The revolution of solid-state batteries

The lithium-ion battery sector is constantly evolving, with daily research aimed at improving battery performance, range, power and charge times.
Among recent technologies, solid-state batteries represent a major development for the future of electric mobility.
These batteries use a solid electrolyte instead of the liquid electrolyte of traditional lithium-ion batteries.

1. Operating principle of Standard LFP vs Solid-State LFP batteries

LiFePo4 / LFP batteries: These consist of two electrodes (cathode and anode) separated by a liquid electrolyte. Lithium-ion moves between the electrodes during charging and discharging.
Solid-state LiFePo4 / LFP batteries: Replace the liquid electrolyte with a solid electrolyte (ceramic or polymer), and use a pure lithium metal anode. This design eliminates the graphite structure of the anode, thus increasing energy density.

the video below details the operating principles of a solid-state lithium battery.

2. Advantages of solid-state batteries

Increased safety: The absence of flammable liquid electrolyte makes these batteries less prone to short-circuits and the formation of dendrites (lithium build-up) that can damage lithium-ion batteries.
Very low internal resistance : The design of the solid-state electrode results in an internal resistance 2 to 3 times lower than that of a conventional lithium battery.
As a result, battery cells heat up much less during use. The benefits are direct: batteries that don’t heat up much during use degrade much less quickly
For example, our laboratory tests show that when discharged at 3C (20 minutes to fully discharge the LFP Solid State battery), the battery heats up by only 23°C, which is 1/3 of the temperature rise seen on a standard LFP battery.
This resistance to overheating means that power batteries can be designed without the need for internal cell cooling.
Ultra-fast charging : Solid-state batteries can be charged up to four times faster than conventional lithium-ion batteries.
What’s more, they are more resistant to heat, which improves their performance during rapid charging.
Longer service life: Solid-state batteries tend to have a longer service life due to the reduced chemical degradation of solid electrolytes compared with liquid electrolytes.
More specifically, the low temperature rise during use means that cells can be kept at temperatures compatible with a long service life.
As a result, they can withstand more charge-discharge cycles before their capacity degrades significantly.
Higher energy density: In the future, lithium metal in the anode will enable higher energy density than current lithium-ion batteries, resulting in a lighter, more compact battery with greater autonomy.

3. Semi-Solid batteries, roadmap and prospects

Les batteries à l’Etat Solide sont très prometteuses, notamment en termes de sécurité, de performance et de durabilité.

Mais pour parvenir à une production à grande échelle et à coûts maîtrisés, il faudra attendre encore quelques années.
Les enjeux technologiques sont tels qu’un certain nombre d’étapes restent à franchir, notamment en ce qui concerne la durabilité des électrolytes métalliques ou céramiques.

En attendant que les électrolytes solides détrônent les liquides, la recherche se concentre sur une technologie intermédiaire : les batteries semi-solides, avec des électrolytes polymérisés.

Les électrolytes polymérisés (également appelés électrolytes gélifiés) contiennent des conducteurs ioniques tels que les sels de lithium, qui permettent une conductivité ionique beaucoup plus efficace. La structure polymère résiste également à la formation de dendrites, des structures en forme d’aiguilles qui peuvent se former sur l’anode pendant la charge et provoquer des courts-circuits. En outre, les gels sont beaucoup moins volatils que les électrolytes liquides, et donc très difficiles à enflammer.

Although semi-solid-state batteries do not achieve the energy densities and lifetimes expected of solid-state batteries, they offer a medium-term advantage in that they can be manufactured on conventional lithium-ion battery production lines. Just as importantly, they have been tested and are now available on the market. On the other hand, Solid-state cells will be available at a reasonable cost by 2027-2028.

The energy density of semi-solid batteries is currently similar or slightly higher to that of standard LFP batteries, but all the other advantages of solid-state are already there. We can expect this lithium battery technology to gain momentum, with a major evolutionary step towards ever-increasing energy density in the years to come.

The future is already here: the new PowerModule SOLID-STATE product, equipped with semi-solid cells technology is already operational and available :