A Conduction‐Nucleation‐Competition‐Guided 3D Adaptive Gradient Buffer for Dendrite‐Free All‐Solid‐State Lithium Metal Batteries

ABSTRACT

The existing designs of buffer for all‐solid‐state Li‐metal batteries (ASSLMBs) are mostly limited to static optimization of single functions and lack systematic regulation of the dynamic competition among ionic conduction, electron distribution, and interfacial lithiophilicity. Herein, a conduction‐nucleation competition mechanism is proposed firstly, clarifying that lithium deposition is governed by the synergy of these three factors. Guided by this principle, a self‐adaptive gradient buffer layer composed of soft carbon and Mg ₃ N ₂ (SCMN) is designed. After lithiation, the buffer forms a continuous lithiophobic/lithiophilic gradient and subsequently undergoes in‐situ conversion into highly ion‐conductive Li ₃ N and highly electron‐conductive/ lithiophilic Li‐C/Li‐Mg alloys during electrochemical activation, enabling dynamic interface self‐optimization. The gradient structure creates a fast ion–electron dual conduction network, guiding bottom‐top lithium deposition within the buffer layer without volume expansion. Consequently, the symmetric cells achieve stable cycling over 1600 h at 1.5 mA cm ^{− 2} and remain stable even under low stack pressure (15 MPa). The LiCoO ₂ ‐based full cells deliver ultra‐stable cycle with 98.5% capacity retention after 200 cycles at 0.1 C. Additionally, the full cells paired with high‐voltage LiNi _0.8 Co _0.1 Mn _0.1 O ₂ cathodes exhibit exceptional cycling stability at high loading (4.45 mg cm ⁻² ). This work demonstrates a mechanism‐driven design paradigm toward high‐energy, long‐life ASSLMBs.