Calcium Battery

Calcium batteries are energy storage and delivery technologies (i.e., electro-chemical energy storage) that employ calcium ions (cations), Ca2+, as the active charge carrier in solution as well as in the electrodes (anode and cathode). Calcium (ion) batteries remain an active area of research, with work persisting in the discovery and development of electrodes and electrolytes the enable stable, long-term battery operation.
Calcium batteries are consider a next-generation, or post-Li-ion energy storage system, namely one of the many candidates that may potentially replace lithium-ion technology. Key advantages sought in such post-Li-ion systems is lower cost, earth abundance, higher energy density, and higher power output. There are several benefits to the development and use of calcium batteries. Calcium is the fifth most abundant mineral in the Earth's crust, and the most abundant alkaline earth metal, and the third most abundant metal after aluminum (Al) and iron (Fe). A calcium metal anode offers a higher volumetric and gravimetric electrochemical capacities (2072 mAh mL–1 and 1337 mAh g–1, respectively) than current commercial graphite anodes in Li-ion batteries (300–430 mAh mL–1 and 372 mAh g–1). Calcium metal anodes have a 2+ oxidation state which would provide a greater energy density over monovalent systems (i.e., Li+ and Na+), and it has a standard reduction potential 0.17 V greater than that of Lithium. Compared to divalent systems, calcium batteries can have a higher cell voltage than magnesium because of the 0.5 V lower standard reduction potential of the latter. Ca2+ also has the potential for faster reaction kinetics as compared to magnesium (Mg2+) owing to its lower polarizing properties and charge density both in the electrode as well as in an intercalation cathode.
A veritiable calcium (ion) battery has not yet been commericially realized, but remains in the realm of research and development. Effort concentration of developing effective anode and cathode materials, as well as electrochemically stable electrolytes.
=== Anodes ===
Examples of anode materials include: vanadium oxide, Copper-calcium alloying, MgV2O5, graphite, metal calcium, and silicon anodes. Recent work on plating/stripping calcium was done in ethylene carbonate/propylene carbonate (EC/PC) solutions at elevated temperatures. It was also shown at room temperature in different electrolytes such as tetrahydrofuran and EC/PC. Aqueous batteries have used calcium vanadate.
=== Cathodes ===
Cathodes examined recently include calcium cobalt oxide and titanium disuphide, as well as hexacyanoferrates, or dual carrier batteries, as well as for aqueous calcium ion batteries. Theoretical work has been performed to ascertain the potential of cathodes from different crystal structures such as perovskite, spinel, other naturally occurring calcium compounds, as well as other calcium lanthanide oxide phases.
=== Other Battery Architectures ===
A primary Ca-S battery was examined. Ca-S batteries have also been examined using Li as a mediator to make it reversible.In addition, a calcium-air (Ca-O2) battery has been examined.
=== Electrolytes ===
Several different electrolyte systems have been examined for calcium (ion) batteries. Electrolytes are still an area of investigation, where previous work has shown that many low show low electrochemical stability. Redox reactions on calcium metal in several organic electrolytes was initially examined by Aurbach et al. Water as the electrolyte has been examined in a calcium ion battery. Alkyl carbonate electrolyte have also been examined. Theoretical studies have also been conducted on aprotic solvents showing they have favorable solvation/de-solvation properties. This has also been followed by experimental observations of salt solvation by different solvents. New salts based on Calcium hexafluoroisopropoxide (Ca(Ohfip)2·xTHF) and tris-hexafluoroisopropoxy borate (B(Ohfip)3) have also been examined. Polymer electrolytes have also been examined. One of the first samples of a polymer electrolyte was PVA/PVP complexed with CaCl2. Subsequent studies demonstrated polymer electrolytes made from PEDGA and PTHF both with Ca(NO3)2. Ionic liquids have also been examined.
Category:Calcium compounds
Category:Battery (electricity)
Category:Battery types