Push-Pull Electrolyte Design Strategy Enables High-Voltage Low-Temperature Lithium Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium (Li) metal batteries offer high energy density but suffer from poor low-temperature performance due to slow charge transport and unstable interphases.
• Conventional electrolytes hinder lithium-ion desolvation and promote solvent decomposition at low temperatures.
• Existing solvation structures in electrolytes impede efficient lithium-ion transport at ultralow temperatures.

Purpose of the Study:

• To design a novel electrolyte system for enhanced lithium metal battery performance at ultralow temperatures.
• To investigate the role of molecular electrostatic potential (ESP) in designing optimal electrolyte cosolvents.
• To improve charge transport kinetics and interphase stability in lithium metal batteries operating at -40 °C.

Main Methods:

• Utilized molecular electrostatic potential (ESP) screening to identify 2,2-difluoroethyl trifluoromethanesulfonate (DTF) as an optimal cosolvent.
• Designed a 'push-pull' electrolyte strategy leveraging DTF's unique electronic properties.
• Tested LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811)||Li cells with the designed electrolyte at -40 °C.

Main Results:

• The DTF cosolvent balanced Li ion affinity, facilitating desolvation and reconstructing solvation structures.
• The designed electrolyte enabled rapid charge transfer kinetics and formed robust, inorganic-rich interphases.
• NMC811||Li cells achieved stable cycling at -40 °C, delivering >153 mAh g^-1 capacity and retaining >93% after 100 cycles at 4.8 V.

Conclusions:

• The push-pull electrolyte design strategy effectively enhances low-temperature performance of lithium metal batteries.
• DTF as a cosolvent promotes efficient Li ion desolvation and stable interphase formation.
• This research advances the development of electrolytes for batteries operating under extreme temperature conditions.