The best batteries are lithium ion batteries. In these batteries, lithium ions are collected in one part of the battery, where they are held in place at the anode end by metal atoms, in the charged state. Pulling electricity out of the battery involves the lithium ions migrating away from the anode toward the cathode via a liquid medium.
The big problem with these batteries, in my view, is that the metal anode is made using a lot of cobalt, and to get cobalt, you have to, well, kill people.
A newer kind of battery uses sulfur to hold the ions at the anode. Sulfur is better in some ways because fewer atoms of sulfur can hold more ions. The sulfur is combined with a carbon (graphite usually, in current experimental designs that work best). The battery is lighter, hold more energy, and does not require maintaining a vast Central African Unending War, like Cobalt does.
But, the sulfur tends to combine with the carbon in the graphite, forming poly-sulfides, which migrate out into the matrix, and even to the cathode, and muck up the battery. For this reason, sulfur-based lithium ion batteries can only be charged and discharged a limited number of times.
There are uses for batteries that you only use a few times then toss. But, these sulfur batteries may eventually be made to work longer. There are tweaks to the anode (using different forms of carbon, or coating the carbon) and to the matrix (a version that allows highly efficient passage of lithium ions but that is repellent to poly-sulfides).
Battery experts are hopeful that there is a future in lithium-sulfer batteries.