Optimization of the Electrode Properties for High-Performance Ni-Rich Li-Ion Batteries.

The microstructure of the electrodes in lithium-ion batteries (LIBs) strongly affects their gravimetric and volumetric energy and power as well as their cycle life. Especially, the effect of the microstructure in the case of next-generation Ni-rich cathode materials has not yet been investigated. A comprehensive understanding of the calendering process is therefore necessary to find an optimal level of the electrode microstructure that can enhance lithium-ion transportation, minimize plastic deformation, and improve conductivity. This work therefore aims to investigate the effect of microstructure and wettability on the electrode kinetics of next-generation Ni-rich LiNi0.88Co0.09Al0.03O2-based 18650 cylindrical cells, which were produced at the semiautomation scale of the pilot plant. Thus, all materials, electrodes, and the battery production are in quality control as the same level of commercial LIBs. With the optimized microstructure and other properties including a finely tuned compaction degree of 17.54%, a thickness of 188 µm, a sheet resistivity of 36.47 mΩ cm-2, a crystallite size of 88.85 nm, a porosity of 26.03%, an electrode Brunauer-Emmett-Teller (BET) surface area of 1.090 m2 g-1, an electrode density of 2.529 g cm-3, and an electrolyte uptake capability of 47.8%, the optimized LiNi0.88Co0.09Al0.03O2 18650 cylindrical cells exhibit excellent high-rate capacity retention, fast Li-ion diffusion, and low internal resistance. The optimized electrode microstructure of next-generation Ni-rich cathode materials could be an effective strategy toward the real application of next-generation Ni-rich LIBs.

A new approach to surface activation of porous nanomaterials using non-thermal helium atmospheric pressure plasma jet treatment.

Non-thermal helium atmospheric pressure plasma jet treatment is applied to the surface activation of porous TiO2 nanoparticle assemblies. Treatment conditions such as the working distance of the plasma discharge, helium gas flow rate, and treatment time are optimized for effective removal of contaminants from the assembly surface. Laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF MS) is applied to detect trace amounts of contaminants on assembly surfaces. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations confirm that the nanoparticle assemblies retain their original perfect spherical structures as well as their ultra-fine convex-concave nano-surfaces even after the plasma jet treatment. N2 adsorption/desorption and X-ray diffraction (XRD) measurements show no significant changes in their BET specific surface areas and crystal structures, respectively. The plasma jet-treated TiO2 nanoparticle assemblies show a 3.8 fold improvement in their reaction rate constants for methylene blue degradation and a 2 fold enhancement of their photocurrents under UV irradiation when compared with untreated TiO2.