Dual Effects of LiF on Enhancing the Synthesis and Electrochemical Stability of Amorphous Nano/Micro Ce2Mg17/Ni Composite Electrodes

Abstract

Amorphous nano/microstructured rare earth (RE)-Mg-based alloys exhibit outstanding hydrogen storage capacity and charge–discharge kinetics. However, precisely controlling the composition to ensure the formation of a uniform microstructure with finely dispersed amorphous or nano/micro phases remains challenging. Simultaneously, the rapid corrosion of nano- and microsized Mg particles in an alkali solution reduces the battery lifespan. Therefore, a LiF catalyst was used to enhance the corrosion resistance of the electrode alloy. Subsequently, a simulation calculation was performed based on the extended Miedema thermodynamic theory. The calculation results show that to ensure ΔH_amor ≤ 0 for amorphous enthalpy, the enthalpy difference between the amorphous and solid states |ΔH_sol^m – ΔH_amor| ≤ 5 is essential for the successful formation of amorphous phases. Moreover, the optimal ranges for Li concentration and corresponding enthalpy differences were determined as 3–5 wt % and −4.55 and −4.41 kJ/mol, respectively. Based on the simulation results, Ce₂Mg₁₇/Ni (1:1) + x wt % LiF (x = 0, 1, 3, 5, and 10) composite electrode materials were prepared through mechanical ball-milling, with the results revealing that the Ce₂Mg₁₇/Ni (1:1) composite material with 3 wt % LiF exhibits the best discharge capacity (526.22 mAh·g^–1). The microstructural observation results indicated that LiF effectively inhibited the propagation of cracks along the grain boundaries. These experimental findings were consistent with our theoretical predictions. Hence, the findings of this study may serve as a reference for future development of novel Ce–Mg-based electrode alloys.