New superionic conductive electrolyte could improve stability of all-solid-state lithium metal batteries

All-solid-state lithium metal batteries (LMBs) are promising energy storage solutions that integrate a lithium metal anode and solid-state electrolytes (SSE), as opposed to liquid electrolytes found in conventional lithium batteries . While solid-state LMBs could feature significantly higher energy densities than lithium-ion batteries (LiB), the solid electrolytes they contain are prone to dendrite growth, reducing their stability and their safety.

Researchers from Western University in Canada, the University of Maryland in the United States and other institutes recently designed a new superionic, vacancy-rich conductive β-Li.₃Solid electrolyte N (SSE). The electrolyte, reported in an article recently published in Nature Nanotechnologycould maintain a stable cycle of fully solid LMBs, potentially facilitating their commercialization.

“The main goal of our work was to develop lithium-stable, superionic conductive ESSs for all-solid-state LMBs, particularly targeting their application in electric vehicles (EVs),” said Weihan Li, first author of the paper. article, at Phys.org. .

“The electric vehicle market is growing rapidly, but a major limitation remains the short range of 300-400 miles per charge, mainly due to the limited energy density (~300 Wh/kg) of conventional lithium-ion batteries. Lithium metal batteries represent a promising solution to this challenge by offering the potential to achieve energy densities of up to 500 Wh/kg, extending range to over 600 miles per charge.

Until now, one of the main challenges encountered in the development of all-solid-state LMBs has been the lack of safe, reliable, and high-performance ESSs. The main goal of Li and co-workers’ recent work was to design a new electrolyte that combines high stability against metallic lithium and high ionic conductivity.

“Building on our previous understanding of SSEs, we identified nitrides as a class of materials that are stable against metallic lithium,” said Li. “However, conventional nitrides exhibit low ionic conductivity. Leveraging our knowledge lithium conduction mechanisms, we designed a vacancies-rich β-Li.₃N SSE.”

In first tests, the new vacancy-rich β-Li₃The N SSE designed by this team of researchers demonstrated 100 times higher ionic conductivity and greater stability compared to commercial Li.₃N. This promising material could thus help overcome the limitations generally associated with the development of high-performance all-solid LMBs.

“Our conception of β-Li rich in vacancies₃N was guided by an understanding of the mechanisms of lithium-ion conduction,” Li said. “Defects in the crystal structure, such as vacancies, can reduce the energy barriers for lithium-ion migration and increase the population of “mobile lithium ions.”

Researchers synthesized vacancy-rich β-Li₃N SSE using a high energy ball mill process. This process was used to introduce a controlled number of vacancies into the material’s structure, which ultimately improved its properties.

“The ionic conductivity of vacancy-rich β-Li₃N is 100 times higher than that of commercial Li₃N,” explained Li. “It demonstrates excellent chemical stability against lithium metal, enabling the fabrication of long-cycle, all-solid LMBs. The material also exhibits high stability in dry air, making it suitable for industrial-scale production in dry environments. »

When they integrated their new SSE into an LMB, the researchers achieved an unprecedented ionic conductivity for an SSE, reaching 2.14 × 10.⁻³ S cm⁻¹ at 25°C. Symmetrical electrolyte-based battery cells achieved high critical current densities up to 45 mA cm⁻²and high capacities up to 7.5 mAh cm⁻²as well as ultra-stable lithium pickling and plating processes over 2,000 cycles.

“Our study achieved record ionic conductivity and exceptional stability with lithium metal for an SSE,” Li said. “These results are important because they address two of the most critical challenges in developing all-solid-state LMBs.”

The new material synthesized by this team of researchers could open up exciting new possibilities for manufacturing all-solid LMBs, potentially improving their energy density and accelerating their charging. These batteries could eventually be integrated into electric vehicles and other large electronic devices, to extend their lifespan and reduce the time needed to charge them.

“In the future, my research will focus on two main directions,” Li added. “On the one hand, my goal is to address the remaining interfacial challenges in all-solid LMBs to further improve lithium-ion conduction and extend battery life. This will involve in-depth studies of interfacial reaction kinetics and new material designs.

“On the engineering side, I intend to address practical challenges by developing commercial-scale prototype cells and pocket cells based on vacancy-rich β-Li.₃N. This will include optimizing the material for large-scale production and integrating it into functional battery systems suitable for real-world applications. »

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