Binder-Free Cathode Enabling High Capacity Li-Ion Battery

Abstract

Li-ion batteries have polymeric binder in their electrodes resulting in high internal resistance and hence long charge times and compromised product lifetime. We have developed Li-ion batteries utilizing binder-free NMC cathodes containing carbon nanotube (CNT). Our proprietary processing of CNT into viscous organic or water-based slurry without surfactant or dispersant reduces or eliminates the need for organic binder and carbon black additives in these cathodes. The benefits of incorporating our processed CNT slurry into NMC cathode electrodes are realized by significant gains in specific energy and power. When the organic binder in the cathode is completely removed, our Li-ion batteries retain superior performance metrics over conventional binder-containing cells, including significantly reduced impedance (-31%) and increased capacity (5%). Li-ion pouch cells containing these binder-free NMC/CNT cathodes show 2.5% higher specific energy. Our cells with binder-free cathode complete 500 cycles with 50% less capacity fade than cells with binder, and display more than 2x improvement in capacity at 10C rate discharge. A processing advantage of eliminating the polymeric binder from the formulation mix was demonstrated by the use of IPA as dispersing solvent in place of the costlier and toxic NMP solvent. Li-ion cells containing binder-free NMC/CNT cathodes from IPA mix preserved their performance advantages over conventional NMP-based binder-containing cells. Figure 1