Solid State batteries, how far are we?
By: Rohan Kadamb
Tags: Technology, Battery, Chemistry, Science, Technology News

Solid-state batteries are an emerging trend for next-generation traction batteries, as they offer high performance and safety at low cost. Additionally, they have low flammability, higher electrochemical stability, higher potential cathodes, and higher energy density as compared to liquid electrolyte batteries.

The main difference between conventional lithium ion and lead acid batteries as compared to Solid state batteries is that of the electrodes. Solid-state batteries use both solid electrodes and electrolytes while lithium ion and lead acid batteries use liquid electrodes.

Currently, there are more than 25 types of solid-state electrolytes, such as oxides, sulfides, phosphates, polyethers, polyesters, nitrile-based, polysiloxane, polyurethane, etc.

Liquid electrolyte vs. solid state batteries

WHY SOLID STATE BATTERIES?

Solid-state batteries are available in much smaller sizes as compared to liquid lithium-ion batteries, which means that solid state batteries can be much smaller in size and contain much more charge capacity. This ultimately means that a Solid state battery, the same size as that of an average smartphone battery in 2020 could power the phone for up to a week!

In addition to this, Solid state batteries have a higher thermal stability, lower self discharge, high conductivity over a broad range of temperatures, higher tolerance and a much higher charge density than Lithium ion or lead acid batteries, which makes them a prominent candidate for Electric vehicles as they are thermally stable over a high range of temperatures and can be charged much faster, as Solid-state batteries do not contain a liquid electrolyte, which gets heated due to fast charging, and thus, solid-state batteries provide high safety as compared to liquid lithium-ion batteries. The fast charging feature of solid-state batteries is one of the most significant factors leading to the higher uptake of electric vehicles powered by solid-state batteries in the near future.

CHALLENGES FACED

The physical limitations of solid electrolytes make them inherently less conductive than their liquid counterparts due to the slowed ion diffusion through the solid medium. The ion conduction of liquid electrolyte is typically on the order of 10–1 S cm-1, while the most conductive solid electrolytes have reported conductivities on the order of 10–3 S cm-1 at room temperature. The ion conductivity of solid electrolytes is thermally dependent and increases with temperature, meaning they are well suited for high temperature applications. However, conductivity also decreases with temperature meaning the energy density of solid-state batteries decreases significantly in cold conditions. Typically, the way to overcome this challenge is to introduce a small amount of liquid electrolyte, this, however, defeats the purpose of using a solid electrolyte in the first place.

These challenges faced by the solid state batteries must be overcome by major scientific breakthroughs and research before solid state batteries can be made commercially available at affordable costs and before they can become as common as liquid lithium ion batteries.

The technology is improving continuously and we are seeing major breakthroughs almost everyday, however it would be safe to say that solid state batteries will not be commercially available for the next 10 years.