Using a simple stencil printing process followed by ultraviolet cross-linking, researchers have demonstrated a new type of Li-ion batteries.
Researchers in South Korea have developed a new technique that can print batteries on any surface. Today's Li-ion batteries can only be fabricated in fixed shapes and sizes, but these Li-ion batteries created at the Ulsan National Institute of Science and Technology (UNIST) can be printed in their entirety—including electrodes and electrolyte—almost anywhere.
Published in ACS Nano Letters in a paper titled “Printable Solid-State Lithium-Ion Batteries: A New Route toward Shape-Conformable Power Sources with Aesthetic Versatility for Flexible Electronics,” the printable solid state (PRISS) batteries consist of a solid-state composite electrolyte (SCE) layer and SCE matrix-embedded electrodes, which can be printed on just about any object of any shape, as it is possible with today's stencil process.
Figure 1: Stencil printing of a conformable PRISS battery.
The researchers were able to tune the rheological properties of the SCE paste and electrode slurry to give them thixotropic fluid characteristics suitable for complex deposition patterns on non-flat objects. They also had to design a high boiling point electrolyte to make the PRISS batteries compatible with heat curing.
The materials used allowed the researchers to circumvent solvent-drying and liquid-electrolyte injection process steps, while removing the need for conventional microporous separator membranes. This makes the printable batteries truly shape-conformable, opening new design opportunities for better battery integration.
Lead researcher and UNIST professor Sang-Young Lee expects the PRISS batteries to alleviate design constraints in wearable devices, removing the need for a pre-designated battery space with fixed dimension and shape.
One example being shown is the integration of the PRISS batteries directly onto smart glasses frames.
Figure 2: Conventional battery integration (left) versus a conformal approach (right). A square-shaped Li-ion battery on a pair of paper glasses.
What's more, after characterising the electrochemical behaviour of PRISS batteries, the researchers found that these batteries exhibited 90% capacity retention after 30 cycles, with no significant loss in charge or discharge capacities, a capacity retention which beats that of conventional Li-ion batteries.