Effect of poly(acrylic acid) on adhesion strength and electrochemical performance of natural graphite negative electrode for lithium-ion batteries

High-capacity natural graphite negative electrodes for use in prismatic lithium-ion batteries are fabricated from an aqueous suspension precursor. The effects of poly(acrylic acid) (PAA) on suspension stability and the resulting mechanical properties of the electrodes are investigated. Precursor suspensions consisting of graphite particles, sodium carboxymethyl cellulose (CMC), emulsified styrene-butadiene (SB) copolymer latex and PAA are prepared in an aqueous medium and tape-cast on to a copper foil. The addition of PAA enhances the stability of the suspension at low shear rates without compromising the solvent-thickening effect of CMC. Peel test results showed that the adhesion strength of the graphite electrode on the copper substrate is significantly improved by PAA. Graphite negative electrodes fabricated using PAA are characterized by gravimetric and volumetric energy densities of more than 340 mAh g−1 and 560 mAh cm−3, respectively. The PAA formulation also leads to improved cycle life, with a discharge capacity exceeding 90% of initial capacity after 500 cycles.