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The objective of this study is to optimize the performance of a graphitized carbon xerogel doped with graphene oxide (GXGO) as cathode for sodium dual-ion batteries. Carbon xerogels are synthetic materials produced in large amounts, with wellcontrolled chemistry, porosity and structure, by a simple and fast microwave process that has been scaled-up. The intercalation of PF 6 À anions from various NaPF 6 salt-based electrolytes in a GXGO-based cathode is investigated by considering the influence of the upper cut-off voltage (UCOV) and of the electrolyte on the electrochemical parameters. The best results were attained in an electrolyte with a 2.0 M NaPF 6 concentration in EC : EMC carbonate solvent mixture with added FEC, at a UCOV of 5.0 V. GXGO cathode provides a discharge capacity of 47 mAh g À 1 after 2500 cycles with a coulombic efficiency of 97 %. Moreover, it shows great cycling stability and capacity retention of essentially 100 % after the initial cycles.

In recent years, the research on lithium-ion batteries (LIBs) to improve their lifetime, efficiency and energy density has led to the use of silicon-based materials as a promising anode alternative to graphite. Specifically, crystalline silicon (cSi) and silicon carbide (SiC) obtained from deposition or reduction processes (e.g., magnesiothermal reduction) stand out for their electrochemical properties. However, the synthesis routes proposed until now have limitations that make them difficult to afford or operate on a large scale. For this reason, in this work, carbon-silicon (C-Si) hybrid materials synthesized through an efficient route are evaluated as the potential precursor for the obtention of both cSi and SiC species in a single material. The feasibility and influence of the magnesiothermal reduction process were evaluated, and materials with 10 wt.% of reduced Si and 10–26 wt.% of SiC were obtained. Both species play a role in the improvement of the performance of silicon-based materials as anodes in lithium-ion batteries. In comparison with materials obtained by the reduction of silica gels and composites, the reduced C-Si hybrid gels stand out thanks to the homogeneous distribution and stability of the species developed.

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