(578f) Electrolessly Etched Composite Silicon Nanowire Anode for Lithium Ion Battery

Silicon nanowire as lithium ion battery anode material has attracted great attention for its superior energy storage capability (4200 mAh?g-1 for Li4.4Si phase), and capability to accommodate large volume change (400%) during lithium insertion/extraction.

Silicon nanowire arrays fabricated via Vapor Liquid Solid (VLS) grown method have been applied as anode for lithium ion battery, the anode showed large specific capacity approximately at 4200 mAh?g-1, and capacity retention of 69% after 50 charge/discharge cycles. Electrolessly fabricated silicon nanowire arrays solely have also been tested as anode in lithium cell, the anode showed charge/discharge ability, however the specific capacity is not comparable with VLS grown silicon nanowire arrays.

The new silicon nanowire composite anode shows a possibility in combining cheaply made silicon nanowire( electroless etching) and graphite composite anode. The silicon nanowire anode is prepared by the following procedures: Silicon nanowires are fabricated via electroless etching in aqueous solution, separated from the substrate, and mixed homogeneously with graphite, PVDF, NMP to make the paste. The paste was applied to nickel foil by doctor blade method, and dried at 120°C over night to evaporate the solvent. The prepared anode is assembled into half cell with metallic lithium as counter electrode for electrical measurement. All experiments are carried out in glove box system in argon atmosphere with trace amount of oxygen and moisture (under 1 ppm).

At the composition of 15% silicon nanowire, 15% PVDF and 70% graphite, the new composite anode showed initial charge capacity approximately 800 mAh?g-1 , which is comparable to the theoretical capacity of the anode at 894 mAh?g-1 . Although the capacity fade is substantial after the initial charge/discharge cycles, the specific capacity of the anode is still larger than that of graphite anode without silicon nanowires. The anode is characterized by FTIR, XPS and SEM to study the surface Solid Electrolyte Interphase (SEI) layer, which significantly affects the anode capacity, so as to further improve the capacity retention for prolonged cycles.