Preparation And Lithium Storage Performance Of Lithium Titanium Silicate Anode Materials

Lithium ion battery（LIB）has the characteristics of high specific energy,long service life,low self-discharge rate,and green environment protection.It is one of the battery systems with the best comprehensive performance at present.It is rapidly developing into a new generation of energy storage power supply,used in information technology,electric vehicles,aerospace,aviation,and other fields of power security.Anode materials play an important role in lithium ion batteries.Among many anode materials for lithium ion batteries,titanium-based materials have been widely studied due to their advantages of low cost and environmental friendliness.However,the poor ionic and electronic conductivity of titanium-based materials hinders its development and production in the field of lithium ion batteries.This paper aims to improve the cycling performance and multiplier performance of titanium-based cathode materials by means of carbon composite and heteroatom doping.The main research contents are as follows:（1）Li₂TiSiO₅（LTSO）has a theoretical specific capacity of up to 315 mAhg^-1with a suitable working potential（0.28 V vs.Li/Li⁺）.The electronic structures of Li₂TiSiO₅ are firstly investigated by theoretically calculation based on first-principle approach,and the results demonstrate that Li₂TiSiO₅ act as the insulator for transferring electrons.Thus,the framework with outstanding conductivity is very essential for Li₂TiSiO₅ to enhance the charge/discharge kinetics.The nitrogen-doped Li₂TiSiO₅/C nanofibers（LTSO-NDC NFs）have been obtained by using carbamide as nitrogen source through an electrospinning technique.The nitrogen-doped carbon matrix with high electronic conductivity improves the electrochemical properties of LTSO significantly.The LTSO-NDC nanofiber electrode delivers high discharge capacities,which are 371.7(0.1 A g^-1)and 361.1(0.2 A g^-1)mAhg^-1,respectively.It also shows comparable cycle performance,which could endure long cycle over 800cycles almost without decay at 0.5 A g^-1.The diffusion coefficient of lithium ions(D⁺_Li)also has been greatly improved.（2）Li₂TiSiO₅（LTSO）,as a new lithium ion anode material,has the characteristics of high theoretical specific capacity and low working voltage,which makes up the disadvantage of the existing anode materials.Na doped LTSO-C NFs(L_2-xN_xTSO-C NFs)are obtained by one-step electrospinning with sodium propionate as the sodium source.Na substituted for Li is not the more Na doping,the better.The L_2-xN_xTSO particles wrapped in carbon fibers not only have better cycling performance,but also improve the ions/electrons conductivity to some extent.Excessive Na would distort the original structure of LTSO.The results show that the L_1.75N_0.25TSO-C NFs electrode has the best electrochemical performance.The L_1.75N_0.25TSO-C NFs electrode has very high discharge specific capacities,which can reach 333.8 and 329.6 mAhg^-1 at 0.5 and 1 A g^-1,respectively.At the same time,it has outstanding cycling performance.The specific capacities of L_1.75N_0.25TSO-C NFs anoode after 1000 and 1500 cycles under 1 and 5 A g^-1 are not shown obvious attenuation.