Safe, long-cyclable lithium metal battery for high temperatures

Rechargeable lithium metal batteries are a promising aleternative to ubiquitous lithium-ion batteries in electric vehicles and energy storage applications that require high energy density. However, their practical implementation is held back by safety concerns and a shortened battery cycle life arising from a combination of undesirable lithium dendrite and solid-electrolyte interphase formations.

Now, a team of researchers at the University of Hong Kong (HKU) has developed a new generation of lithium metal batteries based on microcrack-free polymer electrolytes, which promise extended lifespan and enhanced safety at temperatures as high as 100 degrees Celsius.

The microcrack-free polymer electrolytes are synthesised via a straightforward one-step click reaction, exhibiting notable attributes including “a remarkable resistance to dendrite growth and outstanding non-flammability,” the researchers reported.

They also demonstrated a wide electrochemical stability window up to 5 V, and a high cation conductivity of 3.1 × 10−5 S cm⁻¹ at high temperatures.

These enhanced properties are attributed to the presence of tethered borate anions in microcrack-free membranes, which benefits the acceleration of selective Li⁺ cations transport as well as suppression of dendrite growth.

Ultimately, the microcrack-free anionic network polymer membranes enable lithium metal batteries to function as safe and long-cyclable energy storage devices at high temperatures with a capacity retention of 92.7% and an average coulombic efficiency of 99.867% over 450 cycles at 100 degrees Celsius.

By comparison, the cycling performance of conventional liquid electrolyte lithium metal batteries is fewer than 10 cycles at high temperatures.

“We believe this innovation opens doors for new battery chemistries that can revolutionise rechargeable batteries for high-temperature applications, emphasising safety and longevity,” said Dong-Myeong Shin, professor at the Department of Mechanical Engineering at HKU and the first author of the research paper.

“Apart from applications in high-temperature scenarios, the microcrack-free electrolyte membranes also have the potential to enable fast charging due to low overpotential. This capability could allow electric vehicles to recharge in the time it takes to drink a cup of coffee, marking a significant advancement towards a clean energy future,” Shin added.

The researchers argue that their strategy of enhancing the cyclability and safety of lithium metal batteries through the incorporation of microcrack-free anionic network polymer membranes is broadly applicable to other high energy density batteries, potentially paving the way for future advancements in the design of anionic electrolytes for the next-generation lithium batteries.

Their findings are further discussed in Accelerated Selective Li+ Transports Assisted by Microcrack-Free Anionic Network Polymer Membranes for Long Cyclable Lithium Metal Batteries, published in Advanced Science.