Basic Research On Preparation Of Silicon Nanomaterials By Using Beads-milling

Silicon nanomaterials,with abundant reserves and stable process of lithiation/delithiation,are ideal anode materials for lithium-ion power batteries.Beads-milling is currently the mainstream method for nanocrystallization of silicon,However,in the preparation process,there are many factors affecting the grinding effect.The movement of particles during grinding is complicated,so it is difficult to achieve the desired grinding effect.As to the key issue of controlled preparation of silicon nanoparticles,in this paper,the effects of spindle speed and ball diameter on the grinding effect were studied from the perspective of process parameters.First,the test equipment was measured,and the beads-milling was modeled by Solid Works.Then based on the discrete element method,the motion state of beads was simulated by EDEM,explore the speed distribution and movement law of grinding balls under different spindle speeds;data such as the number of collisions,the mean collision energy,and the total collision energy were extracted to explore their variation rules at different spindle speeds.The process of beads-milling was theoretically analyzed from the point of view of energy loss method.the relationship amongst different size of grinding balls,spindle speeds and the energy consumption was studied by using the proper energy model.Relevant tests were designed to explore the effects of different spindle speeds and ball diameters on particle size,validating the laws derived from simulation and numerical calculations.The particle size of silicon nanoparticles was measured by LPSA,the variation law of particle size(D50,D90)under different spindle speed and grinding ball diameter was obtained.By SEM,XRD and other testing methods,the morphology of the silicon nanoparticles prepared by the tests was characterized.It is demonstrated that,increase of rotating speed is conducive to improving the grinding effect;in a certain range of particle size,the grinding ball with small diameter has higher energy utilization and better grinding effect.To verify the weaken effects of the reduction of silicon nanoparticle size on the significant volume effect associated with lithiation/delithiation processes,this paper conducted related electrochemical performance tests on silicon nanoparticles,and the results are as follows: The first time charge specific capacity of the large-sized silicon particles is extremely high,which is more than 3000 m Ah/g.However,after 150 cycles,reversible capacity of the silicon-based anode maintains at about 292.1m Ah/g,which corresponds to ?10% capacity retention.As a contrast,the first time charge specific capacity of the small-sized silicon particles is 1846.5m Ah/g.And after 150 cycles,reversible capacity of the siliconbased anode maintains at about 706.9m Ah/g,which corresponds to ?40% capacity retention.