Cryo‐EM Studies of Atomic‐Scale Structures of Interfaces in Garnet‐Type Electrolyte Based Solid‐State Batteries

Abstract High interfacial impedance is a major obstacle in the application of solid‐state Li metal batteries (SSLMBs). Understanding the atomic‐scale structure of the interfaces in SSLMBs is thus critical to their practical implementations. However, due to the beam sensitivity of battery materials, such information is not accessible by conventional electron microscopy (EM). Herein, by using cryogenic‐EM (cryo‐EM), the atomic‐scale structures of interfaces in garnet electrolyte based SSLMBs are revealed. A LiF‐rich interlayer exhibiting intimate contacts with both Li and LLZTO is shown, thus rendering uniform Li + transport across the interface in turn inhibiting Li dendrite growth. Consequently, the Li symmetric cell based on the LiF‐rich interlayer exhibits a high critical current density of 3.2 mA cm −2 and a long lifespan over 1800 cycles at 1 mA cm −2 . Moreover, a full cell with a LiNi 0.88 Co 0.1 Al 0.02 O 2 cathode at a high mass loading ≈12 mg cm −2 reached over 400 cycles at 1.2 mA cm −2 , which represents a major progress in the performance of the garnet‐type SSLMBs. This study provides atomic‐scale understanding of interfaces in SSLMBs and an effective strategy to design dendrite‐free SSLMBs for practical applications.