Preparation Of Tin-Based Anode Materials For Lithium Ion Batteries And Research On Li-Intercalation Characteristics

Because it can be made into wearable portable products with small volume,light weight and high energy density to provide energy for digital products and power vehicles,lithium ion has become the most widely used energy storage device.Electrode material is an important part of LIB,and its capacity is also a key factor in determining battery performance.In order to meet the demand of high energy consumption occasions such as new energy vehicles,aerospace and national defense for power batteries,it is particularly important to develop high capacity,environmental protection and cost-effective anode materials.Tin based materials have become an alternative anode material because of their low price,non toxicity and high theoretical specific capacity（Sn:994 m Ah/g,SnO₂:1494 m Ah/g）.However,when directly used as anode materials,both tin and tin oxide will lead to capacity depletion due to serious volume expansion,and the cycle stability is not well,it is impossible to realize long-term multiple charge and discharge.At present,many scholars aim to stabilize the structure of tin based materials,alleviate the volume expansion in the cycle,and design electrode materials with excellent electrochemical performance through the treatment of nano tin based materials,metal/non-metal ion doping and carbon coating.In this paper,based on a large number of current research on tin based materials,the composition,structure and electrochemical properties of Mo-doped 3D carbon@Sn,SnO₂@Li₄Ti₅O₁₂@C hybrid and Li F@SnO₂@C nanosheets were studied.Sodium alginate are used as chelating agent and carbon source,the Mo-doped 3D C@Sn composite has been fabricated by freeze-drying and annealing.XRD,Raman,SEM,XPS,charging and discharging test,CV and EIS are used to test the electrochemical performance.The results confirm that the Mo-doped 3D carbon@Sn composite exhibits high reversible capacity of 800m Ah/g at 0.2A/g after 200 cycles,superior rate capacity of 327m Ah/g even at 5.0A/g and long-term cycling stability of814m Ah/g at 1.0A/g after 500 cycles.The 3D carbon matrix effectively buffer the volume expansion during the cycle,shorten the transmission distance of Li⁺,and increase the rate capacity.The doping of Mo nanoparticles can not only prevent the agglomeration of Sn particles,but also provide more active sites for the embedding of Li⁺together with Sn nanoparticles.The SnO₂@Li₄Ti₅O₁₂@C material was prepared by hydrothermal,sintering,and ball milling methods.XRD,Raman,SEM,XPS,charging and discharging test,CV and EIS are used to test the electrochemical performance.The results confirm that the SnO₂@Li₄Ti₅O₁₂@C material still maintains a reversible specific capacity of957.6m Ah/g after 300 cycles at a current density of 0.2A/g,and the coulombic efficiency remains above 98%after the 10th cycle.The capacity remains at 756m Ah/g after 750cycles at a current density of 1.0A/g,which has excellent electrochemical performance.The nano-treated SnO₂and the"zero strain material"Li₄Ti₅O₁₂can alleviate the chemical pressure which produced in the cycle of charge and dicharge.Beside,can also prevent the accumulation of graphite nanosheets.On the basis of hydrothermal synthesis of SnO₂nanoparticles,Li F@SnO₂@C nanosheet materials were further synthesized by ball milling,which realized the prelithiation treatment of tin-based materials.The results of electrochemical measurement and analysis show that the Li F@SnO₂@C nanosheet material has an excellent capacity of 951.9m Ah/g after 370 cycles at a current density of 0.2A/g,and the ICE reaches 67.4%.It has a specific capacity of 650.0m Ah/g after 930 cycles at a current density of 1.0A/g.The Coulombic efficiency after the 15th cycle was 98.5%and remained above 98.5%in the subsequent cycles.Li F compensates the Li⁺consumed by the formation of the SEI during the initial cycle and inhibits the decomposition of the electrolyte.The strong electronegativity of F^-can adsorb more Li⁺,further increase the capacity of the material,and form stable F-Sn and F-C can also stabilize the structure of the material and inhibit the volume expansion of the composite material during charging and discharging.