Study On Preparation Of N/S Co-doped Carbon And Sodium Storage Performance

Lithium ion batteries has become the most important way of electrochemical energy storage due to its large energy density,small volume,no memory effect.But with the advent and development of smart grid era,the limited lithium resources,expensive and other issues will lead to the emergence of new energy crisis.While,the abound sodium resources and low price making the sodium ion batteries become a promising candidate,which possess similar working principle of lithium ion battery.Although the development of lithium ion battery is mature,but lithium ion battery electrode materials can not be directly applied in sodium ion battery because of the sodium ion radius is larger than the radius of lithium ion.Hence it is necessary to develop electrode materials with low price,excellent performance and suitable for sodium ion battery system to improve the battries performance.Among the multitudinous sodium ion battery anode materials,carbon materials have attracted much attention due to their abundance,low price and environment friendly.The hard carbon became more commonly anode materials because of the high capacity and long life cycle.In order to further improve the sodium storage properties of hard carbon,the novel structures are usually constructed or surface modification by heteroatom doping.Different hereoatoms(O,N,B,P,S,etc.)are introduced into the carbon skeleton,which can change the charge distribution and spin density,generate the defects to improve the storage performance.Carbon materials commonly used as sodium ion batteris anode materials and can be achieved by surface modification(heteroatoms doped)to further improve the electrochemical performance of materials.This article mainly centered on the N/S co-doped carbon material,which were prepared by adding different heteroatom sources and carbon sources.The related characterization of doped materials were performed and explored their performance as anode materials for sodium ion batteries.1.First-principles calculations within dispersion-corrected density functional theory demonstrated that N,S co-doping can increase the spin density,electronegativity,the adsorption capacity of Na atoms and Na+ diffusion ability.However,the excessive O atoms have the opposite effect.Co-doped carbon materials with the excellect,electrochemical performance were obtained by controlling the amount of carbon source and heteroatoms source.When the quality ratio of gelatin and thiourea was 1:10,the optimized product exhibited a super cycling capacity of 300 mAh g-1 at 0.2 A g-1 after 500 cycles,with a Coulombic Efficiency of ~100 %.2.Pyrrole was used as raw materials,polypyrrole precursor containing nitrogen was prepared via chemical oxidation polymerization,and ammonium persulfate as oxidant and sulfur source,through the activation of KOH,the net-like structure N/S co-doped micropore carbon was prepared after carbonization and exploted its storage properties used as sodium ion batteries anode material.After doping and activation,it has a net-like and micropore structure,specific surface increased significantly.The electrical performance showed that the discharge capacity reached 301 and 153 mAh g-1 at the current density of 0.2 and 10 A g-1,revealing the super cycle stability,long life cycle and superior rate capability.3.Polyaniline(PANI)and polypyrrole(PPy)nitrogen containing organic precursor were prepared through in-situ chemical oxidative polymerization,and ammonium persulfate was used as oxidant and sulfur source,N/S co-doped microporous carbon materials were obtained after chemical activation.As sodium ion battery anode materials,the electrochemical performance test results showed the composite material has excellect cycle stability with a high discharge specific capacity(discharge specific capacity is 300 mAh g-1 at the current density of 0.2 A g-1)and capacity remain of 98% after 1000 times cycles.