Rejected stainless steel mesh from filters and sieves can be reclaimed in a furnace, but the process is time- and cost-intensive. Researchers in China have developed a more sustainable means of recycling these materials: convert them into electrodes suitable for potassium ion batteries.

The corroded mesh is dipped into a solution of potassium ferrocyanide (yellow prussiate of potash, known as a fining agent for wine), which dissolves iron, chromium, and nickel ions out of the rust layer. These combine with ferricyanide ions into the complex salt known as Prussian blue, a dark blue pigment that 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.(Source: Chinese Academy of Sciences)

A dip-coating process is then used to deposit a layer of graphene oxide (oxidized graphite layers) which nestles tightly onto the nanocubes. Subsequent reduction converts the graphene oxide to reduced graphene oxide (RGO), which consists of layers of graphite with isolated oxygen atoms. The RGO coating inhibits clumping and detachment of the active material, significantly increases conductivity, and opens ultrafast electron-transport pathways.

In tests, coin cells made with these new electrodes demonstrate excellent capacity, discharge voltages, rate capability, and outstanding cycle stability. Because the inexpensive, binder-free electrodes are very flexible, they are highly suitable for use in flexible electronic devices.

Scientists from the Chinese Academy of Sciences and Jilin University conducted this research.