Those hot molten batteries might be good for large, stationary situations. If you get enough size, the surface area radiating heat becomes small for the volume of battery, keeping the losses to keep it hot low.
On the original topic... It took me quite a while to get the Ni-Mn chemistry going. In addition to my new chemistries, there are hidden details and there has never been an instructional book (until my recent and still preliminary efforts) to teach details of how to make batteries to the uninitiated.
I gave up on sealed "dry" cells (for now) and went for flooded, vented cells.
Some other key points:
* At pH 7 with salt electrolyte, as I was trying to do (KCl, eg from compounding pharmacies), Pourbaix diagrams show that many substances become soluble, which is bad for longevity of electrodes. pH 14 (totally alkaline) is better, but not ideal. Ideal for most substances is perhaps pH 10 or 11 to 13. You can get pH 12.3 with the neutral KCl salt and some calcium hydroxide. Calcium hydroxide is only slightly soluble, so it doesn't raise the pH to 14, only to 12. You can add enough to have an undissolved reserve of it. Lower pHes than 14 give higher voltages from the same chemicals, and they're much safer to handle.
* All common metals oxidize away rapidly in the positive electrode. (Nickel alone works, at pH 14 only.) That's the nowhere stated reason why carbon rods are used in standard dry cells instead of wires. After 2 or 3 years I figured this out and I created "Grafpoxy", 50:50 wt% graphite powder (eg, art supply stores) and epoxy to make a conductive epoxy, which can be made into various forms/shapes. I'm still experimenting with these.
* With the high voltage of manganese in the negative electrode (-1.56 volts at pH 14 going to -1.18 at lower pHes), most metals won't work as current collectors - they bubble hydrogen even if the electrode chemicals don't. The things that work for NiFe, NiCd, and NiMH don't work for NiMn. Only zinc works. This also took me a couple of years to figure out. "Zincate solution" (eg, from Caswell Plating) seems to be a good way to plate zinc onto aluminum. This has given me the best results to date. I'm still experimenting.
* The Mn negative chemical will bubble hydrogen and discharge itself unless an additive is used to raise its hydrogen overvoltage. The additive I came up with works well: 1% stibnite (antimony sulfide, Sb2S3). MnO2 powder (an overdischarged form) can be had at pottery supply stores, where many oxides, carbonates and sulphates are used to make colored glazes. Stibnite comes, eg, from pyrotechnic supplies.
* Nickel (nickel [oxy]hydroxide) probably isn't the best positive electrode. I'm presently trying out two things: the first is MnO2 with graphite powder to enhance conductivity (the 'ideal' form is easily salvaged from standard non-alkaline dry cells), charging it to potassium permanganate. It's chelated with Lemon Fresh Sunlight dishsoap (which has the stable sulfonates) to prevent migration of the slightly soluble permanganate. This has good voltage and moves three electrons/ions per reaction instead of nickel's one.
* The second thing I'm trying is Nickel Manganate, a substance about which little info seems to exist, but which is probably insoluble. I make this by torching nickel oxide (pottery) or hydroxide (eg, Palm Inc) and manganese dioxide (pottery) to red hot in a stainless steel pot. The torch blows a lot of it out... must be a better way.
Potentially these chemistries should give at least as high an energy density as lithium ion, and from dirt cheap ingredients and supplies.
A battery company may start making nickel-manganese alkaline batteries (pH 14, KOH) on an existing assembly line - I've contacted them but nothing's arranged yet.
I'm still trying to improve the very low conductivities of my own test cells and come up with better DIY battery constructions. I've indicated some supply sources above because some of these things, while not rare, may be hard to locate. I don't dare give a link to my preliminary instruction book and newsletter updates. If I knew of anywhere else you might find battery making instructions I'd mention it.
