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Direct contact prelithiation is considered an important means of addressing the low Coulombic efficiency of Si-based anodes. However, few studies have been conducted on the inhibition of volume expansion of Si-based materials and the reduction of side reactions during direct contact prelithiation. In this paper, Li2SiF6 crystals are generated in situ in an amorphous SiO matrix by a thermodynamic reaction between SiO and LiPF6, which is from the viewpoint of contact state at the interface between lithium source and negative electrode as well as the construction of mechanical buffer phase. On the one hand, Li2SiF6 crystals can inhibit the volume expansion of SiO during prelithiation. On the other hand, Li2SiF6 crystals act as an interfacial passivation layer to reduce local currents and inhibit the occurrence of side reactions during direct contact prelithiation. The analysis of the results showed that Li2SiF6 crystals were embedded in an amorphous SiO matrix to prepare the SiO/C composite anode, and the strength of the crystals was utilized to inhibit the volume expansion of SiO during the direct contact prelithiation process. Meanwhile, due to its good ionic conductivity, a strong and tough LiF-rich solid electrolyte interphase (SEI) was constructed, which suppressed the volume expansion of the composite anode for the prelithiation process. The full battery assembled with NCM111 positive electrode still exhibits 94.5% capacity retention after 150 cycles at 0.5C current density. [ABSTRACT FROM AUTHOR]

For the purpose of determining the interaction parameters between Mn and Al, and the influence of Mn on Al2O3 inclusions formation in the Fe-Mn-Al-O melts with high Mn and Al contents, three groups of Fe-Mn-Al-O melts with the initial Al content of 3, 5, and 7 mass% and different Mn contents were equilibrated with pure solid Al2O3 in an Al2O3 crucible at 1873 K and Ar-H2 atmosphere. Then, the interaction parameters between Mn and Al were deduced using the WIPF (Wagner's Interaction Parameter Formalism) and the R-K polynomial (Redlich-Kister type polynomial), respectively. From the WIPF, the first- and second-order interaction parameters, e Al Mn and r Al Mn , were determined to be 0.0292 and −0.00016, respectively. From the R-K polynomial, the binary interaction parameters, Ω Mn - Al 0 and Ω Mn - Al 1 , were determined to be 73,439 J/mol and −34,919 J/mol, respectively. The applicability of the WIPF to high Mn and Al content Fe-Mn-Al-O melts was investigated by comparing the Al activity calculated by the WIPF and the R-K polynomial using the obtained data. The results showed that WIPF can be used in high Mn and Al content melts in the current concentration range. Further from the iso-activity contours of Al, the activity of Al increases with increasing Al or Mn content. Finally, the thermodynamic calculations show that the addition of Mn decreases the equilibrium O content at the same Al content, making the formation of Al2O3 inclusions easier. [ABSTRACT FROM AUTHOR]

In the present study, an approach of determining the standard Gibbs energy of formation of Fe3–xVxO4 was proposed firstly, then the standard Gibbs energies of formation of a variety of Fe3–xVxO4 were determined experimentally, and finally, a calculating model of the standard Gibbs energy of formation of Fe3–xVxO4 was established. The detailed results are as follows: (1) the standard Gibbs energy of formation of Fe3–xVxO4 can be determined successfully by two steps; the first is to measure the chemical potential of Fe in Fe3–xVxO4 under fixed oxygen partial pressure, the second is to derive the chemical potential of V in Fe3–xVxO4 by Gibbs–Duhem relation; (2) the standard Gibbs energies of formation of Fe3–xVxO4 are mainly decided by the Fe/V molar ratio, and almost not influenced by the oxygen partial pressure in the range from 2.39 × 10−12 to 3.83 × 10−11 atm; (3) in this oxygen partial pressure range, the standard Gibbs energies of formation of Fe3–xVxO4 can be calculated satisfactorily by the following model: Δ f G F e 3 − x V x O 4 θ J / m o l = 1 − x / 2 Δ f G F e 3 O 4 θ + x / 2 Δ f G F e V 2 O 4 θ + 1 − x / 2 R T l n 1 − x / 2 + x / 2 R T l n x / 2   −   168627.48 1 − x / 2 x / 2 . [ABSTRACT FROM AUTHOR]

Spontaneous emulsification phenomena at 1873 K for the interfacial reaction between high-Al steel and CaO–SiO2 flux was reevaluated. A mild spontaneous emulsification phenomenon was observed, which intensifies with the increase of Al content. The Al mass transfer in alloy along with the Al2O3 mass transfer in slag was assumed to control the global reaction, which was validated by fitting results. The mass transfer coefficient of Al2O3 in slag, k (Al 2 O 3) , was determined to be 2.73 × 10–6. [ABSTRACT FROM AUTHOR]