Unravelling Polymers

The Definitive Blog on Polymers by Poly Fluoro Ltd.

PTFE Battery Separators - An Essential Insulating Media

The advancement of electronics in our daily lives has accelerated recently with the advent of IOT and electric vehicles. In all these applications, the one feature that is of paramount importance is the battery.

An enhanced battery life and performance appears to be the thing that sets a device apart from its peers. We evaluate our mobile phones and even our electric vehicles on the merit of how far they can go on a single charge. Furthermore, we need the battery life to stay consistent over the lifetime of the product and not dull out after one or two years of operation.

If industry sources are to be believed, the average life of an electric vehicle would be 400,000Km, as against the average of 200,000Km in today’s fuel-powered vehicles. It is suggested that we would not look to replace an electric vehicle (for performance-related factors anyway) for at least 15 years. Obviously, if the battery needs replacement every 2-3 years, this poses a problem. Even if a consumer wishes to trade in their old vehicle for a new one, the resale value of the older vehicle will ride heavily on the battery performance.

In an attempt to look for cheaper, more effective and light-weight solutions to this problem, PTFE has emerged as an ideal medium for insulating the insides of lithium-ion batteries. Battery separators are essential for ensuring that the battery does not discharge internally, reducing the effectiveness of a single charge. They also ensure that while charging, a battery does not accidentally short circuit internally.

PTFE films have several properties that make them ideal for this application:

  1. High dielectric breakdown voltage – the breakdown voltage of PTFE can be as high as 150KV/mm. This means that a thin film of PTFE can perform the insulative function of a much thicker layer of regular insulation
  2. Light-weight – although PTFE has a high density when compared with other polymers (~2.25 g/cm3), it is light when considering that a 40-50 micron film is all that is needed to make an effective medium. In an age when devices are getting more compact, this becomes an even more critical characteristic of the material
  3. Chemically inert – because PTFE does not react with other chemicals (barring molten alkalis at elevated temperatures), it can be used with no concern that it will disintegrate over time
  4. Zero-static discharge – PTFE does not allow any current to pass through or along its surface. This extreme insulative ability ensures that there is no ‘leakage’ of current within the battery, which can cause it to slowly discharge even while idle.
  5. Available in variants – both skived PTFE films and ePTFE Films can be used as separators, depending on whether there is a requirement for porosity or not. Furthermore, PTFE films can also be infused with carbon to give anti-static properties, which may or may not be a requirement depending on the equipment design.

It is a known fact that insulation and electronics go hand in hand. As our dependence on electronic devices grows, so too does our need for stable, cost-effective and efficient insulation. PTFE – due to its incomparable properties as an insulator – should see its demand increase substantially, as more applications will require its unique properties to stay effective.

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