Magnesium Storage Properties And Mechanism Of Organic Carbonyl Cathode Materials For Magnesium-ion Batteries

With the promotion of new energy vehicles and the development of mobile electronic equipment,more and more requirements are putted forward for the energy storage devices.Due to the rising price and the shortage of lithium metal resources,the development of rechargeable lithium-ion batteries has reached a bottleneck.Benefiting from the high volumetric energy density and dendrite-free growth of magnesium metal anode in general,rechargeable magnesium-ion batteries become a promising next-generation energy-storage system.However,due to each magnesium ion carries two positive charges,there is a strong interaction between magnesium ions and host materials.This results in sluggish diffusion kinetics,less discharge capacity and poor cycling performance of the cathode materials,affecting the overall performance of the batteries.Exploring the cathode materials with excellent electrochemical performance and fast diffusion kinetics of magnesium ions for magnesium-ion batteries is of great significance.Organic electrode materials have the characteristics of flexible structure and rich raw materials,have been widely studied in alkali metal ion batteries.However,there are few reports about the application of organic materials on magnesium-ion batteries.In this paper,two kinds of organic carbonyl compounds were used as the research objects.The phase and morphology of these materials were characterized by modern testing methods,and their electrochemical properties were tested as cathode materials of magnesium-ion batteries.The main research results are as follows:(1)Confirming 3,4,9,10-perylenetetracarboxylic dianhydride(PTCDA),as a kind of organic carbonyl compound,which can serve as the cathode material of non-aqueous magnesium-ion batteries.The dissolution issue of PTCDA in the electrolyte is inhibited by introducing the dissolvable salt,which achieves better magnesium-storage performance.Combined with Fourier transform infrared spectrum,ultraviolet-visible absorption spectrum and scanning electron microscope,the behavior of dissolution inhibition with dissolvable salt was directly observed and measured.In addition,the dissolution inhibition behavior can also be achieved by adding other dissolvable salts(KCl and Na Cl)into the all phenyl complex electrolyte.(2)The non-aqueous magnesium-ion batteries were assembled with PTCDA as the cathode and magnesium metal foil as the anode.The electrochemical performance of the assembled coin cells were tested in the voltage range between 0.6–2.5 V vs.Mg²⁺/Mg.The PTCDA electrode achieves a reversible capacity of 126 m Ah g^–1 at a current density of 200 m A g^–1,excellent rate performance and good cycling stability.The diffusion coefficient of magnesium ions in PTCDA was calculated by cyclic voltammetry and galvanostatic intermittent titration technique tests.In addition,the magnesium-storage mechanism of PTCDA and the structural evolution during the charge/discharge processes were also analyzed by in-situ phase and functional group characterization.The types of intercalated ions were analyzed by X-ray energy dispersive spectrometer,X-ray photoelectron spectroscopy and inductively coupled plasma emission spectroscopy.(3)Another organic carbonyl compound,2,3-diamino-1,4-naphthoquinone(DANQ),was synthesized and characterized.The magnesium-ion batteries were assembled with DANQ as the cathode,and the electrochemical performance was tested in the voltage range between 0.1–2.4 V vs.Mg²⁺/Mg.After 30 cycles,the discharge capacity can retain 70 m Ah g^–1 at the current density of 30 m A g^–1.