"Can calcium replace lithium in a battery?" This is the question that researchers are trying to answer in CalSiumbat. Researchers around the world are looking for a viable alternative to lithium-ion batteries.
Chemists have several reasons to take a closer look at calcium when looking for new battery technologies. Calcium is also much less dangerous than lithium and sodium, but is slightly larger, heavier and slower than lithium and sodium. The biggest problem is therefore moving calcium back and forth between the anode and cathode. Rechargeable lithium-ion batteries have become the dominant power source in various types of consumer electronics and sustainable transportation, from phones to cars. However, with current prices, limited supply of lithium can create challenges in the supply chains due to strongly growing use in various industries. Calcium is the fifth most abundant element in the earth's crust, the third most abundant metallic (cationic) element with good geographical distribution throughout the globe. Thus, potassium has a clear potential to act as a lithium substitute. Sodium and magnesium are other alternatives. Calcium has far less risk than lithium in terms of battery ignition. An important aspect of solid-state battery technology is that it avoids the use of a flammable liquid electrolyte, which increases battery safety. The main challenge in the project, which makes this a high-risk / high-yield project, is to find an optimal solid-state polymer electrolyte that enables reversible calcium insertion / extraction. The project combines various experts with broad and high competence, and the project's objectives will be achieved through advanced synthesis, combined with X-ray examination and electrochemical studies. In summary, Calsiumbat will pave the way for new types of materials in energy storage systems with high energy density (HEDSS), with low environmental footprints, and at low production costs. By opening a new research window within the rapidly expanding Norwegian battery scene, UiO will lay the foundation for demonstrating the first prototype of a calcium battery in Norway.
In the last twenty years worldwide intense research and development efforts are invested by public and private stakeholders (universities, research centres and private companies) to develop new battery technologies beyond lithium. Aprotic sodium-ion batteries (NIB) are, by large, the most widely investigated chemistry alternative to LIB, given the chemical similarity of sodium to lithium, and its relatively small atomic weight. However, multivalent batteries based on Mg, Ca, Al and Zn, etc. have the ability to drive multiple electron exchange for every charge transfer event counterbalances the larger atomic weight compared to both Na and Li. Calcium is a divalent alkaline earth metal with an extraordinarily strong oxidative ability in consideration of the –2.87 V vs SHE (standard hydrogen electrode) redox potential for the Ca2+/Ca couple, to be compared to the -3.04 V vs SHE of the lithium metal electrode. In comparison to other elements under study for battery applications, calcium is the multivalent metal with the most negative redox potential and an ionic radium very similar to Na+, a cation easily intercalated/deintercalated in/from a variety of materials. The main objective of the overall project is to achieve a proof of concept for all-solid state Ca-ion batteries (CIB) with energy density higher than 650 Wh/kg. The ambitious part will be develop a new alloy-type of Ca-Si anode (phase 1) and couple it with a solid polymer electrolyte (PEO based) and a barium-free Prussian Blue (PBs) analogue cathode. Pre-tests with organic electrolyte will be carry out in half-cell configuration and later validated with the solid electrolyte. One work package will be devoted to the in-depth electrochemical reaction mechanism using X-ray Operando techniques. The final device will exhibit a working voltage beyond 4V and will use only not-toxic, cheap and easily scalable battery materials.