Abstract
This work focuses on the synthesis of LiFePO4–PANI hybrid materials and studies their electrochemical properties (capacity, cyclability and rate capability) for use in lithium ion batteries. PANI synthesis and optimization was carried out by chemical oxidation (self-assembly process), using ammonium persulfate (APS) and H3PO4, obtaining a material with a high degree of crystallinity. For the synthesis of the LiFePO4–PANI hybrid, a thermal treatment of LiFePO4 particles was carried out in a furnace with polyaniline (PANI) and lithium acetate (AcOLi)-coated particles, using Ar/H2 atmosphere. The pristine and synthetized powders were characterized by XRD, SEM, IR and TGA. The electrochemical characterizations were carried out by using CV, EIS and galvanostatic methods, obtaining a capacity of 95 mAhg−1 for PANI, 120 mAhg−1 for LiFePO4 and 145 mAhg−1 for LiFePO4–PANI, at a charge/discharge rate of 0.1 C. At a charge/discharge rate of 2 C, the capacities were 70 mAhg−1 for LiFePO4 and 100 mAhg−1 for LiFePO4–PANI, showing that the PANI also had a favorable effect on the rate capability.
Highlights
Since Sony developed and commercialized the first lithium-ion batteries based on LiCoO2 in1990, new materials and different applications have driven research and development
PANI was synthesized by chemical oxidation with good crystallinity, with primary particle size of
LiFePO4 –PANI and LiFePO4 particles are similar, but the PANI coating on the LiFePO4 particles gives a different surface structure in the composite. This is supported by elemental mapping, which shows a homogeneous distribution of carbon and sulfur in PANI on the surface of LiFePO4 particles
Summary
Since Sony developed and commercialized the first lithium-ion batteries based on LiCoO2 in. Hybrid electrodes for lithium-ion batteries incorporating PANI with LiMn2 O4 [19], MnO2 [20], V2 O5 [21] and Li(Mn1/3 Ni1/3 Fe1/3 )O2 [22]. Various dopants have been used to improve the physical and chemical properties of PANI Among them, salts such as LiClO4 , LiBF4 , LiPF6 and Zn(ClO4 ) have received much attention, and their application in rechargeable lithium-ion batteries has been extensively studied [24]. The most common method for the synthesis of LiFePO4 –PANI is the shelf-assembly process, PANI is incorporated with LiFePO4 particles through simultaneous chemical polymerization with APS as the oxidizer, and aniline and an inorganic acid as dopants [12]. This work is focused on the synthesis, structural characterization and electrochemical characterization of LiFePO4 –PANI as a cathode material for lithium-ion batteries. Rate capability and cyclability were measured for the LiFePO4 –PANI and showed improvement when compared to the pure materials
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