Effect of insertion of an elastic buffer layer on stability of patterned amorphous silicon thin film Li-ion anode

Amorphous silicon (a-Si) in the form of various nanoscale architectures (nanoparticles, nanoflakes, nanorods, nanowires, hollow nanotubes, and thin films) is a promising alternative anode to traditional carbon with considerable potential for high capacity lithium-ion batteries. However, silicon-based systems suffer from colossal volume expansion-related stresses leading to electrode decrepitation causing rapid capacity fade, and consequently, poor cycling performance. Loss of mechanical integrity of the anode due to lithium alloying-induced stresses is the primary reason for this capacity fade. We hypothesized that disintegration of the a-Si thin film occurs due to the mechanical constraints against lithium intercalation/alloying-induced volume expansion imposed by the current collector, and alteration of this mechanical constraint using an intervening soft layer will considerably improve the stability of the anode system. To test this hypothesis, we utilized an innovative custom-developed multiphysics finite element framework to model the anode system. Our simulations revealed that modulus mismatch between the silicon thin film and the elastic layer sandwich between this layer and the current collector is a key design parameter critical for improving the mechanical integrity of the silicon thin film. We also determined that the adhesion between the different anode components is important in prolonging the anode life.