Breaking Lithium Embrittlement in Alloy Anodes Enables Low‐Stack‐Pressure All‐Solid‐State Batteries

Alloy anodes (Si, Al, In, and Sn) are exceptionally promising for realizing dendrite‐free, high‐energy‐density all‐solid‐state lithium‐ion batteries (ASSLIBs). However, even soft metals such as Al, Sn, and In form hard and brittle lithiated intermetallics upon lithiation, requiring commercially impractical stack pressures during operation. Here, we overcome limited dislocation slip in lithiated intermetallics arising from directional covalent bonding by introducing a nanoscale amorphous structure during lithiation. This mitigates the high hardness and brittleness of lithiated alloys, reducing the required stack pressure for alloy anodes from ≥30 to ≤5 MPa. The results reveal that atomically mixed In and Sn generate abundant nanoscale amorphous structures during lithiation, as mutual lattice disruption suppresses long‐range crystallization. This amorphization facilitates inter‐unit sliding and mitigates the effects of directional covalent bonding in intermetallics, thereby reducing their inherent hardness and brittleness. Consequently, the NMC83|LPSCl|(InSn 4 ) 0.64 ·(In 3 Sn) 0.36 cell (cathode areal loading: 22.37 mg cm −2 ) delivers 84.3% capacity retention over 2000 cycles at 4.0 C. After incorporating (InSn 4 ) 0.64 (In 3 Sn) 0.36 composite into Si anode, the NMC83||Si full cell sustains over 400 cycles at 5 MPa and is further validated in pouch cells. This strategy of breaking lithium embrittlement can also be extended to other alloy anodes (Al–, Sb–, and Bi–containing alloy) in ASSLIBs.