High-energy lithium metal pouch cells with limited anode swelling and long stable cycles

by Niu, Chaojiang; Lee, Hongkyung; Chen, Shuru; Li, Qiuyan; Du, Jason; Xu, Wu; Zhang, Ji-Guang; Whittingham, M. Stanley; Xiao, Jie; Liu, Jun

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Lithium metal anodes have attracted much attention as candidates for high-energy batteries, but there have been few reports of long cycling behaviour, and the degradation mechanism of realistic high-energy Li metal cells remains unclear. Here, we develop a prototypical 300 Wh kg(-1) (1.0 Ah) pouch cell by integrating a Li metal anode, a LiNi0.6Mn0.2Co0.2O2 cathode and a compatible electrolyte. Under small uniform external pressure, the cell undergoes 200 cycles with 86% capacity retention and 83% energy retention. In the initial 50 cycles, flat Li foil converts into large Li particles that are entangled in the solid-electrolyte interphase, which leads to rapid volume expansion of the anode (cell thickening of 48%). As cycling continues, the external pressure helps the Li anode maintain good contact between the Li particles, which ensures a conducting percolation pathway for both ions and electrons, and thus the electrochemical reactions continue to occur. Accordingly, the solid Li particles evolve into a porous structure, which manifests in substantially reduced cell swelling by 19% in the subsequent 150 cycles.

Journal
Nature Energy
Volume
4
Issue
7
Year
2019
Start Page
551
ISBN/ISSN
2058-7546
DOI
10.1038/s41560-019-0390-6