Further on the materials front: STRUCTURAL BATTERIES
1/400th the energy density of lithium ion, but there are reasons to do this. Durability -- resistant to overcharging and abuse, and monitoring the health of the 'cells' illuminates the strucrual integrity.
The 'cell' constitutes three layers, two electrodes and the electrolyte encased within the structure so the outside surface is insulative for human contact (it won't electrocute you).