Systematic cycle life assessment of a secondary zinc–air battery as a function of the alkaline electrolyte composition

Abstract

Development of secondary zinc–air batteries goes through a proper specification of the electrolyte formulation adapted to extend the cycle life of the battery. However, defining an optimal formulation is not a trivial work due to the specific requirements for each electrode. At half‐cell level, it has been determined that ZnO‐saturated 4 mol L−1 KOH with 2 mol L−1 KF and 2 mol L−1 K2CO3 (4s‐2) is the most suitable formulation to increase the cycle life of secondary zinc electrode, whereas additive‐free 8 mol L−1 KOH (8‐0) formulation is more beneficial for the bifunctional air electrode (BAE). Through this systematic cycle life assessment, it has been found that the most suitable electrolyte formulation for the full cell system is a compendium for both electrodes requirements. It has determined an optimal electrolyte formulation for the full system consisting of ZnO‐saturated 7 mol L−1 KOH with 1.4 mol L−1 KF and 1.4 mol L−1 K2CO3 (7s‐1.4). This electrolyte composition increases at least 2.5 times the reversibility of the secondary zinc–air battery in comparison with that employing the traditional formulation for primary zinc–air batteries (additive‐free 8 mol L−1 KOH). In addition, the development of a proper cell design or separator is also necessary to further enhance the secondary zinc–air cycle life.

Translating Materials-Level Performance into Device-Relevant Metrics for Zinc-Based Batteries

“…For example, a new electrolyte additive to control deposition/dissolution at a zinc electrode may show promise in flooded half-cell or beaker cell tests, but the same electrolyte composition needs to be compatible with (or even beneficial for) the positive electrode with which that zinc anode will be paired. 18 To obtain the most relevant results, new electrolyte compositions should be tested in full-cell prototypes with the desired cathode (e.g., nickel as NiOOH), 19 where easily measured parameters such as cycle life, round-trip efficiency, and stable voltage window will reflect the ensemble behavior of the cell components.…”

Designing Aqueous Organic Electrolytes for Zinc–Air Batteries: Method, Simulation, and Validation

“…Table 2 lists the properties of the as‐prepared electrolyte compared with previously reported values for aqueous ZAB electrolytes KOH and NH 4 Cl–ZnCl 2 . The properties of the proposed electrolyte are measured at three pH values: 8, 9, and 12.…”

“…2020, 10,1903470 electrolyte are experimentally characterized to investigate and validate these predictions. Table 2 lists the properties of the as-prepared electrolyte compared with previously reported values for aqueous ZAB electrolytes KOH [64][65][66][67] and NH 4 Cl-ZnCl 2 . [23] The properties of the proposed electrolyte are measured at three pH values: 8, 9, and 12.…”

“…All models with their requisite parameters are described in the Supporting Information. [41,57,60,[64][65][66][67]…”

“…Values for NH4 Cl-ZnCl 2 are reported in ref [23],. and values for KOH are reported in refs [64][65][66][67]…”