Preparation Of Porphyrin-based Conjugated Microporous Polymer And Its Application In Li-ion Batteries

Porphyrin-based molecules have attracted considerable interests for using as anodes in Li-ion batteries,because of their largeπ-conjugated aromatic structures,abundant active sites with multi-electron redox activities,and narrow HOMO–LUMO gaps.To increase the utilization of active sites,enhance electrical conductivity,and inhibition of dissolution in electrolyte,here,two porphyrinic conjugated microporous polymer was prepared through the Sonogashira-Hagihara cross-coupling reaction of Br-functionalized porphyrinic monomer and alkynyl-based monomer,its application in lithium-ion batteries was studied,and its electrochemical mechanism was explored.The main research contents are as follows:1.Tetrabromo-porphyrin-based conjugated microporous polymer（CMP-4Br Por）was prepared by Sonogashira-Hagihara cross-coupling reaction using tetrabromo-methoxy porphyrin（4Br Por）and 1,4-diacetylene as monomers.The polymerized CMP-4Br Por has smaller band gap than4brpor due to the introduction of long conjugated chains.When used as a cathode material,it has a specific capacity of 90 m Ah g^-1 at a current density of 0.2 A g^-1 until 1000 cycles.Its charge-discharge curve shows that its discharge platform is mainly below 1v.When applied to the anode,the capacity can gradually increase from the initial 262 m Ah g^-1 to 929 m Ah g^-1at the 1000th cycle at 1.0 A g^-1 cycle,and the average Coulombic efficiency（CE）exceeds 99%.It is preliminarily proved that the porphyrin-based conjugated microporous polymer is a potential anode material,and the low band gap brought by the long conjugated chain is beneficial to the battery performance.2.Dibromoporphyrin-based conjugated microporous polymer（CMP-2Br Por）,diphenyl linear polymer（LP-1）and dibromoporphyrin-based linear polymer（LP-2）.The results of experimental tests and theoretical calculations indicate that CMP-2Br Por has a narrower band gap due to the introduction of porphyrin and porous structure.CMP-2Br Por provides a specific capacity of 1200 m Ah g^-1 at 1 A g^-1 and a capacity retention of 230%after 2000 cycles at 6 A g^-1 when used as the anode of Li-ion batteries.This excellent performance is due to synergistic effect of porphyrin moiety and porous polymer,which can be compared with the state-of-the-art organic anode materials.The ex situ X-ray photoelectron spectroscopy tests reveal all of the porphyrin center,benzene ring and alkynyl parts of the polymer can be reduced for Li storage during the cathodic process.CMP-2Br Por provides a specific capacity of 200 m Ah g^-1 at 1 A g^-1 when used in solid-state batteries with no capacity degradation after 400 cycles.This result indicates that CMP-2Br Por is potential candidate to construct all-polymer-based flexible batteries for wearable devices,etc.