Effect of Molecular Weight and Degree of Substitution of a Sodium-Carboxymethyl Cellulose Binder on Li4Ti5O12 Anodic Performance

This paper presents a detailed investigation ofthe influence of molecular weight (MW) and degree ofsubstitution (DS) of sodium-carboxymethyl cellulose (CMC)used as binder of Li4Ti5O12 (LTO) anodes. CMC MW and DSwere in the range of 90 000 to 700 000 and 0.7 to 1.2,respectively. As demonstrated by coin cell tests, the LTOelectrode that contained relatively low MW and high DS CMCshowed excellent cyclic performance above 150 mAh g−1 evenafter 100 cycles. Unlike typical electrodes, the adhesionstrength of the LTO electrodes was not a critical factor for cellperformance. On the contrary, low coverage of CMC on thesurface of LTO, which leads to weak adhesion, was morefavorable to the cell performance than strong adhesion caused by high coverage. Both an increase in the DS and a decrease in theMW of CMC gave rise to low charge transfer resistance, high ion conductivity, good wettability with the electrolyte, and goodlithium ion mobility owing to a relatively large amount of LTO exposed to directly the electrolyte so long as critical adhesion isguaranteed in the LTO electrode.