A Non-Concentrated Gradient-Solvation Electrolyte Enables a High-Voltage Lithium Metal Battery with 447.6 Wh Kg^-1.

Abstract

High-voltage lithium (Li) metal batteries (LMBs) emerge as a pivotal strategy for achieving high energy density applications. However, the electrolyte instability leading to inferior rate performance and short lifespan remains to be addressed. In this study, a new non-concentrated gradient-solvation electrolyte by solvent polarity discrepancy is developed. A highly donor-capable ether forms the Li⁺-solvated core through strong ion-dipole interactions, while a weakly donating carbonate creates the shell structure. Such a gradient-solvation structure enables the electrolyte with a high oxidation voltage (4.6 V vs. Li/Li⁺) and rapid Li⁺-desolvated kinetic. Consequently, the electrolyte facilitates the LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811)||Li cells to attain a specific capacity of 165.8 mAh g^-1 at 5C, alongside 1000 stable cycles at 1C charge/3C discharge with 66% capacity retention. Even under lean conditions (N/P = 1.5, electrolyte: 20 µL), NCM811||Li cell still maintains 97.5% capacity retention over 100 cycles. Furthermore, a 3.2 Ah pouch cell achieves a specific energy density of 447.6 Wh kg^-¹ with stable cycling. These findings highlight the promise of gradient-solvation electrolytes for high-voltage LMBs applications.