Tannic Acid-Derived Carbon Coating on LiFePO₄ Nanocrystals Enables High-Rate Cathode Materials for Lithium-Ion Batteries

Tannic acid (TA) is a plant polyphenol capable of coating hydrothermally grown LiFePO 4 nanocrystals by simple wet impregnation and drying. Mild pyrolysis in an inert atmosphere transforms the TA coating on LiFePO 4 nanocrystals into homogeneous and compact carbon films. Introducing conductive carbon films on LiFePO 4 nanocrystals increases the electrical conductivity of the LiFePO 4 /C composite. However, reaction kinetics revealed that excessively thick carbon films limit the Li + diffusivity of the LiFePO 4 /C composite during delithiation/lithiation. Therefore, the electrical conductivity and Li + diffusivity must be balanced to achieve the required electrochemical properties.