Conclusions:

CaSO₄ can be one of candidate for continuing the research

• the relative solubility in water can provide some SO₄ ^2- ions in solution

• increase the conductibility of the electrolyte
  
• the crystallization of PbSO₄ will be more easy due to the suprasaturation in SO₄ cations
  

• the similarity in crystallization system can provide seeds for crystallization for PbSO₄

• effective for the discharging process
• avoid the passivation of the surface

• the relative big difference in cell dimensions will make the PbSO4 crystal more instable and more easy to dissolve

• effective in the charging process
• avoid the premature sulfatation of the surface