Acta Phys. -Chim. Sin. ›› 2021, Vol. 37 ›› Issue (1): 2009006.doi: 10.3866/PKU.WHXB202009006

Special Issue: Lithium Metal Anodes

• COMMUNICATION • Previous Articles     Next Articles

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

Mingli Cai1,2, Liu Yao1,2, Jun Jin1,2, Zhaoyin Wen1,2,*()   

  1. 1 CAS Key Laboratory of Materials for Energy Conversion, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China
    2 Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2020-09-01 Accepted:2020-09-24 Published:2020-10-09
  • Contact: Zhaoyin Wen E-mail:zywen@mail.sic.ac.cn
  • About author:Zhaoyin Wen. Email: zywen@mail.sic.ac.cn; Tel.: +86-21-52411704
  • Supported by:
    the National Key R & D Program of China(2018YFB0905400);the National Natural Science Foundation of China(51772315);the Science and Technology Commission of Shanghai Municipality(18DZ2280800)

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Abstract:

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 LiNi0.5Co0.2Mn0.3O2 (NCM523) or LiFePO4 cathodes can cycle stably for over 100 cycles at RT.

Key words: Garnet electrolyte, Zn(NO3)2 aqueous solution, In situ modification, Interfacial stability, Solid-state Li battery

MSC2000: 

  • O646