Biomass-derived hard carbons,usually prepared by pyrolysis,are widely considered the most promising anode materials for sodium-ion bat-teries(SIBs)due to their high capacity,low poten-tial,sustainability,cost-effectiv...Biomass-derived hard carbons,usually prepared by pyrolysis,are widely considered the most promising anode materials for sodium-ion bat-teries(SIBs)due to their high capacity,low poten-tial,sustainability,cost-effectiveness,and environ-mental friendliness.The pyrolysis method affects the microstructure of the material,and ultimately its so-dium storage performance.Our previous work has shown that pyrolysis in a sealed graphite vessel im-proved the sodium storage performance of the car-bon,however the changes in its microstructure and the way this influences the sodium storage are still unclear.A series of hard carbon materials derived from corncobs(CCG-T,where T is the pyrolysis temperature)were pyrolyzed in a sealed graphite vessel at different temperatures.As the pyrolysis temperature increased from 1000 to 1400℃ small carbon domains gradually transformed into long and curved domains.At the same time,a greater number of large open pores with uniform apertures,as well as more closed pores,were formed.With the further increase of pyrolysis temperature to 1600℃,the long and curved domains became longer and straighter,and some closed pores gradually became open.CCG-1400,with abundant closed pores,had a superior SIB performance,with an initial reversible ca-pacity of 320.73 mAh g^(-1) at a current density of 30 mA g^(-1),an initial Coulomb efficiency(ICE)of 84.34%,and a capacity re-tention of 96.70%after 100 cycles.This study provides a method for the precise regulation of the microcrystalline and pore structures of hard carbon materials.展开更多
The demand for high-energy-density sodium-ion batteries has driven research to increase the hard carbon(HC)plateau capacity(<0.1 V),but the plateau capacity-rate capability trade-off limits performance.We report a ...The demand for high-energy-density sodium-ion batteries has driven research to increase the hard carbon(HC)plateau capacity(<0.1 V),but the plateau capacity-rate capability trade-off limits performance.We report a way to regulate the closed pore structure and improve the rate capability of HC by the addition of graphene oxide using an emulsification process.In a non-emulsion system,graphene oxide not only shortens ion diffusion paths by inducing the formation of flakelike HC but also significantly improves the rate performance by serving as conductive bridges within the carbon matrix.The prepared graphene/phenolic resin carbon composite has reversible capacities of 362,340,319,274,119,86,69 and 48 mAh g^(−1)at current densities of 0.02,0.05,0.1,0.2,0.5,1,2 and 5 A g^(−1),respectively.When emulsification is introduced,the graphene oxide acts as a nano-confinement template,guiding the cross-linking of phenolic resin to form uniformly sized closed pores.This composite electrode material has the highest plateau capacity of 268 mAh g^(−1)at 20 mA g^(−1).展开更多
The advantages of sodium-ion batteries(SIBs)for large-scale energy storage are well known.Among possible anode materials,hard carbon(HC)stands out as the most viable commercial option because of its superior performan...The advantages of sodium-ion batteries(SIBs)for large-scale energy storage are well known.Among possible anode materials,hard carbon(HC)stands out as the most viable commercial option because of its superior performance.However,there is still disagreement regarding the sodium storage mechanism in the low-voltage plateau region of HC anodes,and the structure-performance relationship between its complex multiscale micro/nanostructure and electrochemical behavior remains unclear.This paper summarizes current research progress and the major problems in understanding HC’s microstructure and sodium storage mechanism,and the relationship between them.Findings about a universal sodium storage mechanism in HC,including predictions about micropore-capacity relationships,and the opportunities and challenges for using HC anodes in commercial SIBs are presented.展开更多
Hard carbon is regarded as a promising anode material for sodium-ion batteries,while it remains a huge challenge to initial coulombic efficiency and rate performance.Numerous studies show that critical structural feat...Hard carbon is regarded as a promising anode material for sodium-ion batteries,while it remains a huge challenge to initial coulombic efficiency and rate performance.Numerous studies show that critical structural features in hard carbon,namely defects,crystallites,and close pores,are directly responsible for the electrochemical performance in sodium-ion batteries.Here,we employ bamboo-derived hard carbon to systematically regulate the defects and crystallites in hard carbon by introducing mechanical activation.Benefiting from ball milling,the intermediate product with a high specific area more easily transforms into hard carbon,which possesses abundant closed pores,effective interlayer spacing,and suitable sodium storage defects,helping to improve the sodium ion storage performance.As a result,the hard carbon ball milled for 20 min presents a high reversible capacity of 315.2 mA·h/g at 17.5 mA/g with an initial coulombic efficiency up to 79.3%,as well as good rate and cycling performances.展开更多
文摘Biomass-derived hard carbons,usually prepared by pyrolysis,are widely considered the most promising anode materials for sodium-ion bat-teries(SIBs)due to their high capacity,low poten-tial,sustainability,cost-effectiveness,and environ-mental friendliness.The pyrolysis method affects the microstructure of the material,and ultimately its so-dium storage performance.Our previous work has shown that pyrolysis in a sealed graphite vessel im-proved the sodium storage performance of the car-bon,however the changes in its microstructure and the way this influences the sodium storage are still unclear.A series of hard carbon materials derived from corncobs(CCG-T,where T is the pyrolysis temperature)were pyrolyzed in a sealed graphite vessel at different temperatures.As the pyrolysis temperature increased from 1000 to 1400℃ small carbon domains gradually transformed into long and curved domains.At the same time,a greater number of large open pores with uniform apertures,as well as more closed pores,were formed.With the further increase of pyrolysis temperature to 1600℃,the long and curved domains became longer and straighter,and some closed pores gradually became open.CCG-1400,with abundant closed pores,had a superior SIB performance,with an initial reversible ca-pacity of 320.73 mAh g^(-1) at a current density of 30 mA g^(-1),an initial Coulomb efficiency(ICE)of 84.34%,and a capacity re-tention of 96.70%after 100 cycles.This study provides a method for the precise regulation of the microcrystalline and pore structures of hard carbon materials.
文摘The demand for high-energy-density sodium-ion batteries has driven research to increase the hard carbon(HC)plateau capacity(<0.1 V),but the plateau capacity-rate capability trade-off limits performance.We report a way to regulate the closed pore structure and improve the rate capability of HC by the addition of graphene oxide using an emulsification process.In a non-emulsion system,graphene oxide not only shortens ion diffusion paths by inducing the formation of flakelike HC but also significantly improves the rate performance by serving as conductive bridges within the carbon matrix.The prepared graphene/phenolic resin carbon composite has reversible capacities of 362,340,319,274,119,86,69 and 48 mAh g^(−1)at current densities of 0.02,0.05,0.1,0.2,0.5,1,2 and 5 A g^(−1),respectively.When emulsification is introduced,the graphene oxide acts as a nano-confinement template,guiding the cross-linking of phenolic resin to form uniformly sized closed pores.This composite electrode material has the highest plateau capacity of 268 mAh g^(−1)at 20 mA g^(−1).
文摘The advantages of sodium-ion batteries(SIBs)for large-scale energy storage are well known.Among possible anode materials,hard carbon(HC)stands out as the most viable commercial option because of its superior performance.However,there is still disagreement regarding the sodium storage mechanism in the low-voltage plateau region of HC anodes,and the structure-performance relationship between its complex multiscale micro/nanostructure and electrochemical behavior remains unclear.This paper summarizes current research progress and the major problems in understanding HC’s microstructure and sodium storage mechanism,and the relationship between them.Findings about a universal sodium storage mechanism in HC,including predictions about micropore-capacity relationships,and the opportunities and challenges for using HC anodes in commercial SIBs are presented.
基金Project(2022RC3048)supported by the Science and Technology Innovation Program of Hunan Province,ChinaProject support by the Guangdong Greenway Technology Co.Ltd.,China。
文摘Hard carbon is regarded as a promising anode material for sodium-ion batteries,while it remains a huge challenge to initial coulombic efficiency and rate performance.Numerous studies show that critical structural features in hard carbon,namely defects,crystallites,and close pores,are directly responsible for the electrochemical performance in sodium-ion batteries.Here,we employ bamboo-derived hard carbon to systematically regulate the defects and crystallites in hard carbon by introducing mechanical activation.Benefiting from ball milling,the intermediate product with a high specific area more easily transforms into hard carbon,which possesses abundant closed pores,effective interlayer spacing,and suitable sodium storage defects,helping to improve the sodium ion storage performance.As a result,the hard carbon ball milled for 20 min presents a high reversible capacity of 315.2 mA·h/g at 17.5 mA/g with an initial coulombic efficiency up to 79.3%,as well as good rate and cycling performances.
