Thin Film Batteries: What They Are and How They’re Made

Technological advancements have allowed makers to design and build devices that are both smaller and more powerful than ever before. These advancements have fueled a need for increasingly small and powerful batteries. Today, the most popular battery platform is the lithium-ion battery — but the future lies in the potential of thin film batteries.

What is a Thin Film Battery?

Thin film batteries are created by stacking thin layers of battery components (cathode and anode current collectors) together on a substrate. These layers, which are as small as 5 microns in size, are deposited using magnetron sputtering and thermal evaporation. The result is an extremely compact and efficient battery that is less than a millimeter thick.

Why Use Thin Film Batteries?

Thin film batteries have many advantages over traditional rechargeable batteries.

  • Safety: because thin film batteries contain solid state materials and an inorganic glass electrolyte, there is no risk of spilling, boiling or gassing.
  • Temperature resistance: traditional batteries are prone to failure and significantly reduced capacity at temperatures exceeding 60° Celsius, but thin film batteries have stability at temperatures ranging from as low as -40° to as high as 150°, making them useful for devices such as high temperature sensors.
  • Longevity: thin film batteries have been cycled over 45,000 times with little to no loss of capacity, while thicker batteries have a far lower cycle capacity (often less than 2,000)
  • Cost savings: owing to their small size, thin film batteries will become less costly to produce once the technology has been refined and widely adopted.
  • Performance: the more researchers explore the possibilities of thin film batteries, the better performing they become. Today, high-performance thin film batteries have an impressive power rate capability.

How Are Thin Film Batteries Made?

The components in a thin film battery are placed using two deposition technologies called magnetron sputtering and thermal evaporation.

  • Thermal evaporation: a physical vapour deposition technique where a material is placed in a high-vacuum chamber and heated to its evaporation point, forcing molecules to dislodge and travel to the surface of an object. There, the molecules nucleate together to form a thin coating.
  • Magnetron sputtering: involves generating a gaseous plasma in a sealed, high-vacuum chamber in order to deposit metal molecules onto the surface of an object. The environment inside the chamber causes metal ions to dislodge from the source and travel onto the object, coating it with a thin layer of metal.

These techniques are performed using highly advanced machinery that is usually operated by a trained engineer. Click here for further information about sputtering and evaporation systems.