By coating the iron sulfide cathodes in polymers, a research team was able to create transition-metal sulfide-based lithium batteries with stable cycling and high safety. After 300 cycles, a lithium carbide iron disulfide pouch cell retained 72.0% capacity with no capacity degradation after 100 cycles.
Put that on a phone and the battery will degrade almost 30% in one year… seems a lot tbh.
As a point of reference, Google says that somewhere between 500-2000 cycles you can expect a regular lithium battery to degrade to 80%. So this is worse, but in the ballpark. Seems reasonable for a research prototype to be a little worse than a commercial product that’s had years to become highly optimized.