In examining the Li + charge transfer kinetics at the graphite anode and the lithium nickel cobalt aluminum oxide, LiNi 0.80 Co 0.15 Al 0.05 O 2 (NCA), cathode in a full cell, we found that the activation energy, E a , for the charge transfer at the graphite/electrolyte interface is about 68 kJ/mol, which is consistent with recently reported values. However, the E a for the charge transfer at the NCA/electrolyte interface is about 50 kJ/mol, which is lower than at the graphite anode. With desolvation as the predominate step for limiting the kinetics and both electrodes subjected to the same electrolyte, the difference in E a suggests that it is greatly influenced with respect to the nature of the electrode materials and their associated SEIs. This is further confirmed by the examination of Li + charge transfer at the LiFePO 4 (LFP)/electrolyte and the graphite/electrolyte interfaces using a LFP/graphite full cell.

Charge discharge kinetics of Li-ion batteries is dominated by the lithium ion (Li + ) charge transfer kinetics, which involves the process of transporting the solvated Li + in the electrolyte to the insertion of Li + and the accepting of an electron at the same time in the electrode active materials. The importance of electrolytes and recent studies of Li + charge transfer kinetics were briefly reviewed. Using 3-electrode cells and a DC Pulse Current Impedance method, we examined the charge discharge kinetics of the anode and the cathode in the same electrolyte at the same time. We observed a slower kinetics at the graphitic carbon anode as indicated by higher activation energy than that at the lithium nickel cobalt aluminum mixed oxide (LiNi 0.80 Co 0.15 Al 0.05 O 2 ) cathode. While desolvation is a dominating step as concluded in recent studies on the Li + charge transfer kinetics, this study suggests that the nature of SEIs and electrode materials play crucial roles on Li + charge discharge kinetics.

In examining the Li + charge transfer kinetics at the graphite anode and the lithium nickel cobalt aluminum oxide, LiNi 0.80 Co 0.15 Al 0.05 O 2 (NCA), cathode in a complete cell, we found that the activation energy, E a , for the charge transfer at the graphite/electrolyte interface is about 68 kJ/mol, which is consistent with the recently reported values. However, the E a for the charge transfer at the NCA/electrolyte interface is about 50 kJ/mol, which is lower than that at the graphite anode. With desolvation as the predominate step for limiting the kinetics and both of the electrodes were subject to the same electrolyte, the difference in E a suggests that the E a is influenced greatly with respect to the nature of electrode materials and their associated SEIs. This is further confirmed by the examination of the LiFePO 4 (LFP)/electrolyte and the graphite/electrolyte interfaces using a LFP/graphite complete cell.

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Results of laboratory experiments of arcing on graphite tiles coated by a W-layer are reported.The samples have been taken from coated tiles manufactured for ASDEX Upgrade (AUG).The motion of the arcs was observed by high-speed cameras. Additionally, sample plates have been exposed to collect macro-particles emitted by the arc. The eroded surfaces of the cathodes were investigated after experiment to characterize surface changes, tracks, and redeposited particles. On the cathode strongly radiating immobile spots are observed by the cameras acting as sources of numerous macro-particles. At the surface large holes (diameter 17µm) are found that perforate the W-layer and extend into the graphite bulk. Subsequent arcs tend to locate at the pre-existing holes. Hence, locally the W-coating is quickly and effectively broken, the W erosion is enhanced as compared to bulk W, and carbon is locally liberated despite the existence of an undamaged W-coating outside the arcing region.