Battery Separator Solutions for Li-ion Applications

One of the most critically important cell components to ensure cell safety is the separator, a thin porous membrane that physically separates the anode and cathode. The primary function of the separator is to prevent physical contact between the anode and cathode, while facilitating ion transport in the cell. The challenge with designing safe battery separators is the trade-off between mechanical robustness and porosity/transport properties.


Separators in most batteries are made of very simple plastic films that have the right pore size to allow ions to flow through while keeping the other components blocked. Designed to address the needs of lithium-ion cell manufacturers, Targray Polypropylene (PP), Polyethylene (PE), and ceramic-embedded battery separators deliver excellent porosity, as well as low cost, lightness and durability.

The Role of the Separator in Li-ion Battery Technology

targray-battery-separator-materialsDuring the charging cycle, the positively charged lithium ions move from the cathode, through the separator, to the anode. During discharge, the positively-chargedĀ  ions move from the anode, through the battery separators, to the cathode while the electrons move through the external load from the anode to the cathode, resulting in the current that provides power to the load. The lithium ions move through the separator material via an electrolyte solution.

Battery Separator Characteristics

Requirements for battery separators vary depending on the battery grade application. Manufacturers of Lithium ion batteries using organic electrolytes should use micro-porous films as separators, as this will yield best results for performance, safety and costs. Factors to selecting the right separator are 1:

  • Good electronic insulation with minimal electrolyte (ionic) resistance.
  • Sufficient physical strength to allow easy handling; mechanical and dimensional stability.
  • Chemical resistance to degradation by electrolyte, impurities, and electrode reactants and products
  • Effective in preventing migration of particles or colloidal or soluble species between the two electrodes
  • Readily wettable by electrolyte; Uniform thickness.

1 Battery Separators, Chem. Rev 2001, 104, 4419-4462, Pankaj Arora and Zhengming (John) Zhang.

Requirements for Battery Manufacturing

Battery separators are power-driven spacers that can be produced with fiberglass cloth or flexible plastic films made from nylon, polyethylene or polypropylene. The battery separator material must be absorbent and slim to allow the charged lithium ions to pass without obstruction, while occupying the least amount of space possible. Furthermore, battery separators must be able to withstand penetration and branching moss-like crystalline minerals in order to prevent the contamination of electrodes. If the separator material is compromised, the performance of the high-power cell declines.

Process PE / PP Single or Double Layer Dry Method
Pros Uniformity in thickness
Strong chemical resistance
High wet ability, high EL absorption
High MD tensile strength
Thermal shutdown easy control (PE)
Low cost (PE)
Environmental friendly process
Low contamination in product
Thicker separator possible
Competitive quotation
Flexibility tailor-made products
Cons Lower TD tensile strength (PE)
Lower puncture rate (PE)

Working with supply partners and organizations including the Electrochemical Society and NAATBatt International, we help lithium-ion battery manufacturers and researchers worldwide commercialize ambitious new energy storage technologies.

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