No abstract

In recent years, many novel sensing nanomaterials were explored experimentally and theoretically as chemical gas sensors to detect sulphur hexafluoride (SF 6) decomposed species with rapid response, high sensitivity and selectivity, as well as low cost, in order to estimate and guarantee the operation status of SF 6 insulation devices. However, there has been no systemic review yet to comprehensively understand their sensing mechanism and conclude their sensing application. Such kinds of nanomaterials include traditional carbon-based materials such as carbon nanotube and graphene, metal oxides such as SnO 2 , ZnO and TiO 2 , transition metal dichalcogenides such as MoS 2 monolayer and MoTe 2 monolayer as well as graphene-like InN monolayer. A systemic review would be significant to give a profound insight into the exploration of nanomaterial-based chemical gas sensors in the field of electrical engineering and to help youth scholars first stepping in this field rapidly master the progress inside. Thus, the authors attempt to complete this review here. They are hopeful that this review could provide some guidance to fulfil such purpose in the near future, and it would be full of perspective to explore more novel nanomaterials as defect indicators in SF 6 insulated devices. Furthermore, it is their hope that this review could broaden the sensing application of admirable nanomaterials in many fields such as environmental monitoring and pollutant scavenging.

components of high-performance SSBs is the solid-state electrolyte (SSE). Oxidebased SSEs, [2] sulfide-based SSEs, [3] halidebased SSEs, [4] polymer-based SSEs, [5] and hybrid electrolytes [6] are regarded as the most encouraging candidates for applications in SSBs. [7] Among them, polyethylene oxide (PEO) based solid polymer electrolytes (SPEs) show great promising due to its high ionic conductivity at elevated temperature, low interfacial resistance toward electrodes, and simple fabrication process. [8] More importantly, all-solid-state polymer batteries (ASSPBs) with lithium metal anode, SPE and LiFePO 4 cathode have been commercialized and used in the Bolloré Bluecar, [5] which clearly demonstrates the great capability of SPE for SSBs for EV application.However, it has been found that the state-of-the-art PEO-based SPEs developed so far delivered poor electrochemical performance when coupling with high energy density cathodes, such as lithium cobalt oxide (LiCoO 2 ), layer structure lithium nickel manganese cobalt oxide (NMC), and lithium nickel cobalt aluminum oxide (NCA). [9] This is because PEO-based SPEs have a relatively low electrochemical oxidation potential-less than 3.8 V versus Li/Li + . [10] However, these high energy density cathodes typically require charging voltages up to 4.2 V or higher to achieve a high specific capacity. At these voltages range, PEO-based SPEs will undergo electrochemical oxidation decomposition. [10,11] In order to address this serious limitation, significant research efforts Polyethylene oxide (PEO) based solid polymer electrolytes (SPEs) are incompatible with the 4 V class cathodes such as LiCoO 2 due to the limited electrochemical oxidation window of PEO. Herein, a number of binders including commonly used binders PEO, polyvinylidene fluoride (PVDF), and carboxylrich polymer (CRP) binders such as sodium alginate (Na-alginate) and sodium carboxymethyl cellulose, are studied for application in the 4 V class all-solid-state polymer batteries (ASSPBs). The results show ASSPBs with CRP binders exhibit superior cycling performance up to 1000 cycles (60% capacity retention, almost 10 times higher than those with PEO and PVDF binders). Synchrotron-based X-ray absorption spectroscopy (XAS), morphology studies and density functional theory studies indicate that, with their carboxyl groups, CRPs can strongly bind the electrode materials together, and work as coating materials to protect the cathode/SPE interface. Cyclic voltammetry studies indicate that CRP binders are more stable at high voltage compared to PEO and PVDF. The stability under high voltage and the coating property of CRP binders contribute to stable cathode/SPE interfaces as disclosed by the X-ray photoelectron spectroscopy and Co L-edge XAS results, enabling long cycling life, high performance 4 V class ASSPBs.