Study On Magnesium Storage Mechanism Of Organic Anode Material And Performance Of Mg-based Dual Ion Battery

Lithium ion batteries are the most mature and widely used energy storage devices in the field of energy storage.However,due to the limited lithium resources that can be mined globally,the cost of lithium-ion batteries is increasing year by year,so there is an urgent need to develop new low-cost energy storage devices with rich raw material resources.Magnesium resources are abundant,and as the negative electrode of the secondary battery,high energy density and safety can be obtained,which makes the magnesium ion battery become a hot spot in the research of new energy storage batteries.However,the current research on magnesium ion batteries is still in its infancy,and one of the main reasons is that there is a strong Coulomb interaction between Mg²⁺with a large charge density and the electrode material,which seriously hinders the diffusion of Mg²⁺in the material lattice.Furthermore,the specific capacity and rate performance of magnesium ion batteries are severely limited.On the other hand,due to its advantages of high voltage,environmental friendliness and low cost,the dual-ion battery has become a research hotspot of new energy storage devices today.The battery system reversibly intercalates in the graphite positive electrode layer through anions in the electrolyte Reaction,alloying of metal cations in the negative electrode or intercalation reaction to achieve charge and discharge.However,the current internal reaction mechanism in dual-ion batteries is relatively complicated.In addition to analyzing the reaction mechanism through experiments,the combination of theoretical calculations can not only save a lot of resources and funds,but also help people find experiments that are not easy to observe in experimental research.Phenomenon and internal reaction mechanism further guide the design and optimization of the battery structure.Based on the above analysis,this paper first prepares the numerical simulation of the dual-ion battery,and then conducts experiments to study the performance and reaction mechanism of the magnesium-based dual-ion battery.The specific research contents are as follows:First,this paper establishes the Newman model to conduct a numerical simulation of the dual ion battery using graphite as the positive and negative electrode materials to clarify the working mechanism of the dual ion battery.Specifically,based on the Newman model,this paper simulates the dual graphite electrodes and the electrolyte is 1 M lithium trifluoromethyl sulfonylimide lithium?LiTFSI??ethylene carbonate EC:diethyl carbonate DEC=1:1?ion battery system.In addition,the effects of the particle size of the positive electrode material and the electrolyte concentration on the capacity and rate performance of the dual-ion battery during charge and discharge were also investigated.By comparing the ion concentration distribution and liquid phase diffusion of the positive electrode material particles during the discharge of the dual-ion battery and electrochemical reaction rate,analysis of the mechanism of graphite particle size change and electrolyte concentration affecting the performance of dual-ion batteries,thus it provides a theoretical fundamental for the development of dual-ion batteries.In addition,this paper combines the advantages of dual-ion batteries and magnesium-ion batteries to build a magnesium-based dual-ion battery?Mg-DIB?.On the one hand,it uses an organic material with a mild reaction,low cost,easy availability,and good safety.To complete the rapid deintercalation in the graphite cathode,and thus make the constructed Mg-DIB have the advantages of high energy density,excellent rate performance and good cycle stability.In this work,3,4,9,10-perylenetetracarboxylic diimide?PTCDI?was used as the organic negative electrode,expanded graphite?EG?with high reaction potential and rapid anion intercalation was used as the positive electrode,and ionic liquid was used as Electrolyte,a magnesium-based dual ion battery was constructed,and its electrochemical performance was characterized.At the same time,first-principle calculation and in-situ characterization methods were effectively combined to further study its electrochemical reaction mechanism.Through in-situ infrared characterization,it was found that PTCDI undergoes a three-coordination mechanism and hydrogen bond formation during Mg ion insertion,which indicates that it has good insolubility and good structural stability in organic electrolytes.The results show that Mg-DIB has a reversible discharge capacity of 57.7 mAh g-1 at 2 C in the voltage range of 1-4 V,and the capacity retention rate is 95.7%after 500 cycles at 5 C current density,with good Rate performance and cycle stability provide a new idea for designing high-performance magnesium ion batteries and other energy storage devices.