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South Korea has developed a "palm tree"-like copper dendrite that improves battery electrochemical performance
2019-05-17
来源：转载自第三方
With the rapid development of the electric vehicle industry, the "high-capacity" standard for batteries is also constantly improving. Lithium batteries with lithium metal as the negative electrode have a capacity potential 10 times higher than traditional lithium ion batteries, but there are potential safety hazards. The root cause of this is lithium dendrites. Today, Xiaobian wants to say that it is not a dendritic lithium dendrite that everyone can avoid, but a copper dendrite that grows into a "palm tree" shape. It is said that this "palm tree"-like copper dendrite can grow in 5 minutes and also improve the electrochemical performance of the battery.
What is dendritic
In some lithium batteries with poor design or quality, overcharging will lead to lithium dendrites, and over-discharge will lead to copper dendrites, which will cause problems such as short-circuit and malfunction of the lithium battery. Dendrites are lithium batteries that cannot be embedded with more lithium ions, causing lithium ions to precipitate as metallic lithium on the surface of the negative electrode, causing dendritic lithium. The dendrites can be burned when they encounter air, which is very dangerous.
Formation of "palm tree" shaped copper dendrites
Recently, the Minyang Yang research group of the Korea Institute of Science and Technology (KAIST) published an article in Adv. Energy Mater. They prepared a nano-palm copper by simple electrodeposition using bromide as a unique anisotropic growth catalyst. Dendritic @Fe2O3 lithium ion battery anode. They also revealed the growth mechanism of copper nanostructures under different conditions, improved the electrochemical kinetics of the battery, and achieved excellent energy storage performance.
Using a copper mesh as an electrode, in a mixed electrolyte composed of CuSO4, NaBr and H2SO4, a voltage of −0.9 to −1.8 V is applied for 200 to 300 seconds, and a length of 2 to 50 μm and a diameter of less than 90 nm can be obtained. High ultra-fine copper dendrites with regular angles of ~60°. From the photos, it is indeed like the leaves of palm trees. So how is this particular structure formed?
In an electrolyte in which no bromide ions are present, a structure of copper dendrites hardly occurs. After adding a certain concentration of bromide ions, Br- is easily adsorbed on the surface of copper (110) to form CuBr; since CuBr can promote the growth of copper, the anisotropy of CuBr directly leads to the anisotropic growth of copper. Therefore, copper continues to grow "branches" along the [110] plane, and grows "leaves" along the [011] and [101] planes, and the angles are approximately equal to 60°.
Following this line of thinking, chloride ions can also aid in the growth of dendritic copper. However, depending on the reaction potential, the adsorption tendency of bromine is greater than that of chlorine. This indicates that bromine promotes the anisotropic growth of copper more than chlorine, resulting in a thinner and longer nanostructure of palm tree copper.
Subsequently, the researchers used linear sweep voltammetry (LSV) and scanning electron microscopy to verify the conjecture. After the addition of bromide ions, a reduction peak was observed at δV curve at −0.3 V, resulting from the electroreduction of CuBr deposits at low deposition voltages. At the same time, the increased current of the LSV curve over the entire voltage range is attributed to the catalysis of Br ions.
The researchers used electrodeposition to uniformly modify a layer of Fe2O3 on the surface of "palm tree" copper dendrites, and verified its electrochemical performance as a negative electrode material for lithium ion batteries. When the current density is 100 mA g-1 (0.1 C), the specific capacity of the electrode can reach 919.5 mAh g-1; after 10 A g-1 (only 5 minutes for full charge), after 500 cycles of high-speed charge and discharge The specific capacity is still 630 mAh g-1. In addition, the electrode can also control the formation of the SEI by changing the interface properties, thereby improving the coulombic efficiency of the first cycle, and further development in practical applications.
The method expands the preparation method of the lithium ion battery electrode, and is expected to be extended to the preparation of various metal composite electrodes, and is applied to various energy storage, catalysis, environmental fields, such as supercapacitors, fuel cells, electrocatalytic reactions, gas sensors, etc. , has good universality.
Edited by Suzhou Yacoo Science Co., Ltd.
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