Featured A comparison between nickel metal hydride and lithium ion Toyota hybrid batteries

lion seems to be doing pretty well. the track record here is now 9 years, and longer outside n/a.
i suspect lion batteries are or will soon be cheaper than nimh as usage changes

 

The demand for NiMH will get a lot lower so Li-Ion will become cheaper.
The technology is a lot more mature than 10 years ago. I believe that Toyota has dialed both chemistries in pretty well for their vehicles.

 

The simple answer to "Which one is better" probably is:
Whichever one the car was DESIGNED TO USE.
Because the electrical characteristics are different enough that they likely won't be interchangeable.......and achieve the same performance.

 

Less weight and more power, sounds good to me. If these guys are still around when our 2 Gen needs it's third HV Battery, it's gonna get one of these.
Prius Lithium upgrade pack - 14 blocks– NexPower Energy

I'll let the "techie type's," argue about the "pro's and con's." The market place will shake it out.