Search

A functional electrolyte containing propyl 4-methylbenzenesulfonate (PMBS) additive is developed to improve the performance of the LiNi0.8Co0.1Mn0.1O2 (NCM811)/graphite pouch full cells, especially the cycling lifetime under low temperature. It is indicated that the addition of PMBS into the electrolyte facilitates the formation of stable and low impedance interfacial films of the NCM811 cathode and graphite anode due to the preferential decomposition of PMBS over solvent molecules. Compared to the cells without additives, the cells containing 2% PMBS exhibit enhanced performance, and the capacity retention rate increases from 55.97% to 87.20% after 1200 cycles at 25 °C. And under the temperature condition of −10 °C, the capacity retention rate increases from 55.37% to 98.02% after 100 cycles, indicating the unique effect of PMBS on the low-temperature cycling performance of high-nickel lithium-ion batteries. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Ab initio molecular dynamics (AIMD) simulations were performed to study the adsorption of the 1-hydroxyethane-1,1-diphosphonic acid (HEDP) molecule on the Fe (100) surface. Through molecular dynamics trajectory, changes in bond length and angle, density distribution, interaction region indicator (IRI) and electron localization function (ELF), the fundamental adsorption mechanism of HEDP on the iron surface was disclosed in detail. The oxygen atoms of four phosphonic acid groups of HEDP coordinated with the four Fe atoms form a stable adsorption on the iron (100) surface. The HEDP molecule is slightly distorted to bind with O atoms after adsorption. The bond length change tracking results show that the adsorption occurs very quickly. IRI analysis and Bader charges show that the electrostatic interaction between HEDP and the iron surface is strong and responsible for the stable adsorption state. The interaction between deprotonated O atoms and iron surface is stronger than that between protonated O atoms and iron surface. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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

The effects of 3-(phenylsulfonyl)propionitrile (PSPN) as a higher voltage bifunctional additive in the electrolyte on the formation of a solid electrolyte interface (SEI) on both LiCoO2 cathodes and graphite anodes are investigated using the half-cell method. The capacity retention of the Li/LiCoO2 and Li/graphite batteries with PSPN ranges from 10.12% and 74.81% to 79.19% and 92.58% after 200 cycles, respectively. The results of linear sweep voltammetry (LSV) and cyclic voltammetry (CV) demonstrate that PSPN is not only preferentially reduced but also easily oxidized during the charge–discharge process. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) analyses confirm that PSPN-containing SEI films can form simultaneously on both electrodes due to the interaction of nitrile (–C≡N) and sulfur–oxygen double bonds (S=O), providing protection to the LiCoO2 and graphite electrodes and improving the cycle performance at higher voltage. [ABSTRACT FROM AUTHOR]

A new polyethylene (PE)-supported ultra-thin blended polymer electrolyte based on polyvinylidene fluoride/hydroxyethyl cellulose (PVDF/HEC) was prepared by a simple dipping method for 5 V high voltage lithium-ion batteries (LIBs). The performances of the prepared membranes and the resulting GPEs were investigated by scanning electron microscopy, electrochemical impedance spectroscopy, linear potential sweep voltammetry, and charge–discharge cycling. The effects of the ratio of PVDF to HEC on the performance of the composite separator were further discussed. It was found that PE-supported polymer separators (PVDF : HEC = 3 : 1, by weight) present the best mechanical, thermal and wettability performance. The ionic conductivity of this GPE is 0.78 mS cm−1, which is much higher than that of PE separators (0.39 mS cm−1) at room temperature. The electrochemical stability of this GPE can reach up to 5.25 V (vs. Li/Li+). A LiNi0.5Mn1.5O4 cathode with this GPE exhibits a superior cycling stability and rate performance at room temperature. This suggests that the polyethylene (PE)-supported ultra-thin blended polymer electrolyte can be used for 5 V LIBs due to its good performance, low cost and strong operability. [ABSTRACT FROM AUTHOR]

A reconstructed graphite-like carbon (r-GC) micro/nano-structure with a higher capacity than and a comparative voltage plateau to commercial graphite anodes of lithium-ion batteries (LIBs) is synthesized from an expandable graphite raw material based on an up-down-up synthetic strategy. The expandable graphite powders are thermally expanded, hydrothermally cut, and ultrasonically crushed in turn to prepare a suspension containing nano-fragments with a graphitic plane nano-structure as a carbon precursor. Then, the r-GC micro/nano-structure can be obtained by stacking the graphite nano-fragments through spray drying the suspension and subsequently conducting a calcining treatment. This r-GC exhibits an initial capacity of 575.3 mA h g−1 at 0.1C and a reversible capacity of 508.4 mA h g−1 after 100 cycles. Especially, its comparative voltage plateau of commercial graphite is incapable for other known anode materials for LIBs. In the potential window of 0.3–0.01 V (vs. Li+/Li), a maximum capacity of approximately 432.1 mA h g−1, 1.16 times the theoretical capacity of graphite (372 mA h g−1), is obtained. The unique element stability, capacity, and voltage plateau indicate that the as-synthesized r-GC is a promising sheet-like anode material for LIBs. In addition, an embedded-defect and graphite-dominant graphite/graphene cooperative lithiation mechanism is proposed to elaborate the capacity and voltage plateau of r-GC. [ABSTRACT FROM AUTHOR]

Using the ab initio molecular metadynamics method, the adsorption of the structure of 1-hydroxyethane-1,1-diphosphonic acid (HEDP) on the Fe 3 O 4 surface and subsequent detachment of Fe atoms from the surface were simulated, and the dissolution mechanism by which HEDP dissolves Fe 3 O 4 scale at room temperature while other organic acids cannot was elucidated. The adsorbed hydroxyl groups, water and HEDP on the Fe 3 O 4 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 Fe 3 O 4 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 SrFe 12 O 19 (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.

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.