Synthesis and performance evaluation of binuclear metal phthalocyanines as high-efficiency electrocatalysts for Li/SOCl
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ARTICLE Synthesis and performance evaluation of binuclear metal phthalocyanines as high-efficiency electrocatalysts for Li/SOCl2 batteries Yuanyuan Su,c) Ying Zhang,c) Ronglan Zhang,a) Fei Yang, and Jianshe Zhaob) Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi’an, Shaanxi 710069, People’s Republic of China (Received 18 May 2018; accepted 25 June 2018)
Two series of binuclear metal phthalocyanine complexes M2(PcTN)2Nap and M2(PcTA)2Nap (M 5 Mn21, Fe21, Co21, Cu21) were designed and synthesized through the liquid solvent method and amination reaction. Elemental analysis, IR, and UV-vis spectroscopy were applied to characterize the compounds. To evaluate their catalytic performance, all the compounds were respectively added into the electrolyte of Li/SOCl2 battery systems as well as three-electrode systems for cyclic voltammetry (CV) measurements. The research studies indicate that the average discharge voltage and discharge time of the battery could be effectively enhanced by 0.2440 V and 810.7 s when compared with the battery in the absence of the compounds. As for capacities of the batteries containing catalysts, they were also found to have an improvement of 51.78–91.62%. Among the effects of diverse metal ions on the catalytic performance of phthalocyanines, the complexes whose center metal ions were Mn21 or Co21 exhibited relatively high catalytic performance. Meanwhile, combined with experimental results of CV analyses, the suggested catalytic mechanism of binuclear phthalocyanines for catalyzing Li/SOCl2 batteries had been proposed.
I. INTRODUCTION
Lithium/thionyl chloride batteries are widely used due to their high specific capacity, low self-discharge rate, and long life in the storage, but their discharge voltage and low temperature discharge performance still need to be improved.1–3 The shortages greatly impede their practical applications in some fields, especially the fields of urgently requiring high power batteries.4–6 The Li/SOCl2 battery treats carbon membrane as the cathode, lithium as the anode, and tetrachloride aluminum lithium and thionyl chloride (LiAlCl4/SOCl2) as the electrolyte. And the battery reactions are as follows: Anode: 4Li ! 4Liþ þ 4e
:
Cathode: 2SOCl2 þ 4e ! SY þ SO2 [ þ 4Cl
ð1Þ : ð2Þ
Simultaneously, Li1 will combine with Cl to form the LiCl precipitate: 4Liþ þ 4Cl ! 4LiClY :
ð3Þ
Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] c) These authors contributed equally to this work. DOI: 10.1557/jmr.2018.238 J. Mater. Res., 2018
Overall reaction: 2SOCl2 þ 4Li ! SY þ SO2 [ þ 4LiClY : ð4Þ
During the discharging, the active molecule SOCl2 that is absorbed by the electrode could give rise to a disproportionation reaction. Meanwhile, Li1 could turn into the LiCl film through reacting with Cl, which reduces the selfdischarge and improves the storage period of the battery. However, the S sediment and LiCl film tha
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