Helmholtz Institute Ulm and Cheongju University researchers have created a new lithium-metal battery that promises to have an exceptionally high energy density of 560 watt-hours per kilogram as well as very excellent stability.
These batteries have greater energy storage capacity than conventional Li-ion batteries, but their stability is compromised by the fact that the electrode materials react with common electrolytes.
Nickel has a bright future as a cathode material because of its excellent specific capacity. The high nickel concentration, on the other hand, presents additional difficulties, such as poor cycling and thermal instability. Because Ni2+ and Li+ having a comparable ionic radius, nickel ions from the transition metal layer may readily migrate into nearby lithium vacancies, which is harmful to lithium-ion diffusion.
However, despite the disadvantages of Ni-rich cathodes, significant efforts have been made to develop materials that provide the optimum balance between high specific capacity and high safety features needed by the market. Magnesium, calcium, aluminum, and titanium are used to improve the structural stability of the cathodes by doping them into the transition metal layer, which prevents Ni2+ migration into the lithium layer. This process also helps improve the metal-oxygen binding to limit oxygen release and increases thermal stability.
Applying a protective surface coating on cathode materials is another way to minimize performance degradation. If Ni4+ does not come into direct contact with the electrolyte, then the detrimental effect of attack by highly reactive hydrogen fluoride or other components is reduced, and the parasitic reactions caused by the presence of Ni4+ are lessened or eliminated altogether.
For the second approach, the researchers used a low-cobalt, nickel-rich layered cathode (NCM88) for the cathode and a non-volatile, non-flammable ionic liquid electrolyte with two anions (ILE), bis(fluorosulfonyl) imide (FSI), and bis(trifluoromethanesulfonyl)imide (TFSI) for the electrolyte.
A widely used organic electrolyte (LP30), which causes particle fractures on the cathode, was replaced with ILE. This is where LP30 reacts, destroying the structure. On the cathode, a thick layer of lithium-containing moss develops.
Ion-exchange cathode shows excellent electrochemical performance with an initial specific capacity of 221mAh g-1 and capacity retention of 88% over 1,000 cycles when the electrolyte is ILE. More significantly, this electrolyte has a 99.94% average Coulombic efficiency.
A novel charge storage mechanism for calcium-air batteries has been discovered via joint research between the University of Liverpool in the United Kingdom and National Tsing Hua University (NTHU) in Taiwan, according to Mercom.
Researchers from the Massachusetts Institute of Technology and other institutions discovered a new electrolyte earlier this year that may enable lithium-ion batteries to store approximately 420 watt-hours per kilogram. 260 watt-hours per kilogram of energy may currently be stored in such batteries, according to industry standards.
