Stress-Regulation Design of Lithium Alloy Electrode toward Stable Battery Cycling

Metallic tin(Sn)foil is a promising candidate anode for lithium-ion batteries(LIBs)due to its metallurgical processability and high capacity.However,it suffers low initial Coulombic efficiency and inferior cycling stability due to its uneven alloying/dealloying reactions,large volume change and stress,and fast electrode structural degradation.Herein,we report an undulating LiSn electrode fabricated by a scalable two-step procedure involving mechanical lithography and chemical prelithiation of Sn foil.With the combination of experimental measurements and chemo-mechanical simulations,it was revealed the obtained undulating LiSn/Sn electrode could ensure better mechanical stability due to the pre-swelling state from Sn to Li x Sn and undulating structure of lithography in comparison with plane Sn,homogenize the electrochemical alloying/dealloying reactions due to the activated surface materials,and compensate Li loss during cycling due to the introduction of excess Li from Li_(x)Sn,thus enabling enhanced electrochemical performance.Symmetric cells consisting of undulating LiSn/Sn electrode with an active thickness of∼5 um displayed stable cycling over 1000 h at 1 mA cm^(-2) and 1 mAh cm^(-2) with a low average overpotential of<15 mV.When paired with commercial LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)(NCM622)cathode with high mass loading of 15.8 mg cm^(-2),the full cell demonstrated a high capacity of 2.4 mAh cm^(-2) and outstanding cycling stability with 84.9% capacity retention at 0.5 C after 100 cycles.This work presents an advanced LiSn electrode with stress-regulation design toward high-performance LIBs,and sheds light on the rational electrode design and processing of other high-capacity lithium alloy anodes.

Developing polydopamine modified molybdenum disulfide/epoxy resin powder coatings with enhanced anticorrosion performance and wear resistance on magnesium lithium alloys

Epoxy resin powder coating has been successfully applied on the corrosion protection of magnesium lithium alloys.However,poor wear resistance and microcracks formed during the solidification have limited it extensive application.There are limited approaches to exploit such anti-corrosion and mechanical properties of magnesium lithium alloys.Herein,the epoxy resin powder coating with polydopamine modified molybdenum disulfide(MoS_(2)@PDA-EP powder coating with 0,0.1,0.2,0.5,1.0 wt.%loading)was well prepared by melt extrusion to investigate its anticorrosion performance and wear resistance.The results revealed that the addition of MoS_(2)@PDA enhanced the adhesion strength between coatings and alloys,wear resistance and corrosion protection of the powder coatings.Among them,the optimum was obtained by 0.2 wt.%MoS_(2)@PDA-EP powder coating which could be attributed to well dispersion and efficient adhesion with coating matrix.To conclude,MoS_(2)@PDA-EP powder coating is meaningfully beneficial for the anticorrosive and wear performance improvement of magnesium lithium alloys.

GROWTH BEHAVIOR OF SHORT FATIGUE CRACKS FOR ALUMINUM- LITHIUM ALLOY 8090

The growth behaviors of short through cracks (0.2 < △a < 2.2mm) and long cracks are compared using CT type specimens in aluminum-lithium alloy 8090 T651. It is found that the short cracks grow much more than long ones and are observed to grow at the stress intensity ranges far below the long crack threshold. The distinction of growth bahavior between short and long cracks is attributed to the difference of their crack closure effect. The growth behavior of short cracks can be rationalized with that of long ones in terms of effective stress intensity ranges. The upper demarcation value of short through cracks for aluminum-lithium alloy 8090 is presented.

Investigation on Behavior of Rare Earth Element Cerium in Aluminum-Lithium Alloys by Internal Friction Method

The behavior of rare earth element Ce in 2090 Al Li alloys was studied by the method of low frequency internal friction.The results showed that rare earth element Ce can increase the activation energy of grain boundary and improve the grain boundary strength of alloys.Rare earth element Ce can decrease the tendency of softening of elastic modulus of 2090 Al Li alloys after heat cycle and keep high elastic modulus of initial state.

Fatigue crack propagation of new aluminum lithium alloy bonded with titanium alloy strap

A new type of aluminum lithium alloy （Al–Li alloy） Al–Li–S–4 was investigated by test in this paper. Alloy plate of 400 mm · 140 mm · 6 mm with single edge notch was made into samples bonded with Ti–6Al–4V alloy （Ti alloy） strap by FM 94 film adhesive after the surface was treated. Fatigue crack growth of samples was investigated under cyclic loading with stress ratio （R） of 0.1 and load amplitude constant. The results show that Al–Li alloy plate bonded with Ti alloy strap could retard fatigue crack propagation. Retardation effect is related with width and thickness of strap. Flaws have an observable effect on crack propagation direction.

Optimization on microstructure,mechanical properties and damping capacities of duplex structured Mg–8Li–4Zn–1Mn alloys

Optimizing the mechanical properties and damping capacity of the duplex-structured Mg–Li–Zn–Mn alloy by tailoring the microstructure via hot extrusion was investigated.The results show that the Mg–8Li–4Zn–1Mn alloy is mainly composed ofα-Mg,β-Li,Mg–Li–Zn and Mn phases.The microstructure of the test alloy is refined owing to dynamic recrystallization(DRX)during hot extrusion.After hot extrusion,the crushed precipitates are uniformly distributed in the test alloy.The yield strength(YS),ultimate tensile strength(UTS),and elongation(EL)of as-extruded alloy reach 156 MPa,208 MPa,and 32.3%,respectively,which are much better than that of as-cast alloy.Furthermore,the as-extruded and as-cast alloys both exhibit superior damping capacities,with the damping capacity(Q^(-1))of 0.030 and 0.033 at the strain amplitude of 2×10^(-3),respectively.The mechanical properties of the test alloy can be significantly improved by hot extrusion,whereas the damping capacities have no noticeable change,which indicates that the duplex-structured Mg–Li alloys with appropriate mechanical properties and damping properties can be obtained by alloying and hot extrusion.

Influence of deformation on the corrosion behavior of LZ91 Mg-Li alloy

The effect of rolling and forging on the microstructure and corrosion behavior of LZ91 alloy was investigated using an electron probe micro-analyzer,immersion and electrochemical tests.Results showed that the area fraction of theβ-Li phase remained unchanged,and the grain size of theβ-Li phase decreased after forging.The as-rolled forged alloy(FR-LZ91)exhibited the highest area fraction of theβ-Li phase and the longest grains.The corrosion resistance of the forged LZ91 alloy increased due to grain refinement that prevented further corrosion during the immersion test.Among the experimental alloys,FR-LZ91 showed the highest resistance of corrosion film and charge transfer resistance values due to its protective film caused by the high area fraction of theβ-Li phase.

Influence of thermomechanical treatments on localized corrosion susceptibility and propagation mechanism of AA2099 Al-Li alloy

In order to manifest the influence of specific microstructural component on the development of severe localized corrosion in an AA2099 aluminum-lithium alloy, the corrosion behavior of the alloy subjected to solution heat treatment, cold working and artificial ageing was investigated. Immersion testing and potentiodynamic polarization were employed to introduce localized corrosion; scanning electron microscopy and transmission electron microscopy were used to characterize the alloy microstructure and corrosion morphology. It was found that the susceptibility of the alloy to severe localized corrosion was sensitive to thermomechanical treatments. Additionally, the state of alloying elements influenced the mechanism of localized corrosion propagation. Specifically, the alloy in T8 conditions showed higher susceptibility to severe localized corrosion than that in other conditions. During potentiodynamic polarization, the alloy in solution heat-treated and T3 conditions displayed crystallographic corrosion morphology while the alloy in T6 and T8 conditions exhibited selective attack of grain interiors and grain boundaries in local regions.

Electrochemical performance of a nickel-rich LiNi0.6Co0.2Mn0.2O2 cathode material for lithium-ion batteries under different cut-off voltages

A spherical-like Ni0.6Co0.2Mn0.2(OH)2precursor was tuned homogeneously to synthesize LiNi0.6Co0.2Mn0.2O2as a cathode material for lithium-ion batteries. The effects of calcination temperature on the crystal structure, morphology, and the electrochemical performance of the as-prepared LiNi0.6Co0.2Mn0.2O2were investigated in detail. The as-prepared material was characterized by X-ray diffraction, scanning electron microscopy, laser particle size analysis, charge–discharge tests, and cyclic voltammetry measurements. The results show that the spherical-like LiNi0.6Co0.2Mn0.2O2material obtained by calcination at 900°C displayed the most significant layered structure among samples calcined at various temperatures, with a particle size of approximately 10 μm. It delivered an initial discharge capacity of 189.2 mAh•g−1at 0.2C with a capacity retention of 94.0% after 100 cycles between 2.7 and 4.3 V. The as-prepared cathode material also exhibited good rate performance, with a discharge capacity of 119.6 mAh•g−1at 5C. Furthermore, within the cut-off voltage ranges from 2.7 to 4.3, 4.4, and 4.5 V, the initial discharge capacities of the calcined samples were 170.7, 180.9, and 192.8 mAh•g−1, respectively, at a rate of 1C. The corresponding retentions were 86.8%, 80.3%, and 74.4% after 200 cycles, respectively. © 2017, University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg.

A Nonlinear Observer Approach of SOC Estimation Based on Hysteresis Model for Lithium-ion Battery

In this paper, a state of charge U+0028 SOC U+0029 estimation approach for lithium-ion battery based on equivalent circuit model and the input-to-state stability U+0028 ISS U+0029 theory has been proposed. According to the electrochemical performance of lithiumion battery, the equivalent circuit model with two RC networks is established, which includes hysteresis characteristic in inner electrochemical response process. The nonlinear relation between open circuit voltage U+0028 OCV U+0029 and SOC is obtained from a rapid test. Exponential fitting method is used to identify the parameters of the model. A novel state observer based on ISS theory is designed for lithium-ion battery SOC estimation. The designed observer is tested on AMESim and Simulink co-simulation. The simulation results show that the proposed method has a high SOC estimation accuracy with an error of about 2 percent. © 2017 Chinese Association of Automation.

Influence of Ca on microstructure and corrosion resistance of Mg-14Li alloy

In order to improve the corrosion resistance of magnesium lithium alloy, Mg-14 Li alloy with different content of Ca(0, 3, 5, 10 wt.%) was prepared with a induction melting furnace. Electrochemical test and corrosion test were carried out in NaCl solution with different Cl^-concentrations. The results indicate that the microstructure of the Mg-14 Li alloy with Ca consists of dendritic β phase and eutectic structure(β+CaMg_2). With the increase of Ca addition from 0, to 3, 5, 10 wt.%, the corrosion resistance of the Mg-14 Li alloy initially increases first and then decreases, and that of alloy with 3% Ca is the best. Therefore, the corrosion resistance of Mg-14 Li alloy in NaCl solution can be effectively improved by adding proper amount of Ca. In addition, the concentration of Cl^-was one of important factors affecting the corrosion resistance of the Mg-14 Li alloy, and the influence of Ca was slighter than that of Cl^-.

Texture evolution of Al-Mg-Li aeronautical alloys in in-situ tension

Texture evolution in extruded and hot-rolled Al-Mg-Li aeronautical alloys during in-situ tension was investigated by using elec-tron backscattered diffraction （EBSD）. A field emission scanning electron microscope （FE-SEM） and a MICROTEST-5000 tensile stage were used to carry out in-situ tension tests and observations. The crystallographic texture of the extruded sample changed from weak cube texture {001}〈100〉 to texture {018}〈081〉 during tension fracture. However, strong Brass {110}〈112〉 in the hot-rolled sample was modi-fied into a mixture texture component of Brass {110}〈112〉 and S {123}〈634〉 during tension fracture. Texture evolution in the two samples during tension can be explained by the rotation of grain orientation.

Fractional Modeling and SOC Estimation of Lithium-ion Battery

This paper proposes a state of charge (SOC) estimator of Lithium-ion battery based on a fractional order impedance spectra model. Firstly, a battery fractional order impedance model is derived on the grounds of the characteristics of Warburg element and constant phase element (CPE) over a wide range of frequency domain. Secondly, a frequency fitting method and parameter identification algorithm based on output error are presented to identify parameters of the fractional order model of Lithium-ion battery. Finally, the fractional order Kalman filter approach is introduced to estimate the SOC of the lithium-ion battery based on the fractional order model. The simulation results show that the fractional-order model can ensure an acceptable accuracy of the SOC estimation, and the error of estimation reaches maximally up to 0.5% SOC. © 2014 Chinese Association of Automation.

Corrosion behavior of as-cast Mg–8Li–3Al+xCe alloy in 3.5wt% NaCl solution

Mg-8Li-3Al＋xCe alloys（x = 0.5wt%, 1.0wt%, and 1.5wt%） were prepared through a casting route in an electric resistance furnace under a controlled atmosphere. The cast alloys were characterized by X-ray diffraction, optical microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The corrosion behavior of the as-cast Mg-8Li-3Al＋xCe alloys were studied under salt spray tests in 3.5wt% NaC l solution at 35°C, in accordance with standard ASTM B-117, in conjunction with potentiodynamic polarization（PDP） tests. The results show that the addition of Ce to Mg-8Li-3Al（LA83） alloy results in the formation of Al_2Ce intermetallic phase, refines both the α-Mg phase and the Mg_（17）Al_（12） intermetallic phase, and then increases the microhardness of the alloys. The results of PDP and salt spray tests reveal that an increase in Ce content to 1.5wt% decreases the corrosion rate. The best corrosion resistance is observed for the LA83 alloy sample with 1.0wt% Ce.

Difference in formation of plasma electrolytic oxidation coatings on MgLi alloy in comparison with pure Mg

In order to study the substrate lattice structure(Li addition)on the growth of plasma electrolytic oxidation(PEO)coatings,Mg Li alloy(11.36 wt.%of Li,cubic)and pure Mg(hexagonal)were treated under a pulsed direct PEO mode in a phosphate electrolyte for different periods of time.The results revealed that the presence of Li and Li-rich phases in the cubic Mg alloy seems to be essential for the treatment result rather than the original lattice structure.A modified discharge behavior of Mg Li alloy finally led to a different microstructure of the coating.The unstable coatings of Mg Li alloy tended to dissolve rapidly though shared the similar composition to that of pure Mg.Li was incorporated only in the primary conversion products at the interface of coating/Mg Li.In spite of the advanced efficiency of energy input during processing,the more porous and thinner PEO coatings on the Mg Li alloy were less resistant to abrasion and corrosion.

Microstructure and Properties of RS-P/M and I/M Al-Li Alloys

The Al-Li alloy powder was prepared by argon atomization. It was canned in an aluminum container and then the compact powder billet and I/M Al-Li ingot were extruded into φ17mm at 450°C with an area reduction of 34:1. Compared the tensile properties between RS-P/M and I/M Al-Li alloys, also studied their process, microstructure and the mechanism of the ageing strengthening in the alloy. The size of atomized powder is in the range of 10-140μm and the cooling rate of the powder is about 103-105K/s. The RS-P/M Al-Li alloy has finer grains and more dispersed precipitates than the I/M Al-Li alloy.

ODF Determination from One Complete Pole Figure

A suitable model is developed through the revision of the maximum entropy method (MEM) for the orientation distribution function (ODF) determination from one complete pole figure in the case of cubic materials. Its relevant software is demonstrated by a group of coefficients of the ODF and an experimental test of an Al-Li alloy. The results confirm that the model proposed in this study is accurate and reliable

Contribution of T_1 Precipitates to Strength in Two Kinds

The behavior of interaction between dislocation and T 1 plate was observed and analyzed by means of TEM technique in Al Li alloys of 2090 and 2090+Ce. The observation results show that the interaction between dislocation and T 1 plate is a mix type of shearing and Orowan looping, and the physical models are established by theory of precipitates strengthening. The results of calculation illustrate that the contribution of T 1 plate is up 30%～60% to the overall critical resolved shear stress (CRSS). The role of T 1 plate is enhanced with aging time in the material aged 3～48 h at 190℃, but this enhancing effect becomes gentle on overaged condition. The strengthening effects of T 1 plate in 2090 and 2090+Ce alloys are little different on under aged condition, but the strengthening effects of T 1 precipitates in alloy 2090+Ce is little bigger than that of 2090 on overaged condition, especially the cutting mechanism is only considered. The difference between strengthening effects of matrix in two alloys is about 3.2 MPa on underaged condition and 8.7 MPa or so on overaged condition.

FePO4-coated Li[Li0.2Ni0.13Co0.13Mn0.54]O2 with improved cycling performance as cathode material for Li-ion batteries

Li[Li0.2Ni0.13Coo.13Mn0.54]O2 cathode materials were synthesized by carbonate-based co-precipitation method, and then, its surface was coated by thin layers of FePO4. The prepared samples were characterized by X-ray diffraction （XRD）, field emission scanning electron micro- scope （FESEM）, energy-dispersive spectroscopy （EDS）, and transmission electron microscopy （TEM）. The XRD and TEM results suggest that both the pristine and the coated materials have a hexagonal layered structure, and the FePO4 coating layer does not make any major change in the crystal structure. The FePO4-coated sample exhibits both improved initial discharge capacity and columbic efficiency compared to the pristine one. More significantly, the FePO4 coating layer has a much positive influence on the cycling perfor- mance. The FePO4-coated sample exhibits capacity reten- tion of 82 % after 100 cycles at 0.5℃ between 2.0 and 4.8 V, while only 28 % for the pristine one at the same charge-discharge condition. The electrochemical impe- dance spectroscopy （EIS） results indicate that this improved cycling performance could be ascribed to the presence of FePO4 on the surface of Li[Li0.2Ni0.13Co0.13Mno.54102 par- ticle, which helps to protect the cathode from chemical attacks by HF and thus suppresses the large increase in charge transfer resistance.

Growth and characterization of high-quality Mn-doped LiAlO_2 single crystal

The growth of a Mn-doped LiAlO_2 single crystal by the Czochralski（CZ） method and the characterization of its spectroscopy and thermoluminescence（TL） are presented.The X-ray rocking curve and chemical etching analysis show that the as-grown crystal has good crystallinity.The full-width at half-maximum （FWHM） of the LiAlO_2（200）ωrocking curve is 23.2 arcsec and the etching pits density of the（100） plane is（1.6-4.0）×10~4 cm^（-2）.The transmission spectrum indicates that the crystal is highly transparent in the 200-1500-nm wavelength range.The emission spectrum of the crystal consists of a peak around 579 nm when excited with 428-nm light.The TL spectra show that the LiAlO_2：Mn crystal has glow peaks at 150 and 172℃.The change of TL characteristics of the crystal before and after thermal annealing in the air is discussed,and the effect of annealing and irradiation on the evolution of defect types is analyzed.