Flow batteries with high energy density and long cycle life have been pursued to advance the progress of energy storage and grid application. Non-aqueous batteries with wide voltage windows represent a promising technology without the limitation of water electrolysis, but they suffer from low electrolyte concentration and unsatisfactory battery performance. Here, a non-aqueous lithium bromine rechargeable battery is proposed, which is based on Br2/Br− and Li+/Li as active redox pairs, with fast redox kinetics and good stability. The Li/Br battery combines the advantages of high output voltage (∼3.1V), electrolyte concentration (3.0mol/L), maximum power density (29.1mW/cm2) and practical energy density (232.6Wh/kg). Additionally, the battery displays a columbic efficiency (CE) of 90.0%, a voltage efficiency (VE) of 88.0% and an energy efficiency (EE) of 80.0% at 1.0mA/cm2 after continuously running for more than 1000 cycles, which is by far the longest cycle life reported for non-aqueous flow batteries.