Application prospects of high-voltage cathode materials in all-solid-state lithium-ion batteries

All-solid-state lithium-ion batteries are lithiumion batteries with solid-state electrolytes instead of liquid electrolytes.They are hopeful in solving the safety problems of lithium-ion batteries,once their large capacity and long life are achieved,they will have broad application prospects in the field of electric vehicles and large-scale energy storage.The working potential window of solid electrolytes is wider than that of liquid electrolytes,so high-voltage cathode materials could be used in all-solidstate lithium-ion batteries to get higher energy density and larger capacity by elevating the working voltage of the batteries.The spinel LiNi0.5Mn1.5O4material,layered Li–Ni–Co–Mn–O cathode materials and lithium-rich cathode materials can be expected to be applied to all-solid-state lithium-ion batteries as cathode materials due to their highvoltage platforms.In this review,the electrochemical properties and structures of spinel LiNi0.5Mn1.5O4material,layered Li–Ni–Co–Mn–O cathode materials and lithiumrich cathode materials are introduced.More attentions are paid on recent research progress of conductivity and interface stability of these materials,in order to improve their compatibility with solid electrolytes as cathode materials in all-solid-state lithium-ion batteries and fully improve the properties of all-solid-state batteries.Finally,the existing problems of their application in all-solid-state lithium-ion batteries are summarized,the main research directions are put forward and their application prospects in all-solid-state lithium-ion batteries are discussed.     

Investigation on the electrochemical activation process of Li1.20Ni 0.32Co0.004Mn0.476O2

The lithium-rich layered oxides are one of the most attractive cathode materials for lithium-ion batteries.Here,two types of Li1.20Ni0.32Co0.004Mn0.476O2 were synthesized using Li2CO3 and LiOH as lithium sources.An electrochemical activation process occurs in Li1.2Ni0.32Co0.004Mn0.476O2 prepared from Li2CO3(LLO-1),while no obvious activation in Li1.2Ni0.32Co0.004Mn0.476O2 prepared from LiOH(LLO-2) is observed.Via advanced scanning transmission electron microscopy(STEM),we found that Li2MnO3-like structure is rich in the surface region of LLO-2.The study provides a direct explanation for the electrochemical activation of lithium-rich materials.The sample with more LiMO2-like phase at the surface region shows a better cycling performance.It is likely that more LiMO2-like phase at the surface region could stabilize the interface and improve the cycling performance of the Li-rich cathode materials.     

Storage Characteristics of LiNi_(0.8)Co_(0.1 X)Mn_(0.1-X)O_2 (X=0,0.03,0.06) Cathode Materials for Lithium Batteries

1 Results LiNi0.8Co0.1 xMn0.1-xO2 cathodes with x=0,0.03 and 0.06 were prepared by firing a mixture of stoichiometric amounts of LiOH·H2O and coprecipitated Ni0.8Co0.1 xMn0.1-x(OH)2 at 800 ℃ for 15 h.Using these powders,their storage characteristics upon exposure to air and electrolytes at 90 ℃ were compared before charging and after charging to 4.3 V with a variation of the storage time.As the Co content (x) increased in the cathode,both the Ni2 content in the lithium 3a sites,and the contents of the LiOH and Li2CO3 impurity phases decreased.In particular,changes in the oxidation state of the Ni and Mn ions after 4.3 V charging upon storage at 90 ℃ were monitored using X-ray absorption near edge spectra (XANES),and Ni4 was found to reduce to Ni3 while the oxidation state of the predominant Mn4 did not change.However,residual Mn3 ions in the cathodes dissolved into the electrolytes.Moreover,the cathodes stored at 90 ℃ for 7 days were transformed into a spinel phase (Fd3m),regardless of the Co content.In an effort to resolve this dissolution problem,Al2O3 and Co3(PO4)2 nanoparticles were coated onto the cathode (LiNi0.8Co0.1Mn0.1O2) with the highest amounts of metal dissolution at 90 ℃.The results showed that the Co3(PO4)2-coated cathode exhibited greatly decreased metal dissolution and decreased its irreversible capacity by 5%,compared with a bare and Al2O3-coated cathodes.     

Preparation and performance of LiNi_(0.8)Co_(0.2)O_2 cathode material based on Co-substituted α–Ni(OH)_2 precursor

Co-substituted α-Ni(OH)2 was synthesized by a novel microwave homogeneous precipitation method in the presence of urea. LiNi0.8Co0.2O2 cathode material was synthesized by calcining Co-substituted α-Ni(OH)2 precursor and LiOH·H2O at 900℃ for 10 h in flowing oxygen. XRD, FTIR, FESEM and electro- chemical tests were used to study the physical and the electrochemical performances of the materials. The results show that the prepared LiNi0.8Co0.2O2 compound has a good layered hexagonal structure. Moreover, the LiNi0.8Co0.2O2 cathode material demonstrates stable cyclability with a high initial specific discharge capacity of 183.9 mAh/g. The good electrochemical performance could be attributed to the uniform distribution of Ni2 and Co2 ions in the crystal structure and a minimal cation mixing in LiNi0.8Co0.2O2 host structure.     

Ce-doped LiNi1/3Co（1/3-x/3）Mn1/3Cex/3O2 cathode materials for use in lithium ion batteries

LiNi1/3Co1/3Mn1/3O2 and Ce-doped LiNi1/3Co1/3Mn1/3O2 cathode materials were synthesized by a co-precipitation method and solid phase synthesis and characterized using X-ray diffraction(XRD) and scanning electron microscopy(SEM).The results indicated that the resultant cathode materials with different Ce content all had a good layer structure and high crystallinity.Electrochemical performance testing of the cathode materials showed that the discharge capacity increased with increasing Ce content while the initial reversible capacity attenuation decreased with Ce doping.When the Ce content of the cathode materials is x=0.2,and the current charge and discharge rate is a constant 0.2 C,the discharge capacity maintained 91% of its initial capacity after cycling 50 times.     

Development and application of phase diagrams for Li-ion batteries using CALPHAD approach

Phase diagrams provide fundamental knowledge about design map of new electrode materials for Li-ion batteries. The CALPHAD (CALculation of PHAse Diagrams) approach is widely applied to the development of phase diagrams and property diagrams in a thermodynamic language. Within the CALPHAD framework, the theoretical modeling can be performed to predict phase equilibria, thermodynamics, electrochemical and physical properties of electrodes. This review provides the successful application of high quality calculated phase diagrams and thermodynamic property diagrams in CALPHAD investigation to both cathodes and anodes of Li-ion batteries, including Li–Co–O, Li–Ni–O, Li–Co–Ni–O, Li–Mn–O, Li–Cu–O, Li–Si, Li–Sb and Li–Sn systems with. The intensive CALPHAD-type research may also predict electrochemical properties, cell performance of the Li-ion batteries to achieve more efficient development of electrode materials.     

Graphene-manganese oxide hybrid porous material and its application in carbon dioxide adsorption

Graphene-Mn3O4 (GMNO) hybrid porous material is prepared by a hydrothermal method and its performance in carbon dioxide adsorption is investigated.In the synthesis of the GMNO materials,MnO(OH)2 colloid obtained by the hydrolysis of Mn 2+ in basic solution was using as the precursor of the Mn3O4.After a hydrothermal reaction of the mixture of graphene oxide (GO) and MnO(OH)2,GO was reduced into graphene and the MnO(OH)2 was transformed into Mn3O4 with enhanced crystallization.X-ray diffraction,thermal gravimetric analysis,transmission electron microscopy,infrared spectra and Raman spectroscopy were taken to characterize the hybrid material.The porosity and the carbon dioxide adsorption ability are measured by gas sorption analysis,in which the as-prepared GMNO hybrid materials exhibit a specific surface area ranging from 140 to 680 m2g-1 and a maximum carbon dioxide capacity of about 11 wt%.     

Promotive effect of multi-walled carbon nanotubes on Co3O4 nanosheets and their application in lithium-ion battery

Co3O4/MWCNTs composites have been synthesized by a simple hydrothermal method using a surfactant(CTAB) and a precipitation agent(urea). The samples were characterized by XRD, SEM and BET methods. The electrochemical properties of the samples as anode materials for lithium batteries were studied by EIS and Galvanostatic measurements. The Co3O4/MWCNTs composites displayed higher capacity and better cycle performance in comparison with the Co3O4 nanosheets. The remarkable improvement of electrochemical performance within the hybrid composites is probably related to the addition of MWCNTs that possesses improved properties such as excellent electric conductivity and large surface area, which helps to alleviate the effect of volume change, shorten the distance of lithium ion diffusion, facilitate the transmission of electron and keep the structure stable.     

Low temperature synthesis of NiO/Co3O4 composite nanosheets as high performance Li-ion battery anode materials

NiO/Co3O4 composite nanosheets have been synthesized via a facile method at low temperature for the first time.The as prepared materials were characterized by X-ray powder diffraction(XRD) and transmission electron microscopy(TEM),and the performance of Li-ion batteries(LIBs) as anode materials were also studied.By controlling the atom ratio of Ni:Co,not only the size of the nanosheets can be controlled,the electrode’s conductivity and stability could also be greatly improved.The composite material showed a stable capacity retention during cycling(87% of the second capacity was retained after 15 cycles) even at a relatively large current rate(400 mA/g).The NiO/Co3O4 nanosheet might be promising candidate anode materials in high performance Li-ion batteries.     

Rational construction of NiCo_2O_4@Fe_2O_3 core-shell nanowire arrays for high-performance supercapacitors

Fe_2O_3 electrode materials exhibit excellent electrochemical performance in electrochemical energy storage system. However, its poor electrical conductivity limits its future practical application. The binder-free Ni Co_2O_4@Fe_2O_3 composites was reasonably designed and fabricated on carbon fiber paper with NiCo_2 O_4 nanowires as conductive scaffold in the present investigation. The three-dimensional nanostructure of the porous Fe_2O_3 nanorods coated the Ni Co2 O4 nanowire arrays showed the fascinating electrochemical performance, including high specific capacitance of 262 m F/cm2 at a current density of 1 m A/cm2, and remarkable cycle stability with～74.2% capacitance retention after 4000 cycles. The excellent pseudocapacitance performance of NiCo_2O_4@Fe_2O_3 composite materials is due to synergistic effect between NiCo_2O_4 and Fe_2O_3. The results of the present work show that NiCo_2O_4@Fe_2O_3 core-shell composite electrode is expected to exhibit excellent performance in the field of supercapacitors.     

Preparation and performance of LiNi0. 8Co0.2O2 cathode material based on Co-substituted α-Ni（OH）2 precursor

Co-substituted α-Ni（OH）2 was synthesized by a novel microwave homogeneous precipitation method in the presence of urea. LiNi0.8Co0.2O2 cathode material was synthesized by calcining Co-substituted α-Ni（OH）2 precursor and LiOH·H2O at 900℃for 10 h in flowing oxygen. XRD, FTIR, FESEM and electrochemical tests were used to study the physical and the electrochemical performances of the materials. The results show that the prepared LiNi0.8Co0.2O2 compound has a good layered hexagonal structure. Moreover, the LiNi0.8Co0.2O2cathode material demonstrates stable cyclability with a high initial specific discharge capacity of 183.9 mAh/g. The good electrochemical performance could be attributed to the uniform distribution of Ni^2＋ and Co^2＋ ions in the crystal structure and a minimal cation mixing in LiNi0.8Co0.2O2 host structure.     

Metal oxide and hydroxide nanoarrays: Hydrothermal synthes is and applications as superc apacitors and nanocatalysts

The development of nanotechnology in recent decades has brought new opportunities in the exploration of new materials for solving the issues of fossil fuel consumption and environment pollution.Materials with nano-array architecture are emerging as the key due to their structure advantages,which offer the possibility to fabricate high-performance electrochemical electrodes and catalysts for both energy storage and effcient use of energy.The main challenges in this feld remain as rational structure design and corresponding controllable synthesis.This article reviews recent progress in our laboratory related to the hydrothermal synthesis of metal oxide and hydroxide nanoarrays,whose structures are designed aiming to the application on supercapacitors and catalysts.The strategies for developing advanced materials of metal oxide and hydroxide nanoarrays,including NiO,Ni(OH)2,Co3O4,Co3O4@Ni–Co–O,cobalt carbonate hydroxide array,and mixed metal oxide arrays like Co3 xFex O4and Znx Co3 xO4,are discussed.The different kinds of structure designs such as 1D nanorod,2D nanowall and hierarchical arrays were involved to meet the needs of the high performance materials.Finally,the future trends and perspectives in the development of advanced nanoarrays materials are highlighted.     

Fabrication of SrFe_(12-x)Ni_xO_(19) nanoparticles and investigation on their structural,magnetic and dielectric properties

Sr Fe12-xNixO19 nanoparticles(x = 0–1) were synthesized by a combustion sol–gel method. Their structure, dielectric and magnetic properties were investigated by X-ray diffraction(XRD), scanning electron microscopy(SEM), an LCR metry, and vibrating sample magnetometry(VSM).The results reveal that all samples of Ni doped compounds(Sr Fe12-xNixO19) with x 0.2 are single phase. It appears that the Fe3+ ions are substituted by Ni2+ ions on the crystallographic sites of the Sr Fe12O19 structure; however, for x ≥ 0.2, the secondary Ni phase ferrite(Ni Fe2O3) appears, which reduces the saturation magnetization and coercivity. In addition, Ni doping reduces the dielectric constant, dielectric loss, and alternating current(ac) electrical conductivity of the samples. The variation in ac conductivity(σac) with frequency shows that the electrical conductivity in these ferrites is mainly attributed to the electron hopping mechanism.Therefore; all the single-phase Ni doped samples are suitable for use in magnetic recording media and microwave devices.     

Fabrication of SrFe12-xNixO19 nanoparticles and investigation on their structural,magnetic and dielectric properties

SrFe12?xNixO19 nanoparticles (x = 0–1) were synthesized by a combustion sol–gel method. Their structure, dielectric and magnetic properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), an LCR metry, and vibrating sample mag-netometry (VSM).The results reveal that all samples of Ni doped compounds (SrFe12?xNixO19) withx < 0.2 are single phase. It appears that the Fe3+ions are substituted by Ni2+ ions on the crystallographic sites of the SrFe12O19 structure; however, forx≥ 0.2, the secondary Ni phase ferrite (NiFe2O3) appears, which reduces the saturation magnetization and coercivity. In addition, Ni doping reduces the dielectric con-stant, dielectric loss, and alternating current (ac) electrical conductivity of the samples. The variation in ac conductivity (σac) with frequency shows that the electrical conductivity in these ferrites is mainly attributed to the electron hopping mechanism.Therefore; all the single-phase Ni doped samples are suitable for use in magnetic recording media and microwave devices.     

First principle calculation of lithiation/delithiation voltage in Li-ion battery materials

A first principle method, based on the density functional theory, was used to investigate the average voltage of lithiation/delithiation for Li-ion battery materials across 7 categories and 18 series, including LiMO 2 , LiMn 2 O 4 , LiMPO 4 , Li 2 MSiO 4 and graphite. The average voltage of lithiation/delithiation in the relevant electrode materials was obtained by comparing the total-energy difference, before and after an electrochemical reaction. The calculated values were in good agreement with experimental data. The systematic difference between the simulated and experimental values could be explained in terms of the binding energy on the surface of the lithium electrode. This type of calculation method could be applied as an easy and effective tool for predicting the potential performance of new lithiation/delithiation materials.     

Magnetism in Mn and Co doped ZnO bulk samples

Bulk samples with nominal composition Zn0.95Co0.05O and Zn0.92Co0.05Mn0.03O were fabricated by a solid-state reaction method at 600℃.X-ray diffraction experiment showed that the peaks of secondary phase Co3O4 with a cubic structure were visible in both samples,besides the main peaks of wurtzite structure as ZnO.Magnetization measurement indicated that doping Co alone can induce ferromag- netism in ZnO itself,while the introduction of Mn significantly enhances ferromagnetism.However, both samples showed different magnetic behavior at temperatures below 50 K.It was also noted that ferromagnetic coupling interaction was weakened due to the presence of antiferromagnetic Co3O4.     

Coupling effect of the conductivities of Li ions and electrons by introducing LLTO@C fibers in the LiNi0.8Co0.15Al0.05O2 cathode

To probe the coupling effect of the electron and Li ion conductivities in Ni-rich layered materials(LiNi0.8Co0.15Al0.05O2,NCA),lithium lanthanum titanate(LLTO)nanofiber and carbon-coated LLTO fiber(LLTO@C)materials were introduced to polyvinylidene difluoride in a cathode.The enhancement of the conductivity was indicated by the suppressed impedance and polarization.At 1 and 5 C,the cathodes with coupling conductive paths had a more stable cycling performance.The coupling mechanism was analyzed based on the chemical state and structure evolution of NCA after cycling for 200 cycles at 5 C.In the pristine cathode,the propagation of lattice damaged regions,which consist of high-density edge-dislocation walls,destroyed the bulk integrity of NCA.In addition,the formation of a rock-salt phase on the surface of NCA caused a capacity loss.In contrast,in the LLTO@C modified cathode,although the formation of dislocation-driven atomic lattice broken regions and cation mixing occurred,they were limited to a scale of several atoms,which retarded the generation of the rock-salt phase and resulted in a pre-eminent capacity retention.Only NiO phase“pitting”occurred.A mechanism based on the synergistic transport of Li ions and electrons was proposed.     

Microstructural evolution and growth kinetics of thermally grown oxides in plasma sprayed thermal barrier coatings

The formation of thermally grown oxide(TGO) during high temperature is a key factor to the degradation of thermal barrier coatings(TBCs)applied on hot section components. In the present study both the Co Ni Cr Al Y bond coat and Zr O_2-8 wt.% Y_2O_3(8YSZ) ceramic coat of TBCs were prepared by air plasma spraying(APS). The composition and microstructure of TGO in TBCs were investigated using scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS) and X-ray diffraction(XRD) analysis. The growth rate of TGO for TBC and pure BC were gained after isothermal oxidation at 1100 °C for various times. The results showed that as-sprayed bond coat consisted of β and γ/γ'phases,β phase reducesd as the oxidation time increased. The TGO comprised α-Al_2O_3 formed in the first 2 h. Co O, Ni O, Cr_2O_3 and spinel oxides appeared after 20 h of oxidation. Contents of Co O and Ni O reduced while that of Cr_2O_3 and spinel oxides increased in the later oxidation stage.The TGO eventually consisted of a sub-Al2O3 layer with columnar microstructure and the upper porous CS clusters. The TGO growth kinetics for two kinds of samples followed parabolic laws, with oxidation rate constant of 0.344 μm/h~(0.5) for TBCs and 0.354 μm/h0.5for pure BCs.     

基于尖晶石正极材料的柔性锂离子电池的制备和测试

发展了一种新颖、简单且普适性很强的制备柔性无支撑的电极薄膜方法,并成功地组装和测试了LiMn2O4/Li4Ti5O12,LiNi0.5Mn1.5O4/Li4Ti5O12以及LiNi0.5Mn1.5O4/石墨3种全电池.以这种方法制备的锂离子电池具有能量密度高的特点,在某些特定的领域具有潜在的应用前景.此外,这种技术还有可能应用于锂离子电池的原位光谱分析.     

高电压锂离子电池正极材料LiNi 0.5 Mn 1.5 O 4制备及改性

采用草酸铵共沉淀-高温固相烧结法合成了高电压尖晶石正极材料LiNi0.5Mn1.5O4及其掺杂改性材料LiNi0.4Mg0.1Mn1.5O4.采用X射线衍射(XRD)、扫描电子显微镜(SEM)、恒流充放电测试等对所合成样品进行表征.XRD测试表明所合成的样品具有尖晶石结构,空间群为Fd3m.电化学测试表明,样品有两个主放电平台,分别为4.7V和4.1V.经过800℃煅烧的样品LiNi0.5Mn1.5O4具有最好的倍率性能.经过900℃煅烧的样品具有最好的循环性能,以0.1C充放电,最高放电比容量达到124.2mAh.g-1,循环30次后容量保持率达92.7%.Mg掺杂的改性样品LiNi0.4Mg0.1Mn1.5O4在0.1C倍率下循环30次后容量保持率达95.7%,Mg的掺杂可以提高该材料的循环性能.