Amorphous chloride solid electrolytes with high Li-ion conductivity

A research team led by Prof. YAO Hongbin from the University of Science and Technology of China (USTC) of the Chinese Academy of Sciences, in collaboration with Prof. SHANG Cheng from Fudan University and Prof. TAO Xinyong from Zhejiang University of Technology, constructed a glassy Li-ion conduction network and developed amorphous tantalum chloride solid electrolytes (SEs) with high Li-ion conductivity. The study was published in Journal of the American Chemical Society.

Studies have showed that amorphous SEs distinguishes itself by inherent unique glassy networks for intimate solid-solid contact and extraordinary Li-ion conduction percolation and are conducive to the fast Li-ion conduction. However, due to its low areal capacity of the thin-film cathode and the poor room-temperature ionic conductivity, the amorphous Li-ion conduction phosphorous oxynitride is inferior to the commercialized Li-ion batteries in terms of the energy/power density. It is necessary to develop amorphous SEs with high Li-ion conductivity and ideal chemical (or electrochemical) stability.

Crystalline halides, compounds in which the halogens are negatively valenced, including fluorides, chlorides, bromides, iodides, have been revealed to be promising for realizing high-energy-density all-solid-state lithium batteries (ASSLBs) for their high voltage stability and high ionic conductivity. However, there are still few studies on the development of amorphous chloride SEs.

In this study, the researchers proposed a new class of amorphous chloride SEs with high Li-ion conductivity which demonstrated an excellence compatibility for high-nickel cathodes, and realized a high-energy-density ASSLB with a wide temperature range and stable cycling.

The researchers determined the structural features of the LiTaCl6 amorphous matrix by employing random surface walking global optimization combined with a global neural network potential (SSW-NN) function for a full-situ energy surface search, and one-dimensional solid-state nuclear magnetic resonance lithium spectroscopy for the decoupling of chemical environments, X-ray absorption fine-structure fitting, and low-temperature transmission electron microscopy for the microstructural characterization of the matrix.

A series of high-performance and cost-effective Li-ion composite solid electrolyte materials with the highest room-temperature Li-ion conductivity up to 7 mS cm^-1 were prepared which meet the application requirements of high-magnification ASSLBs.

Furthermore, the researchers verified the applicability of the ASSLBs developed based on amorphous chloride over a wide temperature range. The component flexibility, fast ionic conductivity, and excellent chemical and electrochemical stability exhibited by the amorphous chloride SEs provided new ideas for designing new SEs and constructing high-ratio ASSLBs. This study paves the way for realizing high-nickel cathodes with high-performance for ASSLBs.

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Source: Chinese Academy of Sciences