Stress-diffusion coupled multiscale analysis of Si anode for Li-ion battery†

Silicon (Si) is one of the most promising anodes for next-generation lithium (Li)-ion batteries because of its high capacity. However, the commercial uses of Si anodes are hindered by extremely poor cycling stability caused by huge volume expansion during charging and discharging processes as well as by a change in material properties according to Li concentration. Given these reasons, we propose the multiscale analysis of Si nanowire anode using a diffusion-induced stress model with Li concentration effects, such as softening of mechanical modulus and enhancement of Li diffusion. From the geometry context, the diffusion-induced stress model exhibits stress relaxation during the lithiation and optimal condition of the Si nanowire. We then construct an approximated stress criteria equation for the safe operation of Si nanowire of various sizes and shapes. Our multiscale analysis predicts the various types of Si nanowire, including holecaped Si nanowires, which are beneficial to mechanical stability. This study provides insights into the physics of Li-Si compound behaviors and introduces the possibility of developing Si-based anodes with mechanical stability.