Graphene/PVDF Composites for Ni-rich Oxide Cathodes Toward High-Energy Density Li-ion Batteries

• Main Authors: Chang Won Park, Jung-Hun Lee, Jae Kwon Seo, Weerawat To A Ran, Dongmok Whang, Soo Min Hwang, Young-Jun Kim
• Format: Article
• Language: English
• Published: MDPI AG 2021-04-01
• Series: Materials
• Subjects: lithium-ion batteries; Ni-rich cathodes; graphene; PVDF; electrode density; scanning probe microscopy
• Online Access: https://www.mdpi.com/1996-1944/14/9/2271

Li-ion batteries (LIBs) employ porous, composite-type electrodes, where few weight percentages of carbonaceous conducting agents and polymeric binders are required to bestow electrodes with electrical conductivity and mechanical robustness. However, the use of such inactive materials has limited enhancements of battery performance in terms of energy density and safety. In this study, we introduced graphene/polyvinylidene fluoride (Gr/PVdF) composites in Ni-rich oxide cathodes for LIBs, replacing conventional conducting agents, carbon black (CB) nanoparticles. By using Gr/PVdF suspensions, we fabricated highly dense LiNi_0.85Co_0.15Al_0.05O₂ (NCA) cathodes having a uniform distribution of conductive Gr sheets without CB nanoparticles, which was confirmed by scanning spreading resistance microscopy mode using atomic force microscopy. At a high content of 99 wt.% NCA, good cycling stability was shown with significantly improved areal capacity (Q_areal) and volumetric capacity (Q_vol), relative to the CB/PVdF-containing NCA electrode with a commercial-level of electrode parameters. The NCA electrodes using 1 wt.% Gr/PVdF (0.9:0.1) delivered a high Q_areal of ~3.7 mAh cm⁻² (~19% increment) and a high Q_vol of ~774 mAh cm⁻³ (~18% increment) at a current rate of 0.2 C, as compared to the conventional NCA electrode. Our results suggest a viable strategy for superseding conventional conducting agents (CB) and improving the electrochemical performance of Ni-rich cathodes for advanced LIBs.