Design And Synthesis Of Novel Branched Organic Electrode Materials And Their Rate Performance

Organic electrode materials have attracted much attention because of their environmental friendliness,flexible and designable molecular structure.However,due to the low electrical conductivity of most organic materials,the rate performance of organic batteries remain to be improved.Extending the conjugated structure of organic electrode materials can promote the electronic and ionic transport,and thus is helpful to improve the rate performance of organic batteries.However,the current reports mainly focus on extending the conjugated structure from a one-dimensional perspective.In this paper,we extend the conjugated structure from the two-dimensional perspective,design and synthesize two novel branched materials,and have successfully improved the rate performance of organic batteries.The specific research contents are as follows:(1)We polymerize tetraaminobenzoquinone with 2,5-dihydroxy-1,4-benzoquinone and cyclohexanone by rational molecular design,respectively,to obtain a linear conjugated polymer(LCP)and a branched conjugated polymer(BCP),and apply them as anodes for sodium-ion batteries.Compared with LCP,BCP has larger and branched conjugated structure,which promotes the electronic and ionic transport,and thus the BCP anode shows more capacitive contribution in the Na-storage process and better rate performance,with capacities up to 450 m Ah g^-1 at 0.1 A g^-1 and 330 m Ah g^-1 at 10 A g^-1.Besides,the capacity and rate performance of BCP anode surpass many reported organic polymeric anode materials for sodium-ion batteries.(2)We further design and synthesize a novel dihydrophenazine-based branched cathode material p-TPPZ,and achieve high rate performance and high energy density simultaneously.P-TPPZ has higher electrical conductivity and ionic diffusion coefficient than the linear polymer p-DPPZ,and shows superior rate performance when used as the cathode material for lithium-ion batteries.The p-TPPZ cathode exhibits a specific discharge capacity of 170 m Ah g^-1 at 0.5 C,with the energy density of 618.2 Wh kg^-1.Under the high power density of 23725 W kg^-1(40 C),the energy density still reaches474.5 Wh kg^-1.In addition,p-TPPZ cathode shows higher voltage than p-DPPZ cathode,with an average discharge voltage up to 3.65 V,which is due to its lower HOMO level according to the theoretical calculation.The excellent electrochemical performance of p-TPPZ cathode not only exceeds p-DPPZ cathode and many anion-insertion organic cathode materials,but also can be comparable to commercial inorganic cathode materials.In this paper,we design and synthesize two novel branched organic electrode materials and improve the rate performance of the batteries successfully.Both electrodes exhibit excellent electrochemical performance,which are superior to the reported organic electrode materials.In addition,we reveal the internal mechanism of the branched electrode materials to improve the rate performance through a series of characterization tests.This paper would stimulate the further molecular design for high performance organic electrode materials.