Yes the 20 year shelf life batteries were indeed zinc carbon cells with the electrolyte in a sepperate capsule that was fractured by twisting.

Obsolete due to low energy density, as posted above.

Lithium cells have an advertised shelf life of about 15 years, and would probably last 20 years in practice.

Most types of small rechargeable cell only reliably last a few years in storage.

Lead acid batteries if dry and sealed with the acid stored in bottles last some years in storage.

Crude, non portable, lead acid batteries are very easy to make and the materials store indefinatly.
Once made, the working life is very long and the capacity improves with each cycle.
The capacity is however very small in relation to the weight and bulk.
I once made 2 lead acid cells, each in a gallon glass jar. Each had a capacity of about 2 amp/hours, certainly potentialy useful in a long term emergency, but remember that the energy stored in a gallon glass jar, was only slightly more than that contained in a single AA cell !
So not exactly portable, but 6 such such home made cells could provide very limited lighting in a home every night, being charged by a PV module in the day.