Effects of Surface Modification and Organic Binder Type on Cell Performance of Water-Processed Ni-rich Li(Ni0.8Co0.1Mn0.1)O2 Cathodes

The Ni-rich Li(Ni0.8Co0.1Mn0.1)O2 (NCM811) is surface-modified using phosphoric acid (HPO) and silane reagents, and water-based cathode slurries of unmodified and modified NCM811 are prepared with poly(acrylonitrile) (PAN) or poly(acrylic acid) (PAA) added as the binder to compare the electrochemical performances of the constructed cells. Surface modification using HPO or the addition of PAA as the binder can substantially reduce the alkalinity of the prepared aqueous slurry of NCM811, thereby preventing the slurry from corroding the aluminum current collector, as well as retaining the good structural integrity of the dried electrode. The aforementioned advantage about the reduction in the alkalinity is not achieved when the hydrophobic silane-modified NCM811 or the neutral binder PAN is used. The best cell performance in terms of electrochemical reversibility, ionic and electronic impedance, and cycle stability is obtained when the water-based cathode slurry is prepared using HPO-modified NCM811 as the cathode active and PAA as the binder simultaneously. Moreover, the addition of PAA rather than the adoption of HPO-modified NCM811 contributes more to the improvement of cell performance.