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p-Benzoquinone (BQ) is a promising candidate for next-generation sodium-ion batteries (SIBs) because of its high theoretical specific capacity, good reaction reversibility, and high resource availability. However, practical application of BQ faces many challenges, such as a low discharge plateau (∼2.7 V) as cathode material or a high discharge plateau as anode material compared with inorganic materials for SIBs and high solubility in organic electrolytes, resulting in low power and energy densities. Here, tetrahydroxybenzoquinone tetrasodium salt (Na4C6O6) is synthesized through a simple neutralization reaction at low temperatures. The four −ONa electron-donating groups introduced on the structure of BQ greatly lower the discharge plateau by over 1.4 V from ∼2.70 V to ∼1.26 V, which can change BQ from cathode to anode material for SIBs. At the same time, the addition of four −ONa hydrophilic groups inhibits the dissolution of BQ in the organic electrolyte to a certain extent. As a result, Na4C6O6 as the anode displays a moderate discharge capacity and cycling performance at an average work voltage of ∼1.26 V versus Na/Na+. When evaluated as a Na-ion full cell (NIFC), a Na3V2(PO4)3 ‖ Na4C6O6 NIFC reveals a moderate discharge capacity and an average discharge plateau of ∼1.4 V. This research offers a new molecular structure design strategy for reducing the discharge plateau and simultaneously restraining the dissolution of organic electrode materials.

All-solid-state lithium batteries are promising substitutes for traditional lithium ion batteries to solve the inherent safety issues of organic liquid electrolytes. However, the large interfacial resistance renders the batteries inefficient for practical applications. In this study, we have proposed a composite polymer/ceramic/composite polymer sandwiched electrolyte (CPCCPE), in which polyethylene oxide (PEO) is employed as the wetting polymer matrix on both the sides of CPCCPE, and a Ga and Nb co-doped garnet (i.e., Li6.35Ga0.15La3Zr1.8Nb0.2O12 (LGLZNO)), is used as the center of CPCCPE and also added into the PEO matrix to form the composite polymer. This battery architecture allows fluent lithium-ion transport across the interface and improves solid–solid interfacial contact, therefore resulting in increased ionic conductivity. Scanning electron microscopy (SEM), electrochemical impedance spectroscopy and galvanostatic charge/discharge (GCD) measurements demonstrate the effectiveness of this electrolyte configuration in enhancing the battery performance. The Li/CPCCPE/Li symmetrical cells exhibit stable plating/strapping properties over 500 h, and the constructed all-solid-state LiFePO4/CPCCPE/Li cells can maintain a high specific capacity (∼158 mA h g−1) after 100 cycles at 60 °C with coulombic efficiencies close to 100% during the long-term cycling process.

Three-dimensional N/S co-doped succulent-like hierarchical carbon (3D NS-SHC) is synthesized by carbonization of a supramolecular cluster. In this supramolecular process, potassium citrate can act as a reliable carbon source, while the thiourea as a N/S source and then, two molecules gradually tend to generate a giant “all-in-one” precursor via hydrogen bonding verified by Independent Gradient Model (IGM) calculation. TEM and SEM images show the N/S co-doped carbon holds a novel 3D succulent-like hierarchical structure. For NS-SHC-8:8 sample, element mapping images display the uniform N/S atoms distribution. These distinct features can be related to the supramolecular polymerization which promotes in-situ N/S co-doping homogenously and conduces to build 3D structure. Typically, NS-SHC-8:8 electrode exhibits prominent specific capacitance (258.5 F g−1 at 0.5 A g−1) and excellent cycle stability (94.4% after 20000 cycles) in three-electrode system. Furthermore, an assembled quasi-solid state symmetric supercapacitor delivers good energy density (10.2 Wh kg−1 at 250 W kg−1) and steady cycle endurance (85.1% after 10000 cycles). These eximious behaviors of NS-SHC-8:8 are mainly attributed to (1) the uniform N/S atoms distribution and their synergistic effect, which brings extra Faradaic reaction to higher specific capacitance, (2) the charming 3D succulent-like hierarchical structure, which serves as a multifunctional reservoir that can accommodate the ion/charge and facilitate their migration to further promote the electrochemical performance. Above mentions suggest that this uniformly heteroatom-modified carbon material produced by supramolecular technique is promising for high-performance energy storage devices.

A 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI–BF4) ionic liquid is introduced into an electrolyte as a functional additive to enhance the low-temperature performance of LiNi0.5Co0.2Mn0.3O2 (NCM523)/graphite batteries. Linear sweep voltammetry (LSV), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) tests show that EMI–BF4 can be oxidized in advance and produce low impedance solid-electrolyte interphase (SEI) films on the electrode surfaces. Compared with the batteries without the EMI–BF4 additive, the capacity retention of the NCM523/graphite batteries with 1% EMI–BF4 additive is enhanced from 82.3% to 93.8% after 150 cycles at a low temperature of −10 °C. In addition, at −30 °C, the discharge capacity of the batteries with 1% EMI–BF4 additive is nearly doubled. And at the room temperature of 25 °C and after 400 cycles, the capacity retention also increases from 80.3% to 85.9%, and the coulomb efficiency remains at approximately 100%. These results demonstrate that EMI–BF4 used as a functional electrolyte additive has promising prospects for application to improve the low-temperature performance of NCM523-based lithium-ion batteries.

Organic electrode materials have high capacity, and environmentally friendly advantages for the next generation lithium-ion batteries (LIBs). However, organic electrode materials face many challenges, such as low reduction potential as cathode materials or high reduction potential as anode materials. Here, the influence of chemical functionalities that are capable of either electron donating or electron withdrawing groups on the reduction potential and charge-discharge performance of anthraquinone (AQ) based system is studied. The cyclic voltammetry results show that the introduction of two —OH groups, two —NO2 groups and one—CH3 group on anthraquinone structure has a little impact on the reduction potential, which is found to be 2.1 V. But when three or four—OH groups are introduced on AQ structure, the reduction potential is increased to about 3.1 V. The charge-discharge tests show that these materials exhibit moderate cycling stability.

A new type of sandwiched nanosheets 3D MoS2/C@RGO is synthesized by supramolecular self-assembly methods, as a novel and excellence electrode material. The surface characterization techniques show that the sandwiched 3D MoS2/C@RGO possesses rich porosity and large specific area, which is convenient for electrolyte ion transportation and beneficial for the improved electrical conductivity. An outstanding specific capacitance of the prepared MoS2/C@RGO of 340.0 F/g at 1 A g−1 is achieved with an excellent cycle stability of 90% after 1000 cycles at the scanning rate of 40 mV/s. The sandwiched 3D MoS2/C@RGO is suggested to be an ideal candidate for supercapacitors.

Lithium bisoxalatodifluorophosphate (LiBODFP) is a promising multifunctional lithium salt-type electrolyte additive used to enhance the performance of 5 V LiNi0.5Mn1.5O4 (LNMO)-based lithium-ion batteries (LIBs). Compared to cells without the additive, the cycling retention of the LNMO/Li half cells with 1.0% LiBODFP was improved from 77.6% to 93.7% at a 1C rate after 300 cycles. The capacity retention of the high voltage LNMO/graphite full cells with LiBODFP reached 82% at a 0.5C rate after 100 cycles, which was much higher than that of the cells without the additive (50%). It is shown that the LiBODFP can be preferentially oxidized and reduced to form robust interface films with low resistance and high conductivity on the surfaces of LNMO cathodes and graphite anodes, respectively. The LiBODFP-derived interface film can protect the cathode and anode materials, alleviate the decomposition of the electrolyte, and prevent the dissolution of metal ions from the LNMO cathode and their deposition on the graphite surface. This work provides an effective strategy for developing a functional electrolyte that matches the requirement of LNMO-based batteries with a high-voltage window and enhanced performance.

We report a supramolecular strategy to fabricate high-doping-leveled (10.5 at.%) porous nitrogen-doped reduced graphene oxide (P-NrGO) with outstanding electrochemical properties as electrode material for supercapacitors. The introduced supramolecular polymers melamine cyanurate (MC) acts a barrier to prevent the graphene sheets from restacking, and meanwhile functions as a soft template to create porous structure as well as nitrogen source for in-situ N-doping. The transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images show that the P-NrGO exhibits wrinkled and loose-packed thin layer structure with a large number of pores. X-ray photoelectron spectrometer (XPS) spectra demonstrate that pyridine and pyrrole-N was the main nitrogen bonding states, which were favorable for the improvements of supercapacitive performance. Attributed to the synergistic effects of the porous structure and the N-doping, the P-NrGO1 exhibits an increase of 56.5% in the specific capacitance (335 F g−1) when compared with the rGO (214 F g−1). In addition, the capacitance retention ratio reaches 94.3% after 10000 cycles, indicating the excellent electrochemical stability. The present work benefits the large-scale production of N-doped graphene oxide for high-performance supercapacitors.

A manganese dioxide (MnO2) film is electrodeposited onto a gold-coated quartz crystal electrode by a galvanostatic method. The scanning electron microscopy (SEM) image shows that the electrodeposited MnO2 film consists of nanorods with diameters of 15–20 nm. The cyclic voltammetric (CV) and electrochemical quartz crystal microbalance (EQCM) results demonstrate that the MnO2 electrodes exhibit similar specific capacitance (SC) and mass-to-charge ratios (MCR) in those electrolytes that contain the same cation but different anions. However, the SC and MCR are different in those electrolytes that contain the same anion but different cations. The SC of MnO2 electrodes increases with a decrease of the cationic radius and an increase of the cationic charge. The smaller the cationic radius, the smaller the deviation of the MCR from the equivalent weight (EW) of the cation. The results illustrate that the pseudocapacitive charge storage mechanism of MnO2 involves the cation in the electrolyte and its intercalation/deintercalation, which are affected by the charge number and the cationic radius. This work offers a theoretical basis for selecting suitable electrolytes to couple MnO2-based electrodes in supercapacitors.

The overcharge safety and behaviors of lithium-ion batteries (LIBs) with LiCoO2 cathode are investigated under a successive constant current (CC) and constant voltage (CV) charge mode. It is indicated that in the case of smaller charge currents, a higher probability for the LIBs passing the overcharging test can be obtained. The batteries can safely pass CC overcharge test at 0.25C to 10 V, and then about 80% batteries can also pass CV overcharge test. Whereas, with increasing the CC currents to 0.33C, 0.5C, and 1C, about 50%, 30%, and 10% batteries can directly pass the overcharge test at the CC step, and then about 20%, 10%, and 0% batteries approach 10 V and subsequent pass CV overcharge test, respectively. Besides the charge current, it is also demonstrated that whether the LiCoO2/graphite batteries are likely to achieve energy balance and pass the overcharge test basically depends on the formation of the internal short-circuit pathways derived from the cobalt and lithium deposition in the separator during the overcharge process. The cobalt deposition will be more uniform when the battery core has shape stability of assembly-structure, which can be used as an effective measure to raise LIBs through the overcharge test. In addition, relative more uniform cobalt dendrites can also be formed if a double layer separator is adopted, which reduces the local short-circuit risk caused by the melting or shrinkage of the separator and correspondingly improves the ratio of LIBs passing through the overcharge test. These risk reduction measures can be used in the battery manufacture to improve the overcharge safety of LIBs.

Using chitosan as the carbon and nitrogen source, highly-crystalline lithium titanate nanoparticles with N-doped carbon-coating (N-C/LTO) have been successfully synthesized via a facile refluxing and microwave-assisted hydrothermal processes followed by a subsequent calcination step. Due to the effect of chitosan-confined, the fabricated N-C/LTO composites crystallized into well-defined cubic spinel structure with an average size of ∼50 nm, leading to a significantly enhanced specific surface area. The successful doping of nitrogen into the carbon layer of the N-C/LTO has been confirmed by XPS technology. The porous LTO with nitrogen-doped carbon coating fabricated with chitosan exhibits superior electrochemical performance (a high reversible capacity of 194 mAh g−1 was achieved at 1 C). This work therefore reveals that the N-doped carbon coating realized by chitosan confinement is an effective way for enhancing the surface lithium storage capability of LTO as the anode materials for lithium-ion batteries (LIBs).

In this work, a NH4HCO3 co-precipitation method was used to prepare the precursor of LiNi0.5Mn1.5O4 (LNMO). An orthogonal experiment method was applied to analyze the effects of synthetic conditions such as concentration and molar ratio of Mn2+ and Ni2+ in initial solution, reaction temperature, concentration of NH4HCO3, addition speed of NH4HCO3 on the molar ratio of Mn/Ni in the sediments, through which the co-precipitation process was also optimized. It was found that both Mn and Ni are not completely precipitated from the NH4HCO3 solution, and the precipitation rate of Ni2+ is much lower than that of Mn2+. Among these synthetic conditions, the molar ratio of Ni/Mn in the mixed metal ion solution has the greatest impact on the molar ratio of Mn/Ni in the precursor. A LNMO spinel with precise stoichiometric Ni/Mn and classic Fd 3 ¯ m structure was obtained by using a precursor prepared under the optimal synthesis conditions. Additionally, the prepared LNMO has a spherical hierarchical morphology, composed of submicron primary particles with a chamfered polyhedral structure. This LNMO shows superior electrochemical performance. It delivers a high reversible capacity of ∼110 mAh/g and superior capacity retention of 68.2% after 900 cycles at 1 C. Even at a higher discharge rate of 10 C, the LNMO material still shows a reversible capacity of 84 mAh/g.

A 3-anthraquinone substituted polythiophene (poly[3–(2-anthraquinone)-2,5-thiophene], P3-AQT)) was synthesized by chemical oxidation polymerization using FeCl3 as oxidant. The structure and thermal stability of P3-AQT were characterized by infrared spectroscopy and thermogravimetric analysis. Due to its electrochemical activity in the range of 0–3.0 V, P3-AQT can be used as an anode material for lithium-ion batteries. The P3-AQT/Li batteries were assembled and their electrochemical properties were studied. P3-AQT electrodes can deliver an initial charge capacity of 791 mAh g−1 at a current density of 50 mA g−1 and show good cycle stability at high current density. When the current density is 1000 mA g−1, the initial charge specific capacity is 710 mAh g−1, and the specific capacity remains at 505 mAh g−1 after 100 cycles. The results indicate that the introduction of anthraquinone at the 3-position of polythiophene can increase the reversible capacity of polythiophene and P3-AQT is a potential anode material for lithium-ion batteries.

A large flat-conjugated copolymer poly[ethylene-N,N'-bis(2-ethylhexyl)-1,4,5,8-naphthalene diimide] (PENDI), was synthesized through a simple synthetic method, which is preparation via 2,6-dibromo-N,N'-bis(2-ethylhexyl)-1,4,5,8-naphthalene diimide, and (E)-1,2-bis(tributylstannyl) ethene via Stille coupling reaction for use as a cathode material for lithium ion batteries. The PENDI copolymer was characterized by IR, UV-vis spectra, 1H NMR, and TGA. The electrochemical performance results demonstrated that the reversible capacity of PENDI can be retained at 85% of its initial theoretical capacity with a steady discharge voltage plateau of 2.0–2.5 V after 100 cycles at 0.1 C, and the coulomb efficiency remained above 98%. This can be attributed to the low solubility of the copolymer PENDI in electrolyte and the excellent structural stability of the copolymer PENDI during the charge–discharge tests. The synthesis of polymers with high conjugated systems and more stable structures will become a major breakthrough for the exploitation and optimization of cathode materials.

In this work, a naphthalene tetracarboxylic acid lithium salt (NTCLi) as anode material is designed for lithium-ion batteries, with high theoretical capacity and conjugated system according to the combination principles of multi-carboxyl groups and low molecular weight, which is prepared through a simple one-pot neutralization reaction. The sample is characterized by SEM, TEM, XRD, IR and TGA. The results show that NTCLi exhibits nanorod-like structure, well thermal stability and crystalline structure. The electrochemical measurements results demonstrate the initial discharge capacity of 276 mAh g− 1 with low discharge platform (~ 0.9 V) at the current density of 0.1 C are achieved for NTCLi, and the discharge specific capacity of 190 mAh g− 1 can be retained after 100 cycles. Also, NTCLi delivers good rate capability with discharge capacity of up to 112 mAh g− 1, even at a current density as high as 2 C, indicating the as-prepared sample could be a promising candidate as anode materials for lithium-ion batteries.

A novel tucked flower-like SnS2/Co3O4 structure is synthesized by growing Co3O4 in the gaps between petals of SnS2 microflowers through a facile solution method. In our strategy, the petals of the flowers are curled inwards due to the swelling force resulting from growth of Co3O4, resulting in the encapsulation of Co3O4 with the SnS2 petals forming a coating structure. The SnS2/Co3O4 composite displays greatly improved performance in comparison with pure SnS2. After 100 cycles, an outstanding reversible capacity of ∼715 mAh g−1 with negligible capacity fading is achieved at current density of 100 mA g−1 for SnS2/Co3O4. What is more, the SnS2/Co3O4 exhibits excellent rate capability, and a reversible capacity of up to ∼530 mAh g−1 is obtained, even at a current density as high as 1000 mA g−1. The morphology of tucked flower-like petals and the introduction of the secondary structure of Co3O4 are suggested to be responsible for the improved lithium storage capacity of the composite. The as-prepared SnS2/Co3O4 shows promise as a potential anode material for Li-ion batteries due to its simple synthesis method and large capacity.

Two novel conjugated copolymers (P1 and P2) with donor–acceptor architecture, based on triphenylamine, benzodithiophene and thiazolothiazole (TTz), have been prepared by the Stille coupling reaction. Compared with alternative copolymer P1 with the single electron-withdrawing unit TTz, random copolymer P2 introduced another stronger electron-withdrawing unit benzothiadiazole intramolecularly. Incorporation of two different electron-withdrawing units on the backbone was proved to have a significant influence on the optical and electrical properties. Compared with P1, copolymer P2 has the wider absorption spectrum, lower bandgap, and therefore the better device performances.

The electrochemical behaviors and simultaneous determination of three dihydroxybenzene isomers, i.e., catechol (CC), resorcinol (RC), and hydroquinone (HQ), are studied using a thermally reduced carbon nano-fragment modified glassy carbon electrode (CNF/GCE). The soluble CNF modifier with unique micro-/nano-structure and abundant edges and defective sites is prepared by chemically oxidizing graphite powders, ultrasonically crushing, and thermally reducing treatment in turn. It is shown that the oxidation peak currents of CC, RC, and HQ at the CNF/GCE are improved about 1.74, 2.88, and 1.05 times compared to that of the GCE. The diffusion process in bulk solution controls the electrochemical reaction of CC, RC, and HQ, and their reversible electrochemical process involves equal numbers of protons and electrons. Based on the enhanced electrocatalytic activity and enlarged separation of the anodic peak potential towards three dihydroxybenzene isomers at the CNF/GCE, the simultaneous differential pulse voltammetry (DPV) determination of CC, RC, and HQ, with detection limits (S/N = 3) of 5.0 × 10−7 mol L−1, 8.0 × 10−7 mol L−1 and 4.0 × 10−7 mol L−1, respectively, are obtained. The CNF/GCE also indicates high selectivity, stability, and reproducibility, and is comparable with results of high-performance liquid chromatography in real samples, clearly indicating its applicability.

Organic electroactive materials are promising candidates for next generation sodium ion batteries (SIBs) due to their low cost, sustainability and environmental benignity. It is of great interest to develop organic compounds with multifunctional groups to be used as electrode materials for SIBs owing to their light weight, multi-electron reactions, redox stability and structural diversity. The organic compound 4,8-dihydrobenzo[1,2-b:4,5-b′] dithiophene-4,8-dione (BDT) was prepared by a facile solution method, and its graphene composite (BDT–G) was synthesized by a simple dispersion–deposition process. BDT–G as a cathode material demonstrated much enhanced electrochemical performance, including higher reversible capacity (217 mA h g−1vs. 145 mA h g−1), better cycling performance (∼175 mA h g−1vs. ∼100 mA h g−1 after 70 cycles at 0.2C), and higher rate capabilities (1.7 times better than BDT at 2C) compared with BDT. It is revealed that these improved electrochemical properties should be mainly attributed to the excellent electronic conductivity and ionic transport efficiency promoted by graphene. Furthermore, the fast electrode reaction of BDT with the help of unlimited electron transport via the two-dimensional graphene network results in enhanced usage of materials, and BDT in the composite with graphene could be inhibited from dissolution in the organic electrolyte.

The synthesis of Co 3 O 4 nanostructures with controllable morphology through hydrothermal reaction was investigated. Through adjusting the reaction temperature, mesoporous nanowires (Co 3 O 4 -NWs) and mesoporous nanoflakes (Co 3 O 4 -NFs) can be directly grown on nickel foam at a reaction of temperature of 90 °C and 120 °C, respectively. Compared with Co 3 O 4 -NWs, Co 3 O 4 -NFs displays greatly improved performance of cyclic stability and rate capability. After 100 cycles, an outstanding reversible capacity of 1300 mAh g ⿿1 with negligible capacity fading is achieved at current density of 100 mA g ⿿1 for Co 3 O 4 -NFs. Furthermore, Co 3 O 4 -NFs exhibit excellent rate capability, with a reversible capacity up to ⿼450 mAh g ⿿1 even at a current density as high as 8 A g ⿿1 . Due to the directly growing aligned Co 3 O 4 nanoflakes on conductive 3D nickel foam, the Co 3 O 4 -NFs electrode shows superior electrochemical performance, with potential as a promising anode candidate for lithium ion batteries.

Solvothermal reactions of Co2+ and Mn2+ salts with 2-(trifluoromethyl)-1H-4,5-imidazole dicarboxylic acid (H3TFMIDC) lead to two novel three-dimensional (3D) metal–organic frameworks (MOFs), namely, [Co6(μ3-TFMIDC)4(H2O)12]·15H2O (1) and [(Me2NH2)3][MnII6 MnIII(μ3-TFMIDC)6(H2O)6]·18H2O (2). Single-crystal X-ray diffraction analysis reveals that both of them are based on interesting planar tetranuclear squares [M4(TFMIDC)4] as secondary building units (SBUs). Compound 1 exhibits a unique 3D two-fold interpenetrated network with the diamondoid topology consisting of the tetranuclear square SBUs as 4-connected nodes, while compound 2 features an unusual (6,16)-connected 3D framework based on the novel tetranuclear square SBUs as 16-connected nodes and trivalent manganese ions as 6-connected nodes, representing the first 16-connected MOF utilizing planar tetranuclear square SBUs as building blocks. Our results open up new perspectives to design novel 3D extended MOFs, especially the unique highly connected 3D MOFs by employing planar tetranuclear square SBUs. Moreover, IR spectroscopy, powder X-ray diffraction, thermogravimetric analyses, and a study on the magnetic properties of both compounds, have been also performed.

SnS2 is considered as a promising anode material for lithium-ion batteries (LIBs) due to its high theoretical specific capacity, low toxicity, and low cost. However, its development has been hindered by the volume expansion/contraction during lithiation/delithiation process and also the poor electronic conductivity. Even TiO2 has been widely employed to improve the stability of the bulk SnS2, the underlying mechanism and its interaction with SnS2 remains unclear. Here, we synthesize two different kinds of SnS2/TiO2 heterojunctions with 3D ball-like structures (denoted as BST-1 and BST-2) assembled from nanosprindle and nanosphere TiO2 encapsulated in 3D SnS2 flowers, aiming to investigate their electrochemical performance and structural stability. Compared with pristine SnS2, the 3D BST-1 and BST-2 demonstrate high specific capacity, remarkable rate capability and cycling stability. Ex-situ X-ray diffraction shows that four phase transitions occur to pure SnS2 during charge and discharge process whereas only two to BST-1 and BST-2. We attribute the difference to rapid ion transports introduced by in-situ lithiating TiO2, which helps stabilize the structure of SnS2.

Based on the re-construction idea of carbon nanomaterials, novel folding re-constructed carbon nanosheets (re-CNSs) with unique microstructure and higher lithium-ion storage capacity than prototype graphite powders are prepared. The nanoscale carbon-fragment suspension is firstly prepared through a successive chemical oxidation of graphite and ultrasonic crushing operation, and the re-CNS powders are then obtained by spray drying the suspension and a subsequent high-temperature reducing process. The as-prepared re-CNSs exhibit a folding appearance with a width of several micrometers, with a maximum initial specific capacity of 903 mAh g−1 for the re-CNSs sample thermally reduced at 500 °C (re-CNSs500). After 100 cycles, the reversible capacity is maintained at about 400 mAh g−1 for the re-CNSs500. The abundant carboxylic and hydroxide groups, edges, and defective sites of individual graphite oxide fragments facilitate the dislocation formation in the re-CNSs. In addition, a dislocation mechanism is thus used to describe the enhanced lithium-ion storage.

An unprecedented unique sandwich-like Co 3 O 4 /TiO 2 composite (SCT), for which TiO 2 nanospindles are embedded inside the porous cube-like structures stacked from Co 3 O 4 nanosheets, was fabricated through a facile hydrothermal method. The composition and morphology were characterized by X-Ray Diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Energy-Dispersive X-Ray Spectroscopy (EDS). The SCT electrode manifested excellent electrochemical performance with a capacity retention of 668 mAh g −1 after 120 cycles at 100 mA g −1 , and 785 mAh g −1 after 60 cycles tested successively at 100, 300, 500, 1000, 500, 100 mA g −1 (each for 10 cycles), which is better than that of the prepared pristine Co 3 O 4 electrode. The unique sandwich-like structure is responsible for the enhanced electrochemical performance.

We report the synthesis of a novel shuttle-like Fe3O4–Co3O4 self-assembling architecture through a facile hydrothermal method. The composite manifests quite excellent electrochemical performance as anodes of Li-ion batteries. It delivers a high reversible capacity of ∼1013 mA h g−1 at 100 mA g−1 after 100 cycles (∼1246 mA h g−1 at 0.5 A g−1, 864 mA h g−1 at 1 A g−1 and 625 mA h g−1 at 2 A g−1 after 50 cycles). The rate performance is also outstanding with a reversible capacity of 660 mA h g−1 even at 5 A g−1 and a capacity retention of 94% after 78 cycles. The synergetic effect of Co3O4 and Fe3O4, as well as the unique self-assembling architecture, may be responsible for the large enhanced electrochemical performance.

A novel Eu(III)–Ag(I) coordination polymer [Eu2Ag(μ4-oPyIDC)2(NO3)(H2O)]n (H3oPyIDC = 2-(pyridine-3-yl)-1H-imidzole-4,5-dicarboxylate, 1) was formed based on a planar hexanuclear heterometallic Eu4Ag2 secondary building unit. The planar hexanuclear secondary building blocks are interconnected to a 3D framework with pcu topology. The luminescence property of compound 1 is also investigated.

Lithium terephthalate (Li2C8H4O4, PTAL), a carboxylate-based organic electrode material, displays high reversible capacity of up to 248 mA h g−1 and long cycle life, which is promoted by graphene as a sustainable anode material for lithium ion batteries.