Optimized NMC622 electrodes with a high content of the active material: A comprehensive study

Abstract

The composition of lithium-ion battery positive electrodes, incorporating an active material, conductive carbon additives, and a binder, fundamentally influences the electrode physical and electrochemical characteristics. In this study, the properties of positive electrodes with a high amount of an active material (LiNi0.6Mn0.2Co0.2O2 98 wt-%), were tested with different ratios of carbon nanotubes (CNTs) and carbon black (CB) additives, along with varying amounts of a PVDF binder. Consequently, the electrode rate capability improves with the increase of CNTs up to 30 wt-% in the total conductive carbon share and increasing the binder amount to 1 wt-%, attributed to the optimal balance of inactive material amount. The optimal composition is determined to be 98 wt-% NMC622, 1 wt-% PVDF, and 1 wt-% total conductive carbons, out of which CNT shares accounting for 30 wt-%. Furthermore, this study continues by comparing the optimal composition with the reference electrode (CNT-free) to assess the impact of CNTs on electrochemical performance. With CNTs present, the electrode attains higher energy density and specific capacity owing to uniform conductive network. Operando XRD and dilatometry experiments also reveal that CNTs reduce irreversible height change during cycling and minimize anisotropic lattice changes, thus enhancing capacity retention.