The huge problem with Ni-Zn batteries is the active material actually flows downward with gravity, until the anode and cathode eventually short out. I believe t

The huge problem with Ni-Zn batteries is the active material actually flows downward with gravity, until the anode and cathode eventually short out. I believe this is termed "zinc migration". Many companies have claimed to solve this problem (see Evercel) but were wrong. This effect plus dendrite growth yields a very short cycle life, making Ni-Zn unsuitable unless really cheap.