Study of Water-Based Lithium Titanate Electrode Processing: The Role of pH and Binder Molecular Structure

摘要

This work elucidates the manufacturing of lithium titanate (Li4Ti5O12, LTO) electrodes via the aqueous process using sodium carboxymethylcellulose (CMC), guar gum (GG) or pectin as binders. To avoid aluminum current collector dissolution due to the rising slurries’ pH, phosphoric acid (PA) is used as a pH-modifier. The electrodes are characterized in terms of morphology, adhesion strength and electrochemical performance. In the absence of phosphoric acid, hydrogen evolution occurs upon coating the slurry onto the aluminum substrate, resulting in the formation of cavities in the coated electrode, as well as poor cohesion on the current collector itself. Consequently, the electrochemical performance of the coated electrodes is also improved by the addition of PA in the slurries. At a 5C rate, CMC/PA-based electrodes delivered 144 mAh·g⁻¹, while PA-free electrodes reached only 124 mAh·g⁻¹. When GG and pectin are used as binders, the adhesion of the coated layers to the current collector is reduced; however, the electrodes show comparable, if not slightly better, electrochemical performance than those based on CMC. Full lithium-ion cells, utilizing CMC/PA-made Li[Ni0.33Mn0.33Co0.33]O2 (NMC) cathodes and LTO anodes offer a stable discharge capacity of ~120 mAh·g⁻¹(NMC) with high coulombic efficiencies.