Eric Mills, John Cannarella, Qi Zhang, Shoham Bhadra, Craig B. Arnold, and Stephen Y. Chou

II. EXPERIMENT

B. Assembly of anodes

The cell preparation and assembly process has four key steps: (1) transfer to an Ar-filled glovebox, (2) Li-disk preparation, (3) separator preparation, and (4) final assembly. In step (1), after etching, the anodes were moved into an Ar-filled glovebox (MBraun)—with <0.1 ppm H2O and O2—and loaded into coin cell case (Xiamen Tmaxcn Inc.). In step (2), a 7/16-in. diameter Li disk was punched from 0.5 mm-thick Li foil (Alfa Aesar) and used as a counter electrode in a two-electrode measurement configuration. The thick Li foil represented an essentially unlimited supply of lithium, so that any capacity limitations are due to degradation of the Si electrode structure. In step (3), microporous dry-stretched polypropylene separators of 1/2-in. Diameter (Celgard 2500) were soaked in a solution of 1M LiPF6 in 1:1 ethylene carbonate: dimethyl carbonate electrolyte (Novolyte Technologies). In step (4), the cells were assembled from the above components, sealed using a coin cell crimper (Xiamen Tmaxcn Inc.),and tested in ambient atmosphere at 20–23 C using a potentiostat (Arbin Instruments,BT2000).