Study Of Novel Anode Materials Of Lithium-ion Batteries

Lithium-ion batteries are considered as the most promising power sources because they hold a series of considerable specific advantages, such as high potential, high energy density, long cycle life, no memory effect and Environment friendly. The commercialized anode material graphite exhibits excellent cycling behavior upon repeated charge and discharge cycles, but its theoretical capacity is limited to 372 mAh g?1, which can't satisfy the demand for higher performance battery systems. Therefore, it is urgent to develop new anode materials with larger capacity. The article introduces the study of nano-porous silicon/ graphite/ pyrolyzed carbon composite and tin-cobalt/ oxide composite.The nano-porous Si/graphite composite was prepared via two-step ball-milling followed by etching process. Then carbon coating was introduced to obtain nano-porous Si/graphite/C. SEM and TEM images characterize the microstructure of the nano-porous silicon material. The results from electrochemical test reveal that nano-porous Si/graphite/C composite exhibits much better cycle performance than nanosized Si/graphite/C composite. On the other hand, it is found that influence of composition, carbon precursor, binder type and content on the electrode performance is remarkable. The nano-porous Si/graphite/C composite electrode containing LA132 binder (10wt%) exhibits a reversible capacity of 649.9mAh/g after 200 cycles, with almost no capacity loss. The superior electrochemical characteristics are attributed to suppression of the volume expansion for lithium insertion via nanosized pores in Si particles, and the volume-buffering action as well as excellent electronic and ionic conductivity of carbon materials.Nanosized tin alloy/Al2O3 composites were synthesized by high-energy ball-milling. The combined analysis involving XRD, SEM, TEM, and EDS reveals that Sn3Co nanocrystallites are homogeneously dispersed in the alumina matrix. The results of electrochemical experiments show that the Sn3Co/Al2O3 and Sn4Ni3/Al2O3 nanocomposites as electrode materials have better cycle performance than Sn/ Al2O3. The Sn3Co/Al2O3 composite delivers a stable capacity of ca. 540 mAh g-1 which could be maintained over 35 cycles. The improved cycle stability can be contributed to enhanced conductivity of the composite and finer dispersion of active domains. On the other hand, the influence of binder on the electrode performance is remarkable. LA132 binder is fit for the alloy composite electrode owing to its strong binding strength and weak swelling effect.