Spinel LiMn204 was synthesized by a solid-state method. A 204468-size battery was fabricated and stored at 55℃. The structure and morphology of the LiMn204 cathode were analyzed by X-ray diffraction （XRD） and scann...Spinel LiMn204 was synthesized by a solid-state method. A 204468-size battery was fabricated and stored at 55℃. The structure and morphology of the LiMn204 cathode were analyzed by X-ray diffraction （XRD） and scanning electron microscopy （SEM） technique. Energy dispersive spectroscopy （EDS） was used to analyze the surface component of the carbon anode. The discharge capacities of LiMn204 stored for 0, 24, 48, and 96 h are 106, 98, 96, and 92 mAh·g^-1, respectively. The cyclic performance is improved after storage. The capacity retentions of LiMn204 stored for 0, 24, 48, and 96 h are 83.8%, 85.8%, 86.9%, and 88.6% after 180 cycles. The intensity of all the LiMn204 diffraction peaks is weakened. Mn is detected from the carbon electrode when the battery is stored for 96 h. Cyclic voltammograms and electrochemical impedance spectroscopy （EIS） were used to examine the surface state of the electrode after storage. The results show that the resistance and polarization of LiMn2O4/electrolyte is increased after storage, which is responsible for the fading of capacity.展开更多
The mechanism for capacity fading of18650lithium ion full cells under room-temperature(RT)is discussedsystematically.The capacity loss of18650cells is about12.91%after500cycles.The cells after cycles are analyzed by X...The mechanism for capacity fading of18650lithium ion full cells under room-temperature(RT)is discussedsystematically.The capacity loss of18650cells is about12.91%after500cycles.The cells after cycles are analyzed by XRD,SEM,EIS and CV.Impedance measurement shows an overall increase in the cell resistance upon cycling.Moreover,it also presents anincreased charge-transfer resistance(Rct)for the cell cycled at RT.CV test shows that the reversibility of lithium ioninsertion/extraction reaction is reduced.The capacity fading for the cells cycled can be explained by taking into account the repeatedfilm formation over the surface of anode and the side reactions.The products of side reactions deposited on separator are able toreduce the porosity of separator.As a result,the migration resistance of lithium ion between the cathode and anode would beincreased,leading the fading of capacity and potential.展开更多
A normal spinel LiMn_2O_4 as cathode material for lithium-ion cells wascycled galvanostatically (0.2 C) at 55 deg C. To determine the contribution of each voltage plateauto the total capacity fading of the cathode upo...A normal spinel LiMn_2O_4 as cathode material for lithium-ion cells wascycled galvanostatically (0.2 C) at 55 deg C. To determine the contribution of each voltage plateauto the total capacity fading of the cathode upon repeated cycling, the capacities in each plateauwere separated by differentiation of voltage vs. capacity. The results how that the capacity fadingin the upper voltage plateau is more rapidly than that in the lower during discharging, while incharging process, it fades slower than that in the lower voltage range. The increased capacity shiftand aggravated self-discharge/electrolyte oxidation during discharging contribute to a high fadingrate in the upper step. Capacity shift also takes place during charging process, which againenhancing the fading rate of the lower voltage plateau. An increase in capacity shift, as a resultof an increase in polarization of the cell, plays a major role in determining the fading rate ineach voltage plateau, further reflecting the thickening of the passivation layer on the activeparticles, and the accumulation of electrolyte decomposition. The relative capacity loss formodified spinels is well correlated with the relative increase in the polarization of thehalf-cells, confirming the above causes for capacity fade of this kind of cathode material.展开更多
The capacity fade of spinel lithium manganese oxide in lithium-ion batteries is a bottleneck challenge for the large-scale application.The traditional opinion is that Mn（Ⅱ） ions in the anode are reduced to the meta...The capacity fade of spinel lithium manganese oxide in lithium-ion batteries is a bottleneck challenge for the large-scale application.The traditional opinion is that Mn（Ⅱ） ions in the anode are reduced to the metallic manganese that helps for catalyzing electrolyte decomposition.This could poison and damage the solid electrolyte interface（SEI） film,leading to the the capacity fade in Li-ion batteries.We propose a new mechanism that Mn（Ⅱ） deposites at the anode hinders and/or blocks the intercalation/de-intercalation of lithium ions,which leads to the capacity fade in Li-ion batteries.Based on the new mechanism assumption,a kind of new structure with core-shell characteristic is designed to inhabit manganese ion dissolution,thus improving electrochemical cycle performance of the cell.By the way,this mechanism hypothesis is also supported by the results of these experiments.The LiMn2-xTixO4 shell layer enhances cathode resistance to corrosion attack and effectively suppresses dissolution of Mn,then improves battery cycle performance with LiMn_2O_4 cathode,even at high rate and elevated temperature.展开更多
The solid electrolyte interphase(SEI)is widely recognized as a critical factor leading to the capacity fading of lithium-ion batteries(LIBs).Although SEI stress-related mechanical failure caused by the expansion or co...The solid electrolyte interphase(SEI)is widely recognized as a critical factor leading to the capacity fading of lithium-ion batteries(LIBs).Although SEI stress-related mechanical failure caused by the expansion or contraction of active materials upon cycles is well documented,previously reported SEI components and overpotential varying phenomena due to SEI stress and their effects on the electrochemical performance are poorly understood.Here,we establish a quantitative correlation between capacity fading and the SEI stress by considering its effects on side reactions,especially SEI component evolution,in a multiscale mechanical-electrochemical coupling model.Furthermore,the capacity fading behaviors of two typical cells(Li[NiMnCo]O_(2) as the cathode,and graphite and silicon as the anode,respectively)were adopted as numerical examples to demonstrate its potential utility and applications.Stress within the SEI was indeed found to play a predominant role in the capacity fading of the graphite and silicon anodes,resulting in 27%and 69%of the total capacity loss after 200 and 100 cycles at 1 C,respectively.This study provides valuable mechanical insights into the variations of SEI properties related to the capacity degradation and SEI optimization and design for LIBs.展开更多
P2-type sodium layered oxide cathode (Na_(2/3)Ni_(1/3)Mn_(2/3)O_(2)P2-NNMO) has attracted great attention as a promising cathode material for sodium ion batteries because of its high specific capacity. However, this m...P2-type sodium layered oxide cathode (Na_(2/3)Ni_(1/3)Mn_(2/3)O_(2)P2-NNMO) has attracted great attention as a promising cathode material for sodium ion batteries because of its high specific capacity. However, this material suffers from a rapid capacity fade during high-voltage cycling. Several mechanisms have been proposed to explain the capacity fade, including intragranular fracture caused by the P2-O2 phase transion, surface structural change, and irreversible lattice oxygen release. Here we systematically investigated the morphological, structural, and chemical changes of P2-NNMO during high-voltage cycling using a variety of characterization techniques. It was found that the lattice distortion and crystal-plane buckling induced by the P2-O2 phase transition slowed down the Na-ion transport in the bulk and hindered the extraction of the Na ions. The sluggish kinetics was the main reason in reducing the accessible capacity while other interfacial degradation mechanisms played minor roles. Our results not only enabled a more complete understanding of the capacity-fading mechanism of P2-NNMO but also revealed the underlying correlations between lattice doping and the moderately improved cycle performance.展开更多
1 Results Li1+xV3O8,has been extensively investigated as a positive electrode material for lithium metal polymer batteries and a great deal of interest has been focused on the structural characterization and cyclabili...1 Results Li1+xV3O8,has been extensively investigated as a positive electrode material for lithium metal polymer batteries and a great deal of interest has been focused on the structural characterization and cyclability of this compound[1-6].From the present work,Li1.1V3O8 nanograins synthesized at low temperature from original two component gel precursor suffer from strong capacity fading on cycling.The latter is characterized by emergence of polarized redox processes at the expense of initial ones.Fro...展开更多
The utilization of Li-rich layered oxides(LLOs)as cathodes in high-energy Li-ion batteries is significantly hindered by serious voltage decay and capacity fading due to irreversible oxygen release and transition metal...The utilization of Li-rich layered oxides(LLOs)as cathodes in high-energy Li-ion batteries is significantly hindered by serious voltage decay and capacity fading due to irreversible oxygen release and transition metal(TM)migration triggered by the lattice strain.Herein,B ions are effectively incorporated into the tetrahedral vacancies situated between TM slab and Li layer of LLOs.The robust B-O bond,along with the low Bader charge of oxygen within BO_(4) tetrahedra,alleviates excessive oxidation of O anions while substantially reinforcing the oxygen framework.Consequently,the B-doped LLO sample exhibits only slight variation in lattice parameters,especially the c-axis,which can be characterized as exhibiting“zero-strain”as supported by in situ XRD data.As a result,the discharge capacity of the B-LLO sample maintains 210.66 mAh·g^(−1) after 300 cycles,with a retention ratio of 90.7%.展开更多
Lithium sulfur battery （LSB） offers several advantages such as very high energy density, low-cost, and environmental-friendliness. However, it suffers from serious degradation of its reversible capacity because of t...Lithium sulfur battery （LSB） offers several advantages such as very high energy density, low-cost, and environmental-friendliness. However, it suffers from serious degradation of its reversible capacity because of the dissolution of reaction intermediates, lithium polysulfides, into the electrolyte. To solve this limitation, there are many studies using graphene-based materials due to their excellent mechanical strength and high conductivity. Compared with graphene, graphene oxide （GO） contains various oxygen functional groups, which enhance the reaction with lithium polysulfides. Here, we investigated the positive effect of using GO mixed with carbon black on the performance of cathode in LSB. We have observed a smaller drop of capacity in GO mixed sulfur cathode. We further demonstrate that the mechanistic origin of reversibility improvement, as confirmed through CV and Raman spectra, can be explained by the stabilization of sulfur in lithium polysulfide intermediates by oxygen functional groups of GO to prevent dissolution. Our findings suggest that the use of graphene oxide-based cathode is a promising route to significantly improve the reversibility of current LSB.展开更多
With the deployment of small cells and device to device communications in future heterogeneous networks,in many situations we would encounter mobile radio channels with partly blocked line of sight component,which are...With the deployment of small cells and device to device communications in future heterogeneous networks,in many situations we would encounter mobile radio channels with partly blocked line of sight component,which are well modeled by the Rician shadowed(RS) fading channel.In this paper,by the usage of Kummer transformation,a simplified representation of the RS fading channel with integral fading parameter is given.It is a finite series representation involving only exponential function and low order polynomials.This allows engineers not only the closed-form expressions for exact performance analysis over RS fading channel,but also the insights on the system design tactics.展开更多
Lithium rich layered oxides(LLOs)are attractive cathode materials for Li-ion batteries owing to their high capacity(>250 mA h g^(-1))and suitable voltage(∼3.6 V).However,they suffer from serious voltage and capaci...Lithium rich layered oxides(LLOs)are attractive cathode materials for Li-ion batteries owing to their high capacity(>250 mA h g^(-1))and suitable voltage(∼3.6 V).However,they suffer from serious voltage and capacity fading,which is focused in this review.First,an overview of crystal structure,band structure and electrochemical performances of LLOs is provided.After that,current understanding on oxygen loss,capacity fading and voltage fading is summarized.Finally,five strategies to mitigate capacity and voltage fading are reviewed.It is believed that these understandings can help solve the fading problems of LLOs.展开更多
Sc^3＋-doped lithium manganese oxides were synthesized by solid-state reaction. The influences of doping element on structure, mean valence of manganese, and electrochemical performances were studied by X-ray diffract...Sc^3＋-doped lithium manganese oxides were synthesized by solid-state reaction. The influences of doping element on structure, mean valence of manganese, and electrochemical performances were studied by X-ray diffraction （XRD）, galvanostatic charge-discharge and cyclic voltammetric tests, and also electrochemical impedance spectroscopy （EIS）. XRD tests showed that doped lithium manganese oxides were pure spinel structure without other phases. Redox titration and visible spectrophotometry tests indicated that the mean valence of manganese in doped lithium manganese oxides was higher than that of pure one. LiSc0.02Mn1.9804 remained 92.9% of the initial specific discharge capacity after 50th cycle at a constant current of 50 m/g, and the reversibility of LiSc0.02Mn1.98O4 was improved in comparison with pure LiMn2O4 at 50 ℃. EIS indicated that film deposition on spinel particles was suppressed because of Sc^3＋ doping, and the charge transfer between the surface film and spinel particles with increasing temperature for Sc^3＋-doped materials became easier as compared with undoped one.展开更多
Fast charging, which aims to shorten recharge times to 10–15 min, is crucial for electric vehicles(EVs),but battery capacity usually decays rapidly if batteries are charged under such severe conditions.Revealing the ...Fast charging, which aims to shorten recharge times to 10–15 min, is crucial for electric vehicles(EVs),but battery capacity usually decays rapidly if batteries are charged under such severe conditions.Revealing the failure mechanism is a prerequisite to improving the charging performance of lithium(Li)-ion batteries. Previous studies have focused less on cathode materials while also mostly focusing on their early changes. Thus, the cumulative effect of long-term fast charging on cathode materials has not been fully studied. Here, we study the changes in a layered cathode material during 1000 cycles of 6 C charging based on 1.6 Ah LiCoO_(2)/graphite pouch cells. Postmortem analysis reveals that the surface structure, charge transfer resistance and Li-ion diffusion coefficient of the cathode degenerate during repeated fast charging, causing a large increase in polarization. This polarization-induced poor utilization of the Li inventory is an important reason for the rapid capacity fading of batteries. These findings deepen the understanding of the aging mechanism for cells undergoing fast charging and can be used as benchmarks for the future development of high-capacity, fast-charging layered cathode materials.展开更多
A high sulfur content sulfur–carbon composite was synthesized via in situ generation method in aqueous solution.When the sulfur loading is up to 90%,the electrode still exhibits good cycling performance with a revers...A high sulfur content sulfur–carbon composite was synthesized via in situ generation method in aqueous solution.When the sulfur loading is up to 90%,the electrode still exhibits good cycling performance with a reversible capacity of about 623 mAh·g^(-1)after 100 cycles.To further commercialize the Li–S battery,understanding the capacity degradation mechanism is very essential,especially with a high sulfur loading electrode.To achieve this goal,the electrochemical performance of the high sulfur loading electrode was studied,and the structure change of the electrode after cycling was also examined by ex situ scanning electron microscopy(SEM)and other techniques.The result shows that the Li_(2)S_(2)and Li_(2)S inhomogeneous precipitation contributes to the majority capacity fading of the high sulfur loading Li–S cells.展开更多
Spinel LiMn204 was synthesized by glycine-nitrate method and coated with CaCO3 in order to enhance the electrochemical performance at room temperature （25℃） and 55℃. The uncoated and CaCO3-coated LiMn204 materials...Spinel LiMn204 was synthesized by glycine-nitrate method and coated with CaCO3 in order to enhance the electrochemical performance at room temperature （25℃） and 55℃. The uncoated and CaCO3-coated LiMn204 materials were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and electrochemical tests. XRD and SEM results indicated that CaCO3 particles encapsulated the surface of the LiMn204 without causing any structural change. The charge-discharge tests showed that the specific discharge capacity fade of pristine electrode at 25 and 55℃ were 25.5% and 52%, respectively. However, surface modified cathode shows 7.4% and 29.5% loss compared to initial specific discharge capacity at 70th cycle for 25 and 55~C, respectively. The improvement of electrochemical performance is attributed to suppression of Mn2＋ dissolution into electrolyte via CaCO3 layer.展开更多
In application,lithium-ion cells undergo expansion during cycling.The mechanical behavior and the impact of external stress on lithium-ion battery are important in vehicle application.In this work,18 Ah high power com...In application,lithium-ion cells undergo expansion during cycling.The mechanical behavior and the impact of external stress on lithium-ion battery are important in vehicle application.In this work,18 Ah high power commercial cell with Li Ni_(0.5)Co_(0.2)Mn_(0.3)O_(2)/graphite electrode were adopted.A commercial compress machine was applied to monitor the mechanical characteristics under different stage of charge(SOC),lifetime and initial external force.The dynamic and steady force was obtained and the results show that the dynamic force increases as the SOC increasing,obviously.During the lifetime with high power driving mode,different external force is shown to have a great impact on the long-term cell performance,with higher stresses result in higher capacity decay rates and faster impedance increases.A proper initial external force(900 N)provides lower impedance increasing.Postmortem analysis of the cells with2000 N initial force suggests a close correlation between electrochemistry and mechanics in which higher initial force leads to higher direct current internal resistance(DCIR)increase rate.In addition,for the cell with higher external force,deformation of the cathode and thicker solid electrolyte interface(SEI)film on the surface of anode and separator are observed.Porosity reduction and closure was also verified after cycles which is an obstacle to the lithium ion transferring.The largest cause of the observed capacity decline was the loss of active lithium through autopsy analysis.In addition,for the cell with higher external force,deformation of the cathode and thicker SEI film on the surface of anode and separator are observed.Porosity reduction and closure was also verified after cycles which is an obstacle to the lithium ion transferring.The largest cause of the observed capacity decline was the loss of active lithium through autopsy analysis.展开更多
3d-transition metal(Fe,Co,Ni,and Mn)-based MXene materials have been predicted to demonstrate exceptional electrochemical performance because of their good electrical conductivity and the presence of metallic atoms wi...3d-transition metal(Fe,Co,Ni,and Mn)-based MXene materials have been predicted to demonstrate exceptional electrochemical performance because of their good electrical conductivity and the presence of metallic atoms with multiple charge states.However,until now,there have been no reports on MXenes based on Fe,Co,Ni,and Mn,due to the lack of 3d-metal-layered precursors.Herein,we successfully synthesized the first 3d-transition metal-based MXenes,Mn_(2)CT_(x) by exfoliating a layered precursor derived from the anti-perovskite bulk Mn3GaC.The as-prepared Mn_(2)CT_(x) MXene nanosheets were employed as anode materials in lithium-ion batteries,which exhibited stable storage capacity of 764.7 mAh·g^(-1) at 0.5 C,placing its storage capacities at an upper-middle level compared with other reported MXene materials as well as other Mn-based anode materials.Overall,this study opens a new avenue for MXene research by synthesizing 3d-transition metal-based MXenes for electrochemical applications.展开更多
Modeling and state of charge(SOC)estimation of Lithium cells are crucial techniques of the lithium battery management system.The modeling is extremely complicated as the operating status of lithium battery is affected...Modeling and state of charge(SOC)estimation of Lithium cells are crucial techniques of the lithium battery management system.The modeling is extremely complicated as the operating status of lithium battery is affected by temperature,current,cycle number,discharge depth and other factors.This paper studies the modeling of lithium iron phosphate battery based on the Thevenin’s equivalent circuit and a method to identify the open circuit voltage,resistance and capacitance in the model is proposed.To improve the accuracy of the lithium battery model,a capacity estimation algorithm considering the capacity loss during the battery’s life cycle.In addition,this paper solves the SOC estimation issue of the lithium battery caused by the uncertain noise using the extended Kalman filtering(EKF)algorithm.A simulation model of actual lithium batteries is designed in Matlab/Simulink and the simulation results verify the accuracy of the model under different operating modes.展开更多
The performance and lifespan of Li-ion batteries used in electric vehicles are influenced by operating and environmental conditions.An understanding of the mechanisms leading to performance degradation and capacity fa...The performance and lifespan of Li-ion batteries used in electric vehicles are influenced by operating and environmental conditions.An understanding of the mechanisms leading to performance degradation and capacity fading can aid in the design of better battery systems.In the present study,numerical models are developed to estimate the capacity fading,battery performance,and residual life.Furthermore,key associated parameters are identified as state of charge,charging protocols,and temperature.Later on,a deep machine learning(DML)model consisting of one input,four hidden,and one output layer is developed to estimate the residual life of a battery system.The five input parameters considered include voltage,current,temperature,number of cycles,and time,apart from residual life as the output parameter.The proposed DML model consists of five dense layers and three dropout layers with 2889 trainable parameters in total,with higher neuron counts in initial layers to process diverse inputs and fewer neurons in later layers to ensure compact feature representation as well as to make better and faster predictions.Results from the numerical and DML models are compared to the reported experimental results,where good agreement is observed.Thus,the developed model is tested on Lithium based Nickel Manganese Cobalt Oxide and Nickel Cobalt Aluminum Oxide batteries,for which parametric studies are performed to investigate the influence of the operating temperature,rate of charge/discharge,and pulse charging on the battery life.Therefore,the technologies proposed in this study can contribute to the development of intelligent battery management systems,enabling enhanced performance,and hence prolonged life of battery systems.展开更多
Layered Ni-rich oxide cathodes in lithium-ion batteries(LIBs)often struggle with poor thermal safety and capacity fade.Xin and colleagues’studies in Nature and Nature Energy demonstrate a novel high-entropy(compositi...Layered Ni-rich oxide cathodes in lithium-ion batteries(LIBs)often struggle with poor thermal safety and capacity fade.Xin and colleagues’studies in Nature and Nature Energy demonstrate a novel high-entropy(compositionally complex)doping strategy,introducing“cocktail effects”from multiple constituents.This approach substantially improves cycling performance and stability,reduces material cost,and may pave the way toward the development of advanced electrodes for next-generation LIBs.展开更多
基金supported by the National Basic Research Program of China (No. 2007CB613607)
文摘Spinel LiMn204 was synthesized by a solid-state method. A 204468-size battery was fabricated and stored at 55℃. The structure and morphology of the LiMn204 cathode were analyzed by X-ray diffraction （XRD） and scanning electron microscopy （SEM） technique. Energy dispersive spectroscopy （EDS） was used to analyze the surface component of the carbon anode. The discharge capacities of LiMn204 stored for 0, 24, 48, and 96 h are 106, 98, 96, and 92 mAh·g^-1, respectively. The cyclic performance is improved after storage. The capacity retentions of LiMn204 stored for 0, 24, 48, and 96 h are 83.8%, 85.8%, 86.9%, and 88.6% after 180 cycles. The intensity of all the LiMn204 diffraction peaks is weakened. Mn is detected from the carbon electrode when the battery is stored for 96 h. Cyclic voltammograms and electrochemical impedance spectroscopy （EIS） were used to examine the surface state of the electrode after storage. The results show that the resistance and polarization of LiMn2O4/electrolyte is increased after storage, which is responsible for the fading of capacity.
基金Project(51574287)supported by the National Natural Science Foundation of ChinaProject(2015CX001)supported by the Innovation-driven Plan in Central South University,China
文摘The mechanism for capacity fading of18650lithium ion full cells under room-temperature(RT)is discussedsystematically.The capacity loss of18650cells is about12.91%after500cycles.The cells after cycles are analyzed by XRD,SEM,EIS and CV.Impedance measurement shows an overall increase in the cell resistance upon cycling.Moreover,it also presents anincreased charge-transfer resistance(Rct)for the cell cycled at RT.CV test shows that the reversibility of lithium ioninsertion/extraction reaction is reduced.The capacity fading for the cells cycled can be explained by taking into account the repeatedfilm formation over the surface of anode and the side reactions.The products of side reactions deposited on separator are able toreduce the porosity of separator.As a result,the migration resistance of lithium ion between the cathode and anode would beincreased,leading the fading of capacity and potential.
文摘A normal spinel LiMn_2O_4 as cathode material for lithium-ion cells wascycled galvanostatically (0.2 C) at 55 deg C. To determine the contribution of each voltage plateauto the total capacity fading of the cathode upon repeated cycling, the capacities in each plateauwere separated by differentiation of voltage vs. capacity. The results how that the capacity fadingin the upper voltage plateau is more rapidly than that in the lower during discharging, while incharging process, it fades slower than that in the lower voltage range. The increased capacity shiftand aggravated self-discharge/electrolyte oxidation during discharging contribute to a high fadingrate in the upper step. Capacity shift also takes place during charging process, which againenhancing the fading rate of the lower voltage plateau. An increase in capacity shift, as a resultof an increase in polarization of the cell, plays a major role in determining the fading rate ineach voltage plateau, further reflecting the thickening of the passivation layer on the activeparticles, and the accumulation of electrolyte decomposition. The relative capacity loss formodified spinels is well correlated with the relative increase in the polarization of thehalf-cells, confirming the above causes for capacity fade of this kind of cathode material.
基金Funded by the National Natural Science Foundation of China(Nos.21561016,21661015)Jiangxi Provincial Science&Technology Program(Nos.20133BBE50010,20142BDH80020,and 20161BBE50052)Science&Technology Program of Jiangxi Provincial Education Bureau(No.GJJ150775)
文摘The capacity fade of spinel lithium manganese oxide in lithium-ion batteries is a bottleneck challenge for the large-scale application.The traditional opinion is that Mn（Ⅱ） ions in the anode are reduced to the metallic manganese that helps for catalyzing electrolyte decomposition.This could poison and damage the solid electrolyte interface（SEI） film,leading to the the capacity fade in Li-ion batteries.We propose a new mechanism that Mn（Ⅱ） deposites at the anode hinders and/or blocks the intercalation/de-intercalation of lithium ions,which leads to the capacity fade in Li-ion batteries.Based on the new mechanism assumption,a kind of new structure with core-shell characteristic is designed to inhabit manganese ion dissolution,thus improving electrochemical cycle performance of the cell.By the way,this mechanism hypothesis is also supported by the results of these experiments.The LiMn2-xTixO4 shell layer enhances cathode resistance to corrosion attack and effectively suppresses dissolution of Mn,then improves battery cycle performance with LiMn_2O_4 cathode,even at high rate and elevated temperature.
基金supported by the Natural Science Foundation of Shanghai(Grant No.23ZR1421800)the National Natural Science Foundation of China(Grant Nos.12272213 and 11872235).
文摘The solid electrolyte interphase(SEI)is widely recognized as a critical factor leading to the capacity fading of lithium-ion batteries(LIBs).Although SEI stress-related mechanical failure caused by the expansion or contraction of active materials upon cycles is well documented,previously reported SEI components and overpotential varying phenomena due to SEI stress and their effects on the electrochemical performance are poorly understood.Here,we establish a quantitative correlation between capacity fading and the SEI stress by considering its effects on side reactions,especially SEI component evolution,in a multiscale mechanical-electrochemical coupling model.Furthermore,the capacity fading behaviors of two typical cells(Li[NiMnCo]O_(2) as the cathode,and graphite and silicon as the anode,respectively)were adopted as numerical examples to demonstrate its potential utility and applications.Stress within the SEI was indeed found to play a predominant role in the capacity fading of the graphite and silicon anodes,resulting in 27%and 69%of the total capacity loss after 200 and 100 cycles at 1 C,respectively.This study provides valuable mechanical insights into the variations of SEI properties related to the capacity degradation and SEI optimization and design for LIBs.
基金financial support from the National Natural Science Foundation of China (21938005, 21573147, 22005190, 22008154, 21872163)the Science & Technology Commission of Shanghai Municipality, the Natural Science Foundation of Shanghai (19DZ1205500, 19ZR1424600, 19ZR1475100)the Sichuan Science and Technology Program (2021JDRC0015 to L.S.L)。
文摘P2-type sodium layered oxide cathode (Na_(2/3)Ni_(1/3)Mn_(2/3)O_(2)P2-NNMO) has attracted great attention as a promising cathode material for sodium ion batteries because of its high specific capacity. However, this material suffers from a rapid capacity fade during high-voltage cycling. Several mechanisms have been proposed to explain the capacity fade, including intragranular fracture caused by the P2-O2 phase transion, surface structural change, and irreversible lattice oxygen release. Here we systematically investigated the morphological, structural, and chemical changes of P2-NNMO during high-voltage cycling using a variety of characterization techniques. It was found that the lattice distortion and crystal-plane buckling induced by the P2-O2 phase transition slowed down the Na-ion transport in the bulk and hindered the extraction of the Na ions. The sluggish kinetics was the main reason in reducing the accessible capacity while other interfacial degradation mechanisms played minor roles. Our results not only enabled a more complete understanding of the capacity-fading mechanism of P2-NNMO but also revealed the underlying correlations between lattice doping and the moderately improved cycle performance.
文摘1 Results Li1+xV3O8,has been extensively investigated as a positive electrode material for lithium metal polymer batteries and a great deal of interest has been focused on the structural characterization and cyclability of this compound[1-6].From the present work,Li1.1V3O8 nanograins synthesized at low temperature from original two component gel precursor suffer from strong capacity fading on cycling.The latter is characterized by emergence of polarized redox processes at the expense of initial ones.Fro...
基金supported by the Applied Basic Research Fund of Guangdong Province(No.2024B1515020071)the National Natural Science Foundation of China(Nos.52371217 and 52150410411)+1 种基金the Science and Technology Innovation Plan Project of Hunan Province(No.2024RC3217)Guangdong Provincial Science and Technology Plan Project(No.2023A0505020009).
文摘The utilization of Li-rich layered oxides(LLOs)as cathodes in high-energy Li-ion batteries is significantly hindered by serious voltage decay and capacity fading due to irreversible oxygen release and transition metal(TM)migration triggered by the lattice strain.Herein,B ions are effectively incorporated into the tetrahedral vacancies situated between TM slab and Li layer of LLOs.The robust B-O bond,along with the low Bader charge of oxygen within BO_(4) tetrahedra,alleviates excessive oxidation of O anions while substantially reinforcing the oxygen framework.Consequently,the B-doped LLO sample exhibits only slight variation in lattice parameters,especially the c-axis,which can be characterized as exhibiting“zero-strain”as supported by in situ XRD data.As a result,the discharge capacity of the B-LLO sample maintains 210.66 mAh·g^(−1) after 300 cycles,with a retention ratio of 90.7%.
基金supported by the Core Technology Development Program for Next-Generation Energy Storage of the Research Institute for Solar and Sustainable Energies (RISE) at GISTthe DOST UPD ERDT Faculty Development Program
文摘Lithium sulfur battery （LSB） offers several advantages such as very high energy density, low-cost, and environmental-friendliness. However, it suffers from serious degradation of its reversible capacity because of the dissolution of reaction intermediates, lithium polysulfides, into the electrolyte. To solve this limitation, there are many studies using graphene-based materials due to their excellent mechanical strength and high conductivity. Compared with graphene, graphene oxide （GO） contains various oxygen functional groups, which enhance the reaction with lithium polysulfides. Here, we investigated the positive effect of using GO mixed with carbon black on the performance of cathode in LSB. We have observed a smaller drop of capacity in GO mixed sulfur cathode. We further demonstrate that the mechanistic origin of reversibility improvement, as confirmed through CV and Raman spectra, can be explained by the stabilization of sulfur in lithium polysulfide intermediates by oxygen functional groups of GO to prevent dissolution. Our findings suggest that the use of graphene oxide-based cathode is a promising route to significantly improve the reversibility of current LSB.
基金sponsored by the National Natural Science Foundation of China under grant No.61171089the Training Program of the Major Research Plan of the National Natural Science Foundation of China under grant No.91438104
文摘With the deployment of small cells and device to device communications in future heterogeneous networks,in many situations we would encounter mobile radio channels with partly blocked line of sight component,which are well modeled by the Rician shadowed(RS) fading channel.In this paper,by the usage of Kummer transformation,a simplified representation of the RS fading channel with integral fading parameter is given.It is a finite series representation involving only exponential function and low order polynomials.This allows engineers not only the closed-form expressions for exact performance analysis over RS fading channel,but also the insights on the system design tactics.
基金supported by China-Japanese Research Cooperative Program founded by the Ministry of Science and Technology of the People’s Republic of China(2017YFE0127600)the National Natural Science Foundation of China(No.21978153,51774191).
文摘Lithium rich layered oxides(LLOs)are attractive cathode materials for Li-ion batteries owing to their high capacity(>250 mA h g^(-1))and suitable voltage(∼3.6 V).However,they suffer from serious voltage and capacity fading,which is focused in this review.First,an overview of crystal structure,band structure and electrochemical performances of LLOs is provided.After that,current understanding on oxygen loss,capacity fading and voltage fading is summarized.Finally,five strategies to mitigate capacity and voltage fading are reviewed.It is believed that these understandings can help solve the fading problems of LLOs.
文摘Sc^3＋-doped lithium manganese oxides were synthesized by solid-state reaction. The influences of doping element on structure, mean valence of manganese, and electrochemical performances were studied by X-ray diffraction （XRD）, galvanostatic charge-discharge and cyclic voltammetric tests, and also electrochemical impedance spectroscopy （EIS）. XRD tests showed that doped lithium manganese oxides were pure spinel structure without other phases. Redox titration and visible spectrophotometry tests indicated that the mean valence of manganese in doped lithium manganese oxides was higher than that of pure one. LiSc0.02Mn1.9804 remained 92.9% of the initial specific discharge capacity after 50th cycle at a constant current of 50 m/g, and the reversibility of LiSc0.02Mn1.98O4 was improved in comparison with pure LiMn2O4 at 50 ℃. EIS indicated that film deposition on spinel particles was suppressed because of Sc^3＋ doping, and the charge transfer between the surface film and spinel particles with increasing temperature for Sc^3＋-doped materials became easier as compared with undoped one.
基金supported by the National Natural Science Foundation of China(51874151,51964017)。
文摘Fast charging, which aims to shorten recharge times to 10–15 min, is crucial for electric vehicles(EVs),but battery capacity usually decays rapidly if batteries are charged under such severe conditions.Revealing the failure mechanism is a prerequisite to improving the charging performance of lithium(Li)-ion batteries. Previous studies have focused less on cathode materials while also mostly focusing on their early changes. Thus, the cumulative effect of long-term fast charging on cathode materials has not been fully studied. Here, we study the changes in a layered cathode material during 1000 cycles of 6 C charging based on 1.6 Ah LiCoO_(2)/graphite pouch cells. Postmortem analysis reveals that the surface structure, charge transfer resistance and Li-ion diffusion coefficient of the cathode degenerate during repeated fast charging, causing a large increase in polarization. This polarization-induced poor utilization of the Li inventory is an important reason for the rapid capacity fading of batteries. These findings deepen the understanding of the aging mechanism for cells undergoing fast charging and can be used as benchmarks for the future development of high-capacity, fast-charging layered cathode materials.
基金financially supported by the Beijing Municipal Science and Technology Project (No.Z171100000917021)。
文摘A high sulfur content sulfur–carbon composite was synthesized via in situ generation method in aqueous solution.When the sulfur loading is up to 90%,the electrode still exhibits good cycling performance with a reversible capacity of about 623 mAh·g^(-1)after 100 cycles.To further commercialize the Li–S battery,understanding the capacity degradation mechanism is very essential,especially with a high sulfur loading electrode.To achieve this goal,the electrochemical performance of the high sulfur loading electrode was studied,and the structure change of the electrode after cycling was also examined by ex situ scanning electron microscopy(SEM)and other techniques.The result shows that the Li_(2)S_(2)and Li_(2)S inhomogeneous precipitation contributes to the majority capacity fading of the high sulfur loading Li–S cells.
基金supported by the Erciyes University Research Found under the code of FBA-08-439
文摘Spinel LiMn204 was synthesized by glycine-nitrate method and coated with CaCO3 in order to enhance the electrochemical performance at room temperature （25℃） and 55℃. The uncoated and CaCO3-coated LiMn204 materials were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and electrochemical tests. XRD and SEM results indicated that CaCO3 particles encapsulated the surface of the LiMn204 without causing any structural change. The charge-discharge tests showed that the specific discharge capacity fade of pristine electrode at 25 and 55℃ were 25.5% and 52%, respectively. However, surface modified cathode shows 7.4% and 29.5% loss compared to initial specific discharge capacity at 70th cycle for 25 and 55~C, respectively. The improvement of electrochemical performance is attributed to suppression of Mn2＋ dissolution into electrolyte via CaCO3 layer.
基金financially supported by the National Key Research&Development Program of China(2016YFB0100400)the National Natural Science Foundation of China(21875154 and 22179090)。
文摘In application,lithium-ion cells undergo expansion during cycling.The mechanical behavior and the impact of external stress on lithium-ion battery are important in vehicle application.In this work,18 Ah high power commercial cell with Li Ni_(0.5)Co_(0.2)Mn_(0.3)O_(2)/graphite electrode were adopted.A commercial compress machine was applied to monitor the mechanical characteristics under different stage of charge(SOC),lifetime and initial external force.The dynamic and steady force was obtained and the results show that the dynamic force increases as the SOC increasing,obviously.During the lifetime with high power driving mode,different external force is shown to have a great impact on the long-term cell performance,with higher stresses result in higher capacity decay rates and faster impedance increases.A proper initial external force(900 N)provides lower impedance increasing.Postmortem analysis of the cells with2000 N initial force suggests a close correlation between electrochemistry and mechanics in which higher initial force leads to higher direct current internal resistance(DCIR)increase rate.In addition,for the cell with higher external force,deformation of the cathode and thicker solid electrolyte interface(SEI)film on the surface of anode and separator are observed.Porosity reduction and closure was also verified after cycles which is an obstacle to the lithium ion transferring.The largest cause of the observed capacity decline was the loss of active lithium through autopsy analysis.In addition,for the cell with higher external force,deformation of the cathode and thicker SEI film on the surface of anode and separator are observed.Porosity reduction and closure was also verified after cycles which is an obstacle to the lithium ion transferring.The largest cause of the observed capacity decline was the loss of active lithium through autopsy analysis.
基金supported by the funding from the National Natural Science Foundation of China(Nos.52003163,22105129)Guangdong Basic and Applied Basic Research Foundation(Nos.2022A1515010670,2022A1515011048)+2 种基金Science and Technology Innovation Commission of Shenzhen(No.20200812112006001)and Shenzhen University-Taipei University of Science and Technology Collaboration Project(Nos.2022005,2022015).X.Cai appreciates the help from the electron microscopy center at Shenzhen University for providing the aberration-corrected HAADF STEM testing services.H.Sun acknowledges the support from the Guangdong Special Support Program(No.2021TQ06C953)the Science and Technology Planning Projects of Shenzhen Municipality(Nos.JCYJ20190806142614541,GXWD20220811164433002).
文摘3d-transition metal(Fe,Co,Ni,and Mn)-based MXene materials have been predicted to demonstrate exceptional electrochemical performance because of their good electrical conductivity and the presence of metallic atoms with multiple charge states.However,until now,there have been no reports on MXenes based on Fe,Co,Ni,and Mn,due to the lack of 3d-metal-layered precursors.Herein,we successfully synthesized the first 3d-transition metal-based MXenes,Mn_(2)CT_(x) by exfoliating a layered precursor derived from the anti-perovskite bulk Mn3GaC.The as-prepared Mn_(2)CT_(x) MXene nanosheets were employed as anode materials in lithium-ion batteries,which exhibited stable storage capacity of 764.7 mAh·g^(-1) at 0.5 C,placing its storage capacities at an upper-middle level compared with other reported MXene materials as well as other Mn-based anode materials.Overall,this study opens a new avenue for MXene research by synthesizing 3d-transition metal-based MXenes for electrochemical applications.
基金This work is supported in part by Open Fund of State Key Laboratory of Operation and Control of Renewable Energy&Storage Systems(DGB51201700424)Industrial Innovation of Jilin Province Development and Reform Commission(2017C017-2)Jilin Provincial“13th Five-Year Plan”Science and Technology Project([2016]88).
文摘Modeling and state of charge(SOC)estimation of Lithium cells are crucial techniques of the lithium battery management system.The modeling is extremely complicated as the operating status of lithium battery is affected by temperature,current,cycle number,discharge depth and other factors.This paper studies the modeling of lithium iron phosphate battery based on the Thevenin’s equivalent circuit and a method to identify the open circuit voltage,resistance and capacitance in the model is proposed.To improve the accuracy of the lithium battery model,a capacity estimation algorithm considering the capacity loss during the battery’s life cycle.In addition,this paper solves the SOC estimation issue of the lithium battery caused by the uncertain noise using the extended Kalman filtering(EKF)algorithm.A simulation model of actual lithium batteries is designed in Matlab/Simulink and the simulation results verify the accuracy of the model under different operating modes.
基金P.R.Budarapu is thankful to the Indian Institute of Technology Bhubaneswar,India,for funding this study through grant number SP097.
文摘The performance and lifespan of Li-ion batteries used in electric vehicles are influenced by operating and environmental conditions.An understanding of the mechanisms leading to performance degradation and capacity fading can aid in the design of better battery systems.In the present study,numerical models are developed to estimate the capacity fading,battery performance,and residual life.Furthermore,key associated parameters are identified as state of charge,charging protocols,and temperature.Later on,a deep machine learning(DML)model consisting of one input,four hidden,and one output layer is developed to estimate the residual life of a battery system.The five input parameters considered include voltage,current,temperature,number of cycles,and time,apart from residual life as the output parameter.The proposed DML model consists of five dense layers and three dropout layers with 2889 trainable parameters in total,with higher neuron counts in initial layers to process diverse inputs and fewer neurons in later layers to ensure compact feature representation as well as to make better and faster predictions.Results from the numerical and DML models are compared to the reported experimental results,where good agreement is observed.Thus,the developed model is tested on Lithium based Nickel Manganese Cobalt Oxide and Nickel Cobalt Aluminum Oxide batteries,for which parametric studies are performed to investigate the influence of the operating temperature,rate of charge/discharge,and pulse charging on the battery life.Therefore,the technologies proposed in this study can contribute to the development of intelligent battery management systems,enabling enhanced performance,and hence prolonged life of battery systems.
基金supported by the project on Natural Science Foundation of China(Key Project of 52131306)Carbon Emission Peak and Neutrality of Jiangsu Province(no.BE2022031-4)+1 种基金by research start-up funds from Southeast University(RF1028624081)Nanjing Normal University(184080H201B41).
文摘Layered Ni-rich oxide cathodes in lithium-ion batteries(LIBs)often struggle with poor thermal safety and capacity fade.Xin and colleagues’studies in Nature and Nature Energy demonstrate a novel high-entropy(compositionally complex)doping strategy,introducing“cocktail effects”from multiple constituents.This approach substantially improves cycling performance and stability,reduces material cost,and may pave the way toward the development of advanced electrodes for next-generation LIBs.
