Study On Prelithiation Of SiO Negative Electrode For Lithium Ion Battery

Silicon oxide（SiO）materials have a high reversible specific capacity(1400 m Ah g^-1)and are considered to be one of the most promising anode materials for future high energy density lithium-ion batteries.However,SiO itself generates a large number of irreversible products（lithium silicates and Li₂O）during the first lithium embedding process,resulting in a low first Coulomb efficiency（ICE）,which affects its practical application.The irreversible capacity during the first lithium embedding can be compensated by pre-lithiation.This paper addresses the pre-lithiation products of SiO electrode sheets and the performance differences before and after pre-lithiation.The main research work is as follows:（1）A chemical pre-lithiation strategy was chosen to prepare a lithium aromatic complex pre-lithiation solution（lithium-biphenyl/2-methyl-tetrahydrofuran solution,referred to as B-LAC solution）with a lower redox potential than SiO.90%ICE was achieved at the SCG electrode after 10 min immersion in 0.2 mol/L B-LAC solution.The chemical pre-lithiation was shown to preform SEI films by CV,EIS,and the potential distribution of the pre-lithiated electrodes was found to be more uniform after cycling by AFM tests.Due to the preformation of Li F-rich SEI film,the pre-lithiated cell has better multiplication and cycling performance,and the capacity retention of the pre-lithiated electrode increases from 77.5%to 88.5%after 250 cycles.70.4%to 85.3%respectively,and the capacity retention rate increased from the original 89.7%to 93.7%.（2）The ICE of the SiO electrode was improved by short-circuiting the pre-lithiation,and the ICE of the SCG electrode reached over 90%after 60 minutes of contact with lithium metal in a 4 mol/L Py₁₄FSI electrolyte.The short-circuit pre-lithiation was also found to form a SEI film on the electrode surface by EDS and XPS.The lithiated Pre-SCG has a smaller polarisation and a higher lithium-embedded plateau potential,which is more conducive to lithium de-embedding.The lithiated cell has excellent multiplicative and cycling performance,with the Pre-SCG electrode also maintaining a high reversible specific capacity and capacity retention of 842.5 m Ah g^-1/77.8%,respectively,after 300cycles.（3）A modification study was carried out to address the relatively poor multiplicative performance and low conductivity of ionic liquid electrolytes.By using carbonate electrolyte to preform a thin and stable SEI layer on the SiO electrode sheet,the pre-lithiated electrode is subsequently charged and discharged in the ionic liquid electrolyte to achieve an improvement in electrode multiplicity performance.It was found that the carbonate electrolyte had a higher ion mobility and faster pre-lithiation rate for the same lithium salt concentration,with the ICE reaching over 90%at 20 min of pre-lithiation of the SCG electrode in the carbonate electrolyte（Pre-SCG-CE）.It took 40 min of pre-lithiation in an ionic liquid electrolyte（Pre-SCG-IL）to achieve an ICE of over 90%.The GITT test showed that the D_Liof Pre-SCG-CE was greater,so the carbonate electrolyte obtained better cycling and multiplier performance after pre-lithiation of the silicon-carbon cathode.The specific capacity and capacity retention of the Pre-SCG-CE electrode were 552.5 m Ah g^-1/63.7%after 450 cycles of 1C,respectively.A multiplier test showed that when reverting from a large to a small multiplier,the Pre-SCG-CE had an even higher capacity retention of 93.5%.