Interfacial reactions in lithia-based cathodes depending on the binder in the electrode and salt in the electrolyte

Lithia (Li2O)-based cathodes, utilizing oxygen redox reactions for obtaining capacity, exhibit higher capacity than commercial cathodes. However, they are highly reactive owing to superoxides formed during charging, and they enable more active parasitic (side) reactions at the cathode/electrolyte and cathode/binder interfaces than conventional cathodes. This causes deterioration of the electrochemical performance limiting commercialization. To address these issues, the binder and salt for electrolyte were replaced in this study to reduce the side reaction of the cells containing lithia-based cathodes. The commercially used polyvinylidene fluoride (PVDF) binder and LiPF6 salt in the electrolyte easily generate such reactions, and the subsequent reaction between PVDF and LiOH (from decomposition of lithia) causes slurry gelation and agglomeration of particles in the electrode. Moreover, the fluoride ions from PVDF promote side reactions, and LiPF6 salt forms POF3 and HF, which cause side reactions owing to hydrolysis in organic solvents containing water. However, the polyacrylonitrile (PAN) binder and LiTFSI salt decrease these side reactions owing to their high stability with lithia-based cathode. Further, thickness of the interfacial layer was reduced, resulting in decreased impedance value of cells containing lithia-based cathodes. Consequently, for the same lithia-based cathodes, available capacity and cyclic performance were increased owing to the effects of PAN binder and LiTFSI salt in the electrolyte.

Cyclic performance of exterior R.C beam-column strengthened with different thicknesses of CFRP sheets

The recent ground motion results indicated that the RC buildings are required to be retrofitted by different strengthening techniques. Nowadays, the external strengthening gain interest since its easy, cost effective and not required redesign of buildings. The CFRP sheets are suitable solution and utilized by a number of researchers. However, the numerical cyclic performance of connection strengthened with different thicknesses of CFRP need to be well investigated. This study assessed the performance of RC exterior beam column connection strengthened with CFRP sheets First, two grades of concrete are utilized to be control specimens, normal concrete compressive strength (C20) and high concrete compressive strength (C50) then, the specimens are retrofitted with different thicknesses (1.2, 2.4, 3.6mm) of CFRP sheets. The stresses and damage states showed the importance of connection retrofitting. The CFRP shift the plastic hinge zone away from the panel zone. Furthermore, the results demonstrated that by increase of CFRP thickness the connection resistance will be improved. The comparison between the hysteresis curves demonstrated that the yield and ultimate loading were enhanced for strengthened connection for both concrete grades and the incremental in thicknesses also increase them. The outputs also exhibited that the stiffness and ductility has increased for retrofitted specimens indicating that the CFRP comprehensively overcome the applied cyclic loading and the beam column connection is able to resist such type of loading.

DEM simulation of cyclic tests on an offshore screw pile for floating wind

Screw piles need to be upscaled for offshore use e.g. being an alternative foundation and anchor form for offshore floating wind turbines, although the high demand of vertical installation forces could prevent its application if conventional pitch-matched installation is used. Recent studies, using numerical and centrifuge physical tests, indicated that the vertical installation force can be reduced by adopting over-flighting which also improved axial uplift capacity of the screw pile. The current study extends the scope to axial cyclic performance with respect to the installation approach. Using quasi-static discrete element method (DEM) simulation it was found that the over-flighted screw pile showed a lower displacement accumulation rate, compared to a pitch-matched installed pile, in terms of load-controlled cyclic tests. Sensitivity analysis of the setup of the cyclic loading servo shows the maximum velocity during the tests should be limited to avoid significant exaggeration of the pile displacement accumulation but this may lead to very high run durations.

Theoretical and experimental evaluation of timber-framed partitions under lateral drift

This paper identifies the inherent strengths/weaknesses of rigid timber-framed partitions and quantifies the onset drifts for different damage thresholds under bi-directional seismic actions. It reports construction and quasi-static lateral cyclic testing of a multi-winged timber-framed partition wall specimen with details typical of New Zealand construction practice. Furthermore, the cyclic performance of the tested rigid timber-framed partition wall is also compared with that of similar partition walls incorporating ‘partly-sliding’ connectiondetails, and ‘seismic gaps’, previously tested under the same test setup. Based on the experimentally recorded cyclic performance measures, theoretical equations proposed/derived in the literature to predict the ultimate strength, initial stiffness, and drift capacity of different damage states are scrutinized, and some equations are updated in order to alleviate identified possible shortcomings. These theoretical estimates are then validated with the experimental results. It is found that the equations can reasonably predict the initial stiffness and ultimate shear strength of the partitions, as well as the onset-driftscorresponding to the screw damage and diagonal buckling failure mode of the plasterboard. The predicted bi-linear curve is also found to approximate the backbone curve of the tested partition wall sensibly.

Interfacial reactions in lithia-based cathodes depending on the binder in the electrode and salt in the electrolyte

Lithia (Li2O)-based cathodes, utilizing oxygen redox reactions for obtaining capacity, exhibit higher capacity than commercial cathodes. However, they are highly reactive owing to superoxides formed during charging, and they enable more active parasitic (side) reactions at the cathode/electrolyte and cathode/binder interfaces than conventional cathodes. This causes deterioration of the electrochemical performance limiting commercialization. To address these issues, the binder and salt for electrolyte were replaced in this study to reduce the side reaction of the cells containing lithia-based cathodes. The commercially used polyvinylidene fluoride (PVDF) binder and LiPF6 salt in the electrolyte easily generate such reactions, and the subsequent reaction between PVDF and LiOH (from decomposition of lithia) causes slurry gelation and agglomeration of particles in the electrode. Moreover, the fluoride ions from PVDF promote side reactions, and LiPF6 salt forms POF3 and HF, which cause side reactions owing to hydrolysis in organic solvents containing water. However, the polyacrylonitrile (PAN) binder and LiTFSI salt decrease these side reactions owing to their high stability with lithia-based cathode. Further, thickness of the interfacial layer was reduced, resulting in decreased impedance value of cells containing lithia-based cathodes. Consequently, for the same lithia-based cathodes, available capacity and cyclic performance were increased owing to the effects of PAN binder and LiTFSI salt in the electrolyte.