A potassium-ion battery or K-ion battery (abbreviated as KIB) is a type of battery and analogue to lithium-ion batteries, using potassium ions for charge transfer instead of lithium ions.

It was invented by the Iranian/American chemist Ali Eftekhari (President of the American Nano Society) in 2004.

The prototype device used a potassium anode and a Prussian blue compound as the cathode material for its high electrochemical stability. The prototype was successfully used for more than 500 cycles. A recent review showed currently that several pragmatic materials have been successfully used as the anode and cathode for the new generations of potassium-ion batteries. For example, the conventional anode material graphite has been shown that it can be used as an anode in a potassium-ion battery.

In 2024, Group1, created Kristonite for the cathode.

After the invention of potassium-ion battery with the prototype device, researchers have increasingly been focusing on enhancing the specific capacity and cycling performance with the application of new materials to electrodes (anode and cathode) and electrolyte.

A general picture of the material used for potassium-ion battery can be found as follows:

Besides the original Prussian blue cathode and its analogs, researches on cathode part of potassium ion battery focus on engineering.

Kristonite is a 4V cathode material — in the class of potassium prussian white (KPW) materials.