Study On Dehydroascorbic Acid And CoNi-MOF As Anode Materials For Lithium Ion Batteries

In recent years,with the development of the economy,the global consumption of oil and fossil fuels has increased year by year,and the ensuing environmental problems have caused concern.The search for alternative energy sources and development and a green and environmentally-friendly economic approach is imminent.Chemical power sources have attracted the interest of scientists and enterprises in the energy field due to their own advantages.For example,the advantages of high voltage,high specific energy,long cycle life,and low cost have become research hotspots.The development of higher-performance lithium-ion batteries has become the main task.Lithium-ion batteries are composed of cathode active materials,anode active materials,separators,organic electrolyte and battery case,The anode electrode active material has always been graphite,but its theoretical specific capacity is 372 m Ah / g,which is difficult to meet the needs of power batteries.The preparation of new lithium-ion battery anode materials has become the key to solving the battery capacity.In this thesis,a metal organic framework material(MOF)was synthesized as the anode active material of lithium-ion batteries to investigate its electrochemical performance.The details are as follows:First of all,organic materials have the advantages of high capacity,low cost and environmental friendliness as battery anode materials,and have become one of the alternatives to anode materials for inorganic metal compounds.Carbonyl compounds have reversible storage of lithium ions due to the C = O double bond.Therefore,the nature of multiple carbonyl functional groups determines that the material has the advantages of structural diversity and fast reaction kinetics.We prepared a negative electrode material for lithium ion batteries by mixing dehydroascorbic acid with graphite,and conducted electrochemical tests to find that the current density is 100 m A / g,the first cycle discharge capacity is 600 m Ah / g,and the voltage platform is 0.8V.This is a common feature of carbonyl compounds platform.In the subsequent infrared test,it was found that the characteristic peak did not change significantly,indicating that the material has structural stability.After repeated charging and discharging of the battery,the capacity was found to decline.The analysis showed that this was mainly due to the easy dissolution of organic compounds in organic electrolyte Measures mainly add conductive carbon additives in improve cycle stability and conductivity.Secondly,we synthesized the MOF using the hydrothermal method,and obtained the MOF composite material by centrifugation and multiple washings.Due to the crystalline porous nature of the periodic network structure of the MOF,the electrolyte fully wets theactive material in the electrode.After activation,the stability of the electrode structure is improved.so it has the advantages of high capacity and long cycle life in the electrochemical performance test.For example,at a current density of 500 m A/g,Ni Co-MOFs still has a capacity of 1120 m Ah / g after 200 cycles.However,the electrochemical performance of Ni-MOF and Co-MOF single-metal organic framework materials is not as good as that of bi-metal MOF materials.This interesting phenomenon is worth further exploring the underlying mechanism.