Study of the Reactivity of Na/Hard Carbon with Different Solvents and Electrolytes

Abstract

The reactivity of sodium inserted hard carbon with ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), EC:DEC, EC:DMC and NaPF 6 EC:DEC (/DMC) electrolytes was studied by Accelerating Rate Calorimetry (ARC), and the products after the ARC experiments were investigated by X-ray diffraction. The results show that sodium inserted hard carbon reacts with DMC to form sodium methyl carbonate, and that it reacts with EC and DEC to form sodium alkyl carbonates which apparently have a similar structure to sodium methyl carbonate. Sodium inserted hard carbon is more reactive with DMC and DEC than with EC. Finally, Na inserted hard carbon is more reactive in NaPF 6 EC:DEC and NaPF 6 EC:DMC than in EC:DEC and EC:DMC due to the high thermal stability of NaPF 6 and preferential solvation of NaPF 6 by EC, which leaves DEC and DMC available for reaction. The reactivity of Li inserted hard carbon was also compared to the reactivity of Na inserted hard carbon in both solvent and electrolyte and it was found that Li inserted hard carbon shows much better thermal stability.

Towards greener and more sustainable batteries for electrical energy storage

“…Moreover, Na 2 O 2 is less stable than Li 2 O 2 , and this could be an advantage for Na-O 2 cells, with the feasibility to easily reach Na 2 O (a four-electron process) 97 . Safety wise there is no indication or scientific grounds to tell whether Na-ion batteries will be safer or not than Li-ion batteries, but preliminary accelerating rate calorimetry tests suggest that they will be at least as safe as Li-ion batteries 98,99 . The advancement of Na-ion technology is a certainty, but the type of market it will conquer remains unclear.…”

Structural and Electrochemical Properties of Hard Carbon Negative Electrodes for Sodium Secondary Batteries Using the Na[FSA]–[C₃C₁pyrr][FSA] Ionic Liquid Electrolyte

“…5,6 For example, several positive electrode materials like We have also investigated the charge-discharge behavior of hard carbon (HC) negative electrodes in this ionic liquid at 363 K. 10,11 HC is mainly composed of two structural domains, i.e., randomly-arranged graphene domains and their interstitial sites (pores), and its charge-discharge behavior as a negative electrode material for sodium secondary batteries has been well investigated in organic solvent electrolytes. [12][13][14][15][16][17][18][19][20] However, there have been few studies on the correlation of HC structure and its electrochemical behavior in ionic liquid electrolytes.…”

Comprehensive Insights into the Reactivity of Electrolytes Based on Sodium Ions

“…It was also reported that the SEI on HC in NIBs containsm any inorganic speciest hat are nonhomogeneous and porousi nn ature. Xia et al [10][11][12] studied the thermal response of Na x -HC in the presenceo fv arious salts, such as NaPF 6 and sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), and solvent mixtures by using accelerated-rate calorimetry (ARC). In this study,aNaPF 6 -based electrolyte was more reactive than NaTFSIt owards sodiated HC because of the high thermals tabilityo fN aPF 6 ,w hich resultsi nthe absence of NaF in the SEI layer.M oreover,i nt he presence of NaPF 6 ,D MC and DEC are more reactive than EC if in contact with Na x -HC because of the preferentials olvationo fN a + + by EC, which leaves DMC and DECint he outer sphere.…”