NaCrO_2 is a fundamentally safe positive electrode material for sodium-ion batteries with liquid electrolytes

摘要

Layered structure NaCrO_2 (R-3m) was successfully synthesized by solid state reaction. The electrochemical performance of NaCrO_2 as a positive electrode material for sodium-ion batteries was tested at room temperature using two-electrode coin cells with NaClO_4PC electrolyte. NaCrO_2 delivered a reversible capacity of 110 mAhg during the first charge and had good cyclability. The reaction between deintercalated Na xCrO_2 (～Na_(0.5)CrO_2) and ethylene carbonatediethyl carbonate solvent was studied using Accelerating Rate Calorimetry (ARC). The results were compared to analogous results for Li _(0.5)CoO_2 and Li0FePO_4 under the same conditions. Na_(0.5)CrO_2 showed an unexpected excellent thermal stability in solvent with no heat release in the ARC test temperature range. An X-ray diffraction study showed that Na_(0.5)CrO_2 decomposes to NaCrO_2 and P3-type layered structure CrO _(2-δ) with minimal oxygen release during the ARC tests, which explains the lack of exothermic behavior.