All my materials are here, I just spent a few hours reading about lithium sulfate aqueous electrolytes in AC/AC symmetric super-capacitors. With the addition of potassium iodide they can actually perform as well as exotic organic electrolytes in EDLC super-capacitors.(in energy density not voltage potential)

This is significant as if the K+ cation conductivity is high enough in the neutral aqueous electrolytes they are almost perfect for potassium sulfur batteries. The benefit being poly-sulfides are insoluble in water which will keep them in the cathode where they belong and solve the issues that have plagued lithium sulfur batteries for so long. As the poly sulfides migrate to the anode they cause irreversible capacity fade.

The problem with aqueous electrolytes is that they are limited to around 1.2 volts per cell when they are highly basic or acidic, (exception is lead acid) however being that potassium sulfate or lithium sulfate is pH neutral the cells can operate up to 1.9 volts. Potassium Sulfur batteries are limited to 2.2 volts anyway with any noticeable capacity starting at around 1.9 volts.

One noticable problem is that K2S in the presence of water will form a lewis acid and KOH will be evolved however basic aqueous electrolyte at the cathode does not cause a problem, the evolution of oxygen at the anode is really what limits most aqueous electrolytes to around 1.2 volts.

The first step however is to synthesize potassium sulfide using activated carbon to absorb a saturated solution of potassium sulfate and water then drying in the vacuum oven. This will allow all potassium sulfide evolved from heating to be kept deeply in the pores of the activated carbon increasing conductivity between the insulating sulfur that will evolve upon charging and the carbon backbone that conducts electrons.

This will then be placed in a crucible and heated with a propane torch for 30 minutes. Carbon monoxide and carbon dioxide will evolve so this should be done outside.