Greenhouse gas emissions produced during electricity generation can be reduced by increasing the energy efficiency of power generation systems. One approach to increase generation efficiency is by extracting additional electrical energy from low-grade waste heat (< 100 °C) using thermally regenerative redox flow batteries (TRABs). TRAB chemistries with the largest equilibrium potentials use two different active metals and are referred to as bimetallic TRABs (B-TRAB). In most designs, copper is the positive electrode and zinc is the negative electrode. Using thermal energy, ammonia is moved between battery electrolytes to favorably modify the cell potential of the two electrochemical steps within the cycle. A typical B-TRAB system has four steps to complete a full cycle: 1) high-voltage electrochemical discharge, 2) thermal ammonia separation, 3) low-voltage electrochemical charge, and 4) thermal ammonia separation. During step 1, copper is reduced at the positive electrode and zinc is oxidized at the negative electrode creating aqueous zinc-ammonia complexes. Next, ammonia is separated from the zinc complexes and introduced to the copper electrode electrolyte, thereby increasing the equilibrium potential of the negative electrode, and decreasing the potential of the positive electrode. This creates a smaller cell potential required for electrochemical charging during step 3. After charging, ammonia is thermally separated from the electrolyte and re-introduced to the zinc-containing electrolyte returning the system to step 1. Currently, B-TRAB designs use solid zinc and copper electrodes which lead to low coulombic efficiencies at the copper electrode. Here, we demonstrate how the B-TRAB system can be improved by the addition of ammonium bromide to the positive electrolyte stabilizing Cu(I) species and replacing copper deposition/dissolution reaction with the Cu(I, II) reaction on a carbon felt. As a result, the open circuit potential during charging can be as small as 0.8 V, and as large as 2 V for the discharge step. Polarization curves showed that peak power for the discharge cycle was 98 mW cm^-2, a significant improvement over previous B-TRABs.