Molecular sieves are highly popular in battery electrolyte dehydration via physical adsorption. This technique eliminates the adverse impacts of moisture, optimizes the overall performance of lithium-ion batteries, and enhances their safety, thus gaining widespread research attention in recent years.
Constituents Of Common Lithium Electrolytes
- Organic solvents serve as the primary component of lithium battery electrolytes, making up 80% to 90% of the total electrolyte mass. Common types include ethylene carbonate (EC), dimethyl carbonate (DMC), propylene carbonate (PC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC).
- Lithium salts act as another essential electrolyte component and provide the core lithium source for battery operation. Typical lithium salts adopted in commercial and research batteries cover lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium tetrafluoroborate (LiBF₄), and lithium perchlorate (LiClO₄).
- Additives constitute approximately 5% of the electrolyte system, mainly including film-forming agents, flame retardants, and stabilizers. Vinyl carbonate (VC) and fluorinated vinyl carbonate (FEC) are the most widely used film-forming additives in lithium battery electrolytes.
Impacts Of Water Presence In Battery Electrolytes
- Electrolyte components are highly susceptible to moisture and impurities, which severely undermines the manufacturing process and final quality of lithium-ion batteries. The specific adverse effects are as follows:
- Moisture also destroys the integrity and uniformity of the solid electrolyte interface (SEI) film formed by film-forming additives. A defective SEI film increases battery internal resistance and reduces discharge capacity.
- In the charge and discharge cycles, water decomposes into gases such as carbon dioxide (CO₂) and hydrogen (H₂). The accumulated gas raises internal battery pressure, which further causes battery bulging, liquid leakage, and even extreme safety accidents like smoking, combustion and explosion.
The hazards of water mentioned in solvent treating also exist in the electrolyte. In short, water contaminants impair electrolyte conductivity, weaken interface stability, and shorten battery cycle life while creating major safety risks. Moisture control is therefore a critical step throughout lithium battery production and application.
Molecular Sieves For Electrolyte Dehydration
The applications of molecular sieves in electrolytes vary depending on their specific purposes, such as solvent drying, electrolyte dehydration and deacidification, electrolyte regeneration, and enhancement of electrochemical performance.
