Aqueous based cathodes with LiPAA-Alginate blended binder

Li-ion batteries are one of the most advanced energy storage systems and provide one of the highest energy densities for secondary batteries, long cycle life, and good power capacity. The main solvent for PVdF binders used today for cathode production is NMP, an organic solvent which is expensive, volatile, toxic, and the recovery is energy intensive. Even though PVdF has some good properties, it also has its disadvantages, such as poor binding affinity to the current collector, and it is expensive.^1-2 Using water as a dispersant, water-based binders show advantages in terms of their eco-friendliness, cost, and safety.^3-4 Although numerous aqueous binders have been described, there is little work on binder blends with the goal of improving the overall properties (flexibility, adhesion) of the electrodes. In this work binder blends electrodes of PAA and alginate with NCM622 as active materials is addressed.

In this study we report on developing a feasible process for slurry preparation using blended binder of polyacrylic acid (PAA) and sodium alginate. The slurry is dissolved using a high shear mixer, where different mixing routes are examined to investigate the material process interactions. Properties of the slurries such pH and agglomerate size are monitored during the mixing process. The slurry is casted onto a current collector using the slot die technique. Blended binders of alginate with PAA enabled stable electrochemical performance of the electrodes, very good adhesion, and mechanical properties e.g., flexibility. Rate capability and cycle life measured in coin cells was compared between NMP/PVDF reference cells and cells with the water-processed electrodes. The properties of the electrodes and cells were systematically compared in terms of processing and electrode composition. The water-based processed electrodes showed comparable performance. This work reports that aqueous blended binders consisting of PAA and alginate enables the preparation of homogeneous suspensions with superior mechanical properties and a very promising water-based cathodes.

References:

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