The Effect Of Additives In Aether Electrolyte On The Performance Of Lithium Metal Anode

Lithium metal shows a theoretical specific capacity of 3860 m Ah/g,which is ten times more than that of graphite.The rechargeable Li metal batteries have been called the “Holy Grail” of the energy store systems and posses important research values and broad application prospects.During the last 40 years,however,dendrite and coulombic efficiency have hindered the real application of Li metal electrode.In this thesis,Li dendrite and coulombic efficiency in the lithium metal secondary battery were studied.The main salt Li TFSI and solvent DOL / DME were widely used in lithium ion batteries.It is expected to improve SEI film quality,the efficiency of the coulombic cycle,thereby the electrode cycle stability,by adding traces of water and organic additives VC,FEC and Li PF6 inorganic lithium salt.First,a simple and feasible electrodeposition technique was used to simulate the behavior of the lithium metal electrode during the charging process.The constant current electrodeposition was carried out by using copper as collecto r in a three-electrode system.The influence of electrolyte on lithium negative electrode was evaluated from the cyclic voltammetry curve,the deposition curve,surface morphology(SEM),and impedance spectroscopy.SEM results show that the addition of trace water to the system to achieve the the dendrite-free Li layer.The selected electrolyte system is packaged with a Li / Cu coin cell and analyzed by constant current charge and discharge test.It was divided into short-term and long-term stability test.The short-term test was conducted to obtain the coulombic efficiency of different electrolyte systems.In the process of charging and discharging cycle,the coulombic efficiency and its decay of the electrolyte system were analyzed in order to evaluate the battery stability characteristics.The impedance test of different electrode solutions was carried out in different cycle nodes.The impedance changes of different cycles were compared with those of long-term stability.The effects of different system electrolytes on the suppression of Li dendrite formation and improvement of coulombic efficiency were studied.In the selected electrolyte system under the packaging of lithium iron phosphate and lithium as positive and negative electrode button batteries,t he same constant current charge and discharge testing,but set the charge and discharge cut-off voltage,the upper and lower limits of 3.9 V and 2.8 V,and do long-term charge and discharge cycle.The effect of different electrolyte systems on electrode polarization was analyzed by the relationship between discharge capacity and voltage.Different systems of battery discharge specific capacity and coulombic efficiency changes was analyzed through the long-term cycle.