摘要
Abstract
In this work,NaNi0.4Mn0.4Fe0.2O2(NMF)was used as the sodium-ion source for insertion into a hard carbon(HC)anode material.Various amounts of sodium ions were pre-doped into the HC electrode to achieve different pre-sodiation ratios.AC//HC sodium-ion capacitors were fabricated using an activated carbon(AC)cathode and a pre-sodiated HC anode.The influence of different pre-sodiation ratios on electrochemical performance was analyzed through electrochemical tests.Results indicated that sodium-ion capacitors with a pre-sodiation ratio above 50%exhibited significantly improved performance,including higher voltage,lower direct current internal resistance,enhanced capacity,superior rate performance,and increased power and cycle stability.With a pre-sodiation ratio of 80%,the capacitor demonstrated a linear charge-discharge profile over the voltage range.Additionally,the discharge capacity increased to 83.73 mAh,which was three times that of a capacitor with 0 pre-sodiation.In terms of rate performance,the discharge energy retention at 3 A(44C)improved significantly to 79.35%compared to that at 0.1 A(1.5C),whereas the capacitor with 0 pre-sodiation retained only 26.35%under the same conditions.Furthermore,as the pre-sodiation ratio increased from 0 to 80%,the power density rose from 9807.89 W/kg to 24498.51 W/kg.Capacitors with a 50%pre-sodiation ratio retained more than 90%of their initial energy after 3000 cycles,and their gas expansion degree was lower than that of capacitors with a pre-sodiation ratio below 30%.The lower open-circuit voltage(OCV)of the HC anode due to pre-sodiation increased the operating voltage range of the AC cathode,effectively enhancing the capacity and energy density of the AC//HC sodium-ion capacitor.Additionally,the lower OCV facilitated the formation of a dense solid electrolyte interphase(SEI)layer,improving its stability and cycle performance.However,controlling the pre-sodiation ratio within an optimal range is crucial to achieving the best electrochemical performance.This research provides a scientific basis for the industrial implementation of sodium-ion capacitor pre-sodiation.关键词
钠离子电容器/预钠化/镍铁锰酸钠/活性炭/硬碳Key words
sodium-ion capacitors/pre-sodiation/sodium nickel iron manganese oxide/activated carbon/hard carbon分类
信息技术与安全科学
