| With the rapid development of grid-scale,consumer electronics and electric vehicles,there are higher requirements for the energy density and cost of lithium-ion batteries.Silicon-based materials have the highest theoretical specific capacity among anode materials to the best of our knowledge,far surpassing commercial graphite anode,and abundant reserves.It can be potentially industrialized in large-scale.However,there are still many problems to be addressed.Different from the stability of graphite anode,silicon material will have a huge volume change during lithium insertion,which makes the interface failure of each component in the electrode,leading to the destruction of electrode structure.To solve this problem,in this paper,the recycled low-cost photovoltaic waste silicon is used as raw material,the electrochemical performance of the silicon anode was improved by the preparation of silicon-based composites and binder modification.The main contents of research are as follows:（1）The photovoltaic waste silicon powder purified by acid pickling as bare Si raw material,The PP-Schiff-base polymer coating is in-situ generated on the surface of silicon with p-phthalaldehyde and p-phenylenediamine as reactant monomers and acetic acid as catalyst.The surface coating can effectively mitigate the volume change of silicon,avoid the irreversible capacity loss caused by SEI layer is constantly destroyed and regenerated,and promote electronic transport.Under the current density of 420 mA/g,the first discharge and charge capacity are 3006 mAh g-1 and 2130 mAh g-1,respectively.The initial coulombic efficiency（ICE）reaches 70.9%.the capacity remains 1544 mAh g-1 after 100 cycles.When the rate performance was tested,the current density of 4000mA/g still had a capacity of 1033mAh g-1.In contrast to the bare silicon material rapidly lost its activity due to the severe volume expansion.It can be seen that the PP-Schiff-base polymer coating on the recovered silicon surface greatly improves the electrochemical performance of silicon materials.（2）In order to simplify the process conditions and further improve the electrochemical performance of the silicon anode material,p-phthalaldehyde and 3,3’-diaminobenzidine were used as the reactant monomer,and acetic acid was added as the catalyst to improve the reaction yield.The PD-Schiff-base modified silicon complex solution was prepared without purification and separated,and the conductive agent and binder could be added to prepare the silicon anode.PD-Schiff-base,which has stable reversible lithium insertion capacity,is used as coating on silicon surface,not only plays a role in inhibiting the volume expansion,can stabilizes the entire electrode structure,reducing the direct contact between the active material and the electrolyte,but also facilitates the diffusion and transmission of Li+.The electrode has well cycle performance,the capacity remains 1589 mAh g-1 after 200 cycles under a current density of 420 mA/g,at a high current density of 1000 mA g-1,the reversible capacity still maintains 975 mAh g-1 after 500 cycles.（3）The water-soluble carmine（Cm）and sodium carboxymethyl cellulose（CMC）were mixed and connected by hydrogen bond to form a more stable network structure binder CMC-Cm,and the resulting composite binder CMC-Cm shows stronger adhesion in silicon anode,which could not only better release internal stress,but also stabilize the solid electrolyte interface（SEI）,reduce the decomposition of electrolyte,and effectively improve the electrochemical performance of silicon anode.The initial capacity of the Si@CMC-Cm electrode was up to 2734 mAh g-1 and the initial coulomb efficiency was 76.8%,it still has a stable capacity of 1566 mAh g-1 after 100 cycles. |
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