Electrochemical performance of high-hardness high-Mg aluminum alloy foils as negative electrodes for lithium-ion batteries

초록

The present study investigates high-magnesium-concentration (5-10 wt%) aluminum-magnesium (Al-Mg) alloy foils as negative electrodes for lithium-ion batteries, providing a systematic exploration of the role of Mg solutes in enhancing the mechanical and electrochemical properties of Al-based anodes. The addition of Mg lowers the lithiation voltage and nucleation overpotential, while increasing charge transfer resistance and diffusion resistance. Through solid-solution strengthening and precipitation hardening, Mg addition significantly improves the structural stability of aluminum anode foils during electrochemical cycling. A correlation is observed between increased hardness and enhanced electrochemical performance, characterized by an extended cycle life, improved capacity retention, and higher Coulombic efficiency. A distinct two-stage voltage plateau develops in Al-Mg alloys-a feature absent in pure Al-that becomes more pronounced with increasing Mg concentration. This phenomenon is attributed to the formation of an intermediate Al3Li phase during lithiation. The formation of the Al3Li phase prior to the equilibrium phase of beta-LiAl is expected to effectively mitigate abrupt volume changes and the resulting high mechanical stresses, thereby providing an additional benefit of Mg incorporation in enhancing the anode performance of Al-based electrodes. Among the tested Al-Mg alloy samples, the aged Al10Mg alloy, which exhibits the highest hardness and retains a high concentration of Mg in the matrix, demonstrates the best electrochemical performance.

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