Effect of Phosphorus Doping on Conductivity, Diffusion, and High Rate Capability in Silicon Anode for Lithium-Ion Batteries

Abstract

Poor long-term cycling stability and rate capability seriously restricted the commercial applications of silicon (Si) anodes, because of the huge volume change and the kinetic problems linked to the electronic conductivity and solid-state diffusion of Li+. To overcome these challenges, herein, heteroatom phosphorus (P), as the dopant, is successfully incorporated with silicon to form coral-like P-doped Si anode in lithium-ion batteries. Such the coral-like P-doped Si anode exhibits a noticeable specific capacity (2460.4 mA h g–1 at 0.2 A g–1), excellent rate capability (911 mA h g–1 at 16 A g–1), and long cycling stability (1564 mA h g–1 after 100 cycles at 2 A g–1), which are attributed to three factors: (1) the three-dimensional interconnected nanopores of the coral-like P-doped Si could accommodate volume expansion during cycling; (2) P doping improves the electron-donating ability and suppresses the polarization effect; (3) low activation energies and high Li+ diffusion coefficient are mapped and calculated from the nano- to micrometer and macroscales, verifying that the high Li+ diffusion facilitates the redox kinetics of Si species.