Role of in situ electrode environments in mitigating instability-induced battery degradation

Silicon nanowires and nanotube electrode particles are known for their high charge capacity and good cyclability. However, since Si undergoes volumetric expansion of more than 300% upon lithiation, the electrode particles suffer from buckling instability when axially constrained. The framework presented here enables us to investigate this failure using a buckling criterion in a coupled chemo-mechanical environment. The consideration of more realistic electrode environments helps us go beyond the predictive capabilities of current instability models. The surrounding material sensitively determines the coupling effects of mechanical stresses and electrochemical performance. The study prescribes the safe lengths of the electrode particles to prevent buckling at various states of charging and establishes the reinforcing role of surrounding binder material in facilitating the use of greater particle-lengths. Interestingly, the model predicts a minimum state of charge corresponding to a given binder elastic modulus prior to which the particle will never buckle irrespective of its length. The results show how the electrode surroundings could be manipulated to usefully exploit the impending particle instabilities into modeling sophisticated electrode structures consisting of architected materials.