Symmetric secondary batteries are expected to become promising storage devices on account of their low cost,environmentally friendly and high safety.Nevertheless,the further development of symmetric batteries needs to...Symmetric secondary batteries are expected to become promising storage devices on account of their low cost,environmentally friendly and high safety.Nevertheless,the further development of symmetric batteries needs to rely on bipolar electrodes with superior performance.Cation-disordered rocksalt(DRX)Li_(2)FeTiO_(4)shows promising properties as symmetric electrodes,based on the ability of iron to undergo multiple electrochemical reactions over a wide voltage window.Unfortunately,this cation-disordered structure would not provide a cross-path for the rapid migration of Li^(+),ultimately resulting in inferior electrochemical dynamics and cycle stability.Herein,Li_(2)FeTiO_(4)nanoparticles assembled by ultrafine nanocrystals are synthesized via a sol-gel method through an orderly reaction regulation strategy of precursor reactants.Such ultrafine nanocrystals increase the active sites to promote the reversibility of multi-cationic(e.g.,stable Fe^(2+)/Fe^(3+),Ti^(3+)/Ti^(4+)and moderated Fe^(3+)/Fe^(4+))and anionic redox,and maintain the DRX structure well during the cycling process.The half cells with nano-sized Li_(2)FeTiO_(4)as the cathode/anode exhibit a high reversible capacity of 127.8/500.8 mAh/g,respectively.Besides,the Li_(2)FeTiO_(4)//Li_(2)FeTiO_(4)symmetric full cell could provide a reversible capacity of 95.4 mAh/g at 0.1 A/g after 200 cycles.This hierarchical self-assembly by nanocrystal strategy could offer effective guidance for high-performance electrode design for rechargeable secondary batteries.展开更多
The development of cation-disordered rocksalt(DRX)cathodes has garnered worldwide attention due to their high capacity,broad chemical space and excellent structural flexibility.However,their low intrinsic Li-ion condu...The development of cation-disordered rocksalt(DRX)cathodes has garnered worldwide attention due to their high capacity,broad chemical space and excellent structural flexibility.However,their low intrinsic Li-ion conductivity necessitates extensive particle pulverization,typically achieved through ball-milling process,which impedes large-scale production.In this work,we present a proton-exchange assisted strategy to activate the Li-ion transport in Mn-based DRX cathodes.Short-range spinel-like ordering is observed to form within the DRX matrix after the post treatment,which significantly enhances the intrinsic Li ion mobility.Notably,more than 280 mAh g^(-1)discharge capacity can be delivered at a slow rate from micrometer-sized particles with an overall disordered cation arrangement,which retains more than150 m Ah g^(-1)when cycled at a very high rate of 2000 mA g^(-1).Furthermore,we also demonstrate that the electrochemical performance of the post-treated cathodes can be further optimized by fine-tuning the reaction parameters.展开更多
Cation-disordered rocksalt oxides(DRX)have been identified as promising cathode materials for high energy density applications owing to their variable elemental composition and cationic-anionic redox activity.However,...Cation-disordered rocksalt oxides(DRX)have been identified as promising cathode materials for high energy density applications owing to their variable elemental composition and cationic-anionic redox activity.However,their practical implementation has been impeded by unwanted phenomena such as irrepressible transition metal migration/dissolution and O_(2)/CO_(2)evolution,which arise due to parasitic reactions and densification-degradation mechanisms during extended cycling.To address these issues,a micron-sized DRX cathode Li_(1.2)Ni_(1/3)Ti_(1/3)W_(2/15)O_(1.85)F_(0.15)(SLNTWOF)with F substitution and ultrathin LiF coating layer is developed by alcohols assisted sol-gel method.Within this fluorination-induced integrated structure design(FISD)strategy,in-situ F substitution modifies the activity/reversibility of the cationic-anionic redox reaction,while the ultrathin LiF coating and single-crystal structure synergistically mitigate the cathode/electrolyte parasitic reaction and densification-degradation mechanism.Attributed to the multiple modifications and size effect in the FISD strategy,the SLNTWOF sample exhibits reversible cationic-anionic redox chemistry with a meliorated reversible capacity of 290.3 mA h g^(-1)at 0.05C(1C=200 mA g^(-1)),improved cycling stability of 78.5%capacity retention after 50 cycles at 0.5 C,and modified rate capability of 102.8 mA h g^(-1)at 2 C.This work reveals that the synergistic effects between bulk structure modification,surface regulation,and engineering particle size can effectively modulate the distribution and evolution of cationic-anionic redox activities in DRX cathodes.展开更多
Recent success and application of the percolation theory have highlighted cation-disordered Li-rich oxides as high energy density cathode materials. Generally, this kind of cathode materials suffer from low cycling st...Recent success and application of the percolation theory have highlighted cation-disordered Li-rich oxides as high energy density cathode materials. Generally, this kind of cathode materials suffer from low cycling stability and rate performance. Doped Ti4^＋ ions can improve the long-term cycling stability and rate performance of the Li-rich oxides materials with obvious capacity fading. The electrochemical performance in LixNi2-4x/3Sbx/3O2 can benefit a lot from the nanohighway, which is a kind of nanoscale 0-TM diffusion channels in the transition metal layer and provides low diffusion barrier pathways for the lithium diffusion. In this work, the doping effect of Ti on the structure and electrochemical properties in Li1.15Ni0.47Sb0.38O2 is studied. The Ti-stabilized Li1.15-xNi0.47TixSb0.38O2 （x=0, 0.01, 0.03 and 0.05） have been prepared by a solid-state method and the Li1.03Ni0.47Sb0.38Ti0.03O2 sample exhibits outstanding electrochemical performance with a larger reversible discharge capacity, better rate capability and cyclability. Synchrotron-based XANES, combined with ab initio calculations in the multiple-scattering flame- work, reveals the Ti ions have been doped into the Li-site in the lithium layer and formed a distortion TiO6 octahedron. This TiO6 local configuration in the lithium can keep the stability of nanohighway in the electrochemical pro- cess. In particular, the Lil.03Ni0.47Sb0.38Ti0.03O2 compound can deliver a discharge capacities 132 and 76 mAh/g at 0.2 and 5 C, respectivly. About 86% capacity retention occurs at 1 C rate after 500 cycles. This work suggests capacity fading in the oxide cathode materials can be suppressed to construct and stabilize the nanohighway.展开更多
基金supported by the National Natural Science Foundation of China(No.22278347)the Excellent Doctoral Student Research Innovation Project of Xinjiang University of China(No.XJU2022BS048)the Postgraduate Innovation Project of Xinjiang Uygur Autonomous Region of China(No.XJ2023G027)。
文摘Symmetric secondary batteries are expected to become promising storage devices on account of their low cost,environmentally friendly and high safety.Nevertheless,the further development of symmetric batteries needs to rely on bipolar electrodes with superior performance.Cation-disordered rocksalt(DRX)Li_(2)FeTiO_(4)shows promising properties as symmetric electrodes,based on the ability of iron to undergo multiple electrochemical reactions over a wide voltage window.Unfortunately,this cation-disordered structure would not provide a cross-path for the rapid migration of Li^(+),ultimately resulting in inferior electrochemical dynamics and cycle stability.Herein,Li_(2)FeTiO_(4)nanoparticles assembled by ultrafine nanocrystals are synthesized via a sol-gel method through an orderly reaction regulation strategy of precursor reactants.Such ultrafine nanocrystals increase the active sites to promote the reversibility of multi-cationic(e.g.,stable Fe^(2+)/Fe^(3+),Ti^(3+)/Ti^(4+)and moderated Fe^(3+)/Fe^(4+))and anionic redox,and maintain the DRX structure well during the cycling process.The half cells with nano-sized Li_(2)FeTiO_(4)as the cathode/anode exhibit a high reversible capacity of 127.8/500.8 mAh/g,respectively.Besides,the Li_(2)FeTiO_(4)//Li_(2)FeTiO_(4)symmetric full cell could provide a reversible capacity of 95.4 mAh/g at 0.1 A/g after 200 cycles.This hierarchical self-assembly by nanocrystal strategy could offer effective guidance for high-performance electrode design for rechargeable secondary batteries.
基金funding support from the National Natural Science Foundation of Chinathe Institute of WeiqiaoUCAS Science and Technologythe Fundamental Research Funds for the Central Universities。
文摘The development of cation-disordered rocksalt(DRX)cathodes has garnered worldwide attention due to their high capacity,broad chemical space and excellent structural flexibility.However,their low intrinsic Li-ion conductivity necessitates extensive particle pulverization,typically achieved through ball-milling process,which impedes large-scale production.In this work,we present a proton-exchange assisted strategy to activate the Li-ion transport in Mn-based DRX cathodes.Short-range spinel-like ordering is observed to form within the DRX matrix after the post treatment,which significantly enhances the intrinsic Li ion mobility.Notably,more than 280 mAh g^(-1)discharge capacity can be delivered at a slow rate from micrometer-sized particles with an overall disordered cation arrangement,which retains more than150 m Ah g^(-1)when cycled at a very high rate of 2000 mA g^(-1).Furthermore,we also demonstrate that the electrochemical performance of the post-treated cathodes can be further optimized by fine-tuning the reaction parameters.
基金supported by the National Key R&D Program of China(2021YFB2401800)the National Natural Science Foundation of China(22179008,21875022)+2 种基金the Natural Science Foundation of Chongqing,China(cstc2020jcyj-msxmX0589,cstc2020jcyjmsxmX0654)the support from Beijing Institute of Technology Research Fund Program for Young Scholarsthe 4B7B beamlines radiation equipment of Beijing Synchrotron Radiation Facility(2021-BEPC-PT-005924,2021-BEPC-PT-005967)。
文摘Cation-disordered rocksalt oxides(DRX)have been identified as promising cathode materials for high energy density applications owing to their variable elemental composition and cationic-anionic redox activity.However,their practical implementation has been impeded by unwanted phenomena such as irrepressible transition metal migration/dissolution and O_(2)/CO_(2)evolution,which arise due to parasitic reactions and densification-degradation mechanisms during extended cycling.To address these issues,a micron-sized DRX cathode Li_(1.2)Ni_(1/3)Ti_(1/3)W_(2/15)O_(1.85)F_(0.15)(SLNTWOF)with F substitution and ultrathin LiF coating layer is developed by alcohols assisted sol-gel method.Within this fluorination-induced integrated structure design(FISD)strategy,in-situ F substitution modifies the activity/reversibility of the cationic-anionic redox reaction,while the ultrathin LiF coating and single-crystal structure synergistically mitigate the cathode/electrolyte parasitic reaction and densification-degradation mechanism.Attributed to the multiple modifications and size effect in the FISD strategy,the SLNTWOF sample exhibits reversible cationic-anionic redox chemistry with a meliorated reversible capacity of 290.3 mA h g^(-1)at 0.05C(1C=200 mA g^(-1)),improved cycling stability of 78.5%capacity retention after 50 cycles at 0.5 C,and modified rate capability of 102.8 mA h g^(-1)at 2 C.This work reveals that the synergistic effects between bulk structure modification,surface regulation,and engineering particle size can effectively modulate the distribution and evolution of cationic-anionic redox activities in DRX cathodes.
基金Supporting information for this article is available on the WWW under http：//dx.doi.org/10. 1002/cjoc.201700265 or from the author.Acknowledgement This work was partly supported by the Science Fund for Creative Re search Groups of NSF C （No. 11321503）, the National Key Research and Development Program of China （No. 2016YFA0401004）, the National Natural Science Foundation of China （NSFC No. 11275227, U1632103）, and the Youth Innovation Promotion Association CAS （No. 2014927）.
文摘Recent success and application of the percolation theory have highlighted cation-disordered Li-rich oxides as high energy density cathode materials. Generally, this kind of cathode materials suffer from low cycling stability and rate performance. Doped Ti4^＋ ions can improve the long-term cycling stability and rate performance of the Li-rich oxides materials with obvious capacity fading. The electrochemical performance in LixNi2-4x/3Sbx/3O2 can benefit a lot from the nanohighway, which is a kind of nanoscale 0-TM diffusion channels in the transition metal layer and provides low diffusion barrier pathways for the lithium diffusion. In this work, the doping effect of Ti on the structure and electrochemical properties in Li1.15Ni0.47Sb0.38O2 is studied. The Ti-stabilized Li1.15-xNi0.47TixSb0.38O2 （x=0, 0.01, 0.03 and 0.05） have been prepared by a solid-state method and the Li1.03Ni0.47Sb0.38Ti0.03O2 sample exhibits outstanding electrochemical performance with a larger reversible discharge capacity, better rate capability and cyclability. Synchrotron-based XANES, combined with ab initio calculations in the multiple-scattering flame- work, reveals the Ti ions have been doped into the Li-site in the lithium layer and formed a distortion TiO6 octahedron. This TiO6 local configuration in the lithium can keep the stability of nanohighway in the electrochemical pro- cess. In particular, the Lil.03Ni0.47Sb0.38Ti0.03O2 compound can deliver a discharge capacities 132 and 76 mAh/g at 0.2 and 5 C, respectivly. About 86% capacity retention occurs at 1 C rate after 500 cycles. This work suggests capacity fading in the oxide cathode materials can be suppressed to construct and stabilize the nanohighway.
