Breaking Energy Density‐Stress Trade‐Off in Anode‐Free Lithium Pouch Cells

ABSTRACT The swelling of the Li metal anode and its adverse impacts have barred lithium metal batteries (LMBs) from practical applications. Owing to insufficient recognition of the energy density–stress trade‐off, no viable solution has emerged to halt their expansion or diminish their internal stress accumulation (SA) while preserving their exceptional energy density. We proposed principle‐based criteria to guide the development of high‐energy and low‐swelling LMBs by defining the boundary parameters of strain‐buffering techniques. Taking a typical space‐adaptive buffering (SAB) layer as an example, we have materialized this criterion and verified its scientific validity and forward‐looking nature, effectively reducing SA and mitigating the local stress concentration (SC). As a result, the Ah‐level NCM9 (LiNi x Co y Mn 1‐x‐y O 2 , x ≥ 0.9)||SAB‐Cu pouch cell prototype with the high bare‐cell energy densities of 465 Wh/kg and 1330 Wh/L exhibits the uniform stress distribution and low SC (extreme difference in local pressure<2 MPa), avoiding the failure of Li dendrite puncture. Furthermore, the Ah‐level NCM811(Li 1.2 Ni 0.8 Co 0.1 Mn 0.1 O 2 )||SAB‐Cu pouch cell demonstrates a perfect trade‐off among energy densities (418 Wh/kg and 1061 Wh/L), cycle life (164 cycles with 77% capacity retention), SA (<2 MPa), and swelling ratio (3.6%), underscoring the practical feasibility of the SAB‐AF‐LMB.