We presented a mild pH-decoupling ARFB, operating with a negolyte pH of ~13 and a posolyte pH of ~3, suppressing acid-base crossover rates to less than 0.3 nmol s -1 cm -2 . This strategy permits an open-circuit voltage exceeding 1.7 V with unprecedentedly long lifetime and only minor energy cost and Coulombic efficiency penalty. Additionally, we developed a sub-cell using a bipolar membrane that can recover leaked protons and hydroxides without requiring exogenous addition of acid and base, thereby preventing the long-term salt accumulation problem. This work resolves the long-standing tradeoff between high voltage output and the energy cost penalty associated with acid-base crossover. The ARFB cell and acid-base recovery cell design can be utilized in other multi-chamber batteries or pH-sensitive electrochemical applications. Future work on pHdecoupling batteries should not only pursue astonishingly high voltage output, but also pay more attention to the long-term practicability of the setup and the cost associated with maintaining the pH difference. Regarding the capital cost of energy storage, higher voltage output of the pHdecoupling setup can increase the acid-base crossover tolerance, which informs the development of next-generation, long-lifetime pH-decoupling ARFBs and aqueous redox-active molecules.