Solid State Reaction Mechanisms of the LiMnPO₄ Formation Using Special Function and Thermodynamic Studies

Abstract

LiMnPO 4 was successfully synthesized via thermal decomposition processes of the synthesized MnHPO 4 ·3H 2 O precursor. Thermogravimetry/differential thermal gravimetry/differential thermal analysis, Fourier transform infrared, atomic absorption spectrophotometry, X-ray diffraction, and scanning electron microscopy techniques were employed for the characterization of the samples. Three thermal decomposition steps in the sequence of dehydration, polycondensation, and decarbonization were observed. The iterative Kissinger−Akahira−Sunose method was used to calculate the exact E α values. Regions I and II of the first, second, and final steps were confirmed to be single-step kinetic processes with the unique kinetic triplets. The most probable mechanism functions were found to be R 3 , R 2 , A 2 , and P 4 corresponding to contracting sphere, contracting cylinder, assumed random nucleation (its subsequent growth), and nucleation processes, respectively. The preexponential factors, A, were calculated using E α and g(α). The thermodynamic functions of the transition-state complexes were evaluated from the pre-exponential factors. The kinetic triplets, reaction mechanisms, and calculated thermodynamic functions of the formation of LiMnPO 4 are reported for the first time.

In Situ Coating of Li[Ni0.33Mn0.33Co0.33]O2 Particles to Enable Aqueous Electrode Processing

“…However, the neat changes observed in Figure b (10 wt % PA) must originate from surface species formed as a result of the acid treatment. The H 2 O + peak observed at 165 °C can be related to the elimination of water molecules from transition metal hydrogen phosphate precipitates (e.g., MnHPO 4 ⋅3 H 2 O) . These results confirm the XPS analysis, which indicated the presence of transition metal hydrogen phosphates.…”

LiMn0.8Fe0.2PO4@C cathode prepared via a novel hydrated MnHPO4 intermediate for high performance lithium-ion batteries

“…The topology of the metal phosphate layer in the ac face of MnHPO 4 is similar to that of the metal phosphate layer in the bc face of LiMnPO 4 , which is beneficial to the structural transformation from MnHPO 4 to LiMnPO 4 without structural rearrangement. [31][32][33] Hence, hydrated MnHPO 4 is a good candidate intermediate compound for the preparation of LiMnPO 4 . The difference between them is that hydrogen atoms are located in the channels of the MnHPO 4 structure instead of Li + in LiMnPO 4 .…”

“…34 Due to the fracture of H-O bonds in HPO 4 2− in the process of high-energy ball milling and hyperthermal sintering, a transformation from MnHPO 4 into LiMnPO 4 can be achieved without major structural rearrangement. 31,35 Therefore, the morphology and size distribution of LiMnPO 4 can be easily regulated by tailoring those of the hydrated MnHPO 4 intermediate. Furthermore, phenolic resin as a carbon source can be uniformly dissolved in the alcohol solvent.…”

“…In the second step, the two exothermic peaks at 339.4 and 365.9 °C can be assigned to the polycondensation of MnHPO 4 and Mn 5 (PO 4 ) 2 [(PO 3 )OH] 2 . In addition, Sronsri et al 31 reported that the exothermic peak dominating at 577 °C indicates a phase change from non-crystallinity to crystallinity in the Mn 2 P 2 O 7 structure. It can be rationalized that the exothermic peak at 578.6 °C of MP-0.5 represents the completed crystalline transition.…”