Abstract
The practical application of room-temperature Na-S batteries is hindered by the low sulfur utilization, inadequate rate capability and poor cycling performance. To circumvent these issues, ...here, we propose an electrocatalyst composite material comprising of N-doped nanocarbon and Fe
3
N. The multilayered porous network of the carbon accommodates large amounts of sulfur, decreases the detrimental effect of volume expansion, and stabilizes the electrodes structure during cycling. Experimental and theoretical results testify the Fe
3
N affinity to sodium polysulfides via Na-N and Fe-S bonds, leading to strong adsorption and fast dissociation of sodium polysulfides. With a sulfur content of 85 wt.%, the positive electrode tested at room-temperature in non-aqueous Na metal coin cell configuration delivers a reversible capacity of about 1165 mA h g
−1
at 167.5 mA g
−1
, satisfactory rate capability and stable capacity of about 696 mA h g
−1
for 2800 cycles at 8375 mA g
−1
.
The self‐exothermic in early stage of thermal runaway (TR) is blasting‐fuse for Li‐ion battery safety issues. The exothermic reaction between lithiated graphite (LiCx) and electrolyte accounts for ...onset of this behavior. However, preventing the deleterious reaction still encounters hurdles. Here, we manage to inhibit this reaction by passivating LiCx in real time via targeted repair of SEI. It is shown that 1,3,5‐trimethyl‐1,3,5‐tris(3,3,3‐trifluoropropyl)cyclotrisiloxane (D3F) can be triggered by LiCx to undergo ring‐opening polymerization at elevated temperature, so as to targeted repair of fractured SEI. Due to the high thermal stability of polymerized D3F, exothermic reaction between LiCx and electrolyte is inhibited. As a result, the self‐exothermic and TR trigger temperatures of pouch cell are increased from 159.6 and 194.2 °C to 300.5 and 329.7 °C. This work opens up a new avenue for designing functional additives to block initial exothermal reaction and inhibit TR in early stage.
Cyclotrisiloxane (D3F) is triggered by LiCx to undergo ring‐opening polymerization at elevated temperature (>80 °C), so as to targeted repair of cracked SEI. Consequently, the exothermic reaction of LiCx/electrolyte in early stage of thermal runaway is tamed by introducing D3F into routine carbonate electrolyte. Thus, the self‐exothermic and TR‐trigger temperatures of pouch cell with D3F are increased from 159.6 and 194.2 °C to 300.5 and 329.7 °C.
To obtain unbroken sulfides with delicate morphology from metal–organic frameworks (MOFs), a method for in situ growth of SiO2 protective layers on the surface of MOFs is proposed. This strategy can ...be successfully expanded to a variety of MOFs (ZIF‐67, Cu‐MOF, ZIF‐8, and PBA). Importantly, room‐temperature Na‐SeS2 batteries with Co9S8@SiO2/C prepared from ZIF‐67 as cathode host are assembled. Due to the hollow structure that can relieve the volume expansion and the co‐adsorption of sodium polysulfides/sodium polyselenides by Co9S8@SiO2/C, the SeS2/Co9S8@SiO2/C cathode shows excellent rate performance and Coulombic efficiency. In addition, ex situ X‐ray diffraction and in situ Raman results show that S8 and Se8 are generated after the discharge of SeS2, and Se8 is preferentially oxidized during charging.
A simple, effective, general strategy for the preparation of intact sulfide‐based hollow structures from metal–organic frameworks is presented. Benefiting from the structural and compositional advantages, the SeS2/Co9S8@SiO2/C composite cathode shows excellent electrochemical performance.
This research was carried out to solve the problem of the reasonable characterization of the working load of the main bearing of a large tunnel boring machine (TBM) under complex engineering ...geological conditions and equipment working statuses. A typical telescopic swing main drive system is considered, and a characterization approach based on acquired dynamic characteristic parameters is proposed. First, the axial load Fa, radial load Fr, overturning moment Mk, and torque T are considered as the load indexes of the main bearing. The main drive load model is then developed, and the load indexes are expressed by exploring the relationships between each load index and dynamic characteristic parameters such as the pressures, displacements of the hydraulic cylinders, and torques of the driving motors. Finally, the load indexes are characterized based on a subsea tunnel shield project, representative engineering geologies, and characteristic load inputs. The results indicate that by taking into account the variable attitude of the main drive system, each load index can be expressed as functions of the pressures, displacements of the hydraulic cylinders, and torques of the driving motors. According to the variation of the dynamic characteristic parameters, the load condition of the main bearing during application is accurately characterized. Different geologies are found to correspond to different load levels; the load under the dolomitic limestone and filling karst cave strata is found to be almost 1.5–1.9 times greater than that under diabase, while the torque is almost five times greater. The proposed load characterization approach provides an accurate load input conforming to engineering practice for the design and selection of the main bearing.
Enzymes have demonstrated great potential in the development of advanced electroanalysis devices due to their unique recognition and catalytic properties. However, unsatisfactory stability and ...limited electron communication of traditional enzyme sensors seriously hinder their large-scale application. In this work, a simple and effective method is proposed to improve the stability of enzyme sensors by using sodium hyaluronate (SH) as a protective film, MXene-Ti
3
C
2
/Glucose oxidase (GOD) as the reaction layer, and chitosan (CS) /reduced graphene oxide (rGO) as the adhesion layer. Results demonstrate that the repeatability of the designed sensor increased by 73.3% after improving the adhesion between the reaction layer and the current collector and that its response ability was greatly enhanced. Moreover, the long-term stability of the electrode surface with SH protective film proved to be superior than that without protective film, which suggests that this design can effectively improve the overall performance of the enzyme biosensor. This work proposed a multi-tier synergistic approach for improving the reliability of enzyme sensors.
Graphical abstract
Our proposed protective and adhesion layer can greatly improve the stability of enzyme sensor and realize the rapid detection of glucose in serum sample.
Despite wide‐temperature tolerance and high‐voltage compatibility, employing propylene carbonate (PC) as electrolyte in lithium‐ion batteries (LIBs) is hampered by solvent co‐intercalation and ...graphite exfoliation due to incompetent solvent‐derived solid electrolyte interphase (SEI). Herein, trifluoromethylbenzene (PhCF3), featuring both specific adsorption and anion attraction, is utilized to regulate the interfacial behaviors and construct anion‐induced SEI at low Li salts’ concentration (<1 m). The adsorbed PhCF3, showing surfactant effect on graphite surface, induces preferential accumulation and facilitated decomposition of bis(fluorosulfonyl)imide anions (FSI−) based on the adsorption–attraction–reduction mechanism. As a result, PhCF3 successfully ameliorates graphite exfoliation‐induced cell failure in PC‐based electrolyte and enables the practical operation of NCM613/graphite pouch cell with high reversibility at 4.35 V (96% capacity retention over 300 cycles at 0.5 C). This work constructs stable anion‐derived SEI at low concentration of Li salt by regulating anions–co‐solvents interaction and electrode/electrolyte interfacial chemistries.
Trifluoromethylbenzene (PhCF3), as surfactant, is introduced into propylene carbonate (PC)‐based electrolyte to regulate interfacial behaviors in lithium‐ion batteries. The adsorbed PhCF3 on graphite surface facilitates bis(fluorosulfonyl)imide anions’ (FSI−) accumulation and decomposition at graphite/electrolyte interface through the adsorption–attraction–reduction mechanism. As a result, the graphite is kinetically stabilized in medium‐concentrated PC electrolyte with high reversibility.
The multiaxial character of high-speed railway brake disc thermomechanical fatigue damage is studied in this work. Although the amplitudes and distributions of temperature, strain and stress are ...similar with uniform and rotating loading methods, the multiaxial behavior and out-of-phase failure status can only be revealed by the latter one. With the help of a multiaxial fatigue model, fatigue damage evaluation and fatigue life prediction are implemented, the contribution of a uniaxial fatigue parameter, multiaxial fatigue parameter and out-of-phase failure parameter to the total damage is discussed, and it is found that using the amplitude and distribution of temperature, stress and strain for fatigue evaluation will lead to an underestimation of brake disc thermomechanical fatigue damage. The results indicate that the brake disc thermomechanical fatigue damage belongs to a type of multiaxial fatigue. Using a uniaxial fatigue parameter causes around 14% underestimation of fatigue damage, while employing a multiaxial fatigue parameter without the consideration of out-of-phase failure will lead to an underestimation of about 5%. This work explains the importance of studying the thermomechanical fatigue damage of the brake disc from the perspective of multiaxial fatigue.
•VO2 nanoflowers are immobilized tightly on reduced grapheme oxide.•VO2 as a catalyst can enhance the reaction kinetics of sodium sulfur batteries.•The rGO/VO2/S electrode exhibits good cycle ...performance.
Developing high energy density room-temperature sodium sulfur (RT Na-S) batteries relies on the design of delicate structure that can be efficiently injected sulfur and enhance the cycle life of electrode active material. Herein, a three dimensional (3D) hierarchical cathode substrate with VO2 nanoflowers as catalyst in situ grown on reduced graphene oxide (rGO) for sulfur cathodes are designed and prepared. In this novel structure, the electronic conductivity of sulfur cathode can be greatly improved due to the high electrical conductivity of rGO substrate. More importantly, the catalytic effect of VO2 accelerates the conversion long-chain NaPSs to Na2S2/Na2S, and enhances the cycle capability, which can be validated by experimental data. As a result, the as-obtained rGO/VO2/S composites achieves an initial reversible capacity of 876.4 mA h g−1 at 0.2C. Moreover, the capacity of 156.1 mA h g−1 is demonstrated after long-cycling term of 1000 cycles at 2C and high cycle stability of only 0.07% capacity decay per cycle is exhibited.
Fluorinated solvents emerge as a promising strategy to improve performance of lithium metal batteries (LMBs). However, most of them are prone to produce corrosive HF and deteriorate electrode ...interface, inducing cathode‐to‐anode detrimental crossover of transition metal‐ions. Here, fluorinated aromatic hydrocarbons in dimethyl carbonate (DMC)‐based diluted highly concentrated electrolyte (DHCE) are employed to juggle formation of HF and LiF, enabling stable cycling of high‐voltage LiNi0.7Co0.1Mn0.2O2 (NCM712) and LiCoO2 (LCO). The nature of aromatics in this carbonate‐based DHCE makes them difficult to undergo β‐hydrogen assisted defluorination, evidencing by the high energy barrier and high bond energy of β‐sites hydrogen. The advanced DHCE restrains HF formation but strengthens LiF formation, which not only suppresses impedance growth, transition‐metal dissolution, and stress crack on the cathode, but achieves highly reversible Li stripping/plating with an outstanding average Coulombic efficiency up to 99.3%. The Li||NCM712 cell and Li||LCO cell both exhibits superior cycling stability at high operation voltage. Even under stringent conditions, the 4.4 V Li||NCM712 full battery retains >95% of the initial capacity over 100 cycles, advancing practical high‐voltage LMBs. This study designs an efficient electrolyte that generates robust electrode/electrolyte interphases and restrains by‐products formation spontaneously, thus shedding new light on electrolyte toward applicable LMBs.
Fluorinated molecules have been widely employed in high‐voltage lithium metal batteries, including fluoroethylene carbonate, 1,1,2,2‐tetrafluoroethyl‐2,2,3,3‐tetrafluoropropyl‐ether, etc. Nevertheless, they are prone to β‐hydrogen assisted defluorination to produce corrosive HF. In this study, fluorinated aromatics are introduced to carbonate electrolyte restrain HF formation but strengthen LiF formation, evidence by the high energy barrier and high bond energy of β‐sites hydrogen.
Display omitted
•Flame retardants are introduced into electrolytes through a bridge co-solvent.•The designed electrolyte possesses biphasic fire extinguishing capability.•2.9 Ah pouch cell shows only ...smoke under the severe nail penetration test.•The onset time of thermal runaway is delayed by 86 s under thermal abuse test.•The pouch cell exhibits a capacity retention of 87.5% after 1000 cycles at 0.5 C.
Safety issues of LIBs are closely related to flammable carbonate electrolytes. Traditional strategies for nonflammable electrolytes involve soluble and coordinative flame retardants with limited choices, which interact with lithium ions and lead to deteriorated electrochemical performance. Meanwhile, single dosage of flame retardants fails to suppress ignition of both gas and liquid phases during thermal runaway (TR) of LIBs, thus generating multi-stage fire. Here, we introduce two flame retardants with high and low vapor pressure into carbonate electrolyte through a bridge co-solvent to obtain a non-flammable electrolyte with biphasic fire extinguishing capability. The designed electrolyte not only affords excellent electrochemical performance, but also simultaneously suppresses the combustion of flammable gases and liquid electrolytes. The LiNi0.78Co0.10Mn0.12O2 | graphite pouch cell (2.90 Ah) empowered with such electrolyte exhibits outstanding cycling stability (87.5 % retention after 1000 cycles at 0.5 C) and shows only smoke under the severe nail penetration test as well as maximum temperature of TR reduced by 300 °C. What’s more, the onset time of TR is delayed by 86 s under thermal abuse test. Furthermore, the pouch cell after 1000 cycles remains flameless under the nail penetration test. This work provides a promising path for expanding the selectivity of flame retardants and offers new strategy for designing advanced non-flammable electrolytes for safe LIBs.
PDF
