18650 battery 1800 mah.Energy Storage Institute has made phased progress in lithium metal battery research

　　Researchers from the Qingdao Energy Storage Industry Technology Research Institute optimized the electrolyte for lithium metal batteries and designed a double-salt electrolyte containing additives, a modified polyvinylene carbonate-based high-voltage polymer electrolyte, and a high-lithium-ion electrolyte that combines rigidity and flexibility. The composite electrolyte with ion mobility coefficient has good guiding significance for the development of high-energy lithium metal secondary batteries.

　　1Research background

　　With economic globalization and the rapid development of science and technology, humankind's demand for energy is increasing day by day. Especially with the booming development of electric vehicles and mobile electronic devices in recent years, high energy density energy storage materials have become the focus of scientific research. Although the traditional intercalated lithium-ion battery using graphite as the negative electrode material occupies an important position in the electronic equipment product market, its energy density is close to its upper limit and is gradually unable to meet consumer demand. Compared with intercalated lithium-ion batteries, lithium metal batteries (such as Li-S, Li-O2 and other battery systems) that use metallic lithium directly as the negative electrode have unique advantages in energy density and have become a recent research topic. Hotspot. However, metallic lithium anodes present many practical problems that need to be solved during their use. First of all, it has extremely high electrochemical reduction performance and easily reacts with the electrolyte during the charge and discharge process, consuming a large amount of active lithium and electrolyte. Secondly, uncontrollable dendrite growth and electrode volume changes, as well as the gradual accumulation of side reaction products and "dead lithium" are always serious problems faced by metallic lithium anodes.

　　2Research progress

　　With the deepening of lithium metal anode protection work, researchers are paying more and more attention to the failure mechanism caused by lithium dendrites and "dead lithium" in lithium metal batteries. However, due to their similar morphologies, how to observe and distinguish the two is A very challenging topic, and this issue is extremely important for understanding the battery failure mechanism and predicting the cycle life of lithium metal batteries. In order to describe the distribution of active lithium species on the surface of lithium metal anodes and distinguish lithium dendrites from "dead lithium", researchers from the Qingdao Energy Storage Institute designed a 9,10-dimethyl Based on (DMA) fluorescent probe, this task was completed through traditional visible optical means. This technology has been recognized by international colleagues, and a scientific research paper titled "Fluorescence Probing of Active Lithium Distribution for Lithium Metal Anode" was written on the relevant results ( Angewandte Chemie International Edition, 2019, DOI: 10.1002/anie.201900105).

　　3 Research significance

　　After the battery undergoes charge and discharge cycles, by-products may accumulate on the surface of the metallic lithium anode (a large amount of by-product coating will deactivate active lithium, that is, produce "dead lithium"). Therefore, the researchers evenly coated the fluorescent small molecule DMA on the surface of lithium metal after cycling. Since DMA can undergo a fluorescence quenching reaction with active lithium and remain stable on the surface of the by-products, it can characterize the distribution of active lithium on the anode surface of lithium-ion batteries and its by-products in various electrolytes, which is the basis of the electrolyte of lithium-ion batteries. The selection provides an important reference basis; during the lithium deposition and dissolution process, the accumulation of by-products is visually and semi-quantitatively identified, which can link the performance attenuation of the battery to the amount of by-products to prevent and control battery performance failure. Early warning: The positions of lithium dendrites and "dead lithium" can be clearly identified on the surface of the lithium anode after cycling, allowing the cause analysis of failed batteries to be performed. This technology provides an idea and direction for the analysis of the failure mechanism of lithium metal batteries.

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