Improved electrochemical performance using well-dispersed carbon nanotubes as conductive additive in the Ni-rich positive electrode of lithium-ion batteries
Jae Hong Choi, Chaewon Lee, Sung-Woo Park, Mingi Hwang, Tom James Embleton, Kyungmok Ko, Mina Jo, Kashif Saleem Saqib, Jeongsik Yun, Minki Jo, Yoonkook Son, Pilgun Oh
Abstract
Carbon nanotubes (CNTs) are being used as a conductive material to achieve fast charging/discharging properties in high current density LIB systems. However, it is difficult to form a well-distributed electron transfer network within the electrode using CNTs due to their high aggregational properties. In this paper, we propose a strategy to fabricate the positive electrode with well-dispersed CNTs, controlling the solid content and sonication process of the slurry using LiNi0.8Co0.1Mn0.1O2 as the cathode materials. The CNTs are typically not well-mixed within the active material composite and aggregation occurs on the electrode surface in low solid content of under 50 wt%. When the solids content is as high as 70 %, CNTs are more evenly distributed in the electrode as bundled particles, however, there was no performance improvement using the ultra-sonication process. The CNTs at a mass ratio of CNTs at 4 wt% are well distributed in the electrode in 60 wt% of solid content, resulting in improved capacity retentions of 99.1 % after 100 cycles at a current density of 1C. When the electrochemical performance with CNTs was compared with Super P according to 1,2,3 and 4 wt% at a solid content of 60 %, the electrode using CNTs has a generally improved electrochemical performance due to the stable H1-M phase transition and stable average voltage during charging/discharging. Additionally, the excellent cycle ability at 5C with CNTs (92.8 % of capacity retention after 100 cycles) is helped by the fact that little polarization was observed compared with the Super P cells.