Rheological phase reaction synthesis and electrochemical performance of rufigallol anode for lithium ion batteries

1,2,3,5,6,7-hexahydroxy-anthraquinone (rufigallol) and its metal–organic complex (rufigallol-Li/Ni, R-LN) were both synthesized. The electrochemical performance investigation of rufigallol and R-LN as anodes for lithium ion batteries indicates that pure rufigallol delivers high initial capacity but poor cycling stability, by contrast, the R-LN complex exhibits high initial capacity and excellent cycling stability.

Rufigallol was synthesized by rheological phase method with high yield and investigated as anode for lithium ion batteries.

Lithium ion batteries (LIBs) have proven to be clean and efficient energy-storage technologies to meet the growing demand for green and sustainable electric power storage. Considering the sustainability, low cost, abundant natural sources, structural design with tolerance for variable functional groups, fast reaction kinetics and high power density, organic electrode materials have been the most competitive alternative to traditional inorganic materials.^1–6 Quinone organic materials with carbonyl functional group have received great concern for their high theoretical capacities and reaction reversibility. While, the dissolution of small molecule quinones in the organic electrolyte and the resulting capacity attenuation have restricted their application. Therefore, it is urgently demanded to design new organic electrode materials with high energy efficiency and good cycling stability. Among small molecule quinones, 1,2,3,5,6,7-hexahydroxy-anthraquinone (rufigallol) as a critical component has been widely used in dye industry, drug synthesis, and organic materials.^7–10 Rufigallol was firstly synthesized in 1836.¹¹ Since then, very little efficient method for the preparation of rufigallol has been reported. Recently, Bisoyi and Kumar''s research indicates that the rufigallol can be achieved by self-condensation of gallic acid in the presence of sulfuric acid under microwave-assisted, and the yield reached 86%.¹² Also, as far as we know, there is no correlative literature exists about rufigallol being used as electrode materials for lithium ion batteries.It is well-known that the dissolution of organic molecule in the electrolyte can be effectively suppressed via salt formation. Therefore, constructing the metal–organic complex is an efficient way to obtain a stable and flexible framework as well as a better cycling stability.^13–19 In our previous study,^20,21 we have successfully realized the improvement of cycling stability for 3,4,9,10-perylene-tetracarboxylic acid-dianhydride (NTCDA) through the introducing of Li/Ni or Co/Mn to the matrix material. The obtained metal–organic complex, namely, Li/Ni-1,4,5,8-naphthalenetetracarboxylate or Co/Mn-1,4,5,8-naphthalenetetracarboxylate, showed a high specific capacity and a good cycling stability.Herein, we developed a simple, economical and effective rheological phase method²² to synthesize the rufigallol with high yield and investigated its electrochemical application in lithium ion batteries. In view of the easily connecting of hydroxyl groups in aromatic carbonyl compound for rufigallol with metal ions, in order to modify the cycling stability of pure rufigallol, we synthesized rufigallol-Li/Ni complex (R-LN) through the introducing of lithium and nickel by a hydrothermal method. When used as the LIBs anode, rufigallol shows initial discharge and charge capacities of 977 mA h g⁻¹ and 460 mA h g⁻¹, respectively, which is far higher than that of traditional graphite anode. The R-LN complex delivers initial a charge capacity of 560 mA h g⁻¹ and still remain at about 500 mA h g⁻¹ after 100 cycles, indicating a good electrochemical performance. Our work presents a new quinone-based organic materials with high capacity and competitive cycling stability, which enriches the organic electrode materials.