Layered double hydroxides(LDHs)are potential cathode materials for aqueous magnesium-ion batteries(AMIBs).However,the low capacity and sluggish kinetics significantly limit their electrochemical performance in AMIBs.H...Layered double hydroxides(LDHs)are potential cathode materials for aqueous magnesium-ion batteries(AMIBs).However,the low capacity and sluggish kinetics significantly limit their electrochemical performance in AMIBs.Herein,we find that oxygen vacancies can significantly boost the capacity,electrochemical kinetics,and structure stability of LDHs.The corresponding structure-performance relationship and energy storage mechanism are elaborated through exhaustive in/ex-situ experimental characterizations and density functional theory(DFT)calculations.Specially,in-situ Raman and DFT calculations reveal that oxygen vacancies elevate orbital energy of O 2p and electron density of O atoms,thereby enhancing the orbital hybridization of O 2p with Ni/Co 3d.This facilitates electron transfer between O and adjacent Ni/Co atoms and improves the covalency of Ni–O and Co–O bonds,which activates Ni/Co atoms to release more capacity and stabilizes the Ov-NiCo-LDH structure.Moreover,the distribution of relaxation times(DRT)and molecular dynamics(MD)simulations disclose that the enhanced d-p orbital hybridization optimizes the electronic structure of Ov-NiCo-LDH,which distinctly reduces the diffusion energy barriers of Mg^(2+)and improves the charge transfer kinetics of Ov-NiCo-LDH.Consequently,the assembled Ov-NiCo-LDH//active carbon(AC)and Ov-NiCo-LDH//perylenediimide(PTCDI)AMIBs can both deliver high specific discharge capacity(182.7 and 59.4 mAh g^(−1)at 0.5 A g^(−1),respectively)and long-term cycling stability(85.4%and 89.0%of capacity retentions after 2500 and 2400 cycles at 1.0 A g^(−1),respectively).In addition,the practical prospects for Ov-NiCo-LDH-based AMIBs have been demonstrated in different application scenarios.This work not only provides an effective strategy for obtaining high-performance cathodes of AMIBs,but also fundamentally elucidates the inherent mechanisms.展开更多
Air-rechargeable aqueous Zn-based batteries(ARAZBBs)possess their typical air self-charge advantage.Unfortunately,their further development is beset by two major challenges:an ultrashort air-charge lifespan due to the...Air-rechargeable aqueous Zn-based batteries(ARAZBBs)possess their typical air self-charge advantage.Unfortunately,their further development is beset by two major challenges:an ultrashort air-charge lifespan due to the formation of'dead Zn'(basic zinc salt,BZS)deposited on the cathode surface and the severe corrosion of Zn anode due to continuous consumption of Zn during the air-charge process.Aiming at untying these Gordian knots,herein,an effective dead-zinc activation method of in-situ electrochemical conversion successfully activates'dead zinc'in BZS and repairs the Zn anode simultaneously.Specifically,the specific discharge capacity of as-prepared nitrogen-doped hierarchically porous carbon(NHPC)declines rapidly from 132.4 to 36.8 mAh g^(-1)at 0.2 A g^(-1)after only the 5th air-charge due to a large amount of dead zinc formation.To recover these failed NHPC electrodes,we skillfully draw support from in-situ electrochemical conversion to successfully eliminate BZS on the NHPC during the galvanostatic charging process.More importantly,the method also recovers Zn resources from'dead zinc'to well repair Zn anode,providing a viable solution to address the issue of continuous consumption of Zn.As a result,the air-rechargeable specific capacity of NHPC has been significantly improved from 36.8 to118.9 mAh g^(-1)at 0.2 A g^(-1)by using this effective dead-zinc activation method.Meanwhile,related mechanisms to charge-storage,air-charge,and in-situ electrochemical conversion are clearly revealed by a series of in-/ex-situ tests.This work lays the foundation for the wider practical application of ARAZBBs.展开更多
基金financial support of the National Natural Science Foundation of China (22379063)
文摘Layered double hydroxides(LDHs)are potential cathode materials for aqueous magnesium-ion batteries(AMIBs).However,the low capacity and sluggish kinetics significantly limit their electrochemical performance in AMIBs.Herein,we find that oxygen vacancies can significantly boost the capacity,electrochemical kinetics,and structure stability of LDHs.The corresponding structure-performance relationship and energy storage mechanism are elaborated through exhaustive in/ex-situ experimental characterizations and density functional theory(DFT)calculations.Specially,in-situ Raman and DFT calculations reveal that oxygen vacancies elevate orbital energy of O 2p and electron density of O atoms,thereby enhancing the orbital hybridization of O 2p with Ni/Co 3d.This facilitates electron transfer between O and adjacent Ni/Co atoms and improves the covalency of Ni–O and Co–O bonds,which activates Ni/Co atoms to release more capacity and stabilizes the Ov-NiCo-LDH structure.Moreover,the distribution of relaxation times(DRT)and molecular dynamics(MD)simulations disclose that the enhanced d-p orbital hybridization optimizes the electronic structure of Ov-NiCo-LDH,which distinctly reduces the diffusion energy barriers of Mg^(2+)and improves the charge transfer kinetics of Ov-NiCo-LDH.Consequently,the assembled Ov-NiCo-LDH//active carbon(AC)and Ov-NiCo-LDH//perylenediimide(PTCDI)AMIBs can both deliver high specific discharge capacity(182.7 and 59.4 mAh g^(−1)at 0.5 A g^(−1),respectively)and long-term cycling stability(85.4%and 89.0%of capacity retentions after 2500 and 2400 cycles at 1.0 A g^(−1),respectively).In addition,the practical prospects for Ov-NiCo-LDH-based AMIBs have been demonstrated in different application scenarios.This work not only provides an effective strategy for obtaining high-performance cathodes of AMIBs,but also fundamentally elucidates the inherent mechanisms.
基金financial support of the National Natural Science Foundation of China(22379063)。
文摘Air-rechargeable aqueous Zn-based batteries(ARAZBBs)possess their typical air self-charge advantage.Unfortunately,their further development is beset by two major challenges:an ultrashort air-charge lifespan due to the formation of'dead Zn'(basic zinc salt,BZS)deposited on the cathode surface and the severe corrosion of Zn anode due to continuous consumption of Zn during the air-charge process.Aiming at untying these Gordian knots,herein,an effective dead-zinc activation method of in-situ electrochemical conversion successfully activates'dead zinc'in BZS and repairs the Zn anode simultaneously.Specifically,the specific discharge capacity of as-prepared nitrogen-doped hierarchically porous carbon(NHPC)declines rapidly from 132.4 to 36.8 mAh g^(-1)at 0.2 A g^(-1)after only the 5th air-charge due to a large amount of dead zinc formation.To recover these failed NHPC electrodes,we skillfully draw support from in-situ electrochemical conversion to successfully eliminate BZS on the NHPC during the galvanostatic charging process.More importantly,the method also recovers Zn resources from'dead zinc'to well repair Zn anode,providing a viable solution to address the issue of continuous consumption of Zn.As a result,the air-rechargeable specific capacity of NHPC has been significantly improved from 36.8 to118.9 mAh g^(-1)at 0.2 A g^(-1)by using this effective dead-zinc activation method.Meanwhile,related mechanisms to charge-storage,air-charge,and in-situ electrochemical conversion are clearly revealed by a series of in-/ex-situ tests.This work lays the foundation for the wider practical application of ARAZBBs.
