Assembly of an Elastic & Sticky Interfacial Layer for Sulfide-Based All-Solid-State Batteries

All-solid-state lithium-ion batteries (ASSLBs) have recently attracted significant attention, however, two major degradation processes at the composite cathode interface in ASSLBs, including side electro-chemical reactions and morphological/structural degradation, still hinder their development seriously. To overcome the above two challenges simultaneously, we propose and demonstrate a successful assembly of an elastic & sticky interfacial layer for ASSLBs by using advanced molecular layer deposition (MLD) technique. Our spectroscopic and mechanical characterization results show that the elastic and sticky Al-GL coating layer (Young’s modulus = 0.17GPa, k = 3.300 N m-1) not only suppresses interfacial side reactions, but also enables single-crystal NCM811 particles to be in close contact with the sulfide electrolyte tightly during repeated cycles. Compared to the irreversible interfacial resistance (51.74 Ω cm-2) formed between bare NCM811 and solid electrolyte during the initial charge progress, the irreversible resistance becomes much less (11.77 Ω cm-2) after Al-GL modification. Therefore, it not only shows a capacity retention of 88.0 % of the composite electrode, which is nearly 30 % higher than bare NCM811 (59.9 %) for 100 cycles at 0.2C (1C =180 mA g-1) with a mass loading of 10.2 mg cm-2 at 30 °C. Furthermore, even with a mass loading of 20.4 mg cm-2 at 60 °C, the capacity retention of 80.0 % is obtained after 1000 cycles at 1C. This work highlights the critical role of elastic and sticky coatings in maintaining the electrochemical-mechanical integrity of composite cathode materials and provides a promising avenue for developing mechanically reliable cathode materials for ASSLBs.