Studies On Sodium Storage In Biomass Hard Carbon

Sodium ion battery is an ideal choice for large-scale energy storage system due to its rich sodium reserves,low cost and acceptable electrochemical performance.Anode materials with high performance is one of the decisive factors for the commercial ap-plication of sodium ion battery.Among all the anode materials,hard carbon is the most promising sodium storage anode material because of its rich resources,low cost and high sodium storage capacity.However,the development of hard carbon materials which are cheap and suitable for sodium ion battery is still an important direction for the practical application of hard carbon anode materials.In this paper,hard carbon ma-terials with high performance were prepared by using cheap biomass as precursor and optimizing pyrolysis conditions.On the basis of the study of the sodium storage prop-erties,the sodium storage mechanism of hard carbon-based anode was explored.The main contents and results of this paper are as follows:（1）The electrochemcial performance of biomass-derived hard carbon anode ma-terials for sodium ion battery.Due to the abundant biomass reserves and low price,we have prepared a series of hard carbon materials by regulating pyrolysis process with camellia seed shell as the precursor.It was found that when the pyrolysis temperature was 1300℃,the hard carbon electrode showed the best electrochemical performance.For example,TS1300 hard carbon material can provide high sodium storage capacity(299.1 m A h g^-1 under the current density of 20 m A g^-1)and stable cycling performance（capacity retention:93.8%after 1000 cycles）.This hard carbon anode material has a potential application prospect in the construction of low-cost sodium ion batteries with a large reversible capacity and ultra-stable cycling performance.Compared the electro-chemical characteristics of the carbon of camellia seed shell pyrolysised at different pyrolysis temperatures,we found that the experimental results conform to the"adsorp-tion-intercalation"mechanism:the high-potential slope corresponds to the adsorption behavior of Na⁺on the hard carbon surface,while the low-voltage platform corresponds to the intercalation behavior of Na⁺between the layers of hard carbon.（2）Studies of biomass-derived hard carbon anode materials with high productivity.In order to improve the productivity of hard carbon,charcoal with low ash content and high density was selected as the precursor to pyrolyze hard carbon material.This kind of hard carbon electrode（JW1300）exhibited a good reversible capacity(294.4 m A h g^-1)and initial Coulomb efficiency（77.6%）.The sodium storage mechanism was con-sistent with the"adsorption-intercalation"mechanism.This work provided a new idea to prepare hard carbon with low cost and low energy consumption,givn a novel direc-tion for the sodium storage anode materials.（3）The wood-derived hard carbon anode material modified with dopamine.In or-der to further improve the sodium storage performance of the hard carbon prepared by jujube charcoal,a series of pyrolysis hard carbon materials were designed and synthe-sized by jujube charcoal with the modification of dopamine.The results showed that JW@2.5%P1300 can provided a higher initial capacity(345.9 m Ah g^-1)and excel-lent coulomb efficiency（78.9%）.The capacity was also up to 291.3 m Ah g^-1,and the capacity retention rate was as high as 95.4%even after 250 cycles.Thus,the hard car-bon with good electrochemical performances can be effectively improved by simple modification of dopamine oxidation.This provides an idea for the preparation of high-performance hard carbon materials,and this kind of carbon is expected to realize the application of hard carbon anode in large-scale stored sodium ion batteries.