The effects of the purification of LiAsF6-2-methyl tetrahydrofuran (2MeTHF)/ethylene carbonate (EC) mixed solvent organic electrolytes on the charge-discharge cyclability of lithium metal anodes has been investigated by using an accelerated method for evaluating lithium cycling efficiency. This method involves cycle tests on coin cells with an amorphous V2O5-P2O5 (95:5 molar ratio) cathode and an anode containing a small amount of lithium. Using this method, the cycle life of the cell was determined over a short period simply from the lithium cycling efficiency. The lithium cycling efficiency in LiAsF6-2MeTHF/EC was improved by removing both water and organic impurities such as peroxides. An electrolyte containing less than 14 ppm of water and 20 ppm of organic impurities had a high lithium cycling efficiency of 97.2%.