germany

Researchers in Germany have developed a lithium-ion metal cell that reaches 560Wh/kg. 

The energy density— based on the total weight of the active materials— comes from a nickel-rich cathode that enables storage of high energy per mass.

The scientists are from Helmholtz Institute Ulm (HIU) of Karlsruhe Institute of Technology (KIT) in Germany reports the cell has shown the battery’s capacity remains 88% after 1,000 cycles due to its ionic liquid electrolyte.

Researchers first used a cobalt-poor, nickel-rich layered cathode (NCM88) with the commonly used, commercially available organic electrolyte (LP30), but the cell’s storage capacity decreased as the number of cycles increased with this  combination.

By using a dual-anion ionic liquid electrolyte (ILE) the NCM88 cathode reached 560Wh/kg.

The combination of cathode and electrolyte was reported in the journal Joule.

Its initial storage capacity is 214mAh g-1 of the cathode material. The average Coulombic efficiency, i.e., the ratio between discharge and charge capacity, is 99.94%. 

Professor Stefano Passerini, director of HIU and head of the electrochemistry for Batteries Group, said: “In the electrolyte LP30, particles crack on the cathode. Inside these cracks, the electrolyte reacts and damages the structure.

“In addition, a thick mossy lithium-containing layer forms on the anode.” 

For this reason, the scientists used a non-volatile, poorly-flammable, dual-anion ionic liquid electrolyte (ILE) instead to reduce structural modifications on the nickel-rich cathode 

Image: With a promising combination of cathode and electrolyte, the HIU researchers aim to make a very high energy density possible. (Photo: Amadeus Bramsiepe, KIT)

An international team of scientists has developed a method of boosting the lifetime of lithium metal batteries to “hundreds” of cycles by preventing dendritic growth.

The researchers used a separator made of an extremely thin, two-dimensional membrane made of carbon to reach more than 300 cycles of their battery.

At less than one nanometer, the separator pores are smaller than the critical nucleus size and, as such, prevent the nucleation that leads to the formation of dendrites.

Instead of forming dendritic structures, the lithium is deposited on the anode as a smooth film, which prevents the separator membrane being damaged and affecting the functionality of the battery.

The team included scientists from Friedrich Schiller University Jena in Germany, and Boston University (BU) and Wayne State University (WSU) in the US. 

The researchers report on their method in the journal Advanced Energy Materials.

Dr Antony George from the University of Jena, said: “To test our method, we recharged test batteries fitted with our Hybrid Separator Membrane over and over again.

“Even after hundreds of charging and discharging cycles, we couldn’t detect any dendritic growth.”

Associate professor Leela Mohana Reddy Arava from the WSU, said the key innovation was stabilising electrode/electrolyte interface with an ultra-thin membrane that did not alter current battery manufacturing process.

Sathish Rajendran, a graduate student at WSU, said: “The separator gets the least amount of attention when compared to the other components of the battery.

“The extent to which a nanometer thick two-dimensional membrane on the separator could make a difference in the lifetime of a battery is fascinating.”

As a result, the research team is confident their findings have the potential to bring about a new generation of lithium batteries. 

They have applied for a patent for their method.

The next step is to see how the application of the two-dimensional membrane can be integrated into the manufacturing process. 

The researchers also want to apply the idea to other types of batteries.

Image (Turchanin et al./Wiley): a) Regular battery separators with microscale porosity cause non-uniform lithium transport during the battery charge-discharge cycles resulting in needle-like growth of metallic lithium. This leads to short circuits and premature failure of lithium metal batteries. b) By introducing a carbon nanomembrane on the regular battery separator, the growth of lithium needles can be suppressed. The sub-nanometer-sized pores in carbon nanomembranes regulate the transport of lithium ions during the battery charge-discharge cycles, resulting in the deposition of a smooth film and the battery life can be increased significantly. 

Climatic chamber maker Weiss Technik has developed a test bench for lithium-ion batteries that aims to improve the safety, durability and performance of batteries as well as inform the development of EU-standards.

Developed at its German headquarters, the testing facility at the EU’s Joint Research Centre (JRC) in Petten, the Netherlands, will enable researchers to use computer tomography (CT) images during battery operation. 

The German Bundestag is expected to pass a ‘batteries collection’ bill in September intended to level the playing field and includes new requirements from the Waste Framework Directive.

The German cabinet has drafted changes to the German Batteries Act and the German Federal Council has, with changes, approved the amendment. 

German manufacturer Tesvolt is supplying 2MWh of its lithium-ion energy storage systems to Europe’s largest electric car charging park in the German state of Hilden.

The ESSs at Kreuz Hilden junction park will deliver power to 114 charging stations, including 40 V3 Tesla Superchargers and 22 fast charging stations from Dutch supplier Fastned with a combined charging power of up to 350kW.