Preparation And Electrochemical Performance Study Of Novel Alkaliation Organic Cathode Materials

Compared with traditional inorganic cathode materials,organic cathode materials are considered to be the most promising materials,due to its low cost,rich variety,tunable molecular structures,and high specific capacity.However,most of reported organic electrode materials are in their oxidized state,and require initial reduction with alkali cations uptake.In addition,the anode materials need extra Li-metal or pre-lithiation carbon materials,which greatly increases the production cost.In contrast,alkaliation organic cathode materials are in the reduced state and contain alkali metal ions,thus not requiring a prior discharge process.Anodes can be selected from graphite or other carbon materials,and their battery configuration is si milar to commercial Li-ion batteries.However,research on organic cathodes materials for alkali ion batteries is still in its early stages,facing challenges such as pre-insertion of alkali-ions,low stability,and low energy density.Therefore,it is necessary to further strengthen the design of cathode materials and conduct in-depth research on the structure-performance relationship between materials and electrochemical reactions,revealing the essence and mechanism of electrode reactions,and providing guidance for material s design and optimization.Hence,two types of novel alkali metal organic cathode materials were designed and prepared by introducing strong electron-withdrawing groups and increasing molecular weight.One type is lithiated/sodiated carbonyl organic cathode materials（Li₄-phle-CH₃P,Na₄-phle-CH₃P,Li₄-phle-ph P,Na₄-phle-ph P,Li₄-Zn-DOBDP,and Na₄-Zn-DOBDP）.The other type is alkaliation conjugated diethylsulfonyl methanide organic cathode materials（Li₂-p-TESO₂,Na₂-p-TESO₂,and K₂-p-TESO₂）.The molecular structures was confirmed,and electrochemical properties in alkali metal ion batteries were explored,and revealed the reaction mechanism.This work suggests new ideas of design and modification of alkaliation organic cathode materials.The main research work is as follows:（1）Using 2,5-dihydroxy-1,4-benzenediphosphonic acid（H₆-DOBDP）as the parent molecule,a novel lithium/sodium carbonyl organic cathode material,A ₄-phle-CH₃P and A₄-phle-ph P（A=Li/Na）,was designed and synthesized by substituting the hydroxyl groups on the phosphonic acid groups with electron-donating groups（methyl and phenyl）.The electrochemical properties of A₄-phle-CH₃P and A₄-phle-ph P were systematically investigated.The solid lithium ion and sodium ion conductivity of A ₄-phle-ph P was analyzed and revealed its energy storage mechanism.The lithium and sodium storage electrochemical performance of A₄-phle-ph P was studied.At a high current density of 1C,Na₄-phle-ph P exhibited a reversible specific capacity of 41 m Ah g^-1 after 1000 cycles.（2）H₄-Zn-DOBDP DMF₂ MOF is synthesized by coordinating the hydroxyl group of H₆-DOBDP with Zn（II）in dimethylformamide solution.By optimizing the activation and deprotonation processes,a new type of lithiated and sodiated organic cathode material,A₄-Zn-DOBDP（A=Li/Na）was prepared.The effects of remove/uptake of DMF molecules and H⁺/Li⁺or H⁺/Na⁺exchange of H₄-Zn-DOBDP DMF₂ is discussed,and it manifests high reversibility.The intrinsic lithium and sodium ion conductivity properties of A₄-Zn-DOBDP were evaluated.As organic cathodes,Li₄-Zn-DOBDP exhibited a reversible capacity of 120 m Ah g^-1 after 100 cycles at a current density of0.1C,with a capacity retention rate of 90%.（3）Using the electron-withdrawing effect of sulfonyl group,a new type of alkaliation conjugated di-alkali p-phenylene-bis-diethylsulfonyl methanide A₂-p-TESO₂（A=Li/Na/K）was prepared by introducing sulfonyl group into the 1,4-phthalaldehyde.A₂-p-TESO₂exhibits good air stability and high redox potentials（3.13V vs.Li⁺/Li,2.81 V vs.Na⁺/Na,and 2.98 V vs.K⁺/K）.The liquid-phase and solid-phase electrochemical behavior of A₂-p-TESO₂ was revealed,and the universal application of the conjugated alkalia disulfonyl-methanide in alkali metal ion batteries were proposed and confirmed for the first time.