Nitrogen doping has been widely used to improve the performance of carbon electrodes in supercapacitors,particularly in terms of their high-frequency response.However,the charge storage and electrolyte ion response me...Nitrogen doping has been widely used to improve the performance of carbon electrodes in supercapacitors,particularly in terms of their high-frequency response.However,the charge storage and electrolyte ion response mechanisms of different nitrogen dopants at high frequencies are still unclear.In this study,melamine foam carbons with different configurations of surfacedoped N were formed by gradient carbonization,and the effects of the configurations on the high-frequency response behavior of the supercapacitors were analyzed.Using a combination of experiments and first-principle calculations,we found that pyrrolic N,characterized by a higher adsorption energy,increases the charge storage capacity of the electrode at high frequencies.On the other hand,graphitic N,with a lower adsorption energy,increases the speed of ion response.We propose the use of adsorption energy as a practical descriptor for electrode/electrolyte design in high-frequency applications,offering a more universal approach for improving the performance of N-doped carbon materials in supercapacitors.展开更多
有序碳和无序碳都普遍被用作硅(Si)的复合材料。但是具有不同结晶度和孔结构的碳对硅基负极电化学性能的影响仍存在争议。本工作在严格控制碳含量和表面官能团的基础上,选择沥青(Pitch)和酚醛树脂(PR)作为有序碳和无序碳的前驱体,制备...有序碳和无序碳都普遍被用作硅(Si)的复合材料。但是具有不同结晶度和孔结构的碳对硅基负极电化学性能的影响仍存在争议。本工作在严格控制碳含量和表面官能团的基础上,选择沥青(Pitch)和酚醛树脂(PR)作为有序碳和无序碳的前驱体,制备了硅碳复合材料(Si@C)并系统地研究了其电化学行为。有序的晶体结构有利于复合物中的电子传输,中孔和大孔有利于锂离子的扩散。具有有序结构和小孔容的碳质涂层为Si的膨胀提供了很好的缓冲,电极在50次循环后仍保持结构完整性。然而,无序和多孔的结构降低了结构的稳定性并产生了很大的极化,这使得循环过程中体积不断膨胀,导致电化学性能较差。Si@C-Pitch在5 A g^(−1)下的容量是Si@C-PR的8倍,在0.5 A g^(−1)下100次循环后的容量保持率是Si@C-PR的1.9倍。该研究可为Si@C负极中炭材料的选择提供了理论指导。展开更多
文摘Nitrogen doping has been widely used to improve the performance of carbon electrodes in supercapacitors,particularly in terms of their high-frequency response.However,the charge storage and electrolyte ion response mechanisms of different nitrogen dopants at high frequencies are still unclear.In this study,melamine foam carbons with different configurations of surfacedoped N were formed by gradient carbonization,and the effects of the configurations on the high-frequency response behavior of the supercapacitors were analyzed.Using a combination of experiments and first-principle calculations,we found that pyrrolic N,characterized by a higher adsorption energy,increases the charge storage capacity of the electrode at high frequencies.On the other hand,graphitic N,with a lower adsorption energy,increases the speed of ion response.We propose the use of adsorption energy as a practical descriptor for electrode/electrolyte design in high-frequency applications,offering a more universal approach for improving the performance of N-doped carbon materials in supercapacitors.
文摘有序碳和无序碳都普遍被用作硅(Si)的复合材料。但是具有不同结晶度和孔结构的碳对硅基负极电化学性能的影响仍存在争议。本工作在严格控制碳含量和表面官能团的基础上,选择沥青(Pitch)和酚醛树脂(PR)作为有序碳和无序碳的前驱体,制备了硅碳复合材料(Si@C)并系统地研究了其电化学行为。有序的晶体结构有利于复合物中的电子传输,中孔和大孔有利于锂离子的扩散。具有有序结构和小孔容的碳质涂层为Si的膨胀提供了很好的缓冲,电极在50次循环后仍保持结构完整性。然而,无序和多孔的结构降低了结构的稳定性并产生了很大的极化,这使得循环过程中体积不断膨胀,导致电化学性能较差。Si@C-Pitch在5 A g^(−1)下的容量是Si@C-PR的8倍,在0.5 A g^(−1)下100次循环后的容量保持率是Si@C-PR的1.9倍。该研究可为Si@C负极中炭材料的选择提供了理论指导。
