Co-free Li-rich layered oxides(LLOs)are emerging as promising cathode materials for Li-ion batteries due to their low cost and high capacity.However,they commonly face severe structural instability and poor electroche...Co-free Li-rich layered oxides(LLOs)are emerging as promising cathode materials for Li-ion batteries due to their low cost and high capacity.However,they commonly face severe structural instability and poor electrochemical activity,leading to diminished capacity and voltage performance.Herein,we introduce a Co-free LLO,Li_(1.167)Ni_(0.222)Mn_(0.611)O_(2)(Cf-L1),which features a cooperative structure of Li/Ni mixing and stacking faults.This structure regulates the crystal and electronic structures,resulting in a higher discharge capacity of 300.6 mA h g^(-1)and enhanced rate capability compared to the typical Co-free LLO,Li_(1.2)Ni_(0.2)Mn_(0.6)O_(2)(Cf-Ls).Density functional theory(DFT)indicates that Li/Ni mixing in LLOs leads to increased Li-O-Li configurations and higher anionic redox activities,while stacking faults further optimize the electronic interactions of transition metal(TM)3d and non-bonding O 2p orbitals.Moreover,stacking faults accommodate lattice strain,improving electrochemical reversibility during charge/discharge cycles,as demonstrated by the in situ XRD of Cf-L1 showing less lattice evolution than Cf-Ls.This study offers a structured approach to developing Co-free LLOs with enhanced capacity,voltage,rate capability,and cyclability,significantly impacting the advancement of the next-generation Li-ion batteries.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
The structural transformations,oxygen releasing and side reactions with electrolytes on the surface are considered as the main causes of the performance degradation of Li-rich layered oxides(LROs)cathodes in Li-ion ba...The structural transformations,oxygen releasing and side reactions with electrolytes on the surface are considered as the main causes of the performance degradation of Li-rich layered oxides(LROs)cathodes in Li-ion batteries.Thus,stabilizing the surfaces of LROs is the key to realize their practical application in high energy density Li-ion batteries.Surface coating is regarded as one of the most effective strategies for high voltage cathodes.The ideal coating materials should prevent cathodes from electrolyte corrosion and possess both electronic and Li-ionic conductivities simultaneously.However,commonly reported coating materials are unable to balance these functions well.Herein,a new type of coating material,La_(2)CuO_(4)was introduced to mitigate the surface issues of LROs for the first time,due to its superb electronic conductivity(26-35 mS·cm^(-1))and lithium-ionic diffusion coefficient(10^(-12)-10^(-13)cm^(2)·s^(-1)).After coating with the La_(2)CuO_(4),the capacity retention of Li_(1.2)Ni_(0.54)Co_(0.13)Mn_(0.13)O_(2)cathode was increased to 85.9%(compared to 79.3%of uncoated cathode)after 150 cycles in the voltage range of 2.0-4.8 V.In addition,only negligible degradations on the deliverable capacity and rate capability were observed.展开更多
The high-rate cyclability of Li-rich Mn-based oxide(LMO)is highly limited by the electrochemical polarization resulting from the slow kinetic of the Li2MnO3 phase.Herein,the Prussian blue(PB)coating layer with specifi...The high-rate cyclability of Li-rich Mn-based oxide(LMO)is highly limited by the electrochemical polarization resulting from the slow kinetic of the Li2MnO3 phase.Herein,the Prussian blue(PB)coating layer with specific redox potential is introduced as a functionalized interface to overcome the side effect and the escaping of O on the surface of LMO,especially its poor rate capability.In detail,the PB layer can restrict the large polarization of LMO by sharing overloaded current at a high rate due to the synchronous redox of PB and LMO.Consequently,an enhanced high rate performance with capacity retention of 87.8%over 300 cycles is obtained,which is superior to 50.5%of the pristine electrode.Such strategies on the high-rate cyclability of Li-rich Mn-based oxide compatible with good low-rate performances may attract great attention for pursuing durable performances.展开更多
Li-rich layered oxides have become one of the most concerned cathode materials for high-energy lithiumion batteries, but they still suffer from poor cycling stability and detrimental voltage decay, especially at eleva...Li-rich layered oxides have become one of the most concerned cathode materials for high-energy lithiumion batteries, but they still suffer from poor cycling stability and detrimental voltage decay, especially at elevated temperature. Herein, we proposed a surface heterophase coating engineering based on amorphous/crystalline Li3 PO4 to address these issues for Li-rich layered oxides via a facile wet chemical method. The heterophase coating layer combines the advantages of physical barrier effect achieved by amorphous Li3 PO4 with facilitated Li+diffusion stemmed from crystalline Li3 PO4. Consequently, the modified Li(1.2) Ni(0.2) Mn(0.6) O2 delivers higher initial coulombic efficiency of 92% with enhanced cycling stability at 55 °C(192.9 mAh/g after 100 cycles at 1 C). More importantly, the intrinsic voltage decay has been inhibited as well, i.e. the average potential drop per cycle decreases from 5.96 mV to 2.99 mV. This surface heterophase coating engineering provides an effective strategy to enhance the high-temperature electrochemical performances of Li-rich layered oxides and guides the direction of surface modification strategies for cathode materials in the future.展开更多
Li-rich layered oxide cathodes have received considerable attention because of the high operating potential and specific capacity. However, the structural instability and parasitic reactions at high potential cause se...Li-rich layered oxide cathodes have received considerable attention because of the high operating potential and specific capacity. However, the structural instability and parasitic reactions at high potential cause severe degradation of the electrochemical performance. In our studies, the cycling stability of Li_(1.14)Ni_(0.133)Co_(0.133)Mn_(0.544)O_(2) cathode is improved with LiPO_(2)F_(2) electrolyte additive. After 500 cycles, the capacity retention is increased from 53.6% to 85% at 3 C by LiPO_(2)F_(2) modification. This performance is mainly attributed to the enhanced interfacial stability of the Li-rich cathode. Based on systematic characterization, LiPO_(2)F_(2) additive was found to promote a stable interface film on the cathode surface during the cycling and mitigates the interfacial side reactions. This study provides new insights for improving high-potential Li-rich layered oxide batteries.展开更多
For constructing next-generation lithium-ion batteries with advanced performances,pursuit of highcapacity Li-rich cathodes has caused considerable attention.So far,the low discharge specific capacity and serious capac...For constructing next-generation lithium-ion batteries with advanced performances,pursuit of highcapacity Li-rich cathodes has caused considerable attention.So far,the low discharge specific capacity and serious capacity fading are strangling the development of Fe-based Li-rich materials.To activate the extra-capacity of Fe-based Li-rich cathode materials,a facile molten salt method is exploited using an alkaline mixture of LiOH–LiNO3–Li2O2 in this work.The prepared Li1.09(Fe0.2Ni0.3Mn0.5)0.91O2 material yields high discharge specific capacity and good cycling stability.The discharge specific capacity shows an upward tendency at 0.1 C.After 60 cycles,a high reversible specific capacity of ~250 m Ah g-1is delivered.The redox of Fe3+/Fe4+and Mn3+/Mn4+are gradually activated during cycling.Notably,the redox reaction of Fe2+/Fe3+can be observed reversibly below 2 V,which is quite different from the material prepared by a traditional co-precipitation method.The stable morphology of fine nanoparticles(100–300 nm)is considered benefiting for the distinctive electrochemical performances of Li1.09(Fe0.2Ni0.3Mn0.5)0.91O2.This study demonstrates that molten salt method is an inexpensive and effective approach to activate the extra capacity of Fe-based Li-rich cathode material for high-performance lithium-ion batteries.展开更多
Li-rich layered oxide of Li_(1.2)Mn_(0.6)Ni_(0.2)O_(2)(LMNO)with a considerable specific capacity and higher voltage is regarded as a kind of promising cathode material.However,it suffers from transition metal ion dis...Li-rich layered oxide of Li_(1.2)Mn_(0.6)Ni_(0.2)O_(2)(LMNO)with a considerable specific capacity and higher voltage is regarded as a kind of promising cathode material.However,it suffers from transition metal ion dissolution and oxygen escape that leads to rapid capacity decay.In addition,the poor lithium-ion diffusion kinetics gives rise to unsatisfied rate performance.Herein,a stable layer of Li_(0.5)Mn_(0.5)O(LMO)out of LMNO is in-situ constructed through acetic passivation and following calcination process.The generated defect structure in the composite material exhibits fast ion diffusion kinetics and the produced LMO layer can stabilize the substructure,resulting in elevated cycling stability and rate performance.In specific,the LMNO@LMO material exhibits a high initial coulombic efficiency of 80.3%and remarkable capacity retention of 80.7%after 200 cycles at 1 C.Besides,the composite material reveals prominent rate performance that delivers discharge capacities of 158 and 131 m Ah g^(-1) at 5 and 10 C,respectively.At last,this study presents a new approach to optimizing the Li-rich cathode materials.展开更多
Traditional O3-type Li-rich layered materials are attractive with ultra-high specific capacities,but suffering from inherent problems of voltage hysteresis and poor cycle performance.As an alternative,O2-type material...Traditional O3-type Li-rich layered materials are attractive with ultra-high specific capacities,but suffering from inherent problems of voltage hysteresis and poor cycle performance.As an alternative,O2-type materials show the potential to improve the oxygen redox reversibility and structural stability.However,their structure-performance relationship is still unclear.Here,we investigate the correlation between the Li component and dynamic chemical reversibility of O2-type Li-rich materials.By exploring the formation mechanism of a series of materials prepared by Na/Li exchange,we reveal that insufficient Li leads to an incomplete replacement,and the residual Na in the Li-layer would hinder the fast diffusion of Li^(+).Moreover,excessive Li induces the extraction of interlayer Li during the melting chemical reaction stage,resulting in a reduction in the valence of Mn,which leads to a severe Jahn-Teller effect.Structural detection confirms that the regulation of Li can improve the cycle stability of Li-rich materials and suppress the trend of voltage fading.The reversible phase evolution observed in in-situ X-ray diffraction confirms the excellent structural stability of the optimized material,which is conducive to capacity retention.This work highlights the significance of modulating dynamic electrochemical performance through the intrinsic structure.展开更多
Li-rich layered transition metal oxides are one of the most promising cathode materials for their high energy density.However,the cathodes usually suffer from severe potential dropping and capacity fading during cycli...Li-rich layered transition metal oxides are one of the most promising cathode materials for their high energy density.However,the cathodes usually suffer from severe potential dropping and capacity fading during cycling,which are associated with the surface oxygen release and accompanied by cation densification and structural collapse.Herein,an integrative approach of simultaneous constructing uniform 3d Fe-ion doping in the transition metal layer and Li-rich Li_(5)FeO_(4) shell to grab the oxygen and prevent interfacial side reactions is proposed.The introduction of Fe induces higher redox potential and stronger 3 d Fe-O_(2)p covalent bond,triggering reversible anionic redox via a reductive coupling mechanism.And the delithiated product of Li-rich Li_(5)FeO_(4) not only acts as a protective layer alleviating the side reactions but also enhances the surface kinetic property.With the benefit of promoted reversibility of oxygen redox and enhanced surface stability,the cathode exhibits high reversible capacity and superior cycle performance.Density function theory calculation indicates that the O_(2)p non-bonding state in the cathode incorporated with Fe sits at a lower energy band,resulting in higher energy storage voltage and improved oxygen stability.Consequently,the modified cathode exhibits a discharge specific capacity of 307 m A h g^(-1)(1 C=250 m A g^(-1)),coulombic efficiency of 82.09%in the initial cycle at 0.1 C and 88.34%capacity retention after 100 cycles at 1 C.The work illustrates a strategy that could simultaneously enhance oxygen redox reversibility and interface stability by constructing lattice bond coordination and delithiation induced protective layer to develop Li-rich materials with high reversible capacity and long lifespan.展开更多
Co-free Li-rich layered oxide cathodes have drawn much attention owing to their low cost and high energy density.Nevertheless,anion oxidation of oxygen leads to oxygen peroxidation during the first charging process,wh...Co-free Li-rich layered oxide cathodes have drawn much attention owing to their low cost and high energy density.Nevertheless,anion oxidation of oxygen leads to oxygen peroxidation during the first charging process,which leads to co-migration of transition metal ions and oxygen vacancies,causing structural instability.In this work,we propose a pre-activation strategy driven by chemical impregnation to modulate the chemical state of surface lattice oxygen,thus regulating the structural and electrochemical properties of the cathodes.In-situ X-ray diffraction confirms that materials based on activated oxygen configuration have higher structural stability.More importantly,this novel efficient strategy endows the cathodes having a lower surface charge transfer barrier and higher Li+transfer kinetics characteristic and ameliorates its inherent issues.The optimized cathode exhibits excellent electrochemical performance:after 300 cycles,high capacity(from 238 m Ah g^(-1)to 193 m Ah g^(-1)at 1 C)and low voltage attenuation(168 mV)are obtained.Overall,this modulated surface lattice oxygen strategy improves the electrochemical activity and structural stability,providing an innovative idea to obtain high-capacity Co-free Li-rich cathodes for next-generation Li-ion batteries.展开更多
The Li-rich Zn-doped LiNbO 3 (LN) crystals were grown by the Czochralski method. The structure of the crystals was measured by ultraviolet-visible absorption spectra. The results indicated that the Li-rich Zn-doped LN...The Li-rich Zn-doped LiNbO 3 (LN) crystals were grown by the Czochralski method. The structure of the crystals was measured by ultraviolet-visible absorption spectra. The results indicated that the Li-rich Zn-doped LN crystals had the same characteristics as the pure LN crystal. After Zn 2+ entered into the lattice of Li-rich Zn-doped LN crystal, it replaced Nb Li firstly. When there was no Nb Li , Zn 2+ replaced Li + then. The second harmonic generation (SHG) property of Li-rich Zn-doped LiNbO 3 crystal was measured. The results showed that the SHG conversation efficiency of Li-rich Zn-doped LiNbO 3 crystals was higher than that of Zn-doped LiNbO 3 crystals.展开更多
Boosting the interfacial stability between electrolyte and Li-rich cathode material at high operating voltage is vital important to enhance the cycling stability of Li-rich cathode materials for high-performance Li-io...Boosting the interfacial stability between electrolyte and Li-rich cathode material at high operating voltage is vital important to enhance the cycling stability of Li-rich cathode materials for high-performance Li-ion batteries.In this work,vinyltrimethylsilane as a new type of organic silicon electrolyte additive is studied to address the interfacial instability of Li-rich cathode material at high operating voltage.The cells using vinyltrimethylsilane additive shows the high capacity retention of 73.9%after 300 cycles at 1 C,whereas the cells without this kind of additive only have the capacity retention of 58.9%.The improvement of stability is mainly attributed to the additive helping to form a more stable surface film for Li-rich cathode material,thus avoiding direct contact between the electrolyte and the cathode material,slowing down the dissolution of metal ions and the decomposition of the electrolyte under high operating voltage.Our findings in this work shed some light on the design of stable cycling performance of Li-rich cathode toward advanced Li-ion batteries.展开更多
The energy density of Li-ion batteries is closely related to the capacity and average voltage of cathode materials.Unfortunately,current cathode materials either have low capacity or voltage,which limits the developme...The energy density of Li-ion batteries is closely related to the capacity and average voltage of cathode materials.Unfortunately,current cathode materials either have low capacity or voltage,which limits the development of high-energy-density Li-ion batteries.This has given challenge to many attempts to develop new cathode materials with high capacity and voltage.In this study,we find that Li easily inserts into the(111)plane of SiC in the presence of Si,and a well-organized Li-rich SiC twin crystal is formed.Ultraviolet-visible diffuse reflectance spectra and electrochemical test results suggest that this Li-rich SiC twin crystal possesses the band gap energy of 3.5 eV and charging capacity of 1979 mAh/g at the current density of 200 mA/g,making it a promising candidate for the cathode material in high-capacity Li-ion batteries.X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy results reveal that Si-induced Li insertion contributes to the changes in the surface species and structure of pristine SiC.These findings suggest that the Li-rich SiC twin crystal raises new possibilities for the development of high-capacity cathode materials and merits further investigation to expand its application scope.展开更多
Co-free Li-rich Mn-based layered oxides are promising candidates for next-generation lithium-ion batteries(LIBs)due to their high specific capacity,high voltage,low cost.However,their commercialization is hindered by ...Co-free Li-rich Mn-based layered oxides are promising candidates for next-generation lithium-ion batteries(LIBs)due to their high specific capacity,high voltage,low cost.However,their commercialization is hindered by limited cycle life and poor rate performance.Herein,an in-situ simple and low-cost strategy with a nanoscale double-layer architecture of lithium polyphosphate(LiPP)and spinel phase covered on top of the bulk layered phase,is developed for Li_(1.2)Mn_(0.6)Ni_(0.2)O_(2)(LMNO)using Li^(+)-conductor LiPP(denoted as LMNO@S-LiPP).With such a double-layer covered architecture,the half-cell of LMNO@S-LiPP delivers an extremely high capacity of 202.5 mAh·g^(−1)at 1 A·g^(−1)and retains 85.3%of the initial capacity after 300 cycles,so far,the best highrate electrochemical performance of all the previously reported LMNOs.The energy density of the full-cell assembled with commercial graphite reaches 620.9 Wh·kg^(−1)(based on total weight of active materials in cathode and anode).Mechanism studies indicate that the superior electrochemical performance of LMNO@S-LiPP is originated from such a nanoscale double-layer covered architecture,which accelerates Li-ion diffusion,restrains oxygen release,inhibits interfacial side reactions,suppresses structural degradation during cycling.Moreover,this strategy is applicable for other high-energy-density cathodes,such as LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2),Li_(1.2)Ni_(0.13)Co_(0.13)Mn_(0.54)O_(2),LiCoO_(2).Hence,this work presents a simple,cost-effective,scalable strategy for the development of high-performance cathode materials.展开更多
As one of the promising candidate cathode materials for the high-performance lithium-ion batteries,Li-rich layered oxides still suffer from a series of critical drawbacks,such as voltage decay,oxygen release,irrevers-...As one of the promising candidate cathode materials for the high-performance lithium-ion batteries,Li-rich layered oxides still suffer from a series of critical drawbacks,such as voltage decay,oxygen release,irrevers-ible migration of transition metal ions,etc.In this work,Li-deficient method has been confirmed as an effective approach to improve the overall electrochemical performances of Li-rich cathode.The optimized lithium-deficient Li-rich layered cathode exhibits splendid discharge capacity of~297 mAh/g at 0.1 C and prominent rate per-formance of-143 mAh/g at 5 C.Subsequently,neutron diffraction in combination with Raman spectroscopy is applied to explore and clarify the underlying mechanism for improved performances.It was found that the lithium-deficient induced nickel migration and oxygen vacancy play an significant role in improving electro-chemical performances,because migration of nickel into Li layer is able to expand the Li layer spacing and reduce the Li/Ni antisite,leading to facilitated diffusion of lithium ions.Moreover,the formation of oxygen vacancy is able to promote anionic redox processes and suppress the gas release,thus leading to higher capacity.The results present valuable structural insights into the influence of lithium deficiency and provide guidance for the devel-opment of Li-rich cathode materials.展开更多
基金financially supported by the National Natural Science Foundation of China(52202046,51602246,and 51801144)the Natural Science Foundation of Shanxi Provincial(2021JQ-034)。
文摘Co-free Li-rich layered oxides(LLOs)are emerging as promising cathode materials for Li-ion batteries due to their low cost and high capacity.However,they commonly face severe structural instability and poor electrochemical activity,leading to diminished capacity and voltage performance.Herein,we introduce a Co-free LLO,Li_(1.167)Ni_(0.222)Mn_(0.611)O_(2)(Cf-L1),which features a cooperative structure of Li/Ni mixing and stacking faults.This structure regulates the crystal and electronic structures,resulting in a higher discharge capacity of 300.6 mA h g^(-1)and enhanced rate capability compared to the typical Co-free LLO,Li_(1.2)Ni_(0.2)Mn_(0.6)O_(2)(Cf-Ls).Density functional theory(DFT)indicates that Li/Ni mixing in LLOs leads to increased Li-O-Li configurations and higher anionic redox activities,while stacking faults further optimize the electronic interactions of transition metal(TM)3d and non-bonding O 2p orbitals.Moreover,stacking faults accommodate lattice strain,improving electrochemical reversibility during charge/discharge cycles,as demonstrated by the in situ XRD of Cf-L1 showing less lattice evolution than Cf-Ls.This study offers a structured approach to developing Co-free LLOs with enhanced capacity,voltage,rate capability,and cyclability,significantly impacting the advancement of the next-generation Li-ion batteries.
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Project supported by the National Key Research and Development Program of China(Grant No.2019YFE0100200)the National Natural Science Foundation of China(Grant No.U1964205)the Beijing Municipal Science and Technology Commission(Grant No.Z191100004719001)。
文摘The structural transformations,oxygen releasing and side reactions with electrolytes on the surface are considered as the main causes of the performance degradation of Li-rich layered oxides(LROs)cathodes in Li-ion batteries.Thus,stabilizing the surfaces of LROs is the key to realize their practical application in high energy density Li-ion batteries.Surface coating is regarded as one of the most effective strategies for high voltage cathodes.The ideal coating materials should prevent cathodes from electrolyte corrosion and possess both electronic and Li-ionic conductivities simultaneously.However,commonly reported coating materials are unable to balance these functions well.Herein,a new type of coating material,La_(2)CuO_(4)was introduced to mitigate the surface issues of LROs for the first time,due to its superb electronic conductivity(26-35 mS·cm^(-1))and lithium-ionic diffusion coefficient(10^(-12)-10^(-13)cm^(2)·s^(-1)).After coating with the La_(2)CuO_(4),the capacity retention of Li_(1.2)Ni_(0.54)Co_(0.13)Mn_(0.13)O_(2)cathode was increased to 85.9%(compared to 79.3%of uncoated cathode)after 150 cycles in the voltage range of 2.0-4.8 V.In addition,only negligible degradations on the deliverable capacity and rate capability were observed.
基金supported by the National Natural Science Foundation of China (51802261,52072298,and 52172228)the Natural Science Foundation of Shaanxi (2019GHJD-13 and 2020JC-41)+2 种基金the Natural Science Basic Research Plan in Shaanxi province of China (2019JLP-04)Xi'an Science and Technology Project of China (2019219714SYS012CG034)the foundation of National Key Laboratory (6142808200202),PR China.
文摘The high-rate cyclability of Li-rich Mn-based oxide(LMO)is highly limited by the electrochemical polarization resulting from the slow kinetic of the Li2MnO3 phase.Herein,the Prussian blue(PB)coating layer with specific redox potential is introduced as a functionalized interface to overcome the side effect and the escaping of O on the surface of LMO,especially its poor rate capability.In detail,the PB layer can restrict the large polarization of LMO by sharing overloaded current at a high rate due to the synchronous redox of PB and LMO.Consequently,an enhanced high rate performance with capacity retention of 87.8%over 300 cycles is obtained,which is superior to 50.5%of the pristine electrode.Such strategies on the high-rate cyclability of Li-rich Mn-based oxide compatible with good low-rate performances may attract great attention for pursuing durable performances.
基金supported by the National Key R&D Program of China (2016YFB0100301)the National Natural Science Foundation of China (51802020, 51802019)+1 种基金the Beijing Institute of Technology Research Fund Program for Young Scholarsthe Young Elite Scientists Sponsorship Program by CAST (2018QNRC001。
文摘Li-rich layered oxides have become one of the most concerned cathode materials for high-energy lithiumion batteries, but they still suffer from poor cycling stability and detrimental voltage decay, especially at elevated temperature. Herein, we proposed a surface heterophase coating engineering based on amorphous/crystalline Li3 PO4 to address these issues for Li-rich layered oxides via a facile wet chemical method. The heterophase coating layer combines the advantages of physical barrier effect achieved by amorphous Li3 PO4 with facilitated Li+diffusion stemmed from crystalline Li3 PO4. Consequently, the modified Li(1.2) Ni(0.2) Mn(0.6) O2 delivers higher initial coulombic efficiency of 92% with enhanced cycling stability at 55 °C(192.9 mAh/g after 100 cycles at 1 C). More importantly, the intrinsic voltage decay has been inhibited as well, i.e. the average potential drop per cycle decreases from 5.96 mV to 2.99 mV. This surface heterophase coating engineering provides an effective strategy to enhance the high-temperature electrochemical performances of Li-rich layered oxides and guides the direction of surface modification strategies for cathode materials in the future.
基金supported partially by the Natural Science Foundation of Beijing Municipality (L172036)the Joint Funds of the Equipment Pre-Research and Ministry of Education (6141A020225)+2 种基金the National Natural Science Foundation of China (Grants Nos. 52072323 and 51872098)the Science and Technology Beijing 100 Leading Talent Training Projectthe NCEPU ‘‘Double First-Class” Program. We thank Dr. Rui Liu for suggestions on the crystal structure analysis。
文摘Li-rich layered oxide cathodes have received considerable attention because of the high operating potential and specific capacity. However, the structural instability and parasitic reactions at high potential cause severe degradation of the electrochemical performance. In our studies, the cycling stability of Li_(1.14)Ni_(0.133)Co_(0.133)Mn_(0.544)O_(2) cathode is improved with LiPO_(2)F_(2) electrolyte additive. After 500 cycles, the capacity retention is increased from 53.6% to 85% at 3 C by LiPO_(2)F_(2) modification. This performance is mainly attributed to the enhanced interfacial stability of the Li-rich cathode. Based on systematic characterization, LiPO_(2)F_(2) additive was found to promote a stable interface film on the cathode surface during the cycling and mitigates the interfacial side reactions. This study provides new insights for improving high-potential Li-rich layered oxide batteries.
基金supported by the Nature Science Foundations of Hebei Province (B2016210071, B2016210111)the Natural Science Foundation of Hebei Education Department (QN2016057, ZD2015082, ZC2016045)+3 种基金the National College Students’ Innovative Entrepreneurial Training Project of Chinasupported by the Chinese National 973 Program (2015CB251106)the Joint Funds of the National Natural Science Foundation of China (U1564206)Major achievements Transformation Project for Central University in Beijing
文摘For constructing next-generation lithium-ion batteries with advanced performances,pursuit of highcapacity Li-rich cathodes has caused considerable attention.So far,the low discharge specific capacity and serious capacity fading are strangling the development of Fe-based Li-rich materials.To activate the extra-capacity of Fe-based Li-rich cathode materials,a facile molten salt method is exploited using an alkaline mixture of LiOH–LiNO3–Li2O2 in this work.The prepared Li1.09(Fe0.2Ni0.3Mn0.5)0.91O2 material yields high discharge specific capacity and good cycling stability.The discharge specific capacity shows an upward tendency at 0.1 C.After 60 cycles,a high reversible specific capacity of ~250 m Ah g-1is delivered.The redox of Fe3+/Fe4+and Mn3+/Mn4+are gradually activated during cycling.Notably,the redox reaction of Fe2+/Fe3+can be observed reversibly below 2 V,which is quite different from the material prepared by a traditional co-precipitation method.The stable morphology of fine nanoparticles(100–300 nm)is considered benefiting for the distinctive electrochemical performances of Li1.09(Fe0.2Ni0.3Mn0.5)0.91O2.This study demonstrates that molten salt method is an inexpensive and effective approach to activate the extra capacity of Fe-based Li-rich cathode material for high-performance lithium-ion batteries.
基金financial support from the National Natural Science Foundation of China(51904193)the Major Science and Technology Projects of Sichuan Province(2019ZDZX0029)the Fundamental Research Funds for the Central Universities。
文摘Li-rich layered oxide of Li_(1.2)Mn_(0.6)Ni_(0.2)O_(2)(LMNO)with a considerable specific capacity and higher voltage is regarded as a kind of promising cathode material.However,it suffers from transition metal ion dissolution and oxygen escape that leads to rapid capacity decay.In addition,the poor lithium-ion diffusion kinetics gives rise to unsatisfied rate performance.Herein,a stable layer of Li_(0.5)Mn_(0.5)O(LMO)out of LMNO is in-situ constructed through acetic passivation and following calcination process.The generated defect structure in the composite material exhibits fast ion diffusion kinetics and the produced LMO layer can stabilize the substructure,resulting in elevated cycling stability and rate performance.In specific,the LMNO@LMO material exhibits a high initial coulombic efficiency of 80.3%and remarkable capacity retention of 80.7%after 200 cycles at 1 C.Besides,the composite material reveals prominent rate performance that delivers discharge capacities of 158 and 131 m Ah g^(-1) at 5 and 10 C,respectively.At last,this study presents a new approach to optimizing the Li-rich cathode materials.
基金the National Natural Science Foundation of China(21673064 and 51902072)the Heilongjiang Touyan Team(HITTY-20190033)+2 种基金the Fundamental Research Funds for the Central Universities(HIT.NSRIF.2019040 and 2019041)the State Key Laboratory of Urban Water Resource and Environment(Harbin Institute of Technology)(2020 DX11)the Heilongjiang postdoctoral financial assistance(LBH-Z19055)。
文摘Traditional O3-type Li-rich layered materials are attractive with ultra-high specific capacities,but suffering from inherent problems of voltage hysteresis and poor cycle performance.As an alternative,O2-type materials show the potential to improve the oxygen redox reversibility and structural stability.However,their structure-performance relationship is still unclear.Here,we investigate the correlation between the Li component and dynamic chemical reversibility of O2-type Li-rich materials.By exploring the formation mechanism of a series of materials prepared by Na/Li exchange,we reveal that insufficient Li leads to an incomplete replacement,and the residual Na in the Li-layer would hinder the fast diffusion of Li^(+).Moreover,excessive Li induces the extraction of interlayer Li during the melting chemical reaction stage,resulting in a reduction in the valence of Mn,which leads to a severe Jahn-Teller effect.Structural detection confirms that the regulation of Li can improve the cycle stability of Li-rich materials and suppress the trend of voltage fading.The reversible phase evolution observed in in-situ X-ray diffraction confirms the excellent structural stability of the optimized material,which is conducive to capacity retention.This work highlights the significance of modulating dynamic electrochemical performance through the intrinsic structure.
基金funded by the project from the national natural science foundation of China(21805018 and 21878195)the applied basic research project of Sichuan science and technology department(2020YJ0134)the everest scientific research program of chengdu university of technology。
文摘Li-rich layered transition metal oxides are one of the most promising cathode materials for their high energy density.However,the cathodes usually suffer from severe potential dropping and capacity fading during cycling,which are associated with the surface oxygen release and accompanied by cation densification and structural collapse.Herein,an integrative approach of simultaneous constructing uniform 3d Fe-ion doping in the transition metal layer and Li-rich Li_(5)FeO_(4) shell to grab the oxygen and prevent interfacial side reactions is proposed.The introduction of Fe induces higher redox potential and stronger 3 d Fe-O_(2)p covalent bond,triggering reversible anionic redox via a reductive coupling mechanism.And the delithiated product of Li-rich Li_(5)FeO_(4) not only acts as a protective layer alleviating the side reactions but also enhances the surface kinetic property.With the benefit of promoted reversibility of oxygen redox and enhanced surface stability,the cathode exhibits high reversible capacity and superior cycle performance.Density function theory calculation indicates that the O_(2)p non-bonding state in the cathode incorporated with Fe sits at a lower energy band,resulting in higher energy storage voltage and improved oxygen stability.Consequently,the modified cathode exhibits a discharge specific capacity of 307 m A h g^(-1)(1 C=250 m A g^(-1)),coulombic efficiency of 82.09%in the initial cycle at 0.1 C and 88.34%capacity retention after 100 cycles at 1 C.The work illustrates a strategy that could simultaneously enhance oxygen redox reversibility and interface stability by constructing lattice bond coordination and delithiation induced protective layer to develop Li-rich materials with high reversible capacity and long lifespan.
基金the National Natural Science Foundation of China(51902072 and 22075062)the Heilongjiang Touyan Team(HITTY-20190033)+2 种基金the Heilongjiang Province“hundred million”project science and technology major special projects(2019ZX09A02)the State Key Laboratory of Urban Water Resource and Environment(Harbin Institute of Technology No.2020DX11)the Fundamental Research Funds for the Central Universities(FRFCU5710051922)。
文摘Co-free Li-rich layered oxide cathodes have drawn much attention owing to their low cost and high energy density.Nevertheless,anion oxidation of oxygen leads to oxygen peroxidation during the first charging process,which leads to co-migration of transition metal ions and oxygen vacancies,causing structural instability.In this work,we propose a pre-activation strategy driven by chemical impregnation to modulate the chemical state of surface lattice oxygen,thus regulating the structural and electrochemical properties of the cathodes.In-situ X-ray diffraction confirms that materials based on activated oxygen configuration have higher structural stability.More importantly,this novel efficient strategy endows the cathodes having a lower surface charge transfer barrier and higher Li+transfer kinetics characteristic and ameliorates its inherent issues.The optimized cathode exhibits excellent electrochemical performance:after 300 cycles,high capacity(from 238 m Ah g^(-1)to 193 m Ah g^(-1)at 1 C)and low voltage attenuation(168 mV)are obtained.Overall,this modulated surface lattice oxygen strategy improves the electrochemical activity and structural stability,providing an innovative idea to obtain high-capacity Co-free Li-rich cathodes for next-generation Li-ion batteries.
文摘The Li-rich Zn-doped LiNbO 3 (LN) crystals were grown by the Czochralski method. The structure of the crystals was measured by ultraviolet-visible absorption spectra. The results indicated that the Li-rich Zn-doped LN crystals had the same characteristics as the pure LN crystal. After Zn 2+ entered into the lattice of Li-rich Zn-doped LN crystal, it replaced Nb Li firstly. When there was no Nb Li , Zn 2+ replaced Li + then. The second harmonic generation (SHG) property of Li-rich Zn-doped LiNbO 3 crystal was measured. The results showed that the SHG conversation efficiency of Li-rich Zn-doped LiNbO 3 crystals was higher than that of Zn-doped LiNbO 3 crystals.
基金supported partially by State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources(Nos.LAPS_(2)1004,LAPS_(2)02114)National Natural Science Foundation of China(Nos.52272200,51972110,52102245 and 52072121)+6 种基金Beijing Science and Technology Project(No.Z211100004621010)Beijing Natural Science Foundation(Nos.2222076,2222077)Hebei Natural Science Foundation(No.E2022502022)Huaneng Group Headquarters Science and Technology Project(No.HNKJ20-H88)2022 Strategic Research Key Project of Science and Technology Commission of the Ministry of Education,China Postdoctoral Science Foundation(No.2022M721129)the Fundamental Research Funds for the Central Universities(Nos.2022MS030,2021MS028,2020MS023,2020MS028)the NCEPU"Double First-Class"Program and the State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources(No.LAPS22005).
文摘Boosting the interfacial stability between electrolyte and Li-rich cathode material at high operating voltage is vital important to enhance the cycling stability of Li-rich cathode materials for high-performance Li-ion batteries.In this work,vinyltrimethylsilane as a new type of organic silicon electrolyte additive is studied to address the interfacial instability of Li-rich cathode material at high operating voltage.The cells using vinyltrimethylsilane additive shows the high capacity retention of 73.9%after 300 cycles at 1 C,whereas the cells without this kind of additive only have the capacity retention of 58.9%.The improvement of stability is mainly attributed to the additive helping to form a more stable surface film for Li-rich cathode material,thus avoiding direct contact between the electrolyte and the cathode material,slowing down the dissolution of metal ions and the decomposition of the electrolyte under high operating voltage.Our findings in this work shed some light on the design of stable cycling performance of Li-rich cathode toward advanced Li-ion batteries.
基金supported by the National Natural Science Foundation of China (grant No.21908125)CNPC Innovation Found.
文摘The energy density of Li-ion batteries is closely related to the capacity and average voltage of cathode materials.Unfortunately,current cathode materials either have low capacity or voltage,which limits the development of high-energy-density Li-ion batteries.This has given challenge to many attempts to develop new cathode materials with high capacity and voltage.In this study,we find that Li easily inserts into the(111)plane of SiC in the presence of Si,and a well-organized Li-rich SiC twin crystal is formed.Ultraviolet-visible diffuse reflectance spectra and electrochemical test results suggest that this Li-rich SiC twin crystal possesses the band gap energy of 3.5 eV and charging capacity of 1979 mAh/g at the current density of 200 mA/g,making it a promising candidate for the cathode material in high-capacity Li-ion batteries.X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy results reveal that Si-induced Li insertion contributes to the changes in the surface species and structure of pristine SiC.These findings suggest that the Li-rich SiC twin crystal raises new possibilities for the development of high-capacity cathode materials and merits further investigation to expand its application scope.
基金the financial support from the Ministry of Science and Technology of China(MoST,No.52090034)the Higher Education Discipline Innovation Project(No.B12015).
文摘Co-free Li-rich Mn-based layered oxides are promising candidates for next-generation lithium-ion batteries(LIBs)due to their high specific capacity,high voltage,low cost.However,their commercialization is hindered by limited cycle life and poor rate performance.Herein,an in-situ simple and low-cost strategy with a nanoscale double-layer architecture of lithium polyphosphate(LiPP)and spinel phase covered on top of the bulk layered phase,is developed for Li_(1.2)Mn_(0.6)Ni_(0.2)O_(2)(LMNO)using Li^(+)-conductor LiPP(denoted as LMNO@S-LiPP).With such a double-layer covered architecture,the half-cell of LMNO@S-LiPP delivers an extremely high capacity of 202.5 mAh·g^(−1)at 1 A·g^(−1)and retains 85.3%of the initial capacity after 300 cycles,so far,the best highrate electrochemical performance of all the previously reported LMNOs.The energy density of the full-cell assembled with commercial graphite reaches 620.9 Wh·kg^(−1)(based on total weight of active materials in cathode and anode).Mechanism studies indicate that the superior electrochemical performance of LMNO@S-LiPP is originated from such a nanoscale double-layer covered architecture,which accelerates Li-ion diffusion,restrains oxygen release,inhibits interfacial side reactions,suppresses structural degradation during cycling.Moreover,this strategy is applicable for other high-energy-density cathodes,such as LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2),Li_(1.2)Ni_(0.13)Co_(0.13)Mn_(0.54)O_(2),LiCoO_(2).Hence,this work presents a simple,cost-effective,scalable strategy for the development of high-performance cathode materials.
基金supported by National Key R&D Program of China(2020YFA0406203)National Natural Science Foundation of China(Nos.52072008 and U2032167)+2 种基金Guangdong Basic and Applied Basic Research Foundation(No.2022B1515120070)Shenzhen Fundamental Research Program(No.GXWD20201231165807007-20200807125314001)the Large Scientific Facility Open Subject of Songshan Lake,Dongguan,Guangdong(No.KFKT2022A04).
文摘As one of the promising candidate cathode materials for the high-performance lithium-ion batteries,Li-rich layered oxides still suffer from a series of critical drawbacks,such as voltage decay,oxygen release,irrevers-ible migration of transition metal ions,etc.In this work,Li-deficient method has been confirmed as an effective approach to improve the overall electrochemical performances of Li-rich cathode.The optimized lithium-deficient Li-rich layered cathode exhibits splendid discharge capacity of~297 mAh/g at 0.1 C and prominent rate per-formance of-143 mAh/g at 5 C.Subsequently,neutron diffraction in combination with Raman spectroscopy is applied to explore and clarify the underlying mechanism for improved performances.It was found that the lithium-deficient induced nickel migration and oxygen vacancy play an significant role in improving electro-chemical performances,because migration of nickel into Li layer is able to expand the Li layer spacing and reduce the Li/Ni antisite,leading to facilitated diffusion of lithium ions.Moreover,the formation of oxygen vacancy is able to promote anionic redox processes and suppress the gas release,thus leading to higher capacity.The results present valuable structural insights into the influence of lithium deficiency and provide guidance for the devel-opment of Li-rich cathode materials.