New 'bouncer' membrane boosts lithium-selenium battery performance and lifespan
A carbon quantum dot-based layer blocks unwanted chemical reactions, paving the way for more efficient and durable energy storage systems
image: Reinforcing conversion of polyselenides via a bifunctional blocking layer for efficient Li-Se batteries
Credit: Hongrui Wang, Qingyuan Zhao & Kang Lai
As the demand for high-performance energy storage continues to grow for applications from mobile electronics to electric vehicles, scientists are exploring alternatives to conventional lithium-ion batteries. Lithium-selenium Li-Se batteries are a promising candidate due to their high volumetric energy density. However, their practical application has been hindered by a persistent problem that degrades their performance and shortens their lifespan.
A central issue in Li-Se batteries is the "shuttle effect," where intermediate compounds called polyselenides dissolve into the electrolyte during battery operation. These dissolved polyselenides then shuttle between the cathode and anode, leading to the loss of active material and irreversible reactions with the lithium metal anode. This process ultimately causes rapid capacity decay and low efficiency, impeding the development of reliable Li-Se batteries.
A Novel Solution: The Bifunctional Membrane
To address this challenge, a team of researchers from Hunan Agricultural University, the National University of Defense Technology, and the Hunan Academy of Forestry has engineered a new type of battery separator. In their study published in Carbon Research, scientists led by Xianxiang Zeng, Xiongwei Wu, and Jiayu Dai describe a bifunctional membrane that effectively suppresses the shuttle effect while enhancing the battery's chemical reactions. The team coated a standard separator with a hybrid layer made of polyethylenimine-derived carbon quantum dots, or PEI Cdots, and a conductive carbon material known as Super P.
How It Works: A Two-Pronged Attack
The new membrane functions through a dual-action mechanism. The PEI Cdots, rich in polar amine groups, act as a selective barrier. They effectively trap the migrating polyselenides through strong chemical interactions, preventing them from reaching and reacting with the anode. Concurrently, the Super P component forms an interconnected, porous, and conductive skeleton. This network facilitates the rapid transport of lithium ions and electrons, which accelerates the desired Li-Se conversion reactions and improves the battery's overall kinetics.
Putting It to the Test
Electrochemical tests confirmed the effectiveness of the new design. Li-Se batteries equipped with the bifunctional membrane demonstrated superior performance compared to those with a standard separator. The modified batteries achieved a high specific capacity of 658.60 mAh g−1 at a low rate and maintained a high average coulombic efficiency of 97.8 percent. The membrane also enabled the battery to retain its capacity better at higher charge and discharge rates and showed stable cycling performance over 80 cycles.
Backed by Theoretical Calculations
The research team supported their experimental findings with computational modeling. Using Density Functional Theory calculations, they simulated the interactions between the membrane and the polyselenides at a molecular level. The results showed that the nitrogen element within the PEI Cdots creates strong binding sites for long-chain polyselenides, confirming that the membrane actively traps these unwanted compounds and restricts their movement, which is essential for stabilizing the battery.
Implications for Future Energy Storage
This work presents an effective and straightforward membrane engineering strategy to overcome a major obstacle in Li-Se battery technology. By inhibiting the shuttle effect and reinforcing conversion kinetics, especially with a high selenium loading of 70 percent, this approach moves energy-dense metal batteries closer to practical use. The findings offer a valuable pathway for developing more durable and efficient next-generation energy storage systems for a wide range of applications.
Corresponding Author:
Jiayu Dai, Xiongwei Wu or Xianxiang Zeng
Original Source:
https://doi.org/10.1007/s44246-023-00064-2
Contributions:
Conceptualization and Funding acquisition: Xianxiang Zeng, Xiongwei Wu, and Jiayu Dai; Investigation and Methodology: H.-R. Wang; Writing-original draft: Hongrui Wang and Qingyuan Zhao; Formal Analysis: Kang Lai, Nanyun Bao, and Zhiqiang Fu; Resources and Software: Jiayu Dai; Writing-review & editing: Xianxiang Zeng, Weibin Zhou and Qi Deng. All authors read and approved the final manuscri
pt.