Delithiation kinetics study of carbon coated and carbon free LiFePO4

Manganese dissolution in lithium-ion positive electrode materials

“…The positive electrode base materials were research grade carbon coated C-LiFe0.3Mn0.7PO4 (LFMP-1 and LFMP-2, Johnson Matthey Battery Materials Ltd.), LiMn2O4 (MTI Corporation), and commercial C-LiFePO4 (P2, Johnson Matthey Battery Materials Ltd.). The negative electrode base material was C-FePO4 prepared from C-LiFePO4 as describe by Lepage et al [35] Phase purity of the research grade samples was confirmed using a Philips X'pert diffractometer (2ϴ = 15⁰-75⁰) with a CuKα source. 18.8 ± 0.1 ppm (mass of HF per mass of total electrolyte) for electrolyte A and B respectively, was completed as describe by Chen et al [36] with minor modifications: Titrations were performed on a slurry composed of 3g of crushed ice, 1 mL of water, 5 drops of indicator (bromothymol blue 0.04%) and approximately 1g of electrolyte (accurately weighted) using NaOH 0.005N standardized with potassium biphtalate primary standard (Sigma-Aldrich).…”

Interpreting Lithium Batteries Discharge Curves for Easy Identification of the Origin of Performance Limitations

“…Moreover, recent results show that very complex delithiation reaction mechanisms lead to kinetics, which within the experimental error can be approximated to spherical diffusion [29].…”

“…The corresponding equation system is presented in the supporting information section. Importantly, while it has been shown previously that the microscopic mechanism for lithium uptake and release is remarkably complex for the Li1-xFePO4 system [21][22][23][24][25][26][27][28], we here use a spherical diffusion model to describe lithium transport, as recent data suggests that this yield correct kinetic predictions within the experimental error for the oxidation process [29]. The numerical investigation of a wide range of model parameter combinations, followed by the careful analysis of the resulting discharge curves lead to the conclusion, that two unique sets of circumstances entailed a sharp decrease of potential and that these are depending on very few parameters.…”

Methods for Determination of the Degree of Iron Oxidation in LiFePO4

“…The degree of oxidation of of LiFePO4 was determined by Ox-Red titration with potassium dichromate of a dissolved sample in an acidic medium. The known mass of Chemical oxidation without material dissolution can serve as a method for determining the transport parameters of the chemical delithiation process, such as diffusion coefficient and activation energy [11][12][13].…”

“…Since LiFePO 4 is stable in aqueous media, chemical delithiation is most convenient in them. In [12] chemical delithiation was realized using hydrogen peroxide as an oxidizer in a weak acidic medium, thus permitting the determination of the kinetic parameters of the delithiation process.…”