Energy storage systems made from abundant and environmentally friendly materials are essential for the transition to a sustainable economy. Although lithium-ion batteries (LIBs) are the most popular battery technology today, the increasing demand and low availability of lithium and the use of cobalt and other rare metals raise questions about the sustainability and long-term viability of LIBs. power source as the only energy storage solution. The high abundance of sodium and relative similarity to LIBs allow sodium ion batteries (SIBs) to be considered as an alternative to stationary energy storage devices. However, many issues have hindered the widespread adoption of SIB technology, including the relatively low energy density compared to LIBs. Lower energy density electrodes such as Na2FeP2O7 are generally cycle stable, while many higher energy density electrodes such as Na0.67MnO2 have shorter lifetimes. In this presentation we show several possible solutions to tailor the composition, structure and morphology of cathode materials thus improving an electrochemical performance of SIBs made of these materials.
The promising cathode material Na2FeP2O7 was studied to improve its electrical conductivity, which is often low in the case of sodium pyrophosphates. Solution synthesis was used to prepare pristine Na2FeP2O7 and Na2FeP2O7/C composite cathode materials for SIBs, using glucose as a carbon source. It is demonstrated that the addition of carbon increases the capacity of electrode with an excellent rate capability. The optimal content of carbon in electrode material was found to be 4.8%. Electrochemical measurements were carried out in 1 M NaClO4 salt in propylene carbonate as electrolyte and show that the addition of 5 wt.% fluoroethylene carbonate solid electrolyte interphase stabilizing additive greatly benefits the rate and cycling performance of Na2FeP2O7/C .
Na0,67MnO2 is another compound that is widely studied as cathode materials in sodium ion batteries. Currently polyvinylidene fluoride (PVDF) is the most popular binder choice. In our study, a novel tetrabutylammonium (TBA) alginate binder is used to prepare a Na0,67MnO2 electrode for sodium-ion batteries with improved electrochemical performance. The ageing of the electrodes has been characterized. TBA alginate-based electrodes are compared to PVDF and Na alginate-based electrodes and show favorable electrochemical performance, with gravimetric capacity values higher than measured for the electrode prepared with PVDF binder. TBA alginate-based Na0,67MnO2 electrodes also display good rate capability and improved cyclability and their solid–electrolyte interface is similar to that of PVDF-based electrodes . Overall, we have shown that binder and electrolyte selection can significantly improve the electrochemical properties of electrode materials for SIBs.
The financial support of projects No. 22.214.171.124/VIAA/1/16/166 “Advanced materials for sodium Ion batteries” and No. lzp-2020/1-0391 “Advanced polymer – ionic liquid composites for sodium-ion polymer batteries” is greatly acknowledged. Institute of Solid-State Physics, University of Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Program H2020-WIDESPREAD-01–2016-2017-Teaming Phase 2 under grant agreement No. 739508, project CAMART2.
- Kucinskis, G.; Nesterova, I.; Sarakovskis, A.; Bikse, L.; Hodakovska, J.; Bajars, G. Electrochemical performance of Na2FeP2O7/C cathode for sodium-ion batteries in electrolyte with fluoroethylene carbonate additive. J. Alloys and Compounds 2022, 895, 162656.
- Kucinskis, G.; Kruze, B.; Korde, P.; Sarakovskis, A.; Viksna, A.; Hodakovska, J.; Bajars, G. Enhanced Electrochemical Properties of Na0.67MnO2 Cathode for Na-Ion Batteries Prepared with Novel Tetrabutylammonium Alginate Binder. Batteries 2022, 8, 6.