Thin Film Batteries

The battery, a device whose origins date back to the time of Franklin and Volta in the late 1700’s to early 1800’s has been an essential contributor to the progress of modern technology. There have been a wide range of different battery chemistries and configurations over the years ranging from the simple electrochemical cell of Volta with Cu and Zn electrodes separated by a brine solution, to the modern thin film battery with complex lithium-oxide cathodes, solid electrolytes, and graphite anodes.

Basic Battery Schematic

The leading technological battery platform is undoubtedly the lithium-ion (Li-ion) battery. Li-ion technology has high energy density (~250 Wh/kg) [1] and lower memory effects [2] compared to other battery chemistries. With the advent of new, more complicated, and subsequently more power hungry technologies the requirement for safe, lightweight, and long lasting batteries has increased dramatically. Thus, the Li-ion battery market is projected to increase beyond 50 billion dollars (USD) in the next 10 years. In particular, the market for thin film batteries is being driven by demand for technologies based on the internet of things (IoT), wearables, and portable electronics.

Thin Film Battery Construction

The layers that comprise the anode, cathode, and electrolyte in thin film batteries are true to their name, with thicknesses on the order of microns (0.001 mm). They are often deposited using physical vapor deposition, typically by thermal evaporation and sputtering.

thin film battery schematic

Lithium based thin film battery schematic

As the demands for safety, higher energy density, and other performance metrics increase, research into anode, cathode, and electrolyte materials has been rapidly progressing. Cathode materials are often complex lithium-oxides such as LiCoO2, LiMn2O4, and LiFePO4. Anode materials are typically comprised of carbon based materials such as graphite, Li metal, or other metallic materials.

Both the cathode and anode materials are layered structures, chosen for their ability to intercalate and de-intercalate lithium while maintaining their structural integrity. The electrolyte, which in thin film batteries is solid, are made from lithium phosphorus oxynitride (LiPON), although current research is trending towards ceramics such as lithium lanthanum zinc oxide (LLZO) and lithium lanthanum titanium oxide (LLTO). The optimal electrolyte should be an efficient ion-conductor and a good electrical insulator allowing the battery to safely operate. The optimal combination of these materials can yield a battery that is light, thin, long lasting, and safe.

Angstrom Engineering Battery Deposition Systems

This full featured system was custom created for a partner and integrates dedicated lithium thermal evaporation, lithium-oxide multi-source sputtering, and rapid thermal processing into an ultra-high purity argon environment to provide ideal process flexibility, ease of materials handling, and safety.

Our deposition systems can deposit the full range of battery materials from the thermal evaporation of lithium, to sputtering of ceramics and lithium-oxides. Due to the sensitive nature of these films, our tools can easily be integrated with glove-boxes so substrate and material handling can be done under inert atmospheres. Speaking with one of our experienced process engineers is the best way to decide exactly how to approach your unique process requirements. We would love to hear from you.

References
[1] Panasonic NCR18650b, https://na.industrial.panasonic.com/sites/default/pidsa/files/ncr18650b.pdf
[2] Tsuyoshi Sasaki, Yoshio Ukyo, Petr Novák, Nature Materials 12, 569–575 (2013)

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