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To compensate the large irreversible capacity (Qirr), lithium was pre-doped to Si thin flakes (Si Leaf Powder® (Si-LP), thickness: 100 nm) for different times, and its effects on the charge/discharge characteristics such as reversible capacity, cycleability, and rate-capability were investigated in detail. The charge/discharge test results showed that a large initial Qirr of ca. 2300 mAh g− 1 for the Si-LP can be completely compensated by Li pre-doping, and a high capacity (> 2500 mAh g− 1) was obtained for pre-doped Si-LPs. The pre-doping did not cause any harmful effects on cycleability as long as lithium was uniformly pre-doped. The addition of vinylene carbonate to the electrolyte solution in the pre-doping and in the test cell greatly improved the cycleability, and a high discharge capacity of ca. 2300 mAh g− 1 was kept after 40 cycles.

Pure Si thin flakes (Si Leaf Powder® (Si-LP)) of different thicknesses (50, 100, 200, 300 and 400 nm) were prepared, and their charge/discharge properties were investigated as negative electrode materials for lithium ion batteries (LIBs). High reversible capacity (2200–2500 mAh g − 1 ) and good capacity retention were obtained for thinner Si-LPs (50–200 nm), while thicker samples (300 and 400 nm) exhibited rapid capacity fade upon cycling at C/6. For the thinner flakes, agglomeration and large cracks were confirmed on the composite electrodes, but no pulverization of the flakes was observed. These data suggested that Li atoms diffused easily within the thinner Si-LPs and the uniformity of Li distribution suppressed the localized physical stress that caused by alloying and de-alloying. In addition, the addition of vinylene carbonate (VC) in the electrolyte was found to be quite effective for improving not only the cycleability, but also the rate-capability. The best performance was obtained for Si-LP (100 nm), which exhibited a superior cycleability (ca. 2300 mAh g − 1 at C/6 after 50 cycles) and a high rate capability (ca. 1400 mAh g − 1 at 12 C rate).

Pure Si platelets (Si-LP, thickness: 100 nm) and Ni layer-laminated Si platelets with different thicknesses (Si/Ni/Si-LP50 (50/50/50 nm) and Si/Ni/Si-LP30 (30/30/30 nm)) were prepared by a vapor deposition method, and their charge/discharge properties were investigated as alternative negative electrode materials to graphite for lithiumion batteries. The shape of thin platelet effectively relieved the stress during the alloying and de-alloying processes, and improved the charge/discharge cycleability as compared with a commercially available Si powder. In particular, the laminated platelet samples showed very good cycleability, probably because of a shorter diffusion length of Li+ ions in the Si layers and an improved mechanical strength by the presence of the Ni layer.