The cobalt-free Mn-based Li-rich layered oxide material has the advantages of low cost,high energy density,and good performance at low temperatures,and is the promising choice for energy storage batteries.However,the ...The cobalt-free Mn-based Li-rich layered oxide material has the advantages of low cost,high energy density,and good performance at low temperatures,and is the promising choice for energy storage batteries.However,the long-cycling stability of batteries needs to be improved.Herein,the Mn-based Li-rich cathode materials with small amounts of Li2 MnO3 crystal domains and gradient doping of Al and Ti elements from the surface to the bulk have been developed to improve the structure and interface stability.Then the batteries with a high energy density of 600 Wh kg^(-1),excellent capacity retention of 99.7%with low voltage decay of 0.03 mV cycle^(-1) after 800 cycles,and good rates performances can be achieved.Therefore,the structure and cycling stability of low voltage Mn-based Li-rich cathode materials can be significantly improved by the bulk structure design and interface regulation,and this work has paved the way for developing low-cost and high-energy Mn-based energy storage batteries with long lifetime.展开更多
Layered transition metal oxides have emerged as promising cathode materials for sodium ion batteries.However,irreversible phase transitions cause structural distortion and cation rearrangement,leading to sluggish Na+d...Layered transition metal oxides have emerged as promising cathode materials for sodium ion batteries.However,irreversible phase transitions cause structural distortion and cation rearrangement,leading to sluggish Na+dynamics and rapid capacity decay.In this study,we propose a medium-entropy cathode by simultaneously introducing Fe,Mg,and Li dopants into a typical P2-type Na_(0.75)Ni_(0.25)Mn_(0.75)O_(2)cathode.The modified Na_(0.75)Ni_(0.2125)Mn_(0.6375)Fe_(0.05)Mg_(0.05)Li_(0.05)O_(2)cathode predominantly exhibits a main P2 phase(93.5%)with a minor O3 phase(6.5%).Through spectroscopy techniques and electrochemical investigations,we elucidate the redox mechanisms of Ni^(2+/3+/4+),Mn^(3+/4+),Fe^(3+/4+),and O_(2)-/O_(2)^(n-)during charging/discharging.The medium-entropy doping mitigates the detrimental P2-O_(2)phase transition at high-voltage,replacing it with a moderate and reversible structural evolution(P2-OP4),thereby enhancing structural stability.Consequently,the modified cathode exhibits a remarkable rate capacity of 108.4 mAh·g^(-1)at 10C,with a capacity retention of 99.0%after 200 cycles at 1C,82.5%after 500 cycles at 5C,and 76.7%after 600 cycles at 10C.Furthermore,it also demonstrates superior electrochemical performance at high cutoff voltage of 4.5 V and extreme temperature(55 and 0℃).This work offers solutions to critical challenges in sodium ion batteries cathode materials.展开更多
03-type layered oxide serves as dominant components in sodium ion batteries;however,the unstable electronic structure between transition metal and oxygen inevitably induces framework instability and severe kinetic hin...03-type layered oxide serves as dominant components in sodium ion batteries;however,the unstable electronic structure between transition metal and oxygen inevitably induces framework instability and severe kinetic hindrance.In this study,a two-in-one approach to synergistically modulate the local electro nic and interfacial structure of NaNi_(1/3)Fe_(1/3)Mn_(1/3)O_(2)by Ce modification is proposed.We present an indepth study to reveal the strong-covalent Ce-O bonds,which make local charge around oxygen more negative,enhance O 2p-Mn 3d hybridization,and preserve the octahedral structural integrity.This modification tailors local electronic structure between the octahedral metal center and oxygen,thus enhancing reversibility of 03-P3-03 phase transition and expanding Na+octahedral-tetrahedral-octahedral transport channel.Additionally,the nanoscale perovskite layer induced by Ce element is in favor of minimizing interfacial side reaction as well as enhancing Na^(+)diffusivity.As a result,the designed 03-NaNi_(0.305)Fe_(0.33)Mn_(0.33)Ce_(0.025)O_(2)material delivers an exceptionally low volume variation,an ultrahigh rate capacity of 76.9 mA h g^(-1)at 10 C,and remarkable cycling life over 250 cycles with capacity retention of 80% at 5 C.展开更多
P2/O3-type Ni/Mn-based layered oxides are promising cathode materials for sodium-ion batteries(SIBs)owing to their high energy density.However,exploring effective ways to enhance the synergy between the P2 and 03 phas...P2/O3-type Ni/Mn-based layered oxides are promising cathode materials for sodium-ion batteries(SIBs)owing to their high energy density.However,exploring effective ways to enhance the synergy between the P2 and 03 phases remains a necessity.Herein,we design a P2/O3-type Na_(0.76)Ni_(0.31)Zn_(0.07)Mn_(0.50)Ti_(0.12)0_(2)(NNZMT)with high chemical/electrochemical stability by enhancing the coupling between the two phases.For the first time,a unique Na*extraction is observed from a Na-rich O3 phase by a Na-poor P2 phase and systematically investigated.This process is facilitated by Zn^(2+)/Ti^(4+)dual doping and calcination condition regulation,allowing a higher Na*content in the P2 phase with larger Na^(+)transport channels and enhancing Na transport kinetics.Because of reduced Na^(+)in the O3 phase,which increases the difficulty of H^(+)/Na^(+) exchange,the hydrostability of the O3 phase in NNZMT is considerably improved.Furthermore,Zn^(2+)/Ti^(4+)presence in NNZMT synergistically regulates oxygen redox chemistry,which effectively suppresses O_(2)/CO_(2) gas release and electrolyte decomposition,and completely inhibits phase transitions above 4.0 V.As a result,NNZMT achieves a high discharge capacity of 144.8 mA h g^(-1) with a median voltage of 3.42 V at 20 mA g^(-1) and exhibits excellent cycling performance with a capacity retention of 77.3% for 1000 cycles at 2000 mA g^(-1).This study provides an effective strategy and new insights into the design of high-performance layered-oxide cathode materials with enhanced structure/interface stability forSIBs.展开更多
Undoubtedly,the enormous progress observed in recent years in the Ni-rich layered cathode materials has been crucial in terms of pushing boundaries of the Li-ion battery(LIB)technology.The achieved improvements in the...Undoubtedly,the enormous progress observed in recent years in the Ni-rich layered cathode materials has been crucial in terms of pushing boundaries of the Li-ion battery(LIB)technology.The achieved improvements in the energy density,cyclability,charging speed,reduced costs,as well as safety and stability,already contribute to the wider adoption of LIBs,which extends nowadays beyond mobile electronics,power tools,and electric vehicles,to the new range of applications,including grid storage solutions.With numerous published papers and broad reviews already available on the subject of Ni-rich oxides,this review focuses more on the most recent progress and new ideas presented in the literature references.The covered topics include doping and composition optimization,advanced coating,concentration gradient and single crystal materials,as well as innovations concerning new electrolytes and their modification,with the application of Ni-rich cathodes in solid-state batteries also discussed.Related cathode materials are briefly mentioned,with the high-entropy approach and zero-strain concept presented as well.A critical overview of the still unresolved issues is given,with perspectives on the further directions of studies and the expected gains provided.展开更多
The voltage decay of lithium-rich layered oxides(LLOs)is still one of the key challenges for their application in commercial battery although these materials possess the advantages of high specific capacity and low co...The voltage decay of lithium-rich layered oxides(LLOs)is still one of the key challenges for their application in commercial battery although these materials possess the advantages of high specific capacity and low cost.In this work,the relationship between voltage decay and tap density of LLOs has been focused.The voltage decay can be significantly suppressed with the increasing tap density as well as the homogenization of the primary or secondary particle size of agglomerated spherical LLOs.Experimental results have shown that an extreme small voltage decay of 0.98 m V cycle^(-1)can be obtained through adjusting the tap density of agglomerated spherical LLOs to 1.99 g cm^(-3),in which the size of primary and secondary particles are uniform.Our work offers a new insight towards the voltage decay and capacity fading of LLOs through precursor preparation process,promoting their application in the real battery in the future.展开更多
In this paper, the superhydrophobic polyurethane sponge(SS-PU) was facilely fabricated by etching with Jones reagent to bind the nanoparticles of Ni-Co double layered oxides(LDOs) on the surface, and following modific...In this paper, the superhydrophobic polyurethane sponge(SS-PU) was facilely fabricated by etching with Jones reagent to bind the nanoparticles of Ni-Co double layered oxides(LDOs) on the surface, and following modification with n-dodecyl mercaptan(DDT). This method provides a new strategy to fabricate superhydrophobic PU sponge with a water contact angle of 157° for absorbing oil with low cost and in large scale. It exhibits the strong absorption capacity and highly selective characteristic for various kinds of oils which can be recycled by simple squeezing. Besides, the as-prepared sponge can deal with the floating and underwater oils, indicating its application value in handling oil spills and domestic oily wastewater. The good self-cleaning ability shows the potential to clear the pollutants due to the ultralow adhesion to water. Especially, the most important point is that the superhydrophobic sponge can continuously and effectively separate the oil/water mixture against the condition of turbulent disturbance by using our designed device system, which exhibit its good superhydrophobicity, strong stability.Furthermore, the SS-PU still maintained stable absorption performance after 150 cycle tests without losing capacity obviously, showing excellent durability in long-term operation and significant potential as an efficient absorbent in large-scale dispose of oily water.展开更多
Lithium-rich layered oxides(LLOs)are promising candidate cathode materials for safe and inexpensive high-energy-density Li-ion batteries.However,oxygen dimers are formed from the cathode material through oxygen redox ...Lithium-rich layered oxides(LLOs)are promising candidate cathode materials for safe and inexpensive high-energy-density Li-ion batteries.However,oxygen dimers are formed from the cathode material through oxygen redox activity,which can result in morphological changes and structural transitions that cause performance deterioration and safety concerns.Herein,a flake-like LLO is prepared and aberration-corrected scanning transmission electron microscopy(STEM),in situ high-temperature X-ray diffraction(HT-XRD),and soft X-ray absorption spectrum(sXAS)are used to explore its crystal facet degradation behavior in terms of both thermal and electrochemical processes.Void-induced degradation behavior of LLO in different facet reveals significant anisotropy at high voltage.Particle degradation originates from side facets,such as the(010)facet,while the close(003)facet is stable.These results are further understood through ab initio molecular dynamics calculations,which show that oxygen atoms are lost from the{010}facets.Therefore,the facet degradation process is that oxygen molecular formed in the interlayer and accumulated in the ab plane during heating,which result in crevice-voids in the ab plane facets.The study reveals important aspects of the mechanism responsible for oxygen-anionic activity-based degradation of LLO cathode materials used in lithium-ion batteries.In particular,this study provides insight that enables precise and efficient measures to be taken to improve the thermal and electrochemical stability of an LLO.展开更多
Sodium-ion batteries are very promising in large-scale energy storage.The exploration of Na layered oxides as cathode materials for Na ion batteries usually consumes much resource,while the performances of Na layered ...Sodium-ion batteries are very promising in large-scale energy storage.The exploration of Na layered oxides as cathode materials for Na ion batteries usually consumes much resource,while the performances of Na layered oxides are dominated by their crystal structures.Therefore,it is highly desired to predict the stacking mode of the target oxides in advance:whether O3-type with higher ordered structure and stability,or P2-type with more Na content.For this purpose density functional theory computations do not work.Very recently,Hu's group and international collaborators have proposed a cationic potential to provide a very timely,effective,and accurate criterion to predict the stacking mode of Na layered oxides(Science,370(2020)708-711).Under the guidance of the cationic potential phase map,Na layered oxides could be rationally designed.Here we would like to highlight the progress that novel Na layered oxides could be obtained with the combination of large specific capacity,high power density and good cycling stability.展开更多
Though oxygen defects are associated with deteriorated structures and aggravated cycling performance in traditional layered cathodes,the role of oxygen defects is still ambiguous in Li-rich layered oxides due to the i...Though oxygen defects are associated with deteriorated structures and aggravated cycling performance in traditional layered cathodes,the role of oxygen defects is still ambiguous in Li-rich layered oxides due to the involvement of oxygen redox.Herein,a Co-free Li-rich layered oxide Li_(1.286)Ni_(0.071)Mn_(0.643)O_(2)has been prepared by a co-precipitation method to systematically investigate the undefined effects of the oxygen defects.A significant O_(2)release and the propagation of oxygen vacancies were detected by operando differential electrochemical mass spectroscopy(DEMS)and electron energy loss spectroscopy(EELS),respectively.Scanning transmission electron microscopy-high angle annular dark field(STEMHAADF)reveals the oxygen vacancies fusing to nanovoids and monitors a stepwise electrochemical activation process of the large Li_(2)MnO_(3)domain upon cycling.Combined with the quantitative analysis conducted by the energy dispersive spectrometer(EDS),existed nano-scale oxygen defects actually expose more surface to the electrolyte for facilitating the electrochemical activation and subsequently increasing available capacity.Overall,this work persuasively elucidates the function of oxygen defects on oxygen redox in Co-free Li-rich layered oxides.展开更多
Anionic redox reaction(ARR) in layered manganese-based oxide cathodes has been considered as an effective strategy to improve the energy density of sodium-ion batteries.Mn-vacancy layered oxides deliver a high ARR-rel...Anionic redox reaction(ARR) in layered manganese-based oxide cathodes has been considered as an effective strategy to improve the energy density of sodium-ion batteries.Mn-vacancy layered oxides deliver a high ARR-related capacity with small voltage hysteresis,however,they are limited by rapid capacity degradation and poor rate capability,which arise from inferior structure changes due to repeated redox of lattice oxygen.Herein,redox-inactive Ti^(4+)is introduced to substitute partial Mn^(4+)to form Na_(2) Ti_(0.5)Mn_(2.5)O_7(Na_(4/7)[□_(1/7)Ti_(1/7)Mn_(5/7)]O_(2),□ for Mn vacancies),which can effectively restrain unfavorable interlayer gliding of Na2 Mn307 at high charge voltages,as reflected by an ultralow-strain volume variation of 0.11%.There is no irreversible O_(2) evolution observed in Na_(2) Ti_(0.5)Mn_(2.5)O_7 upon charging,which stabilizes the lattice oxygen and ensures the overall structural stability.It exhibits increased capacity retention of 79.1% after 60 cycles in Na_(2) Ti_(0.5)Mn_(2.5)O_7(17.1% in Na_(2) Mn_(3) O_7) and good rate capability(92.1 mAh g^(-1) at 0.5 A g^(-1)).This investigation provides new insights into designing high-performance cathode materials with reversible ARR and structural stability for SIBs.展开更多
Lithium-rich layered oxides(LrLOs) deliver extremely high specific capacities and are considered to be promising candidates for electric vehicle and smart grid applications. However, the application of LrLOs needs fur...Lithium-rich layered oxides(LrLOs) deliver extremely high specific capacities and are considered to be promising candidates for electric vehicle and smart grid applications. However, the application of LrLOs needs further understanding of the structural complexity and dynamic evolution of monoclinic and rhombohedral phases, in order to overcome the issues including voltage decay, poor rate capability, initial irreversible capacity loss and etc. The development of aberration correction for the transmission electron microscope and concurrent progress in electron spectroscopy, have fueled rapid progress in the understanding of the mechanism of such issues. New techniques based on the transmission electron microscope are first surveyed, and the applications of these techniques for the study of the structure, migration of transition metal, and the activation of oxygen of LrLOs are then explored in detail, with a particular focus on the mechanism of voltage decay.展开更多
Nickel-rich layered oxides(LiNixCoyMnzO2,NCM)are among the most promising cathode materials for high-energy lithium-ion batteries,offering high specific capacity and output voltage at a relatively low cost.However,ind...Nickel-rich layered oxides(LiNixCoyMnzO2,NCM)are among the most promising cathode materials for high-energy lithium-ion batteries,offering high specific capacity and output voltage at a relatively low cost.However,industrialscale co-precipitation presents significant challenges,particularly in maintaining particle sphericity,ensuring a stable concentration gradient,and preserving production yield when transitioning from lab-scale compositions.This study addresses a critical issue in the large-scale synthesis of nickel-rich NCM(x=0.8381):nickel leaching,which compromises particle uniformity and battery performance.To mitigate this,we optimize the reaction process and develop an artificial intelligence-driven defect prediction system that enhances precursor stability.Our domain adaptation based machine learning model,which accounts for equipment wear and environmental variations,achieves a defect detection accuracy of 97.8%based on machine data and process conditions.By implementing this approach,we successfully scale up NCM precursor production to over 2 tons,achieving 83%capacity retention after 500 cycles at a 1C rate.In addition,the proposed approach demonstrates the formation of a concentration gradient in the composition and a high sphericity of 0.951(±0.0796).This work provides new insights into the stable mass production of NCM precursors,ensuring both high yield and performance reliability.展开更多
The development of sustainable energy storage solutions has driven research toward alternatives to lithiumion batteries.Sodium-ion battery(SIB)was considered a promising candidate due to their cost-effectiveness and s...The development of sustainable energy storage solutions has driven research toward alternatives to lithiumion batteries.Sodium-ion battery(SIB)was considered a promising candidate due to their cost-effectiveness and sodium abundance.To introduce defects and enhance the electrochemical performance of O_(3)-phase sodium-ion layered oxide materials,high-temperature shock(HTS)was employed.However,given the characteristics of HTS,especially the rapid heating rate and short sintering time,suitable precursor systems need to be explored.We systematically compared three precursor systems:traditional metal oxides(HTS-O),decomposable salts(HTS-D),and a novel pre-reacted precursor system(HTS-S).The pre-reacted precursor,developed by leveraging the ethanol solubility of C_(4)H_(14)MnO_(8) and modified ball milling conditions,enabled rapid O_(3) phase formation and resulted in impurity-free O_(3)-NaCu_(0.2)Fe_(0.3)Mn _(0.5)O_(2).This material demonstrated superior electrochemical performance,achieving a discharge capacity of 144.05 mAh g^(−1) within 2.0-4.1 V,along with enhanced rate capabilities.Our findings underscore the critical role of precursor selection and modification in HTS synthesis,contributing to the advancement of high-performance sodium-ion battery materials.展开更多
The burgeoning growth in electric vehicles and portable energy storage systems necessitates advances in the energy density and cost-effectiveness of lithium-ion batteries(LIBs),areas where lithium-rich manganese-based...The burgeoning growth in electric vehicles and portable energy storage systems necessitates advances in the energy density and cost-effectiveness of lithium-ion batteries(LIBs),areas where lithium-rich manganese-based oxide(LLO)materials naturally stand out.Despite their inherent advantages,these materials encounter significant practical hurdles,including low initial Coulombic efficiency(ICE),diminished cycle/rate performance,and voltage fading during cycling,hindering their widespread adoption.In response,we introduce an ionic-electronic dual-conductive(IEDC)surface control strategy that integrates an electronically conductive graphene framework with an ionically conductive heteroepitaxial spinel Li_(4)Mn_(5)O_(12)layer.Prolonged electrochemical and structural analyses demonstrate that this IEDC heterostructure effectively minimizes polarization,mitigates structural distortion,and enhances electronic/ionic diffusion.Density functional theory calculations highlight an extensive Li^(+)percolation network and lower Li^(+)migration energies at the layered-spinel interface.The designed LLO cathode with IEDC interface engineering(LMOSG)exhibits improved ICE(82.9%at 0.1 C),elevated initial discharge capacity(296.7 mAh g^(-1)at 0.1 C),exceptional rate capability(176.5 mAh g^(-1)at 5 C),and outstanding cycle stability(73.7%retention at 5 C after 500 cycles).These findings and the novel dual-conductive surface architecture design offer promising directions for advancing highperformance electrode materials.展开更多
The undesirable capacity loss after first cycle is universal among layered cathode materials,which results in the capacity and energy decay.The key to resolving this obstacle lies in understanding the effect and origi...The undesirable capacity loss after first cycle is universal among layered cathode materials,which results in the capacity and energy decay.The key to resolving this obstacle lies in understanding the effect and origin of specific active Li sites during discharge process.In this study,focusing on Ah-level pouch cells for reliability,an ultrahigh initial Coulombic efficiency(96.1%)is achieved in an archetypical Li-rich layered oxide material.Combining the structure and electrochemistry analysis,we demonstrate that the achievement of high-capacity reversibility is a kinetic effect,primarily related to the sluggish Li mobility during oxygen reduction.Activating oxygen reduction through small density would induce the oxygen framework contraction,which,according to Pauli repulsion,imposes a great repulsive force to hinder the transport of tetrahedral Li.The tetrahedral Li storage upon deep oxygen reduction is experimentally visualized and,more importantly,contributes to 6%Coulombic efficiency enhancement as well as 10%energy density improvement for pouch cells,which shows great potentials breaking through the capacity and energy limitation imposed by intercalation chemistry.展开更多
Nickel-rich(Ni≥90%)layered oxides materials have emerged as a promising candidate for nextgeneration high-energy-density lithium-ion batteries(LIBs).However,their widespread application is hindered by structural fati...Nickel-rich(Ni≥90%)layered oxides materials have emerged as a promising candidate for nextgeneration high-energy-density lithium-ion batteries(LIBs).However,their widespread application is hindered by structural fatigue and lattice oxygen loss.In this work,an epitaxial surface rock-salt nanolayer is successfully developed on the LiNi_(0.9)Co_(0.1)O_(2)sub-surface via heteroatom anchoring utilizing high-valence element molybdenum modification.This in-situ formed conformal buffer phase with a thickness of 1.2 nm effectively suppresses the continuous interphase side-reactions,and thus maintains the excellent structure integrity at high voltage.Furthermore,theoretical calculations indicate that the lattice oxygen reversibility in the anion framework of the optimized sample is obviously enhanced due to the higher content of O 2p states near the Fermi level than that of the pristine one.Meanwhile,the stronger Mo-O bond further reduces cell volume alteration,which improves the bulk structure stability of modified materials.Besides,the detailed charge compensation mechanism suggests that the average oxidation state of Ni is reduced,which induces more active Li+participating in the redox reactions,boosting the cell energy density.As a result,the uniquely designed cathode materials exhibit an extraordinary discharge capacity of 245.4 mAh g^(-1)at 0.1 C,remarkable rate performance of 169.3 mAh g^(-1)at 10 C at 4.5 V,and a high capacity retention of 70.5% after 1000 cycles in full cells at a high cut-off voltage of 4.4 V.This strategy provides an valuable insight into constructing distinctive heterostructure on highperformance Ni-rich layered cathodes for LIBs.展开更多
CONSPECTUS:Li-rich layered oxides have received extensive attention as promising high-energy-density cathodes for next-generation Li-ion batteries.Different from traditional cathodes such as LiCoO2,LiFePO4,and Li2MnO4...CONSPECTUS:Li-rich layered oxides have received extensive attention as promising high-energy-density cathodes for next-generation Li-ion batteries.Different from traditional cathodes such as LiCoO2,LiFePO4,and Li2MnO4,Li-rich oxides generally can harvest superior discharge capacities exceeding 250 mAh g−1,which originated from the contribution of oxygen redox chemistry.However,lattice oxygen release and irreversible TM transition would induce severe structure distortion and capacity degradation as well as voltage attenuation within Li-rich cathodes during electrochemical processes,which greatly limits their industrial applications in next-generation Li-ion batteries.展开更多
Sodium-ion batteries(SIBs)employ P2-type layered transition metal oxides as promising cathode materials,primarily due to their abundant natural reserves and environmentally friendly characteristics.However,structural ...Sodium-ion batteries(SIBs)employ P2-type layered transition metal oxides as promising cathode materials,primarily due to their abundant natural reserves and environmentally friendly characteristics.However,structural instability and complex phase transitions during electrochemical cycling pose significant challenges to their practical applications.Employing cation substitution serves as a straightforward yet effective strategy for stabilizing the structure and improving the kinetics of the active material.In this study,we introduce a Ni-rich honeycomb-layered Na_(2+x)Ni_(2)TeO_(6)(NNTO)cathode material with variable sodium content(x=0,0.03,0.05,0.10).Physicochemical characterizations reveal that excess sodium content at the atomic scale modifies the surface and suppresses phase transitions,while preserving the crystal structure.This results in enhanced cyclic performance and improved electrochemical kinetics at room temperature.Furthermore,we investigate the performance of the NNTO cathode material containing 10%excess sodium at a relatively high temperature of 60℃,where it exhibits 71.6%capacity retention compared to 60%for the pristine.Overall,our results confirm that a preconstructed surface layer(induced by excess sodium)effectively safeguards the Ni-based cathode material from surface degradation and phase transitions during the electrochemical processes,thus exhibiting superior capacity retention relative to the pristine NNTO cathode.This study of the correlation between structure and performance can potentially be applied to the commercialization of SIBs.展开更多
The detrimental phase transformations of sodium layered transition metal oxides(Na_(x)TMO_(2))during desodiation/sodiation seriously suppress their practical applications for sodium ion batteries(SIBs).Undoubtedly,com...The detrimental phase transformations of sodium layered transition metal oxides(Na_(x)TMO_(2))during desodiation/sodiation seriously suppress their practical applications for sodium ion batteries(SIBs).Undoubtedly,comprehensively investigating of the dynamic crystal structure evolutions of Na_(x)TMO_(2)associating with Na ions extraction/intercalation and then deeply understanding of the relationships between electrochemical performances and phase structures drawing support from advanced characterization techniques are indispensable.In-situ high-energy X-ray diffraction(HEXRD),a powerful technology to distinguish the crystal structure of electrode materials,has been widely used to identify the phase evolutions of Na_(x)TMO_(2)and then profoundly revealed the electrochemical reaction processes.In this review,we begin with the descriptions of synchrotron characterization techniques and then present the advantages of synchrotron X-ray diffraction(XRD)over conventional XRD in detail.The optimizations of structural stability and electrochemical properties for P2-,O3-,and P2/O3-type Na_(x)TMO_(2)cathodes through single/dual-site substitution,high-entropy design,phase composition regulation,and surface engineering are summarized.The dynamic crystal structure evolutions of Na_(x)TMO_(2)polytypes during Na ion extraction/intercalation as well as corresponding structural enhancement mechanisms characterizing by means of HEXRD are concluded.The interior relationships between structure/component of Na_(x)TMO_(2)polytypes and their electrochemical properties are discussed.Finally,we look forward the research directions and issues in the route to improve the electrochemical properties of Na_(x)TMO_(2)cathodes for SIBs in the future and the combined utilizations of multiple characterization techniques.This review will provide significant guidelines for rational designs of high-performance Na_(x)TMO_(2)cathodes.展开更多
基金supported by the National Key R&D Program of China(No.2022YFB2404400)the National Natural Science Foundation of China(Nos.U23A20577,52372168,92263206 and 21975006)+1 种基金the“The Youth Beijing Scholars program”(No.PXM2021_014204_000023)the Beijing Natural Science Foundation(Nos.2222001 and KM202110005009).
文摘The cobalt-free Mn-based Li-rich layered oxide material has the advantages of low cost,high energy density,and good performance at low temperatures,and is the promising choice for energy storage batteries.However,the long-cycling stability of batteries needs to be improved.Herein,the Mn-based Li-rich cathode materials with small amounts of Li2 MnO3 crystal domains and gradient doping of Al and Ti elements from the surface to the bulk have been developed to improve the structure and interface stability.Then the batteries with a high energy density of 600 Wh kg^(-1),excellent capacity retention of 99.7%with low voltage decay of 0.03 mV cycle^(-1) after 800 cycles,and good rates performances can be achieved.Therefore,the structure and cycling stability of low voltage Mn-based Li-rich cathode materials can be significantly improved by the bulk structure design and interface regulation,and this work has paved the way for developing low-cost and high-energy Mn-based energy storage batteries with long lifetime.
基金supported by the National Natural Science Foundation of China(No.21805018)by Sichuan Science and Technology Program(Nos.2022ZHCG0018,2023NSFSC0117 and 2023ZHCG0060)Yibin Science and Technology Program(No.2022JB005)and China Postdoctoral Science Foundation(No.2022M722704).
文摘Layered transition metal oxides have emerged as promising cathode materials for sodium ion batteries.However,irreversible phase transitions cause structural distortion and cation rearrangement,leading to sluggish Na+dynamics and rapid capacity decay.In this study,we propose a medium-entropy cathode by simultaneously introducing Fe,Mg,and Li dopants into a typical P2-type Na_(0.75)Ni_(0.25)Mn_(0.75)O_(2)cathode.The modified Na_(0.75)Ni_(0.2125)Mn_(0.6375)Fe_(0.05)Mg_(0.05)Li_(0.05)O_(2)cathode predominantly exhibits a main P2 phase(93.5%)with a minor O3 phase(6.5%).Through spectroscopy techniques and electrochemical investigations,we elucidate the redox mechanisms of Ni^(2+/3+/4+),Mn^(3+/4+),Fe^(3+/4+),and O_(2)-/O_(2)^(n-)during charging/discharging.The medium-entropy doping mitigates the detrimental P2-O_(2)phase transition at high-voltage,replacing it with a moderate and reversible structural evolution(P2-OP4),thereby enhancing structural stability.Consequently,the modified cathode exhibits a remarkable rate capacity of 108.4 mAh·g^(-1)at 10C,with a capacity retention of 99.0%after 200 cycles at 1C,82.5%after 500 cycles at 5C,and 76.7%after 600 cycles at 10C.Furthermore,it also demonstrates superior electrochemical performance at high cutoff voltage of 4.5 V and extreme temperature(55 and 0℃).This work offers solutions to critical challenges in sodium ion batteries cathode materials.
基金supported by the Science and technology plan project of Yulin(2023-CXY-193)the Project funded by Shaanxi Postdoctoral Science Foundation(2023BSHEDZZ274)+2 种基金the Shaanxi Province(2023-ZDLGY-24,2023-JC-QN-0588,Z20210201)the Science and technology plan project of Beilin(GX2319)the Science and technology plan project of Ankang(AK2023-GY-08)。
文摘03-type layered oxide serves as dominant components in sodium ion batteries;however,the unstable electronic structure between transition metal and oxygen inevitably induces framework instability and severe kinetic hindrance.In this study,a two-in-one approach to synergistically modulate the local electro nic and interfacial structure of NaNi_(1/3)Fe_(1/3)Mn_(1/3)O_(2)by Ce modification is proposed.We present an indepth study to reveal the strong-covalent Ce-O bonds,which make local charge around oxygen more negative,enhance O 2p-Mn 3d hybridization,and preserve the octahedral structural integrity.This modification tailors local electronic structure between the octahedral metal center and oxygen,thus enhancing reversibility of 03-P3-03 phase transition and expanding Na+octahedral-tetrahedral-octahedral transport channel.Additionally,the nanoscale perovskite layer induced by Ce element is in favor of minimizing interfacial side reaction as well as enhancing Na^(+)diffusivity.As a result,the designed 03-NaNi_(0.305)Fe_(0.33)Mn_(0.33)Ce_(0.025)O_(2)material delivers an exceptionally low volume variation,an ultrahigh rate capacity of 76.9 mA h g^(-1)at 10 C,and remarkable cycling life over 250 cycles with capacity retention of 80% at 5 C.
基金supported by the National Natural Science Foundation of China (22169002)the Chongzuo Key Research and Development Program of China (20220603)the Counterpart Aid Project for Discipline Construction from Guangxi University(2023M02)
文摘P2/O3-type Ni/Mn-based layered oxides are promising cathode materials for sodium-ion batteries(SIBs)owing to their high energy density.However,exploring effective ways to enhance the synergy between the P2 and 03 phases remains a necessity.Herein,we design a P2/O3-type Na_(0.76)Ni_(0.31)Zn_(0.07)Mn_(0.50)Ti_(0.12)0_(2)(NNZMT)with high chemical/electrochemical stability by enhancing the coupling between the two phases.For the first time,a unique Na*extraction is observed from a Na-rich O3 phase by a Na-poor P2 phase and systematically investigated.This process is facilitated by Zn^(2+)/Ti^(4+)dual doping and calcination condition regulation,allowing a higher Na*content in the P2 phase with larger Na^(+)transport channels and enhancing Na transport kinetics.Because of reduced Na^(+)in the O3 phase,which increases the difficulty of H^(+)/Na^(+) exchange,the hydrostability of the O3 phase in NNZMT is considerably improved.Furthermore,Zn^(2+)/Ti^(4+)presence in NNZMT synergistically regulates oxygen redox chemistry,which effectively suppresses O_(2)/CO_(2) gas release and electrolyte decomposition,and completely inhibits phase transitions above 4.0 V.As a result,NNZMT achieves a high discharge capacity of 144.8 mA h g^(-1) with a median voltage of 3.42 V at 20 mA g^(-1) and exhibits excellent cycling performance with a capacity retention of 77.3% for 1000 cycles at 2000 mA g^(-1).This study provides an effective strategy and new insights into the design of high-performance layered-oxide cathode materials with enhanced structure/interface stability forSIBs.
基金supported by the program“Excellence Initiative-Research University”for the AGH University of Krakow(IDUB AGH,No.501.696.7996,Action 4,ID 6354)partially supported by the AGH University of Krakow under No.16.16.210.476.
文摘Undoubtedly,the enormous progress observed in recent years in the Ni-rich layered cathode materials has been crucial in terms of pushing boundaries of the Li-ion battery(LIB)technology.The achieved improvements in the energy density,cyclability,charging speed,reduced costs,as well as safety and stability,already contribute to the wider adoption of LIBs,which extends nowadays beyond mobile electronics,power tools,and electric vehicles,to the new range of applications,including grid storage solutions.With numerous published papers and broad reviews already available on the subject of Ni-rich oxides,this review focuses more on the most recent progress and new ideas presented in the literature references.The covered topics include doping and composition optimization,advanced coating,concentration gradient and single crystal materials,as well as innovations concerning new electrolytes and their modification,with the application of Ni-rich cathodes in solid-state batteries also discussed.Related cathode materials are briefly mentioned,with the high-entropy approach and zero-strain concept presented as well.A critical overview of the still unresolved issues is given,with perspectives on the further directions of studies and the expected gains provided.
基金financially supported by the Beijing Natural Science Foundation(JQ19003)National Key R&D Program of China(grant no.2018YFB0104300)+4 种基金National Natural Science Foundation of China(grant no 51622202,21603009,and 21875007)Beijing Natural Science Foundation(B)(KZ201910005002)Beijing Natural Science Foundation(L182009)Project of Youth Talent Plan of Beijing Municipal Education Commission(CIT&TCD201804013)High-grade discipline construction of Beijing(PXM2019-014204-500031)。
文摘The voltage decay of lithium-rich layered oxides(LLOs)is still one of the key challenges for their application in commercial battery although these materials possess the advantages of high specific capacity and low cost.In this work,the relationship between voltage decay and tap density of LLOs has been focused.The voltage decay can be significantly suppressed with the increasing tap density as well as the homogenization of the primary or secondary particle size of agglomerated spherical LLOs.Experimental results have shown that an extreme small voltage decay of 0.98 m V cycle^(-1)can be obtained through adjusting the tap density of agglomerated spherical LLOs to 1.99 g cm^(-3),in which the size of primary and secondary particles are uniform.Our work offers a new insight towards the voltage decay and capacity fading of LLOs through precursor preparation process,promoting their application in the real battery in the future.
基金the financial support from National Key Research & Development Program of China (2017B0602702)。
文摘In this paper, the superhydrophobic polyurethane sponge(SS-PU) was facilely fabricated by etching with Jones reagent to bind the nanoparticles of Ni-Co double layered oxides(LDOs) on the surface, and following modification with n-dodecyl mercaptan(DDT). This method provides a new strategy to fabricate superhydrophobic PU sponge with a water contact angle of 157° for absorbing oil with low cost and in large scale. It exhibits the strong absorption capacity and highly selective characteristic for various kinds of oils which can be recycled by simple squeezing. Besides, the as-prepared sponge can deal with the floating and underwater oils, indicating its application value in handling oil spills and domestic oily wastewater. The good self-cleaning ability shows the potential to clear the pollutants due to the ultralow adhesion to water. Especially, the most important point is that the superhydrophobic sponge can continuously and effectively separate the oil/water mixture against the condition of turbulent disturbance by using our designed device system, which exhibit its good superhydrophobicity, strong stability.Furthermore, the SS-PU still maintained stable absorption performance after 150 cycle tests without losing capacity obviously, showing excellent durability in long-term operation and significant potential as an efficient absorbent in large-scale dispose of oily water.
基金supported by the Guangdong Provincial Science and Technology Commission,Guangdong Key Areas R&D Program(2020B0909030004)the Beijing Natural Science Foundation Committee,Haidian Original Innovation Joint Fund Project(L182023)Youth Fund Project of GRINM(Grant No.12620203129011).
文摘Lithium-rich layered oxides(LLOs)are promising candidate cathode materials for safe and inexpensive high-energy-density Li-ion batteries.However,oxygen dimers are formed from the cathode material through oxygen redox activity,which can result in morphological changes and structural transitions that cause performance deterioration and safety concerns.Herein,a flake-like LLO is prepared and aberration-corrected scanning transmission electron microscopy(STEM),in situ high-temperature X-ray diffraction(HT-XRD),and soft X-ray absorption spectrum(sXAS)are used to explore its crystal facet degradation behavior in terms of both thermal and electrochemical processes.Void-induced degradation behavior of LLO in different facet reveals significant anisotropy at high voltage.Particle degradation originates from side facets,such as the(010)facet,while the close(003)facet is stable.These results are further understood through ab initio molecular dynamics calculations,which show that oxygen atoms are lost from the{010}facets.Therefore,the facet degradation process is that oxygen molecular formed in the interlayer and accumulated in the ab plane during heating,which result in crevice-voids in the ab plane facets.The study reveals important aspects of the mechanism responsible for oxygen-anionic activity-based degradation of LLO cathode materials used in lithium-ion batteries.In particular,this study provides insight that enables precise and efficient measures to be taken to improve the thermal and electrochemical stability of an LLO.
基金supported by the Fundamental Research Funds for the Central Universities(FRF-TP-18-091A1)。
文摘Sodium-ion batteries are very promising in large-scale energy storage.The exploration of Na layered oxides as cathode materials for Na ion batteries usually consumes much resource,while the performances of Na layered oxides are dominated by their crystal structures.Therefore,it is highly desired to predict the stacking mode of the target oxides in advance:whether O3-type with higher ordered structure and stability,or P2-type with more Na content.For this purpose density functional theory computations do not work.Very recently,Hu's group and international collaborators have proposed a cationic potential to provide a very timely,effective,and accurate criterion to predict the stacking mode of Na layered oxides(Science,370(2020)708-711).Under the guidance of the cationic potential phase map,Na layered oxides could be rationally designed.Here we would like to highlight the progress that novel Na layered oxides could be obtained with the combination of large specific capacity,high power density and good cycling stability.
基金supported by the National Natural Science Foundation of China(52272253)the"Lingyan"Research and Development Plan of Zhejiang Province(2022C01071)+2 种基金the S&T Innovation 2025 Major Special Programme of Ningbo(2018B10081)the Natural Science Foundation of Ningbo(202003N4030)the Youth Innovation Promotion Association of Chinese Academy of Sciences(2022299)。
文摘Though oxygen defects are associated with deteriorated structures and aggravated cycling performance in traditional layered cathodes,the role of oxygen defects is still ambiguous in Li-rich layered oxides due to the involvement of oxygen redox.Herein,a Co-free Li-rich layered oxide Li_(1.286)Ni_(0.071)Mn_(0.643)O_(2)has been prepared by a co-precipitation method to systematically investigate the undefined effects of the oxygen defects.A significant O_(2)release and the propagation of oxygen vacancies were detected by operando differential electrochemical mass spectroscopy(DEMS)and electron energy loss spectroscopy(EELS),respectively.Scanning transmission electron microscopy-high angle annular dark field(STEMHAADF)reveals the oxygen vacancies fusing to nanovoids and monitors a stepwise electrochemical activation process of the large Li_(2)MnO_(3)domain upon cycling.Combined with the quantitative analysis conducted by the energy dispersive spectrometer(EDS),existed nano-scale oxygen defects actually expose more surface to the electrolyte for facilitating the electrochemical activation and subsequently increasing available capacity.Overall,this work persuasively elucidates the function of oxygen defects on oxygen redox in Co-free Li-rich layered oxides.
基金Financial supports from the National Natural Science Foundation of China (21822506 and 51761165025)the Tianjin Natural Science Foundation (19JCJQJC62400)the 111 project of B12015。
文摘Anionic redox reaction(ARR) in layered manganese-based oxide cathodes has been considered as an effective strategy to improve the energy density of sodium-ion batteries.Mn-vacancy layered oxides deliver a high ARR-related capacity with small voltage hysteresis,however,they are limited by rapid capacity degradation and poor rate capability,which arise from inferior structure changes due to repeated redox of lattice oxygen.Herein,redox-inactive Ti^(4+)is introduced to substitute partial Mn^(4+)to form Na_(2) Ti_(0.5)Mn_(2.5)O_7(Na_(4/7)[□_(1/7)Ti_(1/7)Mn_(5/7)]O_(2),□ for Mn vacancies),which can effectively restrain unfavorable interlayer gliding of Na2 Mn307 at high charge voltages,as reflected by an ultralow-strain volume variation of 0.11%.There is no irreversible O_(2) evolution observed in Na_(2) Ti_(0.5)Mn_(2.5)O_7 upon charging,which stabilizes the lattice oxygen and ensures the overall structural stability.It exhibits increased capacity retention of 79.1% after 60 cycles in Na_(2) Ti_(0.5)Mn_(2.5)O_7(17.1% in Na_(2) Mn_(3) O_7) and good rate capability(92.1 mAh g^(-1) at 0.5 A g^(-1)).This investigation provides new insights into designing high-performance cathode materials with reversible ARR and structural stability for SIBs.
基金finically supported by the National Key Research and Development Program of China (Grant No. 2016YFB0100100)Strategic Priority Research Program of Chinese Academy of Sciences (CAS, Grant No. XDA09010101)Ningbo Key Science and Technology Projects "Industrial Application Development of Graphene" (Grant No. 2014S10008)
文摘Lithium-rich layered oxides(LrLOs) deliver extremely high specific capacities and are considered to be promising candidates for electric vehicle and smart grid applications. However, the application of LrLOs needs further understanding of the structural complexity and dynamic evolution of monoclinic and rhombohedral phases, in order to overcome the issues including voltage decay, poor rate capability, initial irreversible capacity loss and etc. The development of aberration correction for the transmission electron microscope and concurrent progress in electron spectroscopy, have fueled rapid progress in the understanding of the mechanism of such issues. New techniques based on the transmission electron microscope are first surveyed, and the applications of these techniques for the study of the structure, migration of transition metal, and the activation of oxygen of LrLOs are then explored in detail, with a particular focus on the mechanism of voltage decay.
基金Ministry of SMEs and Startups,Grant/Award Number:S3248116National Research Foundation of Korea,Grant/Award Numbers:RS-2023-00211636,RS-2024-00416891Ministry of Science and ICT,South Korea,Grant/Award Number:RS-2020-II201336。
文摘Nickel-rich layered oxides(LiNixCoyMnzO2,NCM)are among the most promising cathode materials for high-energy lithium-ion batteries,offering high specific capacity and output voltage at a relatively low cost.However,industrialscale co-precipitation presents significant challenges,particularly in maintaining particle sphericity,ensuring a stable concentration gradient,and preserving production yield when transitioning from lab-scale compositions.This study addresses a critical issue in the large-scale synthesis of nickel-rich NCM(x=0.8381):nickel leaching,which compromises particle uniformity and battery performance.To mitigate this,we optimize the reaction process and develop an artificial intelligence-driven defect prediction system that enhances precursor stability.Our domain adaptation based machine learning model,which accounts for equipment wear and environmental variations,achieves a defect detection accuracy of 97.8%based on machine data and process conditions.By implementing this approach,we successfully scale up NCM precursor production to over 2 tons,achieving 83%capacity retention after 500 cycles at a 1C rate.In addition,the proposed approach demonstrates the formation of a concentration gradient in the composition and a high sphericity of 0.951(±0.0796).This work provides new insights into the stable mass production of NCM precursors,ensuring both high yield and performance reliability.
基金supported by the National Natural Science Foundation of China(92372107,52304338,and 52171219)。
文摘The development of sustainable energy storage solutions has driven research toward alternatives to lithiumion batteries.Sodium-ion battery(SIB)was considered a promising candidate due to their cost-effectiveness and sodium abundance.To introduce defects and enhance the electrochemical performance of O_(3)-phase sodium-ion layered oxide materials,high-temperature shock(HTS)was employed.However,given the characteristics of HTS,especially the rapid heating rate and short sintering time,suitable precursor systems need to be explored.We systematically compared three precursor systems:traditional metal oxides(HTS-O),decomposable salts(HTS-D),and a novel pre-reacted precursor system(HTS-S).The pre-reacted precursor,developed by leveraging the ethanol solubility of C_(4)H_(14)MnO_(8) and modified ball milling conditions,enabled rapid O_(3) phase formation and resulted in impurity-free O_(3)-NaCu_(0.2)Fe_(0.3)Mn _(0.5)O_(2).This material demonstrated superior electrochemical performance,achieving a discharge capacity of 144.05 mAh g^(−1) within 2.0-4.1 V,along with enhanced rate capabilities.Our findings underscore the critical role of precursor selection and modification in HTS synthesis,contributing to the advancement of high-performance sodium-ion battery materials.
基金National Natural Science Foundation of China,Grant/Award Numbers:22179008,21875022Yibin“Jie Bang Gua Shuai”,Grant/Award Number:2022JB004+2 种基金Beijing Nova Program,Grant/Award Number:20230484241Postdoctoral Fellowship Program of CPSF,Grant/Award Number:GZB20230931Special Support of Chongqing Postdoctoral Research Project,Grant/Award Number:2023CQBSHTB2041。
文摘The burgeoning growth in electric vehicles and portable energy storage systems necessitates advances in the energy density and cost-effectiveness of lithium-ion batteries(LIBs),areas where lithium-rich manganese-based oxide(LLO)materials naturally stand out.Despite their inherent advantages,these materials encounter significant practical hurdles,including low initial Coulombic efficiency(ICE),diminished cycle/rate performance,and voltage fading during cycling,hindering their widespread adoption.In response,we introduce an ionic-electronic dual-conductive(IEDC)surface control strategy that integrates an electronically conductive graphene framework with an ionically conductive heteroepitaxial spinel Li_(4)Mn_(5)O_(12)layer.Prolonged electrochemical and structural analyses demonstrate that this IEDC heterostructure effectively minimizes polarization,mitigates structural distortion,and enhances electronic/ionic diffusion.Density functional theory calculations highlight an extensive Li^(+)percolation network and lower Li^(+)migration energies at the layered-spinel interface.The designed LLO cathode with IEDC interface engineering(LMOSG)exhibits improved ICE(82.9%at 0.1 C),elevated initial discharge capacity(296.7 mAh g^(-1)at 0.1 C),exceptional rate capability(176.5 mAh g^(-1)at 5 C),and outstanding cycle stability(73.7%retention at 5 C after 500 cycles).These findings and the novel dual-conductive surface architecture design offer promising directions for advancing highperformance electrode materials.
基金financially supported by the National Natural Science Foundation of China(Grant No.52272253)“Lingyan”Research and Development Plan of Zhejiang Province(Grant No.2022C01071)+2 种基金Low Cost Cathode Material(Grant No.TC220H06P)the Natural Science Foundation of Ningbo(Grant No.202003N4030)the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.2022299)
文摘The undesirable capacity loss after first cycle is universal among layered cathode materials,which results in the capacity and energy decay.The key to resolving this obstacle lies in understanding the effect and origin of specific active Li sites during discharge process.In this study,focusing on Ah-level pouch cells for reliability,an ultrahigh initial Coulombic efficiency(96.1%)is achieved in an archetypical Li-rich layered oxide material.Combining the structure and electrochemistry analysis,we demonstrate that the achievement of high-capacity reversibility is a kinetic effect,primarily related to the sluggish Li mobility during oxygen reduction.Activating oxygen reduction through small density would induce the oxygen framework contraction,which,according to Pauli repulsion,imposes a great repulsive force to hinder the transport of tetrahedral Li.The tetrahedral Li storage upon deep oxygen reduction is experimentally visualized and,more importantly,contributes to 6%Coulombic efficiency enhancement as well as 10%energy density improvement for pouch cells,which shows great potentials breaking through the capacity and energy limitation imposed by intercalation chemistry.
基金financially supported by the National Natural Science Foundation of China(No.52202228,52402298)funded by the Science Research Project of Hebei Education Department(No.BJK2022011)+3 种基金the Central Funds Guiding the Local Science and Technology Development of Hebei Province(No.236Z4404G)the Beijing Tianjin Hebei Basic Research Cooperation Special Project(No.E2024202273)the Science and Technology Correspondent Project of Tianjin(24YDTPJC00240)supported by the U.S.Department of Energy’s Office of Science,Office of Basic Energy Science,Materials Sciences and Engineering Division。
文摘Nickel-rich(Ni≥90%)layered oxides materials have emerged as a promising candidate for nextgeneration high-energy-density lithium-ion batteries(LIBs).However,their widespread application is hindered by structural fatigue and lattice oxygen loss.In this work,an epitaxial surface rock-salt nanolayer is successfully developed on the LiNi_(0.9)Co_(0.1)O_(2)sub-surface via heteroatom anchoring utilizing high-valence element molybdenum modification.This in-situ formed conformal buffer phase with a thickness of 1.2 nm effectively suppresses the continuous interphase side-reactions,and thus maintains the excellent structure integrity at high voltage.Furthermore,theoretical calculations indicate that the lattice oxygen reversibility in the anion framework of the optimized sample is obviously enhanced due to the higher content of O 2p states near the Fermi level than that of the pristine one.Meanwhile,the stronger Mo-O bond further reduces cell volume alteration,which improves the bulk structure stability of modified materials.Besides,the detailed charge compensation mechanism suggests that the average oxidation state of Ni is reduced,which induces more active Li+participating in the redox reactions,boosting the cell energy density.As a result,the uniquely designed cathode materials exhibit an extraordinary discharge capacity of 245.4 mAh g^(-1)at 0.1 C,remarkable rate performance of 169.3 mAh g^(-1)at 10 C at 4.5 V,and a high capacity retention of 70.5% after 1000 cycles in full cells at a high cut-off voltage of 4.4 V.This strategy provides an valuable insight into constructing distinctive heterostructure on highperformance Ni-rich layered cathodes for LIBs.
基金support from the Natural Science Foundation of Jiangsu Province(BK20230376)National Natural Science Foundation of China(22309085 and 52072181)Jiangsu Provincial Department of Education(23KJB150019).
文摘CONSPECTUS:Li-rich layered oxides have received extensive attention as promising high-energy-density cathodes for next-generation Li-ion batteries.Different from traditional cathodes such as LiCoO2,LiFePO4,and Li2MnO4,Li-rich oxides generally can harvest superior discharge capacities exceeding 250 mAh g−1,which originated from the contribution of oxygen redox chemistry.However,lattice oxygen release and irreversible TM transition would induce severe structure distortion and capacity degradation as well as voltage attenuation within Li-rich cathodes during electrochemical processes,which greatly limits their industrial applications in next-generation Li-ion batteries.
基金Korea Institute of Science and Technology,Grant/Award Number:2E33270National Research Foundation of Korea,Grant/Award Number:2020M3H4A3081889。
文摘Sodium-ion batteries(SIBs)employ P2-type layered transition metal oxides as promising cathode materials,primarily due to their abundant natural reserves and environmentally friendly characteristics.However,structural instability and complex phase transitions during electrochemical cycling pose significant challenges to their practical applications.Employing cation substitution serves as a straightforward yet effective strategy for stabilizing the structure and improving the kinetics of the active material.In this study,we introduce a Ni-rich honeycomb-layered Na_(2+x)Ni_(2)TeO_(6)(NNTO)cathode material with variable sodium content(x=0,0.03,0.05,0.10).Physicochemical characterizations reveal that excess sodium content at the atomic scale modifies the surface and suppresses phase transitions,while preserving the crystal structure.This results in enhanced cyclic performance and improved electrochemical kinetics at room temperature.Furthermore,we investigate the performance of the NNTO cathode material containing 10%excess sodium at a relatively high temperature of 60℃,where it exhibits 71.6%capacity retention compared to 60%for the pristine.Overall,our results confirm that a preconstructed surface layer(induced by excess sodium)effectively safeguards the Ni-based cathode material from surface degradation and phase transitions during the electrochemical processes,thus exhibiting superior capacity retention relative to the pristine NNTO cathode.This study of the correlation between structure and performance can potentially be applied to the commercialization of SIBs.
基金supported by the State Grid Corporation Science and Technology Project(No.5419-202158503A-0-5-ZN)。
文摘The detrimental phase transformations of sodium layered transition metal oxides(Na_(x)TMO_(2))during desodiation/sodiation seriously suppress their practical applications for sodium ion batteries(SIBs).Undoubtedly,comprehensively investigating of the dynamic crystal structure evolutions of Na_(x)TMO_(2)associating with Na ions extraction/intercalation and then deeply understanding of the relationships between electrochemical performances and phase structures drawing support from advanced characterization techniques are indispensable.In-situ high-energy X-ray diffraction(HEXRD),a powerful technology to distinguish the crystal structure of electrode materials,has been widely used to identify the phase evolutions of Na_(x)TMO_(2)and then profoundly revealed the electrochemical reaction processes.In this review,we begin with the descriptions of synchrotron characterization techniques and then present the advantages of synchrotron X-ray diffraction(XRD)over conventional XRD in detail.The optimizations of structural stability and electrochemical properties for P2-,O3-,and P2/O3-type Na_(x)TMO_(2)cathodes through single/dual-site substitution,high-entropy design,phase composition regulation,and surface engineering are summarized.The dynamic crystal structure evolutions of Na_(x)TMO_(2)polytypes during Na ion extraction/intercalation as well as corresponding structural enhancement mechanisms characterizing by means of HEXRD are concluded.The interior relationships between structure/component of Na_(x)TMO_(2)polytypes and their electrochemical properties are discussed.Finally,we look forward the research directions and issues in the route to improve the electrochemical properties of Na_(x)TMO_(2)cathodes for SIBs in the future and the combined utilizations of multiple characterization techniques.This review will provide significant guidelines for rational designs of high-performance Na_(x)TMO_(2)cathodes.
