There are some who argue that the battery technology ruins all the environmental benefit

I have never seen this argument substantiated for the type of battery used in the Prius (nickel metal hydride). Do you have any citations or references for this statement? I know the issues with lead and NiCd of course - but they are not and never have been used in the Prius (beyond a single battery, like any other car). NiMH seems environmentally quite benign and is classified as non-hazardous waste. Has a proper life-cycle costs analysis actually found the production costs (mining) per unit outweigh the benefits?