
Sodium-ion batteries: How doping works
Sodium-ion batteries (SIBs) would therefore be a good alternative, especially if the weight of the batteries is not a major concern, for example in stationary energy storage system
Sodium-ion batteries still have a number of weaknesses that could be remedied by optimising the battery materials. One possibility is to dope the cathode material with foreign elements. To investigate the effects of doping with Scandium and Magnesium a team from Helmholtz-Zentrum Berlin (HZB) and Humboldt-Universität zu Berlin collected data at the X-ray synchrotron sources BESSY II, PETRA III, and SOLARIS. They uncovered two competing mechanisms that determine the stability of the cathodes.
Lithium-ion batteries (LIB) have the highest possible energy density per kilogramme but lithium resources are limited. Sodium, on the other hand, has a virtually unlimited supply and is the second-best option in terms of energy density. Sodium-ion batteries (SIBs) would therefore be a good alternative, especially if the weight of the batteries is not a major concern, for example in stationary energy storage systems.
However, experts are convinced that the capacity of these batteries could be significantly increased by a targeted material design of the cathodes. Cathode materials made of layered transition metal oxides with the elements nickel and manganese (NMO cathodes) are particularly promising. They form host structures in which the sodium ions are stored during discharge and released again during charging. However, there is a risk of chemical reactions which may initially improve the capacity, but ultimately degrade the cathode material through local structural changes. This has the consequence of reducing the lifetime of the sodium-ion batteries.
“But we need high capacity with high stability,” says scientist Katherine Mazzio, who is a member of the joint research group Operando Battery Analysis in Berlin, headed by Prof. Philipp Adelhelm. Spearheaded by PhD student Yongchun Li, they have now investigated how doping with foreign elements affects the NMO cathodes.
