The recipe for engineering faster-charging batteries requires some salt, according to researchers from Imperial College London. A prototype composed of polymers and saltwater has been demonstrated to charge and discharge in seconds.

The use of low-cost plastics and non-toxic, water-based electrolytes could lead to the development of easily recyclable batteries. The polymer materials take up and release positive or negative ions from saltwater, As the battery is charged, the positive electrode (left) changes from deep blue to transparent, and the negative electrode (right) changes from green through brown to steel grey. Source: Imperial College Londonquickly and reversibly without degrading. Polar material-based side chains are linked to the conducting polymers, forming electrodes with high affinity to water. A two-electrode cell constructed by the research team delivered output voltages of up to 1.4 V with high redox-stability.

The flexible polymer expands and contracts as the battery charges and discharges, eliminating the need for additives. The device also signals its state of charge by changing color during the charging process.

While the saltwater system holds less charge than conventional lithium-ion batteries, the inexpensive and eco-friendly battery could find use in applications where energy needs to be exchanged quickly and the batteries can be large, such as when regenerative energy from car braking is used moments later to accelerate the vehicle. The technology could also serve to quickly store and release the intermittent energy supplied by solar and wind energy systems.