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Micro-nano multi-scale bionic structure design helps to improve the stability of metal lithium anode

2019-04-16 来源:亚科官网
 
For thousands of years, the various raw materials provided by nature have been the basis for human survival and reproduction. However, with the deepening of the understanding of nature, people began to pay more attention to the unique micro-nano structure inside the organism, and gained inspiration from it, and developed a variety of biomimetic materials. Today, bionic structural design has been applied to various fields such as mechanical materials, thermal insulation and catalysis.
Among battery materials, lithium metal anodes have been receiving widespread attention due to their high specific capacity and low potential. However, problems such as dendrite growth and volume expansion during electrochemical cycling greatly limit the practical application of lithium metal anodes. In many solutions, the introduction of a three-dimensional frame can increase the specific surface area of the negative electrode material, thereby reducing the actual current density and making the deposition and removal process of lithium metal more uniform. However, there are several problems that have to be faced in the three-dimensional framework. The first is the controllability of the microstructure size, that is, to explore the relationship between “structure-performance” to obtain the optimal structure; the second is structural stability, that is, whether the three-dimensional framework can withstand chemical corrosion and a certain pressure, so that the three-dimensional effect is not fail during tableting and electrochemical cycling; the third is the affinity with lithium metal, which can reduce the nucleation energy of lithium deposition and achieve the effect of "induced uniform deposition". Therefore, how to develop a frame with adjustable structure, stable performance and good pro-lithium is the main challenge in the three-dimensional design of lithium metal.
In response to this problem, the team led by Professor Yu Shuhong of the University of Science and Technology of China on the basis of the biomimetic artificial wood developed by the research group (Science Advances 2018, 4(8), eaat7223), followed by the treatment to obtain the low curvature and high energy of the imitation wood lithium negative electrode. The authors carbonized the obtained resin-based bionic artificial wood and modified the upper layer of uniformly distributed Sn/Ni alloy nanoparticles. The obtained carbon skeleton not only has an oriented pore structure with adjustable dimensions, but also has good pro-lithiation and induced deposition effects.
In the ice crystal induced self-assembly process, by controlling the initial temperature of the cold stage, the degree of ice crystal nucleation and growth can be controlled, thereby affecting the subsequent vertical channel size. The researchers found that the thermally cured sample, after carbonization, had a clear size reduction factor. In this way, a clear relationship of "freezing parameters—final channel size" is established, thereby achieving controllability of the channel size.
After charging the battery and after a certain number of cycles, the researchers removed half or all of the lithium in the carbon skeleton and found that the pore structure remained very good, and the alloy nano-nucleation sites on the pores were clearly visible. This proves that the wood-like low-curvature negative electrode skeleton has sufficient mechanical strength and good stability.
In this work, the researchers obtained a series of low-curvity high-energy lithium anodes with good dimensional adjustability and microstructure stability through ice crystal induced self-assembly, heat curing, carbonization, electroplating and lithium enrichment (CHVC). The biomimetic structure has a significant effect in improving lithium metal cycle performance, improving stability, reducing polarization, and suppressing volume expansion. The idea of bionic structure design and the idea of pro-lithium modification in this work will help promote the promotion and application of lithium metal anodes in the future.
Edited by Suzhou Yacoo Science Co., Ltd.