Chain Rigidity Modification To Promote The Electrochemical Performance Of Polymeric Battery Electrode Materials

Electrochemical energy storage possesses several desirable features,including pollution-free operation,high round-trip efficiency,and flexible power and energy characteristics to meet different functions,long cycle life,and low maintenance.However,many ex siting challenges of conventional inorganic materials limit its practical application.Organic materials are promising materials in electrochemical energy storage,because of their abundant elements,relatively low cost,flexible design,and environmental friendliness.However,the application of organic materials is still restricted by some issues,such as low power and/or eneygy density.This paper mainly focuses on the molecular design of organic materials and their application in electrochemical energy storage systems.The main contents as follow:(1)Three phenazine polymers with different chain rigidity were synthesized via a simple carbon-nitrogen coupling reaction and used in lithium ion batteries.The results indicated that the ionic conductivity of polymeric materials was the main limiting factor of the power density.The ionic diffusion coefficient was enhanced by orders of magnitudes if proper twisted group was introduced to interrupt the rigid backbone of the polymers.The polymer p-DPPZR1 with flexible chain not only achieved a highest power density of 3 kW L-1,but also had a high volumetric energy density up to 275 W h L-1,regardless of lower surface area and electrical conductivity compared the ones with more rigid chain structure.Such a strategy is seldom systematically investigated in previous studies but seems highly effective,and might be useful for the design of polymeric materials for practical organic batteries.(2)In this section,four iron-pyridine complexes were synthesized by simple routes and used in lithium redox flow batteries.All four complexes exhibited a reversible redox peak.They had higher diffusion coefficients(3.3-5.2×10-6 cm2 s-1)and electron transfer rates(3.5-6.6x10-3 cm s-1)than other reported organic materials.Li-redox flow batteries tests displyed that Fe[bpy-OCH3]3(BF4)2 with the ligand modified by-OCH3 had excellent cycle stability,and the energy density of which was up to 48 W h/L.