Carbon-based anode materials used in lithium-ion batteries have a composite structure consisting of carbon powder bonded with a binder. With the advent of aqueous electrolytes and solid electrolytes, water resistance is also required for anode materials. In this study, carbon-based anode materials made of polyvinylidene fluoride (PVDF), a solvent-based binder with higher water resistance than aqueous binder, were immersed in water and subjected to static tensile and creep tests to investigate the mechanical properties and creep characteristics of the anode and binder materials in water. Based on the test results, a simple prediction of creep deformation of the anode material in water was proposed. The test results showed that both the anode and binder materials exhibited a transition creep region, in which the creep rate, that is the increase amount of tensile strain with respect to time, gradually decreases after reaching the holding stress, and a steady state creep region, in which the creep rate remains constant after the transition creep region. Due to the PVDF softening, the creep transition region became longer, and the creep strain was larger in water than in air. Using the creep properties of the PVDF, the proposed method successfully estimated the creep properties of the anode material.
KISHIMOTO et al. (Wed,) studied this question.