Amorphous solid electrolytes (SEs) have emerged as a promising solution for increasing the energy density of all-solid-state lithium batteries (ASSLBs). Researchers have made significant progress in developing amorphous SEs with high Li-ion conductivity and ideal chemical stability. This article delves into the recent advancements in the construction of a glassy Li-ion conduction network and the development of amorphous tantalum chloride SEs, which have shown remarkable potential in improving the performance of ASSLBs.
Compared to ceramic SEs, amorphous SEs possess unique glassy networks that facilitate solid-solid contact and promote efficient Li-ion conduction. This characteristic makes amorphous SEs particularly suitable for the effective utilization of high-capacity cathodes and stable cycling. However, thin-film cathodes with low areal capacity and poor room-temperature ionic conductivity have hindered the energy/power density of amorphous Li-ion conduction phosphorous oxynitride (LiPON) when compared to current commercialized Li-ion batteries.
The Need for Ideal Amorphous SEs
To overcome the limitations of existing amorphous SEs, it is essential to develop SEs with high Li-ion conductivity and excellent chemical or electrochemical stability. Researchers have turned their attention to crystalline halides, such as fluorides, chlorides, bromides, and iodides, due to their high voltage stability and ionic conductivity. While the potential of crystalline chloride SEs has been explored to some extent, studies on developing amorphous chloride SEs remain scarce.
Novel Amorphous Chloride SEs
In a recent breakthrough, a research team led by Prof. Yao Hongbin from the University of Science and Technology of China successfully developed a new class of amorphous chloride SEs with high Li-ion conductivity. These SEs demonstrated excellent compatibility with high-nickel cathodes and enabled the construction of high-energy-density ASSLBs that operate efficiently across a wide range of temperatures.
To understand the structural features of the LiTaCl6 amorphous matrix, the research team employed various techniques such as random surface walking global optimization, solid-state nuclear magnetic resonance lithium spectroscopy, X-ray absorption fine-structure fitting, and low-temperature transmission electron microscopy. These analyses provided insights into the composition and microstructure of the matrix, enabling the development of high-performance Li-ion composite solid electrolyte materials.
High-Performance Composite SEs
Utilizing the flexibility in component design, the researchers prepared a series of high-performance and cost-effective Li-ion composite SE materials with a room-temperature Li-ion conductivity of up to 7 mS cm-1. These materials meet the practical application requirements of high-magnification ASSLBs and offer improved ionic conductivity.
Wide Temperature Range Applicability
The researchers successfully verified the applicability of ASSLBs constructed with amorphous chloride SEs over a wide temperature range. The batteries exhibited stable operation, even in freezing temperatures as low as -10°C. Achieving a high rate of 3.4 C and enduring close to 10,000 cycles highlights the excellent performance of these ASSLBs.
Implications and Future Prospects
The breakthrough in developing amorphous chloride SEs not only extends the range of high-performance composite SEs but also overcomes the limitations of traditional crystalline SEs in terms of their structure and component design. This advancement paves the way for realizing high-nickel cathodes with superior performance in ASSLBs. The flexibility, fast ionic conductivity, and chemical and electrochemical stability exhibited by the amorphous chloride SEs offer valuable insights for the design of novel SEs and the construction of high-ratio ASSLBs.
The introduction of amorphous SEs with high Li-ion conductivity has opened up new avenues for enhancing the energy density of lithium batteries. The development of amorphous tantalum chloride SEs showcases the potential of these materials in enabling the effective utilization of high-capacity cathodes and stable cycling. Further research and innovation in the field of amorphous SEs hold the key to unlocking the full potential of ASSLBs and revolutionizing the realm of energy storage.