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

All-solid-state lithium metal batteries (LMBs) are a promising energy storage solution that incorporates a lithium metal negative electrode and a solid electrolyte (SSE), as opposed to the liquid electrolyte found in traditional lithium batteries. Solid-state LMBs can exhibit significantly higher energy densities compared to lithium-ion batteries (LiBs), but their stability and safety are compromised because the solid-state electrolytes they contain are prone to dendrite growth. decreases.

Researchers at Western University in Canada, the University of Maryland in the US, and other research institutions recently designed a new vacancy-rich, superionically conductive β-Li3N solid electrolyte (SSE). The electrolyte, reported in a paper recently published in Nature Nanotechnology, can sustain stable cycling of all-solid-state LMB, potentially facilitating commercialization.

“The main objective of our research was to develop lithium-stable, superionically conductive SSEs for all-solid-state LMBs, specifically targeting electric vehicle (EV) applications,” the paper states. Weihan Li, lead author of the study, told Phys.org. .

“The EV market is experiencing rapid growth, but the range on a single charge is limited to 300-400 miles, mainly due to the limited energy density of traditional lithium-ion batteries (approximately 300Wh/kg). An important limitation still remains: lithium metal batteries offer the possibility of achieving energy densities of up to 500 Wh/kg, thereby increasing the range on a single charge to 600. It is a promising solution to this challenge as it can extend beyond miles.”

To date, the main challenge in the development of all-solid-state LMBs has been the lack of safe, reliable, and high-performance SSEs. The main goal of recent work by Lee et al. was to design a new electrolyte that combines high stability with lithium metal and high ionic conductivity.

“Based on our previous understanding of SSE, we identified nitrides as a type of material that is stable to lithium metal,” Li said. “However, conventional nitrides exhibit low ionic conductivity. We leveraged our knowledge of lithium conduction mechanisms to design vacancy-rich β-Li3N SSEs.”

Initial tests demonstrate that the new vacancy-rich β-Li3N SSE designed by the research team has 100 times better ionic conductivity and better stability compared to commercially available Li3N. Therefore, this promising material could help overcome the limitations typically associated with the development of high-performance all-solid-state LMBs.

“The design of vacancy-rich β-Li3N was based on our understanding of the lithium ion conduction mechanism,” Li said. “Defects in the crystal structure, such as vacancies, can lower the energy barrier to lithium ion movement and increase the number of lithium ions that can be moved.”

The researchers synthesized vacancy-rich β-Li3N SSE using a high-energy ball milling process. This process was used to introduce a controlled number of pores into the structure of the material, ultimately improving its properties.

“The ionic conductivity of vacancy-rich β-Li3N is 100 times that of commercially available Li3N,” Li explained. “This material exhibits excellent chemical stability toward lithium metal, enabling the production of long-cycle all-solid-state LMBs. This material also exhibits high stability in dry air, making it suitable for use in dry rooms. Suitable for industrial scale production in environments.

When the researchers integrated their newly designed SSE into an LMB, they achieved unprecedented ionic conductivity for an SSE, reaching 2.14 × 10−3 S cm−1 at 25 °C. This electrolyte-based symmetrical battery cell delivers high critical current density up to 45 mA cm-2 and high capacity up to 7.5 mAh cm-2, as well as an ultra-stable lithium stripping and plating process of over 2,000 cycles. It has come true.

“Our research achieved record ionic conductivity and exceptional stability using lithium metal for SSE,” Li said. “These discoveries are important because they address two of the most important challenges in the development of all-solid-state LMBs.”

The new material synthesized by this team of researchers could open up new and exciting possibilities for manufacturing all-solid-state LMBs, with the potential to increase energy density and speed up charging. These batteries could eventually be integrated into electric vehicles and other large electronic devices, extending battery life and reducing the time required to charge.

“Going forward, my research will focus on two main directions,” Lee added. “Meanwhile, I aim to address the interfacial challenges remaining in all-solid-state LMBs to further enhance lithium-ion conduction and extend battery life. This includes interfacial kinetics and new material designs. Includes thorough research.

“On the engineering side, we plan to address practical challenges by developing prototype cells and commercial-scale pouch cells based on vacancy-rich β-Li3N. It involves optimizing the material and integrating it into a suitable functional battery system for real-world applications. ”

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