Investigation of an eco-friendly polyacrylic acid binder system on LiFePO4 cathode electrode processing to enhance the performance of coin-cell and pouch-cell graphite||LiFePO4 batteries

Abstract

This study investigates the influence of two types of binders (aqueous and nonaqueous) on the LiFePO₄ (LFP) electrode processing and its electrochemical properties. Specifically, polyvinylidene fluoride (PVDF) and polyacrylic acid (PAA) were dissolved in NMP (N-methyl-2-pyrrolidone) or the aqueous solvent (H₂O) at varying mass ratios of 5%, 10%, and 15%. Binder durability and inertness were assessed by immersing prepared LFP electrodes in an electrolyte comprising 1.0 M LiPF₆ in EC:DEC:DMC (1:1:1 in vol%). Notably, PVDF/NMP 10% and PAA/H₂O 10%-based electrodes displayed good durability without peeling. Electrochemical characteristics were evaluated through cycling voltammetry and galvanostatic cycling with potential limitation. The PAA/H₂O 10%-based-LFP electrode exhibited a specific capacity of ~148.9 mAh g⁻¹ with a Coulombic efficiency (CE) of around 97.27%, surpassing PVDF/NMP 10%. The graphite||PAA/H₂O 10%-based-LFP electrode in a full cell demonstrated higher capacity and superior retention after 30 cycles. In a pouch cell (6 cm × 4 cm), utilizing graphite||LFP with PAA/H₂O 10%, a capacity of 25.5 mAh was achieved, maintaining 93% capacity with a CE of about 99% after 30 cycles at a rate of 0.1C.