A beaded-string silicon anode for lithium ion battery
Teng Li (University of Maryland), Zheng Jia (University of Maryland)
Lithium ion batteries: When Chemistry meets Mechanics
Tue 9:00 - 10:30
Salomon 003
Silicon has been long sought as a candidate anode material for lithium ion batteries due to its ultrahigh theoretical capacity, nearly 10 times in excess of conventional graphite electrodes. The primary challenge has been stress and pulverization of the material and the associated loss of electrical connectivity resulting from a ~300% volume change between lithium insertion and extraction. Significant research effort has been directed toward nanostructured forms, such as nanowires and nanotubes. Here, we address this challenge by synthesizing a new nanostructured material comprising amorphous Si beads threaded on mechanically robust and electrically conductive carbon nanotube (CNT) axial supports with rotational symmetry and controlled Si-C interfacial chemistry. In situ transmission electron microscopy combined with atomic and continuum modeling reveal that the chemically tailored Si-C interface plays important roles in constraining the threaded Si beads, such that they exhibit a symmetric “radial breathing” around the CNT string without, remaining electrically connected throughout lithiation-delithiation cycling. This novel beaded-string heterostructure also remains crack-free during cycling, in contrast to uniform Si coatings on CNTs, which suffer from transverse cracking during the very first lithiation half-cycle. This work is in collaboration with Profs. YH. Huang and J. Cumings at Univ. Maryland and Dr. Y. Qi at GM.