Sodium-ion batteries: Replacement for lithium-ion batteries

Dr Qingsong Wang from the University of Bayreuthis driving forward research into sodium-ion batteries as a cost-effective, sustainable alternative to lithium-ion. As part of an international team of researchers, he has developed a battery with a long service life and high energy. The results have now been published in Nature Energy.

What for?

Lithium-ion batteries are the most successful energy storage technology of recent decades. However, the raw materials for the production of lithium-ion batteries are limited and unevenly distributed in certain countries and regions. In order to relieve the pressure on lithium sources worldwide and utilise a geopolitically and strategically independent raw material, scientists have high hopes for sodium-ion batteries. Sodium is 1,000 times more abundant in the earth's crust than lithium. Sodium and lithium belong to the same group of alkali metals in the periodic table. This means that they have similar chemical and performance properties, and indeed the mature infrastructure of lithium-ion battery technology can be rapidly utilised for the production of sodium-ion batteries.

Cost-effective and sustainable replacement

The constantly growing demand for energy storage is driving research and development in battery technology. The sodium-ion battery is a reliable and affordable replacement for lithium-ion batteries. The easy accessibility and availability of sodium makes sodium-ion batteries more attractive and competitive. By using elements that are abundant in the earth and adjusting the phase growth of the layered oxide cathode, a long-cycle, high-energy sodium-ion battery has now been developed and validated at 165 Wh/Kg with the collaboration of Dr Qingsong Wang, junior group leader at the Chair of Inorganic Active Materials for Electrochemical Energy Storage. "Our result shows that sodium-ion batteries are even more cost-effective and sustainable on an industrial scale than conventional lithium-ion batteries, which are based on iron phosphate chemistry," says Wang.

In the study, which has now been published in Nature Energy by a team of scientists from the Universities of Bayreuth (Germany), Xiamen (China), Shenzhen (China), the Argon National Laboratory (USA) and the Physics Institute of the Chinese Academy of Sciences in Beijing (China), it is shown that the intergrowth structure can be adapted by controlling the charge depth. This allows a prismatic-type stacking state to be inserted evenly between the octahedral-type stacking states. This helps to avoid neighbouring octahedral-type stacking faults.

Octahedral-type and prismatic-type refer to the geometric arrangement of atoms or ions in a crystal lattice. Octahedral-type means that the atoms or ions in a crystal are arranged in an arrangement that resembles an octahedron. Prismatic-type refers to an arrangement that resembles a prism.

"Our research is to analyse the anionic oxygen redox reaction as an energy enhancer of the layered oxide for the sodium ion cathode," says Wang. "It is important to develop a strategy to make this reaction reversible and stable. In the long term, the results of our research can make mid-range electric vehicles more affordable, as the batteries for them can then be produced more cheaply and with a longer service life."