Synthesis and Characterization of Amorphous 3Fe[sub 2]O[sub 3]⋅2P[sub 2]O[sub 5]⋅10H[sub 2]O and Its Electrode Performance in Lithium Batteries

Abstract

Amorphous 3Fe 2 O 3 •2P 2 O 5 •10H 2 O was prepared by oxidation of iron͑II͒ phosphate, obtained by spontaneous precipitation from iron͑II͒ and phosphate aqueous solutions, by heating in air at 100°C. The material was characterized by thermal analysis, Mo ¨ssbauer spectroscopy, X-ray powder diffraction, and scanning electron micrograph analysis. The material, tested as cathode in a nonaqueous lithium cell, exhibited a specific capacity of about 140 mAh g Ϫ1 at a current density of 25 mA g Ϫ1 . The utilization was reduced to about 76% by a tenfold increase of the discharge current. It showed an excellent cyclability. More than 1000 cycles were performed at about 50% of depth of discharge, with a capacity fade lower than 0.025%.

Electrochemical performances of FePO4-positive active mass prepared through a new sol–gel method

“…As mentioned above, it is obvious that such a performance is closely linked to the electrode surface area [23,24]. A similar behavior of good performance was observed by other authors [6][7][8], who explained it by the increase of the amorphous phase content as T c decreased. In spite of the higher surface value of the sample calcinated at 350°C, this latter shows an opposite trend, very likely because its structure being not well defined (cf.…”

“…It should be mentioned that the synthesis conditions used here give rise to a crystalline phase at temperatures well below those reported in the literature [6][7][8].…”

“…Prosini et al [6,7] and Song et al [8] characterized its electrochemical behavior as Li + -intercalation host and stated that the performances of this material are primarily related with its amorphous character. In the present study, we exploited the advantages of a sol-gel synthesis to yield a material with high specific surface area (low grain size), and we report on the behavior of this compound, prepared in the crystalline state, and look into the origin of its electrochemical activity.…”

The hydrothermal synthesis and characterization of olivines and related compounds for electrochemical applications

“…In contrast to the crystalline ferric phosphate discussed above, amorphous ferric phosphate formed by the dehydration of the hydrate has a much higher capacity. Four different research groups published essentially identical data on this material [54,55,[96][97][98]. We found that the highest capacity was attained after complete dehydration at 350°C; at higher temperatures the electrochemically inactive verlinite phase begins to form.…”

A versatile method for preparing FePO4 and study on its electrode performance in lithium ion batteries

“…During the dilithiation process, the structure of LiFePO 4 is similar to FePO 4 and exhibits a little contraction in parameters a and b, a small increase in parameter c. The FePO 4 has also been proposed to be suitable cathode materials in lithium batteries, and lithium metal phosphates can be used as either cathode or anode in lithium batteries (Chen et al, 1996). With the conventional method of spontaneous precipitation of a solution containing Fe 3+ and PO 4+ at neutral or alkaline pHs, a wide series of lithium free iron phosphates have been prepared for (Prosini et al, 2001(Prosini et al, , 2002, Whittingham (Song et al, 2002a,b,c), Masquelier (Masquelier et al, 2002), Salah (Ait Salah et al, 2006) and Li (Li et al, 2006). Their results are in satisfactory agreement and inspirit later researches to improve its electrochemical performance as electrode materials.…”