Canada

It’s mostly improved chemistries and manufacturing processes. What we call “lithium ion batteries” aren’t the same today as they were even just in the 2010s. We have newer chemistries (lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium manganese cobalt, lithium nickel cobalt aluminium oxide, etc.), newer solid state battery technologies, better cell packaging, and overall better manufacturing processes.

Will these cells still have 100% capacity after 15 years? Likely not — but even if they’re only at 80 - 90% of their original capacity that’s still quite a lot of driving capacity for most EVs.

Here is one non-peer reviewed study on Tesla battery deterioration, which shows that at the ~10 year mark, battery capacity loss is at around 17%. However, it’s worth noting that cars that hit the 8 through 10 year marks were more likely using older battery chemistry and construction techniques; newer cars at the 7 year mark only showed a roughly 7% battery capacity loss.

Time will tell, but the situation is significantly less bleak than naysayers (and the oil industry) want you to believe.