Karlsruhe Institute of Technology (KIT ) researchers now present a promising electrolyte class for calcium batteries that has the potential for replacing lithium-ion technology.

Calcium-based batteries promise to reach a high energy density at low manufacturing costs. Using the electrolytes available today, however, has made it impossible so far to charge calcium batteries at room temperature.

Zhirong Zhao-Karger (left) and Zhenyou Li (right) from the POLiS (Post Lithium Storage) Cluster of Excellence succeeded in producing promising electrolytes for calcium batteries. Image Credit: Markus Breig, KIT. Click image for the largest view.

In the Energy & Environmental Science journal, researchers of Karlsruhe Institute of Technology presented a promising electrolyte class, with which room temperature charging will be possible.

Professor Maximilian Fichtner of KIT, Director of the research platform CELEST (Center for Electrochemical Energy Storage Ulm & Karlsruhe) said, “Efficient, large, and low-cost energy storage systems will facilitate nationwide transition to zero-emission mobility and power supply. Today’s predominant lithium-ion technology, however, cannot fulfill this task on a global scale.” CELEST is where calcium batteries and other storage technologies are studied.

“In the medium term, lithium-ion batteries will reach their limits in terms of performance and some of the resources used for their manufacture. This will prevent their future use wherever that would be reasonable for the energy transition. Availability of resources needed for manufacture, such as cobalt, nickel, and lithium, is limited,” he said.

At the Helmholtz Institute Ulm (HIU) established by KIT in cooperation with Ulm University, Fichtner and his team focus on alternative battery technologies instead. These technologies are based on more abundant resources. Calcium is a promising candidate, because it can release and accept two electrons per atom contrary to lithium and because it supplies a voltage similar to that of lithium: “Calcium is the fifth most abundant element in the Earth’s crust. It is distributed homogeneously on Earth and it is safe, non-toxic, and inexpensive,” noted Fichtner.

So far there has been a big obstacle in calcium battery development: In contrast to the established lithium-ion technology or more recent sodium or magnesium technologies, practicable electrolytes to produce rechargeable calcium batteries have been lacking.

Dr. Zhenyou Li, first author of the study, and Dr. Zhirong Zhao-Karger, who heads the project who are both are working in the POLiS (Post Lithium Storage) Cluster of Excellence of KIT that is embedded in CELEST said, “For a few years now, experimental electrolytes and, hence, prototypes of the calcium battery have been available. But these electrolytes enable charging at temperatures beyond 75 degrees Celsius only and additionally they are susceptible to undesired side reactions.”

The researchers have now succeeded in synthesizing a class of new electrolytes based on special organic calcium salts. These electrolytes enable charging at room temperature. Using the new electrolyte calcium tetrakis[hexafluoroisopropyloxy]borate, the researchers demonstrated feasibility of calcium batteries of high energy density, storage capacity, and quick-charging capability.

Their results have been published in the journal Energy & Environmental Science.

The new class of electrolytes is an important basis for transferring calcium batteries from the laboratory to application. In electric vehicles, mobile electronic devices, and stationary storage systems, they might replace the presently predominating lithium-ion battery one day. But this may take a while: “The new electrolytes are a first important step,” Fichtner emphasized. “There still is a far way to go to the mature calcium battery.”

The future alternatives to lithium ion chemistry continue to add up and improve. One day there will likely be choices both in cost and performance. And lithium ion may not be one of the leaders. For now there is some waiting, good expectations and more better cheaper batteries to look forward to.


2 Comments so far

  1. Gregory Harrison on October 29, 2019 6:40 AM

    New material has been discovered that is capable of increasing the speed of charging and discharging slower than before. So, new experiments are being observed by scientists.

  2. Willard Denesik on November 5, 2019 10:31 AM

    Calcium has potential in a number of areas, but struggles in finding a way to move electricity through an electrolyte.

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