【作者】 张谦；

【导师】 胡文成；

【作者基本信息】 电子科技大学 ， 材料科学与工程， 2019， 博士

【摘要】 超级电容器具有循环寿命长,成本低以及功率密度高的特点,在能源领域得到了广泛的应用。碳布作为超级电容器的基底材料,具有柔性好,机械性能好以及电化学性能稳定等优点,但是较低的比表面积和容量限制了其在超级电容器领域的广泛应用,因此,如何提高碳布的电化学性能是目前超级电容器领域的研究热点之一。在此背景之下,本文围绕碳布的比表面积和导电性等问题,通过在碳布的表面复合掺氮多孔碳的方法来提高碳布和超级电容器的电化学性能。（1）在水热条件下用叠氮化钠对活性炭和碳布进行改性,提高其导电性。采用NaN₃水热的方法对活性炭进行氮元素的掺杂,氮掺杂活性炭（NAC）的比表面积仍可以达到1903 m²/g,表面氮元素的掺杂提高了电极材料的导电性,同时增加了电极材料的容量;NAC电极的电荷转移电阻R_ct只有2.2Ω;在1 A/g的电流密度下,电极的比容量可以达到51 F/g;对碳布依次进行扩孔和掺氮处理,制备的氮掺杂多孔碳布（NPCC）电极材料比表面积可以达到52 m²/g;将NPCC电极材料组装成对称的电容器进行充放电测试,在1 mA/cm²电流密度下,容量可以达到130mF/cm²;通过计算,当电容器的功率密度为0.375 W/cm³时,能量密度可达2.03mWh/cm³;在2.5 mA/cm²的电流密度下,经过30000次循环充放电后,器件的容量仍可达初始容量的95.8%,具有良好的电化学稳定性。（2）聚吡咯为前驱物,通过高温碳化工艺制备的多孔碳比表面积可以达到2256 m²/g,由多孔碳组装的对称超级电容器,在LiClO₄/AN电解液中进行测试,当电压窗口为1.25 V时,在0.5 A/g的电流密度下,电容器的容量可以达到62 F/g;当电压窗口为2 V时,在相同的电流密度下测试,电容器的容量增加到112.5 F/g;在1-乙基-3-甲基咪唑四氟硼酸盐中测试,电压窗口可以提升到4 V。在0.5 A/g的电流密度下,电容器的容量可以达到39.25 F/g,并且能量密度有了很大的提升,可以增长到87.2 Wh/kg。（3）通过碳布表面附着掺氮的多孔碳颗粒来提高比表面积,制备的掺氮多孔碳布（NCC）电极比表面积可以达到147 m²/g。当电流密度为8 mA/cm²时,电极的比容量可以达到1.2 F/cm²;对电极进行50000次的充放电测试,材料的比容量基本上没有衰减;将NCC电极材料作为负极,NCC电极表面沉积二氧化锰得到的复合电极材料（MNCC）作为正极组成非对称的超级电容器。当电流密度为3mA/cm²时,容量可以达到350 mF/cm²;当功率密度为208 mW/cm³,能量密度可以达到2.43 mWh/cm³。采用电沉积法和氢氧化钾扩孔法,制备氮掺杂多孔碳薄膜包覆的多孔碳布复合电极材料（PCC@NMC）,多孔碳薄膜厚度为250 nm,材料的比表面积可以达到244 m²/g;当电流密度为8 mA/cm²时,电极的比容量可以达到2.2 F/cm²;将PCC@NMC电极材料作为负极,组成非对称的超级电容器。当电流密度为4 mA/cm²时,器件的容量可以达到600 mF/cm²;组装成柔性的超级电容器可以使32个红色led灯保持16min的高亮度状态。（4）采用电沉积法得到多孔碳薄膜包覆的碳布（NCF）,NCF的比表面积提高到84 m²/g。然后用NaN₃水热的方法进行二次掺氮,得到氮掺杂多孔碳布（NNCF）;把NNCF电极材料制备成半电池进行电化学测试,测试的电化学窗口为0.001-3 V;在1 mA/cm²的电流密度下进行恒流充放电测试,NNCF的首次放电容量可以达到5.1 mAh/cm²;将表面涂覆钴酸锂的NNCF复合电极材料作为正极,NNCF作为负极,制备柔性的锂离子电池,当电流密度为0.2 mA/cm²时,放电容量可以达到0.2mAh/cm²;并且具备良好的倍率性能和循环稳定性。当制备的柔性电池弯折成不同角度测试时,容量基本保持不变,说明其具有良好的机械性能和柔性。更多还原

【Abstract】 Supercapacitors with long cycle life,low price and high power density have been widely used in the energy storage field.The carbon cloth,which has excellent conductivity and mechanical flexibility,has strong potential as support/current collector for flexible supercapacitor.However,the low specific surface area and capacitance limit their application.Therefore,this research focuse on improving the specific surface area and conductivity of the carbon cloth.The electrochemical properties are greatly improved through coating the nitrogen-doped carbon.（1）Sodium azide-assisted hydrothermal method was employed to improve conductivity of active caobon and carbon cloth.Adsorption desorption experiment confirmed that the N-doped active caobon（NAC）possesses a high specific surface area of 1903 m²/g.The existence of nitrogen element on the surface of carbon cloth not only improved the conductivity but also enhanced the capacitance.The Faradaic interfacial charge-transfer resistance(R_ct)was as low as 2.2Ωand the capacitance of NAC electrode could be 51 F/g at a current density of 1 A/g.The surface area of the N-doped porous carbon cloth（NPCC）was 52 m²/g.The NPCC device delivered a high areal capacitance of 130 mF/cm² at a current density of 1 mA/cm²,and the highest volumetric energy density of 2.03 mWh/cm³ was achieved at a volumetric power density of 0.375W/cm³.Additionally,the device could retain 95.8%of its initial capacitance even after30000 cycles at the current density of 2.5 mA/cm²,showing excellent electrochemical properties.（2）The N-doped porous carbon was prepared directly from the carbonization of polypyrrole（PPY）,which has a high surface area of 2256 m²/g.A device was assembled by using the N-doped porous carbon as the positive and negative electrodes and LiClO₄/AN as electrolyte.The capacitance of the device could be 62 F/g from potential range of 0-1.25 V,at the current density of 0.5 A/g.When the potential window was increased to 0-2V,the device has a capacitance of 112.5 F/g,at the current density of 0.5A/g.As the device was further tested by using the 1-ethyl-3-methylimidazole tetrafluoroborate as electrolyte.The capacitance was found to be 39.25 F/g in a broad window of 0-4 V at the current density of 0.5 A/g,corresponding to a high energy density up to 87.2 Wh/kg.（3）The nitrogen-doped carbon was coated on the surface of carbon cloth（NCC）to improve the surface.The specific surface area of the NCC was 147 m²/g.The NCC had a high specific capacitance of 1.2 F/cm² at 8 mA/cm² and excellent cycling stability with no visible decrease after 50000 cycles.An asymmetrical supercapacitor（ASC）was assembled by using MnO₂@NCC（MNCC）and NCC as the positive and negative electrodes.The flexible（ASC）delivered a high capacitance of 350 mF/cm² at 3mA/cm².The ASC devices were charged and then connected to power 16 light-emitting diode indicators for 8 min.Furthermore,the device can be bent and twisted without performance degradation,suggesting the good flexibility and stability.The porous carbon film was coated on the surface of porous carbon cloth（PCC@NMC）to improve the specific surface area.The PCC@NMC showed a specific surface area of 244 m²/g.The PCC@NMC electrode had a high specific capacitance of 2.2 F/cm² at 8 mA/cm².An ASC was assembled by using PCC@NMC as negative electrodes.The flexible（ASC）delivered a high capacitance of 600 mF/cm² at 4 mA/cm².The ASCs were charged and then connected to power 32 light-emitting diode indicators for 16 min.（4）The porous carbon film was deposited on the surface of carbon cloth（NCF）to improve the specific surface area.The specific surface area of NCF was measured to be84 m²/g.The NCF was treated in sodium azide solution at a hydrothermal environment to obtain a dual N-doped NCF（NNCF）with enhanced conductivity.The first discharge capacity of the NNCF electrode at 1 mA/cm² was 5.1 mAh/cm².The full device exhibited a high discharge capacity of 0.2 mAh/cm² at 0.2 mA/cm².The device with different bending angles delivered similar GCD curves,and the capacity was nearly unchanged.These findings revealed the excellent stability of the flexible LIB device.更多还原