| Lithium-ion batteries have been widely used in daily life as a kind of chemical energy storage.However,the low capacity of traditional graphite anodes and the long lithium-ion transport path severely limit the development of high-capacity lithium-ion batteries.At the same time,it is necessary to develop new anode materials to meet the market demand for high energy density.Layered materials such as graphite and transition metal dichalcogenides（Mo S2,WS2）have natural structural advantages as lithium ion anode materials.However,these layered materials also have some problems in practical application,such as the low capacity of graphite and the long Li+diffusion path;transition metal dichalcogenides（Mo S2,WS2）have high theoretical capacity but low conductivity and poor cycle stability.In order to solve these problems,we used assisted ball milling to effectively exfoliate the layered material into two-dimensional nanosheets and composite materials,and optimized the structure of the material to improve its electrochemical performance.The main contents of the paper are as follows:（1）The natural graphite is ball-milled for different times by means of ball-milling.Adding xylitol as an auxiliary during the ball-milling process can increase the transverse shear force and improve the ball-milling efficiency.The results showed that the performance of graphite was improved after assisted ball milling.The first reversible specific capacity of ball-milled 12 h-G was 382.26 m Ah/g at 165 m A/g current density.The rate is always above98.9%.High-quality graphene nanosheets（GNSs）were also exfoliated by this method.As the anode material,the capacity was 501.4 m Ah/g after 300 cycles at a current density of165 m A/g,with good cycling and rate performance.The electrochemical performance is improved because the specific surface area of graphite changes after assisted ball milling,and the diffusion path of lithium ions is shortened,and the generation of GNSs can effectively improve the capacity of graphite.（2）Although the capacity and stability of layered graphite-assisted ball milling have been improved in a small range,it still cannot meet the requirements of high capacity.Therefore,layered Mo S2 with higher capacity was selected,and Mo S2 nanosheets and Mo S2/GNSs nanocomposites with different ratios were prepared by assisted ball milling exfoliation.The results show that Mo S2 nanosheets and Mo S2/GNSs nanocomposites as lithium ion anode materials have improved the discharge capacity and cycle stability to varying degrees.Among them,when the original addition amount of Mo S2 and graphite is1:1,the electrochemical performance of the prepared Mo S2/GNSs composite nanosheets is the best.The initial discharge capacity was as high as 1014 m Ah/g at a current density of 50m A/g,and the capacity remained 664 m Ah/g without decay after 300 cycles at a current density of 250 m A/g.Few-layer Mo S2 nanosheets in composites can effectively increase the specific surface area of the material and shorten the diffusion path of Li+.In addition;GNSs can enhance the conductivity of Mo S2 nanosheets to stabilize the structure of the material.（3）Mo S2/GNSs composite nanosheets can be prepared by assisted ball milling,so WS2nanosheets and WS2/GNSs nanocomposites were prepared and synthesized for reference.The WS2@GNSs heterocomposite structure can be obtained by calcining the WS2/GNSs nanocomposites at 800°C without oxygen.Compared with the WS2/GNSs nanocomposite,its cycle and rate performance is more excellent.It can still maintain a high reversible specific capacity of 705 m Ah/g after 200 cycles at a current density of 250 m A/g,with a retention rate of 95%.The capacity remains in the original state after charge and discharge rate performance.The improved electrochemical performance of WS2@GNSs is attributed to the heterostructure formed after high-temperature calcination,in which the GNSs are embedded after WS2 nanoization.This can effectively alleviate the volume change caused by Li+intercalation and deintercalation,and enhance the structural stability of the material.In addition,heterostructured materials also have high electrical conductivity,which can accelerate the charge transfer during electrochemical reactions. |
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