A sodium bis(fluorosulfonyl)imide (NaFSI)-based multifunctional electrolyte is developed by partially replacing NaPF6 salt in the electrolyte to improve the wide temperature range working capability of NaNi1/3Fe1/3Mn1/3O2/hard carbon (NNFM111/HC) sodium-ion batteries (SIBs). The capacity retention of the SIBs with NaFSI-NaPF6 dual salt electrolyte increases from 47.2% to 75.5% after 250 cycles at 25 oC, and from 51.0% to 82.3% after 80 cycles at 45 oC, and the 1 C discharge capacity retention at the low temperature of -20 oC also increases 26.8%. In the single salt system, NaPF6 effectively passivate the aluminum foil and NaFSI passivate the electrode/electrolyte interface. The synergistic effect of NaPF6 and NaFSI greatly improves the battery performance in a wide temperature range. This NaFSI-based dual salt electrolyte also effectively overcomes the flaws when the SIBs using NaFSI or NaPF6 independently, and makes it more suitable for SIBs, indicating promising prospects in the commercial application of NNFM111/HC SIBs.
Lithium-sulfur batteries (LSBs) hold great potential as future energy storage technology, but their widespread application is hampered by the slow polysulfide conversion kinetics and the sulfur loss during cycling. In this study, we detail a one-step approach to growing tungsten phosphide (WP) nanoparticles on the surface of nitrogen and phosphorus co-doped carbon nanosheets (WP@NPC). We further demonstrate that this material provides outstanding performance as a multifunctional separator in LSBs, enabling higher sulfur utilization and exceptional rate performance. These excellent properties are associated with the abundance of lithium polysulfide (LiPS) adsorption and catalytic conversion sites and rapid ion transport capabilities. Experimental data and density functional theory calculations demonstrate tungsten to have a sulfophilic character while nitrogen and phosphorus provide lithiophilic sites that prevent the loss of LiPSs. Furthermore, WP regulates the LiPS catalytic conversion, accelerating the Li-S redox kinetics. As a result, LSBs containing a polypropylene separator coated with a WP@NPC layer show capacities close to 1500 mAh/g at 0.1C and coulombic efficiencies above 99.5 % at 3C. Batteries with high sulfur loading, 4.9 mg cm-2, are further produced to validate their superior cycling stability. Overall, this work demonstrates the use of multifunctional separators as an effective strategy to promote LSB performance.
Reactive radicals are crucial for activating inert and low-polarity C(sp3)-H bonds for the fabrication of high value-added products. Herein, novel single-crystal oxygen-rich bismuth oxybromide nanosheets (Bi4O5Br2 SCNs) with more than 85 % {10-1} facets exposure and oxygen defects were synthesized via a facile solvothermal route. The Bi4O5Br2 SCNs demonstrated excellent photocatalytic performance in the selective oxidation of toluene under blue light. The yield of benzaldehyde was 1876.66 µmol g-1 h-1, with a selectivity of approximately 90 %. Compared to that of polycrystalline Bi4O5Br2 nanosheets (Bi4O5Br2 PCNs), the activity of Bi4O5Br2 SCNs exhibit a 21-fold increase. Experimental studies and density functional theory (DFT) calculations have demonstrated that the defect Bi4O5Br2 (10-1) facets exhibits exceptional adsorption properties for O2 molecules. In addition, the single-crystal structure in the presence of surface defects significantly increases the separation and transport of photogenerated carriers, resulting in the effective activation of adsorbed O2 into superoxide radicals (â¢O2-). Subsequently, the positively charged phenylmethyl H is readily linked to the negatively charged superoxide radical anion, thereby activating the CH bond. This study offers a fresh perspective and valuable insights into the development of efficient molecular oxygen-activated photocatalysts and their application in the selective catalytic conversion of aromatic C(sp3)-H bonds.
Although hard carbon in propylene carbonate / ethylene carbonate (PC/EC)-based electrolytes possesses favorable electrochemical characteristics in rechargeable sodium-ion batteries, the underlying mechanism is still vague. Numerous hypotheses have been proposed to solve the puzzle, but none of them have satisfactorily unraveled the reason at the molecular-level. In this study, we firstly attempted to address this mystery through a profound insight into the disparity of the ion solvation/desolvation behavior in electrolyte. Combining the results of density functional theory (DFT) calculations and experiments, the work explains that compared to the sole PC-based electrolyte, Na+-EC4 molecules in the PC/EC-based electrolyte preferentially undergo reduction and contribute to the emergence of a more stable protective film on the surface of hard carbon, leading to the preferable durability and rate capability of the cell. Nevertheless, applying the ion solvation/desolvation model, it also reveals that Na+-(solvent)n molecules in the PC/EC-based electrolyte can achieve faster Na+ desolvation processes than in the PC-based electrolyte alone, contributing to the enhancement of charge transfer kinetics. This research holds great importance in uncovering the possible mechanism of the remarkable electrochemical- properties of hard carbon in PC/EC-based electrolytes, and advancing its practical utilization in future sodium-ion batteries.
The lithium-ion batteries (LIBs) with high nickel cathode have high specific energy, but as the nickel content in the cathode active material increases, batteries are suffering from temperature limitations, unstable performance, and transition metal dissolution during long cycling. In this work, a functional electrolyte with P-phenyl diisothiocyanate (PDITC) additive is developed to stabilize the performance of LiNi0.8 Co0.1 Mn0.1 O2 (NCM811)/graphite LIBs over a wide temperature range. Compared to the batteries without the additive, the capacity retention of the batteries with PDITC-containing electrolyte increases from 23 % to 74 % after 1400 cycles at 25 °C, and from 15 % to 85 % after 300 cycles at 45 °C. After being stored at 60 °C, the capacity retention rate and capacity recovery rate of the battery are also improved. In addition, the PDITC-containing battery has a higher discharge capacity at -20 °C, and the capacity retention rate increases from 79 % to 90 % after 500 cycles at 0 °C. Both theoretical calculations and spectroscopic results demonstrate that PDITC is involved in constructing a dense interphase, inhibiting the decomposition of the electrolyte and reducing the interfacial impedance. The application of PDITC provides a new strategy to improve the wide-temperature performance of the NCM811/graphite LIBs.
Today, the commercial application of silicon oxides (SiOx, 1 < x < 2) in lithium-ion batteries (LIBs) still faces the challenge of rapid performance degradation. In this work, by integrating hydrothermal and physicomechanical processes, water-soluble locust bean gum (LBG) and xanthan gum (XG) are utilized to in situ form an LBG@XG binder network to improve the performance of SiOx/C anodes. As a synergy of LBG and XG polysaccharides in hydrogel polymerization, LBG@XG can tightly wrap around SiOx/C particles to prevent plate damage. The flexible SiOx/C anode with the LBG@XG binder exhibits capacity retentions of 74.1% and 76.4% after 1000 cycles at 0.5 A g-1 and 1 A g-1, respectively. The full battery capacity remains stable for 100 cycles at 1 C and the rate performance is excellent (103 mAh g-1 at 3 C). This LBG@XG is demonstrated to be highly electronegative and has a strong attraction to SiOx/C particles, thereby reducing the expansion and increasing the stability of the SiOx/C anodes when coupled with the flexible binder network. In addition to the promising LBG@XG binder, this work also provides a research idea for developing green water-based binders suitable for application in the SiOx/C anodes of LIBs.
Using the ab initio molecular metadynamics method, the adsorption of the structure of 1-hydroxyethane-1,1-diphosphonic acid (HEDP) on the Fe3O4 surface and subsequent detachment of Fe atoms from the surface were simulated, and the dissolution mechanism by which HEDP dissolves Fe3O4 scale at room temperature while other organic acids cannot was elucidated. The adsorbed hydroxyl groups, water and HEDP on the Fe3O4 surface play a synergistic role in detaching the Fe ions, which increases the coordination number of the Fe atoms and weakens the original Fe-O bond strength. In addition, the strong coordination ability and flexible molecular structure of HEDP also facilitate dissolution of Fe3O4 scale by breaking down the chemical bonds and forming Fe-HEDP complexes. The free energy surface for the dissolution reaction shows a low barrier, and the descaling reaction is easily accomplished.
Lithium-sulfur batteries (LSBs) have emerged as one of the ideal contenders for the upcoming generation of high energy storage devices due to their superb energy density. Nonetheless, the shuttle effect generated by intermediate lithium polysulfides (LiPSs) during cell cycling brings about capacity degradation and poor cycling stability of LSBs. Here, a versatile SrFe12O19 (FSO) and acetylene black (AB) modified PP separator is first presented to inhibit the shuttle effect. Thanks to the strong chemical interaction of Fe and Sr with polysulphides in FSO, it can trap LiPSs and provide catalytic sites for their conversion. Therefore, the cell using the FSO/AB@PP separator has a high initial discharge specific capacity (930 mA h g-1) at 2 C and lasts for 1000 cycles with a remarkably low fading rate (0.036% per cycle), while those using PE and AB@PP separators have inferior initial specific capacities (255 mA h g-1 and 652 mA h g-1, respectively) and fail within 600 cycles. This work proposes a novel approach for addressing the shuttle of LiPSs from a bimetallic oxide modified separator.
As an important descaling agent, 1-hydroxyethane-1,1-diphosphonic acid (HEDP) is capable of dissolving calcium sulfate scale when the pH of HEDP solution is adjusted from acidic to weakly alkaline. The molecular structures of Ca-HEDP complexes were determined to understand the impact of pH on the dissolution of calcium sulfate scale. The structures of the complexes revealed that the two phosphonic acid groups and the hydroxyl group of HEDP each provide one O atom to coordinate with the Ca ion to form a stable three-coordinate configuration under alkaline conditions. The electronic structures were investigated by interaction region indicator analysis, atoms in molecules analysis, electron localization function and natural population analysis. The deprotonation of the phosphonic acid group enhances the binding of coordinated O atoms and Ca ions as the pH increases, and weak alkalinity is the optimal process condition as strong alkaline conditions result in the precipitation of hydroxide and Ca ions.
FeP has emerged as an appealing anode material for lithium-ion batteries (LIBs) thanks to its high theoretical capacity, safe voltage platform and rich resources. Nevertheless, sluggish charge transfer kinetics, inevitable volume expansion and easy agglomeration of active materials limit its practical applications. Here, novel Cu-doped FeP@C was synthesized by a synergistic strategy of metal doping and in situ carbon encapsulation. The optimized Cu-doped FeP@C anode demonstrates a highly reversible specific capacity (920 mAh g-1 at 0.05 A g-1), superb rate performance (345 mAh g-1 at 5 A g-1) and long-term cycle stability (340 mAh g-1 at 2 A g-1 after 600 cycles). The electrochemical mechanism was investigated by cyclic voltammetry, kinetic analysis and DFT calculations. The results reveal that carbon frameworks can improve the conductivity and slow down the volume expansion, with highly dispersed FeP facilitating Li-ion migration during the charge and discharge processes. Additionally, Cu doping leads to rearrangement of the charge density and an additional lattice distortion in FeP, which boosts the electron mobility and enriches the surface-active sites, promoting electrochemical reaction and charge storage. This study presents a feasible and effective design for developing transition metal phosphate (TMP) anodes for high-performance LIBs.
A new subtype of nano-impacts by emulsion droplets via reorganization of the electric double layer (EDL) at the liquid/liquid interface (LLI) is reported. This subtype shows anodic, bipolar, and cathodic transient currents with a potential of zero charge (PZC) dependence, revealing the non-faradic characteristic of single fusion impacts. In addition, the absolute integrated mean charge is proportional to the Galvani potential at the ITIES, indicating that the EDL at the LLI may obey the discrete Helmholtz model. The exact PZC point is interpolated from the fitting curve, and the droplet size distribution is estimated from the integrated charge distribution. Moreover, the different values of Epzc between single fusion impacts of MgCl2 droplets and pure water droplets is due to the specific absorption between Mg2+ and antagonistic anion in the organic phase. The influence of the concentration of the supporting electrolyte is also investigated. The above work gives physicochemical insights into the EDL at the micropipette-supported LLI and provides potential application to measure micro/nanoscale heterogeneous media without catalytic, reactive, or charge-transfer activity via impact experiments at LLI.
Electrolytes , Water , Electrodes , Emulsions , Anions
Constructing oxygen vacancies (OVs) with desired concentration and stability on the surfaces of semiconductors has been demonstrated to be a powerful tactic to enhance their photocatalytic performances. Nevertheless, forming OVs usually requires rigorous conditions, and OVs harshly suffer from deactivation during photoreaction. Herein, a facile strategy is developed to introduce surface OVs with tunable concentrations and long-term stability in bismuth-based semiconductors (BBS) through organic small-molecule surface-bonding. Taking I-doped BiOCl (I-BiOCl) as a model photocatalyst and catechol and its derivatives as ligands, a series of organic/I-BiOCl bonded hybrid photocatalysts are successfully synthesized. Compared with I-BiOCl, hybrid photocatalysts exhibited substantially enhanced catalytic activity toward multiple contaminants removal. Experimental characterizations and DFT calculations reveal a strong interfacial interaction between organic ligands and BBS through the formation of BiOC bonds, which lengthen Bi-O bonds within [Bi2O2]2+ structural units and reduce the formation energy of OVs, facilitating the escape of lattice O atoms and thus producing abundant surface OVs. More importantly, the concentration of OVs can be easily regulated by controlling the number of organic ligands, and the OVs exhibit high stability during photoreaction, attributing to the existence of high-valence-state Bi(3+x)+ that is near the OVs, which would not be re-oxidized by oxidative species like the low-valence-state Bi(3-x)+, that is, they would not be reset to original Bi3+. As a verification of its universality, the surface bonded strategy has been successfully extended to other BBS.
A new type of nano-SnFe2O4 with stable lattice-oxygen and abundant surface defects anchored on ultra-thin graphene-like porous carbon networks (SFO@C) is prepared for the first time by an interesting freezing crystallization salt template method. The functional composite has excellent rate performance and long-term cycle stability for lithium-ion battery (LIB) anodes due to the stable structure, improved conductivity, and shortened migrating distance for lithium-ions, which are derived from the higher lattice-oxygen of SnFe2O4, abundant porous carbon networks and surface defects, and smaller nanoparticles. Under the ultra-high current density of 10, 15, and 20 A g-1 cycling for 1000 times, the SFO@C can provide high reversible capacities of 522.2, 362.5, and 361.1 mAh g-1, respectively. The lithium-ion storage mechanism of the composite was systematically studied for the first time by in situ X-ray diffraction (XRD), ex situ XRD and scanning electron microscopy (SEM), and density functional theory (DFT) calculations. The results indicate that the existence of Li2O and metallic Fe during the lithiation/delithiation process is a key reason for reducing the initial lithium-ion storage reversibility but increasing the rate performance and capacity stability in the subsequent cycles. DFT calculations show that lithium-ions are more easily adsorbed on the (111) crystal plane with a much lower adsorption energy of -7.61 eV than other planes, and the Fe element is the main acceptor of electrons. Moreover, the kinetics investigation indicates that the lithium-ion intercalation and deintercalation in SFO@C are mainly controlled by the pseudocapacitance behavior, which is favorable to enhancing the rate performance. The research provides a new strategy for designing LIB electrode materials with a stable structure and outstanding lithium-ion storage performance.
1,2,3,4-Tetrakis(2-cyanoethoxy)butane (TCEB) is first evaluated as a functional electrolyte additive to increase the charge cutoff voltage and energy density of pouch LiCO2 (LCO)/artificial graphite (AG) lithium-ion batteries (LIBs) at a high temperature of 45 °C. The charge (0.7 C) and discharge (1 C) tests show that TCEB effectively improves the cycle stability of cells under a high charge cutoff voltage of 4.5 V. At 25 °C, the capacity retention of the cells with TCEB increases from 0.0% to 72.1% after 1200 cycles. At 45 °C, the capacity retention of the cells without TCEB after 50 cycles is close to 0.0%, while the capacity retention of the cells with TCEB is still 81.6%, even after 350 cycles. The spectroscopic characterization results demonstrate that the TCEB electrolyte additive participates in the construction of a self-repair electrode/electrolyte interface film. Subsequently, low impedance and strong protective layers are formed on the two electrode surfaces. The quantitative analysis results and a theoretical calculation also show that TCEB effectively inhibits the dissolution of Co3+ and maintains the structural integrity of electrode materials. These results indicate that TCEB endows LIBs with excellent cycle stability and is a promising electrolyte additive for the high-voltage and high-temperature conditions of LCO-based LIBs.
A silicon suboxide-carbon (SiO x /C, 1 ≤ x ≤ 2) composite anode of lithium-ion batteries (LIBs) with enhanced performance is prepared using an aqueous multicomponent binder technology. Considering the adhesive force, electrolyte absorption, and stability, different binders including sodium alginate (SA), polyacrylamide gel (PAM), polytetrafluoroethylene (PTFE), and their composites are evaluated. It is indicated that compared to other anodes with single- or multicomponent binders, the SiO x /C composite anode with PAM/SA/PTFE663 (PSAP663) binders exhibits strong adhesion, moderate electrolyte absorption ability, and a specific capacity of 427 mA h g-1 charge-discharged at 0.5 A g-1 after 300 cycles. The improvement of electrochemical performance is attributed to the comprehensive effects of composite binders, including the adhesion of active substances, surface protection, solution adsorption, conductive path, and so on. These results show that the PSAP663 binder has promising potential for application, which not only gives alternative practical schemes of the green binders for the SiO x /C anodes but also provides ideas to develop a high-performance adhesive technology for LIBs.
The development of efficient, effective, and large-scale treatment methods to address high-risk emerging contaminants (ECs) is a growing challenge in environmental remediation. Herein, a novel parallel coupling strategy of adsorption separation and photodegradation regeneration (parallel ASPR) is proposed; subsequently, an adsorptive photocatalyst (Zn-doped BiOI) is designed to demonstrate how to effectively eliminate fluoroquinolones (FQs) from water with the proposed ASPR scheme. Compared with pure BiOI, the addition of Zn2+ during synthesis has a significant influence on the morphology and structure of the products, resulting in Zn-doped BiOI samples with up to 5 times the specific surface area, 32 times the adsorption capacity, and 20 times the photocurrent intensity. The optimized Zn-doped BiOI sample has an excellent adsorption efficiency for FQs with a removal rate that exceeds 95% after 5 min of adsorption for all 6 tested FQ antibiotics. Then the adsorbed contaminants can be effectively degraded during the later visible-light irradiation process, and the adsorbent can be regenerated synchronously, showing excellent ASPR cycling performances. The mechanisms of rapid adsorption and photocatalysis were explored via material characterizations, adsorption models, density functional theory calculations, and photogenerated species analyses. The results reveal that the enhanced adsorption of Zn-doped BiOI for FQs is due to its high specific surface area, coordination-based chemical adsorption, and surface electrostatic attraction, while its superior visible-light photodegradation performance is mainly ascribed to its strong redox ability, abundant surface oxygen vacancies, and enhanced photogenerated carrier separation efficiency.
Fluoroquinolones , Light , Adsorption , Catalysis , Photolysis
In order to improve the electrochemical performance and relieve volume expansion of pure SnFe2O4 anode for lithium-ion batteries (LIBs), we synthesized a novel ZnO/SnFe2O4/nitrogen-doped carbon composites (ZSFO/NC) with flake-like polyhedron morphology by using ZIF-8 as a sacrificial template. Remarkably, it exhibited an initial charge/discharge capacities of 1078.3/1507.5 mAh g-1 with a high initial coulombic efficiency (ICE) of 71.2%, and maintained a steady charge/discharge capacities of 1495.7/1511.8 mAh g-1 at 0.2 A g-1 after 300 cycles. The excellent rate performance of 435.6 mAh g-1 at a higher current density of 10.0 A g-1 and superior reversible capacity of 532.3/536.2 mAh g-1 after 500 cycles at 2.0 A g-1 were obtained. It revealed that the nitrogen-doped carbon matrix and peculiar structure of ZSFO/NC not only effectively buffered large volume expansion upon (de)lithiation through the synergistic interface action between ZnO, SnFe2O4 and NC, but also improved capacity of the composite by large contribution of surface pseudo-capacitance. The excellent charge-discharge performance showed that ZSFO/NC composite has a great potential for LIBs due to the synergistic effect of the multi-components.
An ion transfer-resolved configuration has been introduced to study the fusion impact of a tiny (femtoliter) water-in-oil droplet probed at the micro liquid/liquid (L/L) interface. A periodic linear potential signal with a high frequency is applied in this configuration, and typical (facilitated) ion transfer voltammograms and capacitive voltammograms of single fusion events have been obtained. The responses with voltammetric characteristics allow us to identify ion transfer potentials and elucidate the mechanism in single fusion events. The aqueous droplets encapsulating femtomoles of different quaternary ammonium ions are successfully tracked by fusing with the L/L interface and are identified by their ion transfer potentials. In addition, a capacitive fusion impact is recorded in the obtained current response when no biphasic ion translocation event occurs during a single fusion process, revealing a new mechanism of charge exchange between the electrode surface and polarized interface in the alternating electric field. In addition, a single fusion impact revealed by the facilitating ion transfer is reported, and the obvious discrepancy of fusion event voltammograms with and without ionophore participation is established. By providing new physiochemical insights, this study enables extra trace analysis at the femtomole scale and provides a possible method to electrochemically characterize micro-/nanoscale heterogeneous media.
Increasing the upper cutoff voltage is capable of achieving higher charge capacity, whereas this strategy always causes a dramatic degradation of cycling and thermal stability. In this study, we first report spinel LiNi0.5Mn1.5O4-modified LiCoO2 (LiCoO2@LiNi0.5Mn1.5O4) as an outstanding cathode material. LiCoO2@LiNi0.5Mn1.5O4 retains capacity retention of 81.4% in a full cell between 4.45 and 3.00 V after 400 cycles at 0.5 C and is superior to 55.3% of pure LiCoO2. In situ X-ray diffraction at an upper cutoff voltage of 4.75 V in combination with differential capacity curve reveals that the promoted cycling performance is ascribed to a delay of O3 â H1-3 â O1 phase transitions and a suppression of cobalt dissolution-induced side reactions. Moreover, LiNi0.5Mn1.5O4 modification improves the thermal stability of LiCoO2 by depressing the release of oxygen and the formation of cobalt dendrites.
Three-dimensional nitrogen-sulfur codoped layered porous carbon nanosheets (3D-NSCNs) with sulfur-regulated nitrogen content are constructed as a high-performance anode material for potassium-ion batteries (KIBs) through a gel and nitrogen-sulfur codoping process. Compared with the sample without sulfur doping, the 3D-NSCNs reveal enhanced electrical conductivity, specific surface area, and pyrrolic (N-5) and pyridinic (N-6) nitrogen contents, all of which are beneficial for increased electrochemical performances. After 200 cycles at a current density of 100 mA g-1, the 3D-NSCNs anode exhibits a specific capacity of 254.9 mA h g-1. After 2900 cycles at a higher charge-discharge current density of 1 A g-1, the specific capacity is still 171.1 mA g-1, and the capacity retention is 78.9%, indicating the application potential of the as-synthesized 3D-NSCNs as an anode material for KIBs. Domination by a surface-driven mechanism is proposed to explain the excellent rate and cycle performances and can also be validated by galvanostatic intermittent titration results, which show that the K+ diffusion coefficient in the 3D-NSCNs is improved after nitrogen-sulfur doping. This work demonstrates a new strategy to improve the electrochemical properties of carbon-based K-storage materials by increasing the N-5 and N-6 contents through sulfur doping while also producing micropores to increase the number of active sites.
