Sustainability in batteries needs to be considered at a holistic level, from materials source, manufacturing, lifetime and if there is value in the materials what happens to the batteries at end of life. In this work we discuss three different aspects of sustainable considerations within a sodium-ion technology development. Materials developments, cell lifetime and optimisations, and design for recycling.

The cell is comprised of a nickel based layered oxide material cathode with hard carbon anode. To maximise energy density and life-time degradation of the bulk and surface of the O3-type oxides require stabilisation.¹ We discuss a facile method for manufacturing a stabilised O3- type layered oxide via simultaneous doping and surface coating. A higher average voltage is obtained, which stabilised the high voltage phase transition to higher voltages, and results in longer-cycle life.²

To improve the materials life-cycle lifetime of the battery is also considered, and methods to improve the 1^st lifetime and use discussed. The formation of the interface layers is key, and in addition to the stabilisation of the cathode surface stabilisation of the negative electrode is required. This is initially achieved with formation processes, and can be modified with different electrolyte additives.^3,4 It is hypothesised that water causes significant damage, and removing these small molecules, for example using ZSM-5, in both an electrode and an electrolyte results in significant improvement in lifetime of the cell and the electrodes with less SEI build up over time.

Finally design for remanufacture is also discussed, utilising water-based binder systems we show differences in delamination and material recovery. Utilising different recycling schemes through shredding and physical processing through to disassembly processes improvements in recovery rates are required. Particularly for low value materials, where the techno-economics of the processes do not currently work. Direct recycling of materials reclaimed from the batteries, wherever possible allows value within the material design to be maintained, rather than relying directly upon elemental value. Aspects of direct loop recycling and short loop recycling are discussed with respect to current lithium-ion technologies, and the ability to directly translate this to sodium-ion.

In conclusion three aspects for sustainability considerations are discussed with respect to the materials life-cycle; active material optimisation, longevity and life-time when in use and electrode developments for recycling.

1.           Song, T. & Kendrick, E. Recent Progress on Strategies to Improve the High-Voltage Stability of Layered-Oxide Cathode Materials for Sodium-ion Batteries. J. Phys. Mater. 4, 32004 (2021).

2.           Song, T. et al. High-Voltage Stabilization of O3-Type Layered Oxide for Sodium-Ion Batteries by Simultaneous Tin Dual Modification. Chem. Mater. 34, 4153–4165 (2022).

3.           Chen, L., Kishore, B., Walker, M., Dancer, C. E. J. & Kendrick, E. Nanozeolite ZSM-5 electrolyte additive for long life sodium-ion batteries. Chem. Commun. 56, 11609–11612 (2020).

4.           Kishore, B., Chen, L., Dancer, C. E. J. & Kendrick, E. Electrochemical formation protocols for maximising the life-time of a sodium ion battery. Chem. Commun. 56, 12925–12928 (2020).