Modulation of Prelithiation Solution for Hard Carbon Anodes of Lithium-Ion Batteries

Abstract

The increasing demand for high-energy and high-power lithium-ion batteries (LIBs) in portable gadgets and electric vehicles has led to exploration of high-performance silicon and hard carbon (HC) anodes to replace traditional graphite anodes. However, their practical application is hindered by low initial coulombic efficiency and large irreversible capacity, which decreases the total energy density. Prelithiation is a strategy to restore energy density by supplying additional Li ions. Chemical prelithiation, involving immersing the electrode in a reductive Li−aromatic hydrocarbon (arene) complex solution, is a standout method due to its safety, high efficiency, and practical feasibility. It not only restores the lost lithium but also aids in maintaining a more stable solid electrolyte interphase layer to guarantee battery cycling stability. The first part of our study addresses the issue of expensive and impractical arene complexes for prelithiation, we focus on using low-cost and commercially available aromatic compounds such as naphthalene and methyl-substituted naphthalene compounds. This study investigates the effects of electron-donating methyl groups on naphthalene on the prelithiation activity toward HC using density functional theory calculations. In the second part of this study, we use low-cost and easily available solvents such as ethylene glycol dimethyl ether, bis(2-methoxyethyl) ether, and triethylene glycol dimethyl ether for chemical prelithiation. Ether solvents have a desirable solvation effect with Li+, and the ether with low solvation power enhances the prelithiation activity. The degree of prelithiation is greatly affected by the reaction time, and the details of this relationship are rarely investigated. In the final part of our study, we conduct a detailed investigation on the effects of various reaction times on the prelithiation activity toward the HC anode. This study provides useful insights for effective prelithiation, in terms of choosing aromatic compounds, solvents, and reaction time.