| Silicon has the advantages of low lithium intercalation potential,high theoretical specific capacity,and abundant reserves,and has become one of the most promising anode materials for new-generation lithium-ion batteries.The efficient recycling of photovoltaic silicon waste is one of the important ways to achieve"carbon neutrality".At present,the recycling process of silicon waste is cumbersome,the secondary pollution is serious,and it can only achieve graded recycling,while the silicon waste has the advantages of high purity and small particle size.It has potential value for application in lithium-ion batteries.The purpose of this paper is to realize the secondary utilization of photovoltaic silicon waste.After simple pretreatment,it is applied to the negative electrode of lithium ion battery,and the electrochemical performance of silicon-based negative electrode material is regulated from the perspective of binder and silicon composite material.The main work is as follows:（1）The pretreated photovoltaic silicon waste is used as the active material of the electrode material,and the performance of the electrode material is regulated from the perspective of the binder.The negative electrode of lithium ion battery was prepared by binder,and it was found that the use of CMC and SA binder has high initial capacity(5582 m Ah g-1,5135 m Ah g-1)and excellent cycle stability,and it can be cycled for 300 at high current density.It still has a capacity of 701 m Ah g-1 and 618 m Ah g-1 after the lap,which is attributed to the fact that the CMC and SA binder segments contain a large number of carboxyl groups and hydroxyl groups.On the one hand,the structural stability of the electrode material is stabilized and the volume expansion is relieved.On the other hand,it provides a fast transport channel for the transport of ion electrons.Compared with pure Si anode,the battery capacity and cycle stability performance of the battery prepared from silicon waste are better,which is due to the participation of boron element in the silicon waste in the lithium storage process.The change process of the electrode material was observed by in-situ optical microscope;the in-situ XRD results showed that the phase structure of the electrode changed before and after charging and discharging.The newly generated peak positions at 2θ=45°and the peak positions at 2θ=39°and 65°The change is the main reason for the rapid capacity decay of silicon anode materials.（2）Silicon quantum dots were prepared by high-energy ultrasonication.The TEM results showed that the size of silicon quantum dots was 3.7±0.5 nm.The silicon dots were further compounded with graphene oxide,and Si@r GO composites were obtained by one-step calcination.The XPS analysis showed that the silicon dots were dispersed on the surface and between the layers of graphene,and some of the silicon dots electrostatically self-assembled into nano-silicon dots spheres covered by graphene.In terms of electrochemical performance,the composite structure exhibits excellent lithium storage performance and cycling stability.The results show that the composite anode has an ultra-high capacity of 5406 m Ah g-1 at a current density of 0.05 A g-1It still has a capacity of 1784 m Ah g-1after cycling to 288 cycles at the same current density,and has excellent long-term cycling stability.After 8 current density changes from 0.05 A g-1 to 10 A g-1,it still has a capacity of 408 m Ah g-1,and has excellent rate performance.The excellent electrochemical performance is due to the covalent bonds formed by the anchoring of silicon quantum dots on graphene defects and substituted functional groups.The intercalated graphene and the coating structure of graphene greatly alleviate the volume expansion of the silicon material and show excellent cycle stability;... |
PDF Full Text Request