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Solid state batteries have been available for niche applications for a number of years. However, we are seeing the functionality of solid state batteries improving to the point where they are becoming more useful for consumer applications.

Solid state batteries differ from liquid electrolyte based batteries in that the liquid electrolyte and polymer separator are replaced with a solid electrolyte, creating a more stable battery that can hold more energy in the same volume. 

This move from liquid to solid brings a range of benefits including faster and more efficient charging, a non-flammable construction and a smaller battery volume. Also, because you do not need to be concerned about containing a liquid, you can produce the battery in different shapes making them more suitable for small devices and sensors.

As the world moves to being more connected through the Internet of Things (IoT) approach, different requirements are being created for battery technologies. This, in conjunction with the wider adoption of energy harvesting such as solar, thermal and vibration, has opened-up the proliferation of sensor-based end nodes, wirelessly monitoring and sending data back to centralised points. Most energy harvesting power sources are intermittent, so they need energy storage to power the node when the energy harvesting is not available.

Solid state batteries are the ideal solution to work in conjunction with the energy harvesting for several reasons: they are up to 50% more energy dense than existing batteries, so they can be in a small form factor which enables smaller end sensor nodes to be designed; they have a tenth of the leakage current of coin cells, enabling them to capture small currents and to hold their charge for longer; and, finally, they have an expected longer life span of up to 10 years, 4x that of coin batteries, enabling the batteries to last the lifespan of the end device without having to be changed.

Solid state batteries address the key energy provision challenges faced by the miniaturisation and proliferation of IoT devices – they also in the future have the ability to bring key benefits to automotive and consumer devices.