Application Of Perylene-Tetracarboxylic Dianhydride-Based Organic Cathode In Lithium/Potassium-Ion Batteries

The application of inorganic electrode materials in the secondary batteries still has some urgent problems to be solved,such as cost and environmental protection.In the development of resource-rich and large-radius rechargeable metal-ion batteries(Na⁺,K⁺,Al³⁺,etc.),inorganic electrode materials also show the problems of volume expansion and structure destruction.These questions have led researchers to conduct extensive research on organic batteries,because organic molecules interact mainly by Van der Waals forces,each molecule can independently store electrons and metal ions when redox occurs in organic rechargeable batteries.However,there are serious dissolution problems of organic molecules in organic liquid electrolytes and the solvent molecules in the electrolyte are co-embedded into organic solids.In this work,a novel small organic molecule 1,1-（1,4-phenylene）-bis（perylene-3,4,9,10-tetracarboxylic dianhydride）（2PTCDA）was designed and synthesized,and its electrochemical performance in lithium/potassium-ion batteries were explored.Firstly,this work used the commercial organic material PTCDA to prepared2PTCDA through a circuitous synthesis route.The material characterization and solubility testing showed that high purity and poorly-insoluble 2PTCDA in common organic solvents was successfully prepared.In the following sections,the electrochemical performance of 2PTCDA in lithium-ion batteries under liquid electrolyte was explored,and it was found that the capacity decay of the batteries decreased with the increase of the electrolyte concentration.Combined with the color of separators after cycling and solubility testing,the possibility of 2PTCDA dissolution was excluded.In order to get rid of the influence of solvent molecules,the polymer-based solid-electrolyte lithium-ion batteries were further explored.The peak capacity is 119 m Ah/g and the median voltage is 2.2 V at 60℃.Finally,the cathode performance of 2PTCDA was tested in potassium-ion batteries.Among the six common electrolytes,2PTCDA showed very clear discharge-charge potentials and satisfactory specific capacities（120-137 m Ah/g）in K-ion half cells,showing good electrolyte compatibility.Based on the excellent electrochemical performance of half cells in ester and ether electrolyte respectively,the reduced state（K₄TP）of the K₂TP is selected as the starting organic anode to build the all-organic potassium-ion batteries.The peak discharge capacity is 126 m Ah/g（taking the cathode as the calculation standard）,the median voltage is 1.76 V,and the corresponding peak energy density is about 229 Wh/kg.