Three-Dimensional Porous LiFePO4 Cathode Composite Decorated By Nitrogen-Doped Graphene Aerogel for Ultrafast Lithium Storage

Abstract

Being a candidate of Lithium-ion batteries (LIBs) cathode material, olivine structured LiFePO4 (LFP) has various advantages, however, the major problems associated with LFP still lie in the fact of its poor electric conductivity and low Li+ diffusivity along the [010] direction only[1-2]. Based on this viewpoint, we wrapped (010) facet orientated LFP nanoplatelets (LFP NPs) with N-doped graphene aerogel (N-GA) to prepare a porous N-GA modified LFP composite (LFP@N-GA) through a facile electrostatic attraction treatment combined with a self-assembly process. In such a composite as shown in Figure. 1a-1i, LFP NPs are well surrounded by a N-GA constructed bicontinuous conductive network, which effectively facilitate both Li+and electron transport, and thus, effectively reducing the polarization[3-4]. Electrochemical test results demonstrated that the LFP@N-GA composite electrode indeed exhibited a ultrahigh rate capability (78 mAh·g−1at 100 C) and a stable cyclability (90% capacity retention over 1000 cycles at 10 C), as shown in Figure. 1j and 1k[5-6]. Such a LFP@N-GA cathode material may advance the development of high-power LIB for EVs and HEVs, and the preparation method is independent from the morphology and the synthesis process of the electrochemically active material, and therefore, compatible with many other energy-storage materials for different applications. Figure 1.Characterization and electrochemical performance of LFP@N-GA composite: (a, b) SEM images at different magnification. (c-h) TEM and HRTEM images. Inset of d: FFT pattern of the HRTEM image, where B denotes the beam direction, indicating the (010) facet orientation. (i) HAADF-STEM image and elemental mapping results of LFP@N-GA. (j) and (k) Rate and cycling performance. Reference ： [1]Padhi A. K., Nanjundaswamy K. S., et al., J. Electrochem. Soc., 1997, 144, 1188-1194. [2]Wang B., Xu B., et al., Nanoscale, 2014, 6 (2): 986-995. [3]Wang B., Wang Q., et al., RSC Adv., 2013, 3 (43): 20024-20033. [4]Wang B., Wang S., et al., Mater. Lett., 2014, 118: 137-141. [5]Wang B., Al A. W., et al., Energy Environ. Sci., 2015, 8 (3): 869-875. [6]Wang, B.; Wang D., et al., J. Mater. Chem. A, 2013, 1 (1): 135-144. Figure 1