Hard Carbon And Its Composites In Sodium Ion Battery Application Study

Owing to the characteristics of high abundance,easy mining and significant price advantage of sodium mineral resources,sodium ion batteries(SIBs)are gradually regarded as a powerful alternative to lithium ion batteries(LIBs)in the application scenarios of new energy vehicle power supply and urban energy storage.Compared with the cathode material of SIBs,the common anode material is difficult to have high capacity,high rate and high cycle stability.The poor performance of sodium storage of negative electrode material seriously hinders the wide commercial application of SIBs.Therefore,it is urgent to develop negative electrode materials with excellent sodium storage properties.In the category of metal ion battery anode materials,porous carbon materials have attracted much attention due to their characteristics of flexible pore structure regulation,high specific surface area and excellent electrical conductivity.Moreover,the development of high performance,low cost and readily available anode materials is of great significance for the industrialization of sodium ion batteries.In this context,this work is based on the concept of "simple and feasible industrialization",respectively using gel and Lycium barbarum as carbon sources to synthesize porous carbon anode materials for sodium ion batteries.The specific research content is as follows:(1)Using a gel generated from citric acid and ethylene diester as a carbon source and g-C3N4 as a nitrogen source,we designed a gel coating method to synthesize g-C3N4/amorphous carbon composite material.Electrochemical performance measurements showed that CCN half-cell can provide high discharge capacity of 250 mAh g-1 at 0.1Ag-1 and 183 mAh g-1 at 3 A g-1.Besides,CCN half-cell exhibited long charge-discharge cyclic stability with maintained capacity of 180 mAh g-1 after more than 1600 cycles at current density of 0.5 A g-1.Moreover,the full battery of CCN//Na3V2(PO4)3 assembled with Na3V2(PO4)3 as positive electrode material presented a high discharge capacity of 136 mAh g-1 at 0.1 A g-1 for 140 cycles.(2)In order to investigate the feasibility of wolfberry biomass hard carbon material in sodium ion battery anode material,Lycium barbarum was used as the carbon source to preparation of hard carbon anode materials using a one-step thermal decomposition method.The effect of pyrolysis temperature on the energy storage performance of porous carbon materials was investigated.The electrochemical data demonstrated that the porous carbon anode material obtained from 1000℃ carbonization has the best performance of sodium storage.At current density of 25 mA g-1,it presented the first-cycle chargedischarge capacity of 230 mAh g-1,and the first coulomb efficiency as high as 98%.This coulomb efficiency maintained at 95%over 200 cycles.