In Situ Electrochemical Synthesis Of Novel Lithiumrich Cathodes For Organic Li-Ion Full Batteries

Due to the limited choice of inorganic cathode materials,commercial lithium-ion batteries are close to the upper limit of practical energy density.At the same time,the environmental and cost problems of these inorganic cathode materials containing transition metal elements（such as CO/Ni/Mn）also accelerate the worldwide demand for more powerful,safer and greener electrode materials.Organic electrode materials with redox activity bring new prospects for the further development of lithium-ion batteries because of their high energy density and low cost.In order to make lithium-ion battery,the redox state of cathode material must match that of anode material.For example,in the whole battery manufacturing process,Li Co O₂ in the reduced state on the positive side must match with the oxidized material on the negative side,so the graphite in the oxidized state at first is the required anode material.At present,reduced organic cathode materials are very rare.In this paper,a novel organic molecule ABB4OLi was designed and synthesized as an organic cathode material,which has a theoretical specific capacity of256 m Ah g^-1 in lithium-ion batteries.Firstly,the synthesis of ABB4OLi was studied.In the first step,ABB4OMe was synthesized by Suzuki-Miyaura reaction with a yield of more than 90%;in the second step,ABB4OH was synthesized by boron tribromide demethylation with a yield of more than 80%.Unfortunately,the last step of ABB4OLi synthesis through acid-base neutralization is still unstable in air,so it can only be synthesized by in-situ reduction of protons in the battery.After a long time of exploration in the purification process of the synthesis part,the purification efficiency with comprehensive yield>80%can be achieved.Secondly,the process of in-situ synthesis of ABB4OLi by ABB4OH on the electrode sheet was studied.By comparing the effects of different conductive additives and electrolyte formula on the battery performance,the optimal formula was selected.When the conductive additive is ordered mesoporous carbon CMK and the electrolyte is 3 M Li TFSI in DME,ABB4OH can achieve the best electrochemical performance.For example,in half cell,ABB4OH can provide a high specific capacity of 343 m Ah g^-1 in the second cycle and an average capacity of 194 m Ah g^-1 in 250 cycles(at a low current density of 50 m A g^-1).Finally,the synthesis process of a new electrode material based on ABB4OH was discussed,and its application in sodium-ion and potassium-ion batteries was explored.In sodium-ion battery,PTCDI-DAQ can maintain 84%capacity retention rate after 1400cycles at low current,and can output a specific capacity of 133 m Ah g^-1 at an ultra-high current density of 10 A g^-1.The full cell based on PTCDI-DAQ can provide a high energy density of 295 Wh kg^-1_cathode,a high power density of 13800 W kg^-1_cathode and an ultra long life of over 30000 cycles.