1. Electrolyte Composition
Electrolyte is a critical raw material in lithium batteries. It serves as the ionic conductor between the cathode and anode, enabling efficient charge transfer.
A typical electrolyte consists of high-purity organic solvents, lithium salts, and functional additives in carefully controlled proportions. Its quality directly affects energy density, power performance, cycle life, safety, and temperature stability.
Organic Solvents
Their primary role is to dissolve lithium salts. Common solvents include Ethylene Carbonate (EC), Diethyl Carbonate (DEC), Dimethyl Carbonate (DMC), Ethyl Methyl Carbonate (EMC), Propylene Carbonate (PC), and Dimethoxyethane (DME).
These solvents provide a stable chemical environment for lithium-ion transport. Moisture content is typically required to be below 20 ppm or even lower.
Lithium Salts
Such as LiPF₆, LiFSI, and LiBF₄. These salts provide mobile lithium ions and enable ionic conductivity.
Additives
Used to improve electrolyte stability, suppress side reactions, enhance safety, promote SEI (Solid Electrolyte Interphase) formation, and extend battery life.
Film-forming additives like VC and FEC also require strict dehydration during synthesis and purification.
Among various dehydration technologies (distillation, membrane separation, chemical drying agents), molecular sieve adsorption has become the preferred solution due to its high selectivity, operational simplicity, reusability, and absence of secondary contamination.
2. Principle of Molecular Sieve Dehydration
Molecular sieves (zeolites) are crystalline aluminosilicates with a uniform microporous structure.
Their dehydration mechanism is based on two key principles:
Selective Adsorption (Size Exclusion)
Only molecules smaller than the pore size can enter and be adsorbed.
Polar Adsorption
Strong electrostatic fields generated by cations within the structure attract polar molecules such as water.
Water molecules have a diameter of approximately 0.28 nm and strong polarity, making them highly adsorbable.
Dehydration Process
Before battery assembly, solvent containing trace moisture passes through a molecular sieve bed:
Water molecules (small size, strong polarity) are selectively adsorbed into the pores
Solvent molecules (larger than 0.45 nm, e.g., DMC ≈ 0.45 nm) pass through without being adsorbed
This enables efficient and selective removal of moisture.
By eliminating trace water, the process prevents the formation of harmful hydrofluoric acid (HF) caused by reactions with lithium salts, significantly improving battery safety and cycle life.
3. Molecular Sieve Selection
Selection Criteria Recommended Option Reason
Type 4A Molecular Sieve (Preferred) Pore size of 0.4 nm allows water (0.28 nm) to enter while blocking solvent molecules (>0.45 nm), preventing solvent loss
Shape Spherical Beads Better flow dynamics, lower pressure drop, minimal dust
Particle Size 1.6–2.5 mm or 3–5 mm Too large → lower surface area; Too small → higher pressure drop and dust generation
4. Product Example: CHEMXIN 4A Molecular Sieve
Property Specification
Static Water Adsorption >22%
Dehydration Performance Reduces moisture from 500 ppm to <20 ppm
Water Resistance Strength No breakage after water exposure (Crush strength >100 N)
Chemical Resistance Excellent resistance to acid and alkali
Anti-Caking Performance Effectively prevents solvent agglomeration
Surface Area Uniform distribution with high adsorption capacity
Conclusion
Molecular sieve dehydration is a highly efficient and reliable solution for removing trace moisture from lithium battery electrolyte solvents. With its precise selectivity, strong adsorption capacity, and reusability, 4A molecular sieve has become the industry standard for ensuring electrolyte purity and enhancing battery performance and
About Chemxin:
Guangzhou Chemxin Environmental Material Co., Ltd. has specialized in the production of molecular sieve, activated molecular sieve powder, activated alumina, and ceramic ball for over 24 years. Our factory covers 50,000 square meters and employs more than 250 staff members, including a dedicated R&D team committed to innovation and quality.
If you have any inquiries or requirements, please feel free to contact us at any time. We are here to provide you with professional solutions and reliable service.
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