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

Abstract

This investigation is a contribution to the research on alternative cathode materials with much more promising performances for lithium batteries. It deals with the electrochemical properties of iron phosphate compound FePO 4 , chemically prepared through the so-called sol-gel Pechini process, terminated by a calcination of the product precursor at temperatures (T c ) ranging between 350°C and 650°C. A crystalline phase was obtained for temperatures ≥400°C. The particle size decreased with the decrease in T c , giving rise to a Brunauer-Emmett-Teller (BET)-specific surface area, S BET , as high as 28 m 2 g −1 for the sample annealed at 400°C. The electrochemical properties of FePO 4 -based composite cathodes were characterized on three-electrode laboratory cells. Charge-discharge cycling determined a maximum reversible capacity of 132 mAh g −1 , which fell with the increase in T c . A direct correlation was established between the activity of the material and its active surface area.

A green recycling process designed for LiFePO4 cathode materials for Li-ion batteries

“…2(d). Many studies report on the particle growth with the increasing heat treatment temperature; 11,22,33,39 in addition, the initial precursor shape and size are also important factors to determine the nal morphologies of the resulting products. 22,37,66 High resolution transmission microscopy (HRTEM) is used to detect the presence of carbon on the surface of recycled LiFePO 4 /C, as shown in Fig.…”

“…24 In addition to LiFePO 4 , various amorphous and crystalline phases of iron phosphates, FePO 4 and FePO 4 $nH 2 O, have been proposed as the cathode materials in lithium ion batteries. [25][26][27][28][29][30][31][32][33][34][35] Although many space groups of iron phosphates have been intensively investigated over the years, whether they are either anhydrous or hydrated forms and amorphous or crystalline in their structures, it was not until recent years that a maximum reversible capacity of 132 mA h g À1 was achieved during the charge-discharge process with 22% carbon black in the cathode composite, using the FePO 4 active material annealed at 400 C. 33 Especially, Delacourt et al studied on the lithium de-/ insertion mechanism of many types of amorphous and crystalline iron phosphates, with capacities ranging between $120 and $140 mA h g À1 at a C/20 rate. 34 Tavorite-type FePO 4 $H 2 O intercalates lithium ions at a potential of $2.6 V vs. Li/Li + , delivering >160 mA h g À1 during the rst charge, however, an irreversible capacity loss of 30% is observed for the subsequent cycles, where the capacity stabilizes at 120 mA h g À1 .…”

Iron Phosphate Prepared by Coupling Precipitation and Aging: Morphology, Crystal Structure, and Cr(III) Adsorption

“…Several synthetic routes have been reported for synthesizing iron phosphate according to specific needs for different applications, such as nanoparticle FePO 4 fabricated by using CTAB for lithium batteries, nanotube FePO 4 synthesized by the solvothermal method for catalysis, naonosphere FePO 4 synthesied by the microwave method for biosensoring, and so forth. − However, few of them are concerned about systematic manipulation of the morphology and structure. Especially, more detailed and intuitive evidence is still scarce for better understanding the kinetic process and mechanism of crystal and morphology growth.…”

Preparation of Doped Iron Phosphate by Selective Precipitation of Iron from Titanium Dioxide Waste Acid

“…The price of these analytical pure iron salts is relatively high, and some doping elements (such as Mg, Mn, Al, Ti, etc.) which are beneficial to their electrochemical properties need to be added when they are used to prepare high-performance lithium iron phosphate [16][17][18][19]. These doping elements happen to exist in the titanium dioxide waste acid.…”