Advanced anode materials for sodium ion batteries

Abstract

The economic growth over the last decades has gone hand in hand with the increase of the global energy demand. The use of fossil fuels, which are nowadays the world¿s leading energy source, entails serious environmental issues. For that reason, in order to meet the future energy requirements, the energy systems have to gradually move from fossil fuels towards renewable energy. In this regard, electrochemical energy storage and more specifically, batteries possess desirable features for the integration of renewable energy sources. Since their commercialization, Li ion batteries have been the dominant technology in the market. However, Na ion batteries are becoming an attractive alternative to the Li ion technology for stationary applications due to their lower cost owing to sodium abundance and wider geographical distribution. Although Na presents similar chemical properties to those of Li, the Li ion technology is non-fully transferable and new materials have to be developed.On the one hand, in this work, biomass derived hard carbon materials have been developed. Given the low cost of their lignin precursor, ease of synthesis, non-toxicity and relatively high capacity, hard carbons are considered promising anode materials for sodium ion batteries. The synthesis optimization of lignin derived hard carbons oriented towards the enhancement of the electrochemical properties through the improvement of the purity of the materials is presented. Several characterization techniques such as XRD, SEM-EDX, BET, Raman and SAXS have been used with the purpose of correlating the physico-chemical properties of the carbon materials and their electrochemical performance.On the other hand, polySchiff bases which are low cost, non-toxic, easy to synthesize, structurally diverse and safe organic electrodes have been alsoIIprepared. The synthesis optimization oriented towards the attainment ofPolySchiff-polyethylene oxide copolymers (PSB-PEO) with improvedprocessability with respect to bare PolySchiff polymers is detailed. Theevaluation of the material as anode in powder electrodes, as binder-freelaminate electrodes and as binder of other active materials is shown. Finally,the electrochemical performance as anodes of a carbon material and theoptimized PSB-PEO in a full-cell is evaluated.