Anionic redox reaction(ARR) in layered manganese-based oxide cathodes has been considered as an effective strategy to improve the energy density of sodium-ion batteries.Mn-vacancy layered oxides deliver a high ARR-rel...Anionic redox reaction(ARR) in layered manganese-based oxide cathodes has been considered as an effective strategy to improve the energy density of sodium-ion batteries.Mn-vacancy layered oxides deliver a high ARR-related capacity with small voltage hysteresis,however,they are limited by rapid capacity degradation and poor rate capability,which arise from inferior structure changes due to repeated redox of lattice oxygen.Herein,redox-inactive Ti^(4+)is introduced to substitute partial Mn^(4+)to form Na_(2) Ti_(0.5)Mn_(2.5)O_7(Na_(4/7)[□_(1/7)Ti_(1/7)Mn_(5/7)]O_(2),□ for Mn vacancies),which can effectively restrain unfavorable interlayer gliding of Na2 Mn307 at high charge voltages,as reflected by an ultralow-strain volume variation of 0.11%.There is no irreversible O_(2) evolution observed in Na_(2) Ti_(0.5)Mn_(2.5)O_7 upon charging,which stabilizes the lattice oxygen and ensures the overall structural stability.It exhibits increased capacity retention of 79.1% after 60 cycles in Na_(2) Ti_(0.5)Mn_(2.5)O_7(17.1% in Na_(2) Mn_(3) O_7) and good rate capability(92.1 mAh g^(-1) at 0.5 A g^(-1)).This investigation provides new insights into designing high-performance cathode materials with reversible ARR and structural stability for SIBs.展开更多
Developing low-cost and high performance catalysts to replace precious metal based catalysts for oxygen reduction reaction(ORR) is one of the most feasible ways to promote the commercial application of fuel cells.In t...Developing low-cost and high performance catalysts to replace precious metal based catalysts for oxygen reduction reaction(ORR) is one of the most feasible ways to promote the commercial application of fuel cells.In this work,flower-like CoS and octahedral CoS_2 are synthesized by a facile one-pot hydrothermal method without any adjunction of surfactants or follow-up thermolysis,their catalytic performance towards ORR in alkaline electrolyte are comparatively investigated.The results reveal that CoS_2 outperforms CoS owing to the higher electron density around S-S bond of S_2^(2-) in the crystal structure,which promotes the adsorption of oxygen on catalyst surface and facilitates the breakage of O-O bond in oxygen,leading to direct 4-electron transfer ORR.When CoS_2 particles are dispersed on the surface of rGO with large surface area,their ORR performance could be further improved.展开更多
基金Financial supports from the National Natural Science Foundation of China (21822506 and 51761165025)the Tianjin Natural Science Foundation (19JCJQJC62400)the 111 project of B12015。
文摘Anionic redox reaction(ARR) in layered manganese-based oxide cathodes has been considered as an effective strategy to improve the energy density of sodium-ion batteries.Mn-vacancy layered oxides deliver a high ARR-related capacity with small voltage hysteresis,however,they are limited by rapid capacity degradation and poor rate capability,which arise from inferior structure changes due to repeated redox of lattice oxygen.Herein,redox-inactive Ti^(4+)is introduced to substitute partial Mn^(4+)to form Na_(2) Ti_(0.5)Mn_(2.5)O_7(Na_(4/7)[□_(1/7)Ti_(1/7)Mn_(5/7)]O_(2),□ for Mn vacancies),which can effectively restrain unfavorable interlayer gliding of Na2 Mn307 at high charge voltages,as reflected by an ultralow-strain volume variation of 0.11%.There is no irreversible O_(2) evolution observed in Na_(2) Ti_(0.5)Mn_(2.5)O_7 upon charging,which stabilizes the lattice oxygen and ensures the overall structural stability.It exhibits increased capacity retention of 79.1% after 60 cycles in Na_(2) Ti_(0.5)Mn_(2.5)O_7(17.1% in Na_(2) Mn_(3) O_7) and good rate capability(92.1 mAh g^(-1) at 0.5 A g^(-1)).This investigation provides new insights into designing high-performance cathode materials with reversible ARR and structural stability for SIBs.
基金financially supported National Natural Science Foundation of China(No.21476138)Shandong Provincial Natural Science Foundation(No.ZR2018MB036)+1 种基金Science Development Project of Shandong Province(Nos.2017GGX40115 and2016GGX102038)Project of Shandong Province Higher Educational Science and Technology Program(Nos.J17KA094,J13LD08)。
文摘Developing low-cost and high performance catalysts to replace precious metal based catalysts for oxygen reduction reaction(ORR) is one of the most feasible ways to promote the commercial application of fuel cells.In this work,flower-like CoS and octahedral CoS_2 are synthesized by a facile one-pot hydrothermal method without any adjunction of surfactants or follow-up thermolysis,their catalytic performance towards ORR in alkaline electrolyte are comparatively investigated.The results reveal that CoS_2 outperforms CoS owing to the higher electron density around S-S bond of S_2^(2-) in the crystal structure,which promotes the adsorption of oxygen on catalyst surface and facilitates the breakage of O-O bond in oxygen,leading to direct 4-electron transfer ORR.When CoS_2 particles are dispersed on the surface of rGO with large surface area,their ORR performance could be further improved.
