热处理对锂离子电池硅/石墨/炭负极电化学性能的影响

将天然石墨、酚醛树脂和微米级硅粉进行球磨处理制备复合材料前驱物,再于N2气氛下700℃炭化得到硅/石墨/炭(Si/G/C)复合电极材料,采用X射线衍射仪、扫描电镜和透射电镜及电化学循环充放电对其形貌、结构及其电化学性能进行表征.结果表明,Si/G/C作为锂离子电池负极材料具有高于900 mA·h/g的可逆比容量,40次循环后保持在550 mA·h/g.对电极进行热处理后,其循环性能显著提高,40次循环后比容量保持在700 mA· h/g.扫描电镜分析结果显示,热处理后集流体上电极材料分布更均匀,因涂抹不均形成的空隙不复存在.热处理后电极结构更致密、内部黏结强度增大使其结构稳定性明显提升,是电极循环性能提高的主要原因.

Effect of heat treatment on the electrochemical properties of Si/G/C anode for lithium-ion batteries

Si/G/C composites were prepared from a mixture of artificial graphite,phenolic resin and micro-silicon powder by a ballmilling process to form a composite precursor and carbonization at 700 ℃ under N2atmosphere.The morphology,structure and electrochemical properties of the Si/G/C composites were characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy and galvanostatical charge-discharge test.The results indicated that the Si/G/C composites showed a high reversible capacity of more than 900 mA.h/g,which was dropped to 550 mA.h/g after 40 cycles.The cycling performance was conspicuously enhanced by a heat treatment of the anode.The capacity maintains 700 mA.h/g after 40 cycles.SEM images showed that materials on the electrode were better distributed and voids from smearing disappeared after the heat treatment.The improvement of cycling performance can be attributed to the enhancement of the electrode structure stability by densification of materials and enhanced adhesion after the heat treatment.