Impact of Triethanolamine as an Additive for Rechargeable Alkaline Zn/MnO2 Batteries under Limited Depth of Discharge Conditions

Rechargeable alkaline Zn/MnO2 batteries are being developed for use as cost-effective grid-scale energy storage devices. Previous studies have shown that limiting the depth of discharge (DOD) of the MnO2 cathode extends cell lifetime while still providing a cost-effective battery system. Herein, a comprehensive study of triethanolamine (TEA) as an additive in Zn/MnO2 limited DOD batteries is provided by examining the effect of TEA in full cells as well as independently on the cathode, anode, separator, and electrolyte. Improvement in cycle-ability of the cathode (on average, 80% of cycled capacity remains after 191 cycles without TEA, 568 cycles with TEA) and a decrease in ionic zinc mobility across Celgard 3501 (7.91 × 10−5 cm2/min without TEA, 3.56 × 10−5 cm2/min with TEA) and Cellophane 350P00 (3.26 × 10−5 cm2/min without TEA, 4.74 × 10−6 cm2/min with TEA) separators upon the addition of TEA are demonstrated. However, TEA increased both the reduction potential of Zn (−0.68 V vs. Hg/HgO without TEA, −0.76 V with TEA) and the solubility of Zn2+ (0.813 M without TEA, 1.023 M with TEA). Overall, the addition of TEA extended the lifetime of limited DOD cells on average by 297%.