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 similar to 7 nm. In the electrode made from 7 nm diameter B and P co-doped Si NPs, the capacity is similar to 3300 mAh/g and the Coulombic efficiency is similar to 97% at a charge-discharge rate of 0.2C rate.