Fe-based high voltage positive electrode material Li₂Fe(SO₄)₂ has shown consistent cycling only in experimental Swagelok cell configurations.[1, 2] In order for it to be practically viable, knowledge of its interaction with commercially used additives in the coating process is lacking. Thus, this work seeks to study the cycling performance of Li₂Fe(SO₄)₂in a half cell configuration with different types of binders and carbon based additives as a step towards commercial utilisation of the material.

Flourinated binder polvinylidene fluoride (PVDF) and non-fluorinated binder polyacrylonitrile (PAN) were both evaluated and shown to perform similarly. The long term cycling at low C-rates was found to be consistent for the systems with and without binder. However, at high C-rates a significant fall in capacity of nearly 60% was observed for the system with binders in comparison to the system without binder.

Li₂Fe(SO₄)₂ being polyanionic has poor electronic conductivity and requires carbon coating to enhance performance. This study investigates the effects of amorphous Super-P Carbon, Multi Walled Carbon Nanotubes and Single Walled Carbon Nanotubes when ball-milled with the electrode material. The carbon-coated material was then subjected to galvanostatic charge discharge tests over multiple cycles and at different charging rates. This study on the effect of binders and carbon additives lays the foundation for future work on an all-iron lithium battery and is a step forward in commercialising sulphate based cathode materials.

[1] M. Reynaud, M. Ati, B. C. Melot, M. T. Sougrati, G. Rousse, J.-N. Chotard, et al., "Li₂Fe(SO₄)₂ as a 3.83 V positive electrode material," Electrochemistry Communications, vol. 21, pp. 77-80, 2012.

[2] L. Lander, M. Reynaud, G. Rousse, M. T. Sougrati, C. Laberty-Robert, R. J. Messinger, et al., "Synthesis and electrochemical performance of the orthorhombic Li2Fe (SO4) 2 polymorph for Li-ion batteries," Chemistry of Materials, vol. 26, pp. 4178-4189, 2014.