Batteries are useful for convenience and necessity. They are inherently inefficient and can not make 'alternative' power sources such as solar panels or windmills competitive with hydrocarbon, hydro, and nuclear power sources.
The batteries that Prof. Sadoway and friends are working on function at temperatures between 350 C to 1000 C. So the 1st questions u should ask are: how are those high temperatures generated and what is required to prevent those temperatures and the materials from behaving badly with their environments (environment including the user, containers, etc). The answers eat into efficiency rather dramatically.
The materials that the batteries are composed of should also give u a clue as to their inefficiency. One electrode is comprised of alkali or alkaline earth metals (stuff like sodium, potassium, magnesium and calcium). Those metals are generally found very strongly bound in silicate and carbonate minerals. It takes a great deal of energy to separate those metals from rocks. That's part of the reason why greenies have their eyes on the cement industry. Cement companies burn a lot of natural gas to cook CaCO3 down to CaO. Reducing the CaO to Ca is much more energy intensive.
One could argue that there is a lot of sodium and magnesium in seawater and it is cheap but removing all the water and then reducing the NaCl and MgSO4 to the metals is again very energy intensive.
I don't have any problem with batteries but anybody that pretends they are more efficient than other readily available power sources or environmentally friendly is either extremely ignorant or dishonest (I'm not stating Sadoway fits in that realm just in case any folks with reading comprehension problems might think so.). I do find it amazing that Time magazine couldn't find a few 100000 people more influential than Prof Sadoway.
