* Size is important, because they need to be stored and maintained somewhere. The larger the energy storage, the more infrastructure required.

* Weight typically scales cost (the heavier it is the more it costs). If it really weighs a lot, you need to reinforce the ground too.

* Efficiency in charging and discharging. You also need to monitor the state of each cell carefully.

Li-ion capacity fall off is a fixed percentage per year, so when your car hits 80% of original capacity in ten years, its battery pack can just be used for another ten years. It’ll provide > 64% capacity at the end of that (grid workloads are less stressful than driving workloads).

So, the alternative battery technology has to cost less than the cost difference between refurbishing and recycling old car batteries. That delta might be negative.