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Robustness of micro-scaled amorphous silicon during the initial lithiation/delithiation cycle

Lucas Berla (Stanford University), Seok Woo Lee (Stanford University), Ill Ryu (Stanford University), Yi Cui (Stanford University), William Nix (Stanford University)

Lithium ion batteries: When Chemistry meets Mechanics

Mon 9:00 - 10:30

Salomon 003

Recent research on the electrochemical lithiation of amorphous silicon nanoparticles supports that amorphous silicon is more fracture resistant than crystalline silicon during lithiation. To date, however, the fracture behavior of larger, microscale amorphous silicon structures has yet to be studied. Here, the morphologies of initially amorphous silicon micropillars (2.3 µm tall) are studied before and after electrochemical lithiation and delithiation. No internal or external cohesive cracking is detected in lithiated pillars for any of the pillar sizes studied. Delithiated pillars exhibit some delamination at the interface between the pillar and the underlying nickel substrate. For larger diameter pillars, the initiated interfacial crack is driven upward into the delithiated pillar but remains near the interface as the crack propagates radially inward. However, no cohesive fracture unrelated to interfacial cracking is seen in even the largest delithiated pillars. Finite element modeling supports that the observed cohesive fracture resistance of amorphous silicon micropillars should be representative of the fracture resistance of amorphous silicon microparticles of comparable dimensions.