Application Of Ployanionic Sodium Sulfonate Substituted 9,10-Anthraquinone As Organic Cathode In Li-ion Batteries

The transition elements（Co/Ni/Mn）in inorganic cathode materials are non-renewable resources,which cause serious environmental concerns.Therefore,it is very urgent to search the next generation cathode materials for green and sustainable LIBs.Organic redox-active compounds are emerging to be the most promising cathode materials for the next-generation LIBs because of their low cost,high energy density,structural diversity and green sustainability.Due to the excellent solubility of organic small molecule organic active materials in organic electrolyte,the cycling stability of the battery made of organic small molecule organic active materials is very poor.The cycling stability problem caused by solubility hinders the development of organic small molecule organic electrode materials in practical application.In order to solve the problem of solubility of organic small molecules,based on the principle of"like dissolves like",this work selected 9,10-anthraquinone-2,6-disulfonic acid（Na₂AQ26DS,theoretical specific capacity of 130m Ah/g）as the cathode material of organic LIBs（OLIBs）.Notably,Na2AQ26DS bears two strong ionic Na-O bonds and a large p-conjugated AQ skeleton,so that the polyanionic Na₂AQ26DS organic cathode material is insoluble in traditional organic electrolytes.The main research contents are as follows:Firstly,this work studies the influence of binder on the performance of Li-ion half cells.The experiment results exhibit that the LA133 binder is more stable to adhere the active materials compare to PVDF,and show better battery performance under the same test conditions.Secondly,the influence of conductive additives and electrolytes are explored.Using the composite conductive additives for Ketjen Black with carbon nanotubes the can better improve the capacity and stability of the battery.And the Li-ion half cells show the best performance by using 1 M bis（trifluoromethanesulphonyl）imide lithium salt（Li TFSI）in DOL/DME.Under these optimal conditions,Na₂AQ26DS（1-3.9 V vs.Li⁺/Li）delivers a highly stable specific capacity of 123 m Ah/g at 50 m A/g,along with a capacity retention of 75%during 900 cycles（6 months at least）and realizes a reversible average specific capacity of 69 m Ah/g for 2800 cycles at a high density of 500 m A/g.Finally,due to the excellent performance in Li-ion half cells,the pure organic rocking-chair full organic Li-ion cells are fabricated by using the reduction state（Li₄TP）of the air-stable lithium terephthalate（Li₂TP）as the starting organic anode while Na₂AQ26DS as the cathode.The resulting Li₄TP II Na₂AQ26DS organic LIBs can exhibit a highly stable average discharge capacity of 120 m Ah/g_cathode during 100 cycles at 50m A/g and the average discharge specific capacity of 63 m Ah/g_cathode with a long lifespan over 1200 cycles at a high density of 500 m A/g in 0.2-3.3 V.