How does a lithium ion conducting nanoscale film made by ALD manage to stabilize the performance of future generations of all-solid state batteries? »

All Solid State Batteries (ASSBs), which are based on the use of solid electrolytes (SEs) with high ionic conductivity, are the Holy Grail of future battery technology, as they could increase both energy density and safety. However, the practical application of ASSBs is still hampered by difficulties in controlling the interfaces between the solid electrolyte and the electrodes. Halide-based lithium ion conductors show promise but are not stable against negative Li or LixIny electrodes, hence the need to assemble ASSBs with a dual solid electrolyte design. In a collaborative work between the Collège de France (Chaire du Solide et de L’énergie, Pr Jean-Marie Tarascon) and the IEMN (CSAM Group, Pr Christophe Lethien), a new strategy has been implemented to fight against the chemical incompatibility between two solid electrolytes within an ASSB. It consists in depositing a protective layer of nanometric thickness (from 1 to 2 nm) of Li3PO4 realized by Atomic Layer Deposition (ALD) between two solid electrolytes (Li3InCl6 and Li6PS5Cl). Thanks to this surface engineering process with highly conformal nanoscale films, ASSBs showing a dramatic retention of capacity over 400 cycles have been successfully assembled.