A quantitative relationship between safety issues and dendritic lithium(Li) has been rarely investigated yet. Herein the thermal stability of Li deposits with distinct surface area against non-aqueous electrolyte in p...A quantitative relationship between safety issues and dendritic lithium(Li) has been rarely investigated yet. Herein the thermal stability of Li deposits with distinct surface area against non-aqueous electrolyte in pouch-type Li metal batteries is probed. The thermal runaway temperatures of Li metal batteries obtained by accelerating rate calorimeter are reduced from 211 ℃ for Li foil to 111 ℃ for cycled Li.The initial exothermic temperature is reduced from 194 ℃ for routine Li foil to 142 ℃ for 49.5 m~2g^(-1) dendrite. Li with different specific surface areas can regulate the reaction routes during the temperature range from 50 to 300 ℃. The mass percent of Li foil and highly dendritic Li reacting with ethylene carbonate is higher than that of moderately dendritic Li. This contribution can strengthen the understanding of the thermal runaway mechanism and shed fresh light on the rational design of safe Li metal batteries.展开更多
Li–O2 batteries have attracted significant interest in the past decade owing to their superior high specific energy density in contrast to conventional lithium ion batteries.An 8.7-Ah Li–O2 pouch cell with768.5 Wh k...Li–O2 batteries have attracted significant interest in the past decade owing to their superior high specific energy density in contrast to conventional lithium ion batteries.An 8.7-Ah Li–O2 pouch cell with768.5 Wh kg^-1 was fabricated and characterized in this investigation and the factors that influenced the electrochemical performance of the Li–O2 pouch cell were studied.In contrast to coin/Swagelok-type Li–O2 cells,it was demonstrated that the high-loading air electrode,pulverization of the Li anode,and the large-scale inhomogeneity of the large pouch cell are the major reasons for the failure of Li–O2 batteries with Ah capacities.In addition,safety tests of large Li–O2 pouch cells were conducted for the first time,including nail penetration,crushing,and thermal stability.It was indicated that a self-limiting mechanism is a key safety feature of these batteries,even when shorted.In this study,Li–O2 batteries were investigated in a new size and capacity-scale,which may provide useful insight into the development of practical pouch-type Li–O2 batteries.展开更多
Polypyrrole(PPy)is a very promising pseudocapacitive electrode material for supercapacitors.However,the poor electrochemical performances and cycling stability caused by volumetric change and counterion drain severely...Polypyrrole(PPy)is a very promising pseudocapacitive electrode material for supercapacitors.However,the poor electrochemical performances and cycling stability caused by volumetric change and counterion drain severely limited its practical application and commercialization.Herein,we present a pulsepotential polymerization strategy for uniformly depositing a dual-doped PPy with ordered and shorter molecular structure by balancing the concentration polarization.Such a strategy ensures more homogeneous stress distribution of PPy during ultralong cycling tests and improves the cycle stability.Moreover,the pulse-potential polymerized PPy with dual anion doping behavior induces enhanced protonation level and improved electrical conductivity,which boosting the charge transfer kinetics.Therefore,the as-synthesized PPy exhibits a remarkable capacitance performance(7250 mF/cm^(2)@3 mA/cm^(2)),outstanding rate capability(3073 mF/cm^(2)@200 mA/cm^(2))and a long cycle life.The assembled symmetric and asymmetric supercapacitors(ASC)exhibit good energy densities(0.8 mWh/cm^(2) for ASC and 0.5 mWh/cm^(2) for symmetric supercapacitor),and excellent durability with zero capacitive loss after 35,000 cycles.In addition,we have fabricated small pouch devices,which can effectively operate a variety of electronic products(including the high-voltage 5 V smartphone,and tablet)and well withstand the external extreme tests during operation,demonstrating the quantitative investigation of the real-life application of aqueous supercapacitors.展开更多
基金supported by the National Key Research and Development Program(2021YFB2500300)the National Natural Science Foundation of China(22179070,22109084,22075029,and U1932220)+1 种基金the China Postdoctoral Science Foundation(2021TQ0161 and 2021M691709)the Beijing Natural Science Foundation(JQ20004)。
文摘A quantitative relationship between safety issues and dendritic lithium(Li) has been rarely investigated yet. Herein the thermal stability of Li deposits with distinct surface area against non-aqueous electrolyte in pouch-type Li metal batteries is probed. The thermal runaway temperatures of Li metal batteries obtained by accelerating rate calorimeter are reduced from 211 ℃ for Li foil to 111 ℃ for cycled Li.The initial exothermic temperature is reduced from 194 ℃ for routine Li foil to 142 ℃ for 49.5 m~2g^(-1) dendrite. Li with different specific surface areas can regulate the reaction routes during the temperature range from 50 to 300 ℃. The mass percent of Li foil and highly dendritic Li reacting with ethylene carbonate is higher than that of moderately dendritic Li. This contribution can strengthen the understanding of the thermal runaway mechanism and shed fresh light on the rational design of safe Li metal batteries.
基金supported by the Beijing Municipal Science and Technology Project(Grant No.Z181100004518003)GRINM Youth Foundation Funded Project(Contract No.QGL20190060 or Grant No.69963)。
文摘Li–O2 batteries have attracted significant interest in the past decade owing to their superior high specific energy density in contrast to conventional lithium ion batteries.An 8.7-Ah Li–O2 pouch cell with768.5 Wh kg^-1 was fabricated and characterized in this investigation and the factors that influenced the electrochemical performance of the Li–O2 pouch cell were studied.In contrast to coin/Swagelok-type Li–O2 cells,it was demonstrated that the high-loading air electrode,pulverization of the Li anode,and the large-scale inhomogeneity of the large pouch cell are the major reasons for the failure of Li–O2 batteries with Ah capacities.In addition,safety tests of large Li–O2 pouch cells were conducted for the first time,including nail penetration,crushing,and thermal stability.It was indicated that a self-limiting mechanism is a key safety feature of these batteries,even when shorted.In this study,Li–O2 batteries were investigated in a new size and capacity-scale,which may provide useful insight into the development of practical pouch-type Li–O2 batteries.
基金National Natural Science Foundation of China,Grant/Award Number:52071171。
文摘Polypyrrole(PPy)is a very promising pseudocapacitive electrode material for supercapacitors.However,the poor electrochemical performances and cycling stability caused by volumetric change and counterion drain severely limited its practical application and commercialization.Herein,we present a pulsepotential polymerization strategy for uniformly depositing a dual-doped PPy with ordered and shorter molecular structure by balancing the concentration polarization.Such a strategy ensures more homogeneous stress distribution of PPy during ultralong cycling tests and improves the cycle stability.Moreover,the pulse-potential polymerized PPy with dual anion doping behavior induces enhanced protonation level and improved electrical conductivity,which boosting the charge transfer kinetics.Therefore,the as-synthesized PPy exhibits a remarkable capacitance performance(7250 mF/cm^(2)@3 mA/cm^(2)),outstanding rate capability(3073 mF/cm^(2)@200 mA/cm^(2))and a long cycle life.The assembled symmetric and asymmetric supercapacitors(ASC)exhibit good energy densities(0.8 mWh/cm^(2) for ASC and 0.5 mWh/cm^(2) for symmetric supercapacitor),and excellent durability with zero capacitive loss after 35,000 cycles.In addition,we have fabricated small pouch devices,which can effectively operate a variety of electronic products(including the high-voltage 5 V smartphone,and tablet)and well withstand the external extreme tests during operation,demonstrating the quantitative investigation of the real-life application of aqueous supercapacitors.
