Soft meets hard: hybrid solid electrolytes for all-solid-state batteries

A multidisciplinary team from The Universities of Edinburgh and Oxford has demonstrated that hybrid ceramic-polymer electrolytes can have superior mechanical properties without significantly compromising ionic conductivity, thereby addressing one of the key challenges for all-solid-state batteries.

Batteries with a lithium-metal electrode promise a step-change in energy content per unit volume, making them interesting for application in electric vehicles. However, there are many challenges to overcome. One such challenge is the electrolyte, which is typically volatile and flammable, posing safety and longevity challenges. One solution is to create an all-solid-state battery by replacing the liquid electrolyte with a non-flammable solid electrolyte. Solid ceramic electrolytes have been shown to have sufficiently high ionic conductivity, but they are mechanically brittle.

The researchers used 3D printing techniques to create hybrid solid electrolytes consisting of 3D bicontinuous ceramic and polymer microchannels. The basic idea is that the continuous ceramic channel provides high ionic conductivity, whereas the continuous polymer channel renders the hybrid electrolyte mechanically robust. 3D printing allowed for precise control over the microarchitecture, as demonstrated by the four 3D structures considered: cubic, diamond, gyroidal and spinodal (bijel) structures. The results suggest that the bicontinuous gyroid structure provides the best properties, outperforming a (conventional) dense ceramic disk during charge/discharge cycling in contact with lithium metal electrodes.

This new design concept for solid electrolytes "may offer a way forward in the quest for an all-solid-state battery" and demonstrates that soft materials have something interesting to offer in energy applications.