Single-Nanometer-Sized Boron and Phosphorus Co-Doped Silicon Nanoparticles for Negative Electrode of Lithium-Ion Batteries

A Si-based negative electrode for lithium-ion batteries (LIBs) is produced from methanol solutions of single-nanometer-size B and P co-doped Si nanoparticles (NPs) by drop-coating the solution on a substrate in air without using binders and conductive additives. Stable charge–discharge cycles are observed for films produced from Si NPs in the size range from less than 2 to 12.5 nm in diameter. It is shown that the performance and stability of the electrodes depend strongly on the size. The initial capacity increases with the size, while the stability decreases. The optimum diameter is ∼7 nm. In the electrode made from 7 nm diameter B and P co-doped Si NPs, the capacity is ∼3300 mAh/g and the Coulombic efficiency is ∼97% at a charge–discharge rate of 0.2C rate.