Enhancing stable and high-rate lithium ion storage through multifunctional molecular release in a phosphorus/carbon-bipyridine hybrid anode

Abstract

Phosphorus has emerged as a promising anode material due to its high specific capacity of 2594 mA h g⁻¹ and medium redox potential of about 0.7 V (vs. Li⁺/Li). However, large volume changes and low ion reaction kinetics are still the dominant challenges that affect the long-term cycle stability and high-rate performance of phosphorus anodes. Herein, bipyridine is introduced to modify phosphorus/carbon composites. The highly doped bipyridine can be slowly released into the electrolyte during cycling, utilizing its Lewis base properties to effectively neutralize HF acid byproducts, thereby protecting the electrode integrity. Meanwhile, it can reduce the binding energy of lithium ions and solvent molecules, and promote the desolvation of lithium ions, thus improving the high-rate performance. As a result, P/C-bpy still provides a specific capacity of 1043.44 mA h g⁻¹ after 800 cycles at a current density of 1 A g⁻¹, corresponding to a capacity retention of 97.30%. And even at a high-rate of 15 A g⁻¹, it still provides a high specific capacity of 599.09 mA h g⁻¹.