Selecting the Degree of Partial Lithiation for Preventing Fracture in Si Micoparticles

The limiting aspect in commercializing Si-based anodes is the fractures they undergo during lithiation and de-lithiation. Experimental and theoretical studies have shown that this fracture is minimized when the particle size is reduced below 100 nm; however, this is not a commercially viable solution. Herein, we employ a multiphysics model to capture damage in 1 µm and 2 µm Si particles for different degrees of partial lithiation and corresponding de-lithiation. It is seen that partial lithiation can reduce the mechanical stresses experienced by the Si particles and fracture is fully prevented when the Li-ion penetration does not exceed 360 nm and 600 mm for 1 µm and 2 µm Si particles, respectively, when they are distributed in a binder containing smaller Si particles of 500 nm and 1 µm particles, respectively, prior to de-insertion. This indicates that limiting lithiation to 72% for 1 µm Si particles and 66% for 2 µm Si particles can prevent their pulverization. Removing the smaller Si particles and having a uniform Si size distribution results in lower lithiation states for preventing fracture. Such design information is vital for battery developers in order to fully utilize the capabilities of Si.