Design of surface protective layer of LiF/FeF₃ nanoparticles in Li-rich cathode for high-capacity Li-ion batteries

Advanced lithium-ion batteries for renewable energy storage applications have become a major research interest in recent years. Much better performance can be realized by improvements in the material surface design, especially for the cathode materials. Here, we present a new design for a surface protective layer formed via a facile aqueous solution process in which a nano-architectured layer of LiF/FeF₃ is epitaxially grown on bulk hierarchical Li-rich cathode Li[Li_0.2Ni_0.2Mn_0.6]O₂. Coin cell tests of this material in the voltage range of 2-4.8 V indicated a high reversible capacity (260.1mAhg^-1 at 0.1 C), superior rate performance (129.9 mAhg^-1 at 20 C), and excellent capacity retention. Differential scanning calorimetry showed good thermal stability. The enhanced capacity and cycling stability are attributed to the suppression of interfacial side reactions as well as the conversion reaction resulting from the introduction of LiF/FeF₃ as a surface protective layer.