NiMH vs. NiZn

[crx_rogus]

Does anyone have any views on NiMH vs. NiZn? The latter's described as about 1/3rd again more power dense mass-wise vs. NiMH, and the cell voltage is 1.6V vs. 1.2 for NiMH (4:3). The new NiZn AAs at least are rated 1.5AH vs. up about 2.4Ah for some NiMH AAs, but 1.5/2.4 x 1.6/1.2 = 83% of a 2.4Ah NiMH's Wh, assuming equivalent voltage discharge slopes. Can't guess if NiZn Ah ratings will climb as supermarket-grade NiMH AA capacities have, since HEV cells and supermarket-grade cells do not really compare.

I wouldn't bring up AAs here if it wasn't for the fact that:
1) NiZn is supposedly more tolerant of high sustained charge and discharge rates
2) apparently the company making the NiZn cells has already modified a MkII Prius to use high-capacity prismatic versions
3) they're another nickel-based chemistry, so I'm wondering if they have the same rugged and non-linear characteristics of other nickel-based batteries

I also wonder what exotic other elements the cells rely on, as nickel and zinc are not exactly elements Bolivia or China have a future near-monopoly on.

Just curious, seems interesting.

[MN Driver]

I've done a great deal of reading about Nickel-Zinc and it has actually been around for quite a long time. People who used them in electric cars about a decade ago had failures, which were attributed to separator puncture failure as the zinc dendrites are formed as the zinc doesn't migrate back to the cathode easily, which has been the biggest challenge from the chemistry. I've also read about charging, they need to be charged at a specific rate between C and .5C, they can't take an overcharge like NiMh and NiCd either which makes them unsuitable for a hybrid car and in an electric car you would need to have a very high amperage 240 volt outlet to charge them in two hours if you wanted decent range for the car. I remember searching through the EV Album site at NiZn cars and there was no example where I read their blog where he was having issues with them getting too hot during discharge. Based on everything that I've read, they are far from ideal and no longer 'cheap' relative to other chemistries anymore. I don't even know if there is any accessibility to them anymore in prismatic form.

We currently don't get lithium from Bolivia and its cheap enough as it is and not the primary cost driver of lithium cells, especially Lithium Iron Phosphate which actually has far less lithium than you would think inside it. In 2008 Chile was the largest producer of lithium in terms of mining production, followed by Austrailia, China, Argentina, Canada, the list goes on. Production for Bolivia was zero. Although the large scale Lithium production cells aren't being produced here, the US gets 63% of it from Chile, 35% from Argentina, 1% from China, and 1% from all other sources.

Source: USGS Minerals Information: Lithium