Tunnel/Layer Composite Na0.44MnO2 Cathode Material with Enhanced Structural Stability via Cobalt Doping for Sodium-Ion Batteries

Abstract

Sodium-ion batteries (SIBs) are the most promising alternativeto lithium-ion batteries (LIBs) due to their low cost and environmentalfriendliness; therefore, enhancing the performance of SIBs'components is crucial. Although most of the studies have focused onsingle-phase cathode electrodes, these materials have difficulty inmeeting the requirements in practice. At this point, composite materialsshow superior performance due to balancing different structures andare offered as an alternative to single-phase cathodes. In this study,we synthesized a Na0.44MnO2/Na0.7MnO2.05 composite material in a single step with cobaltsubstitution. Changes in the crystal structure and the physical andelectrochemical properties of the composite and bare structures werestudied. We report that even if the initial capacity is slightly lower,the rate and cyclic performance of the 1% Co-substituted compositesample (CO10) are superior to the undoped Na0.44MnO2 (NMO) and 5% Co-substituted (CO50) samples after 100 cycles.The results show that with the composite cathode phase transformationsare suppressed, structural degradation is prevented, and better batteryperformance is achieved.