Is phosphorene with intrinsic defect still an ideal anode material?

TL;DR

This study reveals that intrinsic defects in phosphorene significantly hinder its ultrafast lithium diffusion, raising concerns about its suitability as an ideal anode material in lithium-ion batteries.

Contribution

It provides a detailed first-principles analysis of how intrinsic defects affect lithium diffusion and voltage in phosphorene, highlighting the importance of defect control for battery applications.

Findings

Intrinsic defects block ultrafast lithium diffusion in phosphorene.

Defects increase the diffusion energy barrier and open circuit voltage.

Defect-free phosphorene is highly desirable for LIB applications.

Abstract

The diffusion of Li in electrode materials is key factor to charging/discharging rate capacity of Li-ion battery (LIB). Recently, two-dimensional phosphorene has been proposed as a very promising electrode material due to its ultrafast and directional lithium diffusion, as well as large energy capacity. Here, on the basis of density functional theory, we report that the intrinsic point defects, including vacancy and stone-wales defects, will block the directional ultrafast diffusion of lithium in phosphorene. On the defect-free phosphorene, diffusion of Li along the zigzag lattice direction is 1.6 billion times faster than along the armchair lattice direction, and 260 times faster than that in graphite. By introducing intrinsic vacancy and stone-wales defect, the diffusion energy barrier of Li along zigzag lattice direction increases sharply to the range of 0.17 ~ 0.49 eV, which block the ultrafast migration of lithium along the zigzag lattice direction. Meanwhile, the open circuit voltage increases with the emergence of defects, which is not suitable for anode materials. In addition, the formation energies of defects in phosphorene are much lower than those in graphene and silicene sheet, therefore, it is highly demanded to generate defect-free phosphorene for LIB applications.