MXene-based aqueous symmetric supercapacitors(SSCs)are attractive due to their good rate performances and green nature.However,it remains a challenge to reach voltages much over 1.2 V,which significantly diminishes th...MXene-based aqueous symmetric supercapacitors(SSCs)are attractive due to their good rate performances and green nature.However,it remains a challenge to reach voltages much over 1.2 V,which significantly diminishes their energy density.Herein,we report on Mo_(1.33)CTz MXene-based SSCs possessing high voltages in a 19.5 M LiCl electrolyte.Benefiting from the vacancy-rich structure and high stable potential window of Mo_(1.33)CTz,the obtained SSCs deliver a maximum energy density of>38.2 mWh cm^(-3) at a power density of 196.6 mW cm^(-3) under an operating voltage of 1.4 V,along with excellent rate performance and impressive cycling stability.This highly concentrated LiCl electrolyte is also applicable to Ti_(3)C_(2)Tz,the most widely studied MXene,achieving a maximum energy density of>41.3 mWh cm^(-3) at a power density of 165.2 mW cm^(-3) with an operating voltage of 1.8 V.The drop in energy density with increasing power in the Ti_(3)C_(2)Tz cells was steeper than for the Mo-based cells.This work provides a roadmap to develop superior SSCs with high voltages and high energy densities.展开更多
Electrochromic(EC)materials that change color with voltage have been widely studied for use in dynamic windows.However,colorless-to-colorful switching with high contrast ratio is generically unattainable,especially fo...Electrochromic(EC)materials that change color with voltage have been widely studied for use in dynamic windows.However,colorless-to-colorful switching with high contrast ratio is generically unattainable,especially for colorless-to-black electrochromic materials with an ultrahigh contrast ratio over the entire visible region.In this work,we developed Nb_(1.33)C MXene-based dynamic windows with colorless-to-black switching of up to 75%reversible change in transmittance from 300 to 1,500 nm.By exploring the electrochromic effects of different electrolytes through in situ optical changes and electrochemical quartz crystal microbalance(EQCM),it is found that electrochromic behavior is greatly influenced by the extent of reversible Li^(+)insertion/deinsertion between the two-dimensional Nb_(1.33)C MXene nanosheets.In addition,a colorless-to-black EC device based on Nb_(1.33)C with an overall integrated contrast ratio over 80%was successfully constructed by a solution-processable spin coating method.This work enables a simple route to fabricate MXene-based high-performance electrochromic smart windows,which is important for further expanding the application of MXenes to optoelectronic and photonic applications.展开更多
Assembly of two-dimensional (2D) nanomaterials into well-organized architectures is pivotal for controlling their function and enhancing performance. As a promising class of 2D nanomaterials, MXenes have attracted sig...Assembly of two-dimensional (2D) nanomaterials into well-organized architectures is pivotal for controlling their function and enhancing performance. As a promising class of 2D nanomaterials, MXenes have attracted significant interest for use in wearable electronics due to their unique electrical and mechanical properties. However, facile approaches for fabricating MXenes into macroscopic fibers with controllable structures are limited. In this study, we present a strategy for easily spinning MXene fibers by incorporating polyanions. The introduction of poly(acrylic acid) (PAA) into MXene colloids has been found to alter MXene aggregation behavior, resulting in a reduced concentration threshold for lyotropic liquid crystal phase. This modification also enhances the viscosity and shear sensitivity of MXene colloids. Consequently, we were able to draw continuous fibers directly from the gel of MXene aggregated with PAA. These fibers exhibit homogeneous diameter and high alignment of MXene nanosheets, attributed to the shear-induced long-range order of the liquid crystal phase. Furthermore, we demonstrate proof-of-concept applications of the ordered MXene fibers, including textile-based supercapacitor, sensor and electrical thermal management, highlighting their great potential applied in wearable electronics. This work provides a guideline for processing 2D materials into controllable hierarchical structures by regulating aggregation behavior through the addition of ionic polymers.展开更多
基金supported by the Swedish Foundation for Strategic Research(SSF)EM16-0004.
文摘MXene-based aqueous symmetric supercapacitors(SSCs)are attractive due to their good rate performances and green nature.However,it remains a challenge to reach voltages much over 1.2 V,which significantly diminishes their energy density.Herein,we report on Mo_(1.33)CTz MXene-based SSCs possessing high voltages in a 19.5 M LiCl electrolyte.Benefiting from the vacancy-rich structure and high stable potential window of Mo_(1.33)CTz,the obtained SSCs deliver a maximum energy density of>38.2 mWh cm^(-3) at a power density of 196.6 mW cm^(-3) under an operating voltage of 1.4 V,along with excellent rate performance and impressive cycling stability.This highly concentrated LiCl electrolyte is also applicable to Ti_(3)C_(2)Tz,the most widely studied MXene,achieving a maximum energy density of>41.3 mWh cm^(-3) at a power density of 165.2 mW cm^(-3) with an operating voltage of 1.8 V.The drop in energy density with increasing power in the Ti_(3)C_(2)Tz cells was steeper than for the Mo-based cells.This work provides a roadmap to develop superior SSCs with high voltages and high energy densities.
基金This work was financed by the SSF Research Infrastructure Fellow Program(No.RIF 14–0074)the SSF Synergy Program EM16–0004,and by the Knut and Alice Wallenberg(KAW)Foundation through a Fellowship Grant,a Project Grant(No.KAW2020.0033)+4 种基金for support of the electron microscopy laboratory in Linköping University.Support from the National Natural Science Foundation of China(No.61774077)the Guangdong Joint Research Fund(No.2020A1515110738)the Postdoctoral Research Foundation of China(No.2020M683187)the Key Projects of Joint Fund of Basic and Applied Basic Research Fund of Guangdong Province(No.2019B1515120073)the Guangzhou Key laboratory of Vacuum Coating Technologies and New Energy Materials Open Projects Fund(No.KFVE20200006)are also acknowledged.
文摘Electrochromic(EC)materials that change color with voltage have been widely studied for use in dynamic windows.However,colorless-to-colorful switching with high contrast ratio is generically unattainable,especially for colorless-to-black electrochromic materials with an ultrahigh contrast ratio over the entire visible region.In this work,we developed Nb_(1.33)C MXene-based dynamic windows with colorless-to-black switching of up to 75%reversible change in transmittance from 300 to 1,500 nm.By exploring the electrochromic effects of different electrolytes through in situ optical changes and electrochemical quartz crystal microbalance(EQCM),it is found that electrochromic behavior is greatly influenced by the extent of reversible Li^(+)insertion/deinsertion between the two-dimensional Nb_(1.33)C MXene nanosheets.In addition,a colorless-to-black EC device based on Nb_(1.33)C with an overall integrated contrast ratio over 80%was successfully constructed by a solution-processable spin coating method.This work enables a simple route to fabricate MXene-based high-performance electrochromic smart windows,which is important for further expanding the application of MXenes to optoelectronic and photonic applications.
基金financially supported this work through a Project Grant(No.KAW2020.0033)We acknowledge Myfab at Uppsala University for providing facilities and experimental support+2 种基金Myfab is funded by the Swedish Research Council(No.2019-00207)as a Swedish national research infrastructureThe authors acknowledge the financial support by the Fundamental Research Funds for the Central Universities of China(No.20822041H4077)ÅForsk Foundation.
文摘Assembly of two-dimensional (2D) nanomaterials into well-organized architectures is pivotal for controlling their function and enhancing performance. As a promising class of 2D nanomaterials, MXenes have attracted significant interest for use in wearable electronics due to their unique electrical and mechanical properties. However, facile approaches for fabricating MXenes into macroscopic fibers with controllable structures are limited. In this study, we present a strategy for easily spinning MXene fibers by incorporating polyanions. The introduction of poly(acrylic acid) (PAA) into MXene colloids has been found to alter MXene aggregation behavior, resulting in a reduced concentration threshold for lyotropic liquid crystal phase. This modification also enhances the viscosity and shear sensitivity of MXene colloids. Consequently, we were able to draw continuous fibers directly from the gel of MXene aggregated with PAA. These fibers exhibit homogeneous diameter and high alignment of MXene nanosheets, attributed to the shear-induced long-range order of the liquid crystal phase. Furthermore, we demonstrate proof-of-concept applications of the ordered MXene fibers, including textile-based supercapacitor, sensor and electrical thermal management, highlighting their great potential applied in wearable electronics. This work provides a guideline for processing 2D materials into controllable hierarchical structures by regulating aggregation behavior through the addition of ionic polymers.
