Effects of Central Metal Ion on Binuclear Metal Phthalocyanine-Based Redox Mediator for Lithium Carbonate Decomposition

Qinghui Yan; Linghui Yan; Haoshen Huang; Zhengfei Chen; Zixuan Liu; Shaodong Zhou; Haiyong He

doi:10.3390/molecules29092034

Effects of Central Metal Ion on Binuclear Metal Phthalocyanine-Based Redox Mediator for Lithium Carbonate Decomposition

Molecules. 2024 Apr 28;29(9):2034. doi: 10.3390/molecules29092034.

Authors

Qinghui Yan^{1

2}, Linghui Yan³, Haoshen Huang⁴, Zhengfei Chen⁴, Zixuan Liu^{4

2}, Shaodong Zhou³, Haiyong He²

Affiliations

¹ School of Materials Science and Chemical Engineering, Ningbo University, Ningbo 315211, China.
² Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China.
³ College of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310058, China.
⁴ School of Biological and Chemical Engineering, NingboTech University, Ningbo 315100, China.

Abstract

Li₂CO₃ is the most tenacious parasitic solid-state product in lithium-air batteries (LABs). Developing suitable redox mediators (RMs) is an efficient way to address the Li₂CO₃ issue, but only a few RMs have been investigated to date, and their mechanism of action also remains elusive. Herein, we investigate the effects of the central metal ion in binuclear metal phthalocyanines on the catalysis of Li₂CO₃ decomposition, namely binuclear cobalt phthalocyanine (bi-CoPc) and binuclear cobalt manganese phthalocyanine (bi-CoMnPc). Density functional theory (DFT) calculations indicate that the key intermediate peroxydicarbonate (*C₂O₆^2-) is stabilized by bi-CoPc²⁺ and bi-CoMnPc³⁺, which is accountable for their excellent catalytic effects. With one central metal ion substituted by manganese for cobalt, the bi-CoMnPc's second active redox couple shifts from the second Co(II)/Co(III) couple in the central metal ion to the Pc(-2)/Pc(-1) couple in the phthalocyanine ring. In artificial dry air (N₂-O₂, 78:22, v/v), the LAB cell with bi-CoMnPc in electrolyte exhibited 261 cycles under a fixed capacity of 500 mAh g^-1_carbon and current density of 100 mA g^-1_carbon, significantly better than the RM-free cell (62 cycles) and the cell with bi-CoPc (193 cycles).

Keywords: Li2CO3 decomposition; binuclear metal phthalocyanine; density functional theory; lithium–air batteries; redox mediator.

Abstract

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