Cracking in Si-based anodes for Li-ion batteries

In attempts to increase the anode capacity of rechargeable Li-ion batteries, composite materials with micro- and nano-scale domains of Li active material surrounded by Li inactive material are being investigated. Materials such as Si, Al and Sn that provide capacities between 900 and 4000 mAh g^-1 during the formation of Li-alloys can be used as the active sites, while inert ceramics or glasses can be as the inactive matrix. During Li insertion the volume of the active sites expands over 100% at maximum capacity. As a result large internal stresses are produced, which lead to a loss of mechanical integrity at the active site/matrix interface and eventually cracking of the electrode. Therefore, before these types of composite material systems are used commercially it is of great importance to model their mechanical response. The present study applies a previously developed formulation to predict stable crack growth in anodes which are comprised of spherical Si nanospheres embedded in a soda glass matrix.