) nanocomposite with the largest mass ratio of Mn_(2)O_(3) delivers the best electrochemical performances among all the products.And its rate capability and cyclability can be significantly improved by modifying the Zn anode with carbon black coating and nanocellulose binder.In this situation,the nanocomposite can deliver high discharging capacities of 322.1 and 213.6 mAh g^(-1) at 0.2 and 3 Ag^(-1),respectively.After 1000 cycles,it can retain 86.2% of the capacity at the 2 nd cycle.Thus,this nanocomposite holds great promise for practical applications.

A flexible CNT@nickel silicate composite film for high-performance sodium storage

Due to the sufficient ion diffusion channels provided by the large interlayer spacing, layered silicates are widely considered as potential anode materials for lithium ion and sodium ion batteries. However, due to the poor electronic conductivity, the application of layered silicates for electrochemical energy storage has been greatly limited. Carbon nanotube(CNT) film has excellent electrical conductivity and a unique interconnected network, making it an ideal matrix for composite electrochemical material. We herein report a CNT@nickel silicate composite film(CNT@NiSiO) fabricated by a SiO2-mediated hydrothermal conversion process, for sodium storage with excellent electrochemical properties. The obtained composite possesses a cladding structure with homogeneous nanosheets as the outermost and CNT film as the inner network matrix, providing abundant ion diffusion channels, high electronic conductivity, and good mechanical flexibility. Due to these merits, this material possesses an excellent electrochemical performance for sodium storage, including a high specific capacity up to 390 mAh g-1 at 50 mA g-1, good rate performance up to 205 mAh g-1 at 500 mA g-1, and excellent cycling stability. On this basis, this work would bring a promising material for various energy storage devices and other emerging applications.

Printable Zinc‑Ion Hybrid Micro‑Capacitors for Flexible Self‑Powered Integrated Units

Wearable self-powered systems integrated with energy conversion and storage devices such as solar-charging power units arouse widespread concerns in scientific and industrial realms.However,their applications are hampered by the restrictions of unbefitting size matching between integrated modules,limited tolerance to the variation of input current,reliability,and safety issues.Herein,flexible solar-charging self-powered units based on printed Zn-ion hybrid micro-capacitor as the energy storage module is developed.Unique 3D micro-/nano-architecture of the biomass kelp-carbon combined with multivalent ion(Zn2+)storage endows the aqueous Zn-ion hybrid capacitor with high specific capacity(196.7 mAh g^−1 at 0.1 A g^−1).By employing an in-plane asymmetric printing technique,the fabricated quasi-solid-state Zn-ion hybrid microcapacitors exhibit high rate,long life and energy density up to 8.2μWh cm^−2.After integrating the micro-capacitor with organic solar cells,the derived self-powered system presents outstanding energy conversion/storage efficiency(ηoverall=17.8%),solar-charging cyclic stability(95%after 100 cycles),wide current tolerance,and good mechanical flexibility.Such portable,wearable,and green integrated units offer new insights into design of advanced self-powered systems toward the goal of developing highly safe,economic,stable,and long-life smart wearable electronics.

Tailored amorphous titanium oxide and carbon composites for enhanced pseudocapacitive sodium storage

As an effective and competitive supplement to the commercialized lithium ion batteries(LIBs),sodium ion batteries(SIBs)have been receiving increasing attention in recent years due to lower cost,richer content,and broader distribution of sodium[1–7].Sodium has similar electrochemical properties to lithium,and thus the concepts for the preparation of electrode materials for SIBs can be borrowed from LIBs[8,9].

Realizing the highly reversible Zn^(2+)and Na^(+) dual ions storage in high-crystallinity nickel hexacyanoferrate microcubes for aqueous zinc-ion batteries

Prussian blue analogues(PBAs)with the 3D open framework are regarded as promising cathode candidates for aqueous Zinc ion batteries(ZIBs).Among various PBAs,nickel hexacyanoferrate(NiHCF)has attracted considerable attention because of its high operating voltage and economic merit.However,the cyclability of NiHCF is unsatisfactory due to poor structural stability during Zn^(2+) ions insertion/deinsertion.Moreover,the ion storage mechanism of NiHCF in aqueous electrolytes has not been fully revealed yet.Herein,high-crystallinity NiHCF(HC-NiHCF)microcubes with improved structural stability and larger crystal plane spacing are synthesized.For the first time,highly reversible Zn2+ions and Na+ions co-insertion/extraction are achieved for the HC-NiHCF microcubes in mixed aqueous electrolyte,as evidenced by various observations including two separated discharge plateaus and sequential changes of Na 1s and Zn 2p signals in ex-situ X-ray photoelectron spectroscopy(XPS).As a result,a high specific capacity of 73.9 mAh g^(−1) is obtained for the HC-NiHCF microcubes at 0.1 A g−1,combined with enhanced cycle stability(75%vs.16.4%)over 1000 cycles at 2 A g^(−1).The reversible Zn^(2+) ions and Na+ions co-insertion in HC-NiHCF microcubes reveals a new ion storage mechanism of Ni-based PBAs in aqueous electrolytes.

Rocking-chair ammonium ion battery with high rate and long-cycle life

Aqueous rechargeable ammonium-ion batteries(AIBs)have drew considerable attention because of their capacity for high rates,low cost,and high safety.However,developing desired electrodes requiring stable structure in the aqueous fast ammoniation/de-ammoniation becomes urgent.Herein,an ammonium ion full battery using Cu_(3)[Fe(CN)_(6)]_(2)(CuHCF)acting to be a cathode and barium vanadate(BVO)acting to be an anode is described.Its excellent electrochemical behavior of Prussian blue analogs and the perfectly matched lattice structure of NH_(4)^(+)is expected.And the open structure of vanadium compounds satisfies the fast ammoniation/de-ammoniation of NH4+is also achieved.As a result of these synergistic effects,the BVO//CuHCF full cell retains 80.5 percent of its capacity following 1000 cycling.These achievements provide new ideas for developing low-cost and long-life AIBs.

Facile fabrication of integrated three-dimensional C- MoSe2/reduced graphene oxide composite with enhanced performance for sodium storage

Scrupulous design and fabrication of advanced electrode materials are vital for developing high-performance sodium ion batteries. Herein, we report a facile one-step hydrothermal strategy for construction of a C-MoSe2/rGO composite with both high porosity and large surface area. Double modification of MoSe2 nanosheets is realized in this composite by introducing a reduced graphene oxide （rGO） skeleton and outer carbon protective layer. The MoSe2 nanosheets are well wrapped by a carbon layer and also strongly anchored on the interconnected rGO network. As an anode in sodium ion batteries, the designed C-MoSe2/rGO composite delivers noticeably enhanced sodium ion storage, with a high specific capacity of 445 mAh-g-1 at 200 mA.g-1 after 350 cycles, and 228 mAh-g 1 even at 4 A.g-1; these values are much better than those of C-MoSe2 nanosheets （258 mAh.g-a at 200 mA-g-1 and 75 mAh-g-1 at 4 A.g-~）. Additionally, the sodium ion storage mechanism is investigated well using ex situ X-ray diffraction and transmission electron microscopy methods. Our proposed electrode design protocol and sodium storage mechanism may pave the way for the fabrication of other high-performance metal diselenide anodes for electrochemical energy storage.