Deciphering Solid‐State Battery Interface Failure: Plasma‐Assisted Bulk‐Interface Lithium Diffusion Kinetics Regulation

Abstract Interfacial‐contact failure and void‐evolution in garnet‐based solid‐state lithium‐metal batteries (SSLMBs), caused by inadequate initial interface‐bonding and limited lithium‐ion diffusion at the anode, represent critical bottlenecks that need to be addressed to achieve the practical viability of SSLMBs. Here, a plasma‐assisted dual‐strategy is presented that integrates radio‐frequency plasma‐magnetron‐sputtering (RF‐PMS) and dielectric‐barrier‐discharge (DBD) plasma‐treatment to construct an outstanding interface structure. Specifically, the composite‐lithium‐anode (CLA) doped with DBD plasma‐functionalized carbon‐nanotubes (D‐CNT) is coated onto an AlF 3 ‐modified Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (AF‐LLZTO) solid electrolyte synthesized using RF‐PMS. The engineered LC10|AF‐LLZTO interface (LC10: optimized CLA containing 10 wt.% D‐CNT) facilitates a stable lithium‐ion diffusion pathway, effectively mitigating interfacial‐contact degradation. Following delithiation to 3.0 mAh cm −2 , this configuration retains 85.16% interfacial‐contact integrity—significantly surpassing the mere 10.49% retention observed in unmodified lithium‐anodes. The enhanced interfacial‐stability of this structure can be directly visualized through in situ optical‐microscopy observation. The symmetric cell LC10|AF‐LLZTO‐AF|LC10 achieves 10000 h of stable cycling at 0.2 mA cm −2 , significantly outperforming the symmetric cells Li|AF‐LLZTO‐AF|Li without CLA (1930 h) and LC10|LLZTO|LC10 without AlF 3 (<900 h). Furthermore, a full cell LC10|AF‐LLZTO‐IL|NCM811 utilizing a LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathode demonstrated ultra‐long cycling stability, achieving a maximum of 2000 cycles at 1 C and exhibiting a single‐cycle capacity degradation of ≈0.0125%.