Lithium metal anodes are of great interest for advanced high-energy density batteries such as lithiumair, lithium-sulfur and solid-state batteries, due to their low electrode potential and ultra-high theoretical capac...Lithium metal anodes are of great interest for advanced high-energy density batteries such as lithiumair, lithium-sulfur and solid-state batteries, due to their low electrode potential and ultra-high theoretical capacity. There are, however, several challenges limiting their practical applications, which include low coulombic efficiency, the uncontrollable growth of dendrites and poor rate capability. Here, a rational design of 3D structured lithium metal anodes comprising of in-situ growth of cobalt-decorated nitrogen-doped carbon nanotubes on continuous carbon nanofibers is demonstrated via electrospinning.The porous and free-standing scaffold can enhance the tolerance to stresses resulting from the intrinsic volume change during Li plating/stripping, delivering a significant boost in both charge/discharge rates and stable cycling performance. A binary Co-Li alloying phase was generated at the initial discharge process, creating more active sites for the Li nucleation and uniform deposition. Characterization and density functional theory calculations show that the conductive and uniformly distributed cobalt-decorated carbon nanotubes with hierarchical structure can effectively reduce the local current density and more easily absorb Li atoms, leading to more uniform Li nucleation during plating. The current work presents an advance on scalable and cost-effective strategies for novel electrode materials with 3D hierarchical microstructures and mechanical flexibility for lithium metal anodes.展开更多
Sodium-oxygen batteries(Na-O_(2))have attracted extensive attention as promising energy storage systems due to their high energy density and low cost.Redox mediators are often employed to improve Na-O_(2) battery perf...Sodium-oxygen batteries(Na-O_(2))have attracted extensive attention as promising energy storage systems due to their high energy density and low cost.Redox mediators are often employed to improve Na-O_(2) battery performance,however,their effect on the formation mechanism of the oxygen reduction product(NaO_(2))is still unclear.Here,we have investigated the formation mechanism of NaO_(2) during the discharge process in the presence of a redox mediator with the help of atomic/nano-scale in-situ characterization tools used in concert(e.g.atomic force microscope,electrochemical quartz crystal microbalance(EQCM)and laser nano-particle analyzer).As a result,real-time observations on different time scales show that by shuttling electrons to the electrolyte,the redox mediator enables formation of NaO_(2) in the solution-phase instead of within a finite region near the electrode surface.These findings provide new fundamental insights on the understanding of Na-O_(2) batteries and new consequently perspectives on designing high performance metal-O_(2) batteries and other related functions.展开更多
基金kindly supported by the National Natural Science Foundation of China (No. U1864213)the EPSRC Joint UK-India Clean Energy center (JUICE) (EP/P003605/1)+2 种基金the EPSRC Multi-Scale Modelling project (EP/S003053/1)the Innovate UK for Advanced Battery Lifetime Extension (ABLE) projectthe EPSRC for funding under EP/S000933/1。
文摘Lithium metal anodes are of great interest for advanced high-energy density batteries such as lithiumair, lithium-sulfur and solid-state batteries, due to their low electrode potential and ultra-high theoretical capacity. There are, however, several challenges limiting their practical applications, which include low coulombic efficiency, the uncontrollable growth of dendrites and poor rate capability. Here, a rational design of 3D structured lithium metal anodes comprising of in-situ growth of cobalt-decorated nitrogen-doped carbon nanotubes on continuous carbon nanofibers is demonstrated via electrospinning.The porous and free-standing scaffold can enhance the tolerance to stresses resulting from the intrinsic volume change during Li plating/stripping, delivering a significant boost in both charge/discharge rates and stable cycling performance. A binary Co-Li alloying phase was generated at the initial discharge process, creating more active sites for the Li nucleation and uniform deposition. Characterization and density functional theory calculations show that the conductive and uniformly distributed cobalt-decorated carbon nanotubes with hierarchical structure can effectively reduce the local current density and more easily absorb Li atoms, leading to more uniform Li nucleation during plating. The current work presents an advance on scalable and cost-effective strategies for novel electrode materials with 3D hierarchical microstructures and mechanical flexibility for lithium metal anodes.
基金financially supported by Soft Science Research Project of Guangdong Province(No.2017B030301013)the Shenzhen Science and Technology Research(Grant No.JCYJ20170818085823773,ZDSYS201707281026184)+1 种基金China Postdoctoral Science Foundation(2019M660317)the National Science Foundation of China(No.U1864213)。
文摘Sodium-oxygen batteries(Na-O_(2))have attracted extensive attention as promising energy storage systems due to their high energy density and low cost.Redox mediators are often employed to improve Na-O_(2) battery performance,however,their effect on the formation mechanism of the oxygen reduction product(NaO_(2))is still unclear.Here,we have investigated the formation mechanism of NaO_(2) during the discharge process in the presence of a redox mediator with the help of atomic/nano-scale in-situ characterization tools used in concert(e.g.atomic force microscope,electrochemical quartz crystal microbalance(EQCM)and laser nano-particle analyzer).As a result,real-time observations on different time scales show that by shuttling electrons to the electrolyte,the redox mediator enables formation of NaO_(2) in the solution-phase instead of within a finite region near the electrode surface.These findings provide new fundamental insights on the understanding of Na-O_(2) batteries and new consequently perspectives on designing high performance metal-O_(2) batteries and other related functions.