水溶液法原位构建ZnO亲锂层稳定锂-石榴石电解质界面

固态电池以其高安全性和高能量密度而备受关注。石榴石型固体电解质(LLZO)由于具有较高的离子导电性和对锂金属的稳定性,在固态电池中具有应用前景,但陶瓷与锂金属较差的界面接触会导致高的界面阻抗和可能形成的枝晶穿透。我们利用LLZO表层独特的H⁺/Li⁺交换反应,提出了一种简便有效的金属盐类水溶液诱发策略,在电解质表面原位构建ZnO亲锂层,界面处LiZn合金化实现紧密连续的接触。引入改性层后,界面阻抗可显著降低至约10Ω·cm²,对称电池能够在0.1mA·cm^-2的电流密度下实现长达1000h的长循环稳定性。匹配正极LiFePO₄(LFP)或LiNi_0.5Co_0.2Mn_0.3O₂(NCM523)的准固态电池在室温下能够稳定循环100次以上。

In situ Lithiophilic ZnO Layer Constructed using Aqueous Strategy for a Stable Li-Garnet Interface

Solid-state batteries have garnered significant attention, owing to their high safety and improved energy density. Among various solid-state electrolytes (SSEs), garnet-type SSEs are promising for application in solid-state batteries, owing to their high ionic conductivities (10^-4–10^-3 S·cm^-1) at room temperature and excellent stability against Li metal. However, the poor contact between the rigid ceramic and Li metal will result in high interfacial impedance and uneven lithium ion flux during cycling. Consequently, this will lead to rapid dendrite penetration along the grain boundary and eventual short circuit. Herein, inspired by the unique H⁺/Li⁺ exchange reaction of the garnet electrolyte, we propose a facile and efficient metal salt aqueous-solution-based strategy to construct an in situ lithiophilic ZnO layer on the garnet surface without employing any specific apparatus. A Zn(NO₃)₂ aqueous solution was selected to modify the garnet surface. Within one minute, LiOH spontaneously formed as a result of the H⁺/Li⁺ exchange reaction reacted with Zn(NO₃)₂ to produce homogeneous precipitates. After heat treatment, a lithiophilic ZnO layer was obtained. This was verified by the results of X-ray diffraction and attenuated total reflection Fourier transform infrared spectroscopy analyses. Furthermore, combined with scanning electron microscopy (SEM) images and corresponding elemental mapping, it was proved that a thin in situ interlayer can be successfully deposited on the garnet surface using our strategy. Moreover, the deposited ZnO nanoparticles were uniformly and densely distributed on the garnet surface. In the presence of the introduced layer, the wettability of the garnet-type SSE with molten Li was greatly improved. The introduced ZnO nanoparticles reacted with molten Li to form a LiZn alloy, achieving a tight and continuous contact at the Li–garnet interface, thereby greatly reducing the interfacial impedance to ~10 Ω·cm². In the case of the untreated SSE in contact with the molten Li, the cross-sectional SEM image shows obvious gaps at the interface, indicating poor contact with Li. This resulted in a large interfacial resistance of up to 1350 Ω·cm². Moreover, the slow ion transport at the interface reduces the capacity of the battery, and the uneven Li ion flux shortens the life of the cell. With a modified layer, the formed LiZn alloy interphase acting as a mixed ionic and electronic conductive interlayer ensures a uniform Li ion flux at the interface and an appreciable electrochemical performance. Symmetric Li cells with modified garnet-type electrolytes can achieve long cycling stability for approximately 1000 h at a current density of 0.1 mA·cm^-2 at room temperature (RT). The quasi solid-state batteries with LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523) or LiFePO₄ cathodes can cycle stably for over 100 cycles at RT.