Encapsulation of LiFePO₄Nanoparticles into 3D Interpenetrating Ordered Mesoporous Carbon as a High-Performance Cathode for Lithium-Ion Batteries Exceeding Theoretical Capacity

Abstract

A nanocomposite cathode based on LiFePO4 (LF) nanoparticles embedded 3D cubic ordered mesoporous carbon CMK-8 for lithium-ion batteries is synthesized by a facile impregnation method followed by further modification with carbon coating. The effects of variation of carbon contents on electrochemical performances of cathodes are investigated. The highly crystalline nanophase of LiFePO4 particles is confirmed by X-ray diffraction and TEM analysis. Nitrogen adsorption–desorption isotherms reveal persistence mesoporosity after encapsulation of LiFePO4 nanoparticles. The graphitic phase in LF/C@CMK-8-X (X = amount of CMK-8) nanocomposites is detected by analyzing the Raman spectra of the matrix carbon due to CMK-8 and the coated carbon (C). The electrochemical properties of the LF/C@CMK-8-X nanocomposites are evaluated with cyclic voltammetry, impedance spectroscopy, and charge–discharge cycling. The excellent rate capability with a discharge capacity value of 184.8 mA h g–1 is obtained for LF/C@CMK-8-0.5 nanocomposite electrode at a current rate of 0.05C, which is higher than the theoretical capacity of LiFePO4 (170 mA h g–1). The discharge capacity (178.3 mA h g–1) is higher than the theoretical capacity up to the current rate of 0.2C. The long cycle stability test at a higher current rate of 10C exhibits remarkable discharge capacity of 120 mA h g–1 with 96.7% capacity retention after 1000 cycles and demonstrates the great potential of LF/C@CMK-8-0.5 nanocomposite cathode for use in lithium-ion batteries.