Improvement Strategies Toward Initial Coulombic Efficiency Of Silicon Monoxide Anode Materials For Lithium Ion Batteries

As the next generation anode materials replacing graphite,Silicon monoxide has a high theoretic capacity of 1500 mAh/g.Compared with pure silicon,it's expansion rate is lower?¹18%vs 300%?.However,during the first lithium insertion cycle,a lot of irreversible products and solid electrolyte interphase?SEI?are formed,leading to a low initial Coulombic efficiency?ICE?.Therefore,studies of improving ICE of silicon monoxide were performed,including the modification of internal components and adding active lithium contained materials.The main study contents are below:?1?Improve ICE of silicon monoxide by transforming SiO₂ to lithium silicates.A sintering process of lithium carbonate with silicon monoxide was adopted to transform SiO₂ to lithium silicates.As a result,obtained lithium silicates with high crystallinity hampered the flow of Li⁺and electrons,making Si inside inactive.After being milled,the lithium silicates became amorphous and the ICE of the elecrode increased to 72.6%from 58.4%.The irreversible capacity decreased to 335.2 mAh/g from 832 mAh/g,and the cycling performance also improved.?2?Improve ICE of silicon monoxide by adding AlLi alloy powder.Taking Al foil as the ingredient,AlLi alloy powder was synthesized through the expansion power of lithium insertion into Al foil in organic solution containing active Li.A new match of binder and solvent for pre-lithiation reagents was put forward,PVDF-HFP and THF,having no side effects for the performance of AlLi alloy powder.After being applied onto the silicon moxoide electrode,charging and discharging test was performed.As a result,the deintercalation capacity of the electrode was increased,producing a high ICE of 88.2%.According to the cycling results,the addition of AlLi alloy powder doesn't affect the cycling stability of cells.