Silicon anodes are promising for use in lithium-ion batteries.However,their practical application is severely limited by their large volume expansion leading to irreversible material fracture and electrical disconnect...Silicon anodes are promising for use in lithium-ion batteries.However,their practical application is severely limited by their large volume expansion leading to irreversible material fracture and electrical disconnects.This study proposes a new top-down strategy for preparing microsize porous silicon and introduces polyacrylonitrile(PAN)for a nitrogen-doped carbon coating,which is designed to maintain the internal pore volume and lower the expansion of the anode during lithiation and delithiation.We then explore the effect of temperature on the evolution of the structure of PAN and the electrochemical behavior of the composite electrode.After treatment at 400℃,the PAN coating retains a high nitrogen content of 11.35 at%,confirming the presence of C—N and C—O bonds that improve the ionic-electronic transport properties.This treatment not only results in a more intact carbon layer structure,but also introduces carbon defects,and produces a material that has remarkable stable cycling even at high rates.When cycled at 4 A g^(-1),the anode had a specific capacity of 857.6 mAh g^(-1) even after 200 cycles,demonstrating great potential for high-capacity energy storage applications.展开更多
二维炭材料引起了研究人员广泛的关注,然而,其复杂的合成方法、非均匀的结构以及难以精确控制的性质限制了这一形貌控制科学的发展。本研究开发了一种普适性的制备方法,通过简便的化学交联反应,利用吡咯和吲哚作为氮源,3,4-乙烯二氧噻...二维炭材料引起了研究人员广泛的关注,然而,其复杂的合成方法、非均匀的结构以及难以精确控制的性质限制了这一形貌控制科学的发展。本研究开发了一种普适性的制备方法,通过简便的化学交联反应,利用吡咯和吲哚作为氮源,3,4-乙烯二氧噻吩作为硫源,制备了一系列杂原子掺杂的二维多孔聚合物。这种自下而上的策略能够实现高杂原子含量、丰富孔性结构和超薄厚度的功能化炭纳米片的大规模合成。因此,所得到的氮掺杂炭纳米片作为锂离子电容器负极,在5 A g^(-1)条件下表现出573.4 mAh g^(-1)的比容量,而经优化的氮掺杂炭纳米片作为锂离子电容器正极,在5 A g^(-1)条件下表现出100.0 F g^(-1)的比电容。基于此,开发了一种双碳离子电容器,在400 W kg^(-1)条件下,168.4 Wh kg^(-1)的能量密度,循环10000次后循环稳定性保持在86.3%。值得注意的是,这种自下而上的策略为大规模精确定制具有目标结构和性质的二维功能化炭纳米片开辟了新途径。展开更多
碳点(CDs)因其较大的比表面积和较快的电子转移特性,已成为能量转换应用领域一种新兴的纳米炭材料。本文以低成本的石油焦为原料,通过简便的一步电化学刻蚀方法制备了硼氮双掺杂碳点(BN-CDs)。与单掺杂碳点B-CDs和N-CDs相比,双掺杂BN-CD...碳点(CDs)因其较大的比表面积和较快的电子转移特性,已成为能量转换应用领域一种新兴的纳米炭材料。本文以低成本的石油焦为原料,通过简便的一步电化学刻蚀方法制备了硼氮双掺杂碳点(BN-CDs)。与单掺杂碳点B-CDs和N-CDs相比,双掺杂BN-CDs表现出更优异的四电子氧还原电催化活性,具有更正的起始电位(Eonset=0.958 V)和大的扩散极限电流密度(j D=-4.32 mA cm~(-2)),且长期稳定性和甲醇耐受性优于商用Pt/C催化剂。密度泛函理论计算(DFT)研究表明,B、N双掺杂的协同效应促进了O_2分子的吸附,有助于提高碳点的电催化活性。本研究为纳米炭材料的设计及其在能量转换领域的应用提供了新的思路。展开更多
文摘Silicon anodes are promising for use in lithium-ion batteries.However,their practical application is severely limited by their large volume expansion leading to irreversible material fracture and electrical disconnects.This study proposes a new top-down strategy for preparing microsize porous silicon and introduces polyacrylonitrile(PAN)for a nitrogen-doped carbon coating,which is designed to maintain the internal pore volume and lower the expansion of the anode during lithiation and delithiation.We then explore the effect of temperature on the evolution of the structure of PAN and the electrochemical behavior of the composite electrode.After treatment at 400℃,the PAN coating retains a high nitrogen content of 11.35 at%,confirming the presence of C—N and C—O bonds that improve the ionic-electronic transport properties.This treatment not only results in a more intact carbon layer structure,but also introduces carbon defects,and produces a material that has remarkable stable cycling even at high rates.When cycled at 4 A g^(-1),the anode had a specific capacity of 857.6 mAh g^(-1) even after 200 cycles,demonstrating great potential for high-capacity energy storage applications.
文摘二维炭材料引起了研究人员广泛的关注,然而,其复杂的合成方法、非均匀的结构以及难以精确控制的性质限制了这一形貌控制科学的发展。本研究开发了一种普适性的制备方法,通过简便的化学交联反应,利用吡咯和吲哚作为氮源,3,4-乙烯二氧噻吩作为硫源,制备了一系列杂原子掺杂的二维多孔聚合物。这种自下而上的策略能够实现高杂原子含量、丰富孔性结构和超薄厚度的功能化炭纳米片的大规模合成。因此,所得到的氮掺杂炭纳米片作为锂离子电容器负极,在5 A g^(-1)条件下表现出573.4 mAh g^(-1)的比容量,而经优化的氮掺杂炭纳米片作为锂离子电容器正极,在5 A g^(-1)条件下表现出100.0 F g^(-1)的比电容。基于此,开发了一种双碳离子电容器,在400 W kg^(-1)条件下,168.4 Wh kg^(-1)的能量密度,循环10000次后循环稳定性保持在86.3%。值得注意的是,这种自下而上的策略为大规模精确定制具有目标结构和性质的二维功能化炭纳米片开辟了新途径。
文摘碳点(CDs)因其较大的比表面积和较快的电子转移特性,已成为能量转换应用领域一种新兴的纳米炭材料。本文以低成本的石油焦为原料,通过简便的一步电化学刻蚀方法制备了硼氮双掺杂碳点(BN-CDs)。与单掺杂碳点B-CDs和N-CDs相比,双掺杂BN-CDs表现出更优异的四电子氧还原电催化活性,具有更正的起始电位(Eonset=0.958 V)和大的扩散极限电流密度(j D=-4.32 mA cm~(-2)),且长期稳定性和甲醇耐受性优于商用Pt/C催化剂。密度泛函理论计算(DFT)研究表明,B、N双掺杂的协同效应促进了O_2分子的吸附,有助于提高碳点的电催化活性。本研究为纳米炭材料的设计及其在能量转换领域的应用提供了新的思路。
