A convenient,effcient and environmentally benign procedure has been developed for the synthesis of pyrano[4,3-b]pyran derivatives via a one-pot,three-component reaction of 4-hydroxy-6-methylpyran-2-one,aldehydes and m...A convenient,effcient and environmentally benign procedure has been developed for the synthesis of pyrano[4,3-b]pyran derivatives via a one-pot,three-component reaction of 4-hydroxy-6-methylpyran-2-one,aldehydes and malononitrile in water using H6P2W18O62á18H2O as catalyst.Reusability of the catalyst and reaction media,short reaction times and easy isolation of products are some added advantages of the present methodology.展开更多
Direct regeneration is considered a sustainable solution to the issue of resource recycling and the environmental pollution caused by discarded lithium-ion batteries(LIBs).However,the direct regeneration of spent LiFe...Direct regeneration is considered a sustainable solution to the issue of resource recycling and the environmental pollution caused by discarded lithium-ion batteries(LIBs).However,the direct regeneration of spent LiFePO_(4)cathode materials still faces a formidable challenge that the irregular strains induced by the irreversible FePO_(4)phase after several charge and discharge cycles hinder the regenerative replenishment of Li^(+).This work proposes a lattice stress modulation strategy that reduces FePO_(4)phase into Fe_(2)P_(2)O_(7)phase(reduction of unit cell volume from 271.7 to 122.6Å^(3)),which releases the residual stress,paving continuous transport channels for Li^(+).In addition,the phase transformation reconstructs the FeO6 octahedra,significantly decreasing the migration energy barrier of ions within the lattice.Ultimately,the steric effect is synergistically weakened,facilitating the replenishment of Li^(+)and the elimination of Li-Fe anti-site defects.The regenerated LiFePO_(4)cathodes outperform commercial cathodes(80.2%capacity retention after 1000 cycles at 2 C).This work establishes fundamental principles for the pretreatment stage of the direct regeneration process and provides a paradigm shifting solution for sustainable LIBs recycling technology.展开更多
In this work,for the first time,it is demonstrated that during the insertion/extraction of Na ions,the structural evolution at the Na_(4)site at a voltage range of 3-4 V is a key factor for the capacity decay of Na_(4...In this work,for the first time,it is demonstrated that during the insertion/extraction of Na ions,the structural evolution at the Na_(4)site at a voltage range of 3-4 V is a key factor for the capacity decay of Na_(4)Fe_(3)(PO_(4))_(2)P_(2)O_(7)(NFPP).Herein,a strategy of introducing columnar potassium ions at the Na_(4)site is proposed to address the aforementioned challenge.As a cathode material for sodium-ion batteries,the K_(0.12)Na_(3.88)Fe_(3)(PO_(4))_(2)P_(2)O_(7)/C(K-NFPP)composite enhances the reversibility of Na_(4)extraction.Specifically,the K-NFPP exhibits an initial discharge capacity of 107.8 mAh g^(-1)at a high current density of 5 C,with a capacity retention of 91.4% after 2000 cycles,outperforming the pristine NFPP material(81.1 m Ah g^(-1)and 67.1%).At 5 C,the K-NFPP also retains 81.5% of the reversible capacity at 0.1 C,whereas the NFPP only retains 68.3%.Moreover,the K-NFPP-based full-cell delivers an initial capacity of 110.1 m Ah g^(-1)at 1 C,with a capacity retention of 90% after 100 cycles.It is found that in comparison to K-doping of the Na1,Na2,and Na3 sites,K-doping at the Na4 site effectively optimizes the band gap and stabilizes the crystal structure,thereby reducing lattice changes of FeO_(6)evolution during Na^(+)insertion/extraction.As a result,the introduction of columnar potassium ions significantly enhances the capacity contribution of the Na_(4)site,optimizes reaction kinetics,and effectively mitigates the capacity decay of NFPP cathodes.It is believed that this study offers a new entry point for the application of NFPP in high-voltage sodium storage.展开更多
文摘A convenient,effcient and environmentally benign procedure has been developed for the synthesis of pyrano[4,3-b]pyran derivatives via a one-pot,three-component reaction of 4-hydroxy-6-methylpyran-2-one,aldehydes and malononitrile in water using H6P2W18O62á18H2O as catalyst.Reusability of the catalyst and reaction media,short reaction times and easy isolation of products are some added advantages of the present methodology.
基金supported by the National Natural Science Foundation of China(52433002)Key projects of Shaanxi Province(2023GXLH-001)+2 种基金Key R&D Program of Shandong Province(2022TSGC2569)New Energy Material Innovation Consortium Projects of Yunnan Province(202302AB080018)Natural Science Basic Research Program of Shaanxi(2022TD-27)。
文摘Direct regeneration is considered a sustainable solution to the issue of resource recycling and the environmental pollution caused by discarded lithium-ion batteries(LIBs).However,the direct regeneration of spent LiFePO_(4)cathode materials still faces a formidable challenge that the irregular strains induced by the irreversible FePO_(4)phase after several charge and discharge cycles hinder the regenerative replenishment of Li^(+).This work proposes a lattice stress modulation strategy that reduces FePO_(4)phase into Fe_(2)P_(2)O_(7)phase(reduction of unit cell volume from 271.7 to 122.6Å^(3)),which releases the residual stress,paving continuous transport channels for Li^(+).In addition,the phase transformation reconstructs the FeO6 octahedra,significantly decreasing the migration energy barrier of ions within the lattice.Ultimately,the steric effect is synergistically weakened,facilitating the replenishment of Li^(+)and the elimination of Li-Fe anti-site defects.The regenerated LiFePO_(4)cathodes outperform commercial cathodes(80.2%capacity retention after 1000 cycles at 2 C).This work establishes fundamental principles for the pretreatment stage of the direct regeneration process and provides a paradigm shifting solution for sustainable LIBs recycling technology.
基金financial support from the National Natural Science Foundation of China(52272237,22279101 and 22172117)the Natural Science Foundation of Shaanxi(2020JC-41 and 2024JC-YBQN-0141)+2 种基金the Scientific Research Program Funded by the Education Department of Shaanxi Provincial Government(22JP056)the S&T Program of Energy Shaanxi Laboratory(ESLB202402)the Foshan Science and Technology Innovation Team Project(1920001004098)。
文摘In this work,for the first time,it is demonstrated that during the insertion/extraction of Na ions,the structural evolution at the Na_(4)site at a voltage range of 3-4 V is a key factor for the capacity decay of Na_(4)Fe_(3)(PO_(4))_(2)P_(2)O_(7)(NFPP).Herein,a strategy of introducing columnar potassium ions at the Na_(4)site is proposed to address the aforementioned challenge.As a cathode material for sodium-ion batteries,the K_(0.12)Na_(3.88)Fe_(3)(PO_(4))_(2)P_(2)O_(7)/C(K-NFPP)composite enhances the reversibility of Na_(4)extraction.Specifically,the K-NFPP exhibits an initial discharge capacity of 107.8 mAh g^(-1)at a high current density of 5 C,with a capacity retention of 91.4% after 2000 cycles,outperforming the pristine NFPP material(81.1 m Ah g^(-1)and 67.1%).At 5 C,the K-NFPP also retains 81.5% of the reversible capacity at 0.1 C,whereas the NFPP only retains 68.3%.Moreover,the K-NFPP-based full-cell delivers an initial capacity of 110.1 m Ah g^(-1)at 1 C,with a capacity retention of 90% after 100 cycles.It is found that in comparison to K-doping of the Na1,Na2,and Na3 sites,K-doping at the Na4 site effectively optimizes the band gap and stabilizes the crystal structure,thereby reducing lattice changes of FeO_(6)evolution during Na^(+)insertion/extraction.As a result,the introduction of columnar potassium ions significantly enhances the capacity contribution of the Na_(4)site,optimizes reaction kinetics,and effectively mitigates the capacity decay of NFPP cathodes.It is believed that this study offers a new entry point for the application of NFPP in high-voltage sodium storage.
