High voltage transition metal-free cathode material LiBC3F4 for Li ion batteries

TL;DR

This study introduces LiBC3F4, a high voltage, transition metal-free cathode material for Li-ion batteries, demonstrating excellent stability, high voltage, and promising electrochemical properties through first principles calculations.

Contribution

The paper presents a novel boron-substituted fluorinated graphite cathode with superior voltage and stability, advancing transition metal-free battery materials.

Findings

LiBC3F4 has an average intercalation voltage of 4.44 V.

LiBC3F4 exhibits excellent structural stability and conductivity.

A linear correlation between Fermi level and intercalation voltage was identified.

Abstract

The structural stability and electrochemical performance of boron substituted fluorinated graphite as a Li ion batteries cathode material are studied by first principles calculations. The results show that boron substituted fluorinated graphite BC3F4 possesses excellent structural stability, good electrical and ionic conductivities. Unexpectedly, the average Li intercalation voltage of LiBC3F4 is up to 4.44 V, which is much larger than that of LiBCF2. The average voltage of LiBC3F4 is even larger than that of common commercial transition metal oxides cathodes, indicating that LiBC3F4 is a breakthrough of transition metal-free high voltage cathode materials. By comparing the Fermi level, we found the Fermi level of LiBC3F4 is 1.38 eV lower than that of LiBCF2, leading to the decrease of the electron filling energy for the Li intercalation and forming much higher voltage. Moreover, LiBC3F4 shows small volume expansion and high energy density. LiBC3F4 is a promising high voltage cathode material for Li ion batteries. Finally, by calculating the evolution of Li intercalation voltage and Fermi level during the discharging process, a linear correlation between the Fermi level and Li intercalation voltage has been found.