The Chinese scientists have found an innovative solution to the problem by transforming rusty stainless steel mesh into electrodes. With the process the rust is converted directly into a compact layer, in a form that has a grid structure allowing the structure to store potassium ions. With this corroded mesh is dipped into a solution of potassium ferrocyanide. This solution dissolves iron, chromium, and nickel ions out of the rust layer. These combine with ferricyanide ions into the complex salt known as Prussian blue, which is deposited onto the surface of the mesh as scaffold-like nanocubes. Potassium ions can easily and rapidly be stored in and released from these structures.
By adding a coating of reduced graphite oxide (via a dip-coating technique) this increases the conductivity and stability during charge and discharge cycles. The oxide inhibits clumping and detachment of the active material and helps to increase the conductivity. The process can produce electrodes with outstanding electrochemical properties, meaning they are ideal for potassium-ion batteries.
The focus on potassium ion batteries is part of the quest to find alternatives to lithium ion batteries. Lithium ion batteries are the most common type of battery in consumer electronics. These based on the displacement of lithium ions. When charging, the ions move toward the graphite electrode to be stored between the layers of carbon. When discharging, they are released.
One reason for looking at alternatives is because lithium is expensive and reserves are limited. The main alternative, up until now, has been sodium ion batteries. The potassium battery has certain advantages over similar lithium batteries in that the cell design is simple and both the material and the fabrication procedure are cheaper.
With the latest Chinese process, potassium ion batteries are emerging as a viable alternative. Key to this development is the recycling of metal mesh. With this, lead researcher Dr. Xin-Bo Zhang, from the Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, notes: “Conversion into electrodes could develop into a more ecologically and economically sensible form of recycling.”
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The research has been reported to the journal Angewandte Chemie. The research paper is titled “Transformation of Rusty Stainless-Steel Meshes into Stable, Low-Cost, and Binder-Free Cathodes for High-Performance Potassium-Ion Batteries.”
