The processing of ceramic solid-state electrolytes (SSEs) is a big challenge for solid-state battery (SSB) application. First, densification of garnet-type SSEs (i.e., Li7La3Zr2O12) requires high initial packing density and high sintering temperature, but Li loss at high temperature introduces pores and the formation of non-conductive La2Zr2O7 phase. Second, the high-energy-density promise of SSBs requires the SSE separator to be as thin as the commercial Celgard separator, while the brittleness of LLZO thin film places another obstacle for its scalable fabrication. Last but not least, the intimate solid-solid contact between garnet SSEs and cathodes is difficult to achieve without thermally induced chemical reactions. In this talk, I will present an advanced laser sintering approach to address the above manufacturing issues. We observe that laser sintering accelerates the densification of LLZO, leading to much higher density than furnace sintering even if starting from low-packing-density green films. The directional shrinkage along film thickness direction also differentiates it from other known sintering methods. Dense films as thin as 10 mm can be obtained using fast scanning of focused laser beam on a porous LLZO film, leading to the formation of a dense/porous bilayer structure. The ultrafast laser heating/cooling capability also provide opportunities for the co-sintering of SSEs with cathodes to achieve intimate contact while mitigating chemical reactions.

Laser sintering of solid-state electrolytes

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