Enhanced cycle performance of quinone-based anodes for sodium ion batteries by attachment to ordered mesoporous carbon and use of ionic liquid electrolyte

Sodium ion batteries (SIBs) have emerged as a potential alternative to lithium ion batteries due to their chemical similarities. Key considerations for SIBs include energy storage capacity, lifetime, cost, and safety. Major challenges associated with high performance organic electrodes for rechargeable batteries are their poor electrical conductivity and dissolution of the active material in common electrolytes. The poor conductivity limits the rate performance, while dissolution leads to poor cycle performance and short lifetimes. Here we demonstrate a route to address these challenges in a sodium ion battery for 2,5-disodium-1,4-benzoquinone, Na₂DBQ (organic active material), through immobilization of the Na₂DBQ on high surface area ordered mesoporous carbon, OMC, and use of 1-methyl-3-propylpyrrolidinium bis(fluoromethylsulfonyl)imide ionic liquid (IL) electrolyte, NaFSI/[PYR13][FSI]. These changes increase the rate capability and capacity retention after cycling when compared Na₂DBQ anodes using standard carbonate electrolytes. At 22◦C, the inclusion of the OMC leads to similar capacities for the IL- and carbonate-electrolytes, but the improved thermal stability of the IL enables safe operation at 60◦C, which more than doubles the discharge capacities due to enhanced ion mobility and charge transfer kinetics. At 60◦C, the capacity retention was 83% for the IL-electrolyte after 300 cycles. For the materials examined here, the use of IL electrolyte does not adversely impact the performance of organic anode sodium-ion batteries and provides advantages with a wider operating temperature range and improved safety when compared to typical carbonate-based electrolytes.