Application Of Disulfonate-substituted 9,10-anthraquinones As Organic Positive Electrodes In Sodium-ion Battery

Due to the extensive storage of sodium?Na?element in the earth's crust and low cost,Na-ion battery has received more and more attention from researchers in battery field.Organic materials have the characteristics of low cost and green sustainability.Therefore,organic sodium-ion battery with the above advantages has become the most promising next-generation battery system.Quinones of organic materials have the advantage of high energy density.However,because of the good solubility of small-molecule materials in organic electrolytes,they face poor cycle-stability issues.Because organic materials have a wide variety of design features,this paper presents the concept of insoluble polyanionic organic cathode materials to solve the problem of solubility for small organic molecules.Herein,the sodium sulfonate group was substituted for the hydrogen atom on anthraquinone to delay its solubility in organic electrolyte.Finally,we chose sodium 9,10-anthraquinone-2,6-disulfonate?Na₂AQ26DS?and sodium 9,10-anthraquinone-2-disulfonate?NaAQ2S?as active materials for organic sodium-ion batteries.This paper explores the effect of the binder on the performance of the electrode and the battery.The LA133 binder is more stable than the PVDF binder to adhere active materials,and thus the battery has a better specific capacity under the same test conditions.Meanwhile,this paper further studies the effect of different electrolytes on battery performance of Na₂AQ26DS,and it was found that the performance of batteries using ether electrolytes was much better than that of ester electrolytes;Furthermore,the effect of different conductive additives on battery performance was explored,and the results confirmed that a single carbon material could not fully exhibit the performance of Na₂AQ26DS and the use of two carbon materials as the composite conductive additives can improve battery performance.Therefore,we can effectively improve the electrochemical performance of the Na-ion battery by using Ketjen Black and carbon nanotube composite carbon materials.Using 1 M NaPF₆ in DME electrolyte,the battery reached the best performance in this paper.The battery results show that Na₂AQ26DS has excellent performance in batteries.Under the test conditions of low current(50 mA g^-1),the battery showed a specific capacity of 137 mAh g^-1.After 300 cycles,the battery still has a high capacity of nearly120 mAh g^-1;At the high current(1 A g^-1)cycle test,the capacity still remains 99 mAh g^-1 after 1000 cycles,which is 92%and 76%of the theoretical specific capacity(C_T=130mAh g^-1).The results show that Na₂AQ26DS has very good cycle stability in the battery,proving that polyanionization of small organic molecules is indeed an effective method to solve the cycle stability.At the same time,this paper also explores the performance of NaAQ2S in sodium-ion batteries.The battery does not reach the theoretical specific capacity of NaAQ2S,and the cycle stability of the battery is very poor.The results indicate that single anionized organic small molecules cannot significantly improve the electrochemical performance in sodium-ion batteries.