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The design and synthesis of three-dimensional (3D) covalent organic frameworks (COFs) with exceptional stability and high proton conductivity are critical for advancing high-temperature fuel cells but remain significantly challenging. In this study, thiadiazole groups were successfully incorporated into a novel 3D COF featuring a five-fold interpenetrated diamond network through a bottom-up self-assembly strategy. The proton conduction of the thiadiazole-based 3D COF (NUST-28) under anhydrous conditions reached up to 8.40 × 10−2 S cm−1 at 120 °C after phosphoric acid doping. Furthermore, the NUST-28 conductor demonstrated good stability at constant temperature and in cyclic experiments. This work paves the way for the design and construction of 3D COFs as platforms for fast ion transportation using reticular chemistry. [ABSTRACT FROM AUTHOR]

Solid-state electrolytes have garnered attention as potential replacements for liquid organic electrolytes in lithium-ion batteries due to their inherent nonflammability and mechanical stability. In this study, the effect of O doping on the transport properties of Li3PS4 solid electrolytes was investigated using ab initio molecular dynamics (AIMD) simulations. The P–O bond is shorter than the P–S bond after O doping, providing more space for Li-ion migration, and making it easier for Li ions to migrate between tetrahedral Li, which was originally somewhat restricted. The diffusion coefficients of Li ions increase in all XYZ directions after doping, with the most significant improvement observed in the Y direction. Radial distribution function and bond length tracking revealed fast Li ion migration, while the PS4 skeleton remained stable. Our results provide insights for the design of solid-state electrolytes through rational doping strategies. [ABSTRACT FROM AUTHOR]

Overall urea–water electrolysis has the potential to be employed in the purification of urea-containing wastewater and the production of hydrogen. However, the lack of cost-effective catalysts currently presents a significant obstacle to the further development of this technology. Through a simple template-directed selenium reaction in a novel type of highly active solution, an interface engineering strategy was designed to synthesize hollow CuSe nanocubes as an efficient bifunctional catalyst. The unique hollow CuSe nanocubes exhibit significant catalytic efficiency because of their larger electrolyte contact area and faster ion transport. In 1 M KOH with a 0.5 M urea electrolyte, CuSe/NF required an overpotential of 199 mV for HER and a potential of 1.38 V for UOR to achieve a current density of 10 mA cm−2. It can work stably for 24 h without significant degradation of activity at 10 mA cm−2, showing excellent durability and excellent stability. For overall urea–water electrolysis, it exhibits a remarkable activity with a low cell voltage of 1.61 V at 10 mA cm−2. Consequently, the design strategy of this unique hollow-structured CuSe provides a new insight to improve electrocatalytic performance and stability. [ABSTRACT FROM AUTHOR]

Pt2Ca nanoparticles with a mean size diameter of 6 nm can be prepared by heating K2PtCl6, CaH2, carbon black and KCl at 400–500 °C. A mechanism study suggests that the formation of the Pt2Ca phase at moderate temperature is enabled by the fast ion transport via the vacancies in the KCl–CaH2 solid solution. The Pt2Ca nanoparticles exhibit high performance for the oxygen reduction reaction in acid due to optimal adsorption energy of the oxygen intermediate. [ABSTRACT FROM AUTHOR]

The coupling of functionalized inorganic polyoxometalates with polymer electrolytes leads to considerably enhanced mechanical properties and faster ion transport (1.1 × 10−4 S cm−1) at room temperature. The assembled Li/Li symmetric cell displays excellent stability in a 3000 h cycling test and a Li/LiFePO4 cell exhibits superior cycling performance over 250 cycles. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs), as typical organic functional materials, have shown promising potential for application in photo/electrocatalysis, especially in the electrocatalytic CO2 reduction reaction (CO2RR). COFs can ensure effective CO2 adsorption and rapid mass transfer by virtue of controllable active sites and a large specific surface area. However, the inefficient interlayer conductivity of most COFs leads to a low electron transfer rate that restricts their practical applications. In this work, porphyrin-based covalent organic framework nanosheets (Por-COF) were vertically grown on the modified MXene surface for efficient electrocatalytic CO2RR. The large exposed MXene surface serves as a carrier "bridge" for dispersed COFs, which can endow heterojunctions with more active sites and fast ion transport channels. The optimal sample can exhibit superior efficient CO2RR performance, in which the faradaic efficiency of the CO2-to-CO conversion was 97.28% at −0.6 V vs. RHE, and the bias current density was −9.33 mA cm−2 at −1.0 V vs. RHE. [ABSTRACT FROM AUTHOR]

Atomic-level structure engineering has proven indispensable for fast ion transport kinetics. Herein, a unique framework of NiSe/Ni heterostructure with abundant heterointerface encapsulated hollow carbon spheres, namely NiSe/Ni@C, is synthesized as an anode for SIBs. The NiSe/Ni@C electrode delivers enhanced Na+ storage performance in terms of high specific capacity (490 mA h g−1) and excellent rate capability (546 mA h g−1) at a current of 5.0 A g−1 over 2000 cycles. This study can provide in-depth insights into the interface effect in hybrid structures and shed light on designing energy storage materials. [ABSTRACT FROM AUTHOR]

Porous CoSe2 nanosheets are prepared on nickel foam by the hydrothermal method using Se powder as the selenium source and a zeolitic imidazolate framework (ZIF-67) as the template. The impact of hydrothermal temperature on the morphological structure and electrochemical performance of the CoSe2 materials is investigated by characterization with HRTEM, SEM, XRD, and so on, and CV and GCD electrochemical tests. The results show that the CoSe2-180 electrode material exhibits excellent electrochemical performance, and its unique nanosheet array structure can provide a highly active surface, large superficial area and fast ion transport channels. This is mainly attributed to the fact that the reaction at different hydrothermal temperatures can provide different nanosheet structures. An ordered array structure is most clearly observed at a hydrothermal temperature of 180 °C. In addition, the incorporated ZIF-67 backbone provides a pathway for rapid electron transfer and accommodates the volume expansion of the selenide during charge–discharge processes. Due to the distinct porous structure, the CoSe2-180 electrode shows a high specific capacity of 269.4 mA h g−1 at 1 A g−1 and a distinguished retention rate of 83.7% at 20 A g−1. After 5000 cycles, the specific capacity can be maintained at 83.4% of the initial value. Moreover, the asymmetric supercapacitor (ASC) device is assembled with CoSe2-180 as the positive electrode. It displays favorable electrochemical performance with the maximum specific energy of 45.6 W h kg−1 at a specific power of 800.8 W kg−1 and an original capacitance retention rate of 81.5% after 5000 cycles. [ABSTRACT FROM AUTHOR]

An interfacial covalent bonding strategy is proposed for the synthesis of the MXene-stabilized Sb2Se3 nanotube hybrid. As an anode material, the prepared Sb2Se3@NC/MXene exhibits an enhanced sodium-ion battery performance in half/full batteries in terms of a high specific and cycling stability. [ABSTRACT FROM AUTHOR]

Na3V2(PO4)3 (NVP) with a NASICON structure serves as one of the most promising cathode materials for aqueous zinc-ion batteries (AZIBs) due to its stable crystal structure and fast ion mobility. Nevertheless, its electrochemical properties are still unsatisfactory because of its poor electrical conductivity. A simple hydrothermal method is used to prepare carbon-coated NVP (NVP-C) and N/S co-doped carbon-coated NVP (NVP-C-NS) composites. The results demonstrate that the NVP-C-NS composite exhibits superior capacity and rate capability. After 100 cycles at a high current density of 1000 mA g−1, the reversible capacity of the NVP-C-NS composite can reach 115 mA h g−1, while pure NVP-C is capable of achieving only 83 mA h g−1 at the same current density, and 94.8% of the capacity of the NVP-C-NS composite and only 90% of the NVP-C material are retained. The excellent electrochemical performance of the NVP-C-NS composite is mainly due to the high carbon content (13.08 wt% vs. NVP-C with 4.8 wt%.) and high conductivity (3.72 × 10−4 S cm−1vs. NVP-C with 1.20 × 10−4 S cm−1). The introduction of more active sites and defects after N/S doping and the increased specific surface area can provide a larger electrochemical contact surface for electrochemical reactions. Furthermore, the practicality of the NVP-C-NS//Zn battery is evaluated by lighting up LED bulbs. This work provides a reference for the development of Na3V2(PO4)3 as a cathode material for AZIBs. [ABSTRACT FROM AUTHOR]

In recent years, two-dimensional (2D) C-based materials have been intensively studied due to their excellent physicochemical properties. Meanwhile, extensive research has revealed that the electrical properties of layered materials can be tuned by changing the stacking pattern. However, the tuning of ion diffusion properties through stacking remains to be explored. In this work, bilayer C3B with different stackings as a lithium-ion battery anode material is systematically investigated by first-principles calculations. The calculated results show that bilayer C3B has better electronic properties (with a band gap of 0.44 eV to 0.54 eV) and enhanced bonding strength of Li (−2.82 to −3.27 eV) compared to monolayer C3B. Moreover, the intralayer migration barrier of Li can be regulated by stacking. Interestingly, the AB stacked configuration has the lowest migration barrier of 0.100 eV, which is significantly lower than those of other stacking configurations and monolayer C3B. Further studies revealed that the formation of fast ion diffusion channels in the AB stacked configuration is due to the combined effect of layer distance and in-plane charge transfer. These results offer a new strategy for the regulation of ion diffusion properties in 2D van der Waals materials. [ABSTRACT FROM AUTHOR]

Solid-state electrolyte (SSE) is crucial for a high-performance all-solid-state battery. Here, a new solid sodium electrolyte based on the ionic liquid EIMS-NaTFSI and one metal--organic framework (MOF) UiO-67-MIMS functionalized with zwitterion groups MIMS was obtained (UiO-67 and was assembled with 4,4'-biphenyldicarboxylate linker and cluster Zr6O4(OH)4) (EIMS = 1-(1-ethyl-3-imidazolio)propane-3-sulfonate, NaTFSI = sodium bis(trifluoromethanesulfonyl)imide, MIMS = 1-(1-mthyl-3-imidazolio)propane-3-sulfonate). By contacting and pairing EIMS-NaTFSI (abbreviated as EN-1) to the MIMS group on the framework, EN-1 was directed and arranged along the channels within UiO-67-MIMS, forming a solid composite EN-1@UiO-67-MIMS with Bragg scatter, i.e., a crystalline ionic liquid containing Na+ salts (NaTFSI). Such an ionic liquid EN-1@UiO-67-MIMS bearing crystalline MOF matrix showed and preserved fast ion conduction (1.02 x 10-2 S cm-1) at 150 °C even after 30 days, and exhibited 1--2 orders of magnitude higher conductivities than the bulk ionic liquid EN-1 within a wide temperature range, although the ion content in the latter was higher. The infinite pathway paved by the EN-1 arranged and contacted the MIMS along the channels within MOF well accounts for the fast ion transmission and the stability of the solid-state electrolyte. Such MOF-based crystalline ionic liquid provides a new strategy for developing high-performance solid-state electrolytes for ions. [ABSTRACT FROM AUTHOR]

A three-dimensional (3D) metal–organic framework containing Li-oxygen clusters, namely {[Li2(IPA)]·DMF}n (1) (H2IPA = isophthalic acid), has been constructed under solvothermal conditions. The Li-based MOF can be applied to lithium energy storage. For example, it shows good compatibility with a PEO (LiTFSI) solid-state polymer electrolyte (SSPE). The PEO (LiTFSI) with the MOF additive shows an ionic conductivity of 1.1 × 10−5 S cm−1 at room temperature. The 1D rhombic channels should facilitate lithium ion transportation and provide fast lithium ion pathway. Having assembled the PEO-MOF SSPE in a Li/Li symmetric cell and cycled at a current density of 0.1 mA cm−2, the polarization voltage was below 0.1 V during a 100 h test. The PEO-MOF SSPE was also used in a LiFePO4-Li full cell and a high specific capacity of 144 mA h g−1 was achieved. [ABSTRACT FROM AUTHOR]

Herein, we propose a solvent-assisted approach for preparing Ni-MOF microflowers with high specific capacitance and excellent rate capability as an electrode material for supercapacitors. The high electrochemical performance of this Ni-MOF is attributed to the fast ion transport and low electrical resistance resulting from its hierarchical flower-like structure, and the capacitance contribution from nickel hydroxide species. [ABSTRACT FROM AUTHOR]

The rational design of the unique morphology of particles has been considered as the key to improving the structural stability of spinel LiMn2O4 cathode materials for Li-ion batteries. Herein, a facile solid-state combustion process, combined with a Cr and Al co-doping approach, is proposed to prepare various LiCr0.01AlxMn1.99−xO4 (x ≤ 0.10) cathode materials with a good crystallinity. Cr and Al co-doping facilitates the formation of a single crystal truncated octahedral morphology. This endows the as-prepared LiCr0.01AlxMn1.99−xO4 with abundant {111} planes for Mn dissolution reduction and a few {100} and {110} planes for Li+ ion fast diffusion channels. Moreover, the introduction of Cr and Al elements with a stable electronic configuration further boosts the structural stability of the spinel LiMn2O4 owing to the relatively robust Al–O and Cr–O bonds compared with the Mn–O bond. Owing to these advantages, the optimal LiCr0.01Al0.05Mn1.94O4 delivers a good electrochemical performance with a high first discharge capacity of 118.5 mA h g−1 and a capacity retention of 70.8% after 1000 cycles at 1 C. Even at relatively high current rates of 15 and 20 C, a durable and prolonged cycling performance of up to 3000 cycles can be achieved. In addition, a high-temperature capacity retention of 72.1% is also maintained after 200 cycles at 5 C under 55 °C. This work provides potential candidates for developing long-life Li-ion batteries with a simultaneously high capacity. [ABSTRACT FROM AUTHOR]

A T-Nb2O5/CNT nanohybrid with short transmission paths, many active sites, and favorable mechanical flexibility can achieve the fast transportation of ions/electrons. The obtained nanohybrid with continuous conductive networks exhibited better lithium storage performance than sodium storage performance, due to lower resistance to the diffusion of Li+ ions crossing the carbon matrix. [ABSTRACT FROM AUTHOR]

Solid ionic conductors are one key component of all-solid-state batteries, and recent studies with lithium, sodium and potassium phosphidosilicates revealed remarkable ion conduction capabilities in these compounds. We report the synthesis and crystal structures of two quaternary phosphidosilicates with sodium and barium, which crystallize in new structure types. Na1.25Ba0.875Si3P5 contains layers of T3 supertetrahedra, while Na31Ba5Si52P83 forms defect T5 entities and contains Si–Si bonds and P3 trimers. Though T1-relaxometry data indicate a relatively low activation energy for Na+ migration of 0.16 eV, the crystal structures lack sufficient three-dimensional migration paths necessary for fast sodium ion conductvity. [ABSTRACT FROM AUTHOR]

Solid ionic conductors are one key component of all-solid-state batteries, and recent studies with lithium, sodium and potassium phosphidosilicates revealed remarkable ion conduction capabilities in these compounds. We report the synthesis and crystal structures of two quaternary phosphidosilicates with sodium and barium, which crystallize in new structure types. Na1.25Ba0.875Si3P5 contains layers of T3 supertetrahedra, while Na31Ba5Si52P83 forms defect T5 entities and contains Si–Si bonds and P3 trimers. Though T1-relaxometry data indicate a relatively low activation energy for Na+ migration of 0.16 eV, the crystal structures lack sufficient three-dimensional migration paths necessary for fast sodium ion conductvity. [ABSTRACT FROM AUTHOR]

Overlimiting current through a perm-selective membrane has been actively researched not only for the fundamental advancement of electrokinetics but also for energy/environmental applications such as electrodialysis, fuel cells, etc. In particular, various strategies were reported for the enhancement of overlimiting current because these applications demand efficient mass transport through the membrane. In this work, we presented in operando visualization and rigorous numerical study for the overlimiting current density enhancement using a pulsed electric field which is one of the most cost-effective parameters to be externally controlled. We clearly demonstrated that the current density had a peak value as a function of the pulse frequency and would suggest its correlation to a concentration profile and diffusion relaxation time (diff). As the pulse frequency was chosen which is similar to (diff)−1, the concentration profiles (i.e. established current paths) were maintained even in off-state due to remnant current paths helping the fast ion transportation. The fundamental evidence presented in this work would provide a strategical design of a perm-selective membrane system for a higher mass transportation efficiency. [ABSTRACT FROM AUTHOR]

A fluorescent probe with high selectivity for the detection of copper ions (Cu2+) is synthesized using 4-hydroxyhypoxidone, paraformaldehyde and proline via a one-step Mannich reaction. This Cu2+ fluorescent probe with large Stokes shift (129 nm) has good water solubility and could coordinate with Cu2+. It achieves fluorescence of this probe to be quenched linearly with the increasing concentration of Cu2+ from 10 to 800 nM. Since Cu2+ and pyrophosphate (PPi) have a stronger coordination ability, it promotes Cu2+ to coordinate with PPi preferentially and results in the fluorescence of the system being enhanced again. In this way, a novel fluorescence "turn-on" detection of PPi in the range from 2 to 40 μM within 2 min is developed using this Cu2+ fluorescent probe. It exhibits high selectivity in PPi detection towards other anions such as Cl−, NO3−, CO32−, PO43− and SO42−. It is worth noting that PPi can be hydrolyzed into phosphate (Pi) by alkaline phosphatase (ALP), and the coordination between Cu2+ and Pi is not as strong as that with the probe. Herein the fluorescence of the system can be quenched again after the addition of ALP. A fluorescence "turn-off" detection of ALP from 10 to 90 mU L−1 is achieved using this Cu2+ fluorescent probe. When it is used to detect ALP in serum samples, recoveries from 98.5% to 104.2% are obtained. [ABSTRACT FROM AUTHOR]

SnO2@C nanocomposites were synthesized using a citrate gel method in one step. Carbon has been used to increase the conductivity of pristine SnO2. The SnO2@C nanocomposites show nanoparticles sized in the range of 30–50 nm. A structural study by XRD shows the tetragonal rutile structure of SnO2. Furthermore, X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy confirm the existence of SnO2 along with carbon. The electrochemical performance was investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge–discharge measurements. The nanocomposite has been used as an anode material for lithium-ion batteries. Pristine SnO2 exhibited a discharge capacity of 1854 mA h g−1 and a corresponding charge capacity of 1038 mA h g−1 for the first cycle. The SnO2@C nanocomposite showed a discharge capacity of 2574 mA h g−1 and charge capacity of 1481 mA h g−1 for the first cycle. These results clearly show the effect of carbon incorporation in SnO2. Furthermore, the nanocomposite shows a discharge capacity as high as 725 mA h g−1 after 200 cycles at a current density of 50 mA g−1. Thus, the obtained capacity for the nanocomposites is much higher as compared to that for pristine SnO2, i.e., 119 mA h g−1 at 50 mA g−1 after 200 cycles. The higher capacity in the nanocomposites is due to the fast transport of electrons and easy transport of lithium ions due to the carbon in the nanocomposites. The SnO2@C nanocomposite anode exhibits superior cycling stability and rate capability due to its stable electrode structure. [ABSTRACT FROM AUTHOR]

A new kind of hollow carbon nanosphere with an ordered mesoporous shell structure is prepared and demonstrated to have improved performances in practical application areas involving fast ion transport. [ABSTRACT FROM AUTHOR]

Electrochemical energy storage performance of inorganic solid materials is highly dependent on the number of electroactive sites and their reactivity. However, it is difficult to control the number of electroactive sites and their reactivity during the solid crystallization process. Herein, we synthesized novel poorly crystalline La3+:Ni–Cl oxyhydroxide gels with sufficient electroactive sites and atomically homogeneous distribution of Ni2+, La3+, and Cl− ions. Their poorly crystalline structure may favor fast ion diffusion and Cl− ions help in the formation of electroactive sites, while La3+ ions enhance the ionic conductivity within these electrode materials. Used as positive materials for hybrid supercapacitors, La3+:Ni–Cl oxyhydroxide gels showed a high specific capacity of 203 mA h g−1, a value higher than most reported values of Ni(OH)2-based materials. This work represents a new strategy for the synthesis of new electrode materials with high capacity and fast ion diffusion kinetics. [ABSTRACT FROM AUTHOR]

Conjugated coordination polymers (CCPs), showing high conductivity, can be expected to be possibly applied in batteries, which, however, have not been well studied. Furthermore, CCPs are so unique that most of their chemical structures have not been well determined. Herein, a highly conductive CCP is reported for sodium-ion batteries, which shows high rate performance and high capacity retention of 84% even at 30C. What's more, the chemical structure is successfully revealed based on the structure variation during the electrochemical redox process. [ABSTRACT FROM AUTHOR]

BiSbS3@N-doped carbon (NC) core–shell nanorods were prepared through a simple preparation process. As anode materials for sodium-ion batteries (SIBs), BiSbS3@NC core–shell nanorods present excellent electrochemical performance with higher specific capacity and better rate capability compared with the unmodified pristine BiSbS3 nanorods. The BiSbS3@NC electrode delivers high sodium storage capacity (771.5 mA h g−1 in the 2nd cycle) and excellent rate performance (capacity of 518.4 mA h g−1 at 1000 mA g−1). The improvement in electrochemical performance results from the coated conductive NC layer which brings about fast ion/electron transfer and buffers volume expansion. The BiSbS3@NC core–shell nanorods are thus promising high performance anode materials for SIBs. [ABSTRACT FROM AUTHOR]

In this study, we discovered a method to synthesize large single crystals of Cu-BTC MOFs (Cu-s) with the assistance of a surfactant (PF-127) in an ethanol–water mixture solution. Single crystal and powder XRD (X-ray diffraction) measurements revealed that Cu-s, with the appearance of long rods, has the chemical formula Cu(BTC)3·H2O. We proposed the growth mechanism of Cu-s by a series of experiments and demonstrated that the addition of surfactant PF-127 can effectively inhibit the contact between Cu2+ ions and BTC ligands, which favoured the growth of Cu-s along the a-axis and suppressed the fast formation of porous Cu-BTC MOFs (HKUST-1). Considering that the photoactive properties of Cu-s and its relatively large size (an average length of up to ∼3 mm), we constructed a simple photo-detector device, showing excellent photo-sensing properties under illumination. [ABSTRACT FROM AUTHOR]

We present the first direct evidence of Na-ion mobility in sodium strontium silicate fast ion conductors, based on variable temperature 23Na solid state NMR spectroscopy and spin-lattice relaxation measurements. [ABSTRACT FROM AUTHOR]