Synthesis of LiFePO₄ powder by the organic–inorganic steric entrapment method

Abstract

A nanoscale and pure, olivine-structured LiFePO 4 was synthesized at ;300°C using an organic-inorganic steric entrapment method. Normally, when calcined and crystallized in air, this method leads to the synthesis of compounds where the cations are in their highest oxidation state. However, in this study, we found a way to produce compounds having lower oxidation states (e.g., compounds containing Fe 21 ), which may have wider applications in the synthesis of other compounds with complex chemistry that have variable oxidation states and, therefore, potential applications in electronic ceramics. The resulting LiFePO 4 or (Li 2 OÁ2FeOÁP 2 O 5 ) was characterized by thermogravimetric analysis/differential thermal analysis, x-ray diffractometry, scanning electron microscopy, transmission electron microscopy, inductively coupled plasma emission spectroscopy, specific surface area by Brunauer-Emmett-Teller nitrogen absorption, and particle size analysis.

Synthesis of NaTi2(PO4)3 by the Inorganic–Organic Steric Entrapment Method and Its Thermal Expansion Behavior

“…The SSAs were higher than for other materials synthesized by the inorganic-organic steric entrapment method. 44,45,51 It can be noticed that the surface area of the amorphous powder was twice (83.0 m 2 /g) that of the crystalline powder (40.9 m 2 /g). Such characteristics could be useful for some applications.…”

“…[41][42][43][44][45] When the metal nitrates were dissolved in water, polyvinyl alcohol ([CH 2 CH(OH)] n ) was used as a polymeric entrapper, whereas, EG was selected when the cation sources dissolved in alcohol or hydrolyzed in water as was the case for TISO. [41][42][43][44][45] When the metal nitrates were dissolved in water, polyvinyl alcohol ([CH 2 CH(OH)] n ) was used as a polymeric entrapper, whereas, EG was selected when the cation sources dissolved in alcohol or hydrolyzed in water as was the case for TISO.…”

“…(1) Powder Synthesis The inorganic-organic steric entrapment method has been used to produce several different materials of high technological importance. [41][42][43][44][45] When the metal nitrates were dissolved in water, polyvinyl alcohol ([CH 2 CH(OH)] n ) was used as a polymeric entrapper, whereas, EG was selected when the cation sources dissolved in alcohol or hydrolyzed in water as was the case for TISO. Specifically for the synthesis of NaTi 2 (PO 4 ) 3 , a hybrid method should be used because some of the reagents (Na and P sources) dissolved in water, but not in alcohol, while another reagent such as TISO hydrolyzed in water (forming isopropyl alcohol and a hydrated form of titania) but dissolved and remained stable in alcohol.…”

“…However, 5-7 d are required for the synthesis. [41][42][43][44][45] The stabilization of cations in the precursor is established not only through the chemical (hydrogen) binding of cations with the functional groups but also, in major part, through the physical entrapment of the metal ions in the network of the dried polymer. Therefore, it is essential to develop a simple, scalable, high-yield, cost-effective technique to be suitable for mass production of these important compounds.…”

“…20 A versatile and simple technique called the inorganicorganic steric entrapment method has been developed to produce multicomponent ceramic powders. [41][42][43][44][45] The stabilization of cations in the precursor is established not only through the chemical (hydrogen) binding of cations with the functional groups but also, in major part, through the physical entrapment of the metal ions in the network of the dried polymer. This method has allowed the production of pure advanced ceramic powders at lower temperatures and shorter times than the conditions required by the traditional solidstate reaction method.…”