Stable fast-charging sodium-ion batteries achieved by a carbomethoxy-modified disodium organic material

Sodium-ion batteries (SIBs) are expected to be a low-cost alternative to lithium-ion batteries (LIBs) as the energy storage market keeps expanding. The organic material-based SIBs have the advantages of high capacity and optimizable molecular structure. However, poor conductivity and unstable cyclability hinder the application of organic materials in SIBs. Here, we introduce a carbomethoxy-modified insoluble quinone-based disodium salt (Na2dmcdbq) that enhances ionic diffusion by building ionic transportation channels. Na2dmcdbq shows impressive rate performance and cycle stability when coupled with carbon nanotubes. The composite electrode delivers 180 mAh/g capacity at 4,000 mA/g (22.5C) and retains 151 mAh/g capacity after 6,000 cycles. With a highly concentrated electrolyte, it achieves superior fast charge-discharge long-term cycle stability with a capacity retention of 76.8% after 35,000 at 40C. When pairing with a synthesized P2-type Na0.67Mn0.75Li0.25O2 cathode (550 Wh/kg), the full cell reaches 125 mAh/g capacity (0.2C) and runs for 1,000 cycles at 2C.