Enhanced Electrochemical Capability of LiNi_1/3Co_1/3Mn_1/3O₂ Cathode Materials Coated with Fluoroborate Glass for Lithium‐Ion Batteries

Abstract

Abstract A LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM) cathode material is coated with fluoroborate glass ( x Li 2 O‐ y B 2 O 3 ‐ z LiF) to improve the electrochemical performance of lithium‐ion batteries. An x Li 2 O‐ y B 2 O 3 ‐ z LiF layer was successfully coated onto the surface of NCM by using a solution‐phase method. The resulting materials are characterized by using X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy. The x Li 2 O‐ y B 2 O 3 ‐ z LiF‐coated NCM exhibits a superior discharge capacity, rate capability, and cycling stability than those of the uncoated material. Notably, the initial discharge capacity of bare and 2Li 2 O‐B 2 O 3 ‐LiF‐coated NCM were 182.1 and 207.5 mAhg −1 , respectively, in the voltage range from 2.5 to 4.5 V. At a rate of 5C, the discharge capacity of Li 2 O‐B 2 O 3 ‐LiF‐coated NCM is 144.4 mAhg −1 , whereas that of bare NCM is 76.7 mAhg −1 . After 50 cycles at a rate of 0.2C, the capacity retentions of Li 2 O‐B 2 O 3 ‐LiF‐, 2Li 2 O‐B 2 O 3 ‐LiF‐, Li 2 O‐2B 2 O 3 ‐LiF‐, and Li 2 O‐B 2 O 3 ‐2LiF‐coated NCM are 96.8, 97.2, 95.6, and 95.2%, respectively, whereas the capacity retention of bare NCM is 81.4%. Cyclic voltammetry and electrochemical impedance spectroscopy results indicate that the x Li 2 O‐ y B 2 O 3 ‐ z LiF coating reduces electrode polarization and decreases charge‐transfer resistance at the electrolyte–electrode interface, further improving the electrochemical activity of the NCM cathode material.