Investigation On Preparation And Performance Of Tin-based Anode Materials For Lithium-ion Batteries

The theoretical capacity of tin anode materials is up to 990 mAh·g^-1,and the element tin is extremely abundant in storage,low in price,and environmentally friendly.It is one of the anode materials with very commercial prospects.However,the severe volume expansion of the metal tin during charging and discharging causes the electrode active material to crack and fall off.This results in a decrease in battery capacity and cycle stability.In response to this problem,this topic has made relevant research and obtained the following results:?1?The tin anode film material was prepared by direct current electrodeposition method by controlling respectively current density and electrodeposition time.Firstly,four sets of pure tin anode materials were prepared at different current densities.Their composition and structure were analyzed by X-ray diffraction and scanning electron microscopy,and the electrochemical properties were analyzed by constant current charge-discharge curves to determine the optimum current density.Then,at the optimum current density,four sets of pure tin anode materials were prepared by controlling electrodeposition time,and their composition and structure of the composition were analyzed by X-ray diffraction analysis and scanning electron microscopy,and the electrochemical properties of the tin electrode were studied by constant current charge-discharge method,cyclic voltammetry and AC impedance method.Finally,the best current density and electrodeposition time were screened out.The experiment results showed that the prepared pure tin electrode when the current density is 40mA/cm² and the time is 20 minutes has a regular rhombic structure,and the film grains are tightly bonded together,resulting in good density and the grain size is about 1-2?m,and the uniformity is good.And showed good electrochemical performance,the first discharge capacity was 765.6 mAh·g^-1,the charge capacity was 322.5 mAh·g^-1(at a rate of 100 mA·g^-1),the first irreversible capacity was 443.1 mAh·g^-1,and the Coulomb efficiency was 42.1%.The capacity of the electrode in the first 41 cycles remained relatively stable,and the capacity of the electrode remained at 345.6 mAh·g^-1 at 41 cycles.?2?Four sets of Sn-Fe alloy film electrodes with different compositions were prepared by electrodeposition in different solutions.The effects of the relative content of inert element Fe in the alloy electrode on the electrochemical performance of Sn-Fe alloy electrodes were investigated.The results show that with the increase of the relative content of Fe in the alloy electrode,the first coulombic efficiency of the alloy electrode increases gradually,the cycle stability and the conductivity of the electrode were improved.It has exellent electrochemical performance when the relative content of Fe in the alloy electrode is 21.41%,When the current density is 100 mAh·g-1,the first discharge capacity is 475.6 mAh·g^-1,and the capacity is 322.1 mAh·g^-1(at a rate of 100 mAh·g^-1),the first irreversible capacity was 153.5mAh·g^-1,the coulombic efficiency was 67.7%,and the discharge capacity remained 173.2mAh·g^-1 after 100 cycles.The stability of the electrode is greatly improved due to the addition of intert element.This is because the addition of the inert element Fe makes the active material have good dispersibility.At the same time,the volume expansion of the active material is suppressed,and the powdering and detachment of the active material is reduced,so that the electrode material forms a pore structure in the reaction.Under the synergy of the inert component and the pore structure,the volume expansion caused by the reaction of the active substance,to a large extent,was suppressed,so that the structure of most of the electrode materials is still good and connected to each other to form a three-dimensional skeleton,and the electrode cycle performance is greatly improved.