Nice work, Daniel. I am thinking of plumbing solutions to the imbalance issue:
From A review of all-vanadium redox flow battery durability:
After studying the capacity fade for mixed acid electrolyte, UET [154] found that, during long‐term operation, the ratio of catholyte and anolyte concentration remained constant: 1.3:1. Based on this finding, they designed an overflow system with different volume (volume ratio: 1.3:1) anolyte and catholyte tanks, in which the volume ratio and total vanadium were kept constant. With the new design, the VRFB achieved long term capacity and efficiency stability. However, this design is only valid for the mixed acid electrolyte system. Recently, Wang et al [152] developed an electrolyte reflow method to solve the electrolyte imbalance issue for the sulfuric acidvanadium electrolyte system. Figure 10 shows the schematic of their method; without reflow, eventually all of the anolyte will move to the catholyte tank, while with reflow, the anolyte tank will always contain some electrolyte. Similar to the UET method, the volume ratio of catholyte to anolyte is a key parameter affecting the capacity stability and is highly dependent on the operating current density. Cycle life and total capacity were all improved with the reflow method.
There is also Capacity balancing for vanadium redox flow batteries through electrolyte overflow but it was retracted - they think they accidentally had a pinhole in their membrane for the test. But they did build a real overflow system:
[image: 1739741378711-aceadcdb-fb4d-4387-b6c6-9b95a79cc192-image.png]
