While alloying transition metal chalcogenides(TMCs)with other chalcogen elements can effectively improve their conductivity and electrochemical properties,the optimal alloying content is still uncertain.In this study,...While alloying transition metal chalcogenides(TMCs)with other chalcogen elements can effectively improve their conductivity and electrochemical properties,the optimal alloying content is still uncertain.In this study,we study the influence of dopant concentration on the chemical bonds in TMC and reveal the associated stepwise conversion reaction mechanism for potassium ion storage.According to density function theory calculations,appropriate S-doping in Co0.85Se(Co_(0.85)Se_(1-x)S_(x))can reduce the average length of Co-Co bonds because of the electronegativity variation,which is thermodynamically favourable to the phase transition reactions.The optimal Se/S ratio(x=0.12)for the conductivity has been obtained from experimental results.When assembled as an anode in potassium-ion batteries(PIBs),the sample with optimized Se/S ratio exhibits extraordinary electrochemical performance.The rate performance(229.2 mA h g^(-1)at 10 A g^(-1))is superior to the state-of-the-art results.When assembled with Prussian blue(PB)as a cathode,the pouch cell exhibits excellent performance,demonstrating its great potential for applications.Moreover,the stepwise K+storage mechanism caused by the coexistence of S and Se is revealed by in-situ X-ray diffraction and ex-situ transmission electron microscopy techniques.Hence,this work not only provides an effective strategy to enhance the electrochemical performance of transition metal chalcogenides but also reveals the underlying mechanism for the construction of advanced electrode materials.展开更多
WS_(2)with layered graphite-like structure as anode for sodium ion batteries has high specific capacity.However,the poor cycling performance and rate capability of WS_(2)caused by the low electronic conductivity and s...WS_(2)with layered graphite-like structure as anode for sodium ion batteries has high specific capacity.However,the poor cycling performance and rate capability of WS_(2)caused by the low electronic conductivity and structure changes during cycles inhibit its practical application.Herein,metallic phase(1T)W_(x)Mo_(1−x)S2(x=1,0.9,0.8 and 0.6)with high electronic conductivity and expanded interlayer spacing of 0.95 nm was directly prepared via a simple hydrothermal method.Specially,1T W_(0.9)Mo_(0.1)S_(2)as anode for sodium ion batteries displays high capacities of 411 mAh g^(-1)at 0.1 A g^(-1)after 180 cycles and 262 mAh g^(-1)at 1 A g^(-1)after 280 cycles and excellent rate capability(245 mAh g^(-1)at 5 A g^(-1)).The full cell based on Na_(3)V_(2)(PO_(4))_(2)O_(2)F/C cathode and 1T W_(0.9)Mo_(0.1)S_(2)anode also exhibits high capacity and good cycling performance.The irreversible electrochemical reaction of 1T W_(0.9)Mo_(0.1)S_(2)with Na ions during first few cycles results in the main products of W-Mo alloy and S.The strong adsorption of W-Mo alloy with polysulfides can effectively suppress the dissolution and shuttle effect of polysulfides,which ensures the excellent cycling performance of 1T W_(0.9)Mo_(0.1)S_(2).展开更多
The photostimulated reactions of benzyl chloride with carbazolyl nitrogen anion in dimethyl sulfoxide gave 9-benzylcarbazole and 3-benzylcarbazole.The reactions are suggested in term of S_(RN) I mechanism of nucleophi...The photostimulated reactions of benzyl chloride with carbazolyl nitrogen anion in dimethyl sulfoxide gave 9-benzylcarbazole and 3-benzylcarbazole.The reactions are suggested in term of S_(RN) I mechanism of nucleophilic substitution.展开更多
基金financially supported by the Natural Science Foundation of Jiangsu Province of China(BK20211172)the Jiangsu Provincial Department of Science and Technology Innovation Support Program(BK20222004,BZ2022036)+1 种基金the National Natural Science Foundation of China(52002366,22075263)the Fundamental Research Funds for the Central Universities(WK2060000039)。
文摘While alloying transition metal chalcogenides(TMCs)with other chalcogen elements can effectively improve their conductivity and electrochemical properties,the optimal alloying content is still uncertain.In this study,we study the influence of dopant concentration on the chemical bonds in TMC and reveal the associated stepwise conversion reaction mechanism for potassium ion storage.According to density function theory calculations,appropriate S-doping in Co0.85Se(Co_(0.85)Se_(1-x)S_(x))can reduce the average length of Co-Co bonds because of the electronegativity variation,which is thermodynamically favourable to the phase transition reactions.The optimal Se/S ratio(x=0.12)for the conductivity has been obtained from experimental results.When assembled as an anode in potassium-ion batteries(PIBs),the sample with optimized Se/S ratio exhibits extraordinary electrochemical performance.The rate performance(229.2 mA h g^(-1)at 10 A g^(-1))is superior to the state-of-the-art results.When assembled with Prussian blue(PB)as a cathode,the pouch cell exhibits excellent performance,demonstrating its great potential for applications.Moreover,the stepwise K+storage mechanism caused by the coexistence of S and Se is revealed by in-situ X-ray diffraction and ex-situ transmission electron microscopy techniques.Hence,this work not only provides an effective strategy to enhance the electrochemical performance of transition metal chalcogenides but also reveals the underlying mechanism for the construction of advanced electrode materials.
基金the support from the National Science Foundation of China(22179071,51772169,51802261,52072217)the Major Technological Innovation Project of Hubei Science and Technology Department(2019AAA164)supported by the Research Project of Education Department of Hubei Province(D20191202)。
文摘WS_(2)with layered graphite-like structure as anode for sodium ion batteries has high specific capacity.However,the poor cycling performance and rate capability of WS_(2)caused by the low electronic conductivity and structure changes during cycles inhibit its practical application.Herein,metallic phase(1T)W_(x)Mo_(1−x)S2(x=1,0.9,0.8 and 0.6)with high electronic conductivity and expanded interlayer spacing of 0.95 nm was directly prepared via a simple hydrothermal method.Specially,1T W_(0.9)Mo_(0.1)S_(2)as anode for sodium ion batteries displays high capacities of 411 mAh g^(-1)at 0.1 A g^(-1)after 180 cycles and 262 mAh g^(-1)at 1 A g^(-1)after 280 cycles and excellent rate capability(245 mAh g^(-1)at 5 A g^(-1)).The full cell based on Na_(3)V_(2)(PO_(4))_(2)O_(2)F/C cathode and 1T W_(0.9)Mo_(0.1)S_(2)anode also exhibits high capacity and good cycling performance.The irreversible electrochemical reaction of 1T W_(0.9)Mo_(0.1)S_(2)with Na ions during first few cycles results in the main products of W-Mo alloy and S.The strong adsorption of W-Mo alloy with polysulfides can effectively suppress the dissolution and shuttle effect of polysulfides,which ensures the excellent cycling performance of 1T W_(0.9)Mo_(0.1)S_(2).
文摘The photostimulated reactions of benzyl chloride with carbazolyl nitrogen anion in dimethyl sulfoxide gave 9-benzylcarbazole and 3-benzylcarbazole.The reactions are suggested in term of S_(RN) I mechanism of nucleophilic substitution.
