Negative Electrode Properties of Sn and Si Leaf Powder® for Li-ion Batteries

Two kinds of metal thin platelets (Leaf Powder (R), Oike Co., Ltd.) based on Sn and Si were prepared, and their charge/discharge properties were investigated as alternative negative electrode materials to graphite for Li-ion batteries. One was simple metal platelets (M-LP, thickness: 100 nm) and the other was laminated platelets with an inactive Ni layer (M/Ni/M-LP, thickness: 30/30/30 nm). For both Sn and Si platelets, the shape of thin platelets effectively relieved the stress by volume expansion and shrinkage during the alloying and de-alloying processes, and improved their charge/discharge cycleabilities. Particularly, the Si platelets suppressed their agglomeration and pulverization, and much more remained the shapes than the Sn platelets. The lamination with the inactive Ni layer further improved the cycleability, though the specific capacity decreased by its presence. The alloying and de-alloying reaction with Li+ ion was substantially smooth, which was due to a decrease in the diffusion distance of Li+ ion by using the thin platelets. As a result, the Si/Ni/Si-LP exhibited a good capability over ca. 400 mAh g(-1) up to 3C rate.