Hybrid electrolyte brings together the best for better lithium-ion batteries

Newswise — Lithium-ion batteries powered the device these words appear on. From phones and laptops to electric vehicles, lithium-ion batteries are essential to the technology of the modern world, but they can also explode. Comprising negatively and positively charged electrodes and an electrolyte to carry the ions through the division, lithium-ion batteries are only as efficient as the limits of their components. Liquid electrolytes are potentially volatile at high temperatures and their effectiveness may be limited by the non-uniformity and instabilities of other components.

Researchers are working to develop safer and more efficient batteries with solid electrolytes, a significant change from the liquid version that currently carries the ions in most commercially available batteries. The challenge is that each solid-state material has as many disadvantages as advantages, according to a team based at the Shenzhen All-Solid-State Lithium Battery Electrolyte Engineering Research Center at the China Research Institute. materials from Tsinghua Shenzhen International Graduate School.

To solve this conundrum, the researchers combined two of the leading solid-state candidates – ceramic and polymer – into a new composite electrolyte.

They published their results on September 21 in Energy materials and devices.

“Solid-state composite electrolytes have received considerable attention due to their combined advantages as inorganic and polymer electrolytes,” said co-first author Yu Yuan, also affiliated with Tsinghua Shenzhen International Graduate School. “However, conventional inorganic ceramic fillers offer limited improvement in ionic conductivity for solid-state composite electrolytes due to the space charge layer between the polymer matrix and the ceramic phase.”

Inorganic ceramic electrolytes offer high conductivity, but they develop resistance when confronted with another solid and are complicated to synthesize. Polymer electrolytes are easier to produce, more flexible, and work better with electrodes, but their conductivity at room temperature is too low for commercial application. According to Yuan, the combination of the two should produce an electrolyte that is flexible, highly conductive and easier to synthesize. In reality, however, when mixed, solid-state composite electrolytes exhibit a separation—called a space charge layer—between their constituent elements that limits their conductivity.

To correct this, the researchers used lithium tantalate, which has a crystal structure that lends itself to unique optical and electrical properties, as a functional filler to attenuate the space charge layer. The ceramic ion-conducting material is ferroelectric, meaning it can reverse the electrical charge when a current is applied.

“Not only does charging attenuate the space charge layer, but it also provides an additional transport pathway for lithium-ion,” said co-first author Likun Chen, also affiliated with Tsinghua Shenzhen International Graduate School.

The researchers experimentally demonstrated that charging lithium tantalate alleviates the lithium ion transport bottleneck across the polymer-ceramic interface, resulting in lithium ions moving in increased numbers and speed through the electrolyte.

The result, according to the researchers, is an electrolyte with high conductivity and a long lifespan – referring to the frequency with which ions can be transported through the battery during charge and discharge cycles – even at low temperatures .

“This work proposes a new strategy to design integrated ceramic fillers with ferroelectric and ion-conducting properties to achieve high-rate lithium-ion transport of composite-solid electrolytes for advanced lithium metal batteries. solid state,” Yuan said. “Our approach sheds light on the design of functional ceramic fillers for solid-state composite electrolytes to effectively improve ionic conductivity and battery performance.”

Other co-authors include Yuhang Li, Xufei An, Jianshuai Lv, Shaoke Guo, Xing Cheng, Yang Zhao, Ming Liu, Yan-Bing He and Feiyu Kang. Li, An, Lv, Guo, Cheng, Zhao and Kang are also affiliated with Tsinghua Shenzhen International Graduate School.

The National Natural Science Foundation of China, Guangdong Province Key Field Research and Development Program, Shenzhen Outstanding Talent Training Fund, Semi-Lithium Battery Electrolyte Engineering Research Center -conductors and the Shenzheng Technical Plan Project supported this research.