Surficial modification enabling planar Al growth toward dendrite-free metal anodes for rechargeable aluminum batteries

This study is led by Prof. Chuan Wu. Serving as one of the most promising candidates among multivalent metal batteries, rechargeable aluminum batteries (RABs) are endowed with various advantages including abundant Al source and high theoretical capacities of Al metal anode. However, the growth of Al dendrite from Al metal anodes during cycling could lead to the short circuit of full cells after repeated Al stripping and plating, which is a key issue towards the long-term cycling performance and practical application of RABs. With increasing efforts that have been devoted to pursuing high-performance cathode materials for the improvement of energy density and cyclic lifespan in RABs, the bottleneck with respect to the stable electro-stripping/-plating of Al metal has been overlooked, Therefore, it is urgent to investigate the morphology evolution of electro-deposited Al and to suppress the Al dendrite formation during cycling.

Herein, a facile and applicable surficial modification method to realize the in-situ modification of Al metal anode surface with F–Al–O chemical bonds has been achieved, through soaking in commercial lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)-based electrolytes. This novel strategy offers an effective route towards low-cost Al metal anodes with superior performance, demonstrated by electrochemical measurements of both symmetric cells and dual-ion full cells coupled with commercial graphite paper cathodes.

Compared to Al–O bonds on the surface of pristine Al metal anodes, the generation of F–Al–O bonds is confirmed to reduce the overpotential upon reversible Al plating and stripping, leading to improved rate capabilities. Moreover, according to both experimental results and theoretical analysis, the surficial modification with F–Al–O chemical bonds is suggested to regulate the interaction between anodes and deposited Al, which could induce the ideal deposition of Al with planar morphology and mitigate the Al dendrite formation. On the contrary, the utilization of pristine Al metal anodes for the Al plating and stripping leads to the gradual growth of Al dendrites due to the accumulation of Al particles, resulting in the short circuit and cell failure. 

Thus, both symmetric cells and full cells based on modified F–Al metal anode are endowed with high cyclic stability without the short circuit caused by Al dendrite formation, which is apparently superior to the cell performance using pristine Al metal anodes. This work reveals the relation between the surficial chemical composition and the cycle life of Al metal anodes, paving the path for state-of-the-art RABs without severe Al dendrite problem.

See the article: 

Surficial modification enabling planar Al growth toward dendrite-free metal anodes for rechargeable aluminum batteries

https://doi.org/10.1007/s11426-023-1940-1