Functionalized Carboxyl Carbon/NaBOB Composite as Highly Conductive Electrolyte for Sodium Ion Batteries

Sodium-ion batteries are the most promising candidates of reusable batteries because of the huge abundant sodium resources and low cost. So the new types of sodium electrolyte materials are attracted to be identified. In this paper, a series of sodium composites are synthesized by the carboxyl carbon spheres (HTC-COOH) and sodium bis(oxalate)-borate (NaBOB) using the solid-state reaction. FTIR, TG, XRD, elemental analysis, SEM and AFM are used to prove the successful synthesis of functionalized carboxyl carbon/NaBOB (HTC/NaBOB) composite. The thermal stability and ionic conductivity of the composites are also studied and discussed. The test results show the HTC/NaBOB composites have high thermal stability, which possess the thermal decomposition temperature higher than 300 degrees C in N-2. When the weight ratio of oxalic acid, boric acid, sodium hydroxide and HTC-COOH reaches appropriate proportion, the conductivity of HTC/NaBOB composite electrolyte solution is higher than NaBOB in N, N-Dimethylformamide (DMF) with the same the content of element boron and the ionic conductivity of 0.10mol dm(-3) electrolyte solution is 4.87 mScm(-1) in DMF. The study shows that these composites are non-absorbent water and easy to be recycle and store as electrolytes. They may have great potential as a new class of electrolyte for high-performance sodium ion batteries.