Stress-electrochemistry interactions in a composite electrode for Li-ion batteries

A cylindrical composite anode with a graphite shell (radius Rs) and a silicon core (radius Rc) is used to explain the physics involved in the interactions between mechanics, electrochemistry and particle geometry. Potentiostatic and potentiodynamic simulations are used to illustrate the role of elastic driving forces on the concentration, stress distributions and the current-voltage relations. Potentiostatic simulations show that, concentration and stress distributions are altered by the intercalation stresses. Potentiodynamic simulations are conducted by either charging and then discharging or, discharge followed by charging the particle. Voltammograms show that the presence of intercalation stresses alters the electrochemical response significantly. The magnitude of this alteration depends on particle size, sweep rate and on whether the particle is charged or discharged first. The difference between peak anodic current density (Δimax) in the voltammograms obtained from including stresses in the formulation and that from excluding it, is used to quantify stress-electrochemistry interactions. The parameter Δimax is mapped for various values of Rc and [Formula presented], for a given sweep rate, suggesting a design space from which the core and the shell geometries with an acceptable level of stress-electrochemistry interactions can be chosen. Higher sweep rates may enhance Δimax depending on whether the particle is charged or discharged first.