Inseong Cho

A comparative investigation of carbon black (Super-P) and vapor-grown carbon fibers (VGCFs) as conductive additives for lithium-ion battery cathodes

To investigate the synergistic effect of different types of conductive additives on the cathode performance of lithium-ion batteries, various types of cathode materials containing different ratios of vapor-grown carbon fibers (VGCFs) and carbon black (Super-P) are investigated. The pillar-like morphology of the VGCFs enabled them to efficiently connect to the active materials and hence, the highest electrical conductivity of LiCoO2 and LiFePO4 (both of which are composed of primary particles) was achieved with the VGCFs. On the other hand, for LiNi0.6Co0.2Mn0.2O2, composed of micro-sized secondary particles embedded with nano-sized primary particles, improved electrical conductivity was achieved with a mixture of VGCF and Super-P via synergistic action.

Three-Dimensional Adhesion Map Based on Surface and Interfacial Cutting Analysis System for Predicting Adhesion Properties of Composite Electrodes

Using a surface and interfacial cutting analysis system (SAICAS) that can measure the adhesion strength of a composite electrode at a specific depth from the surface, we can subdivide the adhesion strength of a composite electrode into two classes: (1) the adhesion strength between the Al current collector and the cathode composite electrode (FAl-Ca) and (2) the adhesion strength measured at the mid-depth of the cathode composite electrode (Fmid). Both adhesion strengths, FAl-Ca and Fmid, increase with increasing electrode density and loading level. From the SAICAS measurement, we obtain a mathematical equation that governs the adhesion strength of the composite electrodes. This equation revealed a maximum accuracy of 97.2% and 96.1% for FAl-Ca and Fmid, respectively, for four randomly chosen composite electrodes varying in electrode density and loading level.

Mussel-inspired Polydopamine-treated Copper Foil as a Current Collector for High-performance Silicon Anodes

A new Cu current collector was prepared by introducing a mussel-inspired polydopamine coating onto a Cu foil surface to improve the electrochemical performance of a Si electrode. The polydopamine coating covalently bonded the polymeric binder (with hydroxyl functional groups) via a condensation reaction. The coating improved the adhesion strength between the Si composite electrode and the Cu current collector (245.5 N m−1, 297.5 N m−1, and 353.2 N m−1 for the Si electrodes based on bare Cu, polydopamine-treated Cu without thermal treatment, and polydopamine-treated Cu with thermal treatment, respectively). We demonstrate that the detachment between the Si composite electrode and the current collector plays an important role in determining the electrochemical performance of the Si electrode. The cycle life and rate capability of the Si electrode improved when the polydopamine surface-treated Cu current collector was used (963.9 mAh g−1, 1361.1 mAh g−1, and 1590.0 mAh g−1 for the Si electrodes based on bare Cu, polydopamine-treated Cu without thermal treatment, and polydopamine-treated Cu with thermal treatment, respectively, at C/2 after 500 cycles).

Highly rough copper current collector: improving adhesion property between a silicon electrode and current collector for flexible lithium-ion batteries

Two types of Cu foil, conventional flat Cu foil and rough Cu foil, are used to fabricate silicon (Si) electrodes for flexible and high-energy-density lithium-ion batteries (LIBs). Confocal microscopy and cross-sectional SEM images reveal the roughness of the very rough Cu foil to be approximately 3 μm, whereas the conventional flat Cu foil has a smooth surface and a roughness of less than 1 μm. This difference leads to the improvement of the interfacial adhesion strength between the Si electrode and the Cu foil from 89.7 (flat Cu foil) to 135.7 N m−1 (rough Cu foil), which is measured by a versatile peel tester. As a result, the Si electrode with high Si content (80 wt%) can deliver a significantly higher discharge capacity of 1500 mA h g−1 after 200 cycles, even at a current rate of 1200 mA g−1. Furthermore, when the corresponding Si electrode is assembled into a pouch-type cell and cycled in the rolled conformation with a radius of 6.5 mm, the Si electrode with rough Cu foil shows a stable cycle performance due to better interfacial adhesion.