Rational design of sodium battery electrodes

Batteries are increasingly essential and will play a crucial role in the energy transition both for the electrification of transport and for improved grid storage to mitigate intermittent renewable generation.

Lithium-based battery technologies currently dominate but suffer from high costs and unsustainable manufacturing practices, as well as geopolitical concerns and safety issues.

Sodium-based cells are an emerging drop-in replacement, offering high energy densities, at lower cost and improved environmental profile compared to lithium systems.

However, implementation is limited by the electrode performance, in terms of intrinsic capacity, stability and charge/discharge kinetics.

There is an enormous opportunity to apply rational design principles to the existing, broadly empirical electrode architectures. Battery electrodes must simultaneously satisfy a number of property constraints that are inherently in conflict.

They must provide both electronic and ionic transport, with low loss; often the conduction paths are in two complementary phases that must both form interpenetrating connected networks.

At the same time, the active materials must undergo redox reactions, but remain mechanically stable and coherent, whilst retaining chemical stability over numerous cycles. Increased surface area accelerates the rate of desirable electrochemical processes but also parasitic side reactions.

These conflicting demands can, in principle, be addressed by applying microstructural design to optimize the geometry, connectivity and scale of the active material(s).

New, regular architectures can balance the demands of the electron/ion transport networks and the mechanical stresses/strains that develop during repeated cycling.