Preparation Of Organic Electrode Materials And Study On Its Electrochemical Performance

Organic electrode materials are widely used in lithium-ion batteries due to their abundant resources,controllable electrode potential,green environmental protection,and strong designability.However,there are some fundamental problems need to be solved for organic electrode materials,such as the dissolution into the electrolyte,which may be result in poor structural stability and rapid capacity decay.In addition,poor conductivity resulting in unsatisfactory real specific capacity.This article focuses on increasing the conductivity of organic electrode materials and solving the material’s solubility.The main contents and results are as follows:the preparation of metal salts of small molecular carbonyl compounds can increase the polarity of the material and ease the solubility behavior of organic materials in organic electrolytes.Therefore,2,6-naphthalenedicarboxylic acid（2,6-NDCA）was synthesized into 2,6-naphthalenedicarboxylic acid salts through the mechanism of acid-base neutralization reaction with different metal substitutions:2,6-naphthalenedicarboxylic acid dilithium salt（2,6-Li₂NDC）,2,6-naphthalenedicarboxylic acid dinaphthalate（2,6-Na₂NDC）,2,6-naphthalenedicarboxylic acid dipotassium salt（2,6-K₂NDC）.Combined with characterization and electrochemical performance to study the effect of different metal substitutions on the electrochemical performance of electrode materials.The results show that this type of carboxylic carbonyl compound can reversibly store lithium.It is worth noting that 2,6-Li₂NDC has the best cycle performance and rate performance.The mainly reason is that the material has many surface defects and active sites,which leads to better electrochemical properties.In order to expand the application field of organic electrode materials,2,6-K₂NDC was applied to the anode material of potassium ion batteries.The results show that 2,6-K₂NDC reversibly discharges and recharges through the opening and recovery of conjugated carbonyl groups,and its’cycle performance and rate performance are also excellent.However,the conductivity of the organic electrode material is poor.To solve the problem,2,6-K₂NDC was modified by adding conductive materials.The 2,6-K₂NDC and GO were compounded by a hydrothermal drying method at a mass ratio of 4:1 to explore the electrochemical performance.The results show that its electrochemical performance is improved.In order to further explore the ratio of the composite material,the mass ratio of 2,6-K₂NDC and GO was changed to 5:1 and 3:1.The results show that the capacity decreases greatly during long cycle and the structure is extremely unstable.Therefore,the optimal mass ratio of composite is 4:1.Considering the characteristics of wide sources and abundant resources of organic materials,the metal phthalocyanine compound-nickel phthalocyanine tetrasulfonate tetrasodium was selected as the negative electrode material for lithium ion batteries to explore its morphological structure characteristics,lithium storage performance and electrochemical reaction mechanism.The molecular structure of TsNiPc is highly conjugated and has many active sites,which is conducive to conducting materials.Moreover,the presence of sodium sulfonate groups in the molecular structure helps to improve the dissolution of organic materials in organic electrolytes.In order to further improve the conductivity of the material,TsNiPc and GO are compounded at a mass ratio of 4:1 to obtain the composite material TsNiPc@GO.Compared to TsNiPc,the results show that after compounded GO,the morphology of TsNiPc changed from granular to flexible layered structure,theπ-πeffect appeared in the composite material and the molecular structure was more stable,which result in a significant improvement in its electrochemical performance.Through ex-situ infrared testing,it can be seen that TsNiPc becomes a more stable structure through ion replacement at first,and then begins to realize reversible electron transfer.