Optimizing interfacial process of Mg metal anode by porphyrin adsorption layer in Cl-free conventional electrolyte

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2024-02, Vol.481, p.148170, Article 148170
• Main Authors: Zhuang, Yichao, Wu, Jiayue, Hua, Haiming, Wang, Fei, Wu, Dongzheng, Xu, Yaoqi, Zeng, Jing, Zhao, Jinbao
• Format: Article
• Language: English
• Subjects: Adsorption layer; Cl-free conventional electrolyte; Mg metal anode; Mg2+ solvation optimization
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2023.148170

[Display omitted] •Improving Mg metal battery performance in conventional electrolyte by porphyrin.•The analysis reveals the mechanism of how porphyrin enhances the battery performance.•The porphyrin molecules adsorbed on anode to alleviate the passivation of Mg metal.•The porphyrin additive reorganizes the Mg2+ solvation sheath near the interface. The viability of Mg metal batteries is severely threatened by the passivating instinct of Mg metal in Cl-free conventional electrolytes. To realize the reversible Mg stripping/plating in the conventional electrolyte, 5,10,15,20-tetraphenylporphyrin (TPP) with planar structure and strong adsorption ability is added into electrolyte to optimize the interfacial process by constructing a dynamic molecular adsorption layer on Mg anode, which is different from the method of tailoring artificial solid electrolyte interphases to facilitate Mg2+ transport. On one side, TPP molecules served as a protective layer to avoid the direct contact between Mg anode and passivation-inducing factors from electrolyte, alleviating passivation effectively. On the other side, a locally high concentration of TPP is created near the Mg surface for Mg2+ solvation sheath reorganization. Theoretical calculations verify that [MgTPP(DME)2] in TPP-containing electrolyte possesses higher stability and a lower energy barrier than [Mg(DME)3]2+ during desolvation, further alleviating passivation and reducing the overpotential of Mg metal. Consequently, the Mg symmetrical battery exhibits a reduced polarization voltage of 0.6 V from ∼ 2 V and a longer cycling life of over 500 h. With TPP-containing electrolyte, the Mg||V2O5 full battery presents a higher initial capacity of 186.5 mAh/g, which confirms the practicability of this additive strategy.