Interfacial materials cathode contact

It is preferable for the cathode interface to have a low WE contact for efficient electron extraction. Low WF metals, such as calcium (Ca), barium (Ba) or magnesium (Mg), are usually inserted into the interfaee between Al and organic active layer to improve the device performance. " However, the low WF metal is vulnerable to oxidation under ambient eonditions, and electrode degradation is a major concern for this type of deviee. Therefore, the development of new interfacial materials to use as a eathode interlayer is still required. 

Besides the glass seal interfaces, interactions have also been reported at the interfaces of the metallic interconnect with electrical contact layers, which are inserted between the cathode and the interconnect to minimize interfacial electrical resistance and facilitate stack assembly. For example, perovskites that are typically used for cathodes and considered as potential contact materials have been reported to react with interconnect alloys. Reaction between manganites- and chromia-forming alloys lead to formation of a manganese-containing spinel interlayer that appears to help minimize the contact ASR [219,220], Sr in the perovskite conductive oxides can react with the chromia scale on alloys to form SrCr04 [219,221],... 

In addition to the criticisms from Anderman, a further challenge to the application of SPEs comes from their interfacial contact with the electrode materials, which presents a far more severe problem to the ion transport than the bulk ion conduction does. In liquid electrolytes, the electrodes are well wetted and soaked, so that the electrode/electrolyte interface is well extended into the porosity structure of the electrode hence, the ion path is little affected by the tortuosity of the electrode materials. However, the solid nature of the polymer would make it impossible to fill these voids with SPEs that would have been accessible to the liquid electrolytes, even if the polymer film is cast on the electrode surface from a solution. Hence, the actual area of the interface could be close to the geometric area of the electrode, that is, only a fraction of the actual surface area. The high interfacial impedance frequently encountered in the electrochemical characterization of SPEs should originate at least partially from this reduced surface contact between electrode and electrolyte. Since the porous structure is present in both electrodes in a lithium ion cell, the effect of interfacial impedances associated with SPEs would become more pronounced as compared with the case of lithium cells in which only the cathode material is porous. 

Perhaps more important than cost is the solution to the crucial problem of interfacial contacts that always plagues homogeneous GPE films prepared from traditional approaches. Since both cathode and anode composite materials are coated on their substrates with the same PVdF—HEP copolymer as the binder, the in situ gellification following the electrolyte activation effectively fuses the three cell components into an integrated multilayer wafer without physical boundaries, so that the interfaces between anode and electrolyte or cathode and electrolyte are well extended into the porous structures of these electrodes, with close similarity to the interfaces that a liquid electrolyte would access. 

Nikam et al. (2008) proposed a low-temperature carburization (Cao, 2003) for the improvement of corrosion resistance and electric properties of 316L specimens. In potentiostatic tests, corrosion current densities were obtained to be 4 pA cm in anodic and 1.5 pA cm" in cathodic PEM fuel cell environment. Interfacial contact resistance of LTC 316L was lowered by approximately 24% compared to untreated material. 

For secondary batteries, highlights for some additional difficulties arising from the need to recycle the systems have been reviewed. These include low diffusion coefficients for ionic transport within intercalation cathode materials, failure modes associated with high current densities, and exacerbations of interfacial contact problems on recycling. 

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