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Traditional O3-type Li-rich layered materials are attractive with ultra-high specific capacities, but suffering from inherent problems of voltage hysteresis and poor cycle performance. As an alternative, O2-type materials show the potential to improve the oxygen redox reversibility and structural stability. However, their structure-performance relationship is still unclear. Here, we investigate the correlation between the Li component and dynamic chemical reversibility of O2-type Li-rich materials. By exploring the formation mechanism of a series of materials prepared by Na/Li exchange, we reveal that insufficient Li leads to an incomplete replacement, and the residual Na in the Li-layer would hinder the fast diffusion of Li+. Moreover, excessive Li induces the extraction of interlayer Li during the melting chemical reaction stage, resulting in a reduction in the valence of Mn, which leads to a severe Jahn-Teller effect. Structural detection confirms that the regulation of Li can improve the cycle stability of Li-rich materials and suppress the trend of voltage fading. The reversible phase evolution observed in in-situ X-ray diffraction confirms the excellent structural stability of the optimized material, which is conducive to capacity retention. This work highlights the significance of modulating dynamic electrochemical performance through the intrinsic structure.

Various properties of sodium ion batteries deteriorate severely when dropping to subzero temperature. Herein, we reveal an accelerated charge-transfer mechanism for high-voltage Na3V2(PO4)2F3 cathode through constructing weakly-solvating architecture, which endows it with superior temperature adaptability (capacity retention of C − 25 ∘ C / C 25 ∘ C reaches 90.8%). The resulting weak solvation effects synergistically lower the activation energy barrier for charge-transfer reactions, thus accelerating the kinetics at low temperature and increasing the energy density by ∼75 Wh Kg−1. Ab initio molecular dynamics calculations show that a weakly-solvating structure forms spontaneously in a low-concentration electrolyte (merely 0.3 M) and thereby facilitates Na+ desolvation process. Besides, visual TOF-SIMS confirms the construction of a dense and uniform cathode/electrolyte interface layer, which optimizes the interface chemistry and improves the interfacial kinetics. In-situ and ex-situ XRD also evidence a smaller degree of structural evolution of the Na3V2(PO4)2F3 cathode, which contributes to long-term durability (attaining a high capacity retention of 93.4% after 1000 cycles at −25 °C). Furthermore, it is demonstrated that under such extreme conditions the Na3V2(PO4)2F3||hard-carbon full cell functions well for over 300 h. These findings elucidate the roles of weak solvation construction in realizing faster kinetics for high-voltage cathodes and provide a feasible pathway for achieving more practical sodium ion batteries.

BiFeO3 was prepared by using a simple one-step hydrothermal synthesis method. The key factor is to rapidly cool the product after the hydrothermal reaction in order to suppress the formation of Bi2Fe4O9 and Bi25FeO40 phases. Different cascade structures of TiO2 and BiFeO3 with controllable dopants(Pr, Al) and concentrations were also prepared on the FTO. The J-V test showed that the photoelectric conversion efficiency of the conventional TiO2 photoanode was increased from 2.54% to 3.21%. However, the J-V tests of Bi0.98Pr0.02FeO3, BiFe0.95Al0.05O3 and Bi0.98Pr0.02Fe0.95Al0.05O3 indicated that their photoelectric conversion efficiencies were up to 3.97%, 4.07%, and 4.99% respectively.

For sodium-ion batteries (SIBs), the electrochemical process for electrodes involves ion transport in the solid electrolyte interphase (SEI) and active materials. Generally, the large ion radius of Na+ is often considered as the key factor in poor electrode kinetics. However, for conversion-type metal oxide anodes with low redox potentials, unstable SEIs as well as the corresponding kinetic barrier also have significant effects on electrochemical behaviors and deserve more attention. Herein, porous and micro-spherical (Mn0.6Co0.3Ni0.1)3O4 is tailored as a SIB anode using co-precipitation. A high Mn percentage is beneficial to the formation of a micro-spherical morphology during co-precipitation. Due to its lack of electrochemical activity, Mn also contributes to the morphological stability of active materials during cycling. This allows for a clear observation regarding morphological changes of SEI products generated at the electrode surface. It is revealed that branch-like products are gradually converted into a dense interphase layer at electrode surfaces during cycling. The unstable and uneven topography of these electrode surfaces generates kinetic barriers that account for low rate capacities of the as-obtained (Mn0.6Co0.3Ni0.1)3O4 materials. The synthesized metal oxide is able to retain 98.1% of its initial sodiation capacity after 2000 cycles at 0.5 A g−1.

In the present study, hierarchical bismuth ferrite (BFO) and Ag2O-doped bismuth ferrite (Ag2O/BFO) nanostructures are successfully fabricated using hydrothermal methods. The fabricated nanostructures were characterized via several analytical techniques. BiFeO3 (BFO) nanoparticles were found to be 30–50 nm in diameter with pure perovskite phase. The nanocomposites were used for the preparation of photoanode to fabricate the dye-sensitized solar cells (DSSCs). The results revealed that the doping of Ag2O nanoparticles with BFO improves the transportation of electrons and decreased the recombination of photogenerated charges. Because of these advantages, the DSSC based on the Ag2O/BFO photoanode has been fabricated and shows the efficiency of energy conversion about to 4.25%, which indicates>100% development equated to the DSSCs fabricated using pure BFO nanoparticle based photoanode and prepared under the similar conditions. These results indicate that the BFO based nanocomposites doped with silver oxide can potentially be used as working electrode materials in DSSCs.

Existing rechargeable batteries not only fail to meet the demand for high power applications but also cause heavy metal pollution. Li-ion capacitors (LICs), which can achieve higher charging speeds and energy densities than supercapacitors, have attracted extensive attention. Nevertheless, sluggish Li-ion diffusion of the battery-type anode results in limited rate performance of LICs. Herein, high-performance LICs using by both battery and capacitor type Mn2V2O7-graphene (MVO-G) anodes and hempstem-derivated activated carbon (HSAC) cathodes with a large surface area are first reported. In addition to high pseudocapacitance, the MVO-G possesses the advantage of fast Li+ storage performance making it a suitable choice for advanced LIC anodes. Graphene is employed to enhance overall conductivity and cycling stability leading to enhanced energy storage. The MVO-G//HSAC LICs exhibit a high energy density of 148.1 Wh kg–1 at a power density of 150 W kg–1 and 25 Wh kg–1 even at 15 kW kg–1. More importantly, the MVO-G//HSAC LICs also show excellent cycling stability of 90% after 15000 cycles, which is expected for high performance energy storage systems.

Carbon coating always has a positive effect on improving the electrochemical performance of electrode materials for lithium ions batteries and its mechanism has once drawn great attention, yet few studies offer a model to elaborate on it. In this study, we select PNb9O25 nanowires as anode material and coat carbon on them to investigate how carbon layer does affect its electrochemical performance. Meanwhile, a theoretical model has proposed for the investigation of mass transfer and electron transfer at the surface of PNb9O25. The result suggests that due to the presence of carbon layer, mass transfer and electron transfer at the surface of PNb9O25 shows a decent boost, leading to the improvement of electrochemical performance at the high current density.

Development of high-efficiency non-noble metal materials to substitute Pt-based catalysts for oxygen reduction reactions is crucial in the commercial viability of Zn-air batteries technology. Nitrogen doped carbons (NDCs) are highly appealing as promising candidates. This study reports a facile molten salt (MS) method to synthesize aerogel-like nitrogen doped carbon (NDC-MS). The eutectic mixture acting as combined solvent and porogen leads to the obtained porous materials with extremely large surface area (1548.6 m2 g−1) and relatively high pore volume. The unique aerogel-like structure with hierarchical structure, increased catalytic active sits, extended surface area and large pore volume is beneficial for enhancing oxygen reduction reaction (ORR) performance. The resultant NDC-MS displays a superb ORR catalytic activity with high half-wave potential of 0.88 V, which is one of the most effective figures in previous literature of metal-free catalysts. The superb ORR performance can also be evaluated by Zn–air batteries with satisfactory power density and long-term operation stability. Therefore, such an efficient and green synthetic strategy can open up a new avenue for a wide range of commercial application of heteroatom doped carbon materials in advanced energy technologies.

Oocyte meiotic maturation failure and unfaithful chromosome segregation are major causes for female infertility. Here, we showed that CENP-W, a relatively novel member of the kinetochore protein family, was expressed in mouse oocytes from the germinal vesicle (GV) to metaphase II (MII) stages. Confocal microscopy revealed that CENP-W was localized in the germinal vesicle in the GV stage, and then became concentrated on kinetochores during oocyte maturation. Knockdown of CENP-W by specific siRNA injection in vitro caused kinetochore-microtubule detachment, resulting in severely defective spindles and misaligned chromosomes, leading to metaphase I arrest and failure of first polar body (PB1) extrusion. Correspondingly, spindle assembly checkpoint (SAC) activation was observed in CENP-W knockdown oocytes even after 10h of culture. Our results suggest that CENP-W acts as a kinetochore protein, which takes part in kinetochore-microtubule attachment, thus mediating the progression of oocyte meiotic maturation.

Titanate-based compounds have been considered as a hopeful family of anode materials for high-performance lithium-ion batteries due to the “zero-strain” characteristics, low cost, excellent safety and high potential plateau, and free generation of metallic Li and solid electrolyte interphase film. Nonetheless, the large-scale applications of titanate-based compounds are limited by the intrinsically low Li-ion diffusion coefficient and poor electronic conductivity. Considerable efforts have been devoted to solving these challenges towards practical applications, and some crucial progresses have been made. In this review, we present a comprehensive overview of the structural features, transport properties, and modification strategies of titanate-based compounds. The research progress of various effective strategies for enhancing Li-ion diffusion coefficient, electronic conductivity and electrochemical performance are emphatically summarized, including ion-doping, surface modifications, particle morphology control, construction of composite electrodes, etc. This review also gives a compendious summary of gassing mechanism of Li4Ti5O12-based battery and the solution. Designing delicate architectures of carbon coating is an efficient strategy to obtain high-performance titanate-based materials, which can restrain gassing behavior and achieve the high electronic conductivity simultaneously. At last, an insight into the future research directions and further developments of titanate-based compounds is prospected so as to promote their wide application. The review will offer significant comprehension for design and optimization of high performance of the titanate-based compounds.

Layered titanates (LT) have aroused considerable attention as advanced anodes for high-performance Na-ion batteries. However, their intrinsic issues including low electronic conductivity and sluggish sodiation kinetic hinder the implementation of achieving superior rate capability and long cycle stability simultaneously. Herein, a crystallization-induced surface defect engineering to promote the electrochemical activity of LT by electronic structure modulation and diffusion kinetics regulation is proposed. As evidenced by electrochemical characterization, this surface defect modification strategy can effectively reduce the polarization and facilitate fast electronic/ionic diffusion of titanates. Thereby, the targeted low-crystalline layer modified layered titanate (LC-LT) unfolds enhanced rate capability and cycle stability (8000 cycles, 88%). Theoretical calculations reveal that the LC-LT is equipped with narrower bandgap originated from the 3d orbital of oxygen vacancies-induced defective Ti atoms on the surface. Moreover, reduced Na+ migration energies and interconnected Na+ diffusion pathways are predicted in LC-LT by density functional theory (DFT) calculations and bond valence site energy (BVSE) analysis. When applied in Na-ion full cell with NASICON-type Na3V2(PO4)2F3 cathode, the configuration exhibits comparable rate performance and cycle stability (800 cycles, 81.6%).

An ultra-high ion-selective Nafion composite membrane modified by phosphotungstic acid (PWA) coupled silica for vanadium redox flow battery (VRB) was constructed and prepared through solution casting. The composite membrane exhibits excellent proton conductivity and vanadium ions blocking property by incorporating the nanohybrid composed of silica and PWA into the Nafion ionomer. Simple tuning for the filling amount of the nanohybrid endows the obtained membranes preeminent vanadium barrier property including a minimum vanadium permeability of 3.13 × 10−7 cm2 min−1 and a maximum proton conductivity of 0.081 S cm−1 at 25 °C. These indicate an ion selectivity of 2.59 × 105 S min cm−3, which is 6.8 times higher than that of recast Nafion (0.33 × 105 S min cm−3). As a result, the VRB with the composite membrane shows superior battery performance containing a lower self-discharge rate, higher capacity retention and more robust cyclic stability compared with recast Nafion over a range of current densities from 40 to 100 mA cm−2.

Before fertilization, ovulated mammalian oocytes are arrested at the metaphase of second meiosis (MII), which is maintained by the so-called cytostatic factor (CSF). It is well known that the continuous synthesis and accumulation of cyclin B is critical for maintaining the CSF-mediated MII arrest. Recent studies by us and others have shown that Ccnb3 is required for the metaphase-to-anaphase transition during the first meiosis of mouse oocytes, but whether Ccnb3 plays a role in MII arrest and exit remains unknown. Here, we showed that the protein level of Ccnb3 gradually decreased during oocyte meiotic maturation, and exogenous expression of Ccnb3 led to release of MII arrest, degradation of securin, separation of sister chromatids, extrusion of the second polar body (PB2), and finally entry into interphase. These phenotypes could be rescued by inhibition of Wee1B or CDK2. Our results indicate that Ccnb3 plays a critical regulatory role in MII arrest and exit in mouse oocytes.

A core shell structured C@MoxTi1-xO2-δ nanocrystal with a functionalized interface (C@MTNC-FI) was fabricated via the hydrothermal method with subsequent annealing derived from tetrabutyl orthotitanate. The formation of anatase TiO2 was inhibited by the simultaneous presence of the hydrothermal etching/regrowth process, infiltration of Mo dopants and carbon coating, which endows the C@MTNC-FI with an ultrafine crystalline architecture that has a Mo-functionalized interface and carbon-coated shell. PtRu nanoparticles (NPs) were supported on C@MTNC-FI by employing a microwave-assisted polyol process (MAPP). The obtained PtRu/C@MTNC-FI catalyst has 2.68 times higher mass activity towards methanol electrooxidation than that of the un-functionalized catalyst (PtRu/C@TNC) and 1.65 times higher mass activity than that of PtRu/C catalyst with over 25% increase in durability. The improved catalytic performance is due to several aspects including ultrafine crystals of TiO2 with abundant grain boundaries, Mo-functionalized interface with enhanced electron interactions, and core shell architecture with excellent electrical transport properties. This work suggests the potential application of an interface-functionalized crystalline material as a sustainable and clean energy solution.

The inception of flexible supercapacitors that can work steadily under large deformation has been a research hotspot in recent years. To improve the device's stability, one needs to find innovative solutions to inevitable delaminations of electroactive components, which are resulted by relative displacement under external force. Herein, an extensive all-in-one hydrogel-based supercapacitor is designed. Based on the special physical properties of hydrogels, the polypyrrole-polyvinyl alcohol/dilute sulphuric acid-polypyrrole (PHP) sandwiched device shows the harmonious mechanical and electrical properties. When the tensile strain of PHP reaches to 110%, the areal capacitance still maintains at 90%. Similarly, the high areal capacitance retention under compression and twisting also verifies that the PPy active layer tightly permeates and adheres to the PVA-H2SO4 electrolyte layer. In addition to the fascinating mechanical properties, the undetectable contact angle reveals a superhydrophilic surface which is beneficial to provide an easy access for electrolyte ions, thus enhancing the electrochemical performance. Moreover, a stable cycle performance (97% after 10000 cycles) is obtained due to the excellent water retention ability which prevents the loss of electrolyte. The maximum extended voltage window is 1 V with the power density of 500 μW cm−2 (the energy density of 6.94 μW h cm−2). These hydrogel-based supercapacitors can be immune to the harm caused by external forces and maintain good mechanical integrity and electrochemical stability. Developing the hydrogel-based supercapacitors can provide a fresh perspective on multifunction applications and herald a new territory for flexible energy storage devices.

Different calcination atmospheres of air, 50% oxygen (vs. N2) and pure oxygen have been used to prepare special LiNi0.8Co0.1Mn0.1O2 cathode materials to observe the influence of oxygen composition. To investigate the structure and electrochemical property of the samples using different oxygen compositions, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), cycling performance tests and electrochemical impedance spectroscopy (EIS) were carried out. XRD, SEM, and XPS results show that the sample made using higher oxygen composition has less cation mixing and lower levels of Ni2+. However, both samples have almost the same oxygen environments on their surfaces as well as micro-morphology and size. The sample with a higher oxygen composition shows better electrochemical performance. Interestingly, the electrochemical performance of the sample made using 50% oxygen is similar to that made with pure oxygen and much better than the sample made with air. It has a specific capacity of 202.4 mAh g−1 at 0.1C and a capacity retention of 85.2% after 300 cycles at 1C, which may be meaningful for balancing cost and performance.

Controllable synthesis strategies of the cost-effective and high-active non-noble metal bifunctional electrocatalysts for overall water splitting are imperatively required. Herein, the hierarchical heterostructure CoP3/NiMoO4 nanosheets on Ni foam (CoP3/NiMoO4–NF) are synthesized by hydrothermal, annealing and phosphorization treatment. The synergistic effect between CoP3 and NiMoO4 remarkably promotes the HER intrinsic activity. Moreover, the Ni foam promotes the vertical growth of well-aligned nanosheet arrays, which expose more active sites for HER and OER. The CoP3/NiMoO4–NF-2 (Co/Mo = 1/1) electrocatalyst reveals a low overpotential of 92 mV for HER and 347 mV for OER at 10 mA cm−2 in 1.0 M KOH. Especially, the CoP3/NiMoO4–NF-2 exhibits exceptional performance for overall water splitting which presents a low cell voltage of 1.57 V at 10 mA cm−2, and outstanding durability which could maintain over 12 h. The design strategy and controllable synthesis of the hierarchical heterostructure bifunctional electrocatalyst will be beneficial for efficient overall water splitting.

Microtubule plus-end tracking proteins (+TIPs) associate with growing microtubule plus ends and control microtubule dynamics and interactions with different cellular structures during cell division, cell migration and morphogenesis. Microtubule-associated RP/EB family member 2 (MAPRE2/EB2) is a highly conserved core component of +TIPs networks, but whether this molecule is required for mammalian meiotic progression is unknown. In this study, we investigated the expression and function of MAPRE2 during oocyte maturation. Our results showed that MAPRE2 was consistently expressed from germinal vesicle (GV) to metaphase II (MII) stages and that MAPRE2 was distributed in the cytoplasm of oocytes at GV stage and along the spindle at metaphase I (MI) and MII stages. Small interfering RNA-mediated knockdown of Mapre2 severely impaired microtubule stability, kinetochore-microtubule attachment, and chromosome alignment and subsequently caused spindle assembly checkpoint (SAC) activation and cyclin B1 nondegradation, leading to failure of chromosome segregation and first polar body extrusion. This study demonstrates for the first time that MAPRE2 plays an important role during mouse oocyte meiosis.

Recently, high performance energy storage devices are increasingly required in many new fields such as smartphone, pilotless automobile. Lithium-ion capacitors (LICs) have become the promising energy storage devices because of the higher power density, electrostatic capacity and long cycle life. Nevertheless, the limitation of the battery-type anode electrode and the capacitance-type cathode electrode with slow kinetics and low specific surface area leads to the LICs remaining lower energy density in high current density. In this report, a high performance LIC assembled by Mn3O4-graphene coupled with activated polyaniline-derived carbon (APDC) is firstly presented. Mn3O4-G composite material exhibits an outstanding invertible capacity of 489.8 mAh g−1 (at 1 A g−1) in a wide working window (0.01–3 V vs. Li/Li+) with an excellent coulombic efficiency in half cell, which is the highest capacitance reported for Mn3O4 so far. By utilization of Mn3O4-G composite as anode and APDC with the large surface of 1641.9 m2 g−1 as cathode, the assembled LIC of Mn3O4-G//APDC possesses an energy density of 97.2 Wh kg−1 at power density of 62.5 W kg−1, even at a relatively higher power density of 6250 W kg−1, its energy density can retain 5.0 Wh kg−1.

Li-rich (LR) layered oxide cathode for high-energy-density Li-ion batteries are receiving considerable attention. However, their intrinsic issues hinder the implementation of LR in simultaneously achieving higher energy and power densities. Herein, a dual-conductive surface control strategy is proposed. This surface layer contains an electronic conductive carbon nanotube (CNT) skeleton and an ionic conductive heteroepitaxial spinel structure, which endows the LR with the light-weight and self-standing characteristic. As evidenced by prolonged electrochemical and structural evolution, this surface layer can reduce polarization, restrain structural distortion and facilitate fast electronic/ionic diffusion. Density functional theory (DFT) calculations demonstrate a higher electron conductivity with a narrower band gap across the CNT/LR interface than that of pure LR, and reveal a highly connective Li+ percolation network and reduced Li+ migration energies for the layered-spinel heterogeneous interface. The designed LR cathode presents a high energy density (1077 Wh kg−1 at 0.1 C), excellent rate capability (195 mAh g−1 at 10 C) and superior cycle stability. When utilized as an additive-free cathode for high-voltage full-battery, impressive energy density (645 Wh kg−1 based on the cathode and anode) and ultra-long cycle life (maintaining 87% capacity after 400 cycles) can be achieved. These results and this dual-conductive surface control strategy provide an exciting perspective and avenue for the further development of high-performance electrode material.

Ti-based compounds are considered as attractive anode materials for sodium-ion capacitors (SICs) due to their favorable safety and stability. However, achieving more Na+ intercalated sites and fast sodiation kinetics in Ti-based anodes is still challenging. Herein, a facile strategy to promote the electrochemical properties of H-titanates by regulating their electronic structure and Na+ diffusion kinetics through thermal-induced interlayer defect engineering is developed. The targeted distorted quasi-layered H-titanate (Q-LT) with abundant interlayer defects exhibits superfast and stable cycle performance (97% capacity retention after 10,000 cycles at 25 C) in Na-ion half-cells. Applied in the high-working voltage (1.5–4.5 V) SICs as additive anodes, high energy density (124 Wh kg−1) and competitive cycle stability (88% capacity retained after 5000 fast cycles) are achieved. The thermal-induced structure evolution in layered H-titanate has been probed by in-situ X-ray diffraction. First-principles density functional theory calculations demonstrate that the Q-LT is equipped with lower coordinate Ti-O polyhedral, higher delocalized Ti-O environment, narrowed band gap and reduced Na+ migration energies; bond valence sum maps expose the continuous Na+ diffusion pathways within the interlayer of Q-LT. This work may offer a conceptual advance in the understanding of the structure-function-performance relationship of titanates for energy storage.

It is well known that high performance and long cycle stability are the most significant advantages of aqueous hybrid supercapacitors (AHSCs). However, low energy density has always restricted the development of AHSCs. Low energy density mainly comes from low voltage window and specific capacitance. If the above short slabs were solved, supercapacitors would be industrialized and widely used. Herein, A novel AHSC based on the optimized CoMoO4/MnO2 nanowires/Ni foam (KF-CMNWs) electrode and modified alkali-treated carbon nanotubes film (M-CNTF) with K3Fe(CN)6 in neutral aqueous Na2SO4 electrolyte is reported. The positive electrode material effectively improved its electrochemical performance through a synergistic effect. In addition, some redox mediators are added to a common electrolyte so that the electrolyte can also provide extra capacity. In order to enlarge the overall voltage window, sodium ions are absorbed on the alkali-treated carbon nanotubes film by a method of electroreduction, and the activity of HER is effectively reduced. A very high voltage of 1.4 V for the negative electrode in aqueous Na2SO4 electrolyte is reached. The AHSC has also a prominent long cycle life (>10,000 cycles; 96.8% capacitance retention) and presents a high energy density of 62.9 W h kg−1 at a power density of 984 W kg−1. More importantly, the full cell has a competitive voltage window (2.4 V). These excellent characteristics are expected to be applied in new energy storage devices.

High-capacity electrode materials are needed for electrochemical energy storage. Spinel (Ni0.4Co0.4Mn0.2)3O4 nanoparticles have been prepared by simplified and efficient coprecipitation in combination with thermal decomposition. As conversion-type anodes for lithium ion batteries (LIBs), the materials exhibit high capacities of 779 mAh g−1 after 600 cycles at the optimal current density of 0.5 A g−1. The enhanced cycling performance of (Ni0.4Co0.4Mn0.2)3O4 electrodes benefits from multiple metal species providing synergic effects in electrical processes, nanosize favorable for releasing stress and optimal rate lithiation for generating unique solid electrolyte interphase (SEI) with reactivation ability. And, the SEI layer is critical for the cycling properties. Optimal rate lithiation offers in designing long-lived electrodes. Additionally, the spinel materials are evaluated in sodium systems. The different capacity fading behaviors of the (Ni0.4Co0.4Mn0.2)3O4 electrodes between lithium and sodium ion cells are concerned.

One of the main issues for titanium-based anode materials is their poor electronic conductivity and this issue can affect their rate performance. For conquering this drawback, many approaches have been proposed. In this report, SrLi2Ti6O14 as one of the titanium-based anode materials is prepared via a facile sol–gel method and subsequently it has been composited with silver to elevate its electronic conductivity. Upon the analysis of electrochemical results, the SrLi2Ti6O14/Ag composite with 6 wt% Ag can deliver an initial capacity of 164.9 mAh g−1. After 50 cycles, the sample can still retain 154.6 mAh g−1 with 93.8% retention of the first cycle. Meanwhile, the SrLi2Ti6O14/Ag composite with 6 wt% Ag can also exhibit good rate capacities, even at 300 mA g−1, its capacity can be firmly kept at 140.0 mAh g−1. In addition, in situ X-ray diffraction characterization shows the structural reversibility of the SrLi2Ti6O14/Ag composite with 6 wt% Ag during cycling. All the electrochemical results indicate that the SrLi2Ti6O14/Ag composite with 6 wt% Ag can be a promising anode material for lithium ion batteries.

The microscopic surface plays a crucial impact on catalytic activity. Herein, the rough-surfaced chain-like palladium nanowires with many steps and inflections are successfully synthesized by a simple one-step reduction by sodium borohydride. The mechanism of bromide ions adsorbing and the oxygen etching to control the growth of chain-like nanowires is investigated. Furthermore, the effect of the pH values of system on the microscopic surface of palladium nanowires, especially on the roughness, is discussed in depth. The nanowires prepared at pH = 11 exhibit rougher surfaces with a diameter of 10–11 nm, and the relevant catalyst has higher electrochemical active area and excellent electrocatalytic performance for oxygen reduction reaction (ORR). Its half-wave potential in 0.5 mol L−1 H2SO4 solution is 80 mV more positive than Pd nanoparticles, slightly negative than Pt/C and the half-wave potential in 0.1 mol L−1 KOH solution is 50 mV more positive than the Pd nanoparticles, and is almost the same as Pt/C. The research result reported here will have important implications for designing palladium-based catalysts to increase their electrocatalytic ability.

The structures of materials have great influence on their properties. For materials with low electron conductivity, fast electron transport pathway can be constructed through carbon structure design. Here we report a simple but effective method to improve the electrochemical performances of Na3V2(PO4)3. Polyvinyl Pyrrolidone (PVP) can improve the viscosity of the precursor solution, thus forming aggregate structured material. In Na3V2(PO4)3, primary particles with a diameter of approximately 300 nm are aggregated through a special carbon network to form micro-sized secondary particles. This kind of structure will provide easy access for electron transportation, thereby improving electrochemical performance of the material. As a cathode material for sodium-ion batteries, Na3V2(PO4)3 delivers excellent rate (86.6 mAh g−1 at 30 C) and cycling performance (capacity retention of 88.4% after 2000 cycles at 10 C). The material also exhibits a specific capacity of 100.2 mAh g−1 at 5 C under 55 °C. The above-mentioned performance is far better than the control sample without PVP. The special carbon network provides electron transport channels which improves the electrochemical performance of the material. This method may provide new ideas for the preparation of phosphate materials.

Under over-increasing demand of advanced lithium-ion batteries (LIBs) for long-range electric vehicles (EVs), high-capacity transition metal oxide (TMO) negative electrodes for LIBs are thought as potential substitutes of traditional graphite anodes. A major barrier for TMO anodes is volumetric expansion during lithiation processes, leading to active material pulverization and falling off current collectors, which seriously deteriorates capacity retention. Herein, apart from conventional mechanical degradation, another capacity fading mechanism is revealed. Furthermore, the understanding is supported by an interesting cycling property. Firstly, NiCo2O4 with designed morphologies of nanoplates and microspheres are studied for the initial (de)lithiation and prolonged cycles. The morphology changes indicate solid electrolyte interphase (SEI) layer accumulating on the surface of electrodes and impeding the contact and reactions between lithium and active materials with a result of severe capacity loss. It can be understood as SEI layer insulating NiCo2O4, and if SEI film appropriately changes, high capacities can recovery. This conjecture is confirmed by following research of NiCo2O4 nanoparticles with amazing cycling performance prepared by a facile water-bath method. As LIB anodes, NiCo2O4 nanoparticles exhibit capacities of 1144 mAh g−1 at the initial discharging, 230 mAh g−1 at the 100th cycle and 661 mAh g−1 at the 500th cycle. The corresponding coulombic efficiency is of 73.1%, 98.4% and 99.5%, respectively. By TEM characterization in combination with electrochemical analysis, size-dependent SEI layer reactivation (from thick and unstable to thin and stable) is a key role on the dramatic capacity recovery.

We report an innovative strategy to prepare the porous N-doped graphene aerogel with an open structure and abundant defects by hydrothermal self-assembly of zeolitic imidazolate framework (ZIF)-8 and graphene oxide. The in-situ hydrothermal restructuring of ZIF-8 on graphene sheets plays a key role in the synthesis of the open structure and the uniform N-doping. The dissolution and restructuring of ZIF-8 on graphene oxide obviously suppress the stacking and reunion of graphene sheets to obtain the continuous macroporous structure. Moreover, the introduction of N and Zn creates the abundant N-doped sites and microporous structure. Its unique structure and composition improve the accessible surface area, the mass transfer diffusion, the dispersion and electronic structure of Pt nanoparticles, further resulting in the high catalytic performance of Pt-based catalyst for methanol oxidation reaction (MOR). Its MOR activity is about 1.8 times of commercial Pt/C, and its long cycling durability is improved by about 18.7% compared with commercial Pt/C. This work renders a promising method by utilizing ZIF-8 derivatives to synthesize the excellent N-doped carbon materials for electrochemical applications.

Self-supported NiMoO4 nanowire arrays (NNAs) are successfully grown on nickel foam (NF) via a simple one-step hydrothermal method and anneal treatment. Importantly, the in-situ growth method can reduce the contact resistance between the active material and current collector. It also can prevent the binder/conductive agent from “area of the deactivation” phenomenon. So, the design can effectively improve the electrochemical performance of electrode materials. In addition, a highly flexible carbon nanotubes (CNTs) film is also prepared by vacuum filtration step. Finally, an all-solid asymmetric supercapacitor (ASC) based on the optimized NiMoO4 nanowires electrode and carbon nanotube film (CNF) is assembled with PVA/KOH gel electrolyte. The ASC device presents outstanding electrochemical performance with a high energy density of 54.3 Wh kg−1 at a power density of 4344 W kg−1. The specific capacitance of the NNAs//CNF ASC remains 91.6% after 6000 cycles with a current density of 14 A g−1. At the same time, it also can continue to work under different bending states with almost constant performance. These results reveal that the NNAs//CNF ASC has great application prospect for flexible electronic fields.

With rapidly growing commercial markets of portable and flexible electronics, flexible supercapacitors (SCs) have become one of the most promising energy storage devices due to their unique characteristics. However, the low operating voltage and energy densities severely restrict their practical application. At the same time, the liquid-electrolyte has leak issues under deformation, resulting in short circuit of the device. Herein, an all-solid-state novel symmetric supercapacitor is designed based on nanostructured δ-MnO2@CNTs@sponge electrodes (MCS). The device presents a high voltage (0–2 V), remarkable cycle life (>10,000 cycles; 94.2% capacitance retention) and high energy (28.5 Wh kg−1 with power density of 2780 W kg−1). It also processes remarkable compression ability up to 80% with no obvious volume damage. After fully charged with four devices in series, it can easily light up a light-emitting diode (LED) under different compression states without electrolyte leakage. This strategy provides a novel device design method, and can be effectively applied to the future flexible electronic products.

Due to the sluggish interfacial kinetics, the energy density and cycle life of sodium-ion batteries (SIBs) suffer severely at subzero temperatures. Herein, to accelerate the interfacial charge transfer process and improve the low-temperature SIBs performance, a strategy by triggering Na+-solvent co-intercalation is proposed. Using hydrogen titanate nanowires (HT-NW) as a model, we found that the layer structure regulation with oxygen defects could trigger HT-NW presents a unique Na+-solvent co-intercalation behavior in the ether-based electrolyte at −25 °C according to ex-situ FTIR and XRD. By eliminating the Na+ desolvation process, Na+-solvent co-intercalation could effectively accelerate the Na+ diffusion kinetics and reduce the activation energy to 66.0 meV. Benefit from these ameliorations, the defective HT-NW delivers a high capacity of 238 mAh g−1 at −25 °C, which is equivalent to 89% of that at 25 °C. Besides, the defective HT-NW shows great superiority in cycle stability, maintaining capacity retention of 80.6% after 4200 cycles at 1.0 A g−1 at −25 °C. Moreover, at −25 °C, the defective HT-NW//Na3V2(PO4)3 full cell exhibits high energy density (119.1 Wh kg−1) and outstanding stability (94.5% after 1000 cycles at 1.0C). These findings reveal that the ion–solvent co-intercalation is highly feasible to improve the battery performance at low temperatures by accelerating charge transfer kinetics.

Spinel LiNi0.5Mn1.5O4 (LNMO) is widely utilized because of its high-energy-density and high-voltage. Unfortunately, there is still much research to be done for LNMO due to its poor structural stability. Here, a strategy is confirmed to stabilize LNMO via modulating interstitial sites. The interstitial 16c sites of the octahedron are partially occupied by Ni2+ to suppress the migration and dissolution of manganese ions upon electrochemical cycling and stabilize lithium-ion vacancies in the state of charge. Unexpectedly, this protocol not only suppresses the phase separation restraining the phase boundary dislocations and stress but also decreases the magnitude of cell volume change during cycling, which originates from the change in Ni redox couple energy states. This two-pronged modification strategy endows the cathode material with a lower charge transfer barrier and faster Li+ transfer kinetics, revealing superior electrochemical performance. The regulated cathode material remains robust after 900 cycles at 1 C and its capacity retention rate is 29% higher than that of the original sample. Our research is useful for providing a concrete example of how the electrochemical performance of spinel LNMO and other high voltage cathode materials can be enhanced.

Nitrogen-doped three-dimensional porous graphene frameworks (NGAs) are fabricated through a unique strategy of adopting the supramolecular assembly-assisted method with GO as building block, and supramolecular aggregate of self-assembled melamine and cyanuric acid as not only a “spacer” to suppress the re-stacking of graphene nanosheets but a self-sacrificial pore-forming agent as well as a nitrogen source leading to simultaneous N-doping. Supramolecular aggregates function as the structure-directing agent playing a vital role in generating the loose porous and free-stacking structure and guiding the formation of unique 3D architecture. The resulting metal-free NGA products possess high specific surface area, porous structure and free-stacking properties, and exhibit enhanced ORR performance in terms of positive half-wave potential which is only ∼43 mV lower than that of a commercial Pt/C, four-electron-transfer process, good durability and outstanding methanol poisoning tolerance. Besides, it also performs as a good support for Pt particles. Consequently, Pt/NGA catalyst displays impressive catalytic activity and stability towards efficient methanol electrooxidation reaction. This simple and robust synthetic strategy of 3D N-doped graphene has put forward a new prospect for rational synthesis of heteroatoms doped carbon materials for sustainable energy conversion applications.

Lithium sulfur battery, with higher gravimetric energy, is regarded as one of the promising next-generation energy storage devices. However, rapid capacity fading and poor rate capability under higher loading hinder its practical applications. Despite the encouraging progress achieved, the cost-effective solutions are still need to be sought for. Herein, a flower-like nitrogen-oxygen-doped carbon coated sulfur (F-S@NOC) composite was synthesized from a low-cost sulfur-containing organic ferro-compound, through a facile calcination and an in-situ oxidation process. The unique flower configuration is constructed by two-dimensional flake petal unit that not only expose more polar nitrogen/oxygen-containing functional groups for anchoring the dissolved intermediates of lithium polysulfides (LiPSs), but also facilitate improved electrochemical reaction kinetics since fast electron/Li+ transfer. Therefore, F-S@NOC demonstrates excellent electrochemical performances that a decay rate of 0.05% per cycle at 1C, and a high initial areal capacity of 4.49 mAh cm−2 at 0.2C, are obtained respectively under the sulfur loading of 3 and 4.6 mg cm−2.

The 3D N-doped graphene supported metal oxide has been synthesized as the sulfur host of Lithium-sulfur battery. A simple method of nanoparticles in-situ grown in aqueous solution is introduced. The SEM images and XRD spectra confirmed that nanoparticles with few tens of nanometers distributed on the surface of graphene sheet. The compound electrode showed an initial specific capacity of 1518 mA h g−1 at 0.2 C with a sulfur utilization of 90%. During 700 cycles, the capacity decay was only 0.03% per cycle. Even at a high rate of 2 C, the specific capacity can still be achieved 595 mA h g−1. The visual charge-discharge test showed that the composite electrode had strong adsorption effect on polysulfide vividly.

The Ni/Mn ratios are changed to improve rate performance of high-voltage spinel. LiNi0.5Mn1.5O4 and LiNi0.4Mn1.6O4 with annealed treatment are prepared. The structural evolutions during delithiation/lithiation are studied by in-situ XRD technique. It is found that the decrease of Ni/Mn ratios can change the structural evolutions from two-phase transformations to solid-solution reaction. The variations of electronic conductivity and lithium diffusivity during discharge are calculated by the galvanostatic intermittent titration technique. LiNi0.5Mn1.5O4 and LiNi0.4Mn1.6O4 have similar electronic conductivity and different lithium diffusivity. Lithium diffusion coefficients of LiNi0.5Mn1.5O4 with two-phase transformations are low due to limited lithium diffusion across the interface between two phases. For LiNi0.4Mn1.6O4, the single phase solid-solution reaction is beneficial to lithium diffusion. Attributed to higher lithium diffusivity, the rate performance of LiNi0.4Mn1.6O4 is obviously improved.

Na 3 V 2 (PO 4 ) 3 has aroused extensive attention as next generation cathode material for sodium-ion batteries because of its abundance, good thermal stability and special 3D Na + channel. In the current work, porous Na 3 V 2 (PO 4 ) 3 material is prepared by a simple freeze drying method followed by calcinations. Inside the porous material, Na 3 V 2 (PO 4 ) 3 particles are embedded in carbon matrix, thus forming facial electron channels and reducing Na + ion diffusion distance at the same time. Benefiting from the special porous structure, this material displays excellent rate capability of 92.8 mA h g −1 at high rate of 20 C. Equally impressive is the long cycling stability. 90.2% of the initial capacity is retained after 2000 cycles at 5 C. This kind of feasible preparation method and beneficial design provide a good strategy for other materials to improve electric conductivity and cycling stability.

It is highly desirable to improve the high voltage stabilities of cathode materials for Li-ion battery materials since it can deliver a higher reversible capacity at high cutoff voltage. Herein, we propose a novel facile strategy to generate La2O3-modified LiNi1/3Co1/3Mn1/3O2 with superior electrochemical performance in the voltage range of 2.5–4.5 V via a solid-state method. It can be observed that La2O3-modified LiNi1/3Co1/3Mn1/3O2 can greatly enhance the electrochemical performance due to the synergistic effect of ion doping and surface-modifying. La ions doping can alleviate the Li+/Ni2+ mixing, and substantially enhance the structure stability of LiNi1/3Co1/3Mn1/3O2 during charge/discharge cycles at high cutoff voltage. LaNi0.4Co0.6O3/LaMnO3.26 spreading on the surface layer is very useful in improving the diffusion of Li+ and inhibiting the particles from reacting with the electrolyte, enhancing the high voltage stabilities of the interface between electrode and electrolyte. The capacity retention of 0.7% (molar fraction) La2O3-modified LiNi1/3Co1/3Mn1/3O2 is 79.0% after 300 cycles compared to 61.7% for bare LiNi1/3Co1/3Mn1/3O2. And its discharge capacity at 10 C is 141.7 mAh g−1 in the voltage range of 2.5–4.5 V, which is higher than those of other samples. This work not only offers a facile novel strategy to achieve superior electrochemical performances of cathode materials but also presents some new insights into the stabilization mechanism of modified cathode materials during charge/discharge cycles or long-term storage at high cutoff voltage.

Fabricating high-performance anode materials is of great significance for the realization of advanced Na-ion batteries (SIBs). Poor rate capability and insufficient cycle stability are two main scientific issues urgently needing to be solved for sodium titanate (NaxTiyOz) anodes. In this paper, protonated titanate nanowire arrays are designed rationally as novel additive-free anodes for SIBs. Results reveal that the protonated strategy can controllablly regulate the lattice interlayer spacing of the titanate, which can not only effectively facilitate the Na-ion migration but also suppress the side reaction and inhibit the irreversible trapping of Na-ions in the crystal framework, leading to fast Na-ion diffusion kinetics. Moreover, the protonated titanate material experiences smaller changes in lattice parameters and unit-cell volume during long-term cycling than those of non-protonated material, resulting in less mechanical stresses and capacity loss in an anode. As expected, the protonated titanate material exhibits superior rate performance and ultralong lifespan when utilized as free-standing anode for SIB, remaining 85% capacity retention after 8000 cycles at 5.0 A g−1 (~ 23 C). When assembled as full cell with Na3V2(PO4)3 cathode, high energy density (262.3 Wh kg−1) and power density (1748.9 W kg−1), excellent rate capability and superior cycle stability (260 cycles, 86%) can be achieved.

Titanium nitride (TiN) as catalyst support has a very good application prospect due to its chemical stability, electrical conductivity and the metal-support interaction. But it is difficult to synthesize nano-TiN with the uniform dispersion by a simple method. This paper proposes a novel and easy strategy to address the problem. The mesoporous g-C3N4 has been synthesized and used as both nano-reactor and nitrogen source for the synthesis of nano-TiN evenly dispersed onto Vulcan XC-72. The uniform dispersion of nano-TiN is conducive to depositing and anchoring the PtRu nanoparticles, further increasing the long-time catalytic durability. Moreover, the electronic effect of TiN obviously improves the catalytic activity and the adsorbed CO tolerance ability of PtRu catalysts for methanol oxidation. Compared with the PtRu/C catalyst, the activity of PtRu/C-TiN for methanol oxidation has been increased by 47.3%. Meanwhile, its durability has been improved by 6.5% after 1000 cycles. In addition, this novel and easy method can be generalized to the synthesis of other nano-size nitrides. The applications of nano-size nitrides modified carbon black in other fields are also expected in the future.

Ni-rich cathode materials always suffer from serious side reaction and irreversible phase transition leading to capacity fading and thermal instability, which could be improved by surface coating and elemental doping. However, it is difficult and cumbersome to carry on the coating and doping at the same time. Herein, a facile method of bi-functional Ti modification has been employed on LiNi0.8Co0.15Al0.05O2 to enhance surface and structural stability via heterogeneous layer coating and bulk doping. The mechanism and synergistic effect of Ti modification has been investigated by XRD, XPS, SEM, TEM and the half-cell test in details. The existence of Ti occupancy in Ni site of the transition metal layer has been confirmed. Besides, a 22 nm heterogeneous layer has been detected on the particle surface and the composition has been analyzed. Ti bulk doping can reduce the cation mixing degree, and stabilize the lattice due to the pillar effect and charge compensation. Moreover, the heterogeneous coating layer could protect the cathode particles from hydrofluoric acid attack and reduce the decomposition of electrolyte during cycling. With the synergistic effects of heterogeneous layer coating and bulk doping, NCA-T2 exhibits the highest initial capacities of 162.9 and 182.4 mAh·g−1 at 1C and 0.1C, and the discharge capacity retentions of 1C cycling reach 85.0% after 200 cycles.