Effect of iron source precursor on sodium-ion battery material Na2FeP2O7/C
Carbon-coated Na2FeP2O7 cathode materials with sucrose as precursors are prepared by sol-gel process,the electrochemical performance of which is improved by optimizing the iron source.The conductivity of the material is improved by adjusting the proportion of sucrose to control the amount of coated carbon.The sucrose content of the precursor shouldn't be too high when the iron source is FeSO4·7H2O,while a higher sucrose precursor content is required when the iron source is Fe(NO3)3·9H2O.The electrode materials prepared by FeSO4·7H2O,Fe(NO3)3·9H2O iron sources show good cycle stability,the specific discharge capacity of 73 mAh/g and 74 mAh/g can be retained after 300 cycles at 1.0 C in 1.5-4.2 V,respectively,with the capacity retention rate of 91.6%and 95.1%,respectively.The carbon-coated material exhibits a specific discharge capacity of more than 48 mAh/g at 20.0 C,demonstrating good rate capability.Through the test of structure and electrochemical performance,it is found that the carbon-coated structure made of sucrose as carbon precursor at high temperature improves the electronic conductivity as well as increases the diffusion coefficient of Na+,thus improving the electrochemical performance.
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