Chemistry: Electrolyte & Separator

Battery Separator Types And Technologies Lithium-ion battery separators physically separate the positive and negative electrodes while allowing the transport of lithium ions. The most commonly used lithium-ion battery separators are typically made of polyolefin materials (typically PE or PP) coated with ceramic. There are many other different types of separators used in lithium-ion batteries with different performance traits and trade offs., and are broadly categorized below. Separator Type

Material

Characteristics

Polyolefin

Polyethylene PE) and/or polypropylene PP

Polyolefin separators are widely used due to their cost-effectiveness, chemical stability, and ease of manufacturing. They are commonly found in commercial lithium-ion batteries

Ceramic-Coated

Polyethylene or polypropylene separators with a ceramic coating

Ceramic-coated separators provide enhanced thermal stability and safety. The ceramic layer helps prevent thermal runaway by inhibiting the growth of internal shorts and dendrites

Composite

Combination of different polymers, ceramics, or other materials

Composite separators leverage the strengths of multiple materials to achieve a balance of properties, mainly to add electrochemical stability, prevent shorts, and inhibit growth of lithium dendrites.

Microporous

Often composed of polyethylene or polypropylene with added fillers or ceramic coatings

Microporous separators have a porous structure, allowing for efficient ion transport while maintaining good mechanical strength. The addition of fillers or ceramic coatings can enhance thermal stability and reduce the risk of thermal runaway

Glass Fiber

Glass fibers combined with a polymer matrix

Glass fiber separators offer good mechanical strength and can be used in high-temperature applications. They are known for their resistance to puncture and excellent thermal stability

Nonwoven Fabric

Nonwoven materials made of synthetic fibers

Nonwoven fabric separators provide good mechanical strength and are often used in flexible and lightweight battery designs. They can offer flexibility and conformability to different battery shapes

Composite Membrane

Combination of polymer and ceramic materials

Composite membrane separators aim to provide a balance between mechanical strength, thermal stability, and ion conductivity. They are designed to enhance safety and performance in lithium-ion batteries

Sources: Celgard, Sepion, Review on Lithium-Ion Battery Separators, 24M, Battery Report 2023 (pg 132)

Extracted from the PDF; charts and images may read imperfectly.