Reduction of Irreversible Capacity by Coating with Polymeric Amine Compound Over Artificial Graphite for Anode of Lithium Ion Secondary batteries

Coating with polyallylamine (PAA) over artificial graphite was applied to reduce its irreversible capacity. The coated graphite showed the same flat charge/discharge curves as the non-coated one. The irreversible capacity was reduced from 67 to 22 mAh/g in EC-based electrolyte by a small amount coating of PAA without change in the discharge capacity. PAA was found effective even in PC-based electrolyte. SEM observation showed the thin layer of PAA, which prevented the direct contact of electrolyte on the graphite surface. The charge characteristic, however, was deteriorated, which might be due to the increased resistance of inter-particle and/or of Li-ion diffusion through the PAA layer.