Unlocking High‐Current Performance in Silicon Anode: Synergistic Phosphorus Doping and Nitrogen‐Doped Carbon Encapsulation to Enhance Lithium Diffusivity

Abstract

The silicon (Si) offers enormous theoretical capacity as a lithium‐ion battery (LIB) anode. However, the low charge mobility in Si particles hinders its application for high current loading. In this study, ball‐milled phosphorus‐doped Si nanoparticles encapsulated with nitrogen‐doped carbon (P‐Si@N‐C) are employed as an anode for LIBs. P‐doped Si nanoparticles are first obtained via ball‐milling and calcination of Si with phosphoric acid. N‐doped carbon encapsulation is then introduced via carbonization of the surfactant‐assisted polymerization of pyrrole monomer on P‐doped Si. While P dopant is required to support the stability at high current density, the encapsulation of Si particles with N‐doped carbon is influential in enhancing the overall Li+ diffusivity of the Si anode. The combined approaches improve the anode’s Li+ diffusivity up to tenfold compared to the untreated anode. It leads to exceptional anode stability at a high current, retaining 87% of its initial capacity under a large current rate of 4000 mA g−1. The full‐cell comprised of P‐Si@N‐C anode and LiFePO4 cathode demonstrates 94% capacity retention of its initial capacity after 100 cycles at 1 C. This study explores the effective strategies to improve Li+ diffusivity for high‐rate Si‐based anode.