Lithium–sulfur(Li–S)batteries have attracted much attention due to their ultrahigh theoretical specific capacity.However,serious capacity attenuation caused by shuttle effect still inhibits the performance improveme...Lithium–sulfur(Li–S)batteries have attracted much attention due to their ultrahigh theoretical specific capacity.However,serious capacity attenuation caused by shuttle effect still inhibits the performance improvement.Herein,a modified separator consists of the few-layer graphene as a highly conductive network and stable scaffold to support P-doped boron nitride(denoted as BN-P@GO)as the functional interlayer of Li–S batteries.The cell with the interlayer provides an initial discharge capacity as high as1045.3 mAh g^-1,and retains a high reversible capacity of 728.7 mAh g^-1 at 1 C after 500 cycles with a capacity decay of 0.061%per cycle.Moreover,the rate capability is also superior to cells with BN@GO or BN-P interlayers,i.e.reversible capcity of 457.9 mAh g^-1 even at 3 C.The excellent electrochemical performance is ascribed to the synergistic effect of physical barrier and chemical adsorption for dissolved polysulfides provided by the modified layer.Furhtermore,it also mitigates the polarization and promotes kinetic reactions of the cells.This work provides a concise and effective method for commercialization of lithium–sulfur batteries.展开更多
Single-atom catalysts (SACs) especially supported on two-dimensional nitrogen-doped carbon substrate have been widely reported to be able to effectively promote electrocatalytic N_(2) reduction reaction (eNRR). The pr...Single-atom catalysts (SACs) especially supported on two-dimensional nitrogen-doped carbon substrate have been widely reported to be able to effectively promote electrocatalytic N_(2) reduction reaction (eNRR). The precise design of single-metal-atom active site (SMAS) calls for fundamental understanding of its working mechanism for enhanced eNRR performance. Herein, by means of density functional theory calculations, we theoretically investigate the eNRR performance of nine prototypical SMAS, namely, MN_(2)B_(2) (M: transition metals of IIIB, IVB and VB groups) which comprises of asymmetric ligands of N_(2)B_(2) embedded in defective BN nanosheet. Our results reveal the significant role of spin state of SMAS in tuning the potential-determining steps of eNRR, in which MN_(2)B_(2) site with higher spin magnetic moment (μ) is beneficial to reducing limiting potentials (U_(L)) of eNRR. Specially, CrN_(2)B_(2) (μ = 4μB), VN_(2)B_(2) (μ = 3μB) and MoN_(2)B_(2) (μ = 2μB) demonstrate high activity and selectivity to eNRR. The asymmetric ligands of N_(2)B_(2) are deemed to be superior over mono-symmetric ligands. More importantly, our results demonstrate that breaking (or deviating) of the scaling relations between key N-containing intermediates (*N_(2)H/*N_(2) and *NH2/*N_(2)) on MN_(2)B_(2) can be realized by enhancing spin state of SMAS which renders the active site a balanced N-affinity critical for efficient eNRR. This observation is validated by the calculated Sabatier volcano-shape relation between eNRR limiting potentials and N_(2) adsorption energy. Our study develops the guidance for catalyst design to boost eNRR performance by tuning the spin state of an active site.展开更多
基金the financial supports provided by the National Natural Science Foundation of China(21871164)Young Scholars Program of Shandong University(No.2017WLJH15)+2 种基金the China Postdoctoral Science Foundation(Nos.2017M610419 and 2018T110680)the Special Fund for Postdoctoral Innovation Program of Shandong Province(No.201701003)the Taishan Scholar Project of Shandong Province(No.ts201511004)
文摘Lithium–sulfur(Li–S)batteries have attracted much attention due to their ultrahigh theoretical specific capacity.However,serious capacity attenuation caused by shuttle effect still inhibits the performance improvement.Herein,a modified separator consists of the few-layer graphene as a highly conductive network and stable scaffold to support P-doped boron nitride(denoted as BN-P@GO)as the functional interlayer of Li–S batteries.The cell with the interlayer provides an initial discharge capacity as high as1045.3 mAh g^-1,and retains a high reversible capacity of 728.7 mAh g^-1 at 1 C after 500 cycles with a capacity decay of 0.061%per cycle.Moreover,the rate capability is also superior to cells with BN@GO or BN-P interlayers,i.e.reversible capcity of 457.9 mAh g^-1 even at 3 C.The excellent electrochemical performance is ascribed to the synergistic effect of physical barrier and chemical adsorption for dissolved polysulfides provided by the modified layer.Furhtermore,it also mitigates the polarization and promotes kinetic reactions of the cells.This work provides a concise and effective method for commercialization of lithium–sulfur batteries.
基金This work was supported by the National Natural Science Foundation of China(No.21673137)the Science and Technology Commission of Shanghai Municipality(No.16ZR1413900)W.A.gratefully acknowledges the support from the Program for Top Talents in Songjiang District of Shanghai.The DFT calculations were performed using resources of the Center for Functional Nanomaterials,which is a U.S.DOE Office of Science Facility,and the Scientific Data and Computing Center,a component of the Computational Science Initiative,at Brookhaven National Laboratory under Contract No.DE-SC0012704.
文摘Single-atom catalysts (SACs) especially supported on two-dimensional nitrogen-doped carbon substrate have been widely reported to be able to effectively promote electrocatalytic N_(2) reduction reaction (eNRR). The precise design of single-metal-atom active site (SMAS) calls for fundamental understanding of its working mechanism for enhanced eNRR performance. Herein, by means of density functional theory calculations, we theoretically investigate the eNRR performance of nine prototypical SMAS, namely, MN_(2)B_(2) (M: transition metals of IIIB, IVB and VB groups) which comprises of asymmetric ligands of N_(2)B_(2) embedded in defective BN nanosheet. Our results reveal the significant role of spin state of SMAS in tuning the potential-determining steps of eNRR, in which MN_(2)B_(2) site with higher spin magnetic moment (μ) is beneficial to reducing limiting potentials (U_(L)) of eNRR. Specially, CrN_(2)B_(2) (μ = 4μB), VN_(2)B_(2) (μ = 3μB) and MoN_(2)B_(2) (μ = 2μB) demonstrate high activity and selectivity to eNRR. The asymmetric ligands of N_(2)B_(2) are deemed to be superior over mono-symmetric ligands. More importantly, our results demonstrate that breaking (or deviating) of the scaling relations between key N-containing intermediates (*N_(2)H/*N_(2) and *NH2/*N_(2)) on MN_(2)B_(2) can be realized by enhancing spin state of SMAS which renders the active site a balanced N-affinity critical for efficient eNRR. This observation is validated by the calculated Sabatier volcano-shape relation between eNRR limiting potentials and N_(2) adsorption energy. Our study develops the guidance for catalyst design to boost eNRR performance by tuning the spin state of an active site.