Study On Lithium Storage And Sodium Storage Performance Of Picolinic Acid Electrode Material

The progress of new energy applications has led to the vigorous development of energy storage materials.Compared with traditional lead-acid batteries,nickelmetal hydride batteries,etc.,ion batteries are secondary batteries with many advantages such as high conversion efficiency,high energy density,environmental friendliness,long life and high reliability.Ion batteries have had relatively active basic research since the end of the last century.By the beginning of this century,ion batteries have been widely used in the fields of new energy vehicles,wind power generation and consumer electronics.Among them,the electrode material accounts for the largest proportion of cost in the entire ion battery device.Meanwhile the process to make it is the most complicated,and the performance of it is the most critical.Therefore,the research and preparation of electrode materials has always been a focus and difficulty of researchers.Studies have found that a considerable part of the functional groups of organic molecules have a high degree of electrochemical activity and can be used as active materials for ion battery electrode materials.At the same time,the abundance of organic matter,environmental protection characteristics and molecular design also contribute to the development of new high-performance organic ion battery electrode materials.In this paper,the electrochemical properties of a series of organic heterocyclic carboxylic acid molecules are explored through material characterization,performance testing,theoretical calculation ex-situ analysis,and performance improvement and principle analysis are carried out.The electrochemical properties of three organic heterocyclic carboxylic acid materials,2,5-pyridinedicarboxylic acid,2,5-thiophene dicarboxylic acid and imidazole-4,5-dicarboxylic acid,were explored.Among them,the initial charge capacity of 2,5-pyridinedicarboxylic acid is 480 mAh/g,which is higher than imidazole dicarboxylic acid and thiophene dicarboxylic acid,and has a continuous upward trend after short-term activation.At the same time,2,5-pyridinedicarboxylic acid also has the best rate performance among the three.Studies have found that the pyridine heterocycle in the 2,5-pyridinedicarboxylic acid molecule helps it undergo multiple enolization reactions,so it has better lithium storage performance than the other two molecules.Combining the advantages of high capacity of pyridine materials,low discharge platform of carboxylic acid-based materials and high cycle reversibility of planar stacking structure,a planar conjugated carboxylic acid 2,2'-bipyridine-5,5'-dicarboxylic acid was designed.Electrode material.The initial charge capacity of the lithium-ion battery is 361 mAh/g at a charge-discharge rate of 200 mA/g.After 50 cycles,it can be stably maintained for more than 200 cycles at a capacity of 550 mAh/g.Under the constant current charge and discharge of 200 mA/g,the sodium ion battery has a specific capacity of 256 mAh/g in the first cycle.After 10 cycles,its specific charging capacity reached 280 mAh/g,and the coulombic efficiency increased to over 99%.After 50 cycles,its specific charge capacity can still remain above 273 mAh/g.At the same time,the main reason for the capacity decline is the generation of dendrites and dead lithium in the lithium negative electrode,not the failure of the active material.Therefore,the 2,2'-bipyridine-5,5'-dicarboxylic acid electrode material has excellent lithium and sodium storage properties,and has good application prospects.In order to improve the initial coulombic efficiency of 2,2'-bipyridine-5,5'-dicarboxylic acid,2,2'-bipyridine-5,5'-dicarboxylic acid lithium salt,2,2 '-Bipyridine-5,5'-dicarboxylic acid sodium salt and 2,2'-dipyridine-5,5'-dicarboxylic acid calcium salt three materials,and compared their lithium storage and sodium storage performance.Among them,the lithium salt has the highest capacity for storing lithium,and the initial coulombic efficiency reaches 72%.Secondly,we deeply explored the lithium storage performance of lithium salt.At a current density of 200 mA/g,the test found that its initial charge capacity was 1600 mAh/g,and the initial coulombic efficiency was 73%.After 100 cycles,its specific charge capacity remained around 530 mAh/g.The sodium storage performance of lithium salt and sodium salt was also tested.Among them,sodium salt has a more stable sodium storage performance,with an initial charge capacity of 230 mAh/g and an initial coulombic efficiency of 77%.After 80 cycles,the reversible specific capacity of212 mAh/g can still be maintained.Therefore,the salt-forming design strategy can effectively improve the electrochemical performance,coulombic efficiency and cycle stability from the perspective of organic molecular design,which also provides new ideas for the development of organic electrode materials.