Lithium-rich Li_(2.6)BMg_(0.05) alloy as an alternative anode to metallic lithium for rechargeable lithium batteries

摘要

A lithium-rich multiphase alloy foil with the nominal composition Li_(2.6)BMg_(0.05) is synthesized for potential anode of rechargeable lithium batteries. Pristine Li_(2.6)BMg_(0.05) is composed of rhombohedral Li_5B_4, cubic lithium and Li_3Mg_7. The overvoltage of Li_(2.6)BMg_(0.05) based symmetric cells keep steady values of about 0.04 V and 0.1 V respectively at 0.2 and 0.5 mA cm~(-2) within 50 cycles. By comparison, the overvoltage rises from ca. 0.04V to 0.08 V at 0.2 mA cm~(-2) and fluctuates between 0.2 V and 0.4V at 0.5 mA cm~(-2) for Li to replace Li_(2.6)BMg_(0.05). The reduced voltage polarization is further confirmed by a comparison between Li_(2.6)BMg_(0.05)/S and Li/S full cells. Moreover, Li dendrite formation can be suppressed by use of Li_(2.6)BMg_(0.05) during cycling and long-term deposition. The improvement of the Li_(2.6)BMg_(0.05) anode may be due to its porous framework structure and slightly decreased reactivity, which reduce the effective current density and benefit the interfacial stability. The test results indicate that lithium-rich multiphase alloys could be promising for anode material of rechargeable lithium batteries.