Preparation And Electrochemical Properties Of Titanium Dioxide/Miscellaneous Elements Doped Carbon Composites

With the development of new energy sources,lithium-ion batteries and sodium-ion batteries have received extensive attention as energy storage devices.Titanium dioxide anode materials have been widely studied because of their stable structure,good lithium\sodium storage and rich content.However,there are also problems with low ion and electronic conductivity and low theoretical specific capacity.Heteroelement-doped carbon materials not only increase the electrical conductivity of the material,but also cause external defects due to doping of heteroelements,enhancing the transport dynamics of ions and electrons.Therefore,in this paper,the carbonized material containing conductive polymers containing heteroelements is a heteroelement-doped carbon source,which is composited with TiO₂ to obtain a TiO₂\heteroelement-doped carbon composite material,exhibiting excellent electrochemical performance.The main content of this paper was:?1?Using polypyrrole?PPy?as the source of nitrogen-doped carbon,polypyrrole was evenly coated on the surface of a titanium alcohol?TG?precursor by in-situ polymerization,and nitrogen-doped carbon coated TiO₂ was obtained after calcination at high temperature.In the NTiO₂@NC composite material,N element is not only doped in the carbon shell,but also the presence of N element can be found in TiO₂.The NTiO₂@NC composite exhibited excellent lithium-ion battery electrical properties,and the capacity after repeated 2000 cycles at a high current density of2000 mA g^-1 and 5000 mA g^-1 was 343.4 mAh g^-1(2000 mA g^-1)and 232.7 mAh g^-1(5000 mA g^-1),which is better than pure TiO₂(87.5 mAh g^-1 capacity at 5000 mA g^-1).?2?Polythiophene?PTh?is the source of sulfur-doped carbon.Sulfur Co-doped TiO₂@Carbon?STiO₂@SC?composites were obtained through simple in-situ polymerization and high-temperature calcination.The composites were applied to lithium/sodium batteries,respectively,exhibiting excellent electrical properties.When STiO₂@SC composites were used as anode materials for lithium-ion batteries,the reversible capacity was maintained at 215.3 mAh g^-1 after the composites were cycled2000 times at a current density of 5000 mA g^-1,which has excellent long-cycle stability.When STiO₂@SC composites were used as anode materials for sodium ion batteries,the reversible capacity was still as high as 121.2 mAh g^-1 and the coulombic efficiency was¹00%when the current density was 1 A g^-1.?3?The polyindole?PIn?is the source of nitrogen-doped carbon.After carbonization,NTiO₂@NC?PIn?composites are obtained.When used in a sodium-ion battery,it exhibited excellent electrochemical performance.At a current density of200 mA g^-1,the NTiO₂@NC?PIn?composite material has a capacity of about 220mAh g^-1 and a Coulomb efficiency of more than 98%.This shows that nitrogen doped carbon coated TiO₂ not only improves the electrical properties of lithium batteries,but also improves the electrical performance of sodium-ion batteries.?4?Silver?Ag?particles are used to increase the electrical conductivity of the material.By reducing silver ions,the Ag particles are evenly coated on the surface of the TG precursor.After calcination,a TiO₂@Ag composite material is obtained.The composite material was used as a sodium ion anode material,and at a high current density of 1000 mA g^-1,after an activation process,the reversible capacity remained at 121 mAh g^-1 after 1800 cycles,and the pure reversible capacity was only 62.5 mAh g^-1.It can be concluded that TiO₂@Ag composites can improve the sodium ion electrical properties.