Amorphous solid electrolytes (SEs) have shown great potential in improving the energy density and performance of all-solid-state lithium batteries (ASSLBs). A recent study published in the Journal of the American Chemical Society by a research team led by Prof. Yao Hongbin from the University of Science and Technology of China (USTC) highlights the successful construction of a glassy Li-ion conduction network and the development of amorphous tantalum chloride SEs with high Li-ion conductivity. This breakthrough paves the way for realizing high-nickel cathodes with high performance in ASSLBs.
Compared to ceramic SEs, amorphous SEs stand out due to their unique glassy networks that allow for intimate solid-solid contact and efficient Li-ion conduction percolation. These properties make amorphous SEs conducive to fast Li-ion conduction and hold promise in enabling the effective use of high-capacity cathodes and stable cycling. Consequently, amorphous SEs significantly increase the energy density of ASSLBs.
Despite the advantages of amorphous SEs, challenges remain in terms of areal capacity and room-temperature ionic conductivity. The amorphous Li-ion conduction phosphorous oxynitride (Li1.9PO3.3N0.5, LiPON) falls short in comparison to current commercialized Li-ion batteries when it comes to energy/power density. To address this challenge, the research team aimed to develop amorphous SEs with high Li-ion conductivity and ideal chemical or electrochemical stability.
Exploring Crystalline Halides
Crystalline halides, including fluorides, chlorides, bromides, and iodides, hold promise in realizing high-energy-density ASSLBs due to their high voltage stability and ionic conductivity. However, there is a lack of studies regarding the development of amorphous chloride SEs. The research team tackled this gap by proposing a new class of amorphous chloride SEs with high Li-ion conductivity. They demonstrated excellent compatibility with high-nickel cathodes and successfully achieved a high-energy-density ASSLB with a wide temperature range and stable cycling.
Structural Features and Material Design
Researchers determined the structural features of the LiTaCl6 amorphous matrix using advanced techniques such as random surface walking global optimization combined with a global neural network potential function. They also utilized solid-state nuclear magnetic resonance spectroscopy, X-ray absorption fine-structure fitting, and low-temperature transmission electron microscopy for further characterization of the matrix. Based on component design flexibility, the team developed a series of high-performance and cost-effective Li-ion composite solid electrolyte materials with the highest room-temperature Li-ion conductivity reaching up to 7 mS cm-1, meeting the practical application requirements of high-magnification ASSLBs.
The applicability of ASSLBs constructed with amorphous chloride SEs was verified over a wide temperature range. These batteries achieved a high rate close to 10,000 cycles of stable operation even in freezing environments as low as -10°C. The component flexibility, fast ionic conductivity, and excellent chemical and electrochemical stability exhibited by amorphous chloride SEs provide a new direction for the design and construction of high-performance ASSLBs with high-nickel cathodes.
The development of amorphous SEs with high Li-ion conductivity and ideal stability opens up new possibilities for enhancing the performance and energy density of ASSLBs. The research team’s breakthrough in constructing a glassy Li-ion conduction network using amorphous tantalum chloride SEs highlights the potential of amorphous SEs in overcoming the limitations of traditional crystalline SEs. This advancement sets the stage for the realization of high-performance ASSLBs with high-nickel cathodes. The collaboration between Prof. Yao Hongbin from USTC, Prof. Shang Cheng from Fudan University, and Prof. Tao Xinyong at Zhejiang University of Technology showcases the significance of interdisciplinary research in pushing the boundaries of battery technology.
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