Flexible solid-state battery discovery could bring up to 86% energy density increase

Solid-state batteries are gradually getting out of the research phase and into prototypes and low-volume production lines.

A number of major companies like CATL, Toyota, Samsung, BYD, Mercedes, and others, have pegged 2027 as the pivotal moment when they will release their first production electric vehicles with true solid-state batteries.

This means a solid electrolyte, unlike the hybrid semi solid-state solutions in cars like the NIO ET7 with a 95% solid and 5% liquid electrolyte. The all-solid-state batteries announced so far offer energy density of about 400 Wh/kg, with theoretical potential to hit 500 Wh/kg. That's more than double the density of the most popular LFP batteries that are in everything from mass market EVs, to the popular Anker Solix power station that is currently available at more than 50% off in the Amazon Prime Big Deal list.

Besides doubling the range on a charge in the same footprint, solid-state batteries are also inherently safer as they come with less reactive components compared to those with flammable liquid electrolyte. A true solid -state battery, however, is rather expensive, as the electrolyte has to be fused with the electrode under high pressure and temperature, resulting in weaker contact between the layers, and diminishing the lithium-ion transportation efficiency.

This prevents solid-state batteries from realizing their full potential, so metal researchers from the Chinese Academy of Sciences have developed a breakthrough solid-state battery electrolyte solution.

They took the "solid" out of the solid-state electrolyte by basing it on a flexible polymer that features ethoxy groups and active short sulfur chains designed to increase ion conductivity and fuse to the cathode on a molecular scale.

The resulting polymer electrolyte in a composite cathode not only increased the solid-state cell's energy density by up to 86% due to the decreased transfer resistance, but can also bend. In fact, the flexible solid-state battery system can withstand 20,000 bending motions, advancing its impact resistance and safety profile further than conventional sulfide solid-state batteries like the ones that Samsung or Toyota are preparing to commercialize in 2027.

Such an energy density increase would essentially mean that the Mercedes EQS prototype with a true solid-state battery that currently undergoes range testing may be able to cover more than 1,300 miles on a single charge. What's more, a solid-state battery with a flexible polymer electrolyte would increase the lifespan and safety of electric vehicles if it can be produced at enough scale to lower the manufacturing costs to a competitive level.