Evaluation of core–shell poly(vinylidene fluoride)-grafted-Barium titanate (PVDF-g-BaTiO3) nanocomposites as a cathode binder in batteries

Abstract

Poly(vinylidene fluoride)-grafted-Barium titanate (PVDF-g-BaTiO3) nanocomposites were used as binders to prepare cathode material containing 70 wt% of active material (LiMn2O4), 18 wt% of conducting agent (carbon black) and 12 wt% of binder (either commercially available PVDF, modified PVDF such as PVDF-g-BaTiO3, or both). A calendering process was used in order to obtain homogenous films and a better dispersity of nanoparticles. First, the electrochemical behavior of the modified PVDF was explored in the absence of the active material and did not revealed any electrochemical activity. Then, after adding the active material into the formulation (4–12 wt%), cells made with commercially available PVDF displayed similar cycling performances as the one achieved from 4 wt% of modified PVDF. For example, at 1C, the initial discharge capacities were 146, 140 and 130 mA h g−1 for films made by 0, 4 and 8% of modified PVDF, respectively. Moreover, with the increase of charge discharge rate to 10C, the capacity can be approximately recovered when the current density returned to 1C for all the samples, revealing a good reversibility of the structure. On the other hand, calendering procedure enables to obtain a uniform structure demonstrated by reproducible tests as compared to those achieved from non-calendered films. Moreover, the calendering process showed an enhancement in cycling performances. For instance, the initial discharge capacity at 1C was 124 and 108 mA h g−1 and decreased to 82 and 2 mA h g−1 at 10C for non-calendered and calendered sample made with commercial PVDF, respectively.