Material interfaces are a key research area in solid-state batteries. The interface between the electrode and the solid electrolyte causes significant electrical resistance, the source of which is not fully understood. When the electrode surface is exposed to air, resistance increases, reducing battery capacity and performance. Despite multiple attempts to lower the resistance, I was unable to get it down to the same 10 Ω cm2 as when not exposed to air. Tests showed that the decrease in resistance was due to the spontaneous removal of protons during the annealing process, rather than oxygen or nitrogen reducing cell performance. After one hour of thermal annealing at 150°C, the resistance dropped to 10.3 Ωcm2, which is comparable to cells not exposed to air.
A major battery manufacturer has adopted a new lithium metal pouch battery design that emphasizes the importance of interfaces. The battery uses a silver-carbon (Ag-C) nanocomposite layer on the lithium metal negative electrode to prevent the growth of lithium dendrites and provide greater capacity, longer cycle life and higher safety. Although the battery combines a high-nickel layered aluminum oxide cathode and a solid sulfide electrolyte, the key is to use a hot isostatic pressing technique to improve the contact between the electrode and the electrolyte. This design allows the battery to be half the size of a lithium-ion battery while supporting a lifespan of more than 1,000 charge cycles.