Analytical Investigation of Binder’s Role on the Diffusion Induced Stresses in Lithium Ion Battery through a Representative System of Spherical Isolated Electrode Particle Enclosed by Binder

Binder which serves to maintain mechanical and electrical integrity of Lithium ion batteries and occupies as much as 50% of battery weight is rather relatively less explored in terms of its effect on electrode and binder stresses during charging-discharging operation and hence motivates the present work. Closed form solution of diffusion induced stresses in an isolated spherical linear elastic, perfectly plastic electrode particle encapsulated by a linear viscoelastic binder during galvanostatic charging-discharging cycle under two sets of boundary conditions for the binder surface viz. traction free and fully constrained are developed. It is proved that the stresses in binder are unchanged even if electrode deforms elastically or plastically and whether diffusion in electrode is driven by concentration gradient or combination of concentration gradient and hydrostatic stress. The analysis identifies that current density not only directly controls the diffusion induced stress in electrode but affects it indirectly through change in stiffness of the binder depending upon the cycle time. Furthermore analysis reveals lower viscosity, lower stiffness and faster relaxation behavior as the recommended binder properties for lower diffusion induced stresses in electrode and binder.