A lithium-rich multiphase alloy foil with the nominal composition Li2.6BMg0.05 is synthesized for potential anode of rechargeable lithium batteries. Pristine Li2.6BMg0.05 is composed of rhombohedral Li5B4, cubic lithium and Li3Mg7. The overvoltage of Li2.6BMg0.05 based symmetric cells keep steady values of about 0.04V and 0.1V respectively at 0.2 and 0.5mAcm−2 within 50 cycles. By comparison, the overvoltage rises from ca. 0.04V to 0.08V at 0.2mAcm−2 and fluctuates between 0.2V and 0.4V at 0.5mAcm−2 for Li to replace Li2.6BMg0.05. The reduced voltage polarization is further confirmed by a comparison between Li2.6BMg0.05/S and Li/S full cells. Moreover, Li dendrite formation can be suppressed by use of Li2.6BMg0.05 during cycling and long-term deposition. The improvement of the Li2.6BMg0.05 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.