Enhancing the rate performance of spherical LiFeBO3/C via Cr doping

Abstract

Spherical LiFe_1−xCr_xBO₃/C (x = 0, 0.005, 0.008) has been successfully synthesized by ball-milling and spray-drying assisted high-temperature solid-state reaction. The effect of Cr doping on LiFeBO₃/C is characterized by XRD, energy-dispersive X-ray spectroscopy (EDS) and XPS. The results show that LiFe_0.995Cr_0.005BO₃/C delivers the highest initial discharge specific capacity of 196.3 mA h g⁻¹ at 0.1C and superior rate capability of 90 mA h g⁻¹ at 5C. Moreover the material presents a cyclic retention of 95% after 50 cycles at 1C. Such improvement in the electrochemical performance can be attributed to the high electronic conductivities (4.75 × 10⁻⁵ S cm⁻¹) and Li ion diffusion coefficients (9.20 × 10⁻¹³ cm² s⁻¹). The introduction of supervalent Cr³⁺ into the LiFeBO₃ lattice produces Fe vacancies with accompanying conduction electrons, which lead to the enhanced electronic conductivity and Li ion diffusion coefficient.