Effect of poly (vinylidene fluoride)/poly (vinyl acetate) blend composition as cathode binder on electrochemical performances of aqueous Li-ion battery

Abstract

In this study, the effect of poly (vinylidene fluoride)/poly (vinyl acetate) (PVDF/PVAc) ratio in the cathode binder of the LiMn2O4 (LMO) electrode on the electrochemical performance of a rechargeable hybrid aqueous battery (ReHAB) is investigated. The miscibility of two polymers is confirmed by Furrier transform infrared (FTIR) and differential scanning calorimetry (DSC) measurements. The binary blends with different PVDF/PVAc ratios (100/0, 75/25, 50/50, 25/75 and 0/100) are used as binder for the LMO cathode preparation. It is found that incorporation of PVAc in the blend decreases the crystallinity of PVDF and increases the cathode hydrophilicity, leading to better wetting by the aqueous electrolyte. The morphology and electrochemical properties of the cathode are also studied. Electrochemical cyclic voltammogram, discharge capacity, capacity retention, electrochemical impedance and rate capability are investigated. It is concluded that the blend with a PVDF/PVAc ratio of 25/75 has the best cycle performance (80% capacity retention after 100 cycles at the rate of 1 °C), with 0.2 °C discharge capacity (110 mAh gr−1) and the best rate capability.