Novel Copolymer Dispersant with Promoted Dispersibility of the LMFP Cathode Slurry for Boosting the Li-Ion Battery Performance

Lithium manganese iron phosphate (LMFP) as the cathode of a Li-ion battery offers a higher energy density. Nanonization and carbon coating of LMFP are often required to improve its conductivity, which in turn leads to severe agglomeration and a poor slurry processing performance, ultimately resulting in a poor battery performance. This study synthesized a novel ternary copolymer dispersant by radical polymerization of vinylpyrrolidone (VP), acrylic acid (AA), and acrylamide (AM) (P(VP-AA-AM)) to enhance the dispersibility, stability, and uniformity of the LMFP cathode slurry, effectively improving the rate capability and cycling performance of the LMFP electrode. The P(VP-AA-AM) polymer with a weight-average molecular weight of 25 K exhibited promising dispersibility and stability for the LMFP slurry without gelation, attributed to the polarity of VP, the hydrogen bonding capability of AM, and the strong polarity and hydrogen bond donor ability of AA on the polymer chain. Additionally, the presence of VP, AA, and AM monomers on the polymer chain increased the flexibility and steric hindrance effect, beneficial for encapsulating and dispersing particles and preventing agglomeration. Electrochemical performance results indicate that the addition of the P(VP-AA-AM) dispersant effectively improves the conductivity and kinetic rate of the LMFP electrode with a lower charge transfer resistance and a higher ion transport rate, significantly boosting the cycling stability and rate capability of the battery.