The modernized society of information and automation has been making continuous progress, and electrochemical energy storage devices have played an important role. Since the 90s of the 20th century, with the commercial application of lithium-ion batteries, lithium-ion batteries have become a part of our lives since the 21st century. Lithium-ion battery portable devices and power vehicles have spread all over the world. However, the cheaper the more commercial products sell, the less expensive lithium resources make the cost of lithium-ion batteries rising in the future. To find an alternative low-cost electrochemical energy storage device has become an urgent problem. The electrochemical properties of potassium and sodium are similar to those of lithium, and the Earth's reserves are abundant. It is the best choice for replacing lithium-ion batteries in the future.
However, the standard electrode potential (-2.71 V, vs SHE.) And the large ionic radius limit make the current energy density and power density of sodium ion battery still coincide with that of lithium ion The battery has a big gap. Potassium's standard electrode potential (-2.93 V, vs SHE.) Is closer to lithium (-3.04 V, vs SHE.). Potassium ions and sodium ions have larger ionic radii than lithium ions, although the energy density is less than lithium ions , But the current research of potassium ion cathode carbon material shows that potassium ion battery has higher power density than sodium and closer to lithium ion battery, and the rate performance is also better. However, at this stage, little research has been done on potassium ion cathode materials. Most of the studies use aqueous solution as the electrolyte and the voltage window is limited. Recently, Professor Lei Yong from Ermna University of Technology in Germany and the research group of Shanghai University collaborated to prepare a low-cost dye nanoparticle: Prussian Blue, which is used as a potassium ion cathode material in the organic Electrolyte, showing the electrochemical properties were described in detail. At the same time, the use of potassium as its cathode material, for the first time matched with high performance potassium-ion battery. The test results show that Prussian blue presents a high discharge platform (3.1 3.4 V) as potassium ion cathode material with a stable reversible specific capacity of 73.8 mAh / g at a charge / discharge rate of 50 mA / g Cycle specific capacity, and very slow degradation rate of only 0.09% per-cycle. At the same time, they analyzed the electrochemical storage mechanism of Prussian blue molecules and found that the framework of the molecular structure is very conducive to the storage and release of potassium ions with larger radius, its main active site in the C-Fe â…¡ / Fe â…¢. Finally, through the positive material and super commercial Polaroid as the anode material, they were the first to match the full potassium-ion battery. The full-battery achieves a reversible maximum capacity of 68.5 mAh at a charge / discharge rate of 100 mA / g / g, and has a long cycle life, which retains 93.4% of the specific capacity after 50 cycles of charge and discharge. For the larger radius of potassium ions, such a breakthrough is commendable.
Low-cost Prussian blue dye as a potassium-based cathode material research and its full battery matching design, making the lithium-ion battery find a better alternative, the research for future potassium ion battery research and commercial applications The broad prospects. This paper has been published online at Advanced Functional Materials (DOI: 10.1002 / adfm.201604307) and is briefly described in the current Back Cover.
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