On the performance of a hierarchically porous Ag 2 S-Cu x S electrode in Li-ion batteries.

A new binder- and carbon-free electrode for lithium-ion batteries was prepared using a hierarchically porous Ag-based current collector. The latter was produced by applying the method of selective dissolution of the less noble metals from the Cu 60 Ag 30 Al 10 master alloy tape. The current collector was reaction-coated with an electrochemically active Ag 2 S-Cu x S coating. The metallic structure provided a mechanically stable conductive scaffold on the walls of which the Ag 2 S-Cu x S skin material was directly deposited. The ordered porosity - hierarchical and directional - provided easy penetration of the liquid electrolyte as well as short Li + ion diffusion paths. The as-prepared electrodes were tested in a half-cell configuration vs. Li/Li + at various current rates to study the cycling and rate performances of the electrode. The first cycling capacity of ∼1250 mA h g -1 was measured at 0.4 A g -1 current rate. After a rapid decrease, a stable reversible capacity of ∼230 mA h g -1 was established at a current rate of 0.4 A g -1 (calculated vs. the weight of the incorporated sulphur). Excellent charge/discharge cycling and rate properties were observed for over 1000 cycles at higher rates of 1.0 and 2.0 A g -1 , in the potential window of 0.15-2.8 V vs. Li/Li + . The observed cycling stability was ascribed to the mechanism of a "displacement" reaction with Li ions. Additional capacity is also available from alloying-dealloying with Ag (and Cu to some extent) and S redox reactions. These results open up a new opportunity for using a Cu-Ag alloy as the precursor for making electrodes for thin Li-ion and Li-S batteries with high cycling stability at relatively high current rates.