Influence of the Degree of Substitution of Carboxymethyl Cellulose Binders on the Properties and Performance of Aqueously Processed LiNi _0.6 Mn _0.2 Co _0.2 O ₂ ‐Based Positive Electrodes—A Comparative Study

The production of positive electrodes for lithium ion batteries typically involves the use of the environmentally harmful solvent N ‐methyl‐2‐pyrrolidone to process the binder polyvinylidene difluoride. An alternative approach is aqueous processing with more environmentally friendly binding agents (BAs) like sodium carboxymethyl cellulose (CMC). This article investigates the influence of the degree of substitution (DS) of CMC, indicating the average number of hydroxy groups substituted with carboxymethyl groups, on the microstructure, as well as on the physical properties of LiNi 0.6 Mn 0.2 Co 0.2 O 2 ‐based positive electrodes. The results indicate a higher DS to be associated with enhanced electronic conductivity and improved adhesion of/within the composite electrode. Battery cells containing aqueously processed electrodes with CMC, with a DS of 1.2, displayed enhanced cycling stability and rate capability in comparison to cells based on CMCs with a lower DS of 0.9 and 0.7. This is attributed to stabilizing effects that occurred during the process of electrode drying. These became more prominent with increasing DS and resulted in the formation of electrodes with higher initial porosity and a favorable distribution of the carbon binder domain comprised of BA and conductive additive.