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 solidstate 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.

Directly Using Li2CO3 as a Lithiophobic Interlayer to Inhibit Li Dendrites for High-Performance Solid-State Batteries

“…25−27 However, these strategies usually introduce additional pollutants or induce the loss of Li to form some electrochemically conductive defects. 28,29 Another strategy is to convert the Li 2 CO 3 on the LLZTO surface into lithiophilic or lithium-conducting materials, such as LiCoO 2 , Li x SiO y , Li 3 PO 4 , and LiF. 30−33 This strategy usually requires a high equipment environment and adds production costs.…”

“…To solve the Li|LLZTO interfacial problems caused by Li 2 CO 3 , one conventional strategy is to remove the Li 2 CO 3 on the LLZTO surface by physical or chemical methods, including mechanical polishing, , high-temperature treatment, and acid treatment. − However, these strategies usually introduce additional pollutants or induce the loss of Li to form some electrochemically conductive defects. , Another strategy is to convert the Li 2 CO 3 on the LLZTO surface into lithiophilic or lithium-conducting materials, such as LiCoO 2 , Li x SiO y , Li 3 PO 4 , and LiF. − This strategy usually requires a high equipment environment and adds production costs. Recently, Wang et al proposed to use Li 2 O and Li-Sr alloy as a lithiophobic interlayer and lithiophilic interlayer, respectively, to effectively inhibit the growth of Li dendrites .…”

Revealing the Influence of Surface Microstructure on Li Wettability and Interfacial Ionic Transportation for Garnet‐Type Electrolytes

“…At 0.2 mA cm −2 , the R int of the symmetric cell decreases with the decrease of LLZTO roughness (Figure 2f and Table S3, Supporting Information), again demonstrating the importance of LLZTO surface roughness to establish a good Li + path at the interface. In addition, this simple polishing method can achieve a small interfacial resistance as low as 1.7 Ω cm 2 , which is smaller than those of previously reported Li/garnet cells upon various surface treatments [18,26,[49][50][51][52][53][54][55][56][57][58][59] (Figure S10, Supporting Information) and shows the superiority if this simple strategy in improving interfacial wettability and reducing interfacial resistance.…”

Recent advances in in situ and operando characterization techniques for Li7La3Zr2O12-based solid-state lithium batteries

“…Notably, an initial investigation of LLZO-based SSLBs has been carried out with ex situ cryo-TEM technique. 92 Results indicate that microcracks which originate from Li dendrite growth are introduced by mechanically polishing the LLZO surface to eliminate the contaminant layer. An interlayer consisting of amorphous carbon and nanocrystalline LiF is formed in situ by the introduction of CF x and molten Li.…”