The development of the layered cathode material for sodium ion batteries are hindered by synthesis approaches. The sol-gel method is a promising way to prepare the cathodes due to the advantage of mixing the raw product at atomic or molecular level, while the selection criteria for complexing agents are still unclear. Herein, the Na0.9Ni0.45Mn0.55O2 cathode is successfully prepared via sol-gel method, by using sucrose, glucose, citric acid, and ethylene diamine tetra-acetic acid as the chelating agent, respectively. The effects of different chelating agents on the morphologies, structural and electrochemical properties are studied in detail. Electrochemical properties prove that the sample using citric acid shows the best electrochemical performance, delivering a capacity of 96 mAh g−1 and 48% retention after 300 cycles at 1C, and 59.6 mAh g−1 of capacity at 10 C rate, which are significantly higher than those of the other samples. XRD and HRTEM are conducted for the cycled electrodes, which demonstrate that the structure of the optimized sample maintains better phase stability and interfacial stability. This work is of considerable significance in understanding the selection criteria for the synthesis of layered cathode chelators for sodium-ion batteries by the sol-gel method. •Layered Na0.9Ni0.45Mn0.55O2 is prepared via sol-gel method.•The effect of the chelating agents on the Na0.9Ni0.45Mn0.55O2 are discussed.•Citric acid assisted Na0.9Ni0.45Mn0.55O2 shows superior electrochemical properties.•Citric acid assisted Na0.9Ni0.45Mn0.55O2 exhibits well dynamic behavior.•Citric acid can fix more sodium and thus obtaining a stable structure.