Increase Of Interface Resistance Research Articles

Vanadium-doped Li6.7La3Zr1.7V0.3O12 and PVDF-HFP enhanced the ionic conductivity and cycling stability of composite solid electrolytes for All-Solid-State lithium batteries

Solid electrolytes receive widespread attention due to their high safety, high energy density and simplicity of processing. However, the poor interface stability between the solid electrolyte and the electrode leads to a significant increase in interface resistance, greatly reducing the electrochemical performance of lithium-ion batteries (LIBs). Here we designed and prepared a new type of solid composite electrolytes (SCEs), which were composed of poly (ethylene oxide) (PEO) blended with poly (vinylidene fluoride-hexafluoro propylene) (PVDF-HFP) and doped with cubic phase Li6.7La3Zr1.7V0.3O12 (LLZVO) particles. Compared with our previous work, the addition of PVDF-HFP can further reduce the crystallinity of PEO, limit the formation of lithium dendrites, and make the electrolyte/electrode interface more stable. The SCEs had better ionic conductivity of 2.04 × 10-4 S cm−1 and 2.03 × 10-3 S cm−1 at 30 ℃ and 80 ℃, respectively, and the Li/SCEs/Li symmetrical battery cycled for 1800 h without short circuit. Moreover, the coulombic efficiency of LiFePO4/SCEs/Li battery remained at 98 % after 300 cycles. This opens up a new direction for the research of garnet-type composite solid electrolytes with lower interface resistance.

Failure mechanisms at the Li anode/solid electrolyte interface during Li stripping

A precipitous increase in the resistance of the Li metal/solid electrolyte interface can occur during the stripping of Li from the electrode. This electrical failure has been typically attributed to the loss of contact associated with the growth of voids in the Li anode at the electrode/electrolyte interface. We first analyse the growth of voids at the electrode/electrolyte interface using a framework that couples the power-law creep deformation of the Li electrode and the flux of Li+ through a single-ion conductor solid electrolyte. We show that a modified Butler-Volmer kinetics where the local interfacial resistance decreases due to dislocations within the creeping Li predicts that voids indeed grow around interfacial sub-micron impurity particles. Consistent with observations that the increase in resistance of interface occurs earlier for thinner electrodes, we predict that the propensity of void growth increases with decreasing electrode thickness, and this is associated with the mechanical constraint imposed by the current collector. However, in contrast to the observations and rather counterintuitively, this analysis predicts that the cell voltage decreases with void growth. Consequently, we investigate an alternative mechanism of contact loss due to the deposition of insulating solute atoms within the Li electrode onto the interface. Predictions of the rising cell voltage using this analysis are in broad agreement with measurements. This leads us to hypothesize that although void growth occurs at the interface it is not the primary mechanism leading to the increase in interface resistance during stripping.

ZnS nanoparticles embedded in N-doped porous carbon xerogel as electrode materials for sodium-ion batteries

zinc sulfide (ZnS) has attracted extensive attention as an electrode material for sodium-ion batteries (SIBs) due to its high capacity and abundant resource. In order to improve the cycling stability, ZnS nanoparticles embedded in N-doped porous carbon xerogel (ZnS/N-CX) were prepared via a facile electrostatic assembly, followed by a high-temperature sintering treatment. In contrast to the retention rate of bare ZnS electrode (6.4%), the ZnS/N-CX electrode shows better capacity retention (51.8%) at a current density of 0.5 A g−1, and delivers a reversible capacity of 312 mAh g−1 at a current density of 0.1 A g−1. This is because the porous N-CX derived from polyelectrolytes can enhance the ZnS nanoparticles' conductivity during long-term cycling. Besides, X-ray diffraction analysis is used to confirm the (de)sodiation mechanism during the 1st cycle of the ZnS/N-CX electrode. In addition, X-ray photoelectron spectroscopy analysis indicates that polymeric components in the solid electrolyte interphase (SEI) prefer to form on the surface of loaded N-CX, resulting in a massive Na+ consumption and rapid decrease of initial Coulombic efficiency (CE). The analysis of electrochemical impedance spectroscopy reveals that the increase of interface resistance is suppressed in long-term cycling, with respect to the bare ZnS electrode. Therefore, these results prove that the synergistic approach of supporting/coating N-CX can be applied in the metal sulfides to achieve improved performance in terms of Na+ storage capacity.

Room-temperature reduction at SrRuO3–metal interface in hydrogenous atmosphere detected by interface-sensitive resistance measurement

Using interface-sensitive resistance measurement techniques, we detected the reducing reaction precursor at the interface between the metallic oxide SrRuO3 and the electrodes under a hydrogenous atmosphere at room temperature. The interface resistance between this polycrystalline oxide and the electrodes (metallic pads or wires) clearly increased with the hydrogen present even at room temperature. In contrast, for bulk SrRuO3, no increase in resistance was found. The rate of increase of the interface resistance depends on the electrode material, for example, that of SrRuO3–Ag is larger than that of SrRuO3–Cu, and the rate is related to the propensity for bulk oxide to reduce; Ag2O is easier to reduce than CuO. The origin of the increase in interface resistance is posited to be the partial deficiency of oxygen in SrRuO3. Our experiments suggest that the reduction at the interface of SrRuO3 occurs at relatively low temperatures (room temperature) compared with the bulk reducing temperature of ≈200°C previously reported. In addition, electrode materials control the reducing reaction at the interface.

Application of metal-organic frameworks as cathode materials for lithium-ion batteries

<p indent=0mm>With the popularity of rechargeable devices, lithium-ion batteries are being widely used in mobile electronic devices and transportation owing to their high specific capacity and high energy density. However, phenomena of dissolution and side reactions leading to an increase in interface resistance still exist in traditional cathode materials, which drastically reduce their specific capacity and cycling performance. Due to these obvious defects, microstructure control of cathode materials has a decisive effect on their performance. Interestingly, metal-organic frameworks (MOFs), as a class of porous materials formed by self-assembly of organic ligands and metal ions or metal clusters, have been widely concerned in the field of energy storage for their advantages such as easy preparation, high porosity, large capacity and diversity. Recent research highlights that MOFs are excellent templates for building electrode materials. This paper reviews the application of MOFs and MOF-derived derivatives in lithium-ion batteries cathode materials. Herein, a summary of direct application of MOFs in cathode materials is provided. When MOFs are working as cathodes, the redox reaction of metal ions or organic active groups realizes the intercalation/deintercalation of lithium-ions. To improve the electrochemical performance of MOFs cathodes, it is important to choose organic ligands with high conductivity, high stability, porous structure and redox active sites at high density. Afterwards, the preparation methods of MOF-derived composite (MOFs as precursors or modifiers) and their application in cathodes of lithium-ion batteries are described in detail. Metal compounds or porous carbon with specific structures can be easily obtained by calcining MOFs at different temperatures under various gas atmospheres and other simple chemical reactions. Since MOF-derived derivatives retain the original morphology of MOFs, MOFs can be regarded as accurate templates for the synthesis of electrode materials. Compared with pristine MOFs, MOF-derived derivatives involve a more extensive level and have better research prospects in the storage and conversion of electrochemical energy sources due to their adjustable structure and composition, which combine the advantages of multiple materials. The following issues should be considered when developing MOF-derived materials as positive electrodes: (1) Introducing conductive materials such as porous carbon to improve the conductivity; (2) providing protective layers for the active material and reduce its dissolution to improve the cycling stability; (3) improving the specific surface area of the composite to increase the contact area between the active substance and the electrolyte for higher reactivity; (4) retaining the inherent porous structure of MOFs so as to provide channels for the transmission of lithium-ions and electrons. Finally, topic of application directions of MOFs and their derivatives in cathode materials for lithium-ion batteries is outlined, providing future prospects for the development of new electrode materials.

A Novel Ultrastable and High‐Performance Electrode Material for Asymmetric Supercapacitors Based on ZIF‐9@Polyaniline

AbstractNanoflower‐like composites have greater contact area and more redox reactive centers, which have great potential in the application of electrode materials for supercapacitors. A nonconductive polymer binder is usually used in preparation of electrodes, which causes an increase in interface resistance and a decrease in material active sites. Here, polyaniline (PANI) and ZIF‐9 are directly grown on the Ni foam (ZIF‐9@PANI/NF) by a simple solvothermal method without a nonconductive polymer binder. A nanoflower array is grown on the NF, which can be directly used as electrode material of supercapacitor. The attachment of PANI facilitates electron transfer and increases the conductivity of the material. At a current density of 1 A g−1, the specific capacitance is up to 7 times that of the ZIF‐9. The assembled asymmetric supercapacitor has a high energy density of 52 Wh kg−1 at a power density of 800 W kg−1, remaining 90.1% after 50 000 cycles. These great electrochemical properties show the material has good market development prospects for energy storage device.

Model Membrane-Free Li-S Batteries for Enhanced Performance and Cycle Life.

The success of the rechargeable Li-S cell is limited in part by the dissolution of lithium-polysulfide in the electrolyte. Remarkably, it is found that removal of the conventional membrane separator in a Li-S cell improves sulfur utilization and cycling performance, whether the sulfur is initially contained in the cathode or electrolyte. An optimized cell design yields discharge capacities as high as 980 mA h g-1 after 100 cycles.

缶用表面処理鋼板の動的接触抵抗と溶接性

Amethod of evaluating the continuity of the weld nugget in mash seam can body welding was developed. In this method, the change in electric resistance at the interface between the materials is measured with a rectangular current pulse during spot welding. Weldability is affected by the difference in the initial and final material interface resistance and by the rate of increase in interface resistance. Materials which have a wide welding current range in mash seam welding show lower initial and higher final interface resistance. Increasing the welding electrode force, which widens the welding current range in seam welding, reduces the rate of increase in interface resistance. These phenomena are attributed to the welding current path, which is affected by material interface electric resistance.