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Novel porous membrane suppresses dendrite growth on Li-metal anodes

After first analyzing the role and underlying fundamental mechanisms of porous media in suppressing dendritic Li growth on Li metal anodes, a team of researchers from the US and China has synthesized a novel porous silicon nitride submicron-wire membrane and incorporated it in both half-cell and full-cell configurations to suppress the formation of lithium dendrites.

In a paper in the ACS journal Nano Letters, they report that the operation time of the battery cells was significantly extended without a short circuit. They suggest that their findings lay the foundation to use a porous medium for achieving nondendritic Li growth in Li metal-based batteries.

… the recent development of rechargeable Li metal batteries (LiMBs) has faced regular setbacks due to the growth of Li dendrites, a phenomenon that is hard to control yet substantially compromises the performance of LiMBs, leading to low Coulombic efficiency, poor cycle stability, and even short-circuiting-related safety hazards. To conquer this challenge and commercialize high-energy LiMBs, a new round of “gold rush” has been launched in related academic and industrial fields, and several strategies have been proposed to suppress dendrite growth.

Recently, introducing submicron-/nanoporous media (e.g., solid electrolytes, modified separators, and artificial protection layers) in LiMBs has emerged as a promising alternative strategy to solve the notorious dendrite growth problem for its versatility, simpleness, and high efficiency. However, an in-depth fundamental understanding of these experiments is lacking, which has hindered the continued development of these strategies to revive LiMBs further.

Because the solid electrolyte, modified separator, and artificial protection layer all have submicron-/nanoporous structures, their dendrite suppression performance is hypothetically associated with the shared structural feature, that is, a porous medium. As a proof-of-principle, we fabricated and incorporated a novel porous silicon nitride (α-Si3N4) submicron-wire membrane in symmetric Li/Li cells, which have shown no apparent dendrite growth after cycling for more than 3000 h. Given the various possible combinations of components and materials in batteries, a systematic investigation around the effects of porous geometry could provide guidance for achieving Li and other metal-based (e.g., Na, K, Zn, and Al) batteries without critical dendritic metal growth.

—Li et al.

The team’s mesoscale simulations revealed that the tortuous pores of the porous media are the key to achieving the nondendritic Li growth.

  • The tortuous pores drastically reduce the local flux of Li+ moving toward the anode; and

  • on the other hand, they effectively extend the physical path of dendrite growth.

Li
Simulation of Li growth with or without the porous membrane. (a−d) Dendrite growth simulation results at the reaction rate of K = 50 μm s−1 (a,b) and 5 μm s−1 (c,d) (gray, a liquid electrolyte; black, anode surface and porous membrane structure; white, dendrites). (e,f) Li+ concentration overlaid with the mass transport flux near the anode surface with the fiber membrane (e) and without the fiber membrane (f) for K = 5 μm s−1. Dendrite deposition is disabled in panels e and f to eliminate the growing reactive boundary of the dendrite so that the effects of pore structure on mass transport can be seen. Credit: ACS, Li et al. Click to enlarge.

Resources

  • Nan Li, Wenfei Wei, Keyu Xie, Jinwang Tan, Lin Zhang, Xiaodong Luo, Kai Yuan, Qiang Song, Hejun Li, Chao Shen, Emily M. Ryan, Ling Liu, and Bingqing Wei (2018) “Suppressing Dendritic Lithium Formation Using Porous Media in Lithium Metal-Based Batteries” Nano Letters 18 (3), 2067-2073 doi: 10.1021/acs.nanolett.8b00183

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