Investigating the Effect of Electrode Compositions on Dry-made NMC811 Positive Electrodes

Abstract

Dry electrode manufacturing processes are appealing as they can potentially mitigate the economic and environmental consequences of traditional slurry techniques. Understanding the interactions among active material (AM), conductive agent, and binder in dry-made electrodes is crucial for achieving the desired electrode performance and durability. In this study, we conducted a comprehensive investigation of the effects of the different electrode formulations by altering the ratio of polyvinylidene fluoride (PVDF) binder and carbon black (CB) for LiNi0.8Mn0.1Co0.1O2 (NMC811) electrodes made using a dry coating process. Specifically, we examined four distinct electrode formulations: 96:3:1, 96:2:2, 90:7.5:2.5, and 90:5:5 (AM: PVDF: CB), equivalent to PVDF/CB mass ratios of 1:1 and 3:1. We found that a high PVDF content at PVDF/CB ratio of 3:1 provides high mechanical strength. However, the electrode ionic conductivity decreases due to the insulating aggregates of PVDF. The PVDF/CB ratio of 1:1 approaches the optimum ratio for balanced electronic and ionic conductivities and electrode mechanical strength, hence leading to enhanced electrochemical performance. For electrodes with the PVDF/CB ratio of 1:1, we observed surprisingly that electrode with higher AM content (e.g., 96%) showed a comparable C-rate and full-cell cycling performance to that with lower AM content (90%).