Enabling High‐Energy Solid‐State Batteries with Stable Anode Interphase by the Use of Columnar Silicon Anodes

All‐solid‐state batteries (ASSBs) with silicon anodes are promising candidates to overcome energy limitations of conventional lithium‐ion batteries. However, silicon undergoes severe volume changes during cycling leading to rapid degradation. In this study, a columnar silicon anode (col‐Si) fabricated by a scalable physical vapor deposition process (PVD) is integrated in all‐solid‐state batteries based on argyrodite‐type electrolyte (Li6PS5Cl, 3 mS cm−1) and Ni‐rich layered oxide cathodes (LiNi0.9Co0.05Mn0.05O2, NCM) with a high specific capacity (210 mAh g−1). The column structure exhibits a 1D breathing mechanism similar to lithium, which preserves the interface toward the electrolyte. Stable cycling is demonstrated for more than 100 cycles with a high coulombic efficiency (CE) of 99.7–99.9% in full cells with industrially relevant areal loadings of 3.5 mAh cm−2, which is the highest value reported so far for ASSB full cells with silicon anodes. Impedance spectroscopy revealed that anode resistance is drastically reduced after first lithiation, which allows high charging currents of 0.9 mA cm−2 at room temperature without the occurrence of dendrites and short circuits. Finally, in‐operando monitoring of pouch cells gave valuable insights into the breathing behavior of the solid‐state cell. Columnar silicon anodes of 3.5 mAh cm−2 combined with Ni‐rich cathodes for room temperature solid‐state full cells are reported. The new cell design exhibits capacity retention of 82% after 100 cycles and no short circuits for 350 cycles at moderate current densities. An external pressure device employs monitoring in situ breathing behavior and recovers volume changes of the silicon anodes.