Graphitic carbon foams as anodes for sodium-ion batteries in glyme-based electrolytes

The electrochemical performance as potential anodes for sodium-ion batteries of boron-doped and non-doped graphitic carbon foams is investigated by galvanostic cycling versus Na/Na at different electrical current densities, in glyme-based electrolytes which are known to allow the intercalation of the Na ions into graphite. The influence of materials composition and graphitic degree on battery parameters is firstly determined and further discussed by analyzing the mechanism of the electrochemical storage of Na ions into these materials which was found to occur through different combinations of pseudocapacitive intercalation and diffusion-controlled intercalation processes. In summary, the results of this study have demonstrated that graphitic carbon foams match a very acceptable capacity with excellent cycle stability as well as performance at high electrical current densities (up to ∼ 90 mAh g after 300 cycles at 1.9 A g with coulombic efficiency ∼ 100%) which make them suitable for sodium-ion battery applications. Overall, the increase of the interlayer spacing between the graphene layers and the presence of boron promote the pseudocapacitive intercalation which is responsible for the remarkable rate performance of these materials, whereas the improvement of diffusion-controlled intercalation capacity is mainly related to larger boron content.Financial support from the Spanish Ministry of Economy and Competitiveness MINECO (under Project ENE2014-52189-C2-2-R) and Iberdrola Spain Foundation (www.fundacioniberdrola.org, Projects 2016-2017) is gratefully acknowledged. J. Rodríguez-García thanks the MINECO for a Ph.D. grant (FPI BES 2015-071293) to develop the work. Thanks are also given to R. García of the INCAR (CSIC) for providing carbon foams