Dithiolene Complexes of First-Row Transition Metals for Symmetric Nonaqueous Redox Flow Batteries.

ABSTRACT: Five metal complexes of the dithiolene ligand maleonitriledithiolate (mnt^2- ) with M=V, Fe, Co, Ni, Cu were studied as redox-active materials for nonaqueous redox flow batteries (RFBs). All five complexes exhibit at least two redox processes, making them applicable to symmetric RFBs as single-species electrolytes, that is, as both negolyte and posolyte. Charge-discharge cycling in a small-scale RFB gave modest performances for [(tea)₂ V_mnt ], [(tea)₂ Co_mnt ], and [(tea)₂ Cu_mnt ] whereas [(tea)Fe_mnt ] and [(tea)₂ Ni_mnt ] (tea=tetraethylammonium) failed to hold any significant capacity, indicating poor stability. Independent negolyte- and posolyte-only battery cycling of a single redox couple, as well as UV/Vis spectroscopy, showed that for [(tea)₂ V_mnt ] the negolyte is stable whereas the posolyte is unstable over multiple charge-discharge cycles; for [(tea)₂ Co_mnt ], [(tea)₂ Ni_mnt ], and [(tea)₂ Cu_mnt ], the negolyte suffers rapid capacity fading although the posolyte is more robust. Identifying a means to stabilize V_mnt ^3-/2- as a negolyte, and Co_mnt ^2-/1- , Ni_mnt ^2-/1- , and Cu_mnt ^2-/1- as posolytes could lead to their use in asymmetric RFBs.

SUBMITTER: Hogue RW 

PROVIDER: S-EPMC6852480 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature