Alternative Energy with Efficient, Low-cost Mixing Entropy Battery

A team of Stanford engineers has developed an efficient battery that can convert salinity gradient power (a.k.a. “blue energy”) into electricity using low-cost, non-toxic electrode materials. This invention generates energy using the same principle as the mixing electron battery (“MEB”, described in Stanford Docket S10-123). However, it improves net power output because it employs low-cost electrode materials that do not require the initial energy investment of a charge step. This battery could be used to generate energy in any natural system that is alternately flushed with freshwater and saline water (e.g., desalination facilities, estuaries, or ships that move between ocean and freshwater environments). It has an energy potential roughly equivalent of the energy required to operate a wastewater treatment plant.

Schematic and typical cycle representing the working mechanism of the mixing entropy battery using a Prussian Blue (PB) cationic electrode and a polypyrrole (PPy) anionic electrode.

Stage of Research
The inventors have tested 3cm² electrodes in an MEB and produced energy during both freshwater flushes and wastewater flushes while eliminating the charge step and upfront energy investment of previous MEBs. The MEB had over 93% capacity retention over 50 cycles of operation. Furthermore, the inventors have built a prototype of a larger scale (10 cm²) electrode.