Silicon-based all-solid-state batteries operating free from external pressure

Silicon-based all-solid-state batteries offer high energy density and safety but face significant application challenges due to the requirement of high external pressure. In this study, a Li₂₁Si₅/Si-Li₂₁Si₅ double-layered anode is developed for all-solid-state batteries operating free from external pressure. Under the cold-pressed sintering of Li₂₁Si₅ alloys, the anode forms a top layer (Li₂₁Si₅ layer) with mixed ionic/electronic conduction and a bottom layer (Si-Li₂₁Si₅ layer) containing a three-dimensional continuous conductive network. The resultant uniform electric field at the anode|SSE interface eliminates the need for high external pressure and simultaneously enables a twofold enhancement of the lithium-ion flux at the anode interface. Such an efficient ionic/electronic transport system also facilitates the uniform release of cycling expansion stresses from the Si particles and stabilizes bulk-phase and interfacial structure of anode. Consequently, the Li₂₁Si₅/Si-Li₂₁Si₅ anode exhibited a critical current density of 10 mA cm^-2 at 45 °C with a capacity of 10 mAh cm^-2. And the Li₂₁Si₅/Si-Li₂₁Si₅|Li₆PS₅Cl|Li₃InCl₆|LCO cell achieve an high initial Coulombic efficiency of (97 ± 0.7)% with areal capacity of 2.8 mAh cm^-2 at 0.25 mA cm^-2, as well as a low expansion rate of 14.5% after 1000 cycles at 2.5 mA cm^-2.