Synthesis of the LiFePO4/graphene composite and its enhanced properties as cathode materials for lithium ion batteries

Publish Year: 1394
نوع سند: مقاله کنفرانسی
زبان: English
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شناسه ملی سند علمی:

ELECTROCHEMISTRY011_085

تاریخ نمایه سازی: 5 بهمن 1395

Abstract:

LiFePO4 is the most promising cathode materials for lithium-ion batteries (LIBs). the bare LiFePO4 shows poor rate capability because of its intrinsically low electronic conductivity.Incredible efforts have been devoted to improve the electron conductivities by coating physically and/ or chemically a thin layer of conductive carbon or derivatives on it [1-3]. Graphene have been demonstrated as one of optimal materials to modify the electrode materials, includingLiFePO4 [4]. In the work, we designed and fabricated a composite of LiFePO4 modified with graphene. Fig. 1shows the SEM images of as-prepared LiFePO4/graphene composite. To get insight into the graphene coating effect on the electrodynamics of LiFePO4, EIS measurements were carried outon the cells with LiFePO4/graphene as cathode. The as-measured Nyquist plot is shown in Fig. 2. The plot was a combination of a depressed semicircle in the high frequency region and a spike in the low frequency region. Previous explanation on the impedance spectra is that the highfrequency semicircle is related to the migration of the Li+ ions at the electrode/electrolyte interface and charge transfer process. The spike is attributed to the Warburg impedance of longrange Li-ion diffusion [5]. Compared with that LiFePO4, a smaller depressed semicircle has beenshown for composite, indicating much lower interface impedance between the metal current collector and electrode materials, which may be beneficial to the rate performance of composite. Cyclic voltammetry was performed in order to investigate the effect of graphene on theelectrochemical properties of LiFePO4 by using a scanning rate of 0.1 mV s−1. The CV of LiFePO4 /graphene composite show more symmetrical and sharper shape of the anodic/cathodic peaks, which indicates the better electrochemical activity.

Authors

Mohadese Rastgoo-Deylami

Department of Chemistry, Amirkabir University of Technology, Tehran, Iran Solar Cell and Fuel Cell Lab, Renewable Energy Research Center, Amirkabir University of Technology, Tehran, Iran

Khadijeh Hooshyari

Department of Chemistry, Amirkabir University of Technology, Tehran, Iran Solar Cell and Fuel Cell Lab, Renewable Energy Research Center, Amirkabir University of Technology, Tehran, Iran

Mehran Javanbakht

Department of Chemistry, Amirkabir University of Technology, Tehran, Iran Solar Cell and Fuel Cell Lab, Renewable Energy Research Center, Amirkabir University of Technology, Tehran, Iran