Overcoming redox barriers in black phosphorus negative electrodes through lattice P-N engineering for fast-charging Li-ion batteries.

Electrochemical energy storage devices commonly face a trade-off between specific energy and power capability. Black phosphorus offers a high theoretical capacity of 2596 mA h g-1, but its practical application is limited by slow reaction kinetics during multiphase phosphorus redox processes. These sluggish transformations, involving bond rearrangement and soluble intermediates, hinder fast charging and compromise cycling stability. Here we show that introducing phosphorus-nitrogen bonds into a black phosphorus/carbon composite regulates the reaction pathway and accelerates charge transport. The engineered bonding environment modifies the electronic structure of black phosphorus and lowers lithium-ion diffusion barriers, enabling faster lithiation and delithiation. Meanwhile, nitrogen sites in the carbon matrix confine lithium-phosphorus intermediates, reducing their migration and improving structural stability. This combined effect enhances both rate capability and reversibility. When coupled with lithium iron phosphate in a pouch cell, the composite negative electrode delivers a specific energy of 282 Wh kg-1 and retains 80% of its capacity after 10 min of charging at high specific current. The device also maintains stable operation over thousands of cycles, demonstrating improved durability under fast charging conditions.