A novel scalable synthesis of high-rate performance silicon anode materials by liquid-phase coating doping method

Abstract

Recycled solar grade p-type silicon (Si) broken wafers (1–10 Ω·cm) were milled to Si powders, and then doped with phosphoric acid to make n-type Si powders with extremely high conductivity for being used as anode materials for lithium ion batteries. The electrical conductivity of as-obtained phosphorus-doped (P-doped) Si powders is as high as 5263.18 μs/cm, which is nearly 5 × 103 times higher than undoped Si (1.04 μs/cm). The charge specific capacity of P-doped Si holds 1920.3 mAhg−1 after 50 cycles at 0.84 A g−1, when the charge current density increased to 21 A g−1 (only take 12 min for charging), it still maintains at 1758.5 mAhg−1 after 50 cycles. This proves the outstanding cycle stability of P-doped Si at high rate, which can be attributed to the improved conductivity and lithium ion diffusion coefficient. For practical application in full cells, P-doped Si was composited with artificial graphite to be used as the anode, and the cathode adopted was commercial LiNi0.5Co0.2Mn0.3O2, which also discloses excellent long cycle stability with a high capacity retention of 80.7% even after 700 cycles at 0.5C (1C = 420 mA g−1).