A Peapod‐like CoP@C Nanostructure from Phosphorization in a Low‐Temperature Molten Salt for High‐Performance Lithium‐Ion Batteries

A mild phosphorization process in low‐temperature molten salt (NaCl‐KCl‐AlCl3) has been developed to synthesize peapod‐like CoP@C nanostructures by using low‐toxicity industrial PCl3 as the phosphorus source and Mg as the reductant at 250 °C. Importantly, high efficiency of the phosphorous source is achieved since only stoichiometric PCl3 is required to complete the reaction. The molten NaCl‐KCl‐AlCl3 not only provides a liquid environment but also participates in the electron transport by the reversible conversion of the Al3+/Al redox couple. The obtained 0D‐in‐1D peapod CoP@C structure exhibits excellent lithium storage performance, delivering a superiorly stable capacity of 500 mAh g−1 after 800 cycles at a high current of 1.0 A g−1. Mild phosphorization with a low‐toxicity phosphorus source and magnesium in a low‐temperature molten salt is used in the high‐efficiency synthesis of peapod‐like CoP@C with superior lithium storage performance. This represents a significant breakthrough for the development of phosphide based functional materials.