Effects of Li pre-doping on charge/discharge properties of Si thin flakes as a negative electrode for Li-ion batteries

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.