【作者】 王炯；

【导师】 周向阳； 杨娟；

【作者基本信息】 中南大学 ， 材料冶金， 2023， 博士

【摘要】 锂离子电容器是一种高性能的电池电容混合储能装置,具有功率密度和能量密度高且循环性能好的优点,被认为是极具发展潜力的新一代储能器件。虽然以商业活性炭为正极、石墨为负极的锂离子电容器已实现了商业化应用,但受限于商业活性炭容量低和石墨倍率性能差的问题,该器件的能量密度和功率密度难以满足市场需求。开发具有高电容性能的多孔炭正极材料和高倍率容量的嵌锂负极材料,是提升锂离子电容器的能量密度和功率密度的关键。本论文以来源广泛、成本低廉、可再生的生物质竹材为原料,在碱性水热条件下将其液化并以此为前驱体,利用硬模板法和杂原子掺杂改性技术,制备了一系列竹液衍生多孔炭及其复合材料用于构筑高性能锂离子电容器。主要的研究内容及研究结果如下:（1）利用碱性水热液化技术对竹材进行液化,系统地研究了碱液浓度、水热温度和水热时间对竹材液化程度的影响。KOH浓度3mol L^-1、水热温度200℃、水热时间6 h的制备条件下能使竹材实现高达98.6%的液化率和杂质的深度脱除。液化过程中竹材的木质素和半纤维素较易溶出,纤维素发生溶胀和转型,从纤维素Ⅰ型转变为更易水解的纤维素Ⅱ型。（2）在竹材水热液化前驱体中添加硬模板剂硝酸锌和活化剂氢氧化钾,热处理后酸/水洗得到竹液衍生多孔炭正极及其负载氧化锌负极材料。得益于竹液衍生多孔炭BLZAC2的高比表面积2303.9 m²g^-1,BLZAC2正极具有良好的电容性和优异的循环稳定性,在0.2 A g^-1下比容量高达94.3 m Ah g^-1,在5 A g^-1下经2000次循环后容量保持率为88.4%。竹液衍生多孔炭负载氧化锌CZ2负极具有较高的比容量和长的循环寿命,在0.2 A g^-1时的比容量为709.3 m Ah g^-1,在5 A g^-1下经1000次循环后容量保持率为80.9%。组装的CZ2//BLZAC2锂离子电容器最高能量密度和功率密度为135 Wh kg^-1和9.8 k W kg^-1,5A g^-1下循环8000次后容量保持率为83.9%。（3）在竹液衍生多孔炭制备过程中添加硫脲作为氮硫源,得到的氮硫共掺竹液衍生多孔炭BLZSC1。得益于氮硫杂原子的掺杂BLZSC1正极表现出极好的电容性能和极佳的循环稳定性,在0.2 A g^-1下比容量高达111.8 m Ah g^-1,在5 A g^-1下经2000次循环后容量保持率为85.8%。利用硫化制备出氮硫共掺竹液衍生多孔炭负载硫化锌负极CZS1,得益于杂原子掺杂和硫化锌本征电导率低于氧化锌,CZS1负极具有极好的倍率性能和极佳的循环稳定性,在0.2 A g^-1时的比容量为740.5 m Ah g^-1,在5 A g^-1下经1000次循环后容量保持率为86.9%。组装的CZS1//BLZSC1锂离子电容器最高能量密度和功率密度为158 Wh kg^-1和10 k W kg^-1。在5 A g^-1下经过8000次循环后容量保持率为79.2%。（4）在竹材水热液化前驱体中添加硬模板氢氧化镁,通过碱活化协同二维模板原理,制备出竹液衍生二维分级多孔炭FPC2。FPC2总孔体积为2.84 cm³g^-1,介孔率高达90%。得益于FPC2的高介孔体积和二维片状结构,FPC2正极展现出优越的倍率性能和优异的循环稳定性。在10 A g^-1时仍有48.5 m Ah g^-1的比容量,循环2000次后容量保持率为92.6%。再在FPC2上原位生长纳米硅制备出竹液衍生二维分级多孔炭负载纳米硅FPC-Si材料。凭借多孔片状炭基体的结构优势,FPC-Si负极在0.2 A g^-1下的比容量为1385.1 m Ah g^-1,在5 A g^-1下循环500次后容量保持率为70.1%。组装的FPC-Si//FPC2锂离子电容器最高能量密度和功率密度为179 Wh kg^-1和27.5 k W kg^-1,在5A g^-1下经8000次循环后容量保持率为82.3%。图76幅,表21个,参考文献202篇更多还原

【Abstract】 Lithium-ion capacitor is a high-performance battery-capacitor hybrid energy storage device with the advantages of high power density and energy density and excellent cycling performance,which is considered as a new generation energy storage device with great development potential.Lithium-ion capacitors with commercial activated carbon as the cathode and graphite as the anode have been commercially applied.However,due to the low capacity of commercial activated carbon and poor rate performance of graphite,the energy density and power density of the devices are increasingly unable to meet the market demand.The development of porous carbon cathode materials with high capacitance performance and inserted lithium anode materials with high rate capacity is the key to improve the energy density and power density of lithium-ion capacitors.In this work,the widely sourced,low cost and renewable biomass bamboo is used as the raw material,and after liquefaction,a series of bamboo liquid derived porous carbons and their composites were prepared by using the method of alkali activation coupled with templating and heteroatom doping modification technique for the construction of high performance lithium-ion capacitors.The main research contents and results are as follows:（1）The effects of alkali concentration,hydrothermal temperature and hydrothermal time on the degree of liquefaction of bamboo powder was systematically investigated by using alkali hydrothermal liquefaction technology.The preparation conditions of KOH concentration of 3 mol L^-1,hydrothermal temperature of 200℃and hydrothermal time of 6 h could achieve up to 98.6%liquefaction rate of bamboo material,while impurities were also deeply removed.During the liquefaction process,lignin and hemicellulose of bamboo were more easily dissolved,and cellulose underwent dissolution and transformation from cellulose I to the more easily hydrolyzed cellulose II.（2）Zinc nitrate as a hard template agent and potassium hydroxide as an activator were added to the hydrothermally liquefied precursor of bamboo.Acid/water washing after heat treatment to obtain bamboo liquid-derived porous carbon cathodes and their Zn O-loaded anode materials.Thanks to the high specific surface area of 2303.9 m² g^-1,BLZAC2 cathode has good capacitance and excellent cycling stability,with a specific capacity of 94.3 m Ah g^-1 at 0.2 A g^-1and 88.4%capacity retention after2000 cycles at 5 A g^-1.The bamboo liquid-based porous carbon loaded Zn O anode CZ2 has a high specific capacity and long cycle life,The specific capacity was 709.3 m Ah g^-1 at 0.2 A g^-1.The capacity retention rate reached80.9%after 1000 cycles at 5 A g^-1.The highest energy and power densities of the assembled CZ2//BLZAC2 lithium-ion capacitors were 135 Wh kg^-1and 9.8 k W kg^-1.The capacity retention was 83.9%after 8000 cycles at 5A g^-1.（3）Thiourea was added as the nitrogen and sulfur source in the preparation of bamboo liquid-derived porous carbon.The prepared nitrogen and sulfur co-doped bamboo liquid-based porous carbon BLZSC1.Thanks to the doping of nitrogen and sulfur heteroatoms,BLZSC1 cathode exhibits excellent capacitive performance and outstanding cycling stability.It has a high specific capacity of 111.8 m Ah g^-1 at 0.2 A g^-1.The capacity retention rate reaches 85.8%after 2000 cycles at 5 A g^-1.The nitrogen and sulfur co-doped bamboo liquid-based carbon-loaded zinc sulfide anode CZS1 was prepared by the sulfide method.Due to the heteroatom doping and lower inherent conductivity of zinc sulfide than zinc oxide,CZS1anode has excellent rate performance and good cycling stability.The specific capacity at 0.2A g^-1 is 740.5 m Ah g^-1.The capacity retention rate reaches 86.9%after 1000 cycles at 5 A g^-1.The highest energy and power densities of the assembled CZS1//BLZSC1 lithium-ion capacitors are 158Wh kg^-1 and 10 k W kg^-1.The capacity retention rate is 79.2%after 8,000cycles at 5 A g^-1.（4）The hard template magnesium hydroxide was added to the hydrothermal liquefaction precursor of bamboo.The bamboo liquid-based two-dimensional hierarchically porous carbon FPC2 was prepared by using the method of alkali activation coupled with the two-dimensional template.The total pore volume of FPC2 is 2.84 cm³ g^-1 and the mesoporous rate is up to 90%.Due to the high mesoporous volume and two-dimensional flake structure of FPC2,FPC2 cathode exhibits excellent rate performance and outstanding cycling stability.There is still a specific capacity of 48.5 m Ah g^-1 at 10 A g^-1 and the capacity retention rate is 92.6%after 2000 cycles.Then,the two-dimensional hierarchically porous carbon loaded FPC-Si material based on bamboo liquid was prepared by the in-situ growth of nanosilica on FPC2.With the structural advantage of porous flake carbon substrate,the specific capacity of FPC-Si anode is 1385.1 m Ah g^-1 at 0.2 A g^-1,the capacity retention rate is 70.1%after 500 cycles at 5 A g^-1.The highest energy and power densities of the assembled FPC-Si/FPC2 lithium-ion capacitors are 179 Wh kg^-1 and 27.5 k W kg^-1.The capacity retention rate is 82.3%after 8,000 cycles at 5 A g^-1.更多还原